Although excellence in pre‐ and postoperative care can often make the difference between an uneventful and a complicated recovery, the care provided in the operating room (OR) usually has the most significant impact on patient outcome. Performing a technically proficient, complete, and expeditious operation is only one component of this phase. Refinements in anesthetic techniques and monitoring, cardiopulmonary bypass (CPB), and myocardial protection have enabled surgeons to operate successfully on extremely ill patients with far advanced cardiac disease and multiple comorbidities. Use of off‐pump modalities to avoid CPB is particularly useful in patients at high risk because of associated comorbidities. Minimally invasive surgery and percutaneous approaches to address valve pathology may lessen the trauma of a procedure and expedite recovery. This chapter describes intraoperative monitoring, transesophageal echocardiography (TEE), concepts of anesthetic management unique to different types of cardiac surgical procedures, and various considerations in the management of patients undergoing procedures in the OR, hybrid OR, or hybrid cath lab with or without use of CPB.
I. Preoperative Visit
A preoperative visit by the cardiac anesthesiologist is essential before all operations. This provides an opportunity to review the patient’s history, perform a relevant examination, and explain the techniques of monitoring and postoperative ventilatory support. This evaluation should identify any potential problems that might require further work‐up or could influence intraoperative management.
History: cardiac symptoms, significant comorbidities, previous anesthetic experiences, surgical procedures, allergies, medications, and recent use of steroids.
Examination: heart, lungs, loose teeth, intubation concerns based on oral anatomy (the Mallampati score), the thyromental distance, which is measured from the thyroid notch to the jaw with the head extended, >7 cm suggesting possible difficult intubation, range of motion of the neck, and jaw laxity.
The anesthesiologist should confirm with the patient the surgeon’s instructions on which medications to continue up to the time of surgery, which ones to stop, and which ones to take in modified doses. Specifically, they should tell the patient to:
Continue all antihypertensive and antianginal medications up to and including the morning of surgery. Exceptions may include angiotensin‐converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), which arguably should be withheld the morning of surgery to reduce the risk of low systemic resistance in the perioperative period.1–4
Withhold long‐acting insulin the night before and not take any insulin or oral hypoglycemic medications the morning of the surgery. Blood glucose should be obtained on arrival in the OR and checked frequently during surgery with coverage provided by intravenous (IV) insulin.
Follow the surgeon’s recommendations for cessation of anticoagulants and antiplatelet agents.5,6
Warfarin should be stopped at least four days preoperatively so that the INR will normalize before surgery. The INR can be reversed for more urgent surgery with vitamin K, fresh frozen plasma, or prothrombin complex concentrate (Kcentra).7
Aspirin can be stopped 3–5 days before valvular surgery in patients without coronary disease. However, aspirin 81 mg daily should be continued in most coronary patients and should have little impact on perioperative bleeding. The benefits of its preoperative use on improving graft patency remain controversial.8–11
The P2Y12 inhibitors should be stopped five days (clopidogrel and ticagrelor) and seven days (prasugrel) before elective surgery. If surgery is indicated within 6–12 months after a drug‐eluting stent (DES) has been placed, stopping these medications prior to surgery may increase the risk of stent thrombosis. Therefore, in this situation, as well as when the patient needs urgent surgery after DES placement, the surgeon may adopt a bridging plan, such as stopping the P2Y12 for a few days and then initiating a glycoprotein IIb/IIIa inhibitor for a few days, which is then stopped four hours prior to surgery.12,13
Unfractionated heparin (UFH) may be continued into the OR for patients with critical coronary disease, but otherwise it can be stopped about four hours before surgery.
Dissipation of the full effect of other anticoagulants takes 4–5 half‐lives. Therefore, low‐molecular‐weight heparin (LMWH), which has a half‐life of 4–5 hours, should be held for 24 hours. The non‐vitamin K antagonist oral anticoagulants (NOACs), including dabigatran, apixaban, and rivaroxaban have half‐lives of about 12 hours in older patients with normal renal function, so the last dose should be given 48 hours prior to surgery.6
Informed consent should be obtained for anesthesia management, including the insertion of monitoring lines, with a discussion of potential complications.
II. Preoperative Medications
These are usually not given before the patient is brought into the holding area or the OR for line insertion. Once the initial IV lines are inserted, low doses of midazolam (1–5 mg IV) with fentanyl (0.2–2 μg/kg or about 50–200 μg) can be given to reduce the patient’s anxiety and produce amnesia and allow for the safe insertion of additional monitoring lines without producing hemodynamic stress. Prophylactic antibiotics should be given within one hour of skin incision (starting two hours beforehand for vancomycin).14
III. Intraoperative Monitoring and Transesophageal Echocardiography
Patients undergoing cardiac surgical procedures are extensively monitored. Hemodynamic alterations and myocardial ischemia that occur during the induction of anesthesia, in the prebypass period, during CPB, and following resumption of cardiac activity can have significant adverse effects on myocardial function and recovery. It should be noted that, even though both hypertension and tachycardia can increase myocardial oxygen demand, an increase in heart rate results in more myocardial ischemia at an equivalent increase in oxygen demand.15
Standard monitoring in the OR consists of a five‐lead ECG system, a radial (and occasionally femoral) arterial line, noninvasive blood pressure cuff, pressure monitoring from a central venous pressure (CVP) line or Swan‐Ganz pulmonary artery (PA) catheter, pulse oximetry, and an end‐tidal CO2 measurement (Figure 4.1). In addition, cerebral oximetry, core body temperature (usually from a “temp probe” Foley catheter) and urine output through the Foley catheter are monitored.
For uncomplicated coronary artery bypass surgery in patients with normal or mildly depressed ventricular function, the use of a CVP monitoring line instead of a PA catheter can provide an adequate assessment of filling pressures.16
Specially designed Swan‐Ganz catheters can be used to obtain continuous cardiac outputs and mixed venous oxygen saturations.
TEE is routine and is cost‐effective in providing useful information that may alter the operative approach.17–19 There should be provisions available to perform epiaortic scanning to assess for ascending aortic atherosclerosis, which may also influence the conduct of the operation.20,21
Swan‐Ganz pulmonary artery catheters are usually placed after induction and intubation to minimize patient discomfort. However, they may be placed before the induction of anesthesia in patients with severe left ventricular (LV) dysfunction. Flow‐directed catheters are used to measure right‐ (CVP) and left‐sided filling pressures (pulmonary artery diastolic [PAD] and pulmonary capillary wedge [PCW] pressures), and obtain thermodilution cardiac outputs. Despite the nearly universal use of these catheters to carefully monitor patients and provide objective data on cardiac performance in the pre‐ and postbypass periods, it has not been demonstrated that they influence the outcome of cardiac surgery.
The catheter is usually inserted through an 8.5 Fr introducer placed into the internal jugular (IJ) vein or, less commonly, the subclavian vein. Ultrasound‐guided access, using an echo probe on the neck to identify the IJ vein, is very helpful in facilitating line placement (Figure 4.2). The introducer sheath contains one side port that provides central venous access for the infusion of vasoactive medications and potassium. Multilumen introducers, such as the 8.5 Fr and 9 Fr high‐flow advanced venous access (AVA) device (Edwards Lifesciences) or the Teleflex multilumen access catheter (MAC) with a 12‐gauge proximal lumen and a 9 Fr distal lumen, can provide additional venous access in patients with poor arm veins and limited peripheral access. A manifold with multiple stopcocks is attached to the side port of the introducer or to one of the additional ports of the AVA/MAC through which all medications are administered.
The catheter is passed into the right atrium, and the balloon at the catheter tip is inflated. The catheter is advanced through the right ventricle (RV) and PA into the PCW position, as confirmed by pressure tracings (Figure 4.3). The PA tracing should reappear when the balloon is deflated. Note: caution is essential in passing the catheter through the RV in patients with a left bundle branch block (LBBB), in whom complete heart block might occur. In this situation, unless provisions for urgent pacing are available, such as external pacing/defibrillator pads, it is best to wait until the chest is open before advancing the catheter, so that the surgeon can directly pace the heart if necessary.22
The proximal port of the Swan‐Ganz catheter (30 cm from the tip) is used for CVP measurements from the right atrium and for fluid injections to determine the cardiac output. Care must be exercised when injecting sterile fluid for cardiac outputs to prevent bolusing of vasoactive medications that might be running through the CVP port. Note: one must never infuse anything through this port if the catheter has been pulled back so that the tip lies in the right atrium and the CVP port lies outside the patient! This might not be noticed, because the catheter is usually placed through a sterile sheath that allows for advancement or withdrawal of the catheter. This concept must always be kept in mind when critical medications, such as heparin prior to cannulation, are being administered.
The distal port should always be transduced and displayed on a monitor to allow for the detection of catheter advancement into the permanent wedge position, which could result in PA injury. Balloon inflation (“wedging” of the catheter) is rarely necessary during surgery. Medication should never be given through the distal PA port.
A variety of advanced technology Swan‐Ganz catheters are available that provide additional functions.
Swan‐Ganz Paceport catheters have additional ports for the placement of right atrial and ventricular pacing probes, which is helpful during minimally invasive surgery when access to the heart is limited.
Catheters have been designed for assessment of continuous cardiac outputs (CCO) or mixed venous oxygen saturations (SvO2) by fiberoptic oximetry (Figure 4.4). These are helpful during off‐pump surgery to evaluate the patient’s hemodynamic status and may contribute to a therapeutic maneuver in many patients. The Vigileo/FloTrac (Edwards Lifesciences) cardiac output monitoring system is also useful during off‐pump surgery,23,24 and may be considered when there is difficulty placing a Swan‐Ganz catheter or when thermodilution cardiac outputs are unreliable (moderate–severe tricuspid regurgitation).25
Swan‐Ganz catheters for CCO and SvO2 monitoring may also include the technology to provide measurements of RV ejection fraction and RV end‐diastolic volume. They are particularly valuable in patients with pulmonary hypertension and compromised RV function.26
The primary concerns during the insertion of a PA catheter are arterial puncture, arrhythmias during passage through the RV, and potential heart block in patients with preexisting LBBB. Other complications of Swan‐Ganz catheters are noted on pages 354–355.
Pulmonary artery perforation is a very serious complication.27–29 It may occur during insertion of the catheter or during the surgical procedure when hypothermia causes the catheter to become rigid. Since a cold, stiff catheter may advance into the lung when the heart is manipulated, it is advisable to pull it back slightly during CPB to prevent perforation and then to re‐advance it after CPB. Migration of the catheter into the wedge position may be evident by a loss of pulse pressure in the PA waveform before or after bypass or by a very high PA pressure measurement on bypass when the heart is decompressed.
If perforation occurs, blood will appear in the endotracheal tube. The goals of management are to maintain gas exchange and arrest the hemorrhage. Positive end‐expiratory pressure (PEEP) should be applied to the ventilator circuit. If the degree of hemoptysis is not severe, it may abate once CPB is terminated and protamine is administered.
If the airway is compromised by bleeding, CPB should be resumed with venting of the PA. Bronchoscopy is then performed with placement of a bronchial blocker or a double‐lumen endotracheal tube to provide differential lung ventilation. The pleural space should be entered to evaluate the problem. If significant bleeding does not abate after application of PEEP or occlusion of the hilar vessels, pulmonary resection may be required. Use of femoral artery–femoral venous extracorporeal membrane oxygenation (ECMO) has been described to control bleeding by lowering the PA pressures, but it is risky because it requires persistent heparinization.30 Because of the risk of recurrence, pulmonary angiography and embolization may be considered once the bleeding is controlled.
Intraoperative TEE has become routine in most cardiac surgical centers, being beneficial in coronary artery bypass grafting (CABG) operations and essential during valvular surgery.17–19,31 The probe is placed after the patient is anesthetized and before heparinization. TEE provides an analysis of regional and global RV and LV function, is very sensitive in detecting ischemia,32 and identifies the presence of valvular pathology or intracardiac masses (Table 4.1 and see Figures 2.21–2.28, pages 148–153). Color flow, continuous wave, and pulsed wave Doppler are used to analyze valvular function or suspected shunts. Although TEE may image the aorta for atheromatous disease, epiaortic imaging provides better visualization of the ascending aorta and arch when there are significant concerns about atheromatous disease.20,21 Having an individual trained in performing and reading TEEs, be they a cardiac anesthesiologist or a cardiologist, is essential to optimize its usefulness.
Before the probe is placed, consideration must be given to contraindications to TEE placement that could produce catastrophic complications, such as hypopharyngeal, or proximal or distal esophageal perforation or bleeding, which are noted in less than 0.1% of patients.33–36 TEE must be used cautiously or avoided in patients with prior esophageal surgery or with known esophageal pathology, such as strictures, Schatzki’s ring, or esophageal varices.
TEE allows for advancement/withdrawal, rotation, and “multiplaning” of the probe through 180 degrees, thus affording excellent images of the heart in multiple views. The probe is advanced up and down the esophagus and then into the stomach for transgastric views. The American Society of Echocardiography (ASE) and the Society of Cardiovascular Anesthesiologists defined 20 standard views for a routine examination in their report from 199937 and expanded the recommendations to 28 standard views in their 2013 update.31 These include 15 mid‐esophageal (ME) views, nine transgastric (TG) views, and four aortic views, which can be obtained in a sequential fashion. These images provide multiple long‐axis (LAX) and short‐axis (SAX) views of all four cardiac valves, the four cardiac chambers, and the great vessels. The 2013 update can be accessed online at www.onlinejase.org and provides links to videos of each of the views. The most important views during cardiac surgery (Figures 4.5–4.7) include the following:
Multiplaning of the probe in the mid‐esophagus allows for acquisition of four‐ and five‐chamber views (0–10°), the mitral commissural view (50–70°), and the two‐chamber view (80–100°) (Figure 4.5). These views are helpful in assessing which mitral valve scallops are involved in patients with degenerative mitral regurgitation (MR). The bicaval view (Figure 4.5E) and SAX view at the base of the aortic valve are used to optimize the site for transseptal puncture during percutaneous mitral valve procedures. The ME SAX view (Figure 4.6A) is used to visualize the three aortic valve leaflets, and the ME LAX LVOT view (Figure 4.6B) is an excellent image for evaluation of aortic and mitral valve pathology, LV function, intracardiac air when weaning from CPB, and for positioning of MitraClip devices.
With the probe anteflexed in the TG position (Figure 4.7), the most helpful views include the following:
The LV SAX views (0–20°) extending from the apex toward the base to assess global and regional LV function and LV wall thickness.
The TG two‐chamber view (90–110°) to identify the mitral valve, submitral apparatus, and the anterior and inferior walls of the LV.
The TG RV two‐chamber (inflow) view (with clockwise rotation of the probe at 90–110°) to show the tricuspid valve and right heart chambers.
The TG LAX view (120–140°) to measure aortic valve gradients.
The deep TG five‐chamber view to assess LV function, but primarily to measure the aortic valve gradient.
Imaging of the aorta is usually performed after obtaining the TG views and is obtained in both SAX and LAX views as the probe is pulled back into the esophagus. This allows for imaging of the ascending and descending aorta and the aortic arch.
During on‐pump coronary artery surgery, a prebypass TEE will provide a baseline analysis of regional and global ventricular function. The TG mid‐papillary SAX view and most ME LAX views of the LV can be used to assess regional wall motion (RWM). The ability of the heart muscle to thicken is consistent with viability, whereas areas of thinned‐out muscle represent infarcted areas. Following bypass, slight improvement in previously ischemic zones may be noted, especially with inotropic stimulation. Areas of hypokinesis may represent stunned or hibernating myocardium that have contractile reserve and may gradually recover function after revascularization. The new onset of hypokinesis raises the specter of hypoperfusion from an anastomotic or graft problem, incomplete revascularization, or inadequate myocardial protection. The new onset of MR may reflect loading conditions but is also consistent with ischemic dysfunction.
During off‐pump surgery, the ME windows are best for assessing RV and LV function and the presence of MR. Baseline views are obtained. During vessel occlusion, TEE should assess for the acute development of regional LV dysfunction or acute MR during construction of left‐sided grafts and for RV dysfunction during right coronary grafting. The TG views are not helpful when the heart is elevated out of the chest.38,39 The development and persistence of a new RWM abnormality after a graft anastomosis is completed suggest a flow problem, usually at the anastomosis. However, the latter may be present even in the absence of a RWM abnormality.
In minimally invasive access procedures (usually aortic or mitral valve surgery), TEE can confirm the location of the retrograde coronary sinus catheter since it cannot be palpated by the surgeon. It can also visualize the intracardiac location of a femoral venous catheter and identify the location of an aortic endoballoon. Upon weaning from bypass, TEE is essential to identify intracardiac air and assess valve competence.
Aortic valve surgery. The best TEE views of the aortic valve are obtained in the ME SAX and LAX views, with use of the TG views to obtain aortic valve gradients. These images are important for the surgeon to:
Quantify the degree of aortic stenosis (AS) by planimetry and by continuous wave and pulsed wave Doppler flow analysis. This provides peak and mean transvalvular pressure gradients and calculates the aortic area using the continuity equation.
Quantify the degree of aortic regurgitation (AR) using color flow and continuous wave Doppler analysis. If moderate to severe, this will render delivery of antegrade cardioplegia into the aortic root ineffective.
Assess the degree of LV hypertrophy and its nature (concentric, septal).
Assess annular and aortic root size and identify an annular abscess in patients with endocarditis.
Identify the presence of systolic and/or diastolic dysfunction (by looking at transmitral flow), which may influence filling pressures and pharmacologic management coming off‐pump.
After bypass, intracardiac air is best assessed in the ME LAX view, and ventricular function is best determined in the ME LAX, TG LAX, and SAX views. Imaging to assess opening and closing of valve leaflets, identify transvalvular and paravalvular leaks, and calculate aortic valve gradients is then performed. Transvalvular regurgitation should be minor and located centrally after a bioprosthetic AVR, but may be eccentric if a leaflet has been distorted by the aortic closure sutures. Multiple trace jets are anticipated after St. Jude (Abbott) bileaflet valve replacements. Paravalvular leaks may need to be reevaluated by direct visualization. Competence of homografts, autografts (Ross procedure), and the native aortic valve in a valve‐sparing root procedure should be confirmed. Rarely, an unusual finding may be demonstrated, such as a ventricular septal defect or an aorto‐left atrial fistula. Flow into the left main coronary artery can be visualized in the ME SAX view.
Following transcatheter aortic valve replacement (TAVR), TEE is used if the procedure is performed under general anesthesia. If the procedure is performed under sedation, transthoracic imaging is adequate to identify paravalvular leaks in the parasternal LAX and SAX views, and to calculate a transvalvular gradient in the apical four‐chamber view.
Mitral valve surgery. TEE is essential to identify the anatomic abnormality responsible for the MR, quantitate its severity, and evaluate the surgical result. The best visualization of the mitral valve is from the mid‐lower esophagus and includes the ME two‐ and four‐chamber views, the ME mitral commissural view, and the ME LAX views. These, along with the three‐dimensional (3D) en face views, allow for the visualization of all of the mitral valve scallops to help identify the precise location of the pathology causing the MR.40
Prebypass assessment should confirm the valvular pathology and identify the mechanism of MR. For example, degenerative MR with a flail leaflet will produce an eccentric jet, whereas functional MR with depressed LV function may produce a central jet from remodeling with papillary muscle displacement or an eccentric jet from leaflet tethering (see Figures 2.22–2.24, pages 148–150). Rotation of the probe to sequentially provide the four‐chamber, mitral commissural, and two‐chamber views should allow for localization of the prolapsed scallop.41 In some patients with MR, it is not uncommon to note a discrepancy in the degree of MR between preoperative echoes and intraoperative TEE due to alteration in loading conditions. The left atrial appendage should be evaluated for the presence of thrombus.
In anticipation of a mitral valve repair, markers for systolic anterior motion should be analyzed. These include an end‐diastolic diameter (EDD) <45 mm. aorto‐mitral angle <120°, coaptation–septum distance <25 mm, posterior leaflet height >15 mm, and basal septal diameter ≥15 mm.42
Assessment of RV function is also important during mitral valve surgery. Markers of RV dysfunction include an RV fractional area change (FAC) <35% or a tricuspid annular plane systolic excursion (TAPSE, the distance traveled between end‐diastole and end‐systole at the lateral corner of the tricuspid annulus) <16 mm.43
During weaning from bypass, TEE is essential to identify intracardiac air. After termination of bypass, it should be used to assess the competence of valve repairs, identify paravalvular leaks after mitral valve replacement (MVR) (Figure 4.8), and assess LV and RV function. Occasionally, the TEE will reveal an unsuspected finding such as:
Systolic anterior motion (SAM) of the anterior mitral valve leaflet obstructing the LV outflow tract (after valve repairs or MVR with retention of the anterior leaflet)
Evidence of valve dysfunction with a trapped or obstructed leaflet
Aortic valve regurgitation after a difficult mitral valve operation (due to suture entrapment of an aortic valve cusp or distortion of the aortic annulus from placement of too small a mitral valve)
Marked lateral wall hypokinesis from circumflex artery entrapment by valve sutures
Percutaneous mitral valve repair with the MitraClip device is performed under general anesthesia with TEE guidance. Specific views are utilized to perform the septal puncture (bicaval, SAX at the base, four‐chamber) and then for maneuvering the system down to the mitral valve to avoid passage into the pulmonary veins or left atrial appendage. The mitral commissural and LVOT views are used to place the clip in the proper position with the aid of the 3D en face view to ensure correct clip orientation. Clip stability should be assessed prior to and after the clip has been deployed.
The diagnosis of an aortic dissection can be confirmed by TEE once the patient is anesthetized (see Figure 2.27, page 152). It may not only identify the intimal flap but can also determine whether AR is present, mandating aortic valve resuspension or replacement. If a large pericardial effusion is present, axillary or groin cannulation may be necessary for the emergent institution of CPB before opening the pericardium. TEE can also identify flaps in cases of iatrogenic dissections at the cannulation or clamp sites.44
In thoracic aortic surgery, TEE is useful in assessing cardiac performance and intracardiac volume status during the period of clamping and after unclamping, when PA pressures tend to be elevated out of proportion to preload. This may influence fluid and pharmacologic management.45 Positioning of an endograft for thoracic aortic repairs, including traumatic aortic tears, type B dissections, and thoracic aortic aneurysms, is usually confirmed by fluoroscopy, and the TEE probe should be pulled back to avoid interference with the x‐ray beam.
Table 4.1 Specific Uses of Intraoperative Echocardiography
Identify or confirm preoperative pathology (see Table 2.3, page 154) Epiaortic imaging for aortic atherosclerosis in ascending aorta, arch Intracardiac thrombus (LA appendage, LV apex)
During Off‐pump Surgery
Regional wall motion abnormalities
Postbypass Coronary disease Valve surgery
Regional dysfunction (incomplete/inadequate revascularization) Presence of intracardiac air on weaning from CPB RV and LV function (circumflex artery entrapment after MVR, coronary ostial obstruction after AVR) Valve regurgitation from paravalvular leak or inadequate repair Outflow tract obstruction after mitral valve repair or replacement Obstruction to prosthetic leaflet opening or closing Residual stenosis after commissurotomy
Location of device relative to aortic arch
Evaluation of iatrogenic aortic dissection
IV. Anesthetic Considerations for Various Types of Heart Surgery
Anesthetic management must be individualized, taking into consideration the patient’s age, comorbidities, the nature and extent of coronary or valvular disease, the degree of LV dysfunction, and plans for early extubation. These factors will determine which medications should be selected to avoid myocardial depression, tachycardia or bradycardia, or to counteract changes in vasomotor tone. Generally, a balanced anesthetic technique using a combination of narcotics and potent inhalational agents is used for all open‐heart surgery to minimize myocardial depression. Specific anesthetic concerns for various disease processes are presented in this section.
Coronary artery bypass surgery
Factors that increase myocardial oxygen demand, such as tachycardia and hypertension, must be prevented in the prebypass period, especially during the induction of anesthesia. Hypotension, often resulting from the vasodilating effects of narcotics, anxiolytics (midazolam), and sedatives (propofol), should be counteracted with fluids and α‐agents, since hypotension is more likely to produce ischemia than hypertension.
Detection and treatment of ischemia is critical in the prebypass period. TEE is the most sensitive means of detecting ischemic RWM abnormalities and can be recommended for all cardiac cases. Ischemia may also be manifested by an elevation in the PA pressures or by ST segment changes in the ECG leads. Aggressive management with nitroglycerin, β‐blockers (esmolol), and narcotics can usually control prebypass ischemia.46 Placement of an intra‐aortic balloon pump (IABP) may be considered for ischemia, but if the patient is truly unstable, prompt initiation of CPB may be necessary.
Narcotic/sedative regimens are the standard for coronary surgery, especially in patients with LV dysfunction. Use of low‐dose fentanyl or sufentanil with inhalational anesthetics during the surgery, and use of propofol or dexmedetomidine at the conclusion of surgery allow for early postoperative extubation. Use of the short‐acting narcotic remifentanil along with a volatile inhalational anesthetic with rapid onset and offset of effect, such as sevoflurane or desflurane, allows for “ultra‐fast tracking” with extubation in the OR or upon arrival in the ICU.47 Remifentanil has been shown to minimize the systemic inflammatory response and shorten ventilation time, but it is associated with chest wall rigidity and the occurrence of chronic pain syndromes for up to one year.48,49
Monitoring techniques for off‐pump surgery (OPCAB) commonly involve a continuous cardiac output Swan‐Ganz catheter with in‐line mixed venous oxygen saturation monitoring. Tilting of the OR table (Trendelenburg position and to the right) to augment cardiac filling, judicious fluid administration, antiarrhythmic therapy (lidocaine/magnesium), α‐agents (phenylephrine) and inotropes (epinephrine/milrinone), and, on occasion, insertion of an IABP may be used to produce hemodynamic stability when the heart is rotated for exposure of the coronary arteries. ß‐blockers to reduce the heart rate may be helpful to reduce cardiac motion during the distal anastomoses. The blood pressure may be lowered to the 80–90s during construction of the proximal anastomoses to reduce the risk of aortic injury when a sideclamp is placed on the aorta. Use of a warming system, especially the Kimberly‐Clark warming system (formerly the Arctic Sun temperature management system), is helpful in preventing hypothermia during OPCAB surgery.50 The essential elements of a successful off‐pump operation include a patient surgeon who uses good judgment in deciding when off‐pump surgery is feasible and when conversion to CPB or right‐heart assist is necessary, an anesthesiologist who is experienced and comfortable with off‐pump surgery, and a qualified, actively involved first assistant. See section IX (pages 262–264) for a more detailed discussion of anesthesia for off‐pump surgery.
MIDCAB procedures involve internal thoracic artery (ITA) takedown either under direct vision or with endoscopic or robotic assistance. The anastomosis to the left anterior descending (LAD) artery is then performed through a small thoracotomy incision, but it can also be performed robotically. One‐lung anesthesia is generally used. Even with use of stabilization platforms, slowing the heart down pharmacologically may be helpful. Robotic coronary surgery can be performed off‐pump or on‐pump with groin cannulation.
Left ventricular aneurysms (LVAs). Anesthetic drugs that cause myocardial depression must be avoided because of the association of LVAs with significant LV dysfunction. Swan‐Ganz monitoring is important in optimizing preload and contractility before and after bypass. TEE is the most sensitive means of detecting the presence of LV thrombus and provides an excellent assessment of ventricular wall thickness and motion (akinesia, hypokinesia, and dyskinesia noted with aneurysms). Aneurysm repairs may be performed with an unclamped aorta, allowing the surgeon to palpate the margin between viable and scarred myocardium. Proper deairing during closure is essential and can be monitored by TEE.
Ventricular septal defects are usually operated upon on an emergent basis when the patient is in cardiogenic shock, usually on inotropic support and an IABP. Thus, myocardial depression must be avoided. Systemic hypertension may increase the shunt and should be prevented. TEE is invaluable in identifying the persistence of a left‐to‐right shunt.
Aortic valve surgery
Aortic stenosis (AS). The induction of anesthesia is a critical period for patients with AS. The LV is generally hypertrophied and stiff with evidence of diastolic dysfunction. Avoidance of hypovolemia, myocardial depression, vasodilation, tachycardia, or dysrhythmias is important, as all of these can lower the cardiac output precipitously.
Blood pressure issues. Hypotension, usually as a result of vasodilation, can produce myocardial ischemia. Volume should be given to maintain intravascular volume, with the understanding that PA pressures may rise quickly with small infusions of volume in noncompliant ventricles and can adversely affect pulmonary function. Systemic resistance should be supported with a small bolus or infusion of an α‐agent, such as phenylephrine or norepinephrine. Hypertension can make aortic cannulation for CPB dangerous. It should be addressed by increasing the depth of anesthesia, use of propofol, or use of ß‐blockers. Post‐CPB, strict adherence to blood pressure control is essential to minimize bleeding from the aortotomy site and avoid the risk of dissection.
Heart rate. Loss of “atrial kick” can substantially compromise the cardiac output in patients with LV hypertrophy. Thus, atrial fibrillation (AF) developing before the initiation of bypass is often associated with profound hypotension for which cardioversion may be necessary. Tachyarrhythmias will compromise LV filling and can also precipitate ischemia. A short‐acting ß‐blocker, such as esmolol or IV metoprolol, may be helpful to control a sinus tachycardia. A reentrant supraventricular or junctional tachycardia may require cardioversion. Sinus bradycardia or a slow junctional rhythm may cause hypotension and can be treated by attaching “alligator” leads to the right atrium to restore a supraventricular mechanism once the pericardium has been opened. Prior to that time, very slow rhythms can be treated by a bolus dose of 5–15 mg of ephedrine, 5–10 μg of epinephrine, or 0.2–0.4 mg of glycopyrrolate.
The best TEE views of the aortic valve are obtained in the ME SAX and LAX views (Figure 4.6). The important information prior to initiating CPB includes confirmation of the degree of AS and regurgitation and the estimated aortic annular diameter. During weaning from bypass, assessment for intracardiac air is essential and is best seen in the ME LVOT LAX view. Postbypass, valve competence, valve gradient, and LV function are important and should be evaluated by the anesthesiologist and surgeon. Significant abnormalities in valve function (primarily paravalvular or transvalvular regurgitation), and especially a significant RWM abnormality possibly related to coronary ostial obstruction by the valve sewing ring, need to be addressed.
Most procedures are performed through a median sternotomy incision. “Minimally invasive” approaches include an upper sternotomy and right upper thoracotomy approach. Both central and peripheral cannulation for CPB may be used and the anesthesiologist may on occasion be asked to place venous drainage catheters, a PA vent, or a cardioplegia catheter. Anesthetic management of minimally invasive AVR is discussed in section XI on page 268.
Transient AV block necessitating AV pacing upon termination of CPB is not uncommon in aortic valve surgery, and about 5% of patients may require a permanent pacemaker if this persists. It is critical that the pacing threshold be adequate prior to chest closure if the patient has third‐degree heart block.
Comments on anesthetic management during TAVRs are noted in section VII on pages 268–269.
Aortic regurgitation (AR). Chronic AR produces volume overload and progressive LV dilatation and compromise of ventricular function. It is associated with a low diastolic pressure that can compromise coronary perfusion.
Hypotension will worsen coronary ischemia while hypertension and bradycardia will increase regurgitation. Thus, a delicate balance must be sought to optimize hemodynamics by maintaining satisfactory preload, treating bradycardia, and avoiding hyper‐ or hypotension before going on CPB. Volatile anesthetics that depress contractility should be avoided. These patients tend to be vasodilated on pump and afterwards as well, often requiring vasopressor support.
The ME aortic valve LAX and SAX and TG LAX views with color Doppler are best for assessing AR, and allow for the measurement of the pressure half‐time (P1/2t). Careful examination of the valve in the ME SAX view is best to determine whether it is repairable or not.
Myocardial protection, especially of the RV, may be compromised in patients with severe AR, since antegrade cardioplegia cannot be administered into the aortic root. Retrograde cardioplegia and use of ostial antegrade perfusion are usually used. Patients with occluded right coronary arteries are at higher risk for RV dysfunction. Post‐CPB, inotropic support may be necessary in patients with pre‐existing LV dysfunction, and many patients are vasodilated and hypotensive despite good cardiac function, requiring an α‐agent or vasopressin for blood pressure support.
The LV is usually dilated and compliant and significant volume infusions may be necessary to maintain preload and cardiac output coming off‐pump.
Hypertrophic obstructive cardiomyopathy. Measures that produce hypovolemia or vasodilation must be avoided because they increase the outflow tract gradient. Volume infusions should be used to maintain preload, with the use of α‐agents to maintain systemic resistance. Use of β‐blockers and calcium channel blockers to reduce the heart rate and contractility are beneficial in the immediate preoperative and prebypass periods. Inotropic drugs with predominantly β‐adrenergic effects could provoke the gradient and must be avoided. TEE assessment of subvalvular pathology is essential so that the surgeon can address issues with papillary muscle pathology in addition to performing a septal myectomy. Assessment of the degree of MR prior to and after surgical repair is essential.51
Mitral valve surgery
Mitral stenosis (MS). Severe MS is associated with impairment to LV filling resulting in an elevation of left atrial and PA pressures to maintain cardiac output. This may result in RV dilatation and functional TR as well. The LV is usually small. Severe MS is often associated with AF with dilated atrial chambers, for which patients should be on preoperative anticoagulation to reduce the risk of formation of thrombus in the left atrial appendage. Attention should be paid to maintaining preload, reducing heart rate, and preventing an increase in pulmonary vascular resistance (PVR) in the prebypass period.
Preload must be adjusted judiciously to ensure adequate LV filling across the stenotic valve while simultaneously avoiding excessive fluid administration that could lead to pulmonary edema.
In patients with severe pulmonary hypertension and RV dysfunction, a volumetric (RVEF) Swan‐Ganz catheter is valuable in the assessment of RV volume and the RV ejection fraction. The PA diastolic pressure may be inconsistent with the left atrial pressure, and placement of a left atrial line for monitoring postbypass may be considered. Balloon inflation (“wedging”) of a PA catheter should be avoided or performed with a minimal amount of balloon inflation in patients with pulmonary hypertension because of the increased risk of PA rupture. If the patient remains hypotensive despite adequate preload, an α‐agent is preferable to restore the blood pressure. Inotropic agents are usually not of much value, since LV function is usually normal, but they may be beneficial if there is evidence of RV dysfunction (usually epinephrine +/− milrinone).
Prebypass TEE is helpful in identifying left atrial thrombus. It should also be used to assess RV function, which can be compromised due to pulmonary hypertension.
The heart rate should be reduced to <80/min to prolong the diastolic filling period. For patients in AF, small doses of esmolol or diltiazem can be used to control a rapid ventricular response. If the AF is of short duration, cardioversion can be performed for an uncontrolled rate with hypotension as long as the TEE confirms absence of thrombus in the left atrial appendage. Cardiac output is usually marginal in patients with MS and can be further compromised if the ventricular rate is excessively slow.
Factors that can increase the PVR must be avoided. Preoperative sedation can induce hypercarbia and should be minimized. Hypoxemia, hypercarbia, acidosis, and nitrous (not nitric) oxide should be avoided in the OR. The PVR can be reduced with systemic vasodilators (propofol) or nonspecific pulmonary vasodilators (usually nitroglycerin) before bypass. Following bypass, RV support is best achieved using inotropic agents that can produce pulmonary vasodilation (usually milrinone). In patients with severe pulmonary hypertension and RV dysfunction, inhaled nitric oxide, epoprostenol (Flolan), or iloprost (Ventavis) can be used. Further discussion of the postoperative management of mitral valve surgery and the management of RV dysfunction is noted on pages 396–397 and 530–534.
TEE should be used during weaning from bypass to identify intracardiac air. Once off bypass, TEE should assess the mean gradient if a commissurotomy is performed, and check for paravalvular or transvalvular leaks of a mitral prosthesis. For mechanical valves, proper opening and closing of the leaflets must be confirmed.
Although the INR should be corrected prior to surgery, levels of clotting factors are rarely normal despite a lowering of the INR into the normal range, so one should anticipate a potential coagulopathy and the potential need for clotting factors (fresh frozen plasma and/or cryoprecipitate). Rarely, AV groove disruption may occur, especially in patients with mitral annular calcification, which will cause catastrophic hemorrhage.
Mitral regurgitation (MR)
MR results in volume overload of the left atrium and ventricle, which subsequently dilate and develop increased compliance. Eventually, the PA pressure rises, causing RV dysfunction and TR, and then the LV, despite the low pressure unloading, begins to fail. Poor LV function with severe MR is an ominous prognostic sign since restoration of mitral valve competence will “unmask” LV dysfunction that was not appreciated due to LV unloading through the regurgitant valve.
Measures that can increase PA pressure, such as hypoxemia, hypercarbia, acidosis, and nitrous oxide, should be avoided. Preoperative sedation should be light or avoided altogether.
In the prebypass period, adequate preload must be maintained to ensure forward output. Some patients come to the OR “dry” because of chronic diuretic usage, while others may be in heart failure from severe MR. Systemic hypertension should be avoided, because the increased resistance to outflow will usually worsen MR. If the patient has ischemic MR or a borderline cardiac output, use of systemic vasodilators or an IABP will improve forward flow. Inotropes with vasodilator properties (i.e. milrinone or dobutamine) should be considered in patients with markedly compromised LV function. Heart rate should be optimized; a slightly faster heart rate in the 80–90s will reduce the degree of MR, and a slow heart rate may cause hypotension.
TEE is invaluable in identifying the precise anatomic cause for MR, assessing the risk of SAM42 (see section D.7.b, page 231), and in evaluating the surgical result. TEE is performed once the patient is anesthetized. The critical views include the ME two‐ and four‐chamber views, the ME mitral commissural view, and the ME LAX views. These, along with the 3D en face views, allow for the visualization of all of the mitral valve scallops to help identify the precise location of the pathology causing the MR. Occasionally, there is a discrepancy between preoperative and intraoperative studies, due to alterations in systemic resistance and loading conditions. Elevating the blood pressure with an α‐agent may increase the amount of regurgitation in patients with moderate ischemic MR and aid in the decision to repair the valve during coronary bypass surgery. TEE is evaluated for intracardiac air when weaning from bypass and for evaluating mitral valve competence after a repair, regurgitant leaks after a mitral valve replacement, and RV and LV function.
Measures noted above to decrease PA pressures may be used before or after bypass to optimize RV function. Both RV and LV function may be compromised after mitral valve surgery, requiring judicious hemodynamic support. This is discussed in detail on pages 385–396 and 530–534.
Percutaneous mitral valve repairs (MitraClip) are performed under general anesthesia with the use of TEE monitoring. A Swan‐Ganz catheter may be placed for documentation of right heart pressures, but it is not essential. Left atrial pressures (assessment of the “v” wave) before and after clip placement are obtained by direct measurement through the guide catheter. Familiarity with all of the requisite TEE images and with 3D echo imaging is critical to the success of the procedure. Reduction in the degree of MR is anticipated but is generally not as successful as a surgical repair. Further comments on anesthesia for these repairs is noted in section XIII on pages 269–271.
Maze procedure for atrial fibrillation
The cut‐and‐sew Cox‐Maze procedure to eliminate AF has been generally replaced by devices that produce comparable transmural ablation lines using either radiofrequency or cryoablation. A left atrial Maze procedure is most commonly performed as a concomitant procedure with mitral valve surgery, although a biatrial Maze may be more successful in eliminating AF (see Figures 1.28 and 1.29). Anesthesia management is directed toward the primary pathology for which surgery is being performed if the Maze procedure is performed as an adjunct. Medications may be used for rate control pre‐CPB.
Bilateral pulmonary vein isolation (PVI) with resection and oversewing of the left atrial appendage is an appropriate procedure for patients with paroxysmal AF. This operation can be performed as an adjunct to any cardiac procedure or as an isolated operation. Surgery for lone AF may be performed through a sternotomy incision or through bilateral thoracoscopic ports. This requires repositioning of the patient with the operated side elevated about 30 degrees and the use of one‐lung anesthesia to allow the surgeon better exposure to isolate the pulmonary veins. The “convergent” procedure entails a subcostal incision to place epicardial ablation lines followed by an endocardial approach by the electrophysiologist (see Chapter 1).
Most surgeons will use amiodarone for early AF prophylaxis, and this is usually given IV during the procedure (unless previously given) and then continued orally for several months.
Tricuspid valve disease
Maintenance of an elevated CVP is essential to achieve satisfactory forward flow in tricuspid stenosis. A Swan‐Ganz catheter can be placed for monitoring PA pressures, although cardiac output determinations are of little value if TR is present. If placed at the beginning of surgery, it is withdrawn into the superior vena cava (SVC) when the tricuspid valve is being addressed and then is readvanced through a repaired valve or a bioprosthetic valve replacement. If not done under direct vision by the surgeon, advancement may need to be deferred until the SVC cannula has been removed. The Vigileo/FloTrac monitor can provide adequate cardiac output measurements based on the arterial line pulse wave, but it will be inaccurate with AF.
Normal sinus rhythm provides better hemodynamics than AF, although the latter is frequently present. Slower heart rates are preferable for tricuspid stenosis and faster heart rates for TR.
Tricuspid valve surgery requires entry into the right atrium. Therefore, tourniquets are placed around the SVC and inferior vena cava (IVC) cannulas to avoid air entry into the venous lines. With the SVC tourniquet tightened, the patient’s head should be observed for congestion, which indicates inadequate drainage by the SVC cannula. An elevated CVP may be noted, depending on the location of the measurement.
Functional TR usually results from RV dilatation and dysfunction due to increased RV afterload from pulmonary hypertension. TEE assessment of tricuspid annular diameter may be helpful to the surgeon in determining whether a tricuspid valve repair is indicated for functional TR even when mild–moderate in severity.52 A dilated annulus ≥40 or ≥21 mm2 is a Class IIa indication for tricuspid repair during left‐sided repairs.53
RV dysfunction is not uncommon once valve competence has been restored and may be exacerbated by suboptimal RV protection during cardioplegic arrest. Tricuspid valve repair for severe TR in patients with preexisting RV dysfunction is very high risk, and use of inotropes that can also lower the PVR (milrinone, dobutamine, and rarely isoproterenol), selective pulmonary vasodilators, or right ventricular assist device (RVAD) support may be required.
Patients with hepatic congestion often have abnormal liver function that can impair the synthesis of clotting factors. A coagulopathy may develop after CPB, necessitating use of multiple blood component transfusions (especially fresh frozen plasma and cryoprecipitate) to control bleeding.
Anesthetic management is dictated by the hemodynamic derangements associated with the particular valve involved. TEE is invaluable in identifying valve pathology, vegetations, and perivalvular abscesses, and may occasionally demonstrate involvement of other valves not appreciated on preoperative studies.
Surgery may be required urgently for HF or cardiogenic shock when there are acute regurgitant lesions, or for persistent sepsis. These patients tend to be quite ill, often with significant respiratory, cardiac, renal, and hematologic problems. Those operated upon for large vegetations or peripheral embolization tend to be more stable. Patients with aortic valve endocarditis may develop heart block from involvement of the conduction system by periannular infection. This may require preoperative placement of a transvenous pacing wire.
Ongoing sepsis may produce refractory hypotension on pump despite the use of α‐agents. Vasopressin may be necessary to maintain blood pressure.
Maintenance of hemodynamic stability and especially avoidance of hypertension are critical to prevent aortic rupture, especially during the induction of anesthesia and line insertion. Use of a Swan‐Ganz catheter is helpful in optimizing perioperative hemodynamics. Its insertion should be delayed until after intubation to minimize the stress response or can be performed later for postoperative management.
Most patients require emergency surgery and should be considered to have a full stomach. A modified rapid‐sequence induction should be performed to minimize the risk of aspiration while ensuring hemodynamic stability.
TEE is useful in localizing the site of the intimal tear and the proximal (and occasionally the distal) extent of the dissection, the degree of AR, and the presence of a hemopericardium. Because the diagnosis of an aortic dissection is usually obtained by a contrast CT scan, TEE is best performed once the patient has been anesthetized. If the diagnosis is in doubt, a TEE may be performed in an awake patient. In this situation, TEE must be performed very cautiously with light sedation for fear of precipitating hypertension, rupture, and then tamponade.
Repair of a type A dissection is usually performed during a period of deep hypothermic circulatory arrest (DHCA). The head is packed in ice, and medications may be given to potentially provide additional cerebral protection (see section L.1). To document reaching 18–20 °C for DHCA, tympanic temperatures correlate better with arterial blood temperatures than do bladder and rectal measurements, which are considered to represent the core temperature.54 Use of a temperature management system is important to prevent temperature afterdrop during the rewarming phase. Uncommonly, the repair does not require DHCA and these measures are not necessary.55 Coagulopathies should be anticipated with this procedure, and blood clotting factors should be requested early and should be available immediately after protamine administration, if needed.
Repair of type B dissections should be accomplished by an endovascular approach if at all possible. An open surgical approach requires a period of descending aortic cross‐clamping. Because less collateral flow is present in patients with dissections than with atherosclerotic aneurysms, the risk of paraplegia is greater. Left‐heart bypass may reduce the risk of paraplegia.56 A cerebrospinal fluid (CSF) drainage catheter should be placed before the patient is anesthetized. Proximal hypertension must be controlled during application of the cross‐clamp, but it should not be so low as to compromise spinal cord perfusion. A CSF drain is also useful if an endovascular stent procedure is performed for a complicated type B dissection.57
Ascending aortic and arch aneurysms
Aneurysms limited to the ascending aorta are repaired on CPB with application of an aortic cross‐clamp. If they extend more distally or the arch is extensively involved, a period of DHCA at 18–20 °C core temperature is used. This usually ensures a lower nasopharyngeal or tympanic temperature, which correlates best with brain temperature. At this point, it is inferred that there is EEG silence with a bispectral index (BIS) analysis reading of 0. This should provide about 45 minutes of safe arrest time and minimize the risk of neurologic insult.
Adjuncts to improve cerebral protection include selective antegrade (ACP) or retrograde cerebral perfusion (RCP), and packing the head in ice.58–60 Administration of methylprednisolone 30 mg/kg may be considered, but evidence of any benefit is unclear.61,62 Some groups prefer to use cold cerebral perfusion techniques to protect the brain while maintaining the body at only moderate hypothermia (21–28 °C).62–64 One study found no difference in neurologic outcome between the use of DHCA + RCP and moderate HCA with ACP, but twice as many new diffusion‐weighted MRI lesions were noted in the latter group.64
Profound hypothermia and warming are associated with a coagulopathy. Platelets, fresh frozen plasma, and cryoprecipitate are helpful in achieving hemostasis. Supplemental use of warming devices is beneficial in warming the patient and preventing temperature afterdrop.
Descending aortic and thoracoabdominal aneurysms (TAAs)
Arterial monitoring lines are inserted in the right radial and femoral arteries to monitor proximal and distal pressures during the period of aortic cross‐clamping. The femoral line is valuable when left‐heart bypass techniques are used.
A Swan‐Ganz catheter is important to monitor filling pressures during the period of cross‐clamping. TEE is helpful in evaluating myocardial function and often demonstrates a hypovolemic LV chamber despite elevated PA pressures when the cross‐clamp is removed. Ensuring adequate intravascular volume will reduce the risk of “declamping shock” upon release of the aortic cross‐clamp.
One‐lung anesthesia using a double‐lumen or Univent tube with a bronchial blocker improves operative exposure.
Control of proximal hypertension is essential during the cross‐clamp period to minimize the adverse effects of increased afterload on LV function. However, lowering the pressure too much can reduce renal and spinal cord perfusion and increase the CSF pressure, so maintaining a pressure >130 mm Hg is recommended. Additional steps should be taken to optimize distal perfusion pressure to minimize the risk of distal ischemic injury during aortic cross‐clamping. This includes use of CSF drainage, distal perfusion to maintain collateral network perfusion pressure, and reattachment of segmental arteries T8–12.65 Cold renal perfusion, epidural cooling, or use of DHCA may also be considered.66–68
Endovascular stent placement is performed under conscious sedation or general anesthesia. Devices may be placed percutaneously or via a surgical groin incision with placement either directly into the femoral artery or through a side graft in patients with extensive aortoiliac disease. The landing zones are located by fluoroscopy. Spinal cord ischemia remains a concern with extensive endovascular repairs, and CSF drainage is recommended.69
Transvenous ICD implantation is usually performed in an electrophysiology laboratory under moderate sedation with propofol or dexmedetomidine, allowing the patient to breathe spontaneously. When ventricular fibrillation is induced, deepening the level of sedation and assisted ventilation usually suffices. This requires close nursing or anesthesia attendance and careful monitoring. Most patients have markedly depressed ventricular function, and provisions for cardiac resuscitation (personnel and equipment) should be immediately available. External defibrillator pads should be placed for rescue defibrillation.
Medications that could be potentially arrhythmogenic, such as the catecholamines, must be avoided. Antiarrhythmic medications are continued unless there are plans for an electrophysiology study, which is usually performed with the patient off medications.
Subcutaneous ICD implants may require a higher level of sedation than transvenous implants, but generally it can be accomplished without the use of general anesthesia.70
Awake patients requiring emergency cardioversion in the ICU are generally hemodynamically unstable and should be given extremely light sedation prior to being cardioverted (1–2.5 mg of midazolam or 2–5 mg morphine). If the patient is still anesthetized and sedated, an increase in the infusion rate of propofol may be considered.
Patients requiring less urgent cardioversion for hemodynamic compromise or undergoing elective cardioversion (usually after TEE confirmation of absence of left atrial appendage thrombus) should receive a small dose of propofol (0.5–1 mg/kg or approximately 50–100 mg). Alternatively, etomidate (0.3 mg/kg or a 10–20 mg bolus) can be used, especially in patients with compromised ventricular function. Etomidate may produce myoclonus in up to 50% of patients, often causing ECG interference, which makes synchronized cardioversion very difficult.71 Anesthesia stand‐by is recommended to provide airway support during the short period of sedation.
Surgery for pericardial disease
Pericardial drainage of a large pericardial effusion or for tamponade is often performed urgently or emergently. In the immediate postoperative period, emergent exploration through a full sternotomy incision may be carried out in the ICU if tamponade is associated with severe hypotension or cardiac arrest. Otherwise, emergency exploration is carried out in the OR. Most patients are still intubated and sedated, and most still have a Swan‐Ganz catheter and satisfactory venous access in place, and there is little time for insertion of additional lines. Patients are generally in a low cardiac output state, and blood pressure is dependent on adequate preload, increased heart rate, and increased sympathetic tone. Volume infusions and less commonly, β‐agonists are beneficial in trying to maintain hemodynamic stability. Any medications that slow the heart rate must be avoided, and sedatives and anesthetic drugs that produce vasodilation must be given judiciously to avoid profound hypotension and cardiac arrest. Since loss of sympathetic tone can be catastrophic in a patient with tamponade physiology, prepping and draping of the patient should be considered before the administration of additional anesthetic agents. There is generally striking hemodynamic improvement once the pericardial blood is evacuated.
In less emergent situations, drainage is usually indicated for hemodynamically significant effusions. This may be accomplished by a pericardiocentesis performed in the cath lab with local anesthesia, depending on the size and location of the effusion. If this cannot be accomplished, the procedure is performed in the OR. A large‐bore central venous line should be inserted. A subxiphoid incision can be made under local anesthesia with moderate sedation, but more commonly it is done under general anesthesia. Again, if there is evidence of tamponade, blood pressure is dependent on adequate preload, heart rate, and increased sympathetic tone, so agents that produce vasodilation, bradycardia, or myocardial depression must be avoided. The patient may need to be prepped and draped before the induction of anesthesia, to prevent cardiovascular collapse.
TEE is invaluable in identifying the size and hemodynamic effects of an effusion. With limited surgical approaches, such as a subxiphoid window or thoracoscopy, TEE can identify whether the effusion has been adequately drained.
After resolution of tamponade, filling pressures generally fall, blood pressure increases, and a brisk diuresis occurs. Depending on the duration of tamponade, some patients may require transient inotropic support after the fluid is removed.
Patients with chronic constrictive pericarditis are usually in a chronic, compensated low cardiac output state. It is similarly essential to avoid hypovolemia, vasodilation, bradycardia, or myocardial depression. After the constricted heart is decorticated, filling pressures may transiently fall, but many patients develop a low output state associated with RV dilatation and will require inotropic support. Inadequate decortication may be evident when a fluid challenge that restores the preoperative filling pressures fails to increase cardiac output. Pulmonary edema may develop if the surgeon decorticates the RV while the LV remains constricted.
V. Induction and Maintenance of Anesthesia
Cardiac anesthesia is provided by a combination of medications, including induction agents, anxiolytics, amnestics, analgesics, muscle relaxants, and inhalational anesthetics.72 Although most centers used a “balanced anesthesia” technique, studies have reported comparable results with regimens of volatile inhalational anesthetics vs. total IV anesthesia for cardiac surgery.73
Induction agents may include propofol, etomidate, ketamine, or a benzodiazepine. Most commonly, anesthesia is induced with a combination of propofol, a narcotic, and a neuromuscular blocker to provide muscle relaxation and prevent chest wall rigidity that is associated with high‐dose narcotic inductions. The most common doses for induction are propofol 1–2 mg/kg (50–100 mg), fentanyl 2.5–5 μg/kg (250–500 μg), and vecuronium 0.1 mg/kg IV followed by 0.01–0.03 mg/kg every 30 minutes. Alternative narcotics, such as sufentanil and remifentanil, are rarely used. Low‐dose fentanyl has a duration of action of 1–4 hours, which allows the patient to awaken within hours of completion of the operation. Remifentanil is a very short‐acting narcotic with a duration of action of only 10 minutes. It is beneficial in shorter operations and allows for very early awakening and extubation.
Succinylcholine is a depolarizing agent with rapid onset that can be used during rapid‐sequence inductions or in patients with difficult airways.
Although rarely used, ketamine given with a benzodiazepine is very useful in patients with compromised hemodynamics or tamponade. Ketamine does not produce myocardial depression, and its dissociative effects and sympathetic stimulant properties that produce hypertension and tachycardia are attenuated by use of a benzodiazepine.74
Subsequently, anesthesia is maintained by additional dosing of narcotics and muscle relaxants in combination with an anxiolytic, such as propofol, and an inhalational agent (Tables 4.2 and 4.3). Bispectral electroencephalographic monitoring (BIS) can be used during on‐ and off‐pump surgery to titrate and minimize the amount of medication required to maintain adequate anesthesia (a level around 55–60) while minimizing hemodynamic alterations and preventing awareness.75,76
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