How far can we go with positive end-expiratory pressure (PEEP) in liver transplant patients?

STUDY OBJECTIVE: To assess the effect of positive end-expiratory pressure (PEEP) up to 15 cm H(2)O on blood flow throughput of the liver and its effects on systemic hemodynamics in patients following liver transplantation. DESIGN: Prospective, interventional study. SETTING: Intensive care unit (ICU) of a university hospital. PATIENTS: 74 consecutive liver transplant recipients with a regular allocated cadaveric graft. INTERVENTION: The lungs of all study patients were postoperatively mechanically ventilated with biphasic positive airway pressure. Three different PEEP levels (5, 10, and 15 cm H(2)O) were randomly set within 4 hours of admission to the ICU. Systemic hemodynamic parameters were recorded using a pulmonary artery catheter and flow velocities were measured of the hepatic artery, portal vein, and right hepatic vein using a Doppler. MEASUREMENTS AND MAIN RESULTS: PEEP of 15 cm H(2)O induced a significant increase in central venous pressure and pulmonary capillary wedge pressure versus PEEP 5 cm H(2)O. Flow velocities of the right hepatic vein, portal vein, and hepatic artery were not influenced by PEEP. There also was no impact of increased PEEP on mean arterial pressure or cardiac index. CONCLUSION: PEEP up to 15 cm H(2)O does not impair liver outflow or systemic hemodynamics in liver transplant patients.