A nurse is caring for a patient with severe TBI receiving mechanical ventilation, ICP is 28 mmHg, CPP (cerebral perfusion pressure) is 55 mmHg. The patient's PaCO, is 60 mmHg The PaCO2, level will likely cause:

A. Cerebral vasodilation and increased ICP is correct because PaCO2 is a potent regulator of cerebral blood flow (CBF). A PaCO2 of 60 mmHg indicates hypercapnia, which causes cerebral vasodilation, increasing blood volume in the brain and raising intracranial pressure (ICP). This effect can further compromise cerebral perfusion, especially when CPP is already low. B. Cerebral vasoconstriction and decreased ICP is incorrect because hypocapnia (low PaCO2), not hypercapnia, causes cerebral vasoconstriction, which temporarily reduces cerebral blood flow and ICP. C. No effect on ICP is incorrect because PaCO2 directly influences cerebral vessel tone. Changes in PaCO2 significantly affect ICP and are a key consideration in mechanically ventilated patients with traumatic brain injury.