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Indian Journal of Anaesthesia 2007; 51 (6) : 486-495 Special Article
Indian Journal of Anaesthesia, December 2007
Scoliosis and Anaesthetic Considerations
Anand H. Kulkarni1 , Ambareesha M2
Scoliosis may be of varied etiology and tends to cause a restrictive ventilatory defect, along with ventilation-perfusion
mismatch and hypoxemia. There is also cardiovascular involvement in the form of raised right heart pressures, mitral valve
prolapse or congenital heart disease. Thus a careful pre-anaesthetic evaluation and optimization should be done. Intraoperatively
temperature and fluid balance, positioning, spinal cord integrity testing and blood conservation techniques are to be kept in mind.
Postoperatively, intensive respiratory therapy and pain management are prime concerns.
Keywords Scoliosis; Deformity, Spine; Monitoring, Spinal cord; Defect, Restrictive.
Introduction Table 1 Etiologic classification of scoliosis
Scoliosis is a complex deformity of the spine and 1. Idiopathic (genetic) scoliosis (approximately 70% of all cases
of scoliosis; classified by age of onset)
anaesthesia for scoliosis surgery can be challenging, with
several aspects to be kept in mind simultaneously. A brief 2. Congenital scoliosis (probably not genetic)
review is presented to highlight important aspects of the Vertebral
pre-anaesthesia evaluation and anaesthesia management. Open- with posterior spinal defect
With neurologic deficit (e.g., myelomeningocele)
Definition Closed- no posterior element defect
Scoliosis is a complex deformity of the spine re- With neurological deficit (e.g., diastematomy
sulting in lateral curvature and rotation of the vertebrae elia with spina bifida)
as well as a deformity of the rib cage1. There is usually Without neurological deficit (e.g., hemivertebra,
secondary involvement of the respiratory, cardiovascu- unilateral unsegmented bar)
lar and neurologic systems. Extravertebral (e.g., congenital rib fusions)
3. Neuromuscular scoliosis
Classification Neuropathic forms
The initial classification was given by Schulthess Lower motor neuron disease (e.g., poliomyelitis)
W 2. He classified scoliosis by the region involved.
Upper motor neuron disease (e.g., cerebral palsy)
1. Cervico thoracic Others (e.g., syringomyelia)
2. Thoracic Myopathic forms
3. Thoracolumbar Progressive (e.g., muscular dystrophy)
Static (e.g., amyotonia congenita)
Others (e.g., Friedrich’s ataxia, unilateral amalia)
5. Combined double primary
4. Neurofibromatosis (Von Recklinghausen’s disease)
The etiologic classification was introduced by the 5. Mesenchymal disorders
Terminology Committee of the Scoliosis Research Soci- Congenital (e.g., Marfan’s syndrome,
ety in 19693, that is shown in Table 1. Morquio’s disease, amyoplasia
congenita, various types of dwarfism)
Epidemiology Acquired (e.g., rheumatoid arthritis, Still’s disease)
Scoliosis can develop at any age, but tends to be- Others (e.g., Scheurmann’s disease, osteogenesis imperfecta)
come clinically evident during periods of rapid somatic 6. Trauma
growth. It’s reported prevalence in the general population Vertebral (e.g., fracture, irradiation, surgery)
varies from 0.3 – 15.3% 4-6. However the prevalence is Extravertebral (e.g., burns, thoracic surgery)
less than 3% for curves more than 10o and less than 0.3%
1. MD, DNB, Assistant Professor, 2. MD, DA, Professor and Head, Dept of Anesthesia, Kasturba Medical College, Mangalore,
Correspondence to: Anand H.Kulkarni, C 3-20, KMC Staff Quarters, Lighthouse Hill Road, Mangalore -575003. Karnataka, India.
E-mail: firstname.lastname@example.org Accepted for publication on:20.10.07
Anand H. Kulkarni et al. Scoliosis and anaesthesia
for curves more than 30 o. It is more common in adoles-
cents and has a female to male ratio of about 3:1 7.
75 -90% of cases of scoliosis are of the idiopathic
type, out of which the adolescent type is most common.
Remaining 10 – 25% cases belong to various other eti-
Measurement of severity
The Cobb’s method of measurement, recom-
mended by the Terminology Committee of the Scoliosis
Research Society, consists of three steps.
1. Locating the superior end vertebra.
2. Locating the inferior end vertebra.
3. Drawing intersecting perpendicular lines from the
superior surface of the superior end vertebra and from
the inferior surface of the inferior end vertebra. Fig.1 Cobb’s method: measurement of severity.
The angle of deviation of these perpendicular lines
from straight line is the angle of the curve (Fig1). If the Pre anaesthetic assessment
end plates are obscured pedicles can be used instead for I. Airway assessment: Airway difficulties may be
quantification 8. The draw back of the Cobb’s method is anticipated when the scoliosis involves the upper
that it measures a complex deformity in only two dimen- thoracic or cervical spine. Also devices like halo
sions. Nevertheless it maintains a uniform method of traction may interfere with securing the airway.
measurement. Some disorders like Duchenne muscular dystrophy
Surgery is performed when the Cobb’s angle ex- may lead to tongue hypertrophy.
ceeds 50o in the thoracic spine and 40o in the lumbar II. Respiratory system: Assessment of the pulmo-
spine. The goal of surgery is to stop the progression of nary system must focus on evidence of pre existing
cardiopulmonary disease. If untreated, idiopathic scolio- lung injury or pulmonary disease, pneumonia and
sis is often fatal in the fourth or fifth decades of life as a 10
severity of scoliosis . Factors associated with post-
result of pulmonary hypertension or respiratory failure9 . operative mechanical ventilation requirements in-
The severity of scoliosis and clinical implications are as clude pre-existing neuromuscular disease, severe
in Table 2. restrictive pulmonary dysfunction with a vital
Table 2 Severity of scoliosis and clinical correlation7 : capacity(VC) of <35% predicted, congenital heart
Cobb’s angle Clinical manifestations defects, right ventricular failure,obesity, anterior tho-
( degrees) racic spine surgery and blood loss of >30ml.kg .
<10 No symptoms Scoliosis results in reduced VC, reduced functional
>25 Increase in pulmonary artery pressure residual capacity (FRC), and restrictive pulmonary
>40 Consider surgical intervention disease pattern characterized by increased respira-
>70 Significant decrease in lung volume tory rate and decreased tidal volume. The severity
>100 Dyspnea on exertion of pulmonary impairment is influenced by the scolio-
>120 Alveolar hypoventilation, chronic respiratory sis angle (>70 ), number of vertebra involved (7 or
more), cephalad location of the curvature and de-
Treatment options: gree of loss seen in the thoracic kyphosis. Pulmo-
I. Non surgical – braces, traction, plaster applications nary impairment is manifested by a decreased arte-
rial oxygen tension due to pulmonary shunting There
II. Surgical- posterior approaches, anterior ap-
is significant controversy regarding the degree of
proaches, combined/staged procedures
Indian Journal of Anaesthesia, December 2007
improvement in pulmonary function after scoliosis way obstruction, which may be a result of chronic
surgery. One study found that patients with an an- airway inflammation secondary to poor clearance
terior component to correction had worse pulmo- of secretions . Significant displacement or rotation
nary function testing variables at 3 months but im- of the trachea or main stem bronchi may cause
proved function at 2 years. Patients who had poste- mechanical airway obstruction . In severe restric-
rior correction only had a trend for improved func- tive defects, there is decrease in inspiratory capac-
tion at 3 months but no significant difference from ity and also ineffective ventilatory patterns which
the anterior or combined group at 2 years . Scolio- rely on increase in frequency of respiration rather
sis surgery is more likely to have immediate pulmo- than increase in tidal volume, which increases the
nary complications if the curvature is >60 . Reduced work of breathing and promotes respiratory muscle
VC is the first manifestation of restrictive lung dis- fatigue in response to exercise. They also have a
ease. As the disease progresses gas exchange is decreased response to carbon dioxide . When the
affected by ventilation-perfusion mismatch, alveo- Cobb’s angle is 100 patients are at an increased
lar hypoventilation, an increased dead space and an risk of developing chronic respiratory failure and
increased alveolar- arterial gradient. Prolonged pe- pulmonary hypertension. The pulmonary hyperten-
riods of hypoxemia result in pulmonary hyperten- sion is a product of chronic atelectasis, chronic hy-
sion, hypercapnia and eventual respiratory failure. poxemia and chronic hypercapnia . Scoliosis of neu-
Surgery for scoliosis is performed to slow disease romuscular dysfunction etiology usually starts from
progression and prevent complications . Scoliosis early infancy, when the chest wall is very compli-
may limit the function of the respiratory muscles ant, and the distortion of the thorax is severe. Also
i.e., intercostals may be overstretched or unable to the lung growth is severely impaired. Moreover the
stretch due to intercostal space changes, putting potential for complications is higher because of prob-
them at a mechanical disadvantage. Moreover, the lems like chronic recurrent aspiration and
effectiveness of the muscles may be hampered by pneumonias due to impaired secretion clearance .
limiting the ability of the thorax to expand. The dis- Preoperatively respiratory function should be as-
tortion of the thoracic cage makes the respiratory sessed by a thorough history, focusing on functional
system much less compliant, thus increasing the impairment and effort tolerance, physical examina-
work of breathing even when the lungs themselves tion and appropriate investigations. Respiratory func-
are healthy . Scoliosis has generally been associ- tion should be optimized by treating any reversible
ated with the development of restrictive lung defect cause of pulmonary dysfunction like infection by
manifested by a decrease in total lung capacity physiotherapy and bronchodilator therapy as indi-
(TLC) on pulmonary function testing. Infantile and cated. Preoperative incentive spirometry is advis-
juvenile scoliosis are more likely to be associated able before thoracotomy for anterior approach cor-
with true lung hypoplasia because the thoracic de- rections.
formity is present during the period of rapid lung III. Cardiovascular system: The cardiovascular
growth and development . In adolescent scoliosis, changes associated with scoliosis are less common
in contrast, the decrease in TLC is more likely to but more serious than the changes in the respira-
reflect the impaired chest wall mechanics that pre- tory system and share a common etiology. The al-
vent normal inflation of the lungs . Long standing teration in the cardiovascular system is related pri-
hypoinflation and atelectasis leads to further reduc- marily to the changes in the structure of the medi-
tion of lung volume. The decreased TLC is often astinum and secondarily to the effects of chronic
associated with increased residual volume (RV), respiratory insufficiency on the function of the car-
resulting in very high RV /TLC ratio reflecting the diac system. The primary changes are related to
dysfunction of expiratory muscles, which do not al- structure of the mediastinum following scoliotic
low full exhalation . In severe cases of scoliosis, curves. The effect is a restrictive pericarditis with
flow-volume loops may show evidence of lower air- a possible secondary pericardial effusion. Limited
Anand H. Kulkarni et al. Scoliosis and anaesthesia
cardiac filling decreases any potential increases in Table 3 Suggested preoperative investigations be-
cardiac output . In response to exercise, the al- fore major spine surgery9
ready elevated pulmonary artery pressure increases. M i n i mu m Optional
Moreover the displacement or compression of the investigations investigations
Respiratory Plain chest X-ray PFT (bronchodilator
heart due to thoracic deformity may not allow an system reversibility)
increase in stroke volume necessary during exer- ABG Pulmonary diffusion
cise . Eventually even normal filling can be impaired Spirometry(FEV1,FVC)
and the cardiac output at rest can be impaired. At Cardiovascular ECG Dobutamine
this point cardiac reserves are limited and may not system
able to withstand the increased haemodynamic de- scintigraphy
mand of major surgery. Echocardiography and stress Blood Complete blood count Liver function tests
testing, either physical or pharmacologic, can be Cross match
done to determine the performance of the myocar- Urea/electrolytes
dium. In addition to mechanical impairment of myo- IV. Neurologic system: A detailed neurologic evalua-
cardium, there can be cardiovascular pathology sec- tion and documentation is important because of medi-
ondary to the chronic insufficiency of the respira- colegal issues. Moreover, patients who have preex-
tory system. Pulmonary hypertension is the natural isting neurologic deficits are at an increased risk of
evolution from chronic hypoxemia . Other factors developing spinal cord injury during scoliosis surgery.
contributing to pulmonary hypertension are that the Prepoerative considerations for patients undergo-
number of vascular units per unit volume of lung is ing major reconstructive spinal surgery are summa-
lesser than in normal lungs .Also in the compressed rized in Table 4.
lung regions, the alveoli become smaller than at re- Table 4 Preoperative considerations for patients
sidual volume, leading to blood flow in extra alveo- undergoing major reconstructive spinal surgery22
lar vessels which have a higher resistance . Even- Problem C o mme n t
tually right ventricular strain and failure will evolve Respiratory
from increased work of right sided cardiac output. Reduction in total lung Reduction worse with increas
capacity and vital -ing deformity. If vital capac
Detection of any right ventricular dysfunction should capacity -ity <40% predicted postop
be a stronger indication for complete cardiac evalu- -erative ventilation likely.
ation . Patients with idiopathic scoliosis also have A further decrease in the vital
capacity of up to 40% may
been found to have a high incidence of mitral valve occur postoperatively: recov-
prolapse (up to 25%). It may indicate a common ery may take up to 2
basis for both the entities, namely a collagen disor- Increasing V/Q mismatch Hypoxemia more likely
der . Moreover the incidence of scoliosis is higher Cardiovascular
Increase in pulmonary Independent of severity of
in patients with congenital heart disease than in nor- vascular resistance scoliosis
mal subjects. Hence the patients should be evalu- Increase in incidence of High index of suspicion
congenital heart disease
ated for the presence of congenital heart disease and mitral valve
like ventricular or atrial septal defects, patent duc- regurgitation
tus arteriosus, tetralogy of Fallot . Assessment of Variable preoperative Careful preoperative docu
the cardiovascular system should be done keeping deficit mentation
all above in mind. Minimum investigations include Musculoskeletal
Muscular dystrophy Abnormal response to muscle
an electrocardiogram and echocardiography to as- relaxants
sess left ventricular function and pulmonary artery Respiratory impairment Postoperative ventilation may
pressures. Dobutamine stress echo may be used to Nutrition
assess cardiac function in those with limited effort Malnourishment Likely in patients with meta
tolerance9 . The preoperative investigations suggested
are as in Table 3. Anaesthesia technique
I. Premedication: It is advisable to avoid use of nar-
Indian Journal of Anaesthesia, December 2007
cotics or heavy sedation as premedication in pres- capnography, esophageal stethoscope and a tem-
ence of pulmonary function impairment. perature probe. Also a urinary catheter should be
Bronchodilators may be used as part of optimiza- placed and urine output measured. The prolonged
tion of lung function preoperatively.Antisialogogues anaesthesia in unusual positions, combined with sig-
may be of value in procedures where a fibre- optic nificant blood loss, haemodynamic effects of tho-
intubation is planned or when prone or lateral posi- racic surgery and possible need for deliberate hy-
tion is required to minimize secretions and avoid potension mandate an invasive arterial line. Also
wetting of the tape securing the endotracheal tube. serial blood gas measurements may be done where
In those at risk of aspiration H2 blocking agents or required. CVP values are not reliable in the prone
proton pump inhibitors may be administered with or 23
position or with an open chest .
without sodium citrate.
VI. Positioning: Patient positioning for surgery varies
II. Induction: Routine induction by the intravenous depending on the level of spine to be operated upon
route is common. Alternatively an inhalational in- and nature of proposed surgery. Repositioning may
duction may be used guided by the patient’s condi-
be required intraoperatively. Peripheral nerves, eyes,
tion. Use of succinylcholine may be associated with
genitals and bony points should be padded and pro-
a hyperkalemic response in presence of myopathies
tected. Intraoperative imaging is often required, thus
or denervation. It may also cause malignant hyper-
the surgical site should be placed away from the
thermia in certain syndromes like King- Denborough,
table’s central support area. Prone positioning re-
central core disease, adenylate kinase deficiency
etc . Therefore it may be prudent to avoid succi- quires an uncompressed abdomen. Anterior ap-
nylcholine in these cases and use nondepolarising proaches to thoracic spine are via a thoracotomy
neuromuscular blocking agents for intubation. with the patient supported in the lateral position.
Anterior approach to the lumbar spine necessitates
III. Intubation: Anterior approaches to spine may ne- laparotomy.
cessitate the use of a double lumen tube for lung
isolation to enable access to the anterior spine. This VII.Malignant hyperthermia: Malignant hyperther-
may be difficult in cases where there is involve- mia is a rare pharmacogenetic myopathy affecting
ment of upper thoracic or cervical spine by the humans .Affected patients are susceptible to acute
scoliosis since distortion of the tracheobronchial tree hyperthermia which may be triggered by potent in-
is a common accompaniment. On the other hand a halational anaesthetics or succinyl choline . There
single lumen tube may be used, allowing more lim- are several published reports of myopathies associ-
ited intraopertive lung retraction, after discussion ated with malignant hyperthermia and several of
with the surgeon. In posterior approaches a single these syndromes have skeletal abnormalities includ-
lumen tube is used. ing scoliosis .It is critically important to be alert for
IV. Maintenance: A stable anaesthetic depth is re- early evidence of malignant hyperthermia like rise
quired to enable proper interpretation of somato in body temperature, elevated heart rate, ventricu-
sensory evoked potentials (SSEPs) or motor evoked lar arrhythmias or hypercapnia. The key to success-
potentials (MEPs). Either a nitrous oxide-narcotic- ful management of malignant hyperthermia is im-
inhalation agent technique may be employed or an mediate cessation of triggering agents, 100% oxy-
intravenous technique using propofol may be used. gen, cooling, supportive respiratory, cardiovascular
Non-depolarizing neuromuscular blocking agents are and acid-base procedures; and drugs like dantrolene
used to maintain relaxation. When MEPs are to be which lower free ionized intracellular calcium .
recorded it is advisable to use atracurium by con- VIII.Spinal cord monitoring: The cervical and lum-
tinuous infusion and maintain a constant depth of bar ganglionic areas of the spinal cord are meta-
block by neuromuscular monitoring. Intravenous flu- bolically more active and the number and size of
ids should be warmed and a warming mattress de- the cervical and lumbar feeders are greater than
vice is preferable. those in the thoracic cord and thus the thoracic cir-
V. Intraoperative monitoring: Minimum monitoring culation is described as“water shed”. This critical
should include ECG, NIBP, pulse oximetry, zone extends from T4 to T9 where the vascular
Anand H. Kulkarni et al. Scoliosis and anaesthesia
supply is least generous and special care should be aesthetic agents may suppress SSEP signals, cer-
taken during surgery .Distraction of the spine, tain patient conditions like neuromuscular degenera-
placement of pedicle screws and bony decompres- tion may make SSEPs impossible to obtain; and
sion are intraoperative events in which the spinal anterior cord injury may go completely undetected
cord or nerves may suffer injury . Above and be- in spite of SSEP monitoring. A wake-up test should
low the auto- regulation range, spinal cord blood flow be planned for well in advance and discussed with
depends on perfusion pressure. Spinal cord injury the patient in the pre-anaesthesia visit. Because of
due to above reasons leads to loss of auto regula- neuromonitoring concerns a predominantly nitrous
tion. In this situation hypotension may further com- oxide and narcotic technique is typically used. Small
promise spinal cord blood flow and compound the doses of volatile anaesthetics, if used, should be dis-
injury. Spinal cord blood flow is also highly sensitive continued an hour before wake-up is anticipated.
to PaCO2 alterations during induced hypotension28 . Two or three twitches on a train-of-four are suffi-
The risks of spinal cord damage and methods to cient to allow the patient to move his or her toes.
minimize the risks are as given in Table 5. The inci- After discontinuation of nitrous oxide and ventila-
dence of post operative neurologic injury is estimated tion with 100% oxygen, the patient should be able
at 1.84% .SSEPs, MEPs and the “wake-up” tests to follow commands to move their toes within ten
are commonly used to help safeguard spinal cord minutes. It is not advisable to reverse neuro muscu-
and nerve root function during surgery. lar blockade or narcotics to speed a wake-up test
Table 5 Risks of spinal cord damage 22 because this may result in violent movements that
can damage instrumentation or hurt the patient. Also
Risk related to:
the sympathetic discharge accompanying narcotic
Length and type of surgical procedure reversal may further compromise spinal cord blood
Spinal cord perfusion pressure flow. As soon as satisfactory movement is observed,
Underlying spinal pathology anaesthesia is reestablished. A successful wake-up
Pressure on neural tissue during surgery test suggests an intact cortex and spinal cord.
Risk minimized by: B . SSEP: They are a type of sensory evoked response.
Careful positioning It provides the ability to monitor functional integrity
Maintaining SCPP of sensory pathways in the anaesthetized patient
SCPP = MAP – CSFP undergoing surgical procedures which place the
CSFP can be reduced by CSF drainage spinal cord at risk. It is recorded after electrical
MAP manipulated by anaesthetist stimulation of a peripheral mixed nerve. Stimulation
?keep systolic blood pressure > 90 mmHg is by surface electrodes placed on the skin above
Drugs the nerve. A square wave stimulus of 50-250 micro
Methylprednisolone given less than 8 hours after insult sec duration, strength 20-50 mA, stimulation rate 1-
NMDA antagonists (ketamine, magnesium) 6 Hz is commonly used. Sites of stimulation are
Prevention of hematoma formation
common peroneal nerve at knee or posterior tibial
nerve at ankle. For best results an anaesthetic tech-
nique that does not markedly depress the SSEP
Stop anti-platelet medication preoperatively
should be chosen and the physiologic status of the
Withhold heparin immediately postoperatively
patient should remain constant during periods of
(CSFP, cerebrospinal fluid pressure; MAP, mean arterial pressure; 31
NMDA, N-methyl-D-aspartate; SCPP, spinal cord perfusion pres-
potential surgical injury .The blood supply to the
motor tracts is derived from the anterior spinal ar-
tery. It is therefore possible for significant motor
A. Wake-up test: It was first described by Vauzelle,
30 deficit to develop post-operatively in patients with
Stagnara et al in 1973 . It is a gross test of spinal 32
intact SSEPs throughout surgery . All anaesthetic
motor function. It remains the most reliable assess-
drugs affect SSEPs. Generally they tend to increase
ment of the intact spine for several reasons. An-
latency and decrease amplitude. Exceptions are ni-
Indian Journal of Anaesthesia, December 2007
trous oxide, ketamine and midazolam which do not A. Reducing blood loss
affect latency. Etomidate has been reported to in- 1. When patients are placed prone intraabdominal
crease amplitude. The use of inhaled agents upto 1 pressure should be minimized. This leads to a re-
MAC may not significantly affect SSEP monitor- duced epidural venous pressure and thus the venous
ing. Bolus doses of opioids or sedatives or sudden surgical bleed.
increase in concentration of anaesthetic agents al-
2. Hypotensive anaesthesia is considered a reason-
ter SSEPs. Therefore the best anaesthetic technique ably safe and effective method for reducing blood
is one that provides smooth and continuous anaes- loss by up to 58% during spine surgery .Mean
thetic effect avoiding bolus dosing . Physiologic arterial pressure is typically maintained at 60-65mm
factors influencing SSEPs include blood pressure, of Hg. Hypotensive anaesthesia can be achieved
temperature and blood gas tensions. When mean by the use of inhalational agents , sodium nitroprus-
arterial pressure falls to below the lower limit of 45
side , ganglion blocking drugs e.g.trimethaphan ,
auto- regulation there is progressive decrease of calcium channel blockers e.g. nicardipine , beta
amplitude with no change in latency . Hypother- blockers e.g. propranolol, esmolol, labetalol , nitro-
mia causes increase in latency and decrease in glycerin , fenoldopam etc.
amplitude .Hyperthermia decreases amplitude and 3. Antifibrinolytic agents e.g. aprotinin inhibits plas-
causes loss of wave at 42 C . Hypoxia decreases min and kallikrein and preserves platelet function .
amplitude . An amplitude decrease of 50% or a Urban et al found significantly reduced blood loss in
latency increase of 10% may suggest a correctable major spine surgeries where aprotinin infusion was
problem. It is to be confirmed that capnography; used intraoperatively .
pulse oximetry and temperature readings are all
constant for the patient. The blood pressure is to be B. Autologous blood transfusion
raised in attempt to improve spinal cord perfusion. Autologous blood can be made available to the
If hemodilution had been performed it should be patient by 3 methods.
reversed. A wake-up test or anatomic manipulation 1. Preoperative autologous blood donation
may then be performed based on the surgeon’s dis- (PABD): The patient donates blood 3 -5 weeks
cretion37 . before surgery for use intraoperatively. Recombi-
C. MEP: The limitations of the wake- up test led in- nant erythropoietin has been used before major sur-
vestigators to explore the possibility of monitoring gery to rise hemoglobin levels, to reduce allogenic
MEPs38 . Compared to SSEPs, MEPs are markedly blood requirements and facilitate PABD and acute
depressed by almost all anaesthetic agents 39.The normovolemic hemodilution (ANH).
marked influence of anaesthetic drugs on MEPs de- 2. Acute normovolemic hemodilution (ANH): This
mands a rigid anaesthetic protocol. During the MEP is performed immediately before surgery. The re-
recording anaesthesia is maintained by minimum moved blood is replaced by the infusion of colloids
dose of ketamine or etomidate infusion. An alterna- or crystalloids to achieve normovolemia with re-
tive is to use a titrable infusion of droperidol-fenta- duced hematocrit. During surgery blood of a lower
nyl40 . hematocrit is lost. The donated blood may be
IX. Blood conservation: In extensive spine surgeries retransfused once hemostasis is achieved.
blood losses are typically 10 to 30 ml.kg . It is 3. Intraoperative cell salvage: Blood lost during
desirable to keep allogenic blood transfusion to a surgery is collected using commercially available
minimum considering the risks of allogenic transfu- equipment and is then anticoagulated, filtered for
sion i.e., hypothermia, impaired coagulation, hyper- clots and debris, centrifuged, resuspended in saline
kalemia, hypocalcaemia, transfusion reactions, acute and reinfused to the patient. Clotting factors need
lung injury, transmitted infections etc. This is ac- to be replaced using fresh frozen plasma. The tech-
complished by techniques to reduce blood loss and nique is unsuitable in the presence of malignancy or
by autologous blood transfusion. infection.
Anand H. Kulkarni et al. Scoliosis and anaesthesia
X. Post operative care: The patients undergoing fects . The use of opioids would not interfere with
scoliosis surgery frequently have preexisting mor- neurologic assessment. However the effects of a
bidity, and surgery imposes several further stresses single intrathecal opioid dose would have a limited
like significant blood loss and fluid shifts, prolonged duration of effect. Other techniques like intrapleu-
anaesthesia, hypothermia etc. After scoliosis cor- ral infusions of local anaesthetics or opioids or both
rection preferably all patients should be cared for in have been used .The use of low dose intravenous
an intensive care setting. This is particularly impor- ketamine has demonstrated efficacy with an initial
tant in those with pre existing myelopathy, pulmo- dose of 0.25 mg.kg -1, followed by an infusion of 2-
nary dysfunction, cardio vascular disease, extensive 2.5 mcg.kg -1.min-1 improves pain scores, decreases
spine surgery, airway edema or those who have had nausea, reduces narcotic requirements and is not
massive transfusion . Oxygen by mask is given for associated with hallucinations27 .
the first few hours after extubation and may be re-
quired for longer periods in those with pre existing Conclusion
pulmonary dysfunction. Pulmonary complications Scoliosis, which may be of varied etiology, leads to
(ARDS, pneumonia, atelectasis, pulmonary embo- respiratory involvement characterized by restrictive lung
lism) are the most common post operative compli- disease, ventilation-perfusion maldistribution and hypox-
cations, and vigilant monitoring, incentive spirom- emia. Cardiovascular involvement is usually in the form
etry and aggressive pulmonary toilet are essential of raised right heart pressures, mitral valve prolapse or
for reducing morbidity particularly in those with pre congenital heart disease. Anaesthesia is often needed
existing pulmonary disease. Certain other compli- for corrective orthopaedic surgery, which is very chal-
cations which could occur after scoliosis surgery lenging. A detailed pre-anaesthetic assessment and opti-
are neurologic injury, ileus, pneumothorax, dural mization of the respiratory and cardiovascular systems
tears, urinary complications and syndrome of inap- is imperative. Important intraoperative considerations are
propriate ADH secretion . monitoring, temperature and fluid balance maintenance,
XI. Post operative analgesia: Pain management can positioning, spinal cord integrity monitoring and blood
be challenging and pain is of a severe degree in conservation. Post operative intensive care, respiratory
more extensive procedures. A multimodal approach care and pain therapy deserve special mention.
to analgesia is recommended using a combination References
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