Table 4. Univariable and multivariable analyses of covariables associated with OWS.

Variables		Univariable analysis			Multivariable analysis
		HR	95% CI	P value	HR	95% CI	P value
Reason for mechanical ventilator application
	Respiratory disease	0.34	0.08–1.41	0.137
	Others	1.73	0.85–3.50	0.129
Comorbidity
	Respiratory disease	0.46	0.14–1.50	0.199
	Hematologic malignancy	1.60	0.77–3.33	0.207
History of opioid exposure		0.54	0.21–1.40	0.209
Alcoholism		1.74	0.72–4.21	0.213
Septic shock		2.14	1.10–4.17	0.025
Dialysis		1.65	0.79–3.45	0.177
Type of opioid
	Remifentanil vs. fentanyl	1.50	0.76–2.98	0.237	0.74	0.36–1.51	0.404
	Remifentanil vs. morphine	0.31	0.07–1.36	0.123	0.16	0.03–0.74	0.019
Sedative type
	No sedative	1.49	0.76–2.90	0.236
SOFA score		1.09	1.98–1.20	0.081
Duration of opioid infusion		0.58	0.47–0.73	< 0.001	0.56	0.45–0.71	< 0.001
Cumulative opioid dose		1.00	1.00–1.00	0.009
Withdrawal type
	De-escalation	0.77	0.40–1.47	0.431

OWS = opioid withdrawal syndrome, SOFA = Sequential Organ Failure Assessment, HR = hazard ratio, CI = confidence interval.