A comparative study of the effect of slow and rapid initiation of cardiopulmonary pump on tissue oxygenation index and ischemic complications

TL;DR

This study compares slow versus rapid initiation of heart-lung machine flow and finds no major differences in tissue oxygenation but a trend toward fewer delirium cases with slower initiation.

Contribution

The study introduces a novel comparison of slow versus rapid initiation of cardiopulmonary bypass flow and its impact on cerebral oxygenation and postoperative delirium.

Findings

No significant differences in tissue oxygenation index or hematocrit between slow and rapid initiation groups.

Rapid initiation was associated with lower arterial oxygen pressure and a higher trend in postoperative delirium.

Delirium incidence was not statistically significant but showed a trend favoring the slow initiation group.

Abstract

Introduction: Although the use of the heart-lung machine (HLM) is routine in cardiac operating theaters, there is still a lack of evidence-based guidelines concerning the optimal speed to reach full flow during initiation to reduce critical episodes of cerebral ischemia. Therefore, we have designed a study to compare two distinct initiation times for the commencement of cardiopulmonary bypass (CPB). Methods: We conducted a randomized, monocentric, double-blind, prospective study to assess the impact of two different CPB initiation speeds – rapid initiation at 30 s and slow initiation at 180 s – on cerebral tissue oxygenation (TOI via NIRS), arterial oxygen pressure, hematocrit (HCT) variation, and the incidence of postoperative delirium. The target flow rate was set at 2.4 L/min/m2, with adjustments made according to the patient’s body surface area. Results: The absolute values of the tissue oxygenation index (TOI) and HCT showed no differences between the study during the first 180 s following commencement of CPB. Patients in the fast group exhibited significantly lower arterial oxygen pressure at the initiation of the (P < 0.05). Additionally, patients in the fast group experienced a higher incidence of delirium in the second and third days following surgery. While clinically relevant, the elevated incidence of delirium fell short of being statistically significant, with post-operative days 2 and 3 having P-values of 0.06 and 0.08, respectively. Conclusion: The results of this study indicate that, despite the absence of a significant difference in TOI between the study groups, patients in the slow group exhibited a not statistically significant trend for a lower incidence of delirium, as defined by CAMICU-7, in comparison to those in the fast group.