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Friday, January 23, 2015

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.

1 comment:

  1. I just came across your blog and read this blog about Increased Intracranial Pressure. this is so information and something very new to me. thanks for sharing. your blog is just bookmarked.

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