What are the risks and benefits of permissive hypercapnia?
Permissive hypercapnia can result in respiratory acidosis, which can be mitigated to some extent by increasing the respiratory rate and gradual renal buffering of the acidosis. Potentially harmful consequences of permissive hypercapnia include pulmonary vasoconstriction and pulmonary hypertension, proarrhythmic effects of increased discharge of the sympathetic nervous system, and cerebral vasodilation, yielding increased intracranial pressure.
However, experimental data have suggested that permissive hypercapnia is not only safe but also potentially beneficial. In most cases, hemodynamic characteristics actually improve, owing to the release of catecholamines.
Nonetheless, permissive hypercapnia should probably be used with caution in patients with heart disease and is relatively contraindicated in patients with elevated intracranial pressure.