Anaesthesia for spinal surgery in adults
D. A. Raw
1
*, J. K. Beattie
2
and J. M. Hunter
1
1
University Department Anaesthesia, University Clinical Department, The Duncan Building, Daulby Street,
Liverpool, L69 3GA, UK.
2
Royal Liverpool and Broadgreen University Hospitals NHS Trust, Prescot Road,
Liverpool L7 8XP, UK
*Corresponding author. E-mail:daveraw@doctors.org.uk
The spectrum of spinal surgery in adult life is considerable. Anaesthesia for major spinal
surgery, such as spinal stabilization following trauma or neoplastic disease, or for correction of
scoliosis, presents a number of challenges. The type of patients who would have been declined
surgery 20 yr ago for medical reasons, are now being offered extensive procedures. They com-
monly have preoperative co-morbid conditions such as serious cardiovascular and respiratory
impairment. Airway management may be dif®cult. Surgery imposes further stresses of signi®-
cant blood loss, prolonged anaesthesia, and problematical postoperative pain management. The
perioperative management of these patients is discussed. The advent of techniques to monitor
spinal cord function has reduced postoperative neurological morbidity in these patients. The
anaesthetist has an important role in facilitating these methods of monitoring.
Br J Anaesth 2003; 91: 886±904
Keywords: anaesthesia, general; monitoring; surgery, spinal
The scope of spinal surgery is considerable. Both adult
and paediatric patients present for surgery, which may
be elective or urgent. They mainly present with one of
®ve pathologies: trauma, for example an unstable
vertebral fracture; infection, for example vertebral
abscess; malignancy (metastatic or primary disease
with spinal instability, pain, and neurological comprom-
ise); congenital/idiopathic, for example scoliosis; or
degenerative disease. In excess of 25 000 spinal
operations were performed in the UK in 2001±2.
112
Surgery may be required at any site in the spine from
cervical to lumbosacral. Procedures range from minim-
ally invasive microdiscectomy, to prolonged operations
involving multiple spinal levels and signi®cant blood
loss. An osteotomy is a decompressive procedure, which
releases compressive forces at a localized site.
Stabilization of the spine involves instrumentation
above and below the unstable spinal level. Distractive
forces may also be applied to the spine, for example in
surgery for scoliosis, with instrumentation placed over
multiple spinal levels. Insertion of such devices may be
through a posterior, anterior, or a combined approach
involving repositioning of the patient part way through
the procedure and major blood loss.
The challenge to the anaesthetist is to provide optimal
surgical conditions whilst ensuring adequate oxygenation to
the brain and spinal cord, and facilitating the use of
intraoperative spinal cord monitoring techniques if appro-
priate.
Pathological conditions requiring spinal
surgery in adult practice
Scoliosis
Scoliosis involves a lateral and rotational deformity of the
spine, which occurs in up to 4% of the population.
98
Most
cases are idiopathic (70%) and occur with a male:female
ratio of 1:4 (Table 1). Surgery is usually considered when
the Cobb angle exceeds 50° in the thoracic, or 40° in the
lumbar spine (Fig. 1A and B). Surgery aims to halt
progression of the condition and to at least partially correct
the deformity, preventing further respiratory and cardiovas-
cular deterioration. Left untreated, idiopathic scoliosis
rapidly progresses and is often fatal by the fourth or ®fth
decade of life, as a result of pulmonary hypertension, right
ventricular failure, or respiratory failure.
85
Muscle disorders
Muscular dystrophy and cerebral palsy are important causes
of scoliosis. Of the muscular dystrophies, Duchenne
REVIEW ARTICLE
British Journal of Anaesthesia 91 (6): 886±904 (2003)
DOI: 10.1093/bja/aeg253
ÓThe Board of Management and Trustees of the British Journal of Anaesthesia 2003

muscular dystrophy (DMD) is the most common, with an
incidence of one in 3300 male births. It is inherited as a sex-
linked recessive condition affecting skeletal, cardiac, and
smooth muscle. Patients lack a membrane cytoskeletal
protein, `dystrophin', and typically present between the ages
of 2 and 6 yr with progressive weakness of proximal muscle
groups. Up to one-third of patients have intellectual
impairment.
73
DMD patients have a high incidence of
cardiac abnormalities (50±70%). In the later stages of the
disease, a dilated cardiomyopathy may occur associated
with mitral valve incompetence. Dysrhythmias occur and up
to 50% of patients have cardiac conduction defects. Cardiac
arrest in DMD patients has been reported during spinal
surgery, from which some patients have been resuscitated,
92
and others have died.
99
Surgery improves the patient's
quality of life, slows the decline in respiratory function, and
increases life expectancy.
26
Muscular dystrophic patients are sensitive to non-
depolarizing neuromuscular blocking agents, and hyperka-
laemia may occur with the use of succinylcholine.
Carcinomatosis
Patients with primary or secondary malignant disease of the
vertebral column and spinal cord are increasingly being
considered for surgery, the aims of which are primarily to
relieve pain but also to excise the lesion, prevent further
neurological deterioration, and stabilize the vertebral col-
umn. These patients have commonly lost a large amount of
weight and have reduced physiological reserve.
Respiratory complications of malignancy are common in
such patients,
105
and include infection, pleural effusion, and
pulmonary toxicity from alkylating agents (cyclophospha-
mide, chlorambucil, busulfan) or antimetabolites (metho-
trexate, azathioprine). Myocardial injury may also occur
secondary to the use of chemotherapy (busulfan, cyclopho-
sphamide, mitomycin). Metabolic derangements such as
hypercalcaemia, and inappropriate secretion of antidiuretic
hormone may develop. The latter is associated with small
cell lung tumours, carcinoma of the prostate, pancreas and
bladder, and central nervous system neoplasms.
It is usual for these patients to have acute-on-chronic pain
problems. They are often receiving regular opioids, non-
steroidal anti-in¯ammatory drugs, and simple analgesics.
Patients may therefore have an increased requirement for
intraoperative and postoperative analgesia as a result of
pharmacodynamic-related opioid tolerance, and pharmaco-
kinetic factors such as liver enzyme induction.
Spinal trauma
Patients with traumatic injury frequently present for surgical
spinal stabilization during the period of spinal shock, which
begins almost immediately after the insult and may last for
up to 3 weeks.
36
Some degree of spinal cord dysfunction
may also be present in patients with malignant disease
presenting for spinal stabilization. The clinical effects
depend on the level of injury to the spinal cord. A
physiological sympathectomy occurs below the level of
the spinal cord lesion, possibly causing hypotension
secondary to arteriolar and venular vasodilatation. Injuries
at or above T6 are particularly associated with hypotension,
as the sympathetic out¯ow to splanchnic vascular beds is
lost.
2
Bradycardia also occurs if the lesion is higher than the
cardiac sympathetic out¯ow (T2±T6), the parasympathetic
cranial out¯ow being preserved. A complete cervical cord
injury produces a total sympathectomy and therefore
hypotension will be more marked.
bove the level of the lesion, sympathetic out¯ow is
preserved. Vasoconstriction in upper body vascular beds
and tachycardia may be observed in response to the
hypotension resulting from reduced systemic vascular
resistance (SVR) in the lower part of the body.
Hypotension associated with spinal cord injury responds
poorly to i.v. ¯uid loading, which may cause pulmonary
oedema.
24
Vasopressors are the treatment of choice. Other
causes of hypotension should be excluded such as blood loss
associated with other injuries. Hypoxia or manipulation of
the larynx or trachea may cause profound bradycardia in
these patients. Positive pressure ventilation (IPPV) causes
marked arterial hypotension as the SVR cannot be raised to
offset the changes in intrathoracic pressure caused by IPPV.
Mid to low cervical spine injuries (C4±C8) spare the
diaphragm but the intercostal and abdominal muscles may
be paralysed (Fig. 1C±E). This leads to an inadequate cough,
paradoxical rib movement on spontaneous ventilation, a
decrease in vital capacity by up to 50% of predicted values
(as a result of a reduction in inspiratory capacity to 70% and
expiratory reserve volume to 20% of predicted), a decrease
in functional residual capacity to 85% of predicted, and a
loss of active expiration.
67
There is also an increased risk of
venous thromboembolism in patients with spinal trauma,
together with delayed gastric emptying, and impairment of
thermoregulation. Administration of succinylcholine may
cause hyperkalaemia from 48 h after the injury.
36
Autonomic dysre¯exia may be present from 3 to 6
weeks after the spinal cord injury. This condition is
Table 1 Aetiology of structural scoliosis (relative frequencies). Derived from
Kafer,
49
published with permission of Anesthesiology
Idiopathic (70%)
Congenital Abnormal spinal cord/vertebral development
Neuromuscular (15%) Neuropathic: cerebral palsy, syringomyelia,
poliomyelitis
Myopathic: muscular dystrophies, neuro®bromatosis,
Friedrich's ataxia
Mesenchymal
disorders
Rheumatoid arthritis, Marfan's syndrome,
osteogenesis imperfecta
Metabolic bone
disease
Osteoporosis, Paget's disease
Malignancy Primary and secondary tumours
Trauma/surgery Fracture, radiotherapy, surgery
Infection Tuberculosis, osteomyelitis
Anaesthesia for spinal surgery in adults
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