For a male client with suspected increased intracranial pressure (ICP), a most appropriate respiratory goal is to:
A. Prevent respiratory alkalosis.
B. Lower arterial pH.
C. Promote carbon dioxide elimination.
D. Maintain partial pressure of arterial oxygen (PaO2) above 80 mm Hg.
Correct Answer: C. Promote carbon dioxide elimination.
The goal of treatment is to prevent acidemia by eliminating carbon dioxide. That is because an acid environment in the brain causes cerebral vessels to dilate and therefore increases ICP. Hypercarbia lowers serum pH and can increase cerebral blood flow contributing to rising ICP, hence hyperventilation to lower pCO2 to around 30 mm Hg can be transiently used.
Option A: Cushing triad is a clinical syndrome consisting of hypertension, bradycardia and irregular respiration and is a sign of impending brain herniation. This occurs when the ICP is too high the elevation of blood pressure is a reflex mechanism to maintain CPP. High blood pressure causes reflex bradycardia and brain stem compromise affecting respiration.
Option B: Preventing respiratory alkalosis and lowering arterial pH may bring about acidosis, an undesirable condition in this case. Clinical suspicion for intracranial hypertension should be raised if a patient presents with the following signs and symptoms: headaches, vomiting, and altered mental status varying from drowsiness to coma.
Option D: It isn’t necessary to maintain a PaO2 as high as 80 mm Hg; 60 mm Hg will adequately oxygenate most clients. Cerebral autoregulation is the process by which cerebral blood flow varies to maintain adequate cerebral perfusion. When the MAP is elevated, vasoconstriction occurs to limit blood flow and maintain cerebral perfusion. However, if a patient is hypotensive, cerebral vasculature can dilate to increase blood flow and maintain CPP.
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