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

Introduction  Controlling the partial pressure of carbon dioxide (PaCO ₂ ) 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 ₂ in this patient population is not known. Therefore, we investigated the variability in resting end-tidal PCO ₂ (P _ET CO ₂ ) in patients with intracranial steno-occlusive disease and the impact of revascularization on resting P _ET CO ₂ in these patients. Setting and Design  Tertiary care center, retrospective chart review Materials and   Methods We collected resting P _ET CO ₂ 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 _ET CO ₂ in a subset of patients. Results  Two hundred and twenty-seven patients were included [moyamoya vasculopathy ( n  = 98) and intracranial atherosclerotic disease ( n  = 129)]. In the whole cohort, mean ± standard deviation resting P _ET CO ₂ was 37.8 ± 3.9 mm Hg (range: 26-47). In patients with moyamoya vasculopathy and intracranial atherosclerotic disease, resting P _ET CO ₂ 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 _ET CO ₂ after revascularization in patients with low preoperative resting P _ET CO ₂ (<38 mm Hg) and decreasing resting P _ET CO ₂ after revascularization in patients with high preoperative resting P _ET CO ₂ (>38 mm Hg). Conclusion  This study demonstrates that resting P _ET CO ₂ in patients with intracranial steno-occlusive disease is highly variable. In some patients, there was a change in resting P _ET CO ₂ after a revascularization procedure.