Increased Intracranial Pressure

This week I had a patient who had herniated. I know that neuro is a weak topic for me so I decided to do a post on intracranial pressure.

This post will act as a quick guide to increased intracranial pressure. What is it? What causes it? How do we treat it? I've also included a quick table on assessing rising intracranial pressure (ICP). We'll do a slight case study.

What is Increased Intracranial Pressure?

Increased intracranial pressure is defined as being > 20 mm Hg for > 5 minutes.

Normal ICP	= 5-15 mm Hg
If ICP	> 20 mm Hg--- Time to treat!!
If Sustained ICP	> 40 mm Hg --- Poor prognosis
If Sustained ICP	> 60 mm Hg--- Almost always fatal

Causes of Increased ICP

• Inadequate oxygen delivered to the brain-- Can be caused by oxygen deprivation, decreased cerebral blood flow, or a result of a direct injury
• Mass effect due to hydrocephalus or an intracranial hematoma
• Interstitial edema caused by increased capillary permeability

Patho

When pressure is increased in the cranium the body compensates by doing the following in this order:

1. Reduces Cerebral Spinal Fluid by contracting the ventricles
2. Reduces blood volume to the head by either hyperventilation (decreases PaCO2 causing vasoconstriction) or Cushing's reflex (blood pressure increases and heart rate decreases).
3. Herniation (displacement of brain tissue)

Treating Increased ICP

• Prevent a "2nd hit"- Hypotention, hypoxemia and decreased cerebral perfusion pressure are major causes of secondary brain injury. In my patient we had a hard time keeping her O2 saturations up.
• O2 and CO2 - Endotracheal intubation and mechanical ventilation need to be deployed.
• Maintain Cerebral Perfusion Pressure - Maintain SBP > 90. Carefully monitor intake and output for fluid excess or deficit. My patient's SBP was 140-160 all day.
• Decrease Oxygen Demands - Aggressively treat fever. Do not allow the patient to shiver. (We used a cooling blanket.) Sedation with Propofol is recommended to lessen the increased ICP caused by agitation, suctioning, coughing, or fighting the ventilator. (We used Versed not Propofol.)
• Control ICP - Elevate head of bed 30-45 degrees to promote venous outflow. Give Mannitol (monitor for seum osmolality.) Lasix is given sometimes to decrease CSF production. Maintain serum albumin because low albumin is a cause of cellular edema- and we want our patient's perfusing, right? Right.)
  
  My patient was given Mannitol but no Lasix. The Mannitol will need to be administered through a filter. It also will make them pee, a lot. So keep an eye on their foley bag that it doesn't overflow.

Assess Rising ICP

As Increased ICP progresses to herniation, the following structures will produce these signs due to compression and ischemia:

Structure	Level of Consciousness	Breathing Pattern	Motor Movement / Posture	Pupils	Other
Cerebral Cortex Motor Strip	Awake Lethargic Obtunded Stuporous	Normal	Weakness/ Paralysis	Normal size React to light	Specific dysfunction according to affected structure
Diencephalon	Semi-coma Coma	Cheyne- Stokes	Gegenhalten (resists movement) Decorticate (arms flexed, legs extended)	Normal size React to light	Diabetes Insipidus Fever
Midbrain	Coma	Central Neurogenic Hyperventilation (Deep, rapid, can't be controlled unless neuromuscular blocking agent is used)	Decerebate (arms and legs are extended, arms are internally rotated)	Midposition Unreactive to light	Ptosis (eye is down and out)
Pons	Coma	Apneustic (prolonged inspiration) Cluster (various patterns with periods of apnea)	Flaccid	Pinpoint Unreactive to light
Medulla	Coma	Agonal, Ataxic (patternless, long periods of apnea)	Flaccid	Dilated Unreactive to light	Absent Doll's eyes No response to caloric stimulation Cushing Reflex

I hope that table and this post will help you understand what's happening during increased intracranial pressure.

Other posts you might be interested in looking at are:

Complete Head to Toe Assessment
Glasgow Coma Score
Dirty Mnemonics to Remember the 12 Cranial Nerves

Leave a comment if you have a topic you'd like for me to discuss!

Xoxo,

Nightingale.