Table 4. Univariate analysis of postoperative nausea and vomiting by intra-operative and postoperative factors.

	No. of patients (%)	PONV No. (%)	P-value	Crude OR (95% CI)
Duration of anesthesia (h)			< 0.001*
< 2	73 (19.6)	7 (9.6)		1
2–4	198 (53.2)	44 (22.2)		2.69 (1.15, 6,29)
> 4	101 (27.2)	43 (42.6)		6.99 (2.92, 16.74)
NG tube insertion			0.002*
No	252 (67.7)	52 (20.6)		1
Yes, no retention	73 (19.6)	30 (41.1)		2.68 (1.54, 4.68)
Yes, with retention	47 (12.6)	12 (25.5)		1.32 (0.64, 2.72)
Blood loss (mL)			< 0.001*
≤ 100	200 (53.7)	37 (18.5)		1
101–499	91 (24.5)	23 (25.3)		1.49 (0.82, 2.69)
≥ 500	81 (21.8)	34 (42.0)		3.19 (1.81, 5.62)
Postoperative opioid			0.094*
No	320 (86.1)	76 (23.8)		1
Yes	52 (13.9)	18 (34.6)		1.70 (0.91, 3.18)

PONV: Postoperative nausea vomiting