Table 3.

Postoperative Data - Nitrous Oxide Versus No Nitrous Oxide

			Univariate Analysis	Multivariate Analysis
Metric	Nitrous Oxide Group	No Nitrous Oxide Group	p-value	Odds Ratio	95% CI	p-value
Length of Intensive Care Unit Stay
N	199	242
≥ 5 days (%)	137 (69)	112 (46)	<0.001	3.04	1.93–4.79	<0.001
Hospital Duration (total days)
N	199	240
≥ 15 days hospital duration (%)	117 (59)	132 (55)	0.424	1.32	0.86–2.04	0.209
Discharge Destination
N	199	240
NOT discharged to home (%)	66 (33)	116 (48)	0.001	0.516	0.32–0.82	0.006

CI=Confidence Interval

Values in "No Nitrous Oxide Group" and "Nitrous Oxide Group" columns represent numbers of patients (% within group).

Discharge destination refers to the facility to which patients were sent upon discharge from the center where surgery was performed and included locations such as the patient's home, another acute care hospital, or chronic/rehabilitation facility.

Both unadjusted (univariate) and adjusted (multivariate) analyses were performed using standard logistic regression for binary outcomes and cumulative logistic regression for ordered categorical outcomes. For the multivariate analysis, the findings are summarized by presenting the odds ratio corresponding to the increased (or decreased) likelihood of the given outcome for patients receiving nitrous oxide compared to patients not receiving nitrous oxide. In all cases, the models are parameterized so that an odds ratio significantly greater than 1.0 would indicate an increased likelihood of a worse outcome in patients receiving nitrous oxide. The odds ratios are adjusted for treatment assignment (normothermia, hypothermia), age, gender, race (white versus other), baseline World Federation of Neurological Surgeons score, Fisher grade, baseline National Institutes of Health Stroke Scale (0, 1–7, 8–14, 15–42), aneurysm location (anterior, posterior), aneurysm size, history of hypertension, and time from subarachnoid hemorrhage to surgery.