Nadir Oxygen Delivery on Bypass and Hypotension Increase Acute Kidney Injury Risk After Cardiac Operations.
BACKGROUND
Acute kidney injury (AKI) continues to complicate cardiac operations. We sought to determine whether nadir oxygen delivery (DO2) on cardiopulmonary bypass (CPB) was a risk factor for AKI while also accounting for other postoperative factors.


METHODS
Using propensity scoring, we matched 85 patients who developed AKI after cardiac operations on CPB with 85 control patients who did not. We analyzed the following variables through midnight on postoperative day 1 (POD1): DO2, antibiotics, blood products and vasopressors (intraoperatively and postoperatively), and hemodynamic variables.


RESULTS
Univariable analysis revealed AKI patients had lower nadir DO2 on CPB (208 vs 230 mL O2/min/m(2) body surface area, p = 0.03), lower intensive care unit admission blood pressure gradient across the kidney (mean arterial pressure minus central venous pressure; 60 vs 68 mm Hg; p < 0.001), a greater proportion of patients with mean arterial pressure of less than 60 mm Hg for more than 15 minutes in the postoperative period (70% vs 42%, p < 0.001), a greater chance of having a cardiac index of less than 2.2 (74% vs 49%, p = 0.02), and greater total vasopressor use through the end of POD1 (5.2 vs 2.3 mg, p = 0.002). On multivariable analysis, predictors of AKI were a DO2 on CPB of less than 225 mL O2/min/m(2) (odds ratio, 2.46; 95% confidence interval, 1.21 to 5.03; p = 0.01) and postoperative mean arterial pressure of less than 60 mm Hg for more than 15 minutes (odds ratio, 3.96; 95% confidence interval, 1.92 to 8.20; p < 0.001). An average postoperative pressor dose greater than 0.03 μg/kg/min did not reach significance (odds ratio, 1.98; 95% confidence interval, 0.95 to 4.11; p = 0.07).


CONCLUSIONS
Postoperative hypotension on POD0 or POD1 and low DO2 on CPB both independently increase the AKI risk in cardiac surgical patients.
Division of Cardiac Surgery, Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland.
J Trent
JT
Magruder
Division of Cardiac Surgery, Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Samuel P
SP
Dungan
Division of Cardiac Surgery, Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Joshua C
JC
Grimm
Division of Cardiac Surgery, Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland.
H Lynn
HL
Harness
Division of Cardiac Surgery, Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Chad
C
Wierschke
Division of Cardiac Surgery, Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Stephen
S
Castillejo
Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Viachaslau
V
Barodka
Division of Cardiac Surgery, Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Nevin
N
Katz
Division of Cardiac Surgery, Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Ashish S
AS
Shah
Division of Cardiac Surgery, Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland. Electronic address: gwhitman@jhmi.edu.
Glenn J
GJ
Whitman
D058186:Acute Kidney Injury / Q000453:epidemiology / Q000209:etiology* / Q000378:metabolism; D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007022:Hypotension / Q000150:complications* / Q000378:metabolism; D015994:Incidence; D008297:Male; D008396:Maryland / Q000453:epidemiology; D008875:Middle Aged; D016017:Odds Ratio; D010100:Oxygen / Q000378:metabolism*; D011183:Postoperative Complications; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors
D010100:Oxygen