Anesthesia for spine surgery

1. ANESTHESIA FOR SPINE SURGERY
Dr. Ashraf Arafat Abdelhalim , MD
Professor
Department of Anesthesia, Alexandria University,
Egypt
1

2. Anesthetic considerations
Trauma for fixation of a spine
Tumor for resection
Degenerative diseases
Correction of deformity as scoliosis
Protrusion of intervertebral disc
Spondylosis
Infection & abscess drainage
Vascular malformation
2

3. Anesthetic problem
Patient position
Increased blood loss
Spinal cord protection
Postoperative blindness
Problem related to site
Cervical :
 Difficult intubation,
 Anterior approach : pneumothorax & CVS changes
 Postoperative edema , brain stem, neck & airway
3

4. Thoracic : Thoracotomy & one lung anesthesia
Lumber : spinal and epidural can be used
Problem related to the cause:
 Acute spinal cord injury complication
 Chronic spinal cord injury complication
Ankylosing Spondylitis, rheumatoid Arthritis &
kyphoscoliosis
Congenital abnormality e.g. Down s
syndrome
4

5. Pre-Operative Assessment
Airway Assessment: .
 Mallampatti classification
 Mouth opening .
 Previous difficulty in intubation .
 Restriction of neck movement .
 Stability of the cervical spine .
 Neurological Assessment: documented
 Co existing diseases : rheumatoid arthritis
is essential to discuss preoperatively the
stability of the spine with the surgeon.

6. RESPIRATORY SYSTEM:
 Any existing ventilatory impairment
 Any signs of pulmonary infection, asthma etc
 Spine deformities eg. Scoliosis kyphosis ankylosis etc.
 Cardiovascular System :
 Besides routine examination: B.P, heart sounds,
History: Hypertension Diabetes mellitus, Congestive
heart failure, Coronary artery disease
 Renal and Liver function assessment
 In Traumatic Spinal Injury: associated injuries eg,
tracheal major vessels, esophagus,, 6

7. Neurological assessment:
 The full neurological assessment should be documented.
 In C-spine surgery, the anesthesiologist should avoid
further neurological deterioration .
 Muscular dystrophies may involve the bulbar muscles,
increasing the risk of postoperative aspiration.
 The level of injury and the time elapsed since the insult
are predictors of the physiological derangements of the
CVS and respiratory systems which occur perioperatively.
 In < 3 weeks of the injury, spinal shock may still be
present. After this time, autonomic dysreflexia may occur.
7

8. Suggested preoperative investigations before major
spinal surgery
Minimum investigations
Airway:
 x-rays Cervical spine lateral
view with flexion/extension
Pulmonary:
 CXR
 ABG
 Spirometry (FEV1, FVC)
 CVS:
 ECG Dobutamine-stress Echo
Echocardiography Dypiridamole
Thalliuscintigraphy Blood tests:
CBC,Blood sugar, electrolytes,
RFT, LFT, B.T,C.T. PT/PTT
Calcium (neoplastic disease)
Optional investigations
 CT scan
 Pulmonary function
tests(bronchodilator
reversibility)
 Pulmonary diffusion
capacity
8

9. Anesthesia technique
Premedication:.
 Avoid heavy sedation if there is respiratory
impairment
 Anticholinergic : prevent wetting of tape of ETT
 Facilitate fiberopic bronchoscopy
 Protection a gainst aspiration: H2 blockers
 NSAIDs should be stopped at least
10days before elective surgeries
9

10. Induction:
Choice of induction technique:
 i.v. or inhalation ?
 Etomidate is of choice
 Thiopentone or propofol , but avoid large doses in
spinal shock
 Airway
 C-spine stability
Consider using a wire reinforced tube to avoid tube
kinking and occlusion
Patients with C spine disease have a high incidence of
difficult intubation. 10

11. Choice of muscle relaxants:
 Succinycholine or NDNMBs ?
 Pt’s medical condition
 Airway
 Risk of aspiration
 Intra-operative S. choline can be used in first 24
hours after injury, avoided between 1-2 days up to 6-8
months after injury
Avoid S. choline if malignant hyperthermia is
suspected e.g. scoliosis
11

12. Awake or asleep
Attention to minimizing motion of the C-spine
Positioning may be associated with the risk of
neurologic injury
12

13. Direct or fiber-optic laryngoscopy
Direct laryngoscopy: Intubation can be achieved without any
neck movement (manual in-line stabilization or a hard collar)
Fiber-optic laryngoscopy:
 Fixed flexion deformities: involving upper T-spine/c-spine
 Pts wearing stabilization devices such as halo vests
 Anatomical reasons: micrognathia, limited mouth opening
13

14. Maintenance :
 Maintain a stable anesthetic depth
 Positioning of patient, check airways
 Avoid sudden changes in anesthetic depth or BP
 Maintain a constant depth of NMB
 Maintain stable hemoglobin & to avoid over
hydration
14

15. Maintenance
 Common practice:
 Inhalational with opioids :
 interfere with monitoring of SSEPs
 Total intravenous anesthesia: faster recovery especially if
SSEPs are monitored
 Opioids:
 not interfere with monitoring of SSEPs
 Stable depth of anesthesia
 Pain – free recovery
15

16. Intraoperative fluids therapy
Dextrose containing solution should be avoided
Hyperglycemia worsen ischemic neurological
injury
Avoid circulatory under- load : to avoid
severe hypotension
Avoid circulatory over- load : to avoid
pulmonary edema with left ventricular
dysfuction
16

17. Transfusion Management
Strategies : reduce the risk of allogeneic transfusion
 Preoperative autologous donation (PAD),
 Acute normovolemic hemodilution (ANH),
Perioperative cell salvage techniques (PCS),
 Deliberate hypotension
 Pharmacologic interventions (ANTIFIBRINOLYTIC )
 Combination of strategies
 Operative position to prevent abdominal
compression
 Surgical hemostasis
17

18. Reversal
 Patient made supine
 Thorough endotracheal and oral suction
 Oxygenated with 100% oxygen
 I.V.- Neostigmine Glycopyrolate
 Extubation:
 Fully awake with full motor power.
 Some patients may require postoperative ICU
 An airway exchange catheter (AEC) through
the ETT before its removal 18

19. Intraoperative Problems
Respiratory dysfunction : in case of traumatic
spinal cord injury
Intraoperative hypothermia: large sized
wounds, prolonged surgeries, loss of thermal
regulation in acute spinal cord injury
increased blood loss
Problems with Transthoracic approach:
thoracotomy and one lung ventilation
19

20. Problems with Anterior Cervical Approach:
Injury to trachea, esophagus, sympathetic
chain, carotid sheath, pneumothorax
Injury to RLN,
Spinal cord protection:
 Surgical decompression as soon as possible
 Corticosteroids as methyl prednisolone
 Hpothermia: local to damaged area
 NMDA receptor antagonist
 Ganglioside GM-1 20

21. IF SSEP is abnormal :
 Decreased amplitude more than 50%
 Increased latency more than 50%
 Complete loss of waveform
ACTION
 Inform the surgeons to search for the cause
 Adequate oxygenation
 Paco2 should be normalized
 ABP should be normalized or slightly increased
 Correct anemia and hypovolemia
 If persist, do wake up test
21

22. Postoperative care
Individualized for each patient
Most spinal surgery is painful
Local anesthetic and Opioid drugs can be
instilled into the epidural space before closing.
A regimen including patient-controlled
analgesia (PCA) combined with regular
oral/rectal analgesics is successful.
22

23. Postoperative complications
Early:
 Hypovolemia
 Neurologic injury or deficit,
 Dural tear with CSF leakage,
 Anemia,
 Urinary retention,
 ileus,
 atelectasis/pneumonia,
 Venous thrombosis
Late: skin breakdown, wound infection, spinal instability
,implant failure, epidural fibrosis, and more rarely,
arachnoiditis
23

24. Injuries: Eye
 Corneal abrasions
 Orbital edema
 Postoperative visual loss ( POVL)
Post-operative visual loss (POVL)
POVL is a rare but devastating complication
1/1100 after prone spinal surgery
Causes:
Ischemic optic neuropathy (ION) (81%)
Central retinal artery occlusion (13%)
Unknown diagnosis (6%).
24

25. Risk Factors for Postoperative Airway
Compromise
Patients undergoing multiple levels anterior C-spine
procedures may be at risk of post operative neck
and airway edema causing airway compromise.
 Operative time more than10hrs,
 Requirement for more than 4 unit transfusion,
 Obesity,
 Reoperations
 Operation of 4 or more cervical spine level or
involving C2
Epstein NE. J Neurosurg 94:185 2001

26. Respiratory care : especially if affected
preoperatively e.g. scoliosis
Deep breathing exercise
Incentive spirometry
Brochdilators,analgesics& mucolytics
Adequate hydration
Postoperative ventilation if needed
26

27. Positioning
 Prone position : most spinal procedures
 Supine position with head traction in anterior
approach to cervical spine
 Sitting or lateral decubitus position : occasionlly
27

28. Prone position
Induction and intubation in supine position
Turn prone as a single unit requiring at least 4 people
Neck should be in neutral position
Head may be turned to the side not exceeding the patients
normal range of motion or face down on a cushioned holder.
Arms should be at the sides in a comfortable position with the
elbow flexed ( avoiding excessive abduction at the shoulder
Chest should rest on parallel rolls (foams )or special
supports (frame) to facilitate ventilation
Check oral endotracheal tube, ckt, other attachments
Check breath sounds bilaterally
28

29. Anesthetic problems of the
prone position
Potential problems Comments
Airway
ET tube kinking or dislodgement
Edema of upper airway in prolonged
cases
Abdominal compression
Impaired ventilation Avoid abdominal compression as far
as possible
Decreased cardiac output Bean bag mattress or pillow are better
than the supportive frames or kneechest
position
29

30. Anesthetic problems of the prone position
Potential problems Comments
Eyes
Corneal abrasion Ensures eyes taped shut
Optic neuropathy Increased intraocular pressure
Decrease perfusion pressure
Reduce risk by avoiding compression
to the eyes, hypotension, low
hematocrit
Retinal artery occlusion Avoid pressure on the eyes
Head and Neck
Venous and Lymphatic
obstruction
Careful positioning to minimize
venous obstruction
Skull fixation Insertion of pins into skull can result in
a hypertensive response that is
difficult to control
30

31. Anesthetic problems of the prone position
Potential problems Comments
Damage to major vessel
Aorta and Venacava Accidental damage following
perforation of anterior longitudinal
ligament produces major bleeding into
wound. Present with acute reduction
of blood pressure and
electromechanical dissociation arrest
High mortality
Iliac vessel Less acute presentation. High degree
of suspicion to avoid delayed
diagnosis
Increased epidural venous pressure
bleeding
(frames elevates)
31

32. Anesthetic problems of the prone position
Potential problems Comments
Pressure necrosis of the nose, ear, forehead, breasts
(female),and genitalias (males)
Monitor disconnects hard to avoid; carefully manage.
Nerves:
Brachial plexus stretch or compression
Ulnar N compression: pressure to the olecranon
Peroneal N compression: pressure over the head of
the fibula
Lateral femoral cutaneous N trauma: pressure over the iliac crest
32

33. Spine Surgery- Monitoring
Routine
Arterial line
CVP/ PA catheter
Neurophysiologic: . Wake up test . SSEP .
MEP . EMG
33

34. Wake-up test
 Lightening anesthesia at an appropriate point during
the procedure
 Observing the patient’s ability to move to command.
 It evaluates the integrity of the motor pathway.
Anesthesia requirements:
 Reliable but quickly antagonized
 Wakening should be smooth
 No pain during the test
 No recall
34

35. Wake-up test
Anesthetic techniques:
 Volatile-based anesthesia
 Propofol-based anesthesia
 Remifentanyl-based anesthesia
Disadvantages:
 Requires pt’s co-operation
 Risky to pt: falling from the table and extubation
 Requires practice
 Prolong the duration of surgery
 Provides information at the time of the wake-up only
 Does not assess sensory pathways
35

36. SSEP (somato sensory evoked potentials)
 The most common neurophysiological method for
monitoring the intra-operative spinal functional
integrity
 The stimulus applied to the peripheral N (tibial or
ulnar)
 The recording electrodes placed: cervical region,
scalp, or epidural space during surgery
 Baseline data obtained after skin incision
36

37. SSEP (somato sensory evoked potentials)
 Responses are recorded intermittently during
surgery
 A reduction in the amplitude by 50% and an increase
in the latency by 10% are considered significant.
 SSEP tests only dorsal column function not motor
 Rarely - post operative neurologic deficit reported
despite preservation of SSEP intraoperatively
37

38. Indications for SSEP’s
Spinal instrumentation
Scoliosis correction
Spinal cord operations
38

39. Anesthetics and SSEPs
Satisfactory monitoring of early cortical SSEPs is
possible with 0.5–1.0 MAC isoflurane, desflurane or
sevoflurane.
Nitrous oxide potentiates the depressant effect of
volatile anesthetics
Intravenous anesthetics generally affect SSEPs
less than inhaled anesthetics
Etomidate and ketamine increases cortical SSEP
amplitude
Clinically unimportant changes in SSEP latency
and amplitude after the administration of opioids
39

40. Implication for SSEPs Monitoring
Eliminating N2O from the background anesthetic has
been shown to improve cortical amplitude and make
monitoring more reliable
SSEP latency will take 5–8 min to stabilize after the
step changes in volatile anesthetic concentration
Adding etomidate, propofol or opioids is
preferable to beginning N2O or increasing volatile
anesthetic concentrations when anesthetic depth is
inadequate
40

41. If a volatile anesthetic is needed rapidly, sevoflurane
permits faster SSEP recovery after the acute need for
volatile anesthetic has been resolved
It is critical to avoid sudden changes in volatile
anesthetic depth or bolus administration of
intravenous anesthetics during surgical
manipulations that could jeopardize the integrity of the
neural pathways being monitored
41

42. Anaesthetics and MEPS( Muscle evoke potentials)
Inhalational anesthetics suppress myogenic
MEPs in a dose- dependent manner
N2O appears to be less suppressive than other
inhaled agents.
 Moderate doses of up to 50% N20 have been used
successfully to supplement other agents during
myogenic MEP monitoring.
Fentanyl, etomidate, and ketamine have little or
no effect on myogenic MEP and are compatible with
intra-operative recording. 42

43. Benzodiazepines, barbiturates, and
propofol also produce marked
depression of myogenic MEP.
However, successful recordings have
been obtained during propofol anesthesia
by controlling serum propofol
concentrations and increasing stimuli
rates.
43

44. Anesthetics and MEPs
Myogenic MEPs are affected by the level of
neuromuscular blockade
By adjusting a continuous infusion of muscle
relaxant to maintain one or two twitches in a train of
four, reliable MEP responses have been recorded
Motor stimulation can elicit movement, and this can
interfere with surgery in the absence of neuromuscular
blockade
44

45. Physiologic factors such as temperature,
systemic blood pressure, PaO2, and PaCO2
can alter SSEPs/MEPs and must be controlled
during intra-operative recordings
45

46. Spinal cord injury
Neurological damage during surgery and
anesthesia is not limited to the site of surgery.
Paraplegia and quadriplegia have been
reported as a result of poor pt positioning.
Neurological damage is more likely at or near
the site of surgery on the spine.
46

47. Spinal cord injury Risk factors:
Length and type of surgical procedure
Spinal cord perfusion pressure
Underlying spinal pathology
Pressure on neural tissue during surgery
47

48. Spine surgery: Conditions of Increased Risk
Spinal distraction
Sub laminar wiring
Induced hypotension
Inadvertent cord compression
Certain instrumentation (Luque rods)
Ligation of segmental arteries
48

49. Controlled Hypotensive Anaesthesia
Definition: It is the elective lowering of arterial B.P.
Advantage :
 Minimization of surgical blood loss
 Better wound visualization
Methods :
 Proper positioning
 Positive pressure ventilation
 Administration of hypotensive drugs: sodium
nitropruside B - Blockers Nitroglycerine Propofol
Trimethaphan Inhalational Adenosine (Halothane/
isofluran)
49

50. Controlled Hypotensive Anaesthesia (contd)
Safe level of hypotension :
In healthy young individuals mean arterial
pressure as low as 50 to 60 mm of Hg is
tolerated with out complication.
Chronically hypertensive patients have
altered autoregulation of CBF and reduction of
MAP more than 25% of base line not tolerated.
Patient with H/o transient ischemic attacks
may not tolerate any decline in cerebral
perfusion.
50

51. Controlled Hypotensive Anaesthesia (contd)
Relative contra indication :
Pt having predisposing illnesses that lesson the margin
of safety for adequate organ perfusion
 Severe anaemia
 Hypovolemia,
 Atherosclerotic vascular disease
 Renal and Hepatic insufficiency
 Cerebrovascular disease
 Uncontrolled glaucoma
51

52. Controlled Hypotensive Anaesthesia (contd)
Complication:( more likely in pt with anaemia)
 Cerebral thrombosis
 Hemiplegia
 Acute tubular necrosis
 Massive hepatic necrosis
 Myocardial infarction
 Cardiac arrest
 Blindness from retinal artery thrombosis or
ischemic optic neuropathy
52

53. Monitoring:
Intra arterial blood pressure monitoring
E.C.G. with S.T. segment analysis
Central venous monitoring
Measurement of urinary output
Monitoring of neurologic function (rarely)
53

54. Traumatic Spinal Cord Injury
Acute Traumatic Spinal Cord Injury:
Common site C5-6 and T12-L1
Respiratory Impairment :
 Intercostal muscle paralysis: if lesion at C5
 Vital capacity 25% of normal
 Diaphragmatic paralysis: if lesion above C3( as
phrenic nerve C3-C5)…… artificial ventilation is
mandatory
 Paralysis of intercostal & abdominal muscles ….
Ineffective cough and decrease chest wall compliance,
retention of secretion , v/Q mismatch 54

55. Spinal shock:
 Sympathectomy , hypotension, bradycardia, & hypothermia
 Spinal reflexes ( areflexia
 Motor power ( flaccid paralysis)
Autonomic Dysfunction:
 Loss of thermal regulation …. Hypothermia
 Gastrointestinal dysfunction: risk of aspiration
 Bladder dysfuction
 Sensory and motor Deficit:
 lesion above C7 and T1 cause quadriplegia
 Lesion above L4 cause paraplegia 55

56. Chronic Traumatic Spinal Cord Injury:
Respiratory dysfunction:
 Pulmonary emoli due to DVT
 Pulmonary infection & upper airway obstruction due to inability
to cough
 Dyspnea due to airway hyperactivity
 Some need partial ventilatory support & diaphragmatic pacing
Cardiovascular Dysfunction:
 Reduced blood volume
 Profound postural hypotension
Autonomic Dysfunction
Autonomic Hyperreflexia 56

57. Conclusions
Understand and appreciate the anatomy
and physiology of the spinal cord
Communicate with the surgeons
Explore new techniques but remember to
perfuse and monitor the patient
57

58. 58