Table 4.
Gross Neurologic and Neuropsychometric Outcome Results - 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 |
| DIND (yes or no) | ||||||
| N | 199 | 242 | 0.108 | 1.78 | 1.08–2.95 | 0.025 |
| DIND=yes | 55 (28) | 51 (21) | ||||
| GOS at 3-months (1 vs. >1) | ||||||
| N | 199 | 242 | 0.059 | 0.70 | 0.45–1.10 | 0.123 |
| 1 (Minor or no disability) | 135 (68) | 143 (59) | ||||
| GOS at 3-months (1,2,3,4,5) | ||||||
| N | 199 | 242 | 0.043 | 0.67 | 0.44–1.03 | 0.065 |
| 1 (Minor or no disability) | 135 (68) | 143 (59) | ||||
| 2 (Moderate disability) | 40 (20) | 55 (23) | ||||
| 3 (Severe disability) | 12 (6) | 23 (10) | ||||
| 4 (Vegetative state) | 0 (0) | 0 (0) | ||||
| 5 (Death) | 12 (6) | 21 (9) | ||||
| Rankin Score at 3-months (0 or 1 vs. >1) | ||||||
| N | 199 | 242 | 0.078 | 0.74 | 0.47–1.16 | 0.192 |
| Score 0 or 1 (Mild or no neurologic disability) | 137 (69) | 147 (61) | ||||
| NIHSS at 3-months (0,1–7,8–14,>14, death) | ||||||
| N | 194 | 240 | 0.741 | 1.02 | 0.66–1.56 | 0.937 |
| 0 (No deficit) | 120 (62) | 149 (62) | ||||
| 1–7 (Mild deficit) | 57 (29) | 58 (24) | ||||
| 8–14 (Moderate deficit) | 3 (2) | 8 (3) | ||||
| 15–42 (Severe Deficit) | 2 (1) | 4 (2) | ||||
| Death | 12 (6) | 21 (9) | ||||
| Barthel's Index at 3-months (95–100,<95) | ||||||
| N | 198 | 242 | 0.076 | 0.69 | 0.38–1.25 | 0.22 |
| 95–100 | 170 (86) | 192 (79) | ||||
| <95 | 16 (8) | 29 (12) | ||||
| Death | 12 (6) | 21 (9) | ||||
| Impairment on neuropsychological composite score (yes or no) | ||||||
| N | 187 | 221 | 0.918 | 0.81 | 0.44–1.49 | 0.493 |
| Impairment=yes | 38 (20) | 44 (20) | ||||
| Impairment on at least 1 neuropsychological tests (yes or no) | ||||||
| N | 187 | 221 | 0.008 | 0.56 | 0.36–0.89 | 0.013 |
| Impairment=yes | 101 (54) | 148 (67) | ||||
Values in "No Nitrous Oxide Group" and "Nitrous Oxide Group" columns represent numbers of patients (% within group)
CI=Confidence Interval
DIND=Delayed Ischemic Neurologic Deficit
GOS=Glasgow Outcome Score
NIHSS=National Institutes of Health Stroke Scale
Statistical analysis of data for impairment on both the neuropsychological composite score and at least 1 neuropsychologic test include only surviving patients; patients who had died were not included in the denominator.
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.