Intracranial Regulation

Increased intracranial pressure, or ICP, is a life-threatening condition characterized by increased pressure within the skull.

Now, increased ICP can occur if there’s an increase in the components of the brain, including brain tissue, cerebrospinal fluid, or CSF, or the blood supplying the brain.

An increase in brain components might develop in the case of cerebral edema, which can be due to infections, trauma, or hypoxia; space-occupying lesions such as brain tumors, abscesses, or intracranial hemorrhage; or disruptions in CSF circulation, like with hydrocephalus.

Alright, so, when it comes to regulating ICP, remember that the mature skull is a rigid structure that can’t expand. So, to maintain a normal ICP, there must be a balance between the volume of brain tissue, CSF, and blood.

If there’s an increase in any one of these three, there should be a compensatory decrease in the other two, which is known as the Monro-Kellie hypothesis.

Normally, the volume of the brain remains relatively stable, so ICP can be regulated by changes in CSF and blood volume.

When needed, CSF production can be decreased, or reabsorption can be increased, to help normalize ICP. Similarly, cerebral blood volume can be decreased either by cerebral vasoconstriction or increasing venous blood drainage out of the skull.

Now, the compensatory mechanisms that keep ICP within a normal range have limits and can be overwhelmed. When this happens, ICP starts to increase, which puts pressure on the ventricles and cerebral blood vessels.

In turn, this decreases cerebral blood flow and cerebral perfusion. Decreased cerebral perfusion means that less oxygen is delivered to the brain tissue, which causes neurons to swell and die, further increasing ICP.

At the same time, hypercarbia, or a build-up of carbon dioxide can occur, causing vasodilation, which also contributes to increased ICP.

If not corrected, increased ICP can lead to complications like papilledema, or swelling of the optic disc, which is the point where the optic nerve leaves the retina; or brain herniation, which occurs when a part of the brain is pushed through rigid spaces into another space of the skull or even out of it.

Brain herniation is a life-threatening emergency, and if it’s not promptly treated, it can be fatal. Now, early clinical manifestations of increased ICP include altered mental status, nausea and vomiting, headache, sluggish pupillary reaction to light, and even seizures.

Additionally, papilledema may cause visual abnormalities, such as double vision or even vision loss. On the other hand, late clinical manifestations include hypertension, bradycardia, and irregular breathing; these signs are referred to as Cushing’s triad, which indicate advanced brainstem dysfunction.

There could be fixed or dilated pupils, as well as loss of brainstem reflexes such as the gag reflex, swallowing reflex, or pupillary and corneal reflexes.

The level of consciousness could progress to coma. Lastly, there may be abnormal posturing, such as decerebrate or decorticate posturing.

Decerebrate posturing is where the arms are stiffly extended and abducted, and the wrists are pronated, with flexed fingers; while the legs are extended, with the feet in plantar flexion.

With decorticate posturing, the arms are adducted and flexed on the chest, with flexed wrists and fingers, while the legs are extended and internally rotated, with plantar flexion of the feet.

Diagnosis of increased ICP starts with a history and physical assessment. A CT should be done before performing a lumbar puncture when increased ICP is suspected, in order to rule out occupying lesions like a tumor or hematoma which could increase the risk of cerebral herniation during the procedure.

Then, CSF pressure can be measured by lumbar puncture or by inserting an intraventricular catheter directly within the lateral ventricle of the brain.

A fundoscopic examination of the eye can also be done, which can identify papilledema as an indirect sign of increased ICP.

Treatment is aimed at reducing the pressure within the skull and preventing further increases. This can be done by elevating the head of the bed at least 30 degrees to increase venous outflow and keeping it in a neutral midline position, since neck flexion can cause venous obstruction and contribute to increased ICP.

Respirations and oxygenation are supported to maintain cerebral oxygenation, since hypoxemia and hypercarbia tend to increase ICP; normothermia is maintained to keep brain metabolism and oxygen consumption to a minimum; and euvolemia is maintained to ensure adequate cerebral perfusion.

In addition, analgesics and anxiolytics can be given to decrease agitation, which can increase ICP, and osmotic diuretics, such as mannitol, can be used to help draw fluid from the brain tissue into the intravascular space.

If these measures cannot lower ICP, an intraventricular catheter can be placed to drain excess CSF from the ventricles. Another way to decrease ICP involves doing a decompressive craniectomy, where part of the skull is temporarily removed to help relieve the pressure.

Finally, treating the underlying cause, such as surgical removal of a tumor, abscess, or hematoma, should be done. Alright, let’s look at the nursing care you’ll provide for a patient with increased ICP.

Begin by positioning the head of their bed to at least 30 degrees and support their head in a neutral position. Monitor their vital signs; watch for hypertension, bradycardia, irregular breathing patterns; and maintain normothermia.

If your patient has an ICP monitor, be sure to monitor their pressure, and notify the health care provider if their pressure does not respond to treatment.

Also, institute cardiac and pulse oximetry monitoring. Take steps to ensure adequate oxygenation and ventilation to prevent hypoxia or hypercarbia, including administering high-flow oxygen or assisting with advanced airway management.

Be sure to maintain a normal fluid volume, and closely watch their electrolyte balance. Then, administer their prescribed medications.

During care, monitor their level of consciousness closely and evaluate the effectiveness of your interventions. Alright, as a quick recap… Increased ICP can occur if there’s an increase in the components of the brain, including brain tissue, CSF, or the blood supplying the brain.

Patients with increased ICP can present with altered mental status, sluggish pupillary reaction to light, abnormal posturing, as well as hypertension, bradycardia, and irregular breathing, referred to as Cushing’s triad.

Diagnostic tests used to confirm increased ICP include imaging tests, lumbar puncture, and intraventricular catheter placement.

Treatment and nursing considerations are focused on avoiding further increases in ICP, decreasing elevated ICP, and addressing the underlying cause.