ICP_Smith - ICP & Head Trauma ICP Sophia R. Smith,...

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Unformatted text preview: ICP & Head Trauma ICP Sophia R. Smith, MD WRAMC November 2, 2005 Introduction Introduction • Head injuries are one of the most common Head causes of disability and death in children. causes • The Centers for Disease Control and The Prevention (CDC) estimates that more than 10,000 children become disabled from a brain injury each year. • Head injuries can be defined as mild as a Head bump to severe in nature. bump Prevalence of Pediatric Trauma Prevalence • Trauma is the leading cause of death in infants Trauma • • • and children and Trauma is the cause of 50% of deaths in people Trauma between 5 and 34 years of age between Motor vehicle related accidents account for 50% Motor of pediatric trauma cases of $16 billion is spent annually caring for injuries to $16 children less than 16 years of age children Traumatic Brain Injury Traumatic Primary Brain Injury Results from what has Results occurred to the brain at the time of the injury injury • Secondary Brain Secondary Injury Injury Physiologic and Physiologic biochemical events which follow the primary injury primary Examples of Primary Brain Injuries Factors that Effect Secondary Brain Injuries Brain • Blood Pressure • Oxygenation • Temperature • Control of Blood Glucose • Fluid Volume Status • Increased Intracranial Pressure SOME of the SECONDARY EVENTS IN TRAUMATIC BRAIN INJURY BBB disruption edema formation diffuse axonal inflammation injury apoptosis necrosis ischemia Brain trauma energy failure cytokines Eicosanoids endocannabinoids Acetyl Choline ROS polyamines Calcium Shohami, 2000 Green – pathophysiological processes; Yellow – various mediators Anatomy of the cranium Anatomy • There are various brain contents that are There localized within a rigid structure. localized – Cranium • The cranial vault contents include: The The brain – The brain The cerebral – The cerebral spinal fluid The cerebral – The cerebral blood Cerebral Spinal Fluid Cerebral • CSF – 150 cc in adults at all times • Children slightly less Produced – Produced by choroid plexus – 20 cc/hr CSF – CSF is absorbed into venous system at the subarachnoid villi Cerebral blood and brain Cerebral • Cerebral blood – Sum of blood in capillaries, veins, and arteries • Brain – 80% of the total intracranial volume • All of these contents are maintained @ a All balanced pressure referred to as intracranial pressure (ICP) pressure Monro-Kellie Doctrine Monro-Kellie Doctrine • The ICP within the skull is directly related The to the volume of the contents. to Defined Monro-Kellie – Defined as the Monro-Kellie Doctrine This – This doctrine states that any increase in volume of the contents within the brain must be met with a decrease in the other cranial contents. contents. Monro-Kellie Doctrine Vintracranial vault=Vbrain+Vblood +Vcsf Increased Intracranial Pressure Cerebral Blood Flow Cerebral • CBF is directly linked to the metabolic CBF requirements of the brain. requirements • As the brain metabolic activity increases, CBF increases – Vasodilatation of cerebral vessels – Increase in cerebral blood volume – Consequent increase in ICP Cerebral blood flow Cerebral • CBF maintained when MAP range is CBF 50mmHg to 150mmHg 50mmHg – Cerebral auto regulation • As BP increase baroreceptors sense event and cerebral arteries vasoconstrict CBF maintained with a CBV decrease • As BP decrease cerebral arteries dilate As to increase flow CBV increase Auto regulation Auto • This process is lost in pathological states – Esp. Head trauma – CBF decreases linearly to MAP below range • Results is ischemia (strokes) to brain regions CBF – CBF increases linearly to MAP above auto regulation range regulation • HTN encephalopathy as CBV and ICP increase HTN Mediators of CBF Mediators • Local and global mediators of CBF and Local metabolism are important. metabolism are – Hypoxia and pH are most important – As local paO2 decreases, CBF increases CBF – CBF is affected by pH (and its surrogate pCO2) pCO2) Blood: Cerebral Blood Flow x x The brain has the ability to control its blood supply to match its metabolic requirements Chemical or metabolic byproducts of cerebral metabolism can alter blood vessel caliber and behavior Studies of hyperventilation & ICP Studies • This relationship has been well studied as This a therapeutic option in particular intentional hyperventilation to lower cerebral blood flow and thus intracranial pressure. pressure. • No longer a practice – Modest hyperventilation On call On • So, you are in the ER on your first So, night of call and the next thing you know you get your very first trauma patient. patient. • How do you evaluate? Trauma Traumatic Brain Injury Glascow Coma Scale Eye Opening Spontaneous To Voice To Pain None Best Verbal Oriented Confused Inappropriate Words Incomprehensible Sounds None Best Motor Obeys Commands Localizes Pain Withdraws to Pain Flexion to Pain Extension to Pain None 4 3 2 1 5 4 3 2 1 6 5 4 3 2 1 Severe TBI Severe • Indications for Intubation – GCS< 8 – Fall in GCS of 3 – Unequal pupils Inadequate – Inadequate respiratory effort or significant lung/chest injury significant – Loss of gag – apnea Treatment Treatment • Intubation. – Pretreatment with lidocaine 1 mg/kg IV may prevent rise in intracranial pressure (ICP). Treatment Treatment • Hyperventilation – to maintain PO2 >90 torrs, PCO2 30 to 32 torrs. Hyperventilation – Hyperventilation may actually increase ischemia in at risk brain tissue if PCO2 <25 torr by causing excessive vasoconstriction and has fallen out of favor. Prophylactic hyperventilation for those without favor Prophylactic increased ICP is contraindicated and worsens outcomes. outcomes. • PEEP relatively contraindicated because PEEP reduces cerebral blood flow. Maintain normal cardiac output. Maintain f • IIf hypotensive from other cause such as multi-trauma, treat shock as usual. • Normal saline is preferred over LR since Normal LR is slightly hypotonic. • Hypertonic saline (3% or 7.5%) can be Hypertonic used. Especially if you see ICP changes. used. Maintain normal cardiac output. Maintain f • IIf markedly hypertensive, consider labetalol or nitroprusside. • Avoid lowering the blood pressure unless Avoid diastolic blood pressure is >120 mm Hg. Diuresis Diuresis • Mannitol 1 g/kg IV over 20 minutes induces osmotic diuresis. Avoid – Avoid if hypotensive or have CHF/renal failure. • Some suggest furosemide (Lasix and Some furosemide others). Avoid – Avoid if hypotensive. ICP Precautions ICP • Elevate head of bed 30 degrees. • Seizure prophylaxis: Phenytoin will Phenytoin reduce seizures in the first week after injury but does not change the overall outcome. • Steroids are ineffective in controlling ICP in the trauma setting. Positioning II Manipulation of CPP Manipulation CPP = MAP - ICP CPP • Maintain adequate intravascular volume • • – CVP Increase MAP Increase Utilize – Utilize alpha agonist--dopamine, phenylephrine, norepinephrine phenylephrine, What is appropriate goal for children? CPP for children CPP • Aim for a CPP of >60 mmHg by – by maintaining an adequate MAP and control of ICP of • MAP – ICP = CPP – Minimizing the morbidity of TBI in children Additional therapies Additional • Prevent hyperglycemia: exacerbates exacerbates ischemic cerebral damage • Attention to electrolyte status. These These patients are prone to electrolyte abnormalities due to osmotic diuresis, cerebral salt losing states, SIADH and diabetes insipidus Manipulation of ICP Manipulation Blood • Decrease cerebral metabolic demand – sedation, analgesia, barbiturates – avoid hyperthermia – avoid seizures • Hyperventilation – decreases blood flow to brain – only acutely for impending herniation • Mannitol Manipulation of ICP Manipulation Brain • Mannitol – dehydrate the brain, not the patient! – monitor osmolality • Hypertonic saline • Decompressive craniectomy ICP Monitoring ICP Monitoring • ICU patients who have sustained head trauma, brain hemorrhage, brain surgery, or conditions in which the brain may swell might require intracranial pressure monitoring. • The purpose of ICP monitoring is to continuously measure the pressure surrounding the brain. Why Monitor? Why • • • Detect “events” Manage intracranial pressure Manage cerebral perfusion pressure How? How? • • • • Ventriculostomy Intraparenchymal fiberoptic catheter Subarachnoid monitor Useful adjuncts: – Arterial line – Central venous line – Foley catheter Manipulation of ICP Manipulation CSF • External drainage – therapeutic as well as diagnostic – technical issues – infectious issues What to do with the information... information... • Goal: adequate oxygen delivery to maintain Goal: the metabolic needs of the brain. the • Intracranial pressure <20 • Cerebral perfusion pressure >50-70 mm Hg Cerebral CPP=MAP-ICP CPP=MAP-ICP Indications for ICP monitoring Indications • Glasgow coma scale <8 Glasgow • Clinical or radiographic evidence of Clinical increased ICP increased • Post-surgical removal of intracranial Post-surgical hematoma hematoma • Less severe brain injury in the setting Less which requires deep sedation or anesthesia anesthesia Other monitoring devices Other monitoring devices • • • • CT Scan MRI PET Scan Jugular Venous Oxygen Saturation Near­infrared Spectroscopy Near­infrared Spectroscopy • Uses absorption characteristics of oxy Hgb, deoxy Hgb, and [o] cyt aa3 • Uses the ability to penetrate the superficial brain • Therefore the state of oxygenation can be determined. • Good assessment of cerebral oxygenation Transcranial Doppler US Transcranial Doppler US • TCD is a noninvasive technique used to determine cerebral blood velocity in large intracranial arteries. • Assessment of – Brain death – Reperfusion injury – Identify regions S/P TBI that are adversely effected Cerebral Microdialysis Cerebral Microdialysis • Measuring the partial pressure of oxygen of brain parenchyma and metabolites using microdialysis • Electrode in vulnerable brain region measures O2 concentration • Measures also local brain metabolism ...
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