Hypercapnia as a preventative therapeutic strategy: Unveiling the neuroprotective potential and mechanisms

• Explores induced therapeutic hypercapnia as a potential neuroprotective strategy. • Focuses on preventing delayed cerebral ischemia after subarachnoid hemorrhage (SAH). • Analyzes existing research on mechanisms, benefits, and limitations of hypercapnia. • Highlights potential benefits, including enhanced cerebral blood flow, reduced neuronal apoptosis, and improved ischemic tolerance. • Discusses findings from animal models and clinical trials on controlled hypercapnia's role in mitigating secondary brain injuries. Hypercapnia, an increase in carbon dioxide (CO2) in the bloodstream, has been historically considered purely a pathological condition. However, based on several publications evaluating the adverse outcome of certain conditions with an additional hypercapnia, It was discovered that hypercapnia can be also utilized as a therapeutic strategy. The most common of these strategies is permissive hypercapnia, which is described by inducing PaCO2 in inhalation while breathing under a mechanical ventilator in order to reduce secondary lung injuries. Subsequently, hypercapnia was also discovered as an effective anti-apoptotic and anti-ischemic agent while evaluated on neurons in vitro and rat models. As a result, hypercapnia has been utilized as an intervention in several clinical trials regarding different neurological conditions, most notably Sub-Arachnoid Hemorrhage. Mild levels of induced Hypercapnia is capable of preventing serious delayed vasospastic ischemic attacks and increases the overall cerebral blood flow which leads to significantly better outcomes in patients with severe acute neurological conditions. The anti-apoptotic and neuroprotective characteristics of CO2 suggest induced hypercapnia as a potential strategy for preventing more chronic neuropathological conditions. This article aims to review the publications surrounding the neuro-therapeutic effects of hypercapnia and discuss the advantages, drawbacks, and future of hypercapnia as an impactful strategy in preventing and treating neurological pathologies.