Head trauma in small animal practice

Valérie Sauvé, DVM, DACVECCFifth Avenue Veterinary Specialists

September 2010

Traumatic Brain Injury

• Pathophysiology

• Patient evaluation

• Diagnostic work-up

• Therapeutic approach• Case example

Causes

Most common • Vehicular trauma • Crush injury

• High-rise or other falls• Trauma from animal / Human

Pathophysiology

• Primary brain injury – Impact / mechanical damage – Immediate and limited

• Secondary brain injury – Minutes to days after injury – Due to both systemic and intracranial causes

Primary brain injury

• Parenchymal damage– Contusion, hematoma, laceration– Diffuse axonal injury

• Vascular damage – Hemorrhage and vasogenic edema

• Axial vs extraxial hematomas– 10% Mild TBI– >80% Severe TBI

Secondary brain injury

• Neurotransmitters• Reactive oxygen

species • Pro-inflammatory

cytokines • Ischemia • ATP depletion • Intracellular Na / Ca• NO accumulation • Cerebral lactic acidosis

Result in • Neuronal cell damage

and cell death• Cerebral edema• ↑ ICP • Compromised BBB• Variation in

cerebrovascular reactivity

Systemic contributions

• Hypotension • Hypoxia• Hypo/hyperglycemia • Hypo/hypercapnea

• Hyperthermia • Electrolytes

imbalances • Acid-base imbalances

↓ CPP / CBF / oxygen delivery → Worsening brain injury

Monro-Kellie Doctrine

• 3 compartments contained in a rigid vault: – Brain parenchyma– Blood– CSF

• Intracranial compliance

• Autoregulation is limited – ↑↑ ICP → ↓ cerebral perfusion → ischemia

Pressure Autoregulation

Health • Systemic BP• Metabolic rate• Acid-base status TBI • Disruption of

autoregulation • ↑dependency on BP • Linear relationship

CPP = MAP – ICP>70mmHg 80mmHg <10mmHg

Cushing’s reflex

• ↑↑ ICP – Severe and life-threatening

• ↓CBF → ↑ CO2– Vasomotor center of brain

• Sympathetic response → vasoconstriction– ↑ MAP to ↑ CPP

• Baroreceptors in aortic arch and carotid arteries – Reflex bradycardia

High BP and low HR

Patient evaluation

• History

• Physical examination

• Triage / ABC - 4 vital organ systems – CV, Respiratory, Neurological…. Urinary

• Complete evaluation of the trauma patient– Thoracic radiographs, orthopedic injuries, etc

• Blood gas, BG, PCV/TS, electrolytes

• BP, HR, arrhythmia, breathing, SpO2, etc

Neurological assessment

• Complete neurological examination • Modified Glasgow coma scale

– Level of consciousness• Coma on presentation = guarded prognosis

– Motor activity • Opistotonos, rigidity • If decerebrate = poor prognosis

– Brainstem reflexes • PLR, pupil size• Herniation

Interpretation of pupil size / PLR Pupil size PLR Level of the lesion Prognosis

Midposition WNL Good

Bilateral miosis ↓ to none Variable

Unilateral mydriasis

↓ to none Cranial nerve III Guarded to poor

Unilateral mydriasis + ventrolateral strabismus

↓ to none Midbrain Guarded to poor

Midposition None Pons / Medulla Poor to grave

Bilateral mydriasis ↓ to none Poor to grave

Adapted from Fletcher DJ and Syring RS in Small Animal Critical Care Medicine 2009

Advanced imaging

CT / MRI

• No response • Worsening

• Moderate to severe signs on presentation

• Lateralizing signs

Cat brain imaging

Therapeutic approach

• Treat concurrent injuries / stabilize – Hypovolemia, hypoxemia and hypoventilation

• Maintain cerebral perfusion pressure CPP = MAP – ICP

• ↓ ICP • Control cerebral metabolic

rate

Fluids / Blood pressure

• First priority to restore systemic perfusion • MAP is a primary determinant of CPP

– MAP 80-100 mmHg or Doppler 100-120 mmHg

• Small boluses repeated – Crystalloids 20 ml/kg Cn / 10-15 ml/kg Fe– Colloids 5 ml/kg Cn / 3 ml/kg Fe

• Increased interest for hypertonic saline – Improves both systemic perfusion / BP and ↓ cerebral

edema – 4 ml/kg over 5 minutes (7% NaCl)

Respiratory considerations

• Prevent hypoxemia: > 90mmHg and CaO2– Erratic respiratory pattern – Pulmonary traumatic lesions – Associated with outcome

• O2 supplementation

• Prevent coughing, struggling, hyperthermia, anxiety and sneezing

Respiratory considerations• Monitor CO2 : CBF and CBV

– ↓ → vasoconstriction → ↓ CBF / ICP– ↑ → vasodilatation → ↑ ICP

• Gag reflex and intubation

• Consider mechanical ventilation – PaO2 < 60mmHg FIO2 60%– PaCO2 > 60 mmHg

• Consider before in TBI

– Apnea / WOB

Intern question !

Which of the following order is correct in a normal animal when comparing different ways to measure CO2?

A) ETCO2 > PvCO2 > PaCO2

B) ETCO2 < PvCO2 < PaCO2

C) ETCO2 < PaCO2 < PvCO2

D) ETCO2 > PaCO2 > PvCO2

Answer!

In a normal animal: C

• PvCO2 > PaCO2 by 2-5 mmHg

• ETCO2 < PaCO2 by 5 mmHg

Target in TBI PaCO2 35-40 mmHg PvCO2 40-45 mmHg

Mannitol First line • After volume repletion • 0.5 – 1.5 G/kg • Filter • Over 15-20 minutes • May repeat• Monitor hydration /

electrolytes

Contraindications: • Hypovolemia• Hypernatremia • Dehydration

Effects• ↓ICP, ↑CPP / CBF• ↑ Outcome

• ↓ Blood viscosity• Osmotic shift• Diuresis • Free radical scavenger

Other hyperosmotics and diuretics

Hypertonic saline • ↓ ICP and brain water content• ↑ CBF• ↓ brain excitotoxicity • Contraindicated if hyponatremic• Cardiac / pulmonary disease

Furosemide • No longer recommended

Glycemia

Hyperglycemia• Sympatho adrenal response • Potentiates brain injury

– ↑ Free radicals, excitatory aa, cerebral edema and acidosis – Alters cerebral vasculature

• Associated with severity of injury • Increased mortality / worse outcome (Hu/exp)

Corticosteroids

• Contraindicated

• Increased mortality in people

• Cause iatrogenic hyperglycemia, immune suppression, delayed healing, gastrointestinal ulceration, worsens catabolic state…

Other drug therapy?

Anticonvulsive• Prophylaxis ?

• Diazepam • Phenobarbitol

Barbiturates

• Last resort for ↑ ICP?

Other supportive care

• Pain – Opioids

• Elevate head/neck 15-30 degrees

• Avoid neck pressure / jugular occlusion

• Body temperature – Hypothermia? – Avoid Hyperthermia

• Turning / PROM / physical therapy

• Nutrition • Stress ulcers

– Famotidine / PPIs

• Prokinetic• Bladder/colon care • Other injuries

Surgical intervention?

• Rarely necessary or performed– Subdural hematoma– Depressed skull fractures– Expanding mass– Contaminated foreign body – Bite wounds

• Decompressive craniotomy

The Extraction of the Stone of Madness H. Bosch 1488-1516

I was rolled on…

DSH, 3-4 months, Fem History • Unclear accident with

a rocking chair, the owner is a little drunk

• T 95F• P 140 bpm• R 26 bpm• Pale mm, CRT 3 sec• No femoral pulses

palpable

Physical examination

• Lateral recumbency, covered in dried blood, abnormal mentation, anisocoria, no menace, head tilt and turn, epistaxis, PLR + OU

What will you do first?A) MannitolB) Recommend euthanasia C) IV fluid bolusD) Blood transfusion E) Skull radiographs

Emergency Treatment

• IVC / NOVA / PCV/TS / BP 50 mmHg • O2 mask• C) Delicate and progressive resuscitation

– Small crystalloid boluses with reevaluation• 10 ml/kg x 2 over 15 min = BP 72 mmHg

– NaCl 23.4 % + HES 6% (1:2) at 4 ml/kg

• Mannitol 0.5 G/kg – Once the BP has improved 100 mmHg

• Active rewarming – Baer Hugger

Continued Care

• Butorphanol IV • Oxygen mask • Elevated head/neck • Famotidine IV• Fluids maintenance • Follow BP • Clean and look for

wounds

• Complete orthopedic exam

• Thoracic radiographs • Turn q4hr• Recheck PCV/TS• Feed q4hrs kitten • Neurological status

monitoring

Progression

• BG: 278 mg/dL to 100 mg/dL • Improved neurological status within 1 hr• D/C O2 and BP monitoring the next day• No thoracic or orthopedic injury• Was bleeding from mouth and nose• Walking within 2 days.

• Home in 3 days!

Prognosis

• Do not get discouraged by appearance of patient on presentation

• Small animal patients have great capacity to compensate for loss of brain function

• Many pets will recover to be functional • Residual deficits

• Complications

Conclusion

• Very rewarding to treat !

• Treat early and aggressively!

Therapeutic summary

• Oxygen supplementation • Normotension • Normoglycemia • Maintain low normal CO2• Elevate head/neck 15-30 degrees • Supportive care and other injuries• Mannitol or Hypertonic NaCl; NO steroids

• Avoid jugular compression, sneeze/cough

Questions