Table 4.

Hierarchical linear model (random intercept model) for OPCAB LOS

Characteristics	Multiplier* (95% CI)		p Value
Patient characteristics
Intercept, days	18.0	(16.5 to 19.6)	<0.001
Preoperative LOS (days) (ref ≤3)
4–6	1.137	(1.109 to 1.166)	<0.001
7–9	1.284	(1.246 to 1.323)	<0.001
≥10	1.516	(1.462 to 1.572)	<0.001
Age (years) (ref <65)
65–74	1.038	(1.015 to 1.061)	0.001
≥75	1.093	(1.065 to 1.122)	<0.001
Sex (ref male)
Female	1.043	(1.017 to 1.070)	0.001
Smoking status (ref not smoking)
Smoking	0.978	(0.958 to 0.999)	0.040
Use of IABP (ref no)
Yes	1.039	(1.002 to 1.076)	0.041
Renal failure with dialysis	1.099	(1.056 to 1.143)	<0.001
Renal failure without dialysis	1.079	(1.032 to 1.131)	0.001
Diabetes, complicated	1.050	(1.020 to 1.083)	0.005
Diabetes, uncomplicated	1.031	(1.009 to 1.054)	0.005
Cardiac arrhythmias	1.051	(1.018 to 1.086)	0.003
Peptic ulcer disease excluding bleeding	0.971	(0.939 to 1.004)	0.082
Deficiency anaemia	0.934	(0.886 to 0.984)	0.012
Liver disease	1.071	(1.005 to 1.143)	0.034
Coagulopathy	1.112	(1.020 to 1.215)	0.016
Hypothyroidism	1.110	(0.997 to 1.237)	0.056
Hypertension, complicated	1.113	(0.966 to 1.289)	0.139
Duration of anaesthesia (hours) (ref ≤4)
6.5–8	1.026	(0.994 to 1.055)	0.107
≥8.5	1.071	(1.028 to 1.135)	0.001
Hospital characteristics
Teaching	1.075	(1.001 to 1.144)	0.046
Private not-for-profit ownership	1.013	(0.961 to 1.068)	0.622
Hospital index charge (ref 10:1)
7:1	1.044	(0.974 to 1.122)	0.225
Size (ref ≤449)
450–799	1.005	(0.950 to 1.067)	0.862
≥800	0.960	(0.881 to 1.055)	0.350
OPCAB hospital volume (ref ≤14)
15–29	0.947	(0.897 to 1.001)	0.053
30–59	0.988	(0.927 to 1.054)	0.719
≥60	0.824	(0.748 to 0.909)	<0.001

*Exponentiated parameter estimates from a log model.

IABP, intra-aortic balloon pumping; LOS, length of stay; OPCAB, off-pump coronary artery bypass grafting.