Laminectomy

Procedure for decompressing the neural elements of the lumbar spine via a posterior approach.

It can be used to treat lumbar radiculopathy secondary to degenerative disease caused by herniated discs or osteophytes (a type of bone spur or bony projection that forms along joints).

Compression of cauda equina is usually due to degenerative disease, congenital stenosis, neoplasm, and/or trauma.

Access to treat intradural tumors, AVMs, and other spinal cord lesions.

Meninges

Dura mater

It has an outer periosteal layer adherent to the inner cranium, and an inner meningeal layer forms a fold, the falx cerebri, which separates the cerebral hemispheres and the tentorium cerebelli, which separates the occipital lobe and the cerebellum.

Innervated by the first three cervical roots and the trigeminal nerve

• During awake craniotomy pt may complain of pain "behind the eye" when traction is applied to the dura

Arachnoid mater

Thin, avascular membrane

Pia mater

Thin avascular membrane adherent to the brain and spinal cord.

Cerebrospinal fluid

150 mL replaced every 3-4 hrs, drains into the venous blood via the superior sagittal sinus and is absorbed by arachnoid granulations.

Normal ICP 5-15 mmHg

Position

Prone for the posterior approach

In general, this patient category may be difficult to position due to their spine issues. They will have to individualize and improvise to provide the best possible support and avoid pressure point issues. Positioning may require more time.

Prone Position

Preop assessment of head, neck, shoulder, and arm mobility

Heart ok as long as avoiding occlusive pressure on the inferior Vena Cava and femoral veins

Increased SVR, and PVR leading to decreased SV/CO/CI

Abdominal pressure may impede venous return due to compression of the inferior vena cava and aorta and increase surgical bleeding during spine surgery due to engorgement of epidural veins

Increased Zone 3 a > v > A

Decreased total lung capacity, and decreased compliance leading to increased work of breathing

Increased PIP to achieve adequate ventilation (abdomen pushes up). Monitor for barotrauma. Pressure control ventilation may be a good option

CNS damage is high risk - keep the neck in a neutral position

If head below heart level = blood/cerebrospinal fluid accumulates (remember no valves, gravitational flow) = increased ICP, decreased CPP

Risk for post-op blindness - lubricate, pad eyes with op-site, gauze, and shield. Check eyes every 15 minutes during the case to ensure no pressure

Jaffe: LR max of 40ml/kg for total surgery to possibly minimize postop blindness from ischemic optic neuropathy; if additional fluid is needed, give hetastarch 6% up to 20 mL/kg, albumin 5% or blood

Pressure points to be padded

• Torso typically supported on a frame or with rolls from shoulder to iliac crest/crosswise at pelvis and shoulders
• Lower legs supported with pillows
• UE either tucked or on arm boards with arms flexed at shoulder and elbow (know preop issues with joint mobility)
• Pad pressure points at elbows, knees, ankles, and genitalia
  • Ensure limited pressure on nipples

Anesthetic considerations

Neurologic

Pts may present with motor weakness, sensory deficits, or bowel/bladder dysfunction. Make sure you document any issues. They may have had a preop MRI.

Hematologic

Substantial risk of blood loss. Pts need to have T&C done, with a minimum of two units of RPBCs available. Consider using a cell saver. Pts may have been on anticoagulants, which increases the risk of bleeding.

Laboratory

Baseline BMP and H&H

Preop

May have a higher degree of pain than other patient categories; may have had previous back surgeries. They may not have gotten their regular pain medication due to surgery. May have anxiety due to previous surgeries

Medicate with versed and possibly a small dose of sufentanil

Placement of A-line in preop holding or in OR after induction along with placement of CVP line

Possible use of Jackson table.

Monitors

Pulse ox, ECG, NIBP, Temp, Bair hugger, PNS, A-line, possible CVP, 2 large bore IVs, Foley Cath

Intraoperative

Induction

Preoxygenation

Consider pretreatment with Rocuronium 3-5 mg IV

Lidocaine 1 mg/kg/IV

Propofol 1-2 mg/kg/IV - if cardiac disease, consider etomidate 0.1-0.4 mg/kg/IV

Sufentanil 5-10 mcg/IV

Succinylcholine 0.5-1.5 mg/kg/IV

ETT

If a thoracic approach may need DLT (double lumen tube) to facilitate one-lung ventilation

Maintenance

If using evoked potentials: consider TIVA - propofol 75-200 mcg/kg/min and remifentanil (0.1-0.5 mcg/kg/min) - May see bradycardia (esp. with vecuronium), chest rigidity, respiratory depression, and decreased sympathetic tone: onset 30 sec, peak 3-5 min, duration of action 5-10 min (esterase elimination). Make sure to start post-op pain management toward the end of the case

If no evoked potentials - volatile agent, eg, isoflurane, vecuronium (0.025 mg/kg) or pancuronium (0.02 mg/kg), sufentanil

Monitor K⁺, hct if excessive bleeding. ABGs as needed

Emergence

Supine position

Evaluate facial and airway edema - consider length of surgery - may need overnight intubation

Zofran 4 mg/IV

Decadron 4-6 mg/IV

Document neurological status if possible, before reaching the PACU

Complications

Hypotension - abdominal compression, decreased venous return, or vascular injury

Nerve root injury

Blindness

Bowel or ureteral injury

Electrophysiologic monitoring

It depends on the location of the tumor

Note 50% decrease in amplitude or a 10% increase in latency are considered significant

Always communicate with the technician to ensure adequate impulses

Continuous drips as opposed to boluses