Intracranial Pressure Paula Ponder MSN, RN, CEN (Relates to Chapter 62,63 Intracranial Pressure in the textbook)
Learning objectives • Discuss the physiologic mechanisms that maintain normal intracranial pressure • Identify the common clinical manifestations of the patient with increased intracranial pressure. • Describe the nursing management of the patient with increased intracranial pressure.
Intracranial Pressure • Skull has three essential components • Brain tissue 78% • Blood 12% • Cerebrospinal fluid (CSF) 10%
Intracranial Pressure • Factors that influence ICP • Arterial pressure • Venous pressure • Intraabdominal and intrathoracic pressure • Posture • Temperature • Blood gases (CO2 levels) • The brain has to be able to accommodate and change all these things. Things change, like BP, we sneeze, stand up, sit down, ect.
Intracranial PressureRegulation and Maintenance • Normal intracranial pressure • Pressure exerted by the total volume from the brain tissue, blood, and CSF • Modified Monro-Kellie doctrine: Describes relatively constant volume within skull structure • Your head is a rigid box and there is limited room for expansion. An increase in any one of these components (brain tissue, blood, and CSF) causes a decrease in volume of the others. This is a mechanism to compensate. If things are working normally, the brain can compensate just fine. The easiest thing to decrease is the CSF, it’s also the first thing that the head pushes out. Blood is next to be pushed out, but vessels collapse, and then we get hypoxia, atrophy, necrosis. If this goes on for long enough there will be brain damage due to hypoxia • Normal ICP is 0-15
Intracranial PressureRegulation and Maintenance • Normal compensatory adaptations • Displacement of CSF into spinal subarachnoid space • Ability to compensate is limited • If volume increase continues, ICP rises • Measuring ICP • Ventricles, subarachnoid space, epidural space, brain parenchymal tissue
Intracranial PressureCerebral Blood Flow • Definition • The amount of blood in milliliters passing through 100 g of brain tissue in 1 minute • About 50 ml/min per 100 g of brain tissue • Autoregulation of cerebral blood flow • Automatic alteration to maintain constant flow to brain
Intracranial PressureCerebral Blood Flow • Cerebral perfusion pressure (CPP) • Pressure needed to ensure blood flow to the brain • CPP = MAP – ICP • Normal is 70 to 100 mm Hg • <50 mm Hg is associated with ischemia and neuronal death • MAP greater than 150 we lose auto regulation. Vessels are manually constricted, therefore they can’t constrict anymore • If we get an ICP is equal to MAP cerebral circulation ceases • We need a MAP of 60 to perfuse our brain and kidneys and what not. We need CPP of 70 – 80 • MAP is 2x the diastolic plus the systolic divided by 3
Intracranial PressureCerebral Blood Flow • Pressure changes • Compliance is the expandability of the brain • Compliance = Volume/Pressure • With low compliance, small changes in volumes creates huge increases in pressure
Intracranial PressureCerebral Blood Flow • Pressure-volume curve represented by stages • Stage 1: High compliance • When we displace CSF • Stage 2: Compliance ↓ , risk for ↑ ICP • Stage 3: Any small addition in volume causes a great ↑ in ICP, loss of autoregulation • When we see Cushing’s Triad • Stage 4: ICP rises to lethal levels
Intracranial PressureCerebral Blood Flow • Factors affecting cerebral blood flow • Cardiac or respiratory arrest • Trauma • Tumor • Cerebral hemorrhage, or stroke • Treat shit with dopamine, but that gives them tachycardia. May give them “pressers”
Increased Intracranial PressureCerebral Edema • Increased accumulation of fluid in the extravascular spaces of brain tissue • Three types of cerebral edema: • Vasogenic • Mainly in the white matter • Cytotoxic • Results from local disruption of the functional integrity of cell membranes • Interstitial • Uncontrolled hydrocephalus • Primarily in kids, can be communicating or non communicating
Increased Intracranial PressureMechanisms of Increased ICP • Mass lesion • Cerebral edema • Head injury • Brain inflammation • Say from an abscess • Metabolic insult
Increased Intracranial PressureClinical Manifestations • Headache • Often continuous and worse in the morning • Vomiting • Not preceded by nausea • Projectile (late sign)
Increased Intracranial PressureClinical Manifestations • Change in level of consciousness • Change in vital signs • Cushing’s triad • Bradycardia, widened pulse pressure, and HTN • With a widened pulse pressure, cerebral blood flow is decreasing • Will see Cheyne-Stokes • Will lose brain stem reflexes, gag, corneal, and swallowing, pupils • Ocular signs • Pupils won’t dialate
Increased Intracranial PressureClinical Manifestations • ↓ In motor function • Decerebrate posturing (extensor) • Indicates more serious damage • Extension of all 4 extremities • Decorticate posturing (flexor) • “to the core” internal rotation and flexion of all 4 extremities
Increased Intracranial PressureComplications • Two major complications of uncontrolled increased ICP • Inadequate cerebral perfusion • Causes brain tissue hypoxia • Cerebral herniation • Tentorial herniation • Uncal herniation • Cingulate herniation • Sustained increase in ICP results in brainstem compression and herniation of brain from one compartment to another
Increased Intracranial PressureDiagnostic Studies • Aimed at identifying underlying cause • MRI • CT • Cerebral angiography • EEG
Increased Intracranial PressureDiagnostic Studies • Aimed at identifying underlying cause • ICP measurement • Transcranial Doppler studies • PET • Brain tissue oxygenation measurement
Increased Intracranial PressureMeasurement of ICP • ICP monitoring used to guide clinical care when at risk for increased ICP • Those admitted with a Glasgow Coma Scale of 8 or less • Less than 8 are probably going to be intubated • Those with abnormal CT scans or MRI • History of neurological insult
Increased Intracranial PressureMeasurement of ICP • The gold standard for ICP monitoring is the ventriculostomy • Risk of infection, of course
A wave • Commonly associated with temporary change neuro status • B wave • Respiratory changes • C wave • Clinically insignificant
Increased Intracranial PressureMeasurement of ICP • Inaccurate readings can be caused by • CSF leaks • Obstruction in catheter • Differences in height of bolt/transducer • Kinks in tubing • Incorrect height of drainage system relative to patient’s reference point
Increased Intracranial PressureCollaborative Care • Adequate oxygenation • ABG analysis guides the oxygen therapy • May require mechanical ventilator • Drug therapy • Mannitol • Corticosteroids • Big doses of these guys!
Increased Intracranial PressureCollaborative Care • Hyperventilation therapy • Was the mainstay treatment • Brief periods may be useful for refractory intracranial hypertension • Increases the risk for focal cerebral ischemia • Nutritional therapy • ↑ Need for glucose • Keep patient normovolemic • IV 0.9% NaCl
Increased Intracranial PressureNursing Management • Nursing assessment • Glasgow Coma Scale • Neurologic assessment • Motor strength and response • Vital signs • BP, Pulse, Respiratory rate, Temperature • O2 saturation
Increased Intracranial PressureNursing Management • Planning • Overall goals • Maintain a patent airway • ICP within normal limits • Normal fluid and electrolyte balance • No complications secondary to immobility and decreased LOC
Increased Intracranial PressureNursing Management • Nursing implementation • Respiratory function • Fluid and electrolyte balance • Monitoring of intracranial pressure • Body position maintained in head-up position • Protection from injury • Psychologic considerations
Summary • Maintain airway • Semi fowlers is how they need to be laying • Maintain adequate oxygenation • Monitor neurological assessment for changes • Document and Report any changes.