Neuroanesthesia

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Neuroanesthesia
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Brain Tumors

• Primary
• Benign Malignant
• Meningioma Glioblastoma
• Pituitary adenoma Medulloblastoma
• Astrocytoma
• Acoustic neuroma

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Increased Intracranial Pressure (ICP)Symptoms

1. Headache
2. Nausea vomiting
3. Paresthesias
4. Somnolence
5. Visual, auditory disturbances
6. Mental aberrations

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Increased Intracranial Pressure (ICP)Signs

1. Hypertension
2. Bradycardia
3. Periodic breathing
4. Seizures
5. Midline shift on computed tomography

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Evidence of Brain Herniation

1. Dilated and unreactive pupil
2. Contralateral hemiplegia
3. Loss of responsiveness
4. Ataxic breathing or apnea

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Continuous ICP Monitoring Causes of a Plateau
Wave

• (Increase above 15 mm Hg)
• Anxiety
• Pain
• Intubation

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Methods to Decrease Intracranial Pressure

1. Posture
2. Hyperventilation (PaCO2 25-30 mm Hg)
3. Cerebrospinal fluid drainage
4. Hyperosmotic drugs (mannitol 0.25-1.0 g/kg IV)
5. Diuretics (furosemide 1 mg/kg IV)
6. Corticosteroids
7. Barbiturates

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Effects of Anesthetic Agents onCerebral Blood
Flow (CBF)

• Increase
• Halothane gt desflurane gt isoflurane
• Succinylcholine, atracurium (histamine release)
• Decrease
• Barbiturates (also etomidate, propofol,
  midazolam)
• Opioids

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Anesthetic Management of the Patient with
Increased ICP

1. IV induction if possible
2. Non-depolarizing muscle relaxant
3. Mechanical hyperventilation
4. Adequate anesthesia paralysis before intubation
5. Fluid therapy 5 glucose in LR vs. NS
6. 1-3 ml/kg/h (avoid D5W)

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Special Monitoring of the Patientwith Increased
ICP

1. Intra-arterial BP
2. Capnography
3. Intracranial pressure
4. Right atrial catheter
5. Doppler transducer

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Detection of Venous Air Embolism

1. Doppler transducer (mill-wheel sound)
2. Sudden decrease in end-tidal CO2
3. Increase in RA and PA pressures
4. Increase in end-tidal N2
5. Sudden attempts to breathe (gasp reflex)

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Treatment of Venous Air Embolism

1. Occlude venous air entry site
2. Aspirate air via right atrial catheter
3. Discontinue N2O
4. Cardiovascular support if required

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Post-Craniotomy Management

1. Prevent reaction to tracheal tube (lidocaine
   1mg/kg IV)
2. Delay extubation until protective throat reflexes
   return (normothermia, adequate spontaneous
   ventilation)

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Carotid EndarterectomyPreoperative Evaluation

1. Ischemic heart disease
2. Range of blood pressure readings
3. Effects of changes in head position

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Carotid EndarterectomySpecial Monitoring

1. Electroencephalogram
2. Somatosensory evoked potentials
3. Stump pressure gt 60 mm Hg probably
   reflects adequate blood flow

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Carotid EndarterectomyPostoperative Problems

1. Blood pressure instability
2. Airway compression (hematoma)
3. Loss of carotid body function
4. Myocardial infarction
5. Stroke
6. Peripheral nerve damage (facial, recurrent
   laryngeal)

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StrokeSymptoms Signs

• Headache and
• Vomiting
• not characteristic of stroke due to systemic
  hypoperfusion
• Loss of consciousness
• Seizures

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Resection of Intracranial Aneurysm

1. Preoperative evaluation mental status, elevated
   ICP
2. Induction of anesthesia minimize pressor
   response to intubation
3. Maintenance potent volatile agent
4. Controlled hypotension
5. Monitor BP accurately (transducer at level of
   circle of Willis)

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Resection of Intracranial AneurysmControlled
Hypotension

1. Nitroprusside (0.5 - 3.0 mcg/kg/min) use
   infusion pump, monitor with arterial line
2. Esmolol available for treatment of reflex
   tachycardia
3. Maintain CVP lt 10 mm Hg
4. Maintain PaCO2 around 35 mm Hg

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Acute Head TraumaPreoperative Evaluation
Preparation

1. Assess other injuries
2. Immobilize cervical spine
3. Establish a patent airway
4. Intubate if necessary to prevent aspiration
5. Performance of CT scan

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Glasgow Coma Scale (1)Eye Opening Response

• Score
• Spontaneous 4
• To speech 3
• To pain 2
• Nil 1

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Glasgow Coma Scale (2)Best Motor Response

• Score
• Obeys 6
• Localizes 5
• Withdraws (flexion) 4
• Abnormal flexion 3
• Extensor response 2
• Nil 1

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Glasgow Coma Scale (3)Verbal Response

• Score
• Oriented 5
• Confused conversation 4
• Inappropriate words 3
• Incomprehensible sounds 2
• Nil 1

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Glasgow Coma Scale

• Definition of Coma 8 or less
• mortality or persistent vegetative state 50
• Common definition of unconsciousness failure
  of rational response to verbal command

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Acute Head Trauma

• Epidural hematoma
• Skull fracture with rupture of a meningeal artery
• Initial loss of consciousness followed by lucid
  interval
• Treatment burr holes
• Subdural hematoma
• Often due to bleeding from a bridging vein
• May follow trivial head trauma, especially in
  elderly
• Symptoms signs evolve gradually
• Treatment surgical evacuation

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Drugs to be Avoided in Selected Neurologic
Diseases

1. Amyotrophic lateral sclerosis succinylcholine
2. Parkinsonism antidopaminergic drugs
3. (antipsychotics, droperidol, metoclopramide)
4. Alzheimers disease sedatives, centrally acting
   anticholinergics ( scopolamine)
5. Multiple sclerosis succinylcholine

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Multiple SclerosisAnesthetic Considerations

1. Patients may be on large doses of corticosteroids
2. Susceptibility to stress (hypotension)
3. Susceptibility to temperature change
4. Drugs that may be required steroids,
   dantrolene, carbamazepine
5. Avoid spinal anesthesia

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Neuropathies (1)Cranial Mononeuropathies

• Idiopathic facial paralysis (Bells palsy)
• Can be caused by excessive mandibular extension
• Treatment prednisone
• Trigeminal neuralgia (tic douloureux)
• Treatment carbamazepine, surgery,
  radiofrequency destruction of V fibers (may cause
  hypertension)
• Glossopharyngeal neuralgia
• May be accompanied by severe bradycardia
• Treatment topical anes. of oropharynx,
  anticholinergics
• Transvenous cardiac pacemaker may be required

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Neuropathies (2)Peripheral

• Entrapment i.e carpal tunnel
• Metabolic i.e alcohol, B12 deficiency, diabetes,
  hypothyroidism, uremia, porphyria
• Systemic disease-related cancer, sarcoidosis,
• collagen-vascular disease, Guillain-Barre
• Toxicities anticancer drugs, poisons,insecticide
  s
• Hereditary peroneal muscular atrophy, others

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NeuropathiesAnesthetic Considerations

• May be due to nerve compression (e.g., ulnar
  nerve) or hyperextension (e.g., brachial plexus)
• Neuropathies due to disease, drugs, or toxic
  substances are usually bilaterally symmetrical

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Guillain-Barre Syndrome(Acute Idiopathic
Polyneuritis)

1. Respiratory insufficiency
2. Impaired cardiovascular compensatory responses
3. Exaggerated vasopressor drug responses
4. Hyperkalemic response to succinylcholine

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Spinal Cord TransectionChronic Manifestations

1. Painful muscle spasms
2. Sensory disturbances
3. Sympathetic overactivity
4. Chronic infections (pulmonary, genitourinary)
5. Altered thermoregulation

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Drugs for Seizure Disorders

• Partial (focal) seizures
• Valproic acid, carbamazepine, phenytoin
• Generalized
• Absence Valproic acid, ethosuximide
• Myoclonic Valproic acid
• Continual (status epilepticus)
• Diazepam, phenytoin, carbamazepine, valproic acid

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Treatment of a Grand Mal Seizure

1. Establish patent upper airway
2. Administer oxygen
3. Diazepam (2 mg/min IV, max, 20 mg)
4. Phenytoin (50 mg/min, max 1 - 1.5 g)
5. General anesthesia (infants children,
   refractory cases)
6. Respiratory circulatory support (for post-ictal
   depression)

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Drugs to be Avoided in Patients with Seizure
Disorders

1. Methohexital
2. Ketamine
3. Enflurane
4. Atracurium (laudanosine effect)

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Perioperative Headache

1. Caffeine withdrawal
2. Migraine
3. Cluster headache (histamine cephalalgia)
4. Increased intracranial pressure
5. Benign intracranial hypertension (pseudotumor
   cerebri) lumboperitoneal shunt
   contraindicates spinal anesthesia

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Abnormal Patterns of Ventilation

• Symptom
• Ataxic (Biots breathing)
• Apneustic breathing
• Cheyne-Stokes breathing
• Central neurogenic hyperventilation
• Posthyperventilation apnea

• Site of lesion
• Medulla
• Pons
• Cerebral hemispheres
• Hypoxic states (CHF)
• Cerebral thrombosis or
• embolism
• Frontal lobes