CORD ISCHEMIA PREVENTION
An anterior approach for an L2 vertebrectomy and L1 - L3 stabilization and fusion was performed on a 40-year-old female. The neurotechnologist used somatosensory evoked potentials to monitor the tibial and ulnar nerves and electromyography to monitor spontaneous activity.

All studies were stable throughout dissection and decompression. Blood pressure was maintained around 110/85, core temperature maintained close to 36.0 degrees C, and anesthesia administered at 50 percent nitrous oxide and 3 percent desflurane with a propofol infusion, a standard anesthetic regimen.

Continued stimulation of the tibial nerve that generated occipital and cortical potentials began showing gradual prolongation in latency that exceeded the allowable limits, greater than 10 percent of baseline studies. Amplitude did not show significant change. Potentials generated with ulnar nerve stimulation, acting as a control, showed no significant deviation from baseline.

The changes in the occipital and cortical potentials were discussed with the surgeon. In review of the electrophysiological findings, the control (potentials generated with ulnar nerve stimulation) remained within normal limits ruling out anesthetic concerns. The occipital and cortical potentials were degraded beyond the upper limits of normal. The neurotechnologist suggested that ischemia can affect the evoked potentials and that the decreased blood flow to the spinal cord was most likely the cause of occipital and cortical potential degradation.

Considering the patient position, left lateral decubitus with the table flexed, a decrease in blood flow to the spinal cord can result due to constriction of the intervertebral foramen. The surgeon suggested increasing the blood pressure. Within four minutes, the occipital and cortical latencies returned to baseline values, thus minimizing the threat of paraplegia due to cord ischemia.

Though the surgery was performed flawlessly, vital functions were stable, and anesthetic concentrations were administered without significant variations, the possibility of a surgical morbidity still existed. This case demonstrates the neurotechnologist’s knowledge in neuroanatomy correlated with his or her knowledge of electrophysiology and the ability to discuss findings on a high level with the surgeon. With the help of a highly trained neurotechnologist and a member of the surgical team, this patient came through surgery with the highest expectations of a full recovery.

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