Variability of Resting Carbon Dioxide Tension in Patients with Intracranial Steno-occlusive Disease.

Controlling the partial pressure of carbon dioxide (PaCO ) is an important consideration in patients with intracranial steno-occlusive disease to avoid reductions in critical perfusion from vasoconstriction due to hypocapnia, or reductions in blood flow due to steal physiology during hypercapnia. However, the normal range for resting PCO in this patient population is not known. Therefore, we investigated the variability in resting end-tidal PCO (P CO ) in patients with intracranial steno-occlusive disease and the impact of revascularization on resting P CO in these patients.  Tertiary care center, retrospective chart review   We collected resting P CO values in adult patients with intracranial steno-occlusive disease who presented to our institution between January 2010 and June 2021. We also explored postrevascularization changes in resting P CO in a subset of patients.  Two hundred and twenty-seven patients were included [moyamoya vasculopathy (  = 98) and intracranial atherosclerotic disease (  = 129)]. In the whole cohort, mean ± standard deviation resting P CO was 37.8 ± 3.9 mm Hg (range: 26-47). In patients with moyamoya vasculopathy and intracranial atherosclerotic disease, resting P CO was 38.4 ± 3.6 mm Hg (range: 28-47) and 37.4 ± 4.1 mm Hg (range: 26-46), respectively. A trend was identified suggesting increasing resting P CO after revascularization in patients with low preoperative resting P CO (<38 mm Hg) and decreasing resting P CO after revascularization in patients with high preoperative resting P CO (>38 mm Hg).  This study demonstrates that resting P CO in patients with intracranial steno-occlusive disease is highly variable. In some patients, there was a change in resting P CO after a revascularization procedure.