Table 4.
Clinical studies utilizing Pressure Reactivity Index (PRx) measurements in subarachnoid hemorrhage patients.
| References | Citation | Study size | SAH grade | Critical observations |
|---|---|---|---|---|
| Svedung Wettervik et al., 2021 | (46) | 242 | WFNS 1-5 | PRx was >0 in SAH patients and tended to increase at 3–4 days post-ictus in patients with unfavorable outcome (GOS-E 1-4 at 12 months). High PRx values independently associate with unfavorable outcome. |
| Howells et al., 2017 | (143) | 129 | Hunt-Hess 1-5 | 80/129 patients had an extraventricular drain opened during ICP/PRx measurements. An open drain did not corrupt ICP signal and conferred small, but significant improvements in PRx. |
| Gaasch et al., 2018 | (147) | 43 | Hunt-Hess 2-5 | PRx values are highest at day 0 post-ictus (0.31), decline and then rise at 4–10 days post-ictus. Patients with DCI and poor outcome (mRS 3-5 at 3 months) had higher PRx values compared to those without. High PRx values over 0–3 days post-ictus (0.21 vs. 0.08) associated with DCI and poor outcome. |
| Johnson et al., 2016 | (148) | 47 | Hunt-Hess 1-5 | Patients with PRx >1 had lower CBF than PRx ≤1 patients over 14 day assessment period. Dichotomized PRx groups did not associate with Hunt-Hess score or predict the development of DCI. |
| Eide et al., 2012 | (149) | 94 | Hunt-Hess 1-5 | PRx was higher (0.28) in patients who die (mRS 6), compared to mRS 0-2 (0.16) and mRS 3-5 (0.12) patients. PRx could not differentiate mRS 0-2 and mRS 3-5 patients. Amplitude correlation was a better predictor than PRx. |
| Bijlenga et al., 2012 | (150) | 42 | WFNS 4-5 | PRx at 0–2 days post-ictus was higher in patients who died within 3 months (0.10; 9/25) vs. survivors (−0.17; 16/25). PRx did not predict the development of vasospasm; PRx values were not significantly affected by vasospasm. |
| Barth et al., 2010 | (151) | 21 | Hunt-Hess 2-4 | PRx values were not statistically different between patients who developed infarcts (0.06; 8/21) vs. those who did not develop infarcts (0.10; 13/15). PRx did not correlate with ORx or FRx indies. |
These studies included SAH patients only. With the exception of Eide et al., all studies were retrospective. DCI, delayed cerebral ischemia; FRx, flow reactivity index; GOS-E, Glasgow outcome score-extended; ICP, intracranial pressure; mRS, Modified Rankin score; ORx, oxygen reactivity index; PRx, Pressure reactivity index; SAH, Subarachnoid hemorrhage; WFNS, World Federation of Neurosurgical Societies scale.