Anesthesia for spine surgery By Dr. Ahmed Mostafa.

Anesthesia for spine surgery

ByDr. Ahmed

Mostafa

Spinal Cord Disorders

• Trauma.• Tumors. • Congenital and degenerative diseases of

the spinal cord and vertebral column.• Intervertebral disc diseases.

Acute Traumatic Spinal Cord Injury

• Cervical spine injury occurs in 1.5% to 3.0% of all major trauma victims.

• Injury to the cervical spine occurs in 2% of patients with head injury who survive to reach the hospital.

• Trauma can injure both the thoracic and lumbar spinal cord segments.


Acute spinal cord transection initially produces:

- Flaccid paralysis.

- Absence of sensation below the level of injury.

- The most severe physiologic derangements occurring with injury to the cervical cord and lesser perturbations occurring with more caudal cord injuries.



- There is loss of temperature regulation.

- Loss of spinal cord reflexes below the level of the injury.

- Hemodynamic instability (spinal shock):

are influenced by:



Loss of sympathetic nervous system activity and diminution of systemic vascular resistance.

Bradycardia due to loss of the T1-T4 sympathetic innervation to the heart.

Hypotension can also occur with thoracic and lumbar injuries, but less severe than with cervical injuries.



- With cervical and upper thoracic cord injury, the major cause of morbidity and mortality is alveolar hypoventilation combined with an inability to clear bronchial secretions.

- Aspiration of gastric contents and pneumonia and pulmonary embolism are constant threats during spinal shock.



• Treatment of a cervical fracture dislocation:

Immediate immobilization.

Hard neck collars.

Immobilization and traction as provided by halo-thoracic devices are most effective in preventing cervical spine movement.



• Treatment of a cervical fracture dislocation:

Manual in-line stabilization: Is recommended to help minimize cervical spine

movement during

tracheal intubation.



• Anesthetic management: (Airway)

Minimize neck movements during laryngoscopy.

Topical anesthesia and awake fiberoptic laryngoscopy are an alternative to direct laryngoscopy.

Rapid-sequence induction of anesthesia.

Awake tracheostomy



• Anesthetic management: (Hemodynamic instability)

Patients are vulnerable to dramatic decreases in systemic blood pressure following:

Acute changes in body posture.

Blood loss.

Positive airway pressure.



• Anesthetic management: (Hemodynamic instability)

To minimize these effects:

Liberal intravenous infusion of crystalloid solutions may be necessary to replete intravascular volume, which has been abruptly compromised by vasodilation.

Acute blood loss should be replaced promptly.



- Anesthetic management:

Breathing is best managed by mechanical ventilation, as abdominal and intercostal muscle weakness or paralysis, exacerbated by general anesthesia, increases the chances of respiratory failure with ensuing hypoxia and hypercapnia.




Anesthetic maintenance is targeted at ensuring physiologic stability and facilitating tolerance of the tracheal tube. Volatile or injected anesthetics are satisfactory for this purpose.

Nitrous oxide should be used with caution.




Muscle relaxant use should be determined by the operative site and the level of spinal cord transection. If muscle relaxants are necessary, the sympathomimetic effects of pancuronium makes this drug an attractive choice; however, other non-depolarizing muscle relaxants can be used safely.



• Anesthetic management:

Succinylcholine is unlikely to provoke excessive release of potassium during the first few hours after spinal cord transection. Even in these instances, the benefits of succinylcholine, which include rapid onset of action and short duration of relaxation, should be weighed against potential side effects.



Anesthetic management: (Monitoring)

Arterial hypoxemia is common following spinal cord injury, emphasizing the need for continuous pulse oximetry and delivery of supplemental oxygen.

ECG abnormalities are common during the acute phase of spinal cord injury.



Anesthetic management: (Monitoring)

Body temperature should be monitored and manipulated as patients tend to become hypothermic below the spinal cord transection.

Chronic spinal cord injuries

• Autonomic hyperreflexia:

It is initiated by:

Cutaneous or visceral stimulation below the level.

Distention of a hollow viscus (bladder & rectum).

Surgery are common stimuli.



Cutaneous vasodilation occurs above the level transection.

Nasal stuffiness.

Headache and blurred vision.



Cerebral, retinal, or subarachnoid hemorrhages as well as increased operative blood loss.

Loss of consciousness , seizures, cardiac arrhythmias, pulmonary edema reflects acute left ventricular failure.



approximately 85% of patients with spinal cord transections above T6 exhibit this reflex, yet it is unlikely to be associated with spinal cord transections below T10.



Management:Prevention of the development of autonomic

hyperreflexia.General, neuraxial, or regional anesthesia

should be instituted. Vasodilator drugs.

Spinal cord tumors

Divided into two broad categories:

Intra-medullary tumors are located within the spinal cord proper and account for approximately 10% of tumors affecting the spinal column.

Extra-medullary tumors can be either:

o Intradural: Neurofibromas and meningiomas account for most of the intradural tumors.

o Extradural: metastatic lesions.

Spinal cord tumors

Anesthetic management:

- Ensuring adequate spinal cord oxygenation and perfusion. This is achieved by ensuring adequate PaO2 and by avoiding hypotension and anemia.

- Specifics of management will depend on the level of the lesion and the extent of neurologic impairment.

Spinal cord tumors

Anesthetic management:

- Safe resection of a tumor may require the use of intraoperative electrophysiologic monitoring of neurologic function. Techniques such as electromyography, somatosensory evoked potentials, and motor evoked potential monitoring have a variety of anesthetic implications.

Congenital and degenerative diseases of the spinal cord and vertebral column

Spina bifida occulta

- It is a congenital defect that is present in an estimated 20% of individuals. Given that it usually produces no symptoms.

- It is often discovered as an incidental finding on radiographic examination during evaluation of some other unrelated disease process.



Because there are usually no underlying abnormalities, an increased risk with spinal anesthesia is not expected, and large numbers of these patients have received spinal anesthesia safely. However, a variant of spina bifida occulta known as occult spinal dysraphism exists in which the bony defect may involve more than one lamina.



These defects are associated with a tethered spinal cord (cord ending below the L2-L3), which may be responsible for progressive neurologic symptoms. Up to 50% of individuals with a tethered spinal cord have cutaneous manifestations overlying the anomaly, including tufts of hair, hyperpigmented areas, cutaneous lipomas, and skin dimples.


Spondylosis

- It is a common non-congenital disorder that leads to osteophyte formation and degenerative disc disease.

- There is narrowing of the spinal canal and compression of the spinal cord and/or nerve root.


Spondylosis

- Spinal cord dysfunction may also reflect ischemic infarction secondary to bony compression of the spinal arteries.

- Symptoms typically develop insidiously after approximately the age of 50.

- Surgery may be necessary to arrest progression of the symptoms, especially motor loss.


Scoliosis, kyphosis and kyphoscoliosis

- Kyphosis is an exaggerated anterior flexion of the spine, as seen in ankylosing spondylitis.

- Scoliosis is defined as a lateral rotation of the spine greater than 10 degrees accompanied by vertebral rotation.

- Scoliosis is classified as idiopathic, congenital, or neuromuscular



- Thoracic scoliosis results in a narrowed chest cavity producing a decrease in chest wall compliance and restrictive lung disease.

- Cobb angles of greater than 65 degrees usually cause significant decreases in lung volumes.


Scoliosis, kyphosis and kyphoscoliosisX-ray of a patient with scoliosis. Cobbangle is an angle formed by a line drawn perpendicular to the top of the superior vertebrae of the scoliotic curve and a similar perpendicular line drawn along the bottom of the inferior vertebrae. The Cobb angle in this patient is 62 degrees.



- Thoracic scoliosis results in a narrowed chest cavity producing a decrease in chest wall compliance and restrictive lung disease.

- Cobb angles of greater than 65 degrees usually cause significant decreases in lung volumes.



- Exercise tolerance and pulmonary function studies should be obtained before surgery.

- This information guides decisions regarding the extent of surgery permitted at one time and the requirement for postoperative ventilatory support.



- A vital capacity of less than 40% of the normal range is predictive of the requirement for postoperative ventilation.

- The major abnormality in arterial blood gases is hypoxemia, secondary to ventilation-perfusion inequalities caused by alveolar hypoventilation.



- Chronic hypoxemia produces elevated pulmonary vascular resistance, which ultimately leads to cor-pulmonale.

- An echocardiogram should be assessed for pulmonary hypertension and right ventricular hypertrophy.



- In patients with pulmonary hypertension, ECG may reveal evidence of right ventricular hypertrophy and right atrial enlargement.

- Surgical corrections involving high anterior thoracic levels or video-assisted thoracoscopic surgery require one-lung ventilation.



- In patients with restrictive lung disease, adequate oxygenation may be difficult during one-lung ventilation and may require continuous positive airway pressure to the non-ventilated lung and positive end-expiratory pressure to the ventilated lung.



- Surgery associated with large blood losses.

- A postoperative neurologic deficit is one of the most feared complications. To reduce this complication, waking the patient up during surgery to determine the functional integrity of the spinal cord.



Disadvantages:- limited to gross motor movements. - Influenced by anesthetics.- Inadvertent extubation. - Air embolism during a deep inspiration, and

dislodgment of the instrumentation during violent movements.



Monitoring:- Somatosensory evoked potential (SSEP)- Motor evoked potential (MEP).- Electromyogram monitoring.

Thank you

Dr. Ahmed Mostafa

Anesthesia for spine surgery By Dr. Ahmed Mostafa.

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