Table 1.
Characteristics and blood gas changes in 98 patients undergoing apnea test
| Variable | All patients (n = 98) | Positive AT (n = 89) | Inconclusive AT (n = 9) | P value |
|---|---|---|---|---|
| Age (years), mean (±SD) | 50 (± 16) | 50 (± 16) | 52 (± 18) | 0.80 |
| Female, n (%) | 54 (55) | 47 (53) | 7 (89) | 0.18 |
| Primary etiology of BD, n (%) | ||||
| HIBI | 41 (42) | 35 (40) | 6 (67) | 0.31 |
| Nontraumatic ICH | 29 (30) | 29 (33) | 1 (11) | 0.26 |
| HIBI + Nontraumatic ICH | 3 (3) | 3 (3) | 0 | 1 |
| AIS | 11 (11) | 9 (10) | 2 (22) | 0.27 |
| TBI | 9 (9) | 9 (10) | 0 | 1 |
| Other cerebral edema | 5 (5) | 4 (4) | 1 (11) | 0.39 |
| Malignancy | 0 | 2 | 0 | |
| Status epilepticus | 0 | 1 | 0 | |
| Lupus cerebritis | 0 | 0 | 1 | |
| Hemodialysis | 0 | 1 | 0 | |
| Duration between clinical exams (hours), mean (±SD) | 7 (± 9) | 6 (± 9) | 18 (± 11) | 0.03 |
| Mean BP at the beginning of AT (mm Hg), mean (±SD) | ||||
| SBP | 127 (± 28) | 128 (± 28) | 113 (± 31) | 0.49 |
| DBP | 72 (± 16) | 73 (± 16) | 65 (± 17) | 0.50 |
| MAP | 90 ± 18 | 91 (± 18) | 81 (± 21) | 0.50 |
| Temperature (°C), mean (±SD) | 36.9 ± 0.6 | 36.9 (± 0.7) | 36.9 (± 0.3) | 0.79 |
| Vasopressor support, n (%) | 78 (80) | 71 (80) | 7 (78) | 1 |
| Pre-AT blood gas (mm Hg), mean (±SD) | ||||
| pH | 7.38 ± 0.06 | 7.38 ± 0.06 | 7.37 ± 0.04 | 0.66 |
| PaO2 | 242 ± 130 | 246 ± 130 | 187 ± 127 | 0.37 |
| PaCO2 | 39 ± 5 | 39 ± 5 | 37 ± 5 | 0.37 |
| Post-AT blood gas (mm Hg), mean (±SD) | ||||
| pH | 7.17 ± 0.07 | 7.17 ± 0.07 | 7.24 ± 0.04 | 0.01 |
| PaO2 | 234 ± 125 | 145 ± 120 | 47 ± 17 | < 0.01 |
| PaCO2 | 72 ± 13 | 73 ± 12 | 55 ± 9 | 0.01 |
| Reasons for inconclusive test, n (%) | ||||
| Inadequate CO2 rise | 4 (4) | NA | 4 (44) | |
| Inability to complete the test due to complication | 4 (4) | NA | 4 (44) | |
| Unclear | 1 (1) | NA | 1 (11) | |
| Ancillary studies, total n (%) | 49 | 38 | 11 | < 0.01 |
| TCD | 18 (37) | 16 (42) | 2 (18) | 0.18 |
| SPECT | 14 (29) | 11 (29) | 3 (27) | 1 |
| EEG | 15 (30) | 10 (26) | 5 (45) | 0.28 |
| CTA | 2 (4) | 1 (3) | 1 (9) | 0.40 |
AT apnea test, SD standard deviation, BD brain death, HIBI hypoxic ischemic brain injury, ICH intracranial hemorrhage, AIS acute ischemic stroke, TBI traumatic brain injury, BP blood pressure, SBP systolic blood pressure, DBP diastolic blood pressure, MAP mean arterial pressure, PaO2 partial pressure of arterial O2, PaCO2 partial pressure of arterial CO2, TCD transcranial Doppler, SPECT single photon emission computed tomography, EEG electroencephalogram, CTA computed tomography angiography