For general practitioners and many cardiologists, the specifics of surgical procedures may not be known. The ACC/AHA guidelines define high-risk procedures to include emergent major operations, aortic and major vascular surgery, peripheral vascular surgery, and anticipated prolonged procedures associated with large blood loss or fluid shifts [26]. For PH patients this list must be expanded to include procedures with risk for venous embolism (air, fat, cement), elevations in venous pressures (laparoscopy, Trendelenburg positioning), reduction in pulmonary vascular volume (lung compression or resection), perioperative systemic inflammatory response, and emergency procedures (Table 19.1). Again, effective communication between the PH specialist, surgeon and anesthesiologist can determine the risks and benefits of the proposed surgery or surgical technique. This will be revisited below.

A known history of PH will prompt an evaluation of functional status, cardiac function (especially RV function), pulmonary function and current severity of disease. Echocardiography and right heart catheterization are essential to make these assessments. Meyer et al. reviewed major risk factors as being, an elevated right atrial (RA) pressure, a 6 min walking distance <399 m at the last evaluation and need for emergency surgery [16]. The discerning physician must also identify patients with risk factors for PH who as yet may have gone undiagnosed such as patients with scleroderma spectrum of disease, obstructive sleep apnea, cardiac valvular lesions, depressed left ventricular function, heart failure with preserved ejection fraction (HFpEF) or interstitial lung disease (ILD). At a minimum, symptoms of pulmonary hypertension or RV failure should be elicited (shortness of breath, abnormal cardiac silhouette on chest radiograph, elevated jugular venous distension, etc.). Intermediate- or high-risk surgeries might prompt a screening echocardiogram.

Comorbidities such as coronary artery disease (CAD), chronic renal insufficiency, history of pulmonary embolism, NYHA functional class III/IV have been correlated with increased morbidity and mortality in cardiac surgery. Right ventricular impairment is also a predictor of worse outcome. Right axis deviation (RAD) (p = 0.02), RV hypertrophy (RVH) (p = 0.04), RV index of myocardial performance (RVMPI) ≥0.075 (p = 0.03), RV systolic pressure to systemic systolic blood pressure ratio ≥2/3 (p = 0.01) all predict increased postoperative mortality [14].

The preoperative evaluation of a patient with pulmonary hypertension should seek out indications of right ventricular dysfunction to determine areas for potential optimization or disqualification for surgery due to unacceptable risk. This section will review common preoperative testing modalities to highlight their utility in diagnosing right ventricular insufficiency.

Right heart catheterization (RHC) should be considered for PH patients undergoing intermediate- to high-risk operations or patients with moderate or severe PH by history, noninvasive screening, or with related comorbidities (e.g., obesity, sleep apnea, scleroderma, or risk factors for HFpEF such as atrial fibrillation and LAE). Left heart catheterization should also be performed in patients with coexisting left heart disease because of discrepancies between PCWP and left ventricular end-diastolic pressure (LVEDP) that could lead to misclassification of PH and have significant implications in treatment paradigms [34].

Ideally, RHC should be performed well in advance of surgery to allow for an adequate period of optimization for elective and semi-elective surgery. In all other cases, attempts should be made to lower PVR and enhance RV function prior to surgery. Routine vasoreactivity testing is performed during diagnostic RHC to determine candidates for vasodilator therapy [35, 36]. Although inhaled nitric oxide (iNO) is the drug of choice for testing due to lack of systemic effects and ease of administration, intravenous adenosine, epoprostenol, sildenafil, and inhaled iloprost can also be tried. Pre-capillary PH patients may benefit from advancing targeted pulmonary vasodilator therapy. When surgery cannot be delayed, phosphodiesterase 5 inhibitors (PDE5-I) such as sildenafil 20–40 mg three times daily, can provide acute vasodilatory effects and augmentation of right ventricular inotropy [37]. In those with high-risk hemodynamics (high right atrial pressure (RAP), low cardiac index (CI)), initiation of parenteral prostanoids should be considered prior to surgery. Furthermore, this same vasoactive testing is likewise useful in the perioperative period to guide intraoperative and postoperative management, such as the use of iNO, inhaled prostacyclins, and less commonly continuous epoprostenol. Patients with parenchymal lung disease and a component of hypoxic pulmonary vasoconstriction may also experience an improvement in PA pressures via an iNO mediated improvement in V/Q matching. Post-capillary PH patients may not benefit at all from pulmonary vasodilator therapy and moreover treatment may worsen pulmonary edema formation. In these patients, perioperative treatment should focus on diuresis and control of systemic hypertension. Some of the sickest WHO group 2 PH patients may need preoperative inodilators for low output states with aggressive up titration of the systemic vasodilators. WHO group 2 PH patients who have an increase in their PCWP in response to pulmonary vasodilators are at risk for developing worsening pulmonary vascular congestion and an increase in the driving force of left atrial hypertension with use of pulmonary vasodilators. Abnormal pulmonary function should be optimized with treatments such as oxygen, continuous positive airway pressure (CPAP), bronchodilators, antibiotics, and steroids where appropriate. Physical therapy and weight loss in obese patients may be beneficial although usually require a long-term plan [38, 39].

Optimal hemodynamic stability would include: mean arterial pressure (MAP) ≥ 60 mmHg, systolic BP ≥ 85 mmHg, oxygen saturation > 92 %, RAP < 12, mPAP < 35 (if feasible), PVR/SVR < 0.5 (if feasible), PCW 8–12 (some WHO 2 PH < 18), and CI ≥ 2.2 L/min/m².

Dyspnea at rest, syncope, hemodynamic findings of severe RV failure (low CI, high RAP >15 mmHg), metabolic acidosis, and marked hypoxemia are all signs of advanced, unstable disease and serious consideration should be given to cancelling or postponing the surgery until/unless improvement and stabilization or pulmonary hypertension can be achieved [37].

Preoperative coordination of care among the multidisciplinary team is crucial for best outcomes. Ideally, all patients except those with the lowest risk PH and lowest risk procedures should be operated on in a tertiary care center, where a multidisciplinary team of specialists experienced in managing patients with PH is available. The multidisciplinary team for preoperative management of PH patients includes anesthesiologist, cardiologists, intensivists and pulmonologists, surgeons, and experienced allied health-care members including respiratory therapists, pharmacy (availability of medications and a pharmacist with experience in administration of PH therapies), as well as nurse managers (systemic prostacyclin administration requires staff training and often is approved only in certain units). Meticulous advanced planning and discussion amongst team members must take place to transition from oral to IV/inhaled therapies where prolonged surgery/intubation/extended NPO periods are expected. Generally, chronic PAH therapies, including PDE5-I (sildenafil, tadalafil), endothelin receptor anatagonists (ERAs) (bosentan, ambrisentan, macitentan), and prostanoids (inhaled, intravenous, subcutaneous, oral) should be continued throughout the perioperative period, with appropriate substitutions as above when necessary (intravenous for oral PDE5-I, intravenous for subcutaneous prostacyclin infusion, etc., depending on the surgery and interference of subcutaneous site,). If inhaled prostacyclin analogues cannot be continued due to intubation appropriate substitution should be planned with iNO, intermittent nebulized prostacyclin, continuous inhaled epoprostenol, vs. occasional conversion to IV prostanoids (there are no significant bleeding complications with IV prostanoids, despite platelet inhibition) [37]. Oral therapies should be resumed as soon as possible after procedure, keeping in mind that compromised absorption can result in low drug levels and rebound PH. Coumadin can usually be discontinued with judicious decision regarding heparin bridging depending on risk/benefit of bleeding vs. clotting (such as hypercoagulable states, pulmonary embolism (PE), or mechanical valves). In high-risk situations (such as major orthopedic surgeries), retrievable preoperative IVC filter placement may be considered [40]. Careful perioperative deep venous thrombosis (DVT) prophylaxis should be instituted and early ambulation is essential for both DVT/PE prevention and avoiding deconditioning.

Meetings with the patient and family must take place preoperatively and include some discussion of modes of anesthesia, need for invasive monitoring, and their role during the recovery period.

Pulmonary vascular disease leads to an increase in RV afterload that impedes RV ejection and thereby leads to increased RV wall stress, RV diastolic overload, RV dilation, and in the more chronic state, RVH. In contrast to the LV, the thinner walled RV is subjected to greater wall tension for the same degree of increase in end diastolic volume; this leads to an increase in RV myocardial oxygen demand and consumption.

Although often described simply as PVR (the steady-state, mean pressure/mean flow relationship largely dictated by small vessels), the true interaction between the RV and the pulmonary circulation is pulsatile and dynamic. Accordingly, the concept of input impedance has been applied as a means to summarize the resistive, elastic, and reflective components of afterload, and provide for some discrimination between the relative contributions of small vessels (steady state resistance) and large elastic ones (“characteristic” impedance) [25]. However, assessment of input impedance requires simultaneous measurement of pressure and flow, and generally involves analysis in the “frequency domain,” i.e., mathematical resolution of pressure and flow waves into their individual frequency components and then defining their ratio at set frequencies along a spectrum. Not surprisingly, the complexity of both measuring and interpreting input impedance spectra has limited clinical utility. Nonetheless, there has been general acceptance of “lumped parameter” models such as the Windkessel to help conceptualize the static and dynamic contributions to afterload. Essentially adaptations of electrical circuits, these models incorporate a resistor (PVR), a capacitor (vascular compliance), and an inductor (characteristic impedance) to represent the basic physiological components dictating input impedance. While alternative methods for calculating characteristic impedance as a measure of large vessel load from more conventional “time-domain” measures (PA pressure, PA diameter, and stroke volume) have been described [41], from a clinical perspective, prognostic significance has focused more upon compliance (calculated as stroke volume/pulse pressure) and its reciprocal relationship with PVR [42–45]. Data suggest that early in the course of PAH, a relatively small rise in PVR will be accompanied by a larger relative decline in compliance, while later in the disease course, the fall in compliance elicited by increased PVR will diminish since the vascular wall approaches maximum stiffness [41]. Functionally, an acute change in compliance will lessen the ability of large elastic vessels to “absorb” pressure waves reflected from more distal potions of the circulation. This effect can be directly observed in the RV and proximal PA pressure waveform as the timing of peak pressure achievement moves from early to late in systole. This “late phase load” produced by summation of reflective pressure components parallels the systolic augmentation described for systemic vessels and contributes to a widened PA pulse pressure. This is particularly relevant to acute insults that may occur during surgery and affect RV pulsatile load, and importantly, may be underestimated by PA catheter tracings where pressure is measured more distal in the circulation. For example, compliance and PVR may be altered by events such as the addition of positive end-expiratory pressure (PEEP) to mechanical ventilation (Fig. 19.2), a change to prone or Trendelenburg positions, pneumoperitoneum during a laparoscopic procedure (Fig. 19.3), venous emboli (including air emboli or particulate matter, i.e., from orthopedic procedures), and any direct compression or displacement of the large PA branches.

Under normal circumstances the RV intramyocardial pressure is lower than the aortic root pressure and the RV coronary perfusion occurs throughout the cardiac cycle. In PH, due to the elevated RV intramyocardial pressure, coronary flow occurs predominantly during diastole, which further worsens the mismatch between oxygen demand and supply promoting RV ischemia and diminished RV contractility [46, 47]. Low RV oxygen supply is associated with a shift away from aerobic glucose and fatty acid oxidation to the less efficient RV glycolytic pathways [25].

Systemic vasodilatation and hypotension with anesthesia (see Sect. “Choice of Anesthetics”) leads to a relative increase in the PVR/SVR ratios, and hypotension induced RV ischemia in the setting of increased oxygen demands [48].

Intraoperative manipulation of the heart and/or great vessels may further contribute to the hypotension.

The combination of elevated PVR/reduced RV compliance and systemic hypotension may promote RV ischemia resulting in the “lethal combination” of RV dilatation, interventricular septal bulging into the left ventricle, and insufficient left ventricular filling, with resulting progressive decline in CO and further systemic hypotension [49]. Management should be focused on RV unloading with pulmonary vasodilators, optimizing intravascular fluid balance, and maintaining adequate systemic pressure. Combination of RV inotropes and systemic pressors may be needed [50]. Dobutamine may be a preferred RV inotrope in this situation due to less systemic vasodilation as compared to milrinone which may cause further LV unloading and septal displacement; vasopressin may be a good option to maintain systemic pressure although there is some institutional bias as well with the choice of systemic pressors and catecholamine sparing. Ongoing monitoring of arterial pressure, central venous pressure, cardiac output, central venous oxygen saturation, arterial blood gases, and lactate levels are necessary, ideally supplemented by transesophageal echocardiography (TEE) guided assessment of RV/LV filling.