The role of cardiopulmonary bypass in lung transplantation

The risk-benefit for utilizing cardio-pulmonary bypass (CPB) in lung transplantation (LTx) remains debatable. This study compares outcomes after LTx utilizing different CPB strategies - elective CPB vs. off-pump vs. off-pump with unplanned conversion to CPB.

A total of 302 LTx performed over seven yr were divided into three groups: "off-pump" group (n = 86), "elective on-pump" group (n = 162), and "conversion" group (n = 54). The preoperative donor and recipient demographics and baseline characteristics and the postoperative outcomes were analyzed; 1:1 propensity score matching was used to identify patients operated upon using elective CPB who had risk profiles similar to those operated upon off-pump (propensity-matching 1) as well as those emergently converted from off-pump to CPB (propensity-matching 2).

Preoperative group demographic characteristics were comparable; however, the "off-pump" patient group was significantly older. The "conversion" group had a significantly greater number of patients with primary pulmonary hypertension, pulmonary fibrosis, preoperative mechanical ventilation, and preoperative extracorporeal life support (ECLS). Postoperatively, patients from the "conversion" group had significantly poorer PaO2 /FiO2 ratios upon arrival in intensive care unit (ICU) and at 24, 48, and 72 h postoperatively, and they required more prolonged ventilation, longer ICU admission, and they experienced an increased need for ECLS than the other groups. Overall, cumulative survival at one, two, and three yr was significantly worse in patients from the "conversion" group compared to the "off-pump" and "elective on-pump" groups - 61.9% vs. 94.4% vs. 86.9%, 54.4% vs. 90.6% vs. 79.5% and 39.8% vs. 78.1% vs. 74.3%, respectively (p < 0.001). The "off-pump" group had significantly better PaO2 /FiO2 ratios, and a significantly shorter duration of ventilation, ICU stay, and hospital length of stay when compared to the propensity-matched "elective on-pump" group. There were no statistically significant differences in postoperative outcomes and overall survival between the "converted" group and the propensity-matched "elective on-pump" group.

Despite segregation of unplanned CPB conversion cases from elective on-pump cases, patients with comparable preoperative demographic/risk profiles demonstrated better early postoperative outcomes and, possibly, an improved early survival with an off-pump strategy. A considerable proportion of high-risk patients require intraoperative conversion from off-pump to CPB, and this seems associated with suboptimal outcomes; however, there is no significant benefit to employing an elective on-pump strategy over emergent conversion in the high-risk group.