Anesthesia for Spine Surgery

Sherif Anis, M.D

Ain Shams University

Cairo, Egypt

Lecture Goals

• Overview of modern concepts in understanding of the spinal cord disease

• Review controversies in anesthesia for spine surgery

• Provide strategies for improving patient care

Why spine?

• 29.9 million people reported musculoskeletal impairments. Back/spine was most frequent, representing 51.7%. Impairment is most prevalent in 45-64 year old group.

AAOS, Musculoskeletal Conditions in the U.S., Feb 1992

Changing times

General Indications for Spine Surgery

1. Spinal cord injury

2. Decompresive spine surgery due to • Trauma• Tumor • Degenerative disease (Spondylosis,

spondylolisthesis, • Spinal canal stenosis,Rheumatoid disease)• Structural deformity (Scoloisis)• Prolapsed Disc• Infection, Vascular malformation

Spinal Cord Anatomy

•   Structure•   Blood supply

Normal C-Spine FilmsAADI ≥ 5 mm = Cervical instability

Lateral view

Spinal Cord Injury: Incidence/ Etiology

• 10, 000 new cases/year in US

• Males> females• Causes:

MVA- 40-50%

Falls- 20%

Recreational activities- 7-15%

violence

Cervical Spine Injury• Occurs in 10% of head-injured patients• Suspect when patient is flaccid, has

diaphragmatic breathing, hypotension, bradydysrythmias, LV dysfunction(Acute SCI)

• Minimize head movement during airway management by cervical collar

• In-line stabilization,in-line traction, during laryngoscopy

Criswell JC, et al: Anaesthesia 1994; 49:900-903

Suspected Cervical Spine Injury• Neck pain• Neurologic symptoms, signs• Unconscious• Mechanism of injury• Intoxication• Spondylosis, rhumatoid arthritis, Down

syndrome (Distruction of transverse ligament and odontoid process).

• Significant head injury, facial fractures

Secondary Injury

• Activation of biochemical, enzymatic and microvascular

• Hemorrhagic necrosis, edema, inflammation

• Vascular stasis, decreased spinal cord blood flow, ischemic cell death

Anesthetic management – acute SCI

• Airway evaluation

• Neurologic evaluation

• Pulmonary evaluation

• Cardiac evaluation and resuscitation

Neurologic DeteriorationAssociated with Airway

Management in a Cervical Spine-Injured Patient

Hastings RH, Kelly SD

Anesthesiology vol 78:580, 1993

Details

• Unrecognized C-spine injury

• Pt became quadriplegic after mask ventilation, repeated laryngoscopy and eventually cricothyroidotmy

Hastings, Anesthesiology 1993

Use of the Intubating LMA-Fastrach™ in 254 Patients with

Difficult to Manage Airways

Ferson DZ, Rosenblatt WH, Osborn I, Ovassapian A.

Anesthesiology 2001 vol 95:1175

Patients with Immobilized Cervical Spines

• 70 cases• 67 under general

anesthesia• 2 awake/topicalized• 1 unconscious

• No new neurologic deficits

Ferson et al, Anesthesiology 2001

Cervical spine motion: a fluoroscopic comparison during intubation with

lighted stylet, GlideScope, and Macintosh laryngoscope.

Turkstra et al.

Anesth Analg 2005; 101: 910–5

Tracheal intubation in patients with cervical spine immobilization:

a comparison of the Airwayscope, LMA CTrach, and the

Macintosh laryngoscopes

M. A. Malik, R. Subramaniam, S. Churasia1, C. H. Maharaj, B. H. Hartel

and J. G. Laffey

BJA 2009

Cervical Disc: Airway Strategies

• Talk to patient• H/O extremity

weakness/tingling• Elicited symptoms

with movement• Neutral position is

best

Anesthetic Technique

• Supine induction• Maintenance with any

combination of opioids, muscle relaxants, volatile agents

• Careful prone positioning

• Careful sitting position

Anterior Cervical Approach

On the Incidence, Cause, and Prevention of Recurrent Laryngeal

Nerve Palsies During Anterior Cervical Spine Surgery

Apfelbaum RI, et al: Spine Volume 25(22), 15 November 2000, pp 2906-2912

Laterality Right > Left

LevelsLower Cervical

Level

Multiple Levels More Level Higher Incidence

ETT Pressure Higher Pressure or Failure to Deflate

Factor Leading To Possible Higher Incidence of RLN Injury

Postoperative Complications• Cervical cord and brain stem edema

• Neck and airway edema

• Risk Factors:

• Duration of surgery

• Amount of blood transfusion

• Obesity, airway pressure

• Operations of greater than 4 cervical levels or involving C2

Epstein NE. J Neurosurg 94:185 2001

Thorocolumbar Spine Disease• Anterior or lateral

pathology• Multiple spine segments• Structural Scoliosis,

tumors, traumatic fractures• Preop.

pain/disability/Medications• Potential large

intraoperative blood loss• Anesthetic technique• Postoperative pain

management

Structural Scoliosis

• Idiopathic

• Neuro-muscular (Neuropathic, Myopathic)

• Congenital

• Neurofiromatosis

• Mesenchymal disorders (Marfan Syndrome)

• Trauma

Methods of Reducing Blood Loss and Limiting Homologous

Transfusions

• Proper positioning to reduce intraabdominal pressure

• Surgical hemostasis• Deliberate hemodilution (?)• Preoperative donation of autologous blood• Blood Salvage technique• Deliberate Hypotension

Prone Position

• Restriction of diaphragm – by abdominal contents – and weight of pt

against thorax

• Create restrictive defect

• Increased peak inspiratory pressure (barotrauma)

• Obstruction of Inf Vena Cava– Decreases preload

– Increases perivertebral venous pressure

• (prone may improve oxygenation when abdomen hangs free- chest roll or frame)

Complications of Flexed Prone Position

• Brachial plexus may be stretched

• Ulnar nerve not properly padded

• Eye damage from pressure• Nose pressure• Excessive compression to

inferior vena cava (minimized by padding under inf iliac spine and chest rolls)

Wilson Frame• Maintains flexed

position for spinal surgery

• Horse-shoe head rest• Proper position of the

head and easy inspection of the face & Eyes.

Support Devices – Head & Neck

38

• Surgical pillow/ foam donut, C-shaped face piece, horseshoe head rest, Prone Positioner, Prone View Helmet. C-Shaped Face Piece

Horseshoe Head Rest Mayfield Tongs

• Mayfield tongs: most stable; recommended in cervical disc disease

Prone Positioner

Jackson Table

• Frame based table• Allows abdomen and

chest to hang freely• May allow 180 degree

rotation

Blood loss during spinal surgery

• 15- 25 ml/Kg• Type of procedure (AP fusion Luque rods into the

pelvis), Operation time• Number of Spine segments.• Duchenne myopathy• Cerebral palsy• Post-operative bleeding.• TRALI

Park Anesth Analg 2000;91

• IAP and intraoperative blood loss were less in the wide vs. narrow width of the Wilson frame

• Blood loss per vertebra tended to increase with an increase in IAP in the narrow pad support

Ischemic Optic Neuropathy

• Rare but increasing• Decreased perfusion• Increased venous

pressure• Increased external

pressure• Decreased oxygen

carrying capacity

Williams, et al. Anesth Analg 1995 80:1018

Injuries: Eye

43

• Corneal abrasions

• Orbital edema

• Postoperative visual loss ( POVL)

POVL Registry

44

SPINE 72%

MISC. 10%ORTHO. 4%

VASCULAR 5%

CARDIAC 9%

Distribution of cases from the ASA POVL Registry

• Goal: Identify risk factors associated with POVL

• Retrospective analysis of patients who reported visual loss < 7 days postop

PION 60%AION 20%

Unknow

n

9%

CR

AO

11%

Distribution of 93 ophthalmic lesions associated with POVL after spine surgery

Postoperative Vision Loss- Risk Factors

• Atherosclerotic disease

• Hypotension

• Anemia

• Excessive blood loss

• Long duration of surgery

• Head dependent positioning

Cheng MA Neurosurgery 46:625, 2000

POVL

46

Ischemic Optic Neuropathy (ION)

Central Retinal Artery Occlusion (CRAO)

Etiology Intraop ↓ BPProlonged surgery↑ Blood loss↑ Crystalloid infusion

Direct external pressureEmboli

Mechanism IschemiaOrbital edema → stretch and compression of ON

↓Ocular perfusion pressure

Clinical Features

PainlessBilateral↓Light perception↓ Visual fields

PainlessUnilateralPeriorbital swelling or ecchymosis

Cardiovascular Support

• Maintain SCPP=MAP-CSFP

• Maintain MAP above 70 mmHg

• Fluid management- blood & crystalloid

• “Pressors” if needed

Spine Surgery- Monitoring

• Routine

• Arterial line

• CVP/ PA catheter

• Neurophysiologic

Monitoring the Spinal Cord

• SSEP• MEP• Wake up test• EMG

Indications for SSEP’s

• Spinal instrumentation

• Scoliosis correction• Spinal cord

operations• Aortic surgery

Spine surgery: Times of Increased Risk

• Spinal distraction

• Sublaminar wiring

• Induced hypotension

• Inadvertent cord compression

• Certain instrumentation (Lugue rods)

• Ligation of segmental arteries

High risk patients

• Severe rigid deformity Cobb angle ≥ 120Q

• Congenital scoliosis with intra-spinal anomalies.

• Post infectious

• Pre-existing neurological deficits

Dorsal /Posterior

Ventral /Anterior

MEP

MEP

SSEP

SSEP

“Damage in the territory of the anterior spinal artery might theoretically occur without causing significant impairment of the dorsal sensory tracts, particularly when the spine is approached from the anterior

side.”

May DM, Jones SJ, Crockard HA. Somatosensory evoked potential monitoring in cervical surgery: identification of pre- and intraoperative risk factors associated with neurological deterioration. J Neurosurg 1996;85:566 ﾐ 7

Factors affecting SSEP

• All Anesthetic agents except NMB (Narcotics least effect)

• Hypotension below cerebral autoregulation

• Hypothermia

• Hypoxemia

• Hemodilution and low HCT levels

SSEP

Loss of SSEP & MEP

Caveats for MEP monitoring

• You CAN intubate with non-depolarizing agent (there will be time for it to wear off)

• When closing, administer NMB to allow decrease of hypnotic agents

Wake up Test• 1 or 2 assistants available

• N2O-Narcotic-Relaxant technique, better TIVA

• Rare use of Naloxone 0.3-0.5 µgm/Kg

• No reversal of NMB (3 twitches on TOF)

• Complications: Extubation, Recall, M.I, Dislodgement of instrumentations, Air embolism

Anesthetic Considerations

• Hypotension may occur with acute blood lossDexmedetomidine:• Use peri-operatively• May decrease narcotic use• Hemodynamic stability• Patients comfortable postoperativelyMgSO4: • NMDA antagonistMethyl-prednisolone:• Better in post traumatic patients (6-8 hours)

When would you Extubate??• Post-operative MV with severe restrictive

VC ≤ 30%, High PCo2

• Duchenne Myopathy, Familial dysautonomia, Cerebral palsy

• Criteria for extubation: VC ≥ 10ml/Kg,

Vt ≥ 5 ml/ Kg,

RR ≤ 30

-ve insp. Force ≥ -30cmH2o

Pain management strategies(Positive attitude in Negative Situations)

• IV PCA• Multimodal therapy• Epidural opioids

(catheter placed by surgeon)

• Cooperation with pain service

• Incentive spirometery• Cough & deep

breathing

Conclusions

• Understand and appreciate the anatomy and physiology of the spinal cord

• Communicate with your surgeons

• Explore new techniques but remember to perfuse and monitor the patient

THANK YOU