Hyperventilation can rapidly decrease ICP by causing vasoconstriction and reducing intracranial blood volume. Prolonged prophylactic hyperventilation was previously a mainstay of ICP management but has been found to worsen outcome, probably by inducing ischemia. Currently, it is recommended that hyperventilation should only be used for short periods and that PCO2 be kept above 30 mm Hg.
If the ICP is uncontrollable despite these measures, high-dose barbiturate therapy may be necessary. This suppresses metabolism and lessens cerebral blood-flow requirements. The patient must, however, be hemodynamically stable because barbiturates can have a direct cardiac depressant effect. Pentobarbital is the barbiturate most commonly used. A typical loading dose is 10 mg/kg over 30 minutes, followed by 5 mg/kg hourly for three doses, with a maintenance dose of 1 mg/kg/hr. Continuous electroencephalographic monitoring is necessary as the goal of therapy is to induce burst suppression.
Decompressive craniectomy (DC) has come to supplant barbiturates as the “final” treatment for intractable ICP elevations. Originally introduced in the 1960s, the procedure fell out of favor because, although mortality was lowered after severe TBI, the quality of survival was unchanged. The procedure involves removal of large portions of the skull in an attempt to control ICP. Over the past decade, numerous published articles on DC have used different ICP-based criteria for undergoing the procedure, such as ICP greater than 20 mm Hg for more than 30 minutes or ICP greater than 30 mm Hg for more than 20 minutes. Regardless of the criteria used, there is a direct correlation between the amount of bone removed and the ability to control ICP. There is a less than 40% reduction in ICP if bone removal is less than 8000 mm3 and greater than 80% reduction with removal of more than 12,000 mm3.
The DC may be unilateral or bilateral. When unilateral, bone is removed from the supraorbital ridge anteriorly to the inion posteriorly, superiorly to within 1 cm of the superior sagittal sinus and inferiorly to the floor of the temporal fossa. Bilateral DC is typically bifrontal from the supraorbital ridge to behind the coronal suture (including a generous subtemporal decompression), leaving a 1-cm strip of bone over the superior sagittal sinus. The bone is saved for later replacement either by implantation into an abdominal subcutaneous pocket or by freezing. It is typically replaced within 1 to 3 months. Some advocate replacement of the bone before hospital discharge to minimize the risk of infection, especially if the bone has been implanted, and other complications associated with DC. Greater than 20% of patients will develop symptomatic hydrocephalus or subdural hygromas after DC. This is related in part to the brain being exposed to atmospheric pressure once the ICP has normalized.
Although DC can be highly effective in controlling elevated ICP, it remains unclear whether it improves the quality of survival. A Cochrane meta-analysis of what little prospective, randomized data currently exist yielded 50% odds of unfavorable outcome after DC. The Decompressive Craniotomy (DECRA) Trial of DC was recently published, and in adults with diffuse TBI and uncontrollable intracranial hypertension, it found early bifrontal DC decreased intracranial pressure and intensive care unit (ICU) length of stay but was associated with more unfavorable outcomes.
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