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.
Background
Advanced glycation end products (AGEs) are potential biomarkers of biological age. Skin Auto Fluorescence (SAF) can assess AGEs non‐invasively. We evaluated the association of SAF levels with frailty and its predictive ability for adverse outcomes in older cardiac surgery patients.
Methods
This was a retrospective analysis of prospectively acquired data from a two‐center observational cohort study. We measured SAF level in cardiac surgery patients aged ≥70. Primary outcome was preoperative frailty. A comprehensive frailty assessment was performed before surgery based on 11 individual tests assessing the physical, mental, and social domain. Frailty was defined as at least 1 positive test in each domain. Secondary outcome measures were severe postoperative complications and a composite endpoint of 1‐year disability (defined by WHO Disability Assessment Schedule 2.0 (WHODAS 2.0) questionnaire) or mortality.
Results
Among 555 enrolled patients, 122 (22%) were frail. SAF level was most strongly associated with dependent living status (aRR 2.45 (95% CI 1.28–4.66)) and impaired cognition (aRR 1.61 (95% CI 1.10–2.34)). A decision algorithm to identify frail patients including SAF level, sex, prescription drugs, preoperative hemoglobin, and EuroSCORE II resulted in a C‐statistic of 0.72 (95% CI 0.67–0.77). SAF level was also associated with disability or death after 1 year (aRR 1.38 (95% CI 1.06–1.80)). The aRR for severe complications was 1.28 (95% CI 0.87–1.88).
Conclusions
Higher SAF level is associated with frailty in older cardiac surgery patients, as well as an increased risk of death or disability. This biomarker could potentially optimize preoperative risk stratification for cardiac surgery.
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