Treatment for Increased ICP

It is critical that intracranial pressure be maintained at less than 20 to 25 mmHg. Above this value results in a significant increase in morbidity and mortality. Several strategies may be used to achieve this goal. All patients with severe TBI and evidence of increased ICP should have the head of the bed elevated to 30 degrees, adequate volume resuscitation to a MAP of 90 mmHg, and maintenance of adequate arterial oxygenation. After these steps several other treatment modalities may be used to lower intracranial hypertension.

Hyperventilation has been widely used to reduce ICP but it is no longer recommended as a prophylactic intervention. 6 Because of the extreme sensitivity of the cerebral vasculature to CO2 levels, hyperventilation leads to vasoconstriction that reduces ICP within 30 s. Unfortunately, hyperventilation and the resultant vasoconstriction can also cause cerebral ischemia. Hyperventilation should be reserved for head-injured patients with signs of increasing ICP (such as unilateral dilated pupil, motor posturing, and worsening mental status) despite other therapeutic measures (i.e., a last resort). If hyperventilation is used, it should be initiated as temporary measure and the Pco2 should be monitored closely and returned to the 30 to 35 mmHg range as soon as possible.6

Osmotic agents such as mannitol reduce ICP by osmotic diuresis with an onset within 30 min and lasting approximately 6 to 8 h. Mannitol has the additional benefit of expanding volume, initially reducing hypotension, and improving the blood's oxygen-carrying capacity. The recommended dose is 0.25 g/kg to 1 g/kg. There is no dose-dependent effect seen with mannitol; therefore, some authors advocate the lower range of the suggested dose. However, due to the diuresis, over time there will be a net intravascular volume loss, requiring hemodynamic monitoring. The Brain Trauma Foundation recommends that CSF drainage is preferable to mannitol. In the ED, where an IC catheter may not be readily available, mannitol may be used.

In addition to the above measures, monitoring of ICP should be performed for all patients with evidence of increased ICP, herniation, and a GCS score of less than 8. A ventricular catheter offers the best method to directly monitor ICP and thus calculate CPP. Under this setting, any rise in ICP above 20 to 25 mm HG may be reduced by CSF drainage. This treatment has the most favorable risk-to-benefit ratio. If CSF drainage is not effective in reducing ICP, then mannitol should be administered, assuming adequate MAP. Barbiturates have been shown to reduce cerebral metabolic rate. However, the use of barbiturate coma is rarely indicated in the emergency department as its effect occurs relatively late. The recommended dose of pentobarital is 10 mg/kg over 30 min. Steroids have no proven role in treating patients with TBI. Studies addressing this issue have not demonstrated improved outcome with their use.

EMERGENCY DECOMPRESSION When other methods to control the ICP have failed, patients with signs of herniation may need emergency decompression by trephination ("burr holes"). CT scanning before attempting trephination is recommended to localize the lesion and direct the decompression site. If CT scan is unavailable, or the patient is unstable for CT due to signs of rapidly progressive neurologic deterioration and herniation, then trephination should be considered.

As a final premorbid action for rapidly increasing intracranial pressure from traumatic hematoma expansion uncontrolled by medical therapy, emergency cranial surgical decompression may be attempted. If the cervical spine is stable, then optimally the patient's head is rotated so that the side with the dilated pupil is superior. The head should be stabilized and supported to prevent movement. A temporal burr hole should be attempted first by making a 4-cm vertical skin incision two finger-breadths anterior and three finger-breadths superior to the anterior tragus of the ear. When skull is reached, then a handheld drill should be inserted and drilled until the inner skull table is reached. A thin rim of bone should be left and scooped out under direct visualization with a curette.

If the temporal burr hole fails to yield blood or reverse signs of herniation then a frontal burr hole three finger-breadths from the midline and three finger-breadths from the hairline may be made. Should the second burr hole fail to improve the patient's condition, a final parietal burr hole can be placed four finger-breadths behind the frontal hole. Rarely, in cases with a high frontal injury, false lateralizing signs can occur due to Kernihan's notch. In these cases, the entire procedure should be repeated on the opposite side of the skull.

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