Do acute stroke patients develop hypocapnia? A systematic review and meta-analysis

Abstract

Purpose: Carbon dioxide (CO₂) is a potent cerebral vasomotor agent. Despite reduction in CO₂ levels (hypocapnia) being described in several acute diseases, there is no clear data on baseline CO₂ values in acute stroke. The aim of the study was to systematically assess CO₂ levels in acute stroke.

Material and methods: Four online databases, Web of Science, MEDLINE, EMBASE and CENTRAL, were searched for articles that described either partial pressure of arterial CO₂ (PaCO₂) and end-tidal CO₂ (EtCO₂) in acute stroke.

Results: After screening, based on predefined inclusion and exclusion criteria, 20 studies were retained. There were 5 studies in intracerebral hemorrhage and 15 in ischemic stroke, totalling 660 stroke participants. Acute stroke was associated with a significant decrease in CO₂ levels compared to controls. Cerebral haemodynamic studies using transcranial Doppler ultrasonography demonstrated a significant reduction in cerebral blood flow velocities and cerebral autoregulation in acute stroke patients.

Conclusion: The evidence from this review suggests that acute stroke patients are significantly more likely than controls to be hypocapnic, supporting the value of routine CO₂ assessment in the acute stroke setting. Further studies are required in order to evaluate the clinical impact of these findings.

Keywords: Acute stroke; Carbon dioxide; Cerebral hemodynamics; Hypocapnia; Meta regression; Systematic review.