Head Trauma in Anesthesiology
Jamison Elder MD Dept. Anesthesiology
Objectives:
Timely Informative Practical Enjoyable
Lecture Information
Board Review Sources
– – – – – – Sdrales & Miller, Anesthesia Review, 1st Ed Faust, Anesthesiology Review, 3rd Ed Morgan & Mckahil, Anesthesiology, 3rd Ed Roizen, Essence of Anes Practice, 1st Ed Derchwitz, MGH Board Review Anes, 5th Ed Hall, Anesthesia Comprehensive Review, 2nd Ed
Head Trauma
Epidemiology
Epidemiology Head Trauma
Epidemiology
– 500,000/yr – 30y/o, 2M:1F – Mortality (40%)
15% Field 25% Hospital
– Morbidity (40%)
40% CNS Disabled
– Full Recovery (20%)
Mortality
Morbidity
Recovery
Epidemiology Head Trauma
Injury Type
– Diffuse Lesion 48% – SDH 24% – EDH 3%
91% Skull Fx
Diffuse Lesion EDH DAI
SDH ICH
– ICH 6% – DAI 3%
Head Trauma
Types
Head Injury
Head Injury
– Types? – Hallmark? – CNS Measure? – Imaging?
Types: Closed Head Injury
Diffuse Axonal Injury Subdural Hematoma Epidural Hematoma
Types: Head Injury
OPEN Head Injury
– Dura OPEN
ICP = 0 CPP = MAP - CVP
CLOSED Head Injury
– Dura CLOSED
ICP > 0 CPP = MAP - ICP
Hallmarks: Closed Head Injury
Hallmark of CHI?
LOC LOC ≅ Severity
S/Sxs ⇑ ICP:
N/V/HA MS changes Ataxia Seizure Coma Death
Head Trauma
Measures
Measures: Head Injury
Measures of Injury
– LOC – GCS – ICP
Bolt Epidural Sub-dural Intra-ventricular
– Imaging
CT (1st line)
GCS
CT
Measures: Glasgow Coma Scale
Eye Opening (4 eyes)
4 Spontaneous 3 Verbal 2 Pain 1 None
Motor (Six Shooter)
6 Verbal 5 Localize 4 Flexion/Withdrawal 3 Decorticate (Flex) 2 Decebreate (Ext) 1 None
Verbal (Best Response)
5 Oriented 4 Disoriented 3 Inappropriate 2 Incomprehensible 1 None
Measures: Glasgow Coma Scale
Useful GCS Values
– – – – <8 ≅ 35% Mortality < 8 ≅ Intubation >12 ≅ Local/MAC? <12 ≅ GETA
Measures: Closed Head Injury
CT Findings ⇑Morbidity
– – – – >5mm Midline Shift >25cc Lesion DAI Pattern Herniation
Physiology Head Trauma
Intracranial HTN CBF Autoregulation Cerebral Ischemia Pharmacology
Head Trauma
(ICP) Intracranial Pressure
Physiology in Head Trauma
ICP Components
– – – – – – CSF 5-15% Blood 3-5% Brain 80-85% ≅ Na ⇑ Mg, Cl ⇓ Colloid, K, Ca
CSF Composition
Physiology in Head Trauma
Intracranial Compliance
– Fixed Box – Monro-Kellie Hypothesis
ICP Buffer System
– – – – 1st CSF Translocation 2nd CSF ⇓net production 3rd Blood Translocation 4th Brain Herniation
Physiology in Head Trauma
ICP Values
– – – – Nml < 15 Abnml > 20 Reversible ≅30-40 Irreversible >60
⇓ Compliance
– Cardiac Oscillations – Plateau Wave
Head Trauma
Physiology
Physiology in Head Trauma
CBF Autoregulation
– Definition? – Mechanism? – Influences? PaCO2 PaO2 CMR ∆P (MAP, ICP) Rx (Pharm)
Physiology in Head Trauma
CBF Autoregulation
– Normal:
CPP 50-150 PaCO2 ≅40 Pa02 >50
– Shifted Leftward
Chronic HTN (1-2mo) +/- 20% MAP
– Extremes
MAP drives CBF
Physiology in Head Trauma
CBF Influences
– PaCO2
Most Influential
– 20-80mmHg
Hyperventilation
– Best @ 25-30 – Worst @ <20
– PaO2
>60 mmHg Wnl <50 mmHg Abnml Associated Injury
Physiology in Head Trauma
CPP PaCO2
PaO2
Comparison:
CPP PaCO2 PaO2
250 200 150 100
PaO2
50
PaCO2 CPP
0
25
50
50 100 150 200
0
Physiology in Head Trauma
CMR02 60% 40% CBF Influences:
– Temperature ∝ CMR02
60% Functional CMR
– TEMP & Rx
40% Basal CMR
– TEMP
– CMR02
Demand = 3-4cc/100g/min Supply = 50cc/100g/min No stored reserve of 02 ⇓⇑CMR 7% ≅ ⇓⇑ 1 C TEMP
Physiology in Head Trauma
Hypothermia & Ischemia
Temp Fxnl CMR Basal CMR Time 37 C 60% 40% 5min 27 C 17 C 25% 0% 16% 8% 60min 60
40 20 0 37 C
Ischemia (min) Fxnl CMR Basal CMR
27 C 17 C
Basal CMR
Fxnl CMR
Ischemia (min)
Michenfelder, The Awake Brain, 1988
Head Trauma
Pharmacology
Pharmacology Head Injury
Rx Influences on CBF:
– Nitrates (SNP) – Volatiles (HAL, ENF) – Hypnotics
STP Ketamine
– MISC.
Nitrous Oxide Droperidol + Fentanyl
Pharmacology Head Injury
NITRATES (SNP):
– Vasodilator – ⇓ CPP – ⇑ ICP – Rebound HTN – Toxicity
Bolus 0.5mg/Kg/hr Gtt 0.5mg/kg/24hr
Cottrell, J. Neurosurgery, 48:329, 1978
CPP w/ Induced Hypotension by SNP
120 100 80 CPP 60 40 20 0
MAP ICP CPP
No SNP
No SNP
SNP
SNP
Pharmacology Head Injury
Volatile Agents:
– “Uncoupling Effect”
⇓ CMR & ⇑ CBF
– Critical CBF
ISO>>HAL>>ENF
– Halothane
Potent C. Vasodilator ⇓ MAP (⇓CO & ⇓SV)
– Enflurane
Net ⇑ CSF
Pharmacology Head Injury
(STP) Na Thiopenthol:
– Mechanism: (⇑GABA) – Indications:
Direct Vasoconstriction ⇓ CMR02 Focal >> Global Injury
– EEG:Burst Suppression:
Suppressed 30mg/Kg Slowed 5-10mg/Kg
– Side Effects:
⇓ MAP (⇓SV & ⇓CO) Cloud Neuro Exam
– NOT Impair CBF or PaCO2
Pharmacology Head Injury
Lidocaine/Propofol/Etomidate
– Vasoconstriction – ⇓ CMR02
Ketamine (⇑SNS)
– Vasodilator – ⇑ CMR02
Nitrous Oxide
– Vasodilator (weak)
Opiods
– No Effect
Droperidol + Fentanyl
– ⇓ CMR02 (weak)
Head Trauma
Cerebral Ischemia
Cerebral Ischemia Head Trauma
Mechanism:
– CPP = MAP - ICP
ICP (IC HTN) CVP (CHF) MAP (Hypotension)
Cerebral Ischemia Head Trauma
⇑ ICP S/Sxs:
– – – – – – – N/V HA MS Changes Ataxia Seizure Coma Death
Cerebral Ischemia Head Trauma
Succinylcholine & ⇑ICP:
– – – Mechanism: Fasciculations Dose: 1.6mg/Kg Transient Effects:
1mg/Kg = ⇑ICP 5-10mmHg Cough = ⇑ICP 20-40mmHg
– ⇑ICP Blunted by:
10% NDNMJB STP (3-5mg/Kg IV) Volatile (>1MAC)
– “ABC before G”
Cerebral Ischemia Head Trauma
Dextrose IVF:
– Anaerobic Glycolysis – Free Water – Neurotoxic
Contraindicated!
Cerebral Ischemia Head Trauma
Positioning:
MAP @ Circle of Willis (ear) Feet = Heart Neck Flexion Venous Obstruction
Cerebral Ischemia Head Trauma
Corticosteroids:
– Mechanism???
Stable Membranes (BBB) ⇓ CSF Production
– Indications:
Yes - Spinal Cord Edema (Focal) No - Cerebral Edema (Global)
Dexamethasone & Methylprednisolone
– Side Effects:
Adrenal crisis
Cerebral Ischemia Head Trauma
Optimal Mgmt:
– 1st ⇑ CPP
⇑ MAP ⇓ ICP ⇓ CMR
– 2nd Reverse Etiology – 3rd Neuro-Protection
Cerebral Ischemia Head Trauma
CPP Calculations:
– – – Normal > 60 mmHg MAP @ Cir. of Willis CPP = MAP – (ICP or CVP)
Dura OPEN CVP Dura CLOSED ICP 20% Baseline MAP
MAP CPP ICP or CVP
Cerebral Ischemia Head Trauma
Neuro-Protection:
– 1st CPP Optimized
⇓ICP & ⇑MAP
– 2nd ⇑Pa02
Fi02 & Hgb
– 3rd PaCO2
Hyperventilation
– 4th ⇓CMR02
STP Temperature
– 5th Free Radical Scavenger
Mannitol
Cerebral Ischemia
Mannitol:
– Mechanism: Osmotic Diuretic – Dose: 0.25-1.0g/Kg/4hr
Ceiling Effect VS Clinical response
– Derangements (>2g/Kg):
Early: ⇑Volume (CHF) Late: ⇓Volume, ⇓K, ⇑Na SDH (Elderly) +/- Cerebral edema (BBB) IVF (1:1 UO w/ IsoCx) Electrolyte Prn
Bridging Vein
Head Trauma
Peri-Operative Concerns
Peri-Op Head Trauma
Co-Existing Disease:
– Geriatrics
Cortical Atrophy ⇒ SDH
– Cardio/Pulmonary
COPD, OSA CAD, CHF, EKG ∆s
– PVD
CVA (<4-6wks) ICA Bruit (60% Asx Stenosis)
– DM – CRI
Peri-Op Head Trauma
Anesthetic Concerns:
– Airway Mgmt
Full Stomach Difficult Airway
– Intracranial HTN – Emergence Based
Pre-Medication Intra-Op Exam Post-Op Exams
“Yep, Dr Elder! You sure did! That’s enough exercise for today.”
Associated Injuries of CHI
Associated Injury:
– – – C-Spine Fx (10%) Basilar Skull Fx SNS Surge Injury
EKG ∆s (injury) Pulmonary Edema (V/Q Mismatch)
– Shock
Peri-Op Complications
Peri-Op Complications
VAE Shock/Anemia Inflammatory
– Coagulopathy/DIC/SIRS/ARDS
(DI) Diabetes Insipidus Hyperosmolar Non-ketotic Coma Basilar Skull Fx Vasospasm Sitting Craniotomy
– Pneumocephalous – Nerve Injury – VAE
Autonomic Hypereflexia
Peri-Op Complications
(VAE) Venous Air Embolism:
– Risk: Head Up >5° – SXs: murmur, arrhythmia, ⇓BP, ⇓PaCO2,
⇓02sat, ⇑PaN2
– Monitors:
TEE(0.01cc)>>PCD(0.5cc)>>PAP>>etN 2=etCO2>EKC>Auscultation
– Tx:
Notify Surgeon Flood Field Head down IJ Compression Volume & Ionotropy Air Aspiration
VAE Detectors
Increasing Sensitivity Rate of Air Entrapment (cc/Kg/min)
Rusner, Head Trauma - Origin and Evaluation of Plateau Wavews J. Neurosurg 60: 312-324 1984
Peri-Op Complications
Sitting Craniotomy:
– Nerve Injury
C-Spine Sciatic Pernoneal/Ulnar
– Airway Edema
Venous Egress
– Pneumocephalous
MS∆s, HA Tension (N20)
– VAE
Peri-Op Complications
Autonomic Hypereflexia
Why? Dysfunctional SNS Response When? >4-6wks s/p spinal shock Where? T10 Unlikely)
– Sxs:
Early: Pulm Edema, ⇓SVR Late: HTN, Bradycardia, LV Dysfxn, Poikilothermia, Vasodilate >lesion Cutaneous or Visceral Stimulation I wish my Brain could see this?
⇑SVR ⇑SVR
– Tx:
Pentolamine (α1 Antagonist) Trimethaphan (Ganglion (SNS) Blocker) β-Blockers Avoided (Unopposed α1)
⇑HTN ⇑HTN
Vasodilate Rhinorrhea
Peri-Op Complications
Vasospasm s/p SAH:
– Hallmark:
New MS∆s or LOC POD 4-14
– Imaging:
Severity ∝ Vol. of Blood Angiographic Signs 70% Clinical Sxs 20-30%
– Tx:
Triple “H” Therapy Nimodipine Angioplasty
Peri-Op Complications
Diabetes Insipidus:
– Mechanism:
⇓⇓⇓ ADH Pituitary Injury
– Treatment:
DDAVP
– 5-10mg Nasal Spray bid
– 2 mcg SQ or IM q12h
– Dx:
Polyuria (>3-4cc/kg/hr)
– No Glucosuria
Vasopressin
– 5-10U SQ q4hr
⇓Uosm (<1.005) ⇑Sosm (>300)
– Mgmt:
UO Replacement Free Water Deficit
Peri-Op Complications
Brain Death (Definition = 3 Parts)
– 1. Cortical
Brain Dead?
Irreversible LOC No purposeful Motor Fxn
– 2. Brainstem
Irreversibly Loss of CN Reflexes
– Pupillary, Corneal, Oculovestibulo, Oropharyngeal, Respiratory
– 3. Study
No ∆ to Atropine No RR to PaCO2 >60 torr
No Mimics (Metabolic, Rx, Hypothermia)
Summary:
Board Review Material:
– – – – – – – – Demographics Types CHI CBF Autoregulation Cerebral Ischemia ICP Management Pharmacology Associated Injuries Complications
“Sorry, Dr. Elder, only senior management is allowed to go on the warpath”