Table 3.

Sensitivity Analysis on Primary Hypothesis

		Considered Potential Confounders for Adjustment
Model	Sample	Baseline	Estimated Blood Loss	Hypotension	Duration of Surgery	Urine Output	Transfusion	Vasopressor Use	Adjusted Odds Ratio (97.5% CI)	P Value∥
Primary model*	Matched patients		•	•	•	•			1.21 (1.06–1.38)	<0.001
Sensitivity analysis
Model included all patients†	All patients	•	•	•	•	•			1.26 (1.12–1.42)	<0.001
Model on patients matched  on all potential confounders‡	Matched patients								1.22 (1.07–1.40)	0.001
Treating transfusion as  potential confounders*	Matched patients		•	•	•	•	•		1.13 (0.99–1.29)	0.04
Treating vasopressor  use as potential confounders*	Matched patients		•	•	•	•		•	1.16 (1.02–1.32)	0.011
Treating transfusion and  vasopressor use as potential  confounders*	Matched patients		•	•	•	•	•	•	1.10 (0.96–1.25)	0.12
Treating as duration of surgery  as a mediator*§	Matched patients		•	•		•			1.35 (1.19–1.53	<0.001
Treating as intraoperative  hypotension as a mediator*§	Matched patients		•		•	•			1.28 (1.13–1.46)	<0.001
Treating as intraoperative  blood loss as a mediator*§	Matched patients			•	•	•			1.20 (1.06–1.37)	0.001

Explored models showed association between colloid use and increased odds of AKI (P < 0.025), except for the models when intraoperative blood transfusion was considered as a confounder.

^*Multivariable proportional odds model adjusts for marked intraoperative potential confounders among 29,360 matched patients. Matching was based on patient’s baseline characteristics listed in the table 1.

^†This multivariable regression model adjusts for baseline characteristics and intraoperative potential confounders among all 44,176 patients meeting inclusion and exclusion criteria. Matching was based on patients’ baseline characteristics listed in the table 1.

^‡This model based on 24,542 matched patients. Matching was based on patient baseline and intraoperative potential confounders (excluding transfusion and vasopressor) listed in the table 1.

^§Exploring the results if our assumptions regarding confounding were untrue. That is, the variable might be potential mediator and need to be excluded from the adjustment.

^∥A significance criterion is 0.025.

AKI = acute kidney injury.