Perioperative mortality in patients with portopulmonary hypertension undergoing liver transplantation.

T he perioperative mortality associated with liver transplantation is very low and is usually the result of a complication from an associated medical problem. One such medical condition is pulmonary hypertension, usually associated with portal hypertension. When liver transplantation is undertaken in a patient with portopulmonary hypertension, perioperative mortality appears to be related to the severity of the condition.1 The critical level of mean pulmonary artery pressure (MPAP), pulmonary vascular resistance (PVR), or transpulmonary gradient that would make liver transplantation inadvisable has long been debated by clinicians.1-11 The proper medical and anesthetic management of these patients is also controversial.12-15 The reason for these dilemmas is a paucity of robust data from which to define guidelines. The incidence of portopulmonary hypertension is reported to be as low as 8.5% for patients with end-stage liver disease.1 Therefore, the published information on outcome data is restricted to case reports or limited retrospective series. In this issue of Liver Transplantation, Krowka et al have critically analyzed the published data and, together with the Mayo Clinic experience, have established recommendations on the advisability of liver transplantation at different levels of portopulmonary hypertension. A patient presenting for transplantation with an MPAP .50 mm Hg presents a risk of mortality of 100% and, therefore, clearly should not undergo transplantation. A patient with an MPAP #35 mm Hg can safely proceed with liver transplantation without an increased risk of mortality. This will be good information for those who first make the diagnosis of pulmonary hypertension on the operating room table, at the time of induction of anesthesia for the transplant procedure. However, a dilemma remains when the MPAP is between 35 and 50 mm Hg. If these MPAP values are associated with a PVR of .250 dynes · s · cm25, then a mortality rate of 50% is noted. This finding emphasizes the need to properly assess the patient’s hemodynamic profile by measuring pulmonary capillary wedge pressure, so that an accurate PVR and transpulmonary gradient can be calculated. To meet the criteria for diagnosis as portopulmonary hypertension, the pulmonary capillary wedge pressure should be ,15 mm Hg. If a greater value is measured, then a primary cardiac etiology should be sought. Because PVR is flow determined, it is inversely related to cardiac output. However, when there is a fixed resistance to flow, MPAP will increase with an increase in cardiac output. Therefore, it is surprising that Krowka et al were unable to associate the level of cardiac output with mortality. At reperfusion of the liver graft, cardiac output typically increases by 5% to 10%. However, this increase is unpredictable and may reach 300% and precipitate right-heart failure in a ventricle that is already under strain. This increase in output is probably the result of the removal of the obstruction to portal blood flow by the extraction of the diseased liver, together with the systemic vasodilatation caused by the washout of acid metabolites and other vasodilator substances from the new graft. Why some patients have such a major increase in cardiac output is not known, but if this occurs it clearly adds to the risk for the patient with pulmonary hypertension. If such an acute increase occurs, inhaled nitric oxide may be administered to act on the pulmonary circulation without exacerbating the systemic vasodilatation.12 If this does not ameliorate the situation, a limited balloon atrial septostomy to reduce the strain on the right ventricle may be the only course of action left. All patients with severe liver cirrhosis may have some degree of cardiomyopathy.16 This may be concealed to the unsuspecting physician by the presence of the hyperdynamic circulation typically seen in this