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CHAPTER 18/PREPARATION FOR SURGERY / 203
either excitatory or depressive and are most commonly
seen when meperidine (pethidine) is coadministered (2).
Other opioids with a piperidine base (e.g., fentanyl) have
been used without complications. The assumption is that
alfentanil and sufentanil are probably safe (3,4). No literature addresses the safety of remifentanil.
The current recommendations are that the newer
reversible monoamine oxidase inhibitors (MAOIs)
should be discontinued 24 hours before anesthesia. The
older irreversible MAOIs should be continued because of
the high risk of uncontrolled depression in the weeks
leading up to surgery. Under these circumstances, all opioids may display an exaggerated depressant effect and
smaller doses should be used in the first instance.
Meperidine (pethidine) should be avoided.
Most institutions, and all anesthetists, should have a
management plan for the diabetic patient. Ideally the diabetic should appear as early as possible on the theater list
(operating schedule). Management should be directed to
avoid dangerous hypogl ycemia and excessi ve h yper glycemia. An intravenous dextrose infusion, combined with a
sliding scale of actrapid insulin, is often used to facilitate
perioperative glycemic control.
The use of specific analgesic or anxiolytic medication
in the immediate preoperative period is a matter of personal choice and can be tailored to the individual patient’s
requirements.
CONSENT FOR ANESTHESIA
In the current climate with the drive for increased day
of surgery admissions, a strong argument can be made for
the anesthetic assessment and consent to be performed
before admission to the hospital for surgery. This allows
time for appropriate investigations to be organized and
the results to be reviewed before admission to the hospital. This is particularly pertinent for those with cardiorespiratory disease, in whom modification of therapy may
be required for optimization of the medical condition
before anesthesia. It also enables the risks and complications to be explained to the patient in a nonthreatening
environment.
POSITIONING
Enough emphasis cannot be placed on the care that
must be taken in positioning the patient under anesthesia
to minimize the risk of pressure injury. Surgery on the
lumbar spine may be undertaken in the lateral or prone
position. For combined anterior and posterior stabilization, the patient needs to be rotated part way through the
procedure.
The patient in the prone position is at particular risk.
Appropriate padding and supports should be used to prevent pressure injury to soft-tissue structures (e.g., breast
and penis) and bony prominences (e.g., iliac crest, knees,
and elbows). Special attention should be given to protecting the orbital structures from trauma. The eyes
should be taped closed to prevent corneal abrasions and
the head should be supported to prevent pressure on the
supraorbital nerves. There is little evidence to suggest
that use of ophthalmic lubrication confers any benefit.
Pressure on the globe must be avoided at all costs
because of the danger of retinal vein occlusion or retinal
ischemia. The latter is of particular concern if hypotensive anesthesia is employed. Both of these complications
may lead to blindness.
Before positioning in the prone position, it is worth
identifying limitations in cervical spine movement and
assessing the range of shoulder movement. The arms may
be positioned with the arms flexed at the elbow, externally rotated and abducted at the shoulder and placed on
a support. This has the advantage of allowing easy access
to peripheral veins, arterial monitoring, pulse oximetry,
and neuromuscular monitoring. However, the ulnar nerve
and brachial plexus must be protected to avoid pressure
or overextension leading to neuropraxia. An alternative is
to place the arms alongside the torso if there are physical
limitations that prevent the former position. Access to
monitoring devices is limited in this position.
Regardless of the position, the ulnar nerve is at high
risk of damage, which may occur in spite of one’s best
efforts to protect it. The mechanisms behind the damage
are not altogether clear , and prev entati ve measures cannot
be implemented without definitive causation. Nevertheless, it is imperative to avoid pressure or excessive
stretching of the ulnar nerve at the elbow (5).
A number of devices are commercially available for
surgery in the prone position. These range from the simple (e.g., firm blocks to be placed under the hips and
chest) to the sophisticated (e.g., the Andrew’s table).
These devices are designed to avoid pressure on the
abdomen and thereby avoid splinting of the diaphragm
and minimal epidural bleeding from abdominal compression. As intra-abdominal pressure increases, the vertebral
venous pressure raises in parallel with raising pressure of
the inferior vena cava (IVC) (6–8). Appropriately designed surgical frames have been proved to reduce the
pressure within the IVC compared with more conventional chest rests (9). Reduction of intra-abdominal and
IVC pressure lower blood loss (10). The spinal frame
used in our institution is shown in Figure 18-1. The iliac
crest padded supports are modifiable to accommodate
different patient sizes. The frame is radiolucent to allow
biplanar fluoroscopy.
Approximately 20% of patients operated in the prone
position using iliac crest support frames complain postoperatively of symptoms linked to neurapraxia of the lateral cutaneous nerve of the thigh. This is more common
in obese individuals and where the surgery is prolonged
204 /SECTION IV/SURGERY
FIG. 18-1. Spinal frame. The iliac crest padded suppor ts are modifiable to accommodate for different
patients’ sizes. The frame is radiolucent to allow biplanar fluoroscopy.
(over 2 hours). In most cases, the neurapraxia fully resolves within 6 weeks.
KNEE-CHEST POSITION
One of the potential advantages of the knee-chest position over iliac crest support frames for lumbar spine
surgery is the greater opening of the interlaminar space
compared to the iliac crest support frame. However, it is
possible that the dural sac and individual nerve roots may
be under increased tension in this position; therefore, safe
retraction of the neural tissue may be more difficult to
achieve. Potential circulatory disturbance in the legs
should be carefully monitored in view of the significant
bend at the knees. It is common for older individuals to
complain after the surgery of increased knee pain, especially if patello-femoral osteoarthritis is present preoperatively.
Intraoperative preservation of the physiologic lumbar
lordosis may become critical when stabilization procedures are performed. A decrease in the lordosis angle has
been correlated with increased symptoms and gait abnormality following lumbar fusion (11–13). The hip flexion
angle relates to lumbar lordosis (14–16), and it appears
that iliac crest support–type frames may lead to better
maintenance of physiologic lumbar lordosis compared
with knee-chest devices because they involve less flexion
of the hip joint.
LATERAL DECUBITUS
This position may be used when the upper lumbar
spine is approached retroperitoneally. In most cases, the
approach is carried out through the left side with the
patient lying onto his or her right side. The right (bottom)
knee is flexed to approximately 90° with the left (upper)
knee extended. An axial pad is placed just underneath the
waistline, and the pelvis and head of the fibula are protected with adequate padding. The patient’s right upper
extremity is placed on the operating table with the left
side in a padded gutter arm support. An axillary roll may
be used to take pressure off the brachial plexus to avoid
disabling postoperative neurapraxia.
BLOOD CONSERVATION
The requirement for blood transfusion depends on a
multitude of factors, not the least of which is an agreement on the threshold hemoglobin before transfusion.
Most departments of transfusion medicine have guidelines for transfusion that have reduced the threshold level
from a previously accepted level of 100 g/L (10 g/dL). In
the absence of confounding comorbid disease, there is little indication for transfusion unless the hemoglobin concentration has fallen below 80 g/L (8 g/dL) in the absence
of ongoing blood loss.
A number of strategies have been proposed to reduce
the incidence of homologous transfusion. These include
autologous predonation, isovolemic hemodilution and
perioperative cell salvage. Autologous predonation can
be logistically difficult and costly to institute; it may
result in a relaxation of the transfusion trigger and result
in inappropriate transfusion; it does not remove the risk
of clerical error; and it does not remove the risk of transmission of bacterial infection. If the blood is harvested
but not reinfused, it is not suitable to be used in the general blood pool and therefore becomes an expensive and
useless commodity.
Isovolemic hemodilution refers to the practice of harvesting a quantity of blood at the beginning of a procedure and replacing it with a crystalloid or colloid solution
to prevent a fall in circulating volume. This has the effect
of immediately reducing the hemoglobin concentration
and therefore reducing the amount of hemoglobin lost per
volume of shed blood. Providing the blood has been harvested correctly, it will contain fresh platelets and coagulation factors not usually present in stored blood. In addition, the harvested blood can be processed to extract a
platelet concentration rich in growth factors, which may
be of benefit to osteogenesis at the surgical site. The har-
CHAPTER 18/PREPARATION FOR SURGERY / 205
vested blood can then be reinfused during the later stages
of the operation.
Perioperative cell salvage has been extensively used as
a blood conservation technique. Despite the equipment
becoming increasingly sophisticated, its application is
still limited to those procedures where blood loss is anticipated to be excessive, such as more extensive and
lengthy spinal procedures.
BLOOD LOSS AND THE SURGICAL FIELD
It is important to realize that the second arm of blood
conservation techniques are directed at reducing blood
loss to optimize the surgical field. A number of basic
strategies should be employed; these are summarized in
Table 18-2. Remember that bleeding can be venous or
arterial.
Venous bleeding occurs predominantly from the epidural veins, which are in communication with the IVC.
Therefore, strategies to reduce IVC pressure reduce
epidural venous pressure. Positive pressure ventilation
tends to reduce venous return and increase IVC pressure.
Consequently, efforts to limit the positive inspiratory
pressure while maintaining appropriate gas exchange
should be made. This can be achieved by maintaining an
adequate level of neuromuscular blockade, together with
adjustments of inspiratory time, pressure, and flow rate.
Appropriate use of bronchodilating drugs may help in the
bronchospastic patient. Positive end expiratory pressure
(PEEP) should be avoided (17). Careful positioning on a
suitable support system avoids abdominal compression.
This has been shown to reduce IVC pressure with reduction in epidural venous pressure. This position also a voids
diaphragmatic splinting from abdominal compression,
which would otherwise cause a rise in ventilatory inflation pressure and increase IVC pressure (18).
Avoiding vasodilatation and reducing the perfusion
pressure can reduce arterial bleeding. Vasodilatation can
be minimized by controlled hyperventilation to produce
hypocapnia. The perfusion pressure can be reduced by a
number of pharmacologic interventions that come under
the broad heading of hypotensive anesthesia. A wide
range of drugs has been used to induce hypotension under
anesthesia; a full discussion on the relative merits can be
found elsewhere (19). Ho wever , h ypotensi v e anesthesia is
TABLE 18-2. Strategies for minimizing blood loss
Prevent venous bleeding Reduce arterial bleeding
Avoid abdominal compression Control heart rate
Avoid diaphragmatic splinting Hyperventilate to
hypocapnia
Minimize peak inspiratory Induce hypotension
pressure
Avoid positive end expiratory
pressure
not without its complications and consideration must be
given to the risk-benefit assessment for each individual
patient. The risks of hypotensive anesthesia are hypoperfusion of vital organs, principally those organs whose
function is not conventionally monitored. The CNS is of
prime concern. Cerebral hypoperfusion may lead to a
range of postoperative complications from short-term
confusion and disorientation to massive cerebral infarction. Although cerebral autoregulation maintains cerebral
blood flow through a range of blood pressure variations,
blood flow is pressure dependent beyond the extremes of
these variations. Volatile anesthetic agents may offer
some cerebral protection by reducing cerebral metabolic
oxygen consumption. A more scientific method of determining adequacy of cerebral blood flow is to monitor
jugular bulb oxygenation or cerebral blood flow by
means of transcranial Doppler. These techniques are
becoming recognized as having a role to play in carotid
vascular surgery and neurosurgery, but their role in
hypotensive anesthesia outside of these domains has yet
to be determined. In addition, spinal cord ischemia may
occur if blood flow through the anterior spinal artery is
compromised. The effects of hypoperfusion of the CNS
may be exacerbated by hyperventilation and consequent
hypocarbia leading to vasoconstriction deliberately induced to reduce bleeding.
Modern volatile anesthetic agents are an attractive
option to induce hypotension. Agents, such as isoflurane
and sevoflurane, with relatively low blood-gas solubility
coefficients cause depression of medullary cardiac centres while depressing myocardial contractility directly.
This leads to a reduction in cardiac output and a fall in
blood pressure. Because of their low solubility, changes
in inspired volatile agent concentration lead to rapid
changes in blood concentration. This offers a level of
titratability that makes them useful agents for inducing
hypotension without a prolonged recovery time.
A special mention should be made regarding perioperative β-blockade. In addition to its advantageous effects
on slowing heart rate and reducing force of contractility
and thereby reducing blood pressure, evidence is becoming availab le that the use of perioperati ve β-b lockade ma y
reduce the all-cause mortality in high risk surgical patients undergoing noncardiac surgery (20–22). Their
potential benefit to patients who are not considered high
risk is yet to be determined (23).
A conservative approach to hypotensive anesthesia for
surgery on the lumbar spine would be to use β-adrenergic
blockade with atenolol for a target heart rate of 60 to 70
beats per minute and a volatile anesthetic agent 0.5 to 1.5
µg/kg clonidine to provide a modest fall in blood pressure
but maintain a mean arterial pressure above 70 mm Hg.
By using a drug such as clonidine with a long half-life
(compared to agents such as sodium nitroprusside), the
problems of rebound hypertension or rapid return to normotension are avoided.
206 /SECTION IV/SURGERY
Finally, two additional concerns must be addressed.
First, the negative impact of perioperative hypothermia
on the incidence of wound infection has been investigated (24,25). Hypothermia leads to increased shivering
in the immediate postoperative period, which increases
the basal metabolic rate. This increases respiratory and
myocardial work and can be relevant in patients with
impaired cardiorespiratory function to the point of precipitating cardiorespiratory failure. In addition, hypothermia has an adverse effect on normal hemostatic
function. Although major blood loss is uncommon in
most surgery on the lumbar spine, the impact of moderate hypothermia, below 35°C, on platelet function and
the coagulation cascade must be considered (26,27). If
efforts to create a bloodless surgical field are to be successful, meticulous attention to detail is required. This
should include the avoidance of hypothermia by the use
of appropriate warming devices. The introduction of
forced air warming devices, which direct warmed air
through an inflatable blanket to provide body surface
heating, has been a huge advance in this field (28). Most
of the work on the effects of hypothermia and coagulation has been done on either trauma or cardiopulmonary
bypass patients. Further work needs to be done on patients undergoing elective noncardiac surgery. Nevertheless, it seems prudent to minimize hypothermia for
the reasons mentioned in the preceding.
Finally, what is the role of the serine protease inhibitor,
aprotinin, and the lysine analogs, tranexamic acid and
aminocaproic acid? Both of these groups of agents have
been shown to be beneficial in cardiac surgery or knee
arthroplasty (29–31). T ranexamic acid has been shown to
be beneficial in pediatric scoliosis surgery (32). The
emphasis has been on the reduction in blood transfusion.
The role of these agents in reducing bleeding to improve
the surgical field has yet to be determined.
ANTIBIOTICS
Infection rates with spinal surgery vary widely among
published series and according to the type of surgery performed. Wimmer et al. reported on 22 cases out of 850
clean spinal procedures with an overall infection rate of
2.6% (33). In that study, it was suggested that extended
preoperative hospitalization, large intraoperative blood
loss, and prolonged operating time were correlated with
increased risk of postoperative infection. The authors also
suggested that routine prophylactic antibiotics ma y not be
necessary, although parenteral postoperative antibiotic
should be administered when segmental instrumentation
is used.
The overall risk of infection is higher in acute trauma
than in elective surgery. Patients with significant preoperative neurologic def icit are also at higher risk. It has
been shown that penetration of antibiotics into the disc is
poor and that a critical relationship exists between serous
antibiotic concentration and disc antibiotic levels that
may have a prophylactic effect on infection. It has been
suggested that antibiotic concentration within the disc is
highest between 15 and 80 minutes follo wing intravenous
administration (34).
Prophylactic administration of antibiotics should be
considered mandatory for all procedures that may violate
the intervertebral disc. In experimental studies where
lumbar intervertebral discs were inoculated with staphylococcus epidermidis cultures, no discitis developed with
prophylactic intravenous or intradiscal administration of
cephalosporins, whereas large doses of antibiotics administered following the inoculation of bacteria into the disc
did not prevent disc infection (35,36).
Different classes of antibiotics hav e been demonstrated
to penetrate the intervertebral disc at different rates.
Aminoglycosides and glycopeptides appear to penetrate
into the nucleus pulposus well, whereas penicillins and
cephalosporins have been proven to enter the disc at
much lower concentrations. Prophylactic antibiotics are
even more critical when percutaneous disc procedures are
performed. The administration of antibiotics should be
planned so that the highest intradiscal concentration may
be achieved when the surgical insult to the disc is likely
to occur. Maximal antibiotic concentration in the disc, as
indicated, occurs 15 to 80 minutes following parenteral
antibiotic administration; the likely average time for
broad-spectrum antibiotics is 30 to 45 minutes.
POSTOPERATIVE PAIN MANAGEMENT
The mainstay of acute pain management is opioid analgesia. Postoperative analgesia should be administered by
a route that offers rapid onset and the ability to titrate the
dose to achieve optimal effect. The intravenous route is
the most suitable in the recovery unit, where the patient
can be closely monitored for the adverse effects of opioids. Central nervous system depression is initially manifest and may then present with more serious effects, such
as respiratory depression. A simple sedation score can be
used as an early warning sign for the clinician before
more significant CNS depression occurs. Figure 18-2
gives the protocol for intravenous opioid loading used at
the Royal Adelaide Hospital. Once therapeutic plasma
concentrations of opioid analgesics have been achie v ed, it
is appropriate to convert to a patient controlled analgesia
(PCA) system. Most institutions have a protocol for drug
concentration, bolus dose, and lockout time to be used for
PCA. A simple protocol for the fit patient under 65years
of age is the following:
• Morphine: 1 mg/mL
•Bolus dose: 1 mg
• Lockout time: 5 minutes
The bolus dose can be increased if analgesia is inadequate and decreased if excessive sedation occurs. It is
CHAPTER 18/PREPARATION FOR SURGERY / 207
Y
Y
Y
Y
Y
t
d
t
d
Sedation Score
0 None
1 Mild: occasionally
2 Moderate: constantly
3 Severe: somnolent,
S Normally Asleep
drowsy, easy to rouse
drowsy, easy to rouse
difficult to rouse
Routine observations
NO
ES
Pain?
WAIT 3 min
Give 1ml IV Give 0.5ml IV
BEGIN
Pain?
NO
YES
“Pain Protocol” and
opioid ordered?
NO
ES
Prepare in Saline
morphine 1mg/ml, or
fentanyl 20 micrograms/ml
ES
Is sedation score less than 2?
NO
Seek
medical
advice
YES
Is respiratory rate greater than 8/min?
ES
NO
B.P. OK?
NO
Seek
medical
advice
Seek
medical
advice
YES
Under 70 years old?
NO
ES
Severe pain?
s
n
1
or 2
dose? 1
Some relief with last 2 doses? Some relief with last 2 doses?
YES YES
NONO
Routine observations
Get order
Draw up 10mg morphine or
200 micrograms fentanyl and
make up to 10ml with saline
Draw up 20mg morphine or
400 micrograms fentanyl and
make up to 20ml with
Hold further doses until sedation
score less than 2 and respiratory
rate greater than 8/min. Consider
use of naloxone 100 microgram
Severe pain?
YESYES
s
n
or 2
dose?
NONO
YESYES
10ml syringe
20ml syringe
saline
increments IV.
NONO
Give 4ml IV Give 1ml IVGive 1ml IVGive 2ml IV
Give 2ml IV
FIG. 18-2. Guidelines for intravenous opioid administration.These guidelines are/should: (1) Only to be
used by staff in recovery wards who hav e been instructed in this technique;(2) NOT appropriate for routine maintenance of analgesia in general wards; (3) Note that the peak effect of an intravenous dose
may not occur for over 15 minutes, therefore all patients should be observed closely during this time;
(4) All patients receiving repeated doses of IV opioids should be ordered oxygen; and (5) “Pain Protocol” should cease when the patient is comfor table (they will not necessarily be pain free). From The
Acute Pain Service, Royal Adelaide Hospital, with per mission.
208 /SECTION IV/SURGERY
generally accepted that a background infusion ordinarily
should not be prescribed because it appears not to
improve the analgesia but may increase the incidence of
side effects (38).
Morphine should be the f irst line agent of choice, but
fentanyl can be used as an alternative. Meperidine (pethidine) should be avoided if feasible because of the possibility of CNS toxicity associated with its metabolite,
normeperidine (norpethidine). Normeperidine plasma
concentrations can be achieved with PCA pethidine and
can lead to CNS excitability, and manifest as agitation
and even convulsions (39,40).
It is worth considering the use of adjuvant analgesic
agents that do not specifically target opioid receptors. Use
of nonspecific cyclooxygenase inhibitors may increase
intra and post-operative bleeding and should be avoided.
However, the more recently released selective cox-2 inhibitors (celecoxib and parecoxib) may have a role to play
and further investigation of these drugs is warranted. Similarly, centrally acting drugs that are α-adrenergic agonists
stimulate the descending spinal inhibitory pathways. These
pathways originate in the periaqueductal gray matter and
reticular formation, to run in the dorsolateral fasciculus.
They synapse in the substantia gelatinosa of the dorsal horn
where norepinephrine and serotonin are released. They are
involved in the highly complex system of interneurons,
which modify nociceptive input to the spinal cord. Clinical
data do not support the use of clonidine by the epidural or
intrathecal route with conflicting data on its analgesic efficacy. However, its sedative effects may be beneficial in
patients with a high preoperative opioid intake. Similarly,
tramadol may be beneficial by preventing reuptake of noradrenaline and serotonin at the spinal cord level. It has only
weak intrinsic opioid activity and is thought to exert its
effects at a supraspinal or spinal cord level.
Finally, if pain control in the immediate postoperative
period is difficult, ketamine by intravenous infusion of 2
to 8 mg/hour (depending on age and comorbid disease)
can be used. Ketamine is the only clinically available
NMDA (N-methyl-D-aspartate) receptor antagonist and
provides analgesia at the spinal cord level where NMDA
is an excitatory neurotransmitter.
ACKNOWLEDGMENT
Hiroaki Nakamura’s contribution was supported by a
grant from Medtronic-Sofamor Danek International.
REFERENCES
1. Noble DW, Kehlet H. Risks of interrupting drug treatment before
surgery. BMJ 2000; 321:719 –20
2. Stack CG, Rogers P, Linter SP. Monoamine oxidase inhibitors and
anaesthesia. Br J Anaesthesiol 1988;60:222.
3. Fobe F, Kestens-Servaye Y, Baele P, et al. Heart transplant and
monoamine oxidase inhibitors. Acta Anaesthesiol (Belgium) 1989;40
(2):131–138.
4. Ure DS, Gillies MA, James KS. Safe use of remifentanil in a patient
treated with the monoamine oxidase inhibitor phenelzine. Br J Anaesthesiol 2000;84(3): 414–416.
5. Practice advisory for the prevention of perioperative peripheral neuropathies. Anesthesiology 2000;92(4):1168–1182.
6. Distefano VJ, Klein KS, Nixon JE, et al. Intraoperative analysis of the
effects of position and body habitus on surgery of the low back. A preliminary report. Clin Orthop 1974;99:51–56.
7. McNulty SE, Weiss J, Azad SS, et al. The effect of the prone position
on venous pressure and blood loss during lumbar laminectomy. J Clin
Anesthesiol 1992;l4:220–225.
8. Wayne SJ. The trunk position for lumbar-disc surgery. J Bone Joint
Surg 1967;49:1195–1198.
9. Lee TC, Yang LC, Chen HJ. Effect of patient position and hypotensive
anaesthesia on inferior vena caval pressure. Spine 1998;23:941–948.
10. Sivarajan M, Amory DW, Everett GB, et al. Blood pressure not cardiac
output, determines blood loss during induced hypotension. Anesthesiol
Analg 1980;59:203.
11. Grobler Lj, Moe JH, Winter RB, et al. Loss of lumbar lordosis following surgical correction of thoracolumbar deformity. Orthop Trans
1978;2:239–244.
12. Hasty CA, Passoff TL, Perry J. Gait abnormalities arising from iatrogenic loss of lumbar lordosis secondary to Harrington instrumentation
in lumbar fractures. Spine 1983;8:501–511.
13. Wasylenko MJ, Skinner S, Per ry J. Analysis of posture and gait following spinal fusion with Harrington instrumentation. Orthop Trans
1981;5:21–25.
14. Tan SB, Kozak JK, Dickson JH, et al. Effect of operative position on
sagittal alignment of the lumbar spine. Spine 1994;19:314–318.
15. Steohens CG, Yoo JU, W ilbur G. Comparis on of lumbar sagittal alignment
produced by different operative positions. Spine 1996;21:1802–1807.
16. Benfanti PL, Geissele AE. The effect of intraoperative hip position on
maintenance of lumbar lordosis. Spine 1997;22:2299–2303.
17. Mitaka C, NaguraT, TsunodaY, et al. Two-dimensional echocardiographic evaluation of inferior vena cava, right ventricle and left ventricle during positive pressure ventilation with varying levels of positive
end-expiratory pressure. Crit Care Med 1989;17(3):205–210.
18. Lee TC, Yang LC, Chen HJ. Effect of patient position and hypotensive
anaesthesia on inferior vena caval pressure. Spine 23(8):941–947.
19. Miller RD. Anaesthesia, 4th ed. New York: Churchill Livingstone, 1994.
20. Auerbach AD, Goldman L. β-Blockers and reduction of cardiac events
in noncardiac surgery: scientific review. JAMA 2002;287(11):
1435–1444.
21. Mangano DT, Layug EL, Wallace A, et al. Effect of atenolol on mortality and cardiovascular morbidity after noncardiac surgery. Multicenter Study of Perioperative Ischemia Research Group. N Engl J Med
1996;335(23):1713–1720.
22. Jones KG, Powell JT. Slowing the heart saves lives: advantages of perioperative beta-blockade. Br J Surg 2000;87(6):689–690.
23. Howell SJ, Sear JW, Foex P. Peri-operative beta-blockade: a useful
treatment that should be greeted with cautious enthusiasm. Br J Anaesthesiol 2001;86(2):161–164.
24. Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce
the incidence of surgical-wound infection and shorten hospitalization.
Study of Wound Infection and Temperature Group. N Engl J Med
1996;334(19):1209–1215.
25. Beilin B, Shavit Y, Razumovsky J, et al. Effects of mild perioperative
hypothermia on cellular immune responses. Anesthesiology 1998;89
(5):1133-1140.
26. Watts DD, Trask A, Soeken K, et al. Hypothermic coagulopathy in
trauma: effect of varying levels of hypothermia on enzyme speed, platelet
function, and fibrinolytic activity. J Trauma 1998;44(5):846–854.
27. Reed RL 2nd, Bracey AW Jr, Hudson JD, et al. Hypothermia and blood
coagulation: dissociation between enzyme activity and clotting factor
levels. Circ Shock 1990;32(2):141–152.
28. Giesbrecht GG, Ducharme MB, McGuire JP. Comparison of forced-air
patient warming systems for perioperative use. Anesthesiology 1994;
80(3):671–679.
29. Hiippala S, Strid L, Wennerstrand M, et al. Tranexamic acid (Cyklokapron) reduces perioperative blood loss associated with total knee
arthroplasty. Br J Anaesthesiol 1995;74(5):534–537.
30. Casati V, Sandrelli L, Speziali G, et al. Hemostatic effects of tranexamic acid in elective thoracic aortic surgery: a prospective, randomized, double-blind, placebo-controlled study. J Thorac Cardiovasc Surg
2002;123(6):1084–1091.
31. Benoni G, Fredin H. Fibrinolytic inhibition with tranexamic acid
CHAPTER 18/PREPARATION FOR SURGERY / 209
reduces blood loss and blood transfusion after knee arthroplasty: a
prospective, randomised, double-blind study of 86 patients. J Bone
Joint Surg Br 1996;78(3):434–440.
32. Neilipovitz DT, Mur to K, Hall L, et al. A randomized trial of tranexamic acid to reduce blood transfusion for scoliosis surgery. Anesthesiol
Analg 2001;93(1):82–87.
33. Wimmer C, Gluch H, Franzreb M, et al. Predisposing factors for injections in spine surgery: a survey of 850 spinal procedures. J Spinal Disord 1998;11:124–128.
34. Guiboux J-P, Cantor JB, Small SD, et al. The effect of prophylactic
anti-biotics on iatrogenic intervertebral disc infection: rabbit model.
Spine 1995;20:685–688.
35. Fraser RD, Osti OL, Vernon-Roberts B. Discitis after discography. J
Bone Joint Surg 1987;69B:26–35.
36. Osti OL, Fraser RD, Ver non-Roberts B. Discitis after discography.
The role of prophylactic anti-biotics. J Bone Joint Surg 1990;72B:
271–274.
37. Owen H, et al. Variables of patient controlled analgesia 2 Concurrent
infusion. Anaesthesia 1989;44:11–13.
38. McHugh GJ Norpethidine accumulation and generalized seizure during pethidine patient-controlled analgesia. Anaesthesiol Int Care 1999;
27(3):289–291.
39. Stone PA, Macintyre PE, Jarvis DA. Norpethidine toxicity and patient
controlled analgesia. Br J Anaesthesiol 1993;71(5):738–740.
CHAPTER 19
Surgical Approaches to the Thoracolumbar Spine
Scott D. Daffner and Todd J. Albert
The thoracolumbar spine offers numerous challenges in
treatment, particularly with regard to anterior surgical
approaches. The unique biomechanics of this re gion, particularly the transition from thoracic kyphosis to lumbar
lordosis, put it at increased risk for degeneration. In addition, a wide variety of traumatic and neoplastic conditions may also affect the thoracolumbar spine.
Two basic surgical approaches exist for surgery in this
region—anterior and posterior. Posterior approaches are
most frequently used for procedures involving the posterior elements, although modifications of the posterior
exposure may allow access to the anterior portion of the
spine. Anterior approaches are generally required for
access to the vertebral body itself. In addition, combined
anterior and posterior approaches are occasionally used,
depending on the type of pathology, the extent of the
injury, and the judgment of the physician.
BONY AN ATOMY OF THE THORACOLUMB AR
SPINE
The thoracolumbar region represents the transition
from one type of vertebral body to another. Thoracic vertebrae are generally smaller than those of the lumbar
region. Their facet joints are oriented more frontally, the
spinous process is longer and angled more distally, the
pedicles are narrower and shorter, and the articulations
with the ribs distinguish the thoracic vertebrae. The short
transverse processes are angled posterolaterally, articulating with the ribs (1,2).
The lower thoracic vertebrae begin to resemble lumbar
vertebrae. Their facet joints change from a frontal orientation to one that more closely resembles those of the
lumbar vertebrae in which the superior articular facets
are anterolateral to the inferior articular facets of the vertebra above and are directed dorsomedially. From L1 to
L5, the pedicles become larger in diameter and become
more medially oriented (1,2).
Several ligamentous structures stabilize the bony elements of the vertebrae (Fig. 19-1). The supraspinous and
interspinous ligaments connect the spinous processes,
while the intertransverse ligaments segmentally connect
the transverse processes. The ligamentum flavum passes
between the ventral side of the lamina to the superior lip
of the next caudal lamina. The ligamentum flavum has a
midline raphe, providing a convenient plane through
which the canal may be entered. The broad anterior longitudinal ligament runs the length of the spinal column,
intimately integrated with the periosteum of the anterior
vertebral body, while the posterior longitudinal ligament
lies along the posterior aspect of the vertebral body,
adhering strongly to the intervertebral discs.
POSTERIOR APPRO A CH
The most commonly used approach to the spine is the
posterior approach (3). This approach differs little along
the entire length of the spine, and is used for laminectomy
and posterior, transpedicular, or posterolateral fusion.
Posterior Anatom y
To fully appreciate this approach, one must understand
the anatomy (Fig. 19-2).The muscular layers of the back
can be divided into three distinct layers (Fig. 19-3). The
superficial layer consists of the trapezius, which inserts
on the T12 spinous process most caudally, and the latissimus dorsi which arises from the spinous processes and
inserts onto the humerus. The intermediate layer is composed of the serratus posterior inferior, while the deep
layer includes the erector spinae group (spinalis, longissimus, and iliocostalis) lying superficial and lateral to the
210
CHAPTER 19/SURGICAL APPROACHES TO THE THORACOLUMBAR SPINE / 211
FIG. 19-1. Ligamentous stabilization of the vertebra and ribs.
(From Albert TJ, Balderston RA, Nor thrup BE, eds. Surgical
approaches to the spine. Philadelphia: WB Saunders, 1997,
with permission.)
transversospinalis group (rotatores, multifidus, and semispinalis). These latter muscle groups are often detached
as a single mass during this approach. The bony structures revealed during this approach include the spinous
processes, laminae, and transverse processes. The facet
joint capsules are also visualized from this approach.
FIG. 19-2. Axial view demonstrating posterior exposure of
the thoracolumbar spine. (From Albert TJ, Balderston RA,
Northrup BE, eds. Surgical approaches to the spine.
Philadelphia: WB Saunders, 1997, with permission.)
Surgical Technique
The patient is placed in either the prone or kneeling
position with the abdomen hanging free to reduce pressure on the abdomen and thereby reduce epidural venous
pressure and decrease intraoperative bleeding (F ig. 19-4).
It is important to pad all bony prominences (2,3).
The skin incision is made in the midline over the spinous processes at the appropriate level. The incision is carried down through the subcutaneous tissue to the deep
fascia. By dissecting the deep fascia subperiosteally from
the spinous processes, one can preserve the attachments
of fascia and can avoid bleeding from intramuscular
blood vessels. The erector spinae muscles should be gently retracted with a Cobb elevator, helping to avoid straying into the musculature (Fig. 19-2). Subperiosteal dissection should be carried out in a caudal to cephalad
direction. The dissection may be extended laterally to
facilitate posterolateral fusion or pedicular instrumentation. Unless a facet fusion is planned, care should be
taken to av oid subperiosteal dissection into the facet joint
(2). Transverse processes may be palpated inferolateral to
the facet joint by following the base of the superior articular process out laterally. After defining the superior and
inferior borders of the transverse process, electrocautery
may be used to continue the subperiosteal dissection of
the segmental musculature, taking care to preserve the
intertransverse ligament.
This approach may be extended to allow exposure of
the posterior and anterior spinal elements. The extended
posterior approach is primarily used for tumor resection
and for osteotomies. The extensive nature of this
approach may increase the risk for neurovascular damage, including spinal ischemia. The skin incision is
extended three or four levels proximal and distal to the
desired level of resection. The contents of the spinal canal
may be visualized by performing a complete laminectomy. In the low thoracic region, ribs may be divided lateral to the costotransverse joints. If the pleura is entered,
a chest tube may need to be inserted. Mobilizing the vascular structures may require ligation of the segmental
vessels. The vertebral bodies may then be excised
through the disc space above and below the pathology.
Posterior stabilization should be performed before the
anterior vertebral body resection to avoid neurologic
compromise resulting from a completely destabilized
spine (1).
Complications associated with the posterior approach
may be minimized by careful planning and meticulous
surgical technique. Identification of the appropriate level
should be verified by taking an intraoperative radiograph.
Neural elements, including nerve roots, must be clearly
identified and protected. Excessive bleeding may be minimized by performing a subperiosteal dissection. Identification and cauterization of the segmental facetal artery
lateral to the pars will minimize bleeding as the dissec-
212 /SECTION IV/SURGERY
A
B
FIG. 19-3. Superficial, intermediate, and deep muscular layers of the back. (From Albert TJ, Balderston
RA, Northrup BE, eds. Surgical approaches to the spine. Philadelphia: WB Saunders, 1997, with permission.)
tion is carried out laterally. Epidural bleeding may be
controlled by using Gelfoam or thrombin-soaked pledgets and bipolar cautery (2).
ANTERIOR APPRO A CHES
Two basic anterolateral approaches to the thoracolum-
bar spine may be used. These are the transpleural
retroperitoneal and the retropleural retroperitoneal
approaches. While the transpleural approach provides
excellent exposure of the anterior vertebral column over
a number of segments, it involves extensive soft-tissue
dissection and the rib head may impair visualization. In
addition, bleeding from the epidural veins may be diff icult to control. The retropleural approach is more lateral
than the transpleural approach. Because the rib head and