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

Purpose: Carbon dioxide (CO ₂ ) is a potent cerebral vasomotor agent. Despite reduction in CO ₂ levels (hypocapnia) being described in several acute diseases, there is no clear data on baseline CO ₂ values in acute stroke. The aim of the study was to systematically assess CO ₂ 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 CO ₂ (PaCO ₂ ) and end-tidal CO ₂ (EtCO ₂ ) 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 CO ₂ 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 CO ₂ assessment in the acute stroke setting. Further studies are required in order to evaluate the clinical impact of these findings.
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