What are the recommended cardiopulmonary bypass (CPB) strategies for patients with impaired hepatic (liver) function?

Cardiopulmonary Bypass Strategies in Patients with Compromised Hepatic Function

In patients with compromised hepatic function undergoing cardiac surgery, optimize hemodynamics preoperatively by reducing right atrial pressures and pulmonary vascular resistance with vasodilators and ultrafiltration, maintain high CPB pump flow rates (≥2.4 L/min/m²), consider moderate hypothermia (28°C), correct coagulopathy with vitamin K supplementation, and aggressively manage nutritional deficits before surgery. 1

Preoperative Optimization Strategy

Hemodynamic Optimization

• Reduce hepatic congestion by decreasing right atrial pressures and pulmonary vascular resistance using vasodilators to improve preload and afterload 1
• Utilize ultrafiltration to relieve hepatic congestion from fluid overload 1
• Consider temporary mechanical support (IABP or temporary assist device) to improve forward cardiac output and alleviate hepatic venous congestion 1
• Obtain hepatology consultation with measurement of hepatic venous pressure and consideration of liver biopsy to evaluate the degree of hepatic fibrosis 1

Coagulation Management

• Correct vitamin K deficiencies with supplemental vitamin K before surgery, as hepatic dysfunction impairs synthesis of vitamin K-dependent clotting factors 1
• Anticipate increased transfusion requirements during the intraoperative and perioperative periods due to coagulopathy from liver disease and hepatic congestion 1
• Do not prophylactically correct INR with fresh frozen plasma based solely on laboratory values, as most patients with liver dysfunction have rebalanced hemostasis 1, 2, 3

Nutritional Optimization

• Aggressively manage hypoproteinemia (albumin <3.5 g/dL, total protein <6.0 g/dL) with dietary consultation and nutritional supplementation, as this impairs wound healing and increases infection risk 1
• Delay surgery if possible to allow nutritional repletion, as malnutrition is associated with higher sepsis rates and mortality 1

Intraoperative CPB Management

Pump Flow Rate Strategy

• Maintain high pump flow rates of 2.4 L/min/m² rather than 1.2 L/min/m², as hepatic blood flow is better preserved at higher flow rates 4
• Recognize that effective hepatic blood flow decreases by approximately 19% during CPB even under optimal conditions, which may be poorly tolerated in patients with pre-existing hepatic dysfunction 5

Temperature Management

• Consider moderate hypothermia (28°C) during CPB, as this increases portal venous flow and helps maintain total hepatic blood flow 4
• Avoid deep hypothermia (<28°C), as data on hepatic perfusion at these temperatures are limited 4

Perfusion Mode Considerations

• At low pump flow rates (1.2 L/min/m²), pulsatile perfusion better preserves total hepatic blood flow compared to nonpulsatile flow 4
• At high pump flow rates (2.4 L/min/m²) with hypothermia, the advantage of pulsatile perfusion is diminished, and either mode is acceptable 4

Central Venous Pressure Management

• Maintain low CVP (<5 cm H₂O) during hepatic manipulation or resection if applicable, as this reduces hepatic congestion and blood loss 1
• Monitor closely for adequate perfusion when using low CVP strategies, as excessive reduction can compromise hepatic arterial flow 1

Intraoperative Monitoring

Hemodynamic Monitoring

• Use pulmonary artery catheter monitoring in patients with significant hepatic dysfunction and associated portopulmonary hypertension to guide fluid and vasopressor management 1
• Monitor for right ventricular dysfunction, particularly in patients with portopulmonary hypertension, as positive pressure ventilation and increased afterload can precipitate RV failure 1

Fluid Management

• Utilize goal-directed fluid therapy targeting adequate cardiac output and end-organ perfusion rather than fixed CVP targets 1
• Consider stroke volume variation (SVV) monitoring instead of CVP to guide fluid administration, as SVV-guided therapy reduces intraoperative fluid volume without increasing complications 1
• Use balanced crystalloids (Ringer's lactate) for maintenance and colloids (human albumin) for volume expansion 1

Postoperative Management

Transfusion Strategy

• Maintain hemoglobin >7 g/dL in hemodynamically stable patients, with consideration of 8 g/dL threshold in those with cardiovascular disease or ongoing bleeding 3
• Transfuse single units and reassess after each transfusion to avoid overtransfusion, which increases mortality and complications 3
• Maintain platelet count >50,000/mm³ during invasive procedures 3
• Keep PT/aPTT <1.5 times normal only during active life-threatening hemorrhage, not prophylactically 3

Infection Prevention

• Administer empirical broad-spectrum antibiotics immediately if signs of sepsis or worsening encephalopathy develop, as bacterial infections occur in 60-80% of patients with acute liver failure 2
• Consider fungal coverage in patients with persistent fever despite antibacterial therapy, as fungal infections occur in one-third of patients with acute liver failure 2

Metabolic Monitoring

• Monitor blood glucose at least every 2 hours, as hypoglycemia is common in hepatic dysfunction and can mimic hepatic encephalopathy 2
• Provide stress ulcer prophylaxis given the high-risk nature of this population 2

Critical Pitfalls to Avoid

• Do not delay surgery for complete normalization of liver function tests if hemodynamic optimization has been achieved, as liver function may improve after restoration of adequate cardiac output 1
• Do not use high PEEP (>10 cm H₂O) postoperatively, as this can cause hepatic congestion and worsen liver function 1
• Do not assume coagulopathy requires prophylactic correction based solely on INR elevation, as this obscures disease progression monitoring and most patients have rebalanced hemostasis 1, 2, 3
• Do not overlook portopulmonary hypertension (mean PAP >35 mmHg), as this significantly increases perioperative risk and requires aggressive preoperative treatment 1
• Do not use benzodiazepines for sedation in patients with hepatic encephalopathy, as these worsen mental status 1

Special Considerations for Severe Hepatic Dysfunction

• Mean pulmonary artery pressure ≥45-50 mmHg represents an absolute contraindication to major cardiac surgery in most centers due to prohibitive mortality risk 1
• Patients with moderate portopulmonary hypertension (mean PAP 35-45 mmHg) require aggressive preoperative treatment with pulmonary vasodilators and close intraoperative monitoring with continuation of therapy throughout the perioperative period 1
• Consider extracorporeal membrane oxygenation (ECMO) availability for patients with severe portopulmonary hypertension who experience acute rises in PAP during surgery 1