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Table 1 Characteristics and blood gas changes in 98 patients undergoing apnea test

From: The effect of incorporating an arterial pH target during apnea test for brain death determination

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
  1. 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
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