Intraoperative Anesthesia Management


Left ventricle and interventricular septum

Small LV size, particularly with increased LV trabeculation

LV thrombus

LV apical aneurysm

Ventricular septal defect

Right ventricle

RV dilatation

RV systolic dysfunction

Atria, interatrial septum, and inferior vena cava

Left atrial appendage thrombus

PFO or atrial septal defect

Valvular abnormalities

Any prosthetic valve (especially mechanical AV or MV)

>Mild AR

≥Moderate MS

≥Moderate TR or >mild TS

>Mild PS; ≥moderate PR

Other

Any congenital heart disease

Aortic pathology: Aneurysm, dissection, atheroma, coarctation

Mobile mass lesion

Other shunts: Patent ductus arteriosus, intrapulmonary


AR aortic regurgitation, AV aortic valve, LV left ventricular, MS mitral stenosis, MV mitral valve, PFO patent foramen ovale, PR pulmonary regurgitation, PS pulmonary stenosis, RV right ventricle, TR tricuspid regurgitation, TS tricuspid regurgitation



RV failure occurs in up to 30% of patients following LVAD placement and is a harbinger of a poor postoperative course complications [46]. There is no preoperative predictive model for RV failure with both good sensitivity and specificity; the right ventricular failure risk score (RVFRS) and TEE are often used together to identify potential high-risk patients for postoperative RV failure [47]. Postoperative RV failure following LVAD placement can be mitigated by concomitant placement of an RVAD, but the outcomes for these patients are substantially worse [8]. Therefore the presence of preoperative RV ischemic disease may warrant stenting or bypass grafting prior to LVAD placement. Preoperative inotropic support should be also considered if the RV is marginal [8].

The presence of pulmonary hypertension should be assessed preoperatively. Severe fixed pulmonary pressures used to be a contraindication for LVAD placement, but emerging evidence suggests fixed pulmonary hypertension secondary to left heart failure can improve significantly in the first 6 months post-LVAD placement [9]. Regardless, inhaled nitric oxide (iNO) and prostacyclin vasodilators should be available.

Given the advanced heart failure in this population, atrial and ventricular arrhythmias are common and not contraindications to LVAD placement . The majority of patients will present with automatic implantable defibrillators (AICDs ) which will need to be deactivated in the operating room, and external defibrillation pads placed. All pacemakers should be interrogated prior to surgery for battery life and underlying heart rhythm. Pacer-dependent patients should be placed in asynchronous mode.

Potential intracardiac shunts and valvular pathology should be ruled out by echocardiography. A patent foramen ovale (PFO ) or other septal defect requires pre-LVAD implantation repair , as the transluminal pressure gradient post-LVAD predisposes a right-to-left shunt and intractable hypoxia. Similarly, moderate to severe aortic insufficiency (AI), moderate to severe mitral stenosis (MS), and severe tricuspid regurgitation (TR) are valvular lesions requiring repair prior to LVAD implantation.

Finally, the patient’s cardiac medications should be reviewed for potential anesthetic interactions. ACE inhibitors’ impact on afterload reduction, cardiac remodeling, and mortality in heart failure renders them a recommended medication for this patient population. However, their potential to blunt catecholamine response has been reported in the literature and may contribute to refractory vasoplegia. Withholding an ACE-I on the day of LVAD placement should be discussed.



Renal and Hepatic Function


Patients classified as NYHA III or IV experience a decrease in volume of distribution (VD) and reduced clearance of many intravenous medications by 50% or more [10]. Additionally, secondary renal and hepatic dysfunction are common in patients presenting for LVAD placement. The net result is that many common anesthetic drugs require dose adjustments. Both renal and hepatic end-organ functions can improve post-LVAD implantation, but their presence preoperatively are independently associated with worsened outcomes [1113]. Elevated bilirubin is the laboratory value most strongly associated with mortality, and primary liver disease should be ruled out prior to LVAD placement. Pre-existing coagulopathy or electrolyte/acid-base imbalances should be corrected .


Other


Patients should have a complete preoperative neurologic exam to rule out deficits, an anesthetic history evaluation (assessing for personal or family anesthetic complications), and an airway exam . Difficulty in ventilation or intubation can result in a host of cardiopulmonary complications as hypoxia- or hypercarbia-related pulmonary hypertension and can precipitate cardiovascular collapse.


Preoperative Laboratory Testing and Imaging


Preoperative labs consisting of an ECG, CXR, pulmonary function tests, complete metabolic panel (including LFTs), complete blood count, and coagulation profile, including fibrinogen and a functional coagulation assessment such as a TEG or ROTEM, should be ordered. Echocardiogram and cardiac catheterization should assess the transpulmonary gradient, pulmonary vascular resistance, pulmonary vascular response to vasodilators, right ventricular function, cardiac output, valvular function, and LV filling pressures. Imaging including head, chest, and abdominal CT scans should be negative for malignancy, terminal process, or hemorrhage. Patients should be typed and crossed, and blood products should be immediately available in the operating room .


Consent/Family Discussions


Despite their success in extending the quality and duration of life for a vast majority of patients, LVAD placement comes with the assumption of significant risk for not only mortality but also prolonged ICU stay, renal failure, progressive cardiac failure, and fatal hemorrhage. Patients and their families need to be aware of this during the informed consent process, and the discussion should address the patient’s wishes in the event of a catastrophic complication or decompensation. There is a high degree of family member confusion at the time of end of life for LVAD patients given the complexity and life-sustaining nature of these devices [14].



Monitors


Large-bore peripheral IV access is recommended in patients with prior sternotomy. If present, an AICD should be inactivated in the OR, and external defibrillation pads placed. An arterial line should be confirmed prior to induction. A PA catheter recommended and is useful to measure ventricular pressures, mixed venous saturation, and CVP/PCMP ratio. Unlike the LVAD flow reading which is estimated and does not include the native heart’s contribution, a PA catheter is also useful for cardiac output. Intraoperative TEE is useful for detecting factors that may affect VAD performance and patient outcome, including septal defects, aortic valve regurgitation, mitral stenosis, RV dysfunction, intracavitary thrombus, and aortic atheroma. Additionally, TEE is useful for confirming VAD cannulae positioning and cardiac de-airing .


Induction and Management Prior to Bypass



Induction and Preparation for Cardiopulmonary Bypass


End-stage cardiac failure patients presenting for LVAD implantation are often dependent on high circulating concentrations of catecholamines to maintain vasoconstriction. Acute decreases in LV preload or increases in LV afterload are poorly tolerated and should be avoided on anesthetic induction. Decreases in heart rate (HR) are especially deleterious, as these patients cannot compensate by increasing stroke volume [1]. Thus, these patients may benefit from low-dose norepinephrine or epinephrine infusion at the time of induction in order to maintain HR and CO .

Lidocaine and fentanyl are often given to blunt the sympathetic response to laryngoscopy. Etomidate is the most commonly used induction agent, but it comes with a risk of adrenal insufficiency. If this is a concern, ketamine can be used. Esmolol should be available to manage any tachycardia resulting from laryngoscopy. Increased time for circulation is required for onset of all intravenous medications, and intraoperative awareness is more frequent in patients undergoing cardiac surgery [15]. Maintaining cardiac output while restricting fluids to avoid unnecessary increases in RV end-diastolic pressure and maintaining adequate anesthetic depth are the pre-CBP goals.

Baseline labs including basic chemistry panel, arterial blood gas, and ACT should be obtained following induction. Hypokalemia and hyperglycemia should be addressed immediately. Antibiotics should be initiated at the time of skin prep (or earlier with vancomycin) and redosed accordingly during the procedure. Leukocyte-reduced blood should be available to reduce anti-HLA antibody production [16]. Replacement products for patients with an iatrogenic antithrombin III deficiency should be available.

Patients should be anticoagulated with heparin (300–400 units/kg) and an appropriate ACT (>350 s) confirmed with the surgeon and perfusionist prior to initiating CPB [17]. For patients with a suspected heparin resistance manifested by inappropriate ACT elevation, an additional dose of heparin may be administered. If this is unsuccessful, a presumed antithrombin III deficiency can be treated with antithrombin III concentrate or FFP if the former is unavailable. If the patient remains refractory to heparin or there is a contraindication to heparin, bivalirudin is the preferred substitute for use on CPB.


Intraoperative Transesophageal Echocardiography


The American Society of Echocardiography recommends a TEE checklist for both pre- and postimplantation (Table 7.2). TEE evaluation of the RV should begin with a qualitative assessment of size, tricuspid regurgitation (TR) severity, TR etiology (iatrogenic or secondary to dilated annulus), and ventricular motion from the tricuspid annulus to the apex, inclusive of the free wall [3, 18]. Systolic function and dilatation should be noted, as RV end-diastolic diameter was one of the two echocardiographic variables recently identified as independently predictive of RV failure [3, 19]. 3D volume assessment, tricuspid annular plane systolic excursion (TAPSE), global and regional RV fractional change area, and the maximum derivative of the RV pressure (dP/dt max) have also been mentioned as quantitative options for evaluating systolic function [3, 18]. However, these tools are not always available, and the techniques are challenging in this population [3]. At present there is no consensus on reliable predictors of RV failure following LVAD placement, but given the high morbidity and mortality associated with that event, thorough pre-bypass and postimplant examinations of both ventricles are imperative.


Table 7.2
Perioperative TEE protocol /checklist (Adapted with permission from [3])


















































Two-part exam

1. Preimplantation perioperative TEE exam

Goals: Confirm any preoperative echocardiography (TTE or TEE) findings; detect unexpected abnormal findings prior to LVAD implantation

Blood pressure: If hypotension is present, consider vasopressor agent to assess AR severity

LV: Size, systolic function, assess for thrombus

LA: Size, assess for LA appendage/LA thrombus

RV: Size, systolic function, catheters/leads

RA: Size, assess for thrombus, catheters/leads

Interatrial septum: Detailed 2D, color Doppler, IV saline contrast. Red flag: PFO/ASD

Systemic veins: Assess SVC, IVC

Pulmonary veins: Insepect

Aortic valve: red flags: >mild AR, prosthetic valve

Mitral valve: red flags: ≥moderate mitral stenosis, prosthetic mitral valve

Pulmonary valve: red flags: >mild PS, ≥moderate PR, if RVAD planned; prosthetic valve

Pulmonary trunk: red flags: Congenital anomaly (PDA, pulmonary atresia or aneurysm)

Tricuspid valve: TR, systolic PA pressure by TR velocity. Red flags: ≥moderate TR, >mild TS, prosthetic valve

Pericardium: Screen for effusion; consider constrictive physiology

Aorta: Root, ascending, transverse, and descending thoracic aorta; screen for aneurysm, congenital anomaly, dissection, or complex atheroma at each level

2. Postimplantation perioperative TEE exam

Goals: Monitor for intracardiac air; rule out shunt; confirm device and native heart function

Pump type and speed: Confirm

Blood pressure: Via arterial line; for hypotension (MAP of <60 mmHg), consider vasopressor agent before assessing AR severity and other hemodynamic variables

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Feb 24, 2018 | Posted by in CARDIOLOGY | Comments Off on Intraoperative Anesthesia Management
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