Prebypass Critical Closing Pressure Predicts Acute Kidney Injury After Cardiopulmonary Bypass

Objectives

Optimal blood pressure goals during cardiopulmonary bypass (CPB) remain uncertain and new metrics to individualize perfusion targets are needed. Critical closing pressure (Pcrit) is a fundamental property of the arterial circulation related to vascular tone and represents the outflow pressure impacting flow across the systemic circulation. We examined Pcrit as a prognostic marker of acute kidney injury (AKI).

Design

Retrospective cohort study.

Setting

Single tertiary care hospital

Participants

We included 1,038 adult cardiac surgery patients who underwent CPB.

Interventions

Pcrit was calculated using arterial waveform data before initiation of CPB. Pcrit was examined in relation to incidence of stage 2 or higher postoperative AKI according to standard Kidney Disease Improving Global Outcomes definitions.

Measurements and Main Results

Of the 1,038 patients included in the study, 50 (5%) experienced AKI. Patients who suffered AKI had significantly higher preoperative risk factors, including higher incidence of severe chronic kidney disease and higher Society of Thoracic Surgeons risk score (p < 0.01). They also had longer operative times and longer cross-clamp times (p < 0.01). All patients were maintained at similar mean arterial pressure while on CPB. Patients who suffered AKI had a significantly higher prebypass Pcrit than those who did not (49.0 mmHg vs 44.1 mmHg; p = 0.018). In a multivariate regression, Pcrit remained a significant predictor, representing a 16% increased risk of AKI for each 5 mmHg increase in prebypass Pcrit (p = 0.011).

Conclusions

A higher prebypass Pcrit is associated with a significantly higher incidence of postoperative AKI. Future study is warranted to investigate using intraoperative Pcrit to determine a personalized blood pressure goal during CPB.