Time-dose response of oxygen delivery during cardiopulmonary bypass predicts acute kidney injury.

OBJECTIVE: Previous studies have reported that nadir oxygen delivery during cardiopulmonary bypass is associated with the occurrence of postoperative acute kidney injury (AKI). However, these measurements only considered the bottom point of the oxygen delivery (DO2) but did not consider the duration of DO2. We aimed to examine whether the time-dose response of DO2 during cardiopulmonary bypass can be used to estimate the risk for postoperative AKI. METHODS: We evaluated 112 patients who underwent cardiac surgeries with cardiopulmonary bypass. We analyzed the perfusion parameters recorded every 20 seconds. To obtain time-dose response of DO2 index (DO2i), the area under the curve was calculated as below the 300 mL/min/m2 threshold, which accounts for depth and duration of cumulative oxygen debt. In addition, the cumulative time below DO2i 300 mL/min/m2 was also calculated. Receiver operating characteristic analysis, univariate regression analysis, and multivariate regression analysis were used to evaluate associations between perioperative variables and postoperative AKI. RESULTS: Patients who developed AKI had larger area under the curve below the 300 mL/min/m2 threshold (1581 vs 632; P < .01) and cumulative time below DO2i 300 mL/min/m2 (34.7 vs 15.3 minutes; P < .01). Nadir DO2i was not significantly different between the non-AKI and AKI groups (263.4 vs 247.0 mL/min/m2; P = .291). CONCLUSIONS: The time-dose response of DO2i during cardiopulmonary bypass is a better indicator than nadir DO2i in evaluating AKI risk. Maintaining DO2i levels >300 mL/min/m2 may result in decreased risk for postoperative AKI.

Continuous renal replacement therapy with a polymethyl methacrylate membrane hemofilter suppresses inflammation in patients after open-heart surgery with cardiopulmonary bypass.

Cardiopulmonary bypass (CPB) induces a complex inflammatory response involving an increase in inflammatory cytokines, called postperfusion syndrome. Previous studies demonstrated that adsorption of the serum cytokines can reduce acute inflammation and improve clinical outcomes. In this study, patients were placed on continuous renal replacement therapy (CRRT) with a polymethyl methacrylate (PMMA) membrane hemofilter immediately after the start of an open-heart surgery with CPB and throughout the postoperative course to prevent postperfusion syndrome. The aim of this study was to assess whether continuous CRRT using a PMMA filter (PMMA-CRRT) could affect cytokine expression and improve perioperative outcomes. We designed a randomized controlled trial, which included 19 consecutive adult patients on maintenance dialysis and 7 consecutive adult patients who were not on maintenance dialysis (NHD group). Patients on maintenance dialysis were randomly divided into two groups: Ten patients who received CRRT with a polysulfone membrane hemofilter (PS group) and nine patients who received CRRT with a PMMA membrane (PMMA group). Blood samples were collected from the radial or brachial artery at five different time points. Comparisons between the PS, PMMA, and NHD groups revealed a significant main effect of time on changes in serum IL-6 and IL-8 concentrations (p < 0.01) and an interaction (p < 0.05) between time and group. Plasma IL-6 and IL-8 levels after surgery were significantly lower in the PMMA group than in the PS group, while other cytokines measured in this study were not significantly different. In addition, clinical outcomes were not significantly different between the groups. The continuous use of PMMA-CRRT throughout the perioperative period suppressed serum IL-6 and IL-8 concentrations, although there were no differences in clinical outcomes.