Management of Intracranial Hypertension
Section snippets
Normal values
In normal individuals with closed cranial fontanelles, the central nervous system contents, including the brain, spinal cord, blood, and cerebrospinal fluid (CSF), are encased in a noncompliant skull and vertebral canal, constituting a nearly incompressible system. The system has a small amount of capacitance provided by the intervertebral spaces. In the average adult, the skull encloses a total volume of 1475 mL, including 1300 mL of brain, 65 mL of CSF, and 110 mL of blood [1]. The
Causes of intracranial hypertension
The different causes of intracranial hypertension (Box 1) can occur individually or in various combinations. In primary causes of increased ICP, its normalization depends on rapidly addressing the underlying brain disorder. In the second group, intracranial hypertension is due to an extracranial or systemic process that is often remediable [9], [10], [11]. The last group comprises the causes of increased ICP after a neurosurgical procedure.
Intracranial hypertension secondary to traumatic brain injury
Special features should be considered in patients who
Neurologic intensive care monitoring
Intracranial hypertension is an important cause of secondary injury in patients who have acute neurologic and neurosurgical disorders and typically mandates specific monitoring. Patients who have suspected intracranial hypertension, especially secondary to TBI, should have monitoring of ICP; monitoring of cerebral oxygen extraction, as with jugular bulb oximetry or brain tissue Po2, may also be indicated. Brain-injured patients should also have close monitoring of systemic parameters, including
Intracranial pressure monitoring
Clinical symptoms of increased ICP, such as headache, nausea, and vomiting, are impossible to elicit in comatose patients. Papilledema is a reliable sign of intracranial hypertension, but is uncommon after head injury, even in patients who have documented elevated ICP. In a study of patients who had head trauma, 54% of patients had increased ICP, but only 3.5% had papilledema on fundoscopic examination [18]. Other signs, such as pupillary dilation and decerebrate posturing, can occur in the
Intracranial pressure treatment measures: brief summary of goals of therapy
The goals of ICP treatment may be summarized as follows:
- 1.
Maintain ICP at less than 20 to 25 mm Hg.
- 2.
Maintain CPP at greater than 60 mm Hg by maintaining adequate MAP.
- 3.
Avoid factors that aggravate or precipitate elevated ICP.
An overall approach to the management of intracranial hypertension is presented in Fig. 1.
General care to minimize intracranial hypertension
Prevention or treatment of factors that may aggravate or precipitate intracranial hypertension is a cornerstone of neurologic critical care. Specific factors that may aggravate intracranial hypertension include obstruction of venous return (head position, agitation), respiratory problems (airway obstruction, hypoxia, hypercapnia), fever, severe hypertension, hyponatremia, anemia, and seizures.
Measures for refractory intracranial hypertension
For patients who have sustained ICP elevations of greater than 20 to 25 mm Hg, additional measures are needed to control the ICP. Emergent surgical management should be considered whenever intracranial hypertension occurs suddenly or is refractory to medical management.
Heavy sedation and paralysis
Routine paralysis of patients who have neurosurgical disorders is not indicated; however, intracranial hypertension caused by agitation, posturing, or coughing can be prevented by sedation and nondepolarizing muscle relaxants that do not alter cerebrovascular resistance [45]. A commonly used regimen is morphine and lorazepam for analgesia/sedation and cisatracurium or vecuronium as a muscle relaxant, with the dose titrated by twitch response to stimulation. A disadvantage of this therapy is
Resection of mass lesions
Intracranial masses producing elevated ICP should be removed when possible. Acute epidural and subdural hematomas are a hyperacute surgical emergency, especially epidural hematoma because the bleeding is under arterial pressure. Brain abscess must be drained, and pneumocephalus must be evacuated if it is under sufficient tension to increase ICP. Surgical management of spontaneous intracerebral bleeding is controversial [77].
Cerebrospinal fluid drainage
CSF drainage lowers ICP immediately by reducing intracranial volume,
Summary
Effective treatment of intracranial hypertension involves meticulous avoidance of factors that precipitate or aggravate increased ICP. When ICP becomes elevated, it is important to rule out new mass lesions that should be surgically evacuated. Medical management of increased ICP should include sedation, drainage of CSF, and osmotherapy with either mannitol or hypertonic saline. For intracranial hypertension refractory to initial medical management, barbiturate coma, hypothermia, or
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This article was supported by National Institutes of Health grant P01-NS38660.
This is an updated version of an article that originally appeared in Critical Care Clinics, volume 22, issue 4.