Hypocapnia, ischemic lesions, and outcomes after intracerebral hemorrhage

Background: An association between spontaneous hyperventilation, delayed cerebral ischemia, and poor clinical outcomes has been reported in subarachnoid hemorrhage. We evaluated the relationship between early pCO₂ changes, ischemic lesions and outcomes in patients with intracerebral hemorrhage (ICH).

Methods: Consecutive patients with spontaneous ICH were enrolled in an observational cohort study conducted between 2006 and 2019. Patient characteristics and discharge outcome were prospectively recorded. Arterial blood gas (ABG) measurements and mechanical ventilation settings in the first 72 h of admission were retrospectively collected. MRI images were adjudicated for diffusion-restricted lesions consistent with ischemia and distant from the hematoma. We examined the associations between pCO₂ changes, ischemic lesions, and discharge outcomes by univariate and adjusted analyses.

Results: ABG data were available for 220 patients. Hyperventilation occurred in 52 (28%) cases and was not associated with clinical severity. Lower initial pCO₂ was associated with greater risk of in-hospital death (OR 0.94 per mmHg, 95%CI [0.89, 0.996], p = 0.042) after adjustment for ICH Score, pneumonia and mechanical ventilation requirements. MRI data were available for 33 patients. Lower pCO₂ was associated with a higher risk of ischemic lesions, except in patients with low initial systolic blood pressure (p < 0.05 for main and blood pressure interaction effects), after adjustment for other predictors.

Conclusions: In ICH patients with spontaneous ventilation, lower pCO₂ was independently associated with greater risk of in-hospital death. In patients with elevated initial blood pressure, who undergo blood pressure reduction per guideline recommendations, lower pCO₂ was associated with increased risk to develop ischemic lesions.

Keywords: Hyperventilation; Hypocapnia; Intracerebral hemorrhage; Outcomes.