Martin Young DVM , MS, DACVIM Mike Higginbotham, DVM, DACVIM Blackwater Falls • • • Common causes Pathophysiology Presenting signs • • Hit by automobile Falls Stairs • • • Kicks Penetrating wounds Bites • Primary injury – initial insult. Function of trauma and forces. Linear, rotational Coup vs counter coup www.mdusd.k12.ca.us • Concussion Brief loss of consciousness • Contusion Bruising of parenchyma and secondary edema • Tissue laceration Physical disruption of the parenchyma • Intra-axial and extra-axial hematomas • Secondary injury cascade of biochemical pathways initiated which lead to further brain injury and increased intracranial pressure (ICP). • Edema •Vasogenic and cytotoxic vicious cycle of tissue damage • Occurs minutes to hours after initial insult • Series of events that perpetuate and initiate cellular damage • Driven primarily by cerebral ischemia Hypotension, hypoxia, and perfusion • Hypotension, hypoxia, and perfusion • ATP depletion • Na+ and Ca++ influx • Cytotoxic edema Other cascades Depolarization Glutamate Platt & Olby. BSAVA Manual of Canine and Feline Neurology • Pressure autoregulation • Chemical autoregulation PaCO2 • Intracranial compliance Monroe-Kelly Doctrine • CPP = MABP – ICP Pressure MABP Volume • Epidural • Subdural / subarachnoid • Parenchymal Subdural / Subarachnoid T2 image FLAIR Herniation Head Trauma Assessment Looking for head trauma • • • • • • 25% of trauma patients have head trauma MGCS – only evaluates BS function PTE is a common cause of epilepsy 6.8% 36% of head trauma patients had seizures DWI - hemorrhage detected by 30 min MRI is useful for prognostication Step 1: • Focus on ABC’s • Correct hypoxia and hypotension first, will help the brain as well as the rest of the patient and will allow you to better assess your patients neurological status • Baseline labwork: PCV, TS, CBC, Chem, Urinalysis, and Wt. • Can’t accurately assess the mentation of a shocky patient! Postures and respiration • Postures: decerebrate vs decerebellate vs schiff sherrington • Respiration: Cheyne-Stokes – deep cerebral and rostral BS –rapid breathing followed by apnea Central hyperventilation – 25/min – regardless of CO2 content – midbrain to Pons Irregular gasping – caudal BS - terminal • Gait and Posture Paresis, circling, paralysis Normal, opisthotonus, decerebrate rigidity • Mental status Bright, depressed, stuporous, comatose • • Vestibular signs Pupils Size, symmetry, response to light Decerebrate rigidity Step 2: • Part 1 complete. Patient is normovolemic and normotensive and we have established appropriate oxygenation and ventilation • Assess the rest of the patient: Nervous system, vertebral fractures/ luxation, lungs, abdomen, musculoskeletal • Additional Diagnostics: Radiographs: skull, abdomen, thorax Additional bloodwork if indicated MRI/CT, electrodiagnostics Modified Glasgow Coma Scale • Published in a 2001 JVIM article by Dr. Simon Platt • Evaluates the patient using 3 criteria and assigns a severity score from 1-6 to each: Level of Mentation Motor Function Brainstem Reflexes • Score assigned from 3-18; higher the score, better prognosis Basic Levels of Mentation • Bright, alert, responsive • Obtunded Dull, depressed but responsive to all manner stimuli • Semi-coma responsive to stimuli • Stuporous responsive only to noxious stimuli • Comatose unconscious, non-responsive to any stimuli MGCS: Levels of Mentation • 6 - BAR or intermittent periods BAR • 5 – obtunded – clouded consciousness • 4 – semi-coma - responsive to visual stimuli • 3 – semi-coma - responsive to auditory stimuli • 2 – stuporous – responsive to vigorous stimulation • 1 - comatose LOA Brain Stem Reflexes • 6 - Normal PLR and oculocephalic reflex (OcR) • 5 - Slow PLR, normal to slow OcR • 4 - Bilateral unresponsive miosis, normal to slow OcR • 3 - Pinpoint pupils, reduced to absent OcR • 2 - Unilateral, unresponsive mydriasis, reduced to absent OcR • 1 - Bilateral, fixed dilated pupils Pupil Chart De Lahunta - Vet Neuroanatomy Oculocephalic Reflex • AKA - conjugate eye movements • Pathway between the vestibular system and the extraocular muscles to coordinate eye movements • Pathway travels through the central brainstem in the medial longitudinal fasciculus before connecting with CN III, IV and VI and exiting the brainstem • Loss of oculocephalic reflex = Poor Prognosis Denotes severe brainstem damage MGCS: Motor Assessment • 6 - Normal gait, normal spinal reflexes • 5 - Hemiparesis, tetraparesis • 4 - Recumbent, intermittent extensor rigidity • 3 - Recumbent, constant extensor rigidity • 2 - Recumbent, constant extensor rigidity w/ opisthotonus (decerebrate rigidity) • 1 - Recumbent, hypotonia of muscles, depressed/absent spinal reflexes MGCS Score • Now, have your MGCS score, what does it mean? Score 15-18: Good prognosis Score 9-14: Guarded prognosis Score 3-8: Grave prognosis • A linear association between score during first 48 hours and patient overall prognosis • Score = 8 in the JVIM paper resulted in 50% mortality Cushing Reflex • KEY: Decreased mentation, high systemic MAP, low heart rate suspect high ICP Increased ICP results in decreased CBF which regionally increases CO2 concentration High CO2 sensed by vasomotor center in the brain and triggers a massive sympathetic discharge resulting in a peripheral vasoconstriction Result is a rise in MAP to maintain CPP Activates baroreceptors creating the reflex bradycardia Forebrain • • • • • • • Can have fewer signs Seizures Menace deficit Behavior changes Sensory/proprioceptive deficits (contralateral) Large circles to the lesion Altered homeostasis (temperatue, heart rate, blood pressure) Imaging • Radiographs Unlikely to reveal additional clinically useful information but may show depressed skull fractures • Presence of a skull fracture has not been shown to be a negative prognosticator • Often, CT or MRI warranted to assess for severity of injury, hemorrhage, and herniation Head Trauma Treatment Treating the Head Trauma Patient • Therapeutic Options: Mannitol/hypertonic saline Fluids Anticonvulsants Antibiotics Steroids? Oxygen Nutrition Analgesia Patient care Mannitol: MOA Osmotic diuretic: decreases vasogenic cerebral edema and decreases ICP Reflex cerebral vasoconstriction as a result of decreased blood viscosity Free-radical scavenger Improves microvascular flow; shrinks RBCs by 15% and improves deformation and cell wall flexibility hence improving tissue oxygenation Hypertonic saline MOA • Osmotic draw: pulls fluid from interstitial and intracellular space • Improves: MAP, CBP and CBF • Volume expansion: not used in dehydration or hypernatremia. • Can cause vago-reflex – may need atropine Mannitol/hypertonic saline • Indications: Clinical indication of increased ICP Progressive decline in neurological status Cushing’s reflex • Dose: • mannitol 1 to 1.5 g/kg IV over 20 minutes • Hypertonic saline 3-5 ml/kg over 10 minutes • Effect • Mannitol max effect in 20 min last 2-5 hrs repeat q6-8 • Hypertonic saline max effect in minutes, last 1 hour Mannitol/hypertonic saline • Do not give if dehydrated/volume depleted • Monitor electrolytes • Monitor weight/hydration • No hypertonic saline if hypernatremic Maintain Oxygenation • Evaluate mucous membrane and tongue color, respiratory rate, pattern and thoracic auscultation Arterial Blood Gas: PaO2 > 90 mmHg Pulse Oximetry: Maintain SpO2 > 95% • Provide supplemental oxygen Flow-by or mask oxygenation or tent O2 cage does not allow frequent patient assessment Nasal O2 - avoid sneeze induction which increases ICP Intubation / Ventilation No Corticosteroids • Are contra-indicated in both veterinary and human medicine for the treatment of head trauma. • All studies show either no improvement or a worsening of the outcome • Commonly associated with iatrogenic hyperglycemia and worse prognosis • Does not help with cytotoxic edema only vasogenic edema • Promote anaerobic metabolism – increase lactate • Increase glutamate levels and neuronal death. Hyperglycemia and Head Trauma • Hyperglycemia > 200 mg/dL has been associated with increased mortality in severely brain injured people • JAVMA, 2001 paper positively correlated degree of hyperglycemia with severity of brain injury Paper failed to correspond to overall patient prognosis but parallels human papers which correlated higher BG with lower GCS score • Current guideline: Avoid iatrogenic elevation of blood glucose Analgesia • Ideal Analgesic Agent that provides pain relief without inducing respiratory depression or hypotension • Options: Opioids – fentanyl Benzodiazepines (reduce anxiety, muscle relaxation) Alpha-2 agonists NSAIDS Gabapentin Fluid Resuscitation • Goal is to restore normovolemia and normotension • Fluid Choices: Crystalloids - 90 ml/kg/hr Colloids e.g. hetastarch - 10-20 mL/kg to effect Hypertonic saline - 4-5 mL/kg over 3-5 minutes Blood products if indicated • No one fluid proven to be better than another, important point is to give to effect, don’t want to create hypertension! • Ideal MAP = 70 - 90 mmHg, remember, CPP = MAP – ICP! (Minimum CPP 70 mmHg) Monitoring • Serial neurological exams necessary as the patient will change, better or worse every 1-2h depending on patient • Continuous BP, ECG and O2 monitoring recommended • Serial ABG indicated if patient having difficulty breathing appropriately to determine if ventilation is needed • Monitor electrolytes, PCV/TS and weight twice daily Supportive Care • • • • • • • • • • Circulatory support Oxygenation Analgesia Padded bedding Rotate patients Elevation of the head 15-30° above the heart Lubricated eyes to prevent ulceration Nutrition Anticonvulsants if indicated Avoid jugular compression • Not just an auditory test • Can be a useful assessment of brainstem function Normal Brainstem damage Electroencephalogram Sequella • Behavior changes • Post traumatic epilepsy (weeks to years) • Persistent deficits • Ventricular anomalies Post trauma Conclusions • With time and good supportive care, many head trauma patients can do quite well • Most important aspect in management is maintaining good MAP and oxygenation References • • • • • • • • Dewey, CW. Emergency Management of the Head Trauma Patient. Veterinary Clinics of North America: Common Neurological Problems. 2000: 207-25. Syring RS. Hyperglycemia in dogs and cats with head trauma: 122 cases (1997-1999). JAVMA. 2001; 218(7): 1124-29. Syring RS. Assessment and treatment of CNS abnormalities in the emergency patient. Vet Clin Small Anim. 2005; 35: 343-358. Platt SR. The Prognostic Value of the Modified Glasgow Coma Scale in Head Trauma Dogs. JVIM. 2001; 15: 581-84. Armitage-Chan EA. Anesthetic management of the head trauma patient. JVECC. 2007; 17(1):5-14. Kalita J. Current Status of osmotherapy in intracerebral hemorrhage. Neurology India. 2003; 51(1): 104-9. Oliver and Lorenz. Handbook of Veterinary Neuroanatomy. DeLahunta A. Veterinary Neuroanatomy and clinical neurology. Saunders Elsevier. 2009.