Do not dramatically lower the bloodpressure in patients with increased intracranial pressure (ICP)
Author:
Emily Riehm Meier, MD
What to Do - Make a Decision
Brain parenchyma, cerebrospinal fluid (CSF), and blood are the three components of the intracranial cavity (Table 215.1). The durability of the skull
protects the brain from outside insults, but cannot accommodate an increase
in the amount of intracranial contents. Increased ICP is, therefore, a medical
emergency that requires careful diagnosis, monitoring, and management.
The Cushing triad is classically associated with increased ICP but is a
relatively late finding. It consists of hypertension, bradycardia, and hypopnea. Hypertension occurs as the body attempts to maintain cerebral perfusion pressure (CPP). CPP can be calculated by subtracting the mean arterial
pressure (MAP) from ICP (CPP = MAP - ICP). Because CPP is interdependent on MAP, an acute fall in blood pressure in patients with increased
ICPplaces thematriskforcerebralhypoperfusion and long-termneurologic
damage. Hypertension associated with increased ICP causes a compensatory
bradycardia.Decreasedrespiratoryrateisalatefinding,signalingimpending
herniation and is secondary to compression of brainstem respiratory centers
from the increased pressure. Ideally, increased ICP should be identified and
treatment started before these findings arise (Table 215.2).
Evacuation of a fluid (CSF or blood) collection or mass removal are the
surgical interventions for increased ICP. Medical management of increased
ICP includes elevation of the head of the bed, osmotic diuretics, hypertonic
saline, hyperventilation, sedation, and hypothermia. Varying amounts of
evidence exist for the effectiveness of these interventions in decreasing ICP.
Elevatingtheheadofthebedto30degreesisoneofthesimplestinterventions
for patients with suspected increased ICP. It improves venous outflow from
the brain and can be an effective measure at preventing increased ICP from
escalating.
Table 215.1 Causes of Increased Intracranial Pressure
Brain parenchyma
Space-occupying lesion
• Epidural or subdural hematoma
• Mass
• Abscess
Cerebral edema
• Infection (meningitis/encephalitis)
• Toxin induced encephalopathy (lead, liver failure, Reye syndrome)
• Hypertensive encephalopathy
CSF
Hydrocephalus
• CSF Overproduction
• Decreased CSF absorption
• Blockage of CSF flow (aqueductal stenosis)
Blood
Head trauma
Subarachnoid hemorrhage
Venous sinus thrombosis
Miscellaneous
Pseudotumor cerebri
CSF, cerebrospinal fluid.
Table 215.2 Management Guidelines for Increased Intracranial Pressure
First-Line Therapy
• Sedation, analgesia, paralytics
• CSF drainage if ventriculostomy present
• Hyperosmotic therapy (mannitol of hypertonic saline)
• Mild hyperventilation (PaCO2 30–35 mm Hg)
Second-Line Therapy
• Barbiturate coma
• Hypothermia
• Aggressive hyperventilation (PaCO2 <30 mm Hg)
CSF, cerebrospinal fluid; PaCO2, partial pressure of arterial carbon dioxide.
Mannitol is the most thoroughly studied medication used to induce an
osmotic diuresis in patients with increased ICP. Doses range from 0.25 to 1
g/kg and should be given as a bolus infusion. Mannitol is a large sugar that
doesnotcrosstheblood–brainbarrier.Thisallowsittoexertanosmoticeffect
on brain parenchyma, effectively decreasing the volume of the intracranial
space,whichlowersICP.Mannitolalsoincreasesintravascularvolume,which
improves cerebral blood flow and perfusion. If autoregulation is maintained
within the brain, the improved oxygenation can lead to vasoconstriction in
certain areas, which would also decrease ICP. One side effect of mannitol
therapy is renal failure when serum osmolarity is >320 mOsm/L. If this
problem arises, hypertonic (3%) saline can provide similar effects and can
increase serum osmolarity to 360 mOsm/L without a concomitant risk of
renal failure.
HyperventilationisacontroversialinterventionforincreasedICP.Cerebral blood flow (CBF) is exquisitely sensitive to changes in oxygenation
and ventilation, with hypoxia and hypercapnia causing increased CBF and
hypocapnia decreasing CBF. Intentionally inducing hypocapnia by hyperventilating a patient with increased ICP can lead to cerebral hypoperfusion.
Even mild hypocapnia (partial pressure of arterial carbon dioxide [PaCO2]
of 32–35 mm Hg) leads to hypoxia and generation of lactic acid, leading to
possible neurologic damage. CBF decreases in the first 24 hours following
head trauma and gradually improves over the next 3 to 4 days. Therefore,
aggressive hyperventilation is not generally used in the treatment course
to minimize additional risk of neurologic damage, but mild-to-moderate
hyperventilation may be effective particularly for refractory ICP problems.
Two other therapeutic options may be tried if ICP is not lowered by hyperosmolarity and hyperventilation: barbiturate coma and hypothermia. Because of decreased cerebral metabolism, cerebral oxygenation requirements
are lower for patients when they are in barbiturate coma. Pentobarbital is the
mostfrequentlyusedbarbiturateusedtoinducecoma.Thesepatientsshould
have continuous electroencephalograph monitoring to ensure adequate suppression of brain activity. Mechanical ventilation and pressor support will
likely be needed in these patients. Hypothermia is another strategy aimed at
decreasing cerebral metabolism and subsequently decreasing CBF.
Steroids are commonly used to treat cerebral edema in patients with
brain tumors. However, there is no evidence to support the use of steroids in
increased ICP, unless patients have a documented decreased cortisol level.
Suggested Readings
Allen CH, Ward JD. An evidence-based approach to management of increased intracranial
pressure. Crit Care Clin. 1998;14:485–495.
Jankowitz BT, Adelson PD. Pediatric traumatic brain injury: past, present and future. Dev
Neurosci. 2006;28(4-5):264–275.
Soustiel JF, Mahamid E, Chistyakov A, et al. Comparison of moderate hyperventilation and
mannitol for control of intracranial pressure control in patients with severe traumatic brain
injury–astudyofcerebralbloodflowandmetabolism.ActaNeurochir(Wien).2006;148:845–
851.
Tasker RC. Neurological critical care. Curr Opin Pediatr. 2000;12:222–226.
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Book Source Details
- Book Title: Avoiding Common Pediatric Errors
- Author(s): Anthony D Slonim MD, DrPH; Lisa Marcucci MD
- Year of Publication: 2008
- Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Lippincott Williams & Wilkins.
Other Book Chapters Related to Increased intracranial pressure
Read excerpts from these other book chapters related to Increased intracranial pressure:
Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Williams & Wilkins.
More About Causes of Increased intracranial pressure
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More About This Book:
Title: Avoiding Common Pediatric Errors
Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7489-6
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