Critical oxygen delivery threshold during cardiopulmonary bypass in older cardiac surgery patients with increased frailty risk.

Open in new tab Download slide Open in new tab Download slide OBJECTIVES Older patients have a higher cardiac surgery-associated acute kidney injury (CSA-AKI) related mortality. Low oxygen delivery (DO₂) during cardiopulmonary bypass (CPB) is a risk factor for CSA-AKI, but critical DO₂ thresholds for older patients are unknown. This study investigated critical DO₂ thresholds for CSA-AKI in patients ≥70 years undergoing on-pump cardiac surgery. METHODS Patients were enrolled from July 2015 until August 2017. CPB data from 432 patients were collected, and DO₂ values were calculated per minute. The primary outcome was CSA-AKI. The association between DO₂ and CSA-AKI was analysed with multivariable regression analysis. Multiple DO₂ thresholds were analysed. The association between CSA-AKI and the area below the DO₂ thresholds (DO₂ deficit) was evaluated, as was the association between frailty and CSA-AKI. RESULTS CSA-AKI occurred in 63 (14.6%) patients. Mean and nadir (lowest) DO₂ values were lower in patients with CSA-AKI (283 vs 312 ml/min/m²; P -value <0.001 and 238 vs 270 ml/min/m²; P -value <0.001, respectively). The adjusted relative risk for CSA-AKI was 1.006 [99% confidence interval (CI) 1.001–1.012] per ml/min/m² nadir DO₂ decrease. The critical DO₂ threshold was 270 ml/min/m² [adjusted relative risk 2.06 (99% CI 1.33–2.80)]. The DO₂ deficit below 270 ml/min/m² was associated with CSA-AKI [adjusted relative risk 2.84 (99% CI 1.87–3.81)]. No association between frailty and CSA-AKI was found (P  = 0.82). CONCLUSIONS Low DO₂ increased the risk for CSA-AKI in older patients who had cardiac surgery. A critical DO₂ threshold of 270 ml/min/m² was applicable for frail and non-frail patients. The efficacy of a DO₂ >270 ml/min/m² to reduce CSA-AKI in older patients needs further evaluation. [ABSTRACT FROM AUTHOR]