A Randomized Controlled Crossover Study Comparing Sugammadex and Placebo

Intraoperative monitoring of the motor evoked potentials has been shown to be both a sensitive and specific indicator for detecting intraoperative neurological injuries during spine surgery.(Fehlings, Brodke et al. 2010) It is utilized whenever there is risk for injury of nerve roots or the spinal cord during the procedure.

Anesthetic agents, especially the inhaled volatile anesthetics and muscle relaxants, are con-founders for motor evoked potential monitoring as they have deleterious effects on the amplitude of motor evoked potentials.(Sekimoto, Nishikawa et al. 2006) Hence, total intravenous anesthesia with no intraoperative muscle relaxants, are the standard anesthetic technique for these surgeries.

Muscle relaxants are usually required during the induction of anesthesia and endotracheal intubation of larynx. Current practice is to wait for the resolution of residual neuromuscular blockade before the motor evoked potential recordings (MEP) are initiated and this makes it difficult to assess if there was any neurological injury associated with positioning of the patient. A previous case series has shown that reversal of muscle relaxant can improve the amplitude of MEPs.(Batistaki, Papadopoulos et al. 2012) The aim of this study is to perform a randomized controlled trial to study the changes in motor evoked potential amplitudes comparing sugammadex and placebo.

Motor evoked potential monitoring is a well-established and safe intervention to assist in prevention of intraoperative injury during spine surgery.(Schwartz, Sestokas et al. 2011) Patients with cervical myelopathy often present with neurological deficits and recording of the motor evoked potentials are often challenging in these patients. In addition, anesthetic agents especially muscle relaxants can abolish the motor response making it difficult to know when the baseline MEP can be recorded.

The usual anesthetic practice for patients undergoing posterior cervical spine surgery is to administer muscle relaxation to aid intubation at the start of the case . The neuromuscular blockade is then allowed to wear off and the neurophysiologist will attempt to record their baseline motor evoked potentials during or just prior to surgical exposure.

The issues with this current technique are;

1. Patients cannot be monitored for neurological changes during their transfer into the prone position
2. There is likely residual neuromuscular blockade decreasing the amplitude of motor evoked potentials.

Investigators plan to perform a randomized controlled cross-over trial comparing the change in MEP amplitudes with administration of sugammadex or placebo. This will be performed on at risk patients (e.g. cervical myelopathy) undergoing posterior cervical spine surgery where MEPs can be more difficult to attain but of higher utility.

The purpose of this study is to determine if reversal of residual neuromuscular blockade with Sugammadex can increase the amplitude of the motor evoked potentials.

Eligibility Criteria:
Inclusion Criteria:

* All adult patients aged 18-80 years with American Society of Anesthesiologist (ASA) classification I-III undergoing cervical spine surgery in the prone position with intraoperative motor evoked potential monitoring.
* Operation time greater than 3 hours

Exclusion Criteria:

* Allergy to propofol or documented egg allergy
* Known allergy to sugammadex
* Severe renal dysfunction (EGFR\<30)
* British Research Medical Council (BRMC) motor grading \<3 in any peripheral muscle group preoperatively. This is inability to move the muscle group against gravity.
* Surgical requirement of strict muscle relaxation for surgical exposure
* Lack of informed consent
* Pregnancy
* Loss of MEP signals during washout period (or intraoperative spinal cord injury resulting in irreversible loss of MEP)