Table 3.

Mixed effects model on postoperative opioid dose within 24 hours of surgery. Values are standardised estimates (95% confidence intervals) unless stated otherwise

Variables	Estimates	P value
Group allocation (intervention v control)	−2.26 (−3.7 to 0.8)	0.002
Surgery related pain levels (expected high v expected low)	1.90 (0.1 to 3.7)	0.04
Intraoperative opioid dose	1.91 (1.1 to 2.7)	<0.001
Intraoperative non-opioid dose	−0.46 (−1.3 to 0.4)	0.29
Intraoperative clonidine dose	0.36 (−0.4 to 1.1)	0.37
Random effects (study centre):
Within group variance	50.00
Between group variance	6.72
Intraclass correlation coefficient*	0.12

^*For comparison of fixed effects estimates, with variables normalised before model calculation.