(From the January 2015 Issue of PediatricsOnline)
Neurophysiological monitoring during spinal surgery allows surgeons and anesthetists to determine whether any potential damage has occurred to spinal cord function. Now, data indicates that, for adolescent patients with idiopathic scoliosis requiring posterior spinal fusion, a volatile agent-based anesthetic regimen is a viable alternative to total intravenous anesthesia for neurophysiological monitoring. The alternate anesthesia allows for faster awakening and administration of a rapid wake-up test, according to a prospective study conducted at Nationwide Children’s Hospital.
Posterior spinal fusion is a surgical procedure to correct significant spinal deformity in patients with scoliosis. It requires general anesthesia and may, very rarely, cause damage to nerves controlling sensation or movement in the legs, bowel or bladder. Patients are monitored during surgery via somatosensory-evoked potentials and motor-evoked potentials, which allows the anesthetist and surgeon to test whether a spinal cord injury may have occurred. Until now, no prospective trials had been conducted comparing intravenous anesthesia with a volatile agent-based technique for its effects on the ease of neurophysiological monitoring.
“We wanted to determine whether a volatile agent-based anesthetic would give us an equally effective, alternative method for monitoring nerve function during this risky surgery, since total intravenous anesthesia carries its own additional risks,” says Allan C. Beebe, MD, an orthopedic surgeon at Nationwide Children’s involved with the study.
The pain management and orthopedics teams at Nationwide Children’s collaborated to conduct a randomized trial including 30 adolescent idiopathic scoliosis patients undergoing posterior spinal fusion. Patients received either the volatile agent-based technique with desflurane-remifentanil or the standard, total intravenous technique with propofol-remifentanil. Age, weight, height, body mass index, Cobb angle and distribution of Lenke classifications were comparable between the two groups, as were surgery characteristics such as anesthesia time, surgery duration, intraoperative fluids and blood loss.
“In the volatile anesthesia group, patients had shorter recovery times,” Dr. Beebe says. “Time to eye opening, following commands and tracheal extubation were shorter in the volatile group, and there were no differences in the amplitude or latency of somatosensory-evoked potential monitoring. ”
Greater voltage was needed to generate a motor-evoked potential among the volatile agent-based group, but the voltage remained within a clinically acceptable range.
“Clinically, it appears that the volatile agent is a safe and effective option that also allows improved ability to awaken and test patients during such a risky procedure, should it become necessary.” Dr. Beebe says. “Because of these positive results, we believe the volatile anesthesia option is a beneficial technique for monitoring nerve integrity during these operations.”
The use of volatile agent-based anesthesia for posterior spinal fusion is now a preferred method at Nationwide Children’s. The pain management and orthopedic teams are currently studying alternative pain management techniques utilizing intraoperative methadone, as well as white blood cell function in patients undergoing posterior spinal fusion.
Martin DP, Bhalla T, Thung A, Rice J, Beebe A, Samora W, Klamar J, Tobias JD. A preliminary study of volatile agents or total intravenous anesthesia for neurophysiological monitoring during posterior spinal fusion in adolescents with idiopathic scoliosis. Spine. 2014 Oct 15, 39(22):E1318-24.