Table 2.
Cerebral physiologic data—Mann–Whitney U testing—ICP below 15 mmHg versus ICP above 20 mmHg
| Demographic variable | Mean ICP below 15 mmHg | Mean ICP above 20 mmHg |
Mann–Whitney
U p value |
||
|---|---|---|---|---|---|
| N = 157 | N = 28 | ||||
| Median | IQR | Median | IQR | ||
| ICP (mmHg) | 11.0 | 8.2–12.9 | 23.4 | 21.9–37.3 | <0.0001 |
| MAP (mmHg) | 82.0 | 76.2–87.5 | 89 | 80.2–96.8 | 0.0009 |
| CPP (mmHg) | 71.8 | 66.2–77.6 | 59.1 | 50.0–73.1 | <0.0001 |
| AMP (mmHg) | 1.9 | 1.4–2.7 | 3.5 | 2.2–5.6 | <0.0001 |
| PbtO2 (mmHg)* | 27.0 | 23.2–33.1 | 22.1 | 18.2–26.2 | 0.183 |
| PRx (a.u.) | − 0.002 | − 0.118 to 0.014 | 0.206 | − 0.009 to 0.582 | 0.0006 |
| PAx (a.u.) | − 0.090 | − 0.208 to 0.095 | 0.151 | − 0.090 to 0.376 | 0.0001 |
| RAC (a.u.) | − 0.384 | − 0.554 to − 0.176 | − 0.181 | − 0.382 to 0.145 | 0.003 |
| RAP (a.u.) | 0.731 | 0.560–0.837 | 0.710 | 0.485–0.783 | 0.290 |
| RAP AUC 0 | 2662.2 | 1908.0–3369.3 | 2194.0 | 1000.0–3198.9 | 0.047 |
| RAP AUC + 0.4 | 1305.6 | 716.4–1764.6 | 964.0 | 245–1565.8 | 0.052 |
| Total length of recording (h) | 119.7 | 80.5–161.6 | 114.1 | 57.1–167.7 | 0.333 |
| % Time above/below threshold | |||||
| Below CPP 60 mmHg | 7.3 | 2.2–26.3 | 57.2 | 12.4–75.4 | <0.0001 |
| Above CPP 70 mmHg | 53.0 | 30.6–81.2 | 12.7 | 3.5–55.5 | 0.0001 |
| Above PRx 0 | 47.8 | 22.6–64.3 | 72.4 | 47.1–90.2 | 0.0009 |
| Above PRx + 0.25 | 23.7 | 14.0–38.0 | 46.1 | 26.2–82.1 | 0.0003 |
| Above PRx + 0.35 | 17.0 | 9.7–28.0 | 36.4 | 18.3–77.9 | 0.0003 |
| Above PAx 0 | 39.6 | 25.6–59.9 | 66.4 | 41.4–79.6 | 0.0002 |
| Above PAx + 0.25 | 16.0 | 8.8–32.1 | 36.4 | 19.2–62.6 | <0.0001 |
| Above RAC − 0.10 | 20.9 | 9.2–40.4 | 39.4 | 18.1–75.1 | 0.003 |
| Above RAC − 0.05 | 17.6 | 7.8–35.4 | 35.3 | 15.9–71.2 | 0.002 |
| Below PbtO2 20 mmHg* | 16.5 | 1.7–35.1 | 30.7 | 19.3–54.3 | 0.229 |
| Mean hourly dose above/below threshold | |||||
| Above PRx 0 | 7.5 | 4.9–11.3 | 12.5 | 6.2–26.9 | 0.003 |
| Above PRx + 0.25 | 2.9 | 1.7–4.4 | 6.0 | 2.5–16.1 | 0.0006 |
| Above PRx + 0.35 | 1.8 | 1.1–2.9 | 4.1 | 1.6–12.3 | 0.0004 |
| Above PAx 0 | 5.0 | 2.9–9.5 | 10.3 | 5.9–17.3 | 0.0003 |
| Above PAx + 0.25 | 1.6 | 0.7–3.4 | 4.3 | 2.3–8.6 | <0.0001 |
| Above RAC − 0.10 | 2.6 | 1.1–5.4 | 5.8 | 2.1–15.8 | 0.001 |
| Above RAC − 0.05 | 2.0 | 0.8–4.0 | 4.9 | 1.8–13.7 | 0.0007 |
| Below PbtO2 20 mmHg* | 3.1 | 0.3–55.2 | 94.8 | 49.9–144.1 | 0.033 |
p values reaching statistical significance (<0.05) are bolded
a.u. = arbitrary units, AUC = integrated area under the RAP over time plot, AMP = pulse amplitude of ICP, CPP = cerebral perfusion pressure, ICP = intracranial pressure, IQR = interquartile range, MAP = mean arterial pressure, mmHg = millimeters of mercury, N = number of patients, PbtO2 = brain tissue oxygen, PAx = pulse amplitude index (correlation between AMP and CPP), PRx = pressure reactivity index (correlation between ICP and MAP), RAC = correlation between AMP and CPP
*Only 47 patients (41 in the ICP < 15 mmHg, and 6 in the > 20 mmHg cohorts) had PbtO2 monitoring