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Abstract

Introduction: The development of new onset acute kidney injury (AKI) and its impact on outcomes in the subarachnoid hemorrhage (SAH) population has not been well described. This patient population in particular is exposed to unique risk factors including hyperosmolar compounds and potentially multiple angiographic contrast exposures. Specific aim: To study the incidence and risk factors for developing AKI (based on Acute Kidney Injury Network criteria) and its impact on outcomes in the SAH population admitted to a large academic neurocritical care unit. Methods: This is an IRB-approved, retrospective study of patients admitted to a tertiary academic neurologic intensive care unit between 2006–12. The patient cohort included adult (age>18Y) patients admitted following SAH (aneurysmal and non aneurysmal etiologies). Marginal comparisons between patients that developed AKI during the study period and those who did not were conducted using the Wilcoxon rank sum test for continuous variables, and the Pearson Chi-square test for categorical variables. The overall increase in the odds of mortality for patients who developed AKI was summarized using an odds ratio. A nonparametric bootstrap method was used to construct 95% confidence intervals for the odds ratio of mortality, and the overall incidence of AKI. Cox proportional hazards regression, with time-varying covariates, was used to conduct an adjusted analysis of specific risk factors The primary endpoint was the development of AKI following admission to the ICU, up to 14 days post bleed. The secondary end point was hospital mortality. Results: The final cohort of patients included 1253 adults admitted with a diagnosis of SAH, out of which 133 patients (11%) developed new onset AKI. Patients in the AKI cohort were older (median age was 60Y versus 57Y; p-value: 0.046) and had a significantly higher prevalence of Diabetes Mellitus (29% Vs 16 %; p-value: <0.001) and preexisiting kidney disease (p-value: <0.001). Interestingly, in spite of repeated contrast exposure, notable on day 1 and then peaking at day 10, we did not observe a significant effect of contrast exposure after adjusting for other risk factors for AKI. The hazard ratio (HR) for cumulative days of contrast exposure was 1.0 (95% CI: 0.8, 1.2). For each day of mechanical ventilation, the hazard of developing AKI was increased by 12% (HR: 1.12; 95% CI: 1.05, 1.19; p-value: <0.001). Preexisting kidney disease and Diabetes increased the hazard of AKI by a factor of 2.35 (95% CI: 1.31, 4.19; p-value: 0.004) and 1.80 (95% CI: 1.22, 2.66; p-value: 0.003), respectively. The cumulative number of days in which serum osmolality was measured was not significantly associated with the hazard of AKI, in these data. The AKI cohort had an increased length of ICU stay 14.4 ± 9.3 days versus 11.2 ± 8.5 days (p-value: <0.001). Patients who developed AKI had a 2.36 (95% CI: 1.51, 3.69) fold increased odds of death compared to the patients who did not develop AKI. Conclusions: Conclusion: Mechanical ventilation, preexisting kidney disease and DM were independent risk factors for AKI following SAH. AKI-SAH is associated with a significant increased length of stay and significant increased risk of hospital mortality.