Emergency lectures - Management of increased intracranial pressure
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Transcript of Emergency lectures - Management of increased intracranial pressure
Management of Increased Intracranial Pressure
William M. Coplin, M.D., F.C.C.M.
Departments of Neurology and Neurological Surgery
Wayne State University School of Medicine
ICP
• Intracranial pressure is a process, not an event
• There are several pathophysiological mechanisms involved in intracranial pressure
• There are basic strategies for treatment
Increased ICP
• Pathophysiology– Acute neurological condition alters equilibrium of
components within cranial vault• Causes– Primary– Secondary
• Regardless of cause, ICP decreases cerebral perfusion, stimulates further swelling, and may cause herniation
ICP - Pathophysiology
• Intracranial pressure is a process, not an event!– Secondary injury can be more damaging than
primary injury• Main mechanisms of increased intracranial pressure– Trauma• Contusion• Diffuse axonal injury
– Stroke–Mass (tumor, hematoma…)– Edema (brain swelling)
Increased ICP andCushing’s Response
ICP – Understanding Determinants of Intracranial Pressure
• Volume of intracranial vault =• Intracranial contents– 80% brain tissue– 10% blood– 10% cerebrospinal fluid
• Increase in volume of any of these contents may cause increased intracranial pressure– Brain can swell (edema)– Extravascular blood can accumulate because of hemorrhage– Cerebrospinal fluid can accumulate from blocked outflow
ICP – Key Concept #1
• The cranial vault is a fixed volume• Bone does not expand• Cranial vault also contains blood and CSF• These components usually in state of equilibrium and
produce ICP– Usually measured in lateral ventricles– Normal pressure 10 to 20 mm Hg
Monro-Kellie Hypothesis
• “…because of the limited space for expansion within the skull, an increase in any one of the components causes a change in the volume of the others.”
• What does this mean?
ICP – Understanding Physics of Intracranial Pressure
Intracranial pressure rises as brain + blood + CSF volume increases
Decreased Cerebral Blood Flow
• What happens to brain cells as blood flow decreases?• Early compensatory mechanism:– Vasomotor stimulation• Assessment findings indicate this
• Changes in concentration of CO2
– causes cerebral vasodilation– causes vasoconstriction
• Decreased cerebral outflow
Increased ICP: Clinical Manifestations
Early Indicators
• Subtle changes in LOC• Pupillary changes• Weakness of one
extremity or one side• Constant headache
increasing in intensity and aggravated by movement or straining
Late Indicators
• Continuing decrease in LOC progressing to coma
• Bradypnea, bradycardia, hypertension, and fever
• Altered respiratory pattern• Projectile vomiting• Hemiplegia, “decorticate”
(flexor), or “decerebrate” (extensor) posturing
• Loss of brainstem reflexes
Cerebral Perfusion Pressure
• What is cerebral perfusion?
• Steady cerebral perfusion can be maintained if arterial mean pressure is ~50-150 mm Hg and ICP is below 40 mm Hg
• CPP = MAP – ICP
• Normal CPP is 70-100 mm Hg
ICP – Understanding Physics of Intracranial Pressure
This patient has dangerously high intracranial pressures, which increase likelihood of morbidity and mortality
ICP
CPP
ICP – Key Concept #2
• There is only one way out of cranial vault• Opening at base of skull known as foramen magnum
ICP – Key Concept #3
• When brain is squeezed through foramen magnum (herniation), brainstem is compressed, patient stops breathing, and patient dies
Causes of ICP: Epidural Hematomas
Example of epidural hematoma on CT scan on patient's left side, obviously of traumatic origin; this patient has soft tissue damage and fractured skull
Causes of ICP: Subdural Hematomas
Example of subdural hematoma on CT scan on patient's left side. Lesion extends for considerable distance over surface of hemisphere: note shift of midline
Causes of ICP: Swelling
Observe swelling (darker tissue) on brain CT scan of 37-year-old victim of pneumococcal meningitis
Cerebral Edema
• What is it?
• What is role of autoregulation in control of cerebral edema?
Causes of ICP: Swelling
Observe diffuse swelling (yellow-green tissue) and expansion of brain tissue
Causes of ICP: Swelling
Observe widening and flattening of gyri on brain surface
Cerebral Edema
• What is it?
• What is role of autoregulation in control of cerebral edema?
1501251007550250
0
25
50
75
Cerebral Perfusion Pressure (mm Hg)
Cer
ebra
l Blo
od F
low
(m
l/10
0 g/
min
)
Autoregulation AutoregulationBreakthrough
VasodilatoryCascade
PassiveCollapse
0
25
50
ICP
(m
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g)
From Rose JC, Mayer SA. Neurocrit Care. 2004;1:287-299.
Hypertension Can Drive ICP Elevations
100 200
normotensive
chronic hypertensive
Mean arterial pressure (mm Hg)
Cerebral Blood Flow
Increasing risk of hypertensive
encephalopathy
Increasing risk of ischemia
Adapted with permission from Varon J, Marik PE. Chest. 2000;118:214-227.
50 150 250
Patients with chronic hypertension autoregulate cerebral blood flow
around higher set points
Chronic HTN AffectsCBF Autoregulation
100 200
normotensive
chronic hypertensive
Mean arterial pressure (mm Hg)
Cerebral Blood Flow
Increasing risk of hypertensive
encephalopathy
Increasing risk of ischemia
50 150 250
Patients with cerebral ischemia lose their ability to autoregulate
ischemia
Adapted with permission from Varon J, Marik PE. Chest. 2000;118:214-227.
Autoregulation of CBFAffected by Ischemia
Medical Management
• Increased ICP is a true medical emergency• Initiate treatment promptly– Invasive monitoring of ICP–Manipulating one or more cranial vault component• Decrease cerebral edema• Maintain cerebral perfusion• Reduce CSF and intracranial blood volume
– Controlling fever–Maintaining oxygenation– Reducing metabolic demands
ICP: Basic Principles ofClinical Management
• Monitor intracranial pressure (invasively) and intervene to lower ICP when necessary– Elevate head of bed– Medications to decrease swelling– Decrease brain activity to reduce blood delivery and swelling “medically
induced coma”– Hypothermia– Surgical decompression when risk for herniation high
• Seizure prophylaxis?– Seizures occur in ~26% of severe TBI patients, with ~50% occurring within
first 24 hours
• Other priorities– Adequate nutrition, correction of electrolyte abnormalities, strict control of
blood sugar, strict temperature regulation…
Complications
• Brain stem herniation• Diabetes insipidus• Syndrome of inappropriate ADH (SIADH)
• Cause of these complications– Hypothalamic
• Treatment– DI: volume replacement and water replacement– SIADH: adequate volume with water restriction
ICP - Prognosis
• Effect of ICP– Patients with mean ICP > 20 mmHg during
hospitalization• 47% mortality vs.
– Patients with mean ICP < 20 mmHg• 17% mortality–(p < 0.001)1
1: Balestreri M, Czosnyka M et al. Impact of intracranial pressure and cerebral perfusion pressure on severe disability and mortality after head injury. Neurocrit Care. 2006,;4(1):8-13
Looking to the Future…
• Will new imaging and/or monitoring technologies lead to advances in patient care?
• Surgical interventions?• Medications to decrease swelling?– Hypertonic saline vs. mannitol?
• Decrease brain activity– Sedation and analgesia– Anticonvulsants?– “Medically induced coma”?
• Hypothermia?
Thank You