ANESTHESIA IN PATIENT WITH HEAD TRAUMA

PREOPERATIVE MANAGEMENT

Initial resusitation:
-ensure patent airway
-assumed C-spine injury until radiographically proven otherwise
- in-line stabilization requirement: maintaining head in neutral position during airway manipulation
-adequate ventilation / oxygenation
-maintaining hemodyanamic stability

approximately 70% of head trauma patients have hypoxemia

Hypoxemia may be complicated by:
-pulmonary contusion
-fat emboli
-neurogenic pulmonary edema

Neurogenic pulmonary edema may result from:
-systemic hypertension
-pulmonary hypertension

Intubation
-patients with head trauma are considered ‘full stomachs’
-require cricoid pressure during ventilation and intubation
-thiopental 2 – 4 mg/kg or propofol 1.5 – 3 mg/kg
-muscle relaxant (short acting) although succinylcholine is controversial: may increase ICP and induce hyperkalemia

Options for an anticipated difficult intubation
-awake intubation
-fiberoptic bronchoscope
-tracheostomy

Contraindication
-blind nasaltracheal intubation in a basilar skull fracture
-signs of basilar skull fracture: CSF rhinorrhea or otorrhea, hemotympanic, ecchymosis
“raccoon sign”, “battle sign”

INTRAOPERATIVE MANAGEMENT

Common maintenance technique:
Barbiturate + opiod + N20 + muscle relaxant

N20 should generally be avoided when:
-air is entrained within the cranial vault
-peroids of hypotension

Intraoperative hypotension
-may occur after induction due to: vasodilation effects of induction agents combined with presumed hypovolemia
-treated with α adrenergic (phenylephrine)
-volume infusion
-fluid resusitation may be better corrected with colloid solutions or blood opposed to crystalloid solution infusion
-advantage of colloid or blood infusion opposed to crystalloid is less incidence of cerebral edema
-severe hypotension: may be treated with dopamine infusion
-maintain hematocrit above 30%

Useful monitors in hypotensive setting:
-arterial line
-central venous pressure
-pulmonary artery occlusion pressure
-TEE
-ICP

Intraoperative hypertension

Commonly treated with:
-additional doses of thiopental
-hyperventilation
-inhalational anesthetic agent
-hypertension + tachycardia is often controlled with β adrenergic blockade
-cerebral perfusion pressure (CePP) should be maintained between 70 – 110 mmHg
-vasodilators generally best avoided until the dura is open
-atropine may be used for excessive vagal tone (ex. bradycardia)

Excessive hyperventilation is avoided in head trauma patients:
-to avoid excessive reduction in CBF
-PaC02 between 25 – 30 mmHg is considered optimal in reducing ICP and maintaining adequate CBF

Common cardiac manifestations following head trauma injury include:
-dysrhythmias
-ecg changes including:
-T wave changes
-U wave changes
-ST segment changes
-QT interval changes

Disseminated intravascular coagulation (DIC) in severe head injury associated with:
-large release of brain thromboplastin
-diagnosed by coagulation profile/studies

Treatment of DIC includes:
-platelets
-fresh frozen plasma (FFP)
-cryoprecipitate

DIC in severe head injury often associated along with ARDS:
-may require mechanical ventilation

If PEEP is required, should be applied when:
-ICP monitoring is being evaluated
-dura is open

Diabetes insipidus often seen in severe head injury involving:
-the pituitary stalk
-large amount of dilute urine
-should be diagnosed with measurements of urine and serum osmolality
-should assess the response to vasopressin

ANESTHESIA FOR INTRACRANIAL MASS LESION

PREOPERATIVE MANAGEMENT
investigate into intracranial hypertension

CT/MRI :
-brain edema
-midline shift > 0.5 cm
-ventricular size

Physical Examination

Neurological assessment:
+/- change in mental status
+/- sensory deficits
+/- motor deficits

Medications
Patient taking?
-corticosteroids
-diuretics
-anticonvulsants

Laboratory Evaluation:

Rule out:
-hyperglycemia (corticosteroid induced)
-electrolyte abnormalities (diuretic and ADH effects on electrolyes)
-anticonvulsant levels (ensure therapeutic levels of anticonvulsant medications)

Premedication
-corticosteroids: continued upto day of surgery
-anticonvulsants: continued upto day of surgery
-pts with nl ICP: may benefit with benzodiazepines (ex, diazepam PO, midazolam IM/IV)
-pts with ↑ ICP: should avoid premedication due to possible respiratory depressants effects: ↑PaC02, ↑CBF: further↑ICP

INTRAOPERATIVE MANAGEMENT

Monitoring
-standard monitors
-arterial line
-urinary bladder catherization
-central venous catherization
-evoked potentials
-ICP monitoring

Arterial line
-allows for continuous blood pressure monitoring
-helps to regulate and optimize adequate cerebral perfusion pressure and resultant CBF
-allows for frequent arterial blood gas samples which helps to monitor ventilatory status: PaC02
-zeroing the arterial line at the level of the head (external meatus of the ear) helps to monitor cerebral perfusion pressure

Continous blood pressure monitoring very important during:
-induction
-hyperventilation
-intubation
-postioning
-surgical manipulation
-emergence

Central venous catheter
-generally required for patients receiving vasoactive medications
-helps to assess volume status

Site of CVC placement is controversial:
-internal jugular vein: may impede venous drainage from the brain and may be involved with carotid artery puncture
-median basilic vein: in order to avoid the complications involved with internal jugular vein CVC placement
-external jugular vein good alternative for CVC placement
-subclavian vein good alternative for CVC placement

Urinary catheter placement
-often placed due to commonly used diuretics
-long nature of neurosurgical procedures
-helps to assess fluid therapy management

Evoked potentials
-helps to assess integrity of neuropathways during neurosurgical procedures
ex. VEP: helps protect optic nerve damage
used during resection of large pituitary tumors

Intracranial pressure monitoring
-ventriculostomy: allows for the removal of CSF in order to decrease the ICP
-subdural bolt
-electronic ICP monitoring

Induction

Critical periods of patients with increased cranial pressure:
-induction of anesthesia
-endotracheal intubation

Improved intracranial compliance, reduced ICP with:
-osmotic diuresis
-steroids
-CSF removal via ventriculostomy s/p intubation

Goal:
-smooth induction
-gentle intubation
-avoidance of arterial hypertension: ↑BP leads to ↑ICP , results in ↓CePP and possible brain herniation
↓BP may lead to ↓ CePP creating vulnerability to cerebral ischemia

Common induction includes
-thiopental or propofol with hyperventilation
-muscle relaxation
-opiods
-esmolol

Benefit of propofol: short recovery time
benefit of etomidate: hemodynamic stability with less cardiodepressant effects
ex. unstable patient etomidate 6 – 8 mg with fentanyl 5 ug/kg in unstable cardiac patients

Monitoring
-standard ASA monitors
-A-line
-central venous catherization
-urinary catherization
-evoked potentials
-ICP monitoring

Arterial line
-continuous blood pressure monitoring to ensure adequate and optimal cerebral perfusion pressure and resultant CBF
-frequent ABG samples to closely monitor and regulate PaC02
-zeroing arterial line at the level of the ear (external auditory meatus) allows for closer approximation of the CePP

Central venous catherization
-indicated in patients requiring vasoactive medications
-site of central venous catherization is controversial:

Internal jugular vein

Medial basilic vein:
external jugular vein
subclavian vein

Internal jugular vein
-may impede venous drainage from the brain
-possible carotid puncture with complications of expanding hematoma
-expanding hematoma may impede venous drainage with resultant increased ICP

Urinary bladder catherization
-commonly used in diuresis
-long duration of surgical procedure
-assessing fluid therapy

Evoked potentials
-helps assess and monitor integrity of nerve pathways
ex. VEP helps prevent optic nerve damage
used during resection of large pituitary tumor

ICP monitoring
-ventriculostomy:
-subdural bolt
-electronic ICP monitoring
induction

Goal:
-smooth induction
-gentle intubation
-avoidance of arterial hypertension: ↑BP : ↑ICP: possible consequence of brain herniation
↓BP : ↓CePP: vulnerable to cerebral ischemia with resultant edema and inc ICP

Critical periods for patients with increased ICP
-induction of anesthesia
-endotracheal intubation

Methods to improve intracranial compliance in patients with increased ICP:
-osmotic diuresis
-corticosteroids
-CSF removal via ventriculostomy before intubation

Induction for mass lesion may include:
-thiopental or propofol with hyperventilation deep anesthesia with hyperventilation to reduce ICP fluctations
-muscle relaxation prevent straining or bucking which may increase ICP
-opiods ex. fentanyl 5 – 10 ug/kg blunt the sympathetic response to both laryngoscopy and intubation
-esmolol ex. 0.5 – 1 mg/kg prevent tachycardia in hypertensive patients

Benefit of propfol: short recovery time
benefit of etomidate : hemodynamic stability: prevent cardiodepression
ex. etomidate 6 – 8 mg with fentanyl 5 ug/kg for an unstable cardiac patient
induction option for a patient with reactive airway disease:
thiopental with isoflurane along with hyperventilation

Muscle relaxants with hemodynamic stability include:
-rocuronium
-vecuronium
-pipecuronium
-doxacurium
succinlycholine may be associated with an increase in ICP

Treatment of hypertension upon induction may include: Vasodilators are generally avoided until the dura is open:
-esmolol bolus -NTP
-deepening anesthesia with thiopental or propofol -NTG
-hyperventilation with lose dose isoflurane (less than 1 MAC) -Hydralazaine
-CCB

Treatment of intraoperative hypotension may include:

Vasopressors in incremental doses:
-ephedrine
-phenylephrine

Positioning of patient during a neurosugical procedure: mass lesion
Supine position: head elevation within 15 – 30 degree excessive head flexion/extension
-frontal craniotomy -facilitate venous drainage -may restrict jugular venous drainage
-temporal craniotomy -facilitate CSF drainage -restricted drainage may lead to ↑ICP
-parieto-occipital craniotomy

Maintenance

Techniques
-nitrous –opiod –muscle relaxant
-opoid – lose dose inhalational agent
-total intravenous anesthesia (TIVA)

Periods of greatest stimulation include:
-laryngoscopy / intubation
-skin incision
-dural opening
-periosteal manipulation
-closure

optimizing ICP reduction and maintaing adequate CePP
intraoperative hyperventilation: PaC02 25 –30 mmHg

Intravenous fluid management
-glucose free isotonic cystalloid or colloids are preferred (ex. LR, NS)
-glucose containing iv fluids avoided due to vulnerability of hyperglycemia (corticosteroid induced hyperglycemia)
-hyperglycemia may increase ischemic brain injury
-fluid requirements in neurosurgical procedures generally are lower than calculated fluid requirements
-reduced iv fluid administration in order to prevent further cerebral edema and increase in ICP

POSTOPERATIVE MANGEMENT

Emergence
-patients with removal of mass lesion are generally extubated at the end of the case
-emergence should be well controlled and smooth

Straining and bucking on the ETT may may cause:
-intracranial hemorrhage
-increase in ICP
-cerebral edema

Patients who remain intubated should be:
-sedated
-paralyzed
-hyperventilated

Model of a well controlled and smooth emergence:
-while the skin is being closed, try having the patient begin breathing spontaneously
-once the dressing is intact and the table is back in optimal orientation for emergence discontinue all inhalational anesthetics
-deliver 100% oxygen
-reverse neuromuscular blockade
-may administer iv lidocaine 1.5 mg/ kg
rapid awakening allows for neurological assessment
postoperatively the patient should be closely monitored in the ICU for neurological function and hemodynamic stability

ANESTHESIA MANAGEMENT FOR INTRACRANIAL ANEURYSM
PREOPERATIVE MANAGEMENT

-blood should be available prior to the start of the procedure
-determine whether rupture of the cerebral aneurysm has occurred
-investigate into presenting signs if increased ICP
-review CT imaging for hydrocephalus, ventricular enlargement and or midline shift

Relative contraindications for elective hypotension include history of:
-hypertension
-renal insufficieny
-cardiac disease
-cerebral vascular disease

Premedication:
-patients with normal ICP generally may receive sedation pre-induction
-patients with increased ICP generally should avoid sedation pre-induction to avoid the risk of hypercarbia

INTRAOPERATIVE MANAGEMENT
blood should be available prior to the start of the procedure

Overall goal of intraoperative management includes:
-prevent rupture of the cerebral aneurysm
-prevent rebleeding of the cerebral aneurysm
-prevent factors which may create cerebral ischemia
-prevent factors which may initiate cerebral vasospasm

Intraoperative monitoring
-ASA monitors
-intra-arterial line
-central venous catheter
-pulomary artery pressure

Intraoperative hypertension:
sudden increases in arterial blood pressure should be avoided
-may be avoided with deeper levels of anesthesia
-deep level of anesthesia may be occomplished by:
-adequate fluid resusitation guided by CVP trend with increased surgical level of anesthesia

May occur during:
-tracheal intubation
-surgical stimulation

Intraoperative hypotension
-reduces transmural tension across the aneurysm
-decreases risk of rupture of cerebral aneurysm
-decreases risk of rebleeding from ruptured cerebral aneurysm
-facilitates surgical clipping
-improves surgical visualization in amidst of bleeding
-may decrease surgical blood loss
-more pron in patients with preoperative use of CCB (nimodipine, nicardipine )
-due to decrease systemic vascular resistance (SVR) of CCB use

Cerebral protection during intraoperative hypotension
-use of temporary vascular clips
-thiopental administration
-mild hypothermia

Intraoperative hyperventilation
-generally avoided to prevent excessive decreases in CBF
clinical example: hyperventilation should be avoided in a patient with cerebral aneurysm with cerebral vasospasm

Intraoperative diuresis
-once the dura is opened
-facilitates surgical exposure
-reduces tissue trauma from surgical retraction
ex. mannitol diuresis

Intraoperative diuresis prior to dura opening :
-rapidly decreases ICP which may promote rebleeding
-tamponading effect of the dura upon the aneurysm is removed
-resultant increased risk of rebleeding
-therefore best to avoid osmotic diuresis prior to dura opening

ANESTHESIA MANAGEMENT FOR ARTERIOVENOUS MALFORMATION

Anesthetic management of arteriovenous malformation:
-blood should be available in the OR prior to the start of the procedure
-preparation for expectant extensive blood loss
-large bore IV access
-direct intra-arterial pressure monitoring
-embolization prior to surgery helps to reduce operative blood loss
-surgical access facilitated by hyperventilation and mannitol diuresis
-altered cerebral autoregulation may occur due to surgical resection of AVM lesion
-altered cerebral autoregulation may lead to hyperemia and cerebral edema due to increased BP
-control of blood pressure often accomplished with β blockers

ANESTHESIA FOR STEREOTACTIC SURGERY

Stereotactic procedures indicated for treatment of:
-disorders of involuntary movement
-diagnosis / treatment of deeply positioned brain tumors
-intractable pain
-epilepsy

Stereotactic procedures may be performed under:
-local anesthesia: allows for periodic evaluation of patients status
-sedation/amnesia: accomplished with a propofol infusion. Patient should have a normal ICP for sedation
-general anesthesia in case of emergency craniotomy.

Issues involved in converting from local anesthesia to general anesthesia may include:
-platform and localizing frame attached to patient’s head for stabilazation
-limited range of motion of neck while mask ventilation prior to intubation (due to localizing frame)

Possible options for emergent airway management while converting to general anesthesia (ex. emergent craniotomy)
-ETT intubation first definitive preference
-LMA alterative to a failed ETT intubation
-mask ventilation last resort amidst emergent conditions
awake intubation with fiberoptic bronchoscope:
-ideal and safe modality of airway management under limited exposure and movement of the patient’s airway
ex. stereotactic head frame limiting:
-range of motion of neck
-exposure/visibility for direct laryngoscopy

ANESTHESIA FOR SURGERY OF THE SPINE

Spine surgery commonly performed for:
-symptomatic nerve root compression
-cord compression due to degenerative changes
-correct deformities ex. scoliosis
-decompress the spinal cord
-spinal fusion s/p spinal trauma
-spinal tumor resection
-vascular malformation
-abscess

Compression of nerve root may occur:
-protrusion of an intervertebral disk into the spinal canal
-protrusion of an osteophytic bone segment into the spinal canal

Herniation of intervertebral disc
-usually occurs at L4-L5 or C5-C6
-usually occurs in patients between ages 30 –50 yrs

PREOPERATIVE MANAGEMENT

Evaluate for:
-limited range of motion of the neck
-neck braces which may complicate airway management
-pre-existing respiratory impairment
-pre-existing neurological impairment (document)

INTRAOPERATIVE MANAGEMENT

Factors which may complicate intraoperative anesthetic management:
-prone position
-multiple levels often involved
-instrumentation (Harrington rod, pedicle screw fixation)
-potential for large amounts of intraoperative blood loss

Positioning during spine surgery
prone position:
-induction of anesthesia and intubation in supine position
-patients turned into prone position with smooth gentle positioning requiring at least 4 people
-neck must remain in neutral position
-head may be displaced to the side in the prone position or faced down with use of a cushioned holder
-parallel foam rolls for the chest to rest on facilitates ventilation
-arms should be to the side with elbows flexed to prevent excessive abduction of shoulders

Physiologic/ hemodynamic changes which may occur while positioning in prone position:
-blunted or inhibited postural sympathetic reflexes
-resultant hypotension
-impedance to venous return due to abdominal compression
-possible increased intraoperative blood loss due to epidural vein engorgement

Extra caution in prone position to avoid:
-corneal abrasions
-retinal ischemia due to pressure on the ocular globe
-pressure necrosis

Vulnerable areas to pressure necrosis while in prone position include:
-nose
-ears
-forehead
-breast
-genitalia

Supine position:
-allows for anterior approach to the cervical spine

Supine position may increase risk of intraoperative damage of:
-traceha
-esophagus
-recurrent laryngeal nerve
-sympathetic chain
-carotid artery
-jugular vein