Table 3.

Adjusted rates and relative risks of adverse outcomes, at hospitals participating in Keystone Surgery, and in the entire cohort, after Keystone Surgery implementation compared to before (values are percentage unless otherwise noted; CI: confidence interval)

Adverse Outcome	Hospitals Participating in Keystone Surgery			Entire Cohort
	Before enrollment in Keystone Surgery* N = 37,393	After enrollment in Keystone Surgery* N = 53,924	Relative Risk of adverse outcome after enrollment vs. before (95% CI)** N = 91,317	Relative Risk of adverse outcomes after enrollment vs. control hospitals (95% CI)*** N = 1,002,241
Mortality
Overall	4.66	4.51	0.97 (0.81, 1.13)	1.03 (0.97, 1.10)
General	5.38	5.17	0.95 (0.77, 1.12)	1.02 (0.95, 1.09)
Vascular	2.39	2.28	1.16 (0.87, 1.45)	1.10 (0.94, 1.26)
Complications
Overall	18.35	20.33	1.06 (0.99, 1.13)	1.03 (0.99, 1.07)
General	20.19	22.45	1.07 (1, 1.14)	1.03 (0.98, 1.07)
Vascular	12.52	13.23	0.99 (0.85, 1.13)	1.05 (0.98, 1.13)
Serious complications
Overall	8.79	9.05	1.02 (0.92, 1.12)	1.06 (1.01, 1.11)
General	9.56	9.83	1.03 (0.93, 1.13)	1.05 (0.99, 1.10)
Vascular	7.17	7.25	0.96 (0.74, 1.19)	1.10 (1.00, 1.19)
Reoperations
Overall	0.59	0.54	0.88 (0.34, 1.42)	0.89 (0.56, 1.22)
General	0.78	0.69	0.89 (0.32, 1.46)	0.89 (0.56, 1.21)
Vascular	0.15	0.13	0.75 (0.21, 2.43)	0.97 (0.09, 1.86)
Readmissions
Overall	13.10	13.34	1.03 (0.96, 1.11)	1.01 (0.97, 1.05)
General	13.57	13.81	1.01 (0.91, 1.1)	0.99 (0.95, 1.04)
Vascular	11.77	11.96	1.11 (0.98, 1.24)	1.04 (0.99, 1.09)

^*Adjusted for year of surgery.

^**Adjusted for year of surgery, patient characteristics, procedure type, and coexisting conditions.

^***The independent impact of Keystone Surgery was ascertained using a differences-in-differences analysis, which compared adverse outcomes after vs. before enrollment after controlling for trends towards improved outcomes in control hospitals. These models also adjusted for year of surgery, patient characteristics, procedure type, and coexisting conditions.