Table 3

Results from univariable Cox regression of effects of specific variables on postoperative length of stay in a cohort of patients undergoing surgery for cSDH (n=530) pooled across m=40 imputed data sets

	HR	95% CI	P value
Demographics
Age (per year increase)	0.99	0.99 to 0.99	0.042*
Sex (male vs female)	1.20	0.99 to 1.45	0.053*
Referred patient	2.20	1.54 to 3.13	<0.001*
ASA 2 (all vs ASA 1)	0.50	0.31 to 0.82	0.006*
ASA 3	0.34	0.21 to 0.55	<0.001*
ASA 4	0.26	0.15 to 0.45	<0.001*
ASA 5	0.22	0.07 to 0.68	0.009*
mRS 1 (all vs mRS 0)	0.86	0.67 to 1.11	0.249
mRS 2	0.83	0.58 to 1.18	0.299
mRS 3	0.73	0.47 to 1.11	0.142
mRS 4	0.68	0.46 to 0.98	0.040*
Admission status
GCS 15 on admission (vs any other)	1.11	1.06 to 1.16	<0.001*
Admission ePOMS (per 1 domain increase)	0.91	0.87 to 0.97	0.002*
Cognitive impairment (yes/no)	0.57	0.48 to 0.69	<0.001*
Comorbidities
Airways disease	0.75	0.58 to 0.96	0.020*
CVS disease	0.83	0.70 to 0.99	0.040*
Heart failure	0.70	0.56 to 0.87	0.001*
Anticoagulated on admission	0.42	0.35 to 0.50	<0.001*
Creatinine (per 20 µmol/L increase)	0.96	0.92 to 0.99	0.022*
Day of surgery
Preoperative deterioration (yes/no)	1.07	0.89 to 1.28	0.488
Length of wait (per hour)	0.96	0.92 to 1.01	0.142
Time MAP <80 mm Hg (per 10 min increase)	0.99	0.97 to 1.02	0.720
Time ETCO₂ not 3–5 kPa (per 10 min increase)	0.98	0.92 to 1.05	0.616
Fentanyl dose (per 25 µg increase)	1.01	0.99 to 1.04	0.330
Volatile maintenance	0.99	0.84 to 1.18	0.964
Operative time (per 10 min increase)	0.97	0.95 to 0.99	0.004*
Postoperative
Complications (per 1 domain increase in ePOMS)	0.57	0.52 to 0.63	<0.001*

HRs >1 indicate a more rapid time to postoperative discharge.
*Indicate statistical significance at p<0.1, chosen threshold for inclusion in subsequent multivariable modelling. Postoperative complications included as a time-dependent covariate (by day).
ASA, American Society of Anesthesiologists Score; CVS, cardiovascular; ePOMS, Electronic Postoperative Morbidity Score; ETCO₂, end-tidal carbon dioxide measurement; GCS, Glasgow Coma Scale; MAP, mean arterial pressure; mRS, Modified Rankin Scale.