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Basics

Christopher R. Newey, DO


BASICS

DESCRIPTION

The Monroe–Kelli doctrine states that the cranium is a fixed volume composed of CSF, blood, and brain tissue and that an increase in any of these must be offset by an appropriate decrease in another content. If there is not an appropriate offset, the intracranial pressure (ICP) will increase. Intracranial compliance (i.e., change in volume divided by change in ICP) decreases with increased ICP. This can affect cerebral blood flow by affecting cerebral perfusion pressure (CPP) [i.e., mean arterial pressure (MAP) minus ICP], which ultimately can cause neurological deficits. Normal ICP ranges from 5 to 15 mm Hg. Normal CPP is >50 mm Hg.

EPIDEMIOLOGY

Incidence

The epidemiology varies depending on the underlying etiology.

RISK FACTORS

The risk factors comprise stroke, head injury, intracranial tumor (primary or secondary), CNS infection, and eclampsia.

GENERAL PREVENTION

Avoiding precipitating event, serially monitoring known intracranial lesions.

PATHOPHYSIOLOGY

As mentioned, the Monroe–Kelli doctrine describes the maintenance of normal ICP where if one intracranial constituent increases, another must decrease. Cerebral autoregulation is the natural attempt to maintain cerebral blood flow adequate for metabolic demands of the brain. As ICP increases, the autoregulation curve is disrupted causing a linear increase in cerebral blood pressure with increasing MAP. Once compliance limit has been reached (i.e., an ICP of approximately 20 mm Hg), parenchyma becomes displaced resulting in various herniation syndromes.

ETIOLOGY

COMMONLY ASSOCIATED CONDITIONS

Commonly associated conditions depend on the underlying etiology: Pregnancy, liver/kidney failure, malignancy, cardiovascular disease, and hypercoagulable state.

Diagnosis

DIAGNOSIS

HISTORY

Patients may give a history of headache (especially positional with recumbency), nausea/vomiting (especially projectile), blurry vision, difficulty walking, diplopia, weakness, altered mental status, prior cancer, and hematological disorder.

PHYSICAL EXAM

DIAGNOSTIC TESTS AND INTERPRETATION

Lab

Initial Lab Tests

Complete blood counts, coagulation profile including PT/INR and PTT, and type and screen should be ordered in preparation for possible surgical or medical (e.g., FFP) intervention. Metabolic profile. Check serum osmolarity.

Follow-Up & Special Considerations

Daily labs, including blood counts, metabolic profiles, and coagulation panels.

Imaging

Initial Approach

Follow-Up & Special Considerations

Serial CT heads are indicated to monitor for increasing or decreasing mass effect.

Diagnostic Procedures/Other

Pathological Findings

DIFFERENTIAL DIAGNOSIS

Treatment

TREATMENT

MEDICATION

First Line

ADDITIONAL TREATMENT

General Measures

Additional Therapies

COMPLEMENTARY AND ALTERNATIVE THERAPIES

Pain/agitation control as needed with narcotics, sedatives, seizure prophylaxis, control nausea, and vomiting.

SURGERY/OTHER PROCEDURES

Early neurosurgical consultation is necessary in cases of increased ICP. Mortality with medical management alone 50–80%. Surgical decompression (i.e., frontotemporoparietal bone hemicraniectomy) may be an option for malignant cerebral edema in select patients with large infarcts. Patients are selected on the basis of age, timing of surgery, and neuroimaging findings. Flap should be 12 cm in diameter and also includes duraplasty. Additionally, debulking surgery may be an option for tumors. Consider placement of pressure monitoring devices and CSF drainage.

IN-PATIENT CONSIDERATIONS

Admission Criteria

ICU admission with signs of increased ICP. Discharge will be based on stabilization and continuous management of the underlying cause.

IV Fluids

IV fluids to prevent hypovolemia.

Nursing

Discharge Criteria

Discharge depends on causation.

Ongoing Care

ONGOING-CARE

FOLLOW-UP RECOMMENDATIONS

Patients should have follow up after discharge with appropriate departments.

Patient Monitoring

Serial neurological examinations are necessary. Additionally, arterial lines, Swan–Ganz catheters, ICP monitoring devices, and/or central venous catheters may be necessary.

DIET

Nutritional support via NG or PEG tube.

PATIENT EDUCATION

ICU is necessary for monitoring patients with signs of increased ICP.

PROGNOSIS

COMPLICATIONS

Additional Reading

SEE-ALSO

Codes

CODES

ICD9

Clinical Pearls