Defining and characterizing severe hypoxemia after liver transplantation in hepatopulmonary syndrome

Abstract

Hepatopulmonary syndrome is defined as a triad of liver disease, intrapulmonary vascular dilatations, and abnormal gas exchange, and it carries a poor prognosis. Liver transplantation is the only known cure for this syndrome. Severe hypoxemia in the early postoperative period has been reported to be a major complication and often leads to death in this population, but it has been poorly characterized. We sought to propose an objective definition for this complication and to describe its risk factors, incidence, and outcomes. We performed a systematic literature search and reviewed our single-center experience to characterize this complication. On the basis of the most commonly applied definition in 27 identified studies, we objectively defined severe postoperative hypoxemia as hypoxemia requiring a 100% fraction of inhaled oxygen to maintain a saturation 85% and out of proportion to any concurrent lung process. Nineteen of the 27 reports (70%) fulfilled this definition, as did 4 of the 21 patients (19%) at our center. We determined the prevalence and mortality of this complication from reports including 10 or more consecutive patients and providing sufficient postoperative details to determine whether this complication had occurred. In these reports, the prevalence of this complication was 12% (25/209). For the 11 cases with reported outcomes, the posttransplant mortality rate was 45% (5/11). There was a trend toward an increased risk of developing this complication in patients with very severe preoperative hypoxemia, defined as a partial pressure of arterial oxygen 50 mm Hg (8/41 with very severe hypoxemia versus 3/49 without severe hypoxemia, P 5 0.053), and there was a significantly increased risk for patients with anatomic shunting 20% (7/25 with anatomic shunting 20% versus 1/25 without anatomic shunting 20%, P 5 0.049). In conclusion, increased preoperative vigilance for this common complication is required among high-risk patients, and further research is required to identify the best management strategies.

Proposed Management Algorithm for Severe Hypoxemia After Liver Transplantation in the Hepatopulmonary Syndrome

“…Using the existing definition of severe posttransplant hypoxemia in HPS (a need for 100% FiO 2 to maintain a saturation ≥85%) 10, we designated the threshold for triggering the algorithm as a saturation <85% despite 100% FiO 2 . We further required these conditions for at least one hour, and with a PEEP of ≥10 mmHg, corresponding to existing standards for use of ECLS in acute respiratory distress syndrome (ARDS) 16.…”

“…Where evidence was not available, we relied on common sense and our practical experience in using these strategies at our specialized HPS center, where reported mortality from this complication was 28.6%, versus 75% in other reports 10.…”

“…Although liver transplantation (LT) is curative in HPS, these patients have an elevated postoperative complication rate 6, 7, 8, 9. In particular, “severe posttransplant hypoxemia,” defined as a need for 100% inspired oxygen (FiO 2 ) to maintain a saturation of ≥85% (out of proportion to any other concurrent lung process) 10, has been identified as a major complication leading to prolonged ICU stay and death in this population 6, 9, 10, 11, 12. Although survivors have a complete normalization of gas exchange over time, severe posttransplant hypoxemia occurs in 6–21% of HPS patients, carries a mortality of 45%, and accounts for the majority of peri‐operative deaths in this population 10.…”

“…In particular, “severe posttransplant hypoxemia,” defined as a need for 100% inspired oxygen (FiO 2 ) to maintain a saturation of ≥85% (out of proportion to any other concurrent lung process) 10, has been identified as a major complication leading to prolonged ICU stay and death in this population 6, 9, 10, 11, 12. Although survivors have a complete normalization of gas exchange over time, severe posttransplant hypoxemia occurs in 6–21% of HPS patients, carries a mortality of 45%, and accounts for the majority of peri‐operative deaths in this population 10. A variety of strategies to attempt to manage this complication have been described in the literature, but these have never been reviewed and summarized and are used inconsistently, which has led to calls for a systematic approach 6, 9, 10, 13.…”

“…Although survivors have a complete normalization of gas exchange over time, severe posttransplant hypoxemia occurs in 6–21% of HPS patients, carries a mortality of 45%, and accounts for the majority of peri‐operative deaths in this population 10. A variety of strategies to attempt to manage this complication have been described in the literature, but these have never been reviewed and summarized and are used inconsistently, which has led to calls for a systematic approach 6, 9, 10, 13. We sought to review available evidence in order to develop a practical clinical management algorithm for severe posttransplant hypoxemia in HPS.…”