Final answer:
The appropriate intervention for a client with ICP of 20 mm Hg is to administer low-dose barbiturate, which helps in reducing ICP by depressing cerebral metabolism.
Step-by-step explanation:
The appropriate nursing intervention for a client with an ICP (intracranial pressure) of 20 mm Hg is B. Administer low-dose barbiturate. This intervention can help reduce ICP through cerebral metabolic suppression. It's important to monitor the patient's neurological status and maintain adequate cerebral perfusion pressure (CPP) when using barbiturates. Options A, C, and D could potentially worsen the ICP. Warming blankets could increase metabolic demand and consequently ICP; hyperventilation could lead to excessive lowering of CO2 which may result in vasoconstriction and ischemia; and fluid restriction might not be helpful and could contribute to hypovolemia and decreased CPP.