22Physiology Brain Metabolism: Like all tissues, the brain requires a constant supply of oxygen and nutrients.
23Physiology Brain accounts for 2% of total body mass. Brain accounts for 15% of total metabolism in the body.Brain metabolic rate 7.5 times the rate of other neurological tissues.
24PhysiologyAlmost all of the brain’s energy needs are supplied by glucose.Provided by capillaries in the brain.
25PhysiologyInsulin NOT needed for glucose delivery to brain tissues.
26PhysiologyThe brain is among the most oxygen dependent organs in the body.The brain is not capable of much anaerobic metabolism.Primarily due the high metabolic rate of the neurons.
27PhysiologyBecause of this, sudden cessation of blood flow to the brain can cause unconsciousness within 5-10 seconds.
28Physiology Neuroglobin: Intracellular hemeprotein. Reversibly binds oxygen with an affinity greater than that of hemoglobin.Increases oxygen availability to brain tissue and provides protection under hypoxic or ischemic conditions, potentially limiting brain damage.
29Physiology Brain requires: OxygenationGlucosePerfusionAny deficit in these results in immediate dysfunction.
30Intracranial Pressure The cranial vault is effectively a closed container.Largest opening is the foramen magnum.Limited room for brain swelling.
31Intracranial Pressure There is always some pressure in the brain.Referred to as intracranial pressure (ICP).Normal ICP:Children: 0-10 mm HgAdults: 0-15 mm Hg
32Intracranial Pressure Volume of the cranial vault defined by the Monro-Kellie doctrine:Intracranial Volume (fixed) =Brain Volume + CSF Volume + Blood Volume + Mass Lesion Volume
33Intracranial Pressure Normally:Brain = 80% of cranial vault spaceBlood = 10% of cranial vault spaceCSF = 10% of cranial vault spaceSpace Available for Blood or MASS = 0%
34Intracranial Pressure To perfuse the brain, the pressure of blood delivered to the brain MUST be greater than the intracranial pressure.CPP = MAP - ICP
35Intracranial Pressure Mean Arterial Pressure:MAP DP + 1/3 (SP–DP)
36Intracranial Pressure Perfusion of the brain is driven by the CPP.MAP - ICP = CPP= 40CPP of 60 is the critical minimum threshold.CPP of 40 is the critical minimum threshold for children < 8 years of age.
37Intracranial Pressure Injury to brain tissue causes:SwellingBleedingEdemaAll cause an increase in the size and mass of the brain.
38Intracranial Pressure As the brain swells, it will eventually reach a critical volume where ICP increases to a point that perfusion is compromised.
39Brain Injury Etiology of TBI: Primary injury: Damage to the brain from mechanical effects of trauma causing:IschemiaAnoxia/hypoxiaShear injury
40Brain Injury Secondary Injury: Results from a traumatic event and changes in the brain or in the brain vasculature.HypoxiaHypotension ( cerebral blood flow) ICPHyperglycemia/HypoglycemiaMetabolic disturbancesSeizures
41Brain Injury 12-24 hours post-injury: Hypoperfusion and decrease in CBF.Results from increases in distal microvascular resistance and intravascular clot formation.
42Brain Injury 1-5 days post injury: Increased CBF > CMRO2. Vascular engorgementSwellingIncreased ICPInduction of free radicals and oxidative stress.
43Brain Injury 5/6-14 days post injury: CBF slows due to vasospasm Brain vulnerable to changes in ICP.
44Brain Injury Secondary Injury: Impaired autoregulation: Autoregulation is the ability of the brain to maintain CBF in light of changes in BP and CPP.Impaired autoregulation causes: O2 delivery to the brain and cerebral ischemia.Cerebral metabolism altered due to loss of, or a decrease in, CBF.Conversion from aerobic to anaerobic metabolism.
45Brain Injury Secondary Injury (extracranial causes): Hypotension (SBP < 90 worsens outcomes)Hypoxia (significantly associated with increased morbidity and mortality)Hypocapnia:Low CO2 causes vasoconstriction1 mm Hg decrease on CO2 = 3% decrease in CBF.AnemiaHyperthermia
47Brain Injury Compensatory mechanisms: Brain shifts or is compressed. Venous blood is shunted to heart.CSP shunted to spinal SAS.
48Vegetative- Severe Disability Secondary InjurySecondary InsultsNo. of PatientsGood-ModerateDisabilityVegetative- Severe DisabilityDeadHypoxia7845%22%33%Hypotension11326%14%60%Both526%19%75%
49Signs and Symptoms Early ( ICP): Altered mental status Agitation Nausea and/or vomitingHemiparesis
50Signs and Symptoms Late ( ICP): Coma Hemiplegia Posturing Cushing’s Triad:Widening pulse pressureBradycardiaRespiratory abnormalities
51Brain HerniationResults when ICP increases beyond the capability of physiologic and limited physical compensation mechanisms.
52Brain Herniation Major areas of brain herniation syndrome: Subfalcial (a)Uncal (b)Central transtentorial (c)External (d)Cerebellotonsillar (e)
53TBI Mild (GCS = 14-15) Moderate (GCS = 9-13) Severe (GCS < 9) ~ 80% of patientsModerate (GCS = 9-13)~ 10% of patientsSevere (GCS < 9)~ 10 of patients
54Trauma Types Scalp Laceration: Highly vascular Can lead to massive blood loss
55Trauma Types Skull Fracture: Classified by: LocationPatternOpen/closedUp to 50% of patients with skull fracture will NOT have LOC or neurologic symptoms.
56Trauma Types Concussion: Brief and temporary loss of neurologic function following head trauma.May occur with or without LOC.Symptoms:AmnesiaDuration of amnesia predictive of injury severity.Confusion
57Concussion Grade 1: No LOC Confusion without amnesia Treatment: Remove from event and examine immediately and every 5 minutes for the development of amnesia.If asymptomatic > 20 minutes, can return to game.2 Grade 1 concussions:No sports for the day3 or more Grade 1 concussions:Out for season and no contact sports for 3 months
58Concussion Grade 2: No LOC Confusion and amnesia Treatment: Remove from event for the day.Refer for exam the next day.May return in 1 week if asymptomatic with rest/exertion.2 Grade 2 concussions:No play for 1 season3 Grade 2 concussions:Season terminated.
59Concussion Grade 3: LOC Treatment: Transport to ED for evaluation Return to sport in 1 month if asymptomatic for a 2-week period.2 Grade 3 concussions:Season terminated.
60Trauma Types Cerebral contusion: Most frequent type of TBI Most common in:Subfrontal cortexFrontal lobeTemporal lobeOccipital (less common)Often associated with SAH.
63Trauma Types Subarachnoid hemorrhage: Disruption of subarachnoid vessels.1/3 of all patients with moderate to severe TBI have traumatic SAH.
64Trauma Types Epidural hematoma: Collection of blood between the dura and the skull.Arterial bleed.Incidence:% of all head-injured patients.<10% of head-injured patients who are comatose.Almost all associated with skull fracture.80% will progress to uncal herniation.
66Epidural Hematoma Signs and Symptoms: Classis syndrome (<20% of cases):Immediate LOC.Patient awakens and has a “lucid interval.”Loses consciousness as hematoma expands.Most commonly:Most patients either never lose consciousness or never regain consciousness.
67Trauma Types Subdural hematoma: Collection of blood between the dura and the SAM.Venous bleed.Associated with sudden acceleration and/or deceleration.Tears bridging veins.
69Subdural HematomaUsually more brain parenchymal injury than epidurals.Classified as:Acute (< 3 days)Subacute (3-14 days)Chronic (> 14 days)
70Trauma Types Diffuse Axonal Injury (DAI): Interruption of axonal fibers in the white matter and brain stem.Shearing forces (usually deceleration) cause injury.Adults: MVCsBabies: “Shaken baby” syndromeInjury occurs immediately and is usually irreversible.
79Assessment/Treatment Palpate skull, facial bones and neckAssess rate, depth and quality of respirations.Consider tachypnea at the following rates a sign of deterioration:Infant: 40 breaths per minuteChild: 30 breaths per minuteAdult: 20 breaths per minute
80Assessment/Treatment Assess pupils carefully:Pupil sizeSymmetryReactivity to light
81Assessment/Treatment Pupillary assessment:Bilateral symmetry (asymmetric pupils differ more than 1 mm).Reactivity to light (a fixed pupil shows <1mm change in response to bright light).Dilation (greater than or equal to 4mm diameter in adults)
82Assessment/Treatment Single fixed and dilated pupil:45% poor outcomeBilateral fixed and dilated pupils:82% poor outcome
83Assessment/Treatment Mid-position fixed and dilated pupil:Suggests brain stem herniation.Indicative of mass on same side.Treat hypoxia and hypotension, if present.Treat increased ICP per practice parameters.
84Assessment/Treatment Indications of herniation:Unilateral or bilateral dilated, nonreactive pupils.Asymmetric pupils.Decerebrate posturing.No motor response to painful stimuli.
85Assessment/Treatment Monitor SpO2 and ETCO2.Maintain SpO2 > 90%Maintain ETCO2 between mm HgInitiate IV line with saline:Maintain adult systolic BP > 90 mm HgPediatric values are lower.Utilize Glasgow Coma Scale
86Glasgow Coma Scale (Adult) Eye Opening (E)Verbal Response (V)Motor Response (M)Obeys (6)Oriented (5)Localizes (5)Spontaneous (4)Confused (4)Withdraws (4)Reaction to Speech (3)Inappropriate Words (3)Decorticate (3)Reaction to Pain (2)IncomprehensibleSounds (2)Decerebrate (2)No Response (1)TOTAL = E + V + M
87Glasgow Coma Scale (Infant) Eye Opening (E)Verbal Response (V)Motor Response (M)Obeys (6)Coos, Babbles (5)Localizes (5)Spontaneous (4)Irritable Cry (4)Withdraws (4)Reaction to Speech (3)Cries to Pain (3)Decorticate (3)Reaction to Pain (2)Mans, Grunts (2)Decerebrate (2)No Response (1)TOTAL = E + V + M
89Treat Airway Protect C-spine alignment, consider facial trauma. Airway support per scope of practice.Intubate severe TBI patients.Correct hypoxia.
90When to Intubate GCS < 9 (severe TBI). All patients with respiratory failure of apnea.
91Treat Breathing Oxygenation. Ventilation. Administer supplemental oxygen by non-rebreather or BVM as appropriate.Ventilation.Assess rate, depth, quality, to determine the effectiveness of respirations.As necessary, assist ventilations with BVM and supplemental O2.
92Adult normal Ventilation rate = 10-12 per minute Treat BreathingAdult normalVentilation rate=10-12 per minute
93Hyperventilation? Hyperventilation: Rapid PaCO2Cerebral vasoconstrictionDecreased CBF ICPBut, hyperventilation can CBF to the point of ischemia.Monitor ETCO2!
94Hyperventilation?Potential harm in patients without evidence of brain herniation.Short-term measure used in specific TBI patients (herniation) until definitive diagnostic or therapeutic can be provided.
95Hyperventilation? Rates: Ages 9-Adult: 20 breaths per minute: (ETCO2 ~ 35 mm Hg).Ages 1-8 years: 30 breaths per minute:(ETCO2 ~ mm Hg).Ages < 1 year: 40 breaths per minute:
96Fluids Fluids to maintain SBP> 90 mm Hg. Normal saline Hypertonic saline?
97Brain-Targeted Therapies Glucose for hypoglycemiaSedatives for agitationAnalgesics for painParalytics for ET intubationControversial:MannitolLidocaineHypertonic Saline
98Destinations Mild (GCS 14-15): Emergency Department Moderate (GCS 9-13): Trauma CenterSevere (GCS < 9): Trauma Center with severe TBI management capabilities.
99Take Home Messages Clinical practice should be evidence-based. Do early and repeated neurological assessments.Identify patients with severe TBI (GCS < 9).
100Take Home Messages Avoid hypoxia, keep SpO2 > 90%. Avoid hypotension, keep SBP > 90 mm Hg.Hyperventilate only for clinical signs of herniation.Triage and transport TBI to appropriate facilities based on severity.
101The Future Therapies to protect against secondary injury: Hypothermia. Sedative-induced coma.Metabolic therapies.Antioxidant therapies.