ANESTHETIC CONSIDERATIONS IN SPINAL SURGERIES

DEFINITION OF SPINAL SURGERIES Surgeries on spinal column from atlanto

occipital joint to the coccyx. Can be divided in to four categories:

1. Decompression of the spinal cord and nerves.

2. Stabilization and correction of the spinal deformity.

3. Excision of the spinal tumour.

4. Trauma .

ANESTHETIC TECHNIQUE

It depends on the 1. Indication of the surgery.2. Level of spine for surgery.3. Degree of urgency. Whether the surgery is elective as in case of

disc herniation or spinal stenosis. Urgent as in metastatic disease with

neurological deficit. Acute emergency as in fractures and

fracture dislocation.

GENERAL PRINCIPLES

Spinal surgeries can be performed at all ages.

Most procedures are done in prone position although anterior and lateral approaches can also be used.

Secure the airway prior to the surgeries with non kinking ET tube.

Excessive abdominal and thoracic pressure may lead to compromise ventilation and circulation.

CONTD…..

Secure venous access is vital. Moderate hypotension may help to reduce

intraoperative bleeding. Effective analgesia is required mainly in case

of thoracic spinal surgeries as post op respiratory function will be compromised if analgesia is inadequate.

LUMBAR SPINAL SURGERIES

Indications :

1. Herniated nucleus pulposus.

2. Spinal canal stenosis.

3. Spondylolisthesis.

APPROACH

Posterior approach is most commonly used Position :

1. Prone position is most commonly used.

2. Lateral decubitus position is also used.

3. Knee chest position is used in morbidly obese patients.

SYMPTOMS

Severe backache radiated to the hips and legs due to impingement or compression of the nerve root.

Diagnosis can be done by CT scan, MRI scan or myelography.

INTERVERTEBRAL DISC HERNIATION 90% of the disc herniation occur at l5 – S1 or

l4 – l5 levels.

Disc herniates mainly postero laterally and compresses the adjacent nerve root producing pain that radiates along the dermatome.

MRI will show lateral herniated disc compressing on the nerve root.

SPINAL STENOSIS

MRI findings will show that the spinal contents are passing through an area of constriction.

SPONDYLOLISTHESIS

This is the congenital defect in the ossification of the spine in which the body, pedicle and superior facet joint of the vertebra slides anteriorly leaving posterior elements behind.

Most common : L5 sliding over S1.

Diagnosis done by X –rays and confirmed by MRI which shows altered path of cauda equina contents.

ANESTHESIA TECHNIQUES

General anesthesia most commonly used. Regional anesthesia can also be used. General anesthesia is preferred over

regional anesthesia in

1. Metastatic disease of spine.

2. Severe osteoporosis.

3. Infection at the site of dural puncture.

4. High risk to the patient.

COMPLICATIONS OF GA

This is mainly because of prone position.

1. Eye injuries .

2. Necrosis of the nasal cartilage, ear and chin.

3. Increased chances of surgical site bleeding.

4. Hypotension is common.

5. Chances of accidental extubation and tracheo bronchial intubation are more common.

6. venous air embolism.

REGIONAL ANESTHESIA

Advantages over GA: It avoids the complication of GA in prone

position.

1. No increase in surgical site bleeding.

2. No risk of accidental extubation and

3. Decreased incidence of post operative deep vein thrombosis.

4. It offers acute pain relief and assist in early patient mobilization.

CONTD…..

Disadvantages :

1. Patient have to tolerate being awake in prone position.

2. If the patient is restless then movement at the operative site can disturb the surgeon.

THORACIC SPINE SURGERY

Surgery in this region is greatly influenced by the rib cage.

Thoracic spines undergoes less degenerative changes less irritation of the spinal cord and nerve roots because rib cage provides greater mechanical stability.

Indications :

1. Malignancy of the spine, meninges or cord

2. Infections

APPROACH

Anterior approach: This requires thoracotomy and mobilization of

lung to reach Para vertebral areas, sometimes endo bronchial intubation and one lung ventilation are also required to reach upper thoracic spine.

ANESTHETIC TECHNIQUE

Mostly GA is preferred Anesthetic technique depends on potential for

hypoxemia, possibility of massive blood loss and need to verify spinal cord integrity intraopertively.

HYPOXEMIA

The potential for hypoxemia or one lung ventilation mandates routine arterial catheter placement for continuous determination of BP and for taking ABG samples.

This possibility emphasize increase delivering concentration of oxygen to maintain acceptable oxygenation as evidenced by pulse oximetry.

This limit the use of nitrous oxide intraoperatively as it might have to be turned off rapidly in case of difficult oxygenation so i.v anesthetic agent like BZD, propofol or potent inhalational agents are used.

SPINAL CORD INTEGRITY

Somato sensory evoked potentials are used to determine whether surgery has compromised the spinal cord or its blood supply or not.

RECOVERY

Pain relief is a part of anesthetic plan In case where extubation is planned most

common approach is opiod administration prior to extubation.

NSAIDS can also augments post op analgesia.

Regional anesthetic technique like thoracic epidural catheter, intercostal block can also be used.

CERVICAL SPINE SURGERIES

Objectives:

1. To decompress the lesion and

2. Stabilize the cord by internal fixation and bone fusion.

Indications:

1. Degenerative like osteoarthritis or IVD herniation.

2. Rh arthritis.

3. Trauma

4. malignancy

APPROACH

ANTERIOR AND POSTERIOR:Anterior approach is done when spine is stable. Aim of the surgery is decompression and

fusion anterolaterally.Posterior approach Mainly done for unstable cervical spine

ANESTHETIC TECHNIQUE

OBJECTIVE :

1. To secure the airway with out causing neurological injury and to minimize the neck movements during this procedure.

2. It can be done by two ways: Intubation under GA Awake intubation with topical anesthesia

INTUBATION UNDER GA

In this maneuvers are taken to stabilize the head during direct laryngoscopy to avoid hyperextension of the neck.

Advantages :

1. Deep anesthesia and NMB minimize risk of coughing and bucking during instrumentation which can cause movement of spine and risk to cord.

CONTD….

Disadvantages:

1. Can be performed only with patient head in neutral position and

2. May be difficult in case of difficult airway.

CONTD….

AWAKE INTUBATION: Can be done from nasal or oral route with or

with out fibreoptic bronchoscope.Advantages: It provides easiest direct route for

visualization of larynx.Disadvantages : Requires topical anesthesia and

vasoconstriction of nasopharynx . Failure to achieve this can cause epistaxis.

TOPICALIZATION OF AIRWAY

Involves paralysis of lingual nerve, glossopharyngeal nerve, superior and recurrent laryngeal nerve.

They can be blocked by gargling with topical lignocaine or by direct spray.

Anesthesia and vasoconstriction of nasal mucosa can be achieved by topical cocaine or mixture of lignocaine and phenylephrine.

RECOVERY

Put the patient to supine position from prone position and wait for few minutes because emergence with coughing and bucking esp. during shift from prone to supine may put cord at risk.

PAIN RELIEF

Small titrated incremental doses of short acting analgesics like fentanyl can be given prior to emergence.

REFERENCES:

Orthopedic anesthesia . Oxford hand book of anesthesia. Miller anesthesia.