Preoperative Risk and the Association between Hypotension and Postoperative Acute Kidney Injury

Abstract

Background: Despite the significant healthcare impact of acute kidney injury, little is known regarding prevention. Single-center data have implicated hypotension in developing postoperative acute kidney injury. The generalizability of this finding and the interaction between hypotension and baseline patient disease burden remain unknown. The authors sought to determine whether the association between intraoperative hypotension and acute kidney injury varies by preoperative risk.

Methods: Major noncardiac surgical procedures performed on adult patients across eight hospitals between 2008 and 2015 were reviewed. Derivation and validation cohorts were used, and cases were stratified into preoperative risk quartiles based upon comorbidities and surgical procedure. After preoperative risk stratification, associations between intraoperative hypotension and acute kidney injury were analyzed. Hypotension was defined as the lowest mean arterial pressure range achieved for more than 10 min; ranges were defined as absolute (mmHg) or relative (percentage of decrease from baseline).

Results: Among 138,021 cases reviewed, 12,431 (9.0%) developed postoperative acute kidney injury. Major risk factors included anemia, estimated glomerular filtration rate, surgery type, American Society of Anesthesiologists Physical Status, and expected anesthesia duration. Using such factors and others for risk stratification, patients with low baseline risk demonstrated no associations between intraoperative hypotension and acute kidney injury. Patients with medium risk demonstrated associations between severe-range intraoperative hypotension (mean arterial pressure less than 50 mmHg) and acute kidney injury (adjusted odds ratio, 2.62; 95% CI, 1.65 to 4.16 in validation cohort). In patients with the highest risk, mild hypotension ranges (mean arterial pressure 55 to 59 mmHg) were associated with acute kidney injury (adjusted odds ratio, 1.34; 95% CI, 1.16 to 1.56). Compared with absolute hypotension, relative hypotension demonstrated weak associations with acute kidney injury not replicable in the validation cohort.

Conclusions: Adult patients undergoing noncardiac surgery demonstrate varying associations with distinct levels of hypotension when stratified by preoperative risk factors. Specific levels of absolute hypotension, but not relative hypotension, are an important independent risk factor for acute kidney injury.

Fig. 1.

Study inclusion/exclusion criteria.

Fig. 2.

Relationship between acute kidney injury (AKI) incidence and intraoperative hypotension (IOH), stratified by preoperative risk quartile. Quartiles with asterisks indicate statistically significant within-quartile differences among mean arterial pressure (MAP) ranges (P < 0.05). (A) and (B) represent compare absolute IOH ranges for each quartile in the derivation and validation cohorts, respectively; (C) and (D) compare relative IOH ranges for each quartile in the derivation and validation cohorts, respectively.

Fig. 3.

Adjusted risk of acute kidney injury (AKI) associated with intraoperative hypotension nadir greater than 10 min, by preoperative risk quartile. Regression within each quartile included all four blood pressure ranges and operative duration log transformed. Values presented as adjusted odds ratio and 95% confidence interval. *Patients were stratified by risk of postoperative AKI using the full-fit multivariable model. †Color scale used only for adjusted odds ratios demonstrating statistically significant associations. MAP, mean arterial pressure.