Table 1.
Baseline Characteristics
| Nitrous Oxide Use | |||
|---|---|---|---|
| Yes | No | p-value | |
| N | 199 | 242 | |
| Demographics | |||
| Age (y) (mean ± SD) | 50 ± 11 | 52 ± 12 | 0.041a |
| Sex (% Female) | 126 (63) | 154 (64) | 1b |
| Race (% white not of hispanic origin) | 152 (76) | 206 (85) | 0.019b |
| Preoperative Medical History | |||
| History of diabetes mellitus (% with diabetes mellitus) | 7(4) | 5 (2) | 0.351b |
| History of hypertension (% with hypertension) | 82 (41) | 82 (34) | 0.113b |
| History of smoking (% current smokers) | 105 (53) | 142 (59) | 0.213b |
| Pre-operative Neurologic Status | |||
| Pre-operative WFNS Score: | 0.679b | ||
| GCS=15 and no motor deficit or aphasia | 138 (69) | 158 (65) | |
| GCS=13–14 and no motor deficit or aphasia | 52 (26) | 71 (29) | |
| GCS=13–14 with motor deficit or aphasia | 9 (5) | 13 (5) | |
| NIHSS Score at Baseline: | 0.035c | ||
| NIHSS=0 | 117 (59) | 120 (50) | |
| NIHSS=1–7 | 61 (31) | 101 (42) | |
| NIHSS=8–14 | 8 (4) | 5 (2) | |
| NIHSS=15–42 | 0 (0) | 1 (0) | |
| NIHSS missing | 13 (7) | 15 (6) | |
| Pre-operative Fisher Grade: | 0.01b | ||
| Fisher grade=1 | 15 (8) | 12 (5) | |
| Fisher grade=2 | 59 (30) | 77 (32) | |
| Fisher grade=3 | 105 (53) | 111 (46) | |
| Fisher grade=4 | 20 (10) | 42 (17) | |
| Interval between subarachnoid hemorrhage and induction of anesthesia (d) | 0.063a | ||
| Mean ± SD | 3.0 ± 3.0 | 3.5 ± 3.1 | |
| Median (Range) | 2 (0–14) | 2 (0–14) | |
Catagorical data expressed as n (% within group)
a
Based on Student's t-test
b
Based on Pearson chi-square test
c
Based on Fisher exact test
GCS=Glasgow Coma Score
NIHSS=National Institutes of Health Stroke Scale
SD=Standard Deviation
WFNS=World Federation of Neurological Surgeons