Anaesthesia in scoliosis
Dr. S. Parthasarathy
MD., DA., DNB, MD (Acu),
Dip. Diab.DCA, Dip. Software statistics
PhD (physio)
Mahatma gandhi medical college and research
institute, puducherry, India
What is it ??
• Scoliosis is a lateral curvature and rotation of
the thoraco-lumbar vertebrae(commonly) with
a resulting rib cage deformity.
When it is problematic – cobb angle
• > 10 * abnormal
• > 65* respiratory
• > 100 * Rt HF
• > 40 * - surgery
• 1 to 2 degrees/year
The initial classification was given by
Schulthess W
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Cervico thoracic
Thoracic
Thoracolumbar
Lumbar
Combined double primary
The list is very big
• Idiopathic
common – 70 % cases
• Neuropathic
Poliomyelitis
Syringomyelia
Friedreich’s ataxia
• Myopathic
Myopathies
• Osteopathic
vertebral anomalies – infection, TB,
tumors
Incidence
• 10 -- 30 degrees – 3 %
• more than 30 degrees -- 0.3 %
• Adolescents
• Female : male -- 3:1
Why to correct ??
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to correct the curve
fuse the spine,
improving posture
halting the progression of pulmonary dysfunction.
• The approach may be
• posterior, anterior or combined
• depending on the cause and severity of the
curvature
Correction – example
Preanaesthetic check up
What is special ??
Location ?? Etiology??
Airway assessment
• upper thoracic or
cervical spine
• Traction devices
• Duchenne –
tongue hypertrophy
• discuss preoperatively the stability of the spine
with the surgeon
• previous radiotherapy of the head and neck can
cause diffculty in direct laryngoscopy
Airway assessment
• Xrays and CT scan neck SOS
• A decision must be made, whether to intubate
the patient awake or asleep.
Respiratory system
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Restrictive lung defect
VC decrease TLC decrease
RV may increase
RV /TLC increase
? Allow full exhalation
• Secretions retained
infections
• Resp. Rate may increase
Scoliosis and loss of lung volume
The problems are
• abnormal thoracic cage geometry producing a
marked decrease in chest wall compliance
• There is a mechanical defect
• Exceptions include congenital and infantile
scoliosis where there is lung hypoplasia
Factors
• More than 70 degrees and
• More than 7 vertebrae
• Hypoxemia, progressing to PHT and Rt heart
failure – not necessarily hypercarbia
Responses
abnormal ventilatory patterns in response to
hypoxemia and hypercarbia
Factors associated with postoperative
mechanical ventilation requirements
• pre-existing neuromuscular disease,
• severe restrictive pulmonary dysfunction with
a vital capacity(VC) of <35% predicted
• congenital heart defects,
• Right ventricular failure,
• obesity,
• anterior thoracic spine surgery
• blood loss of >30ml/kg
Preop correction
• Infection
• Bronchodilators
• Incentive spirometry
Cardiovascular system
• Less common
• But more dangerous
Cardiovascular system
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↑ PVR
PHT and RVF.
mitral valve prolapse
restrictive pericarditis with a possible secondary
pericardial effusion.
• Limited cardiac filling decreases any potential
increases in cardiac output – surgery and anaes ??
• Duschenne – cardiomyopathy
• Marfan s – AR and MR
ECG
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Tachycardia,
prolonged PR and QRS intervals,
ST abnormalities,
bundle branch block,
Q waves in the left precordial leads and tall R
waves in the right precordial leads.
• Ejection fraction may be decreased on
echocardiogram.
Special in preop
• When does it start
• The number of alveoli increases from
approximately 20 million at birth to 250 million
at 4 years of age
• Where is it ??
• Cervical or thoracic
• Number of vertebrae ??
Preop summary
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Airway
CVS
RS
Neuro
• History examination and document
Investigations
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Routine
Xrays
ECG
Echo
PFT
Blood grouping and typing
rehearse the wake-up test during the
preoperative visit .
Premedication
• Antisialogogue – FOL , position
• Antibiotics and bronchodilators
• Preop prophylaxis with high dose corticosteroids
should be considered for patients with a preexisting
neurologic deficit.
• Sedatives and heavy narcotics ?
• DVT --- The use of compression stockings and/or
pneumatic boots is recommended
Anaesthetic techniques
General
anaesthesia
Induction
• Intravenous is ideal
• no to Scoline
• hyperkalemic response in presence of
myopathies or denervation.
• It may also cause malignant hyperthermia in
certain syndromes
Intubation
• FOL awake
• NDPs
• Double lumen tube in anterior approach to
thoracic spines
Positions
• Anterior approach to thoracic spine
• Posterior approach to lumbar spine
• Anterior approach to lumbar spine
• Position changes intraop
• Peripheral nerves, eyes, genitals and bony points
should be padded and protected
Monitoring
• ECG ,SPO2,Temperature,ETCO2, urine output ,
blood loss , NMJ monitoring
• CVP monitoring according to necessity
• Open chest and prone position – role of CVP ??
• TEE better than CVP in prone position ??
• Catheter and output – monitor both !!
Arterial line
• The prolonged anaesthesia in unusual positions,
combined with significant blood loss, haemodynamic
effects of thoracic surgery and need for deliberate
hypotension mandate an invasive arterial line.
• Also serial blood gas measurements may be done
where required
spinal cord monitoring – stagnara
• The ‘wake-up’ test provides a snapshot of
spinal cord motor function.
• Surgery is halted, the volatile agent switched
off and emergence allowed.
• The patient is asked to move their feet, ok then anesthesia can be recommenced
• Beware of tubes, catheters
• Any paraperesis – remove hardware, stabilize
hemodynamics
Defects in wake up test ??
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Sensory deficits - ??
Preoperative paraperesis ??
Intra operative recall -- !!
Temporary test – problem can come later ?
Squeeze hand and then proceed !!
If he does , immediate give propofol / agent/
narcotics
SSEP monitoring
• SSEP monitoring involves stimulating a peripheral
nerve often the posterior tibial nerve, and then
detecting a response with epidural or scalp
electrodes.
• The evoked potentials are averaged more than 2–
3 min to eliminate background noise then
displayed as voltage against time.
SSEP
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A square wave stimulus
50-250 micro sec duration,
strength 20-50 mA,
stimulation rate 16 Hz is commonly used.
• Hypothermia, hypotension may influence SSEP
SSEP
• Baseline data obtained after skin incision
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Responses are recorded
intermittently during
surgery
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A reduction in the amplitude by 50% and an increase
in the latency by 10% are considered significant.
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SSEP tests only dorsal column function not motor
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Rarely - post operative neurologic deficit reported
despite preservation of SSEP intraoperatively
SSEP
> 10 %
<
5
0
%
SSEP
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0.5–1.0 MAC isoflurane, desflurane or sevoflurane. -SSEP – OK – monitoring
Nitrous oxide potentiates the depressant effect of
volatile anesthetics
IV anesthetics generally affect SSEPs less than inhaled
Etomidate ,ketamine increases cortical SSEP amplitude
Opioids – not much change
Neuromuscular blocking agents may reduce
background noise
SSEP
• Bolus IV anaesthetics ??
• Wait for 5- minutes to stabilize after vaporizer
dial change
• Sevoflurane better if rapid changes are needed
• If in doubt , perform wake up test
Clonus test
• Clonus can normally be elicited in patients with
intact spinal reflexes and lack of central inhibition
• Coming out of GA
• It does not require patient cooperation
• clonus can be elicited – may be an injury to cord
• absence of clonus does not reliably predict injury
Motor evoked potentials (MEPs)
• MEP monitoring involves stimulating the motor cortex by
electrical impulses transcranially and detecting the
resulting signal at spinal level with epidural electrodes or
from muscles as a compound muscle action potential
(CMAP)
• MEPs are markedly depressed by almost all
anaesthetic agents
• Minimum dose ketamine and record
• May not absolutely reliable
Motor cortex Stimulation – biceps
brachii CMAP
Something becomes abnormal in cord
monitoring ??
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Maintain BP
100 % oxygen
Iv fluids
Blood to correct anemia
• Perform wake up test , adjust or remove
instrumentation
Temperature
• Body temperature can decrease considerably
during the operation.
• Temperature monitoring, i.v. fluid warmers
and warm air blankets should be commenced
at induction
surgery.
and
continued
throughout
Blood conservation:
• Major scoliosis surgery – 10 – 30 ml /kg go upto 50 ml
• Decrease surgical time
• Position proper, relax abdominal muscles
• Antifibrinolytic agents e.g. aprotinin inhibits plasmin
and kallikrein and preserves platelet function – use as
an infusion
• Autologous blood donation
• Hypotensive anaesthesia
Postop pain relief is painful
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Children
Large incisions
Cognitive impairment
Preop painful conditions
Post op pain relief
• Good postoperative analgesia is essential to allow
frequent physiotherapy and early mobilization, and
so reduce the risk of respiratory complications
• Systemic opioids , NSAIDs (after 24 hours) , PCA,
• paravertebral block, Epicath – can be kept by the
surgeon end operatively
Post op paralysis
• The incidence of motor deficit or paraplegia
after surgical correction of scoliosis in the
absence of spinal cord monitoring, has been
quoted as between 3.7 and 6.9%.
• This can be reduced by intra operative
monitoring to 0.5%
Some more perioperative complications
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Fat embolism
Air embolism
Coagulopathy
Visual loss
Necessity for postoperative ventilation
Hyponatremia
Summary
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Definition and incidence
Cobbs angle and severity
Etiology
Pre op : : airway, RS, CVS, Neuro , premed
Induction , airway, scoline ?? Monitors
Blood loss
Emergence and post op problems