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SpecialtyCare recently published research that evaluates the impact of inhalational anesthetic agents on the baseline monitorability of motor evoked potentials (MEPs) during spine surgery.
The Research
Motor evoked potentials (MEPs) are typically used to monitor spinal cord and spinal nerve root or plexus function during spine surgery. Reports are currently evaluating the impact of anesthesia on MEPs ability to monitor spinal cord function. Still, more research is needed to assess its ability to monitor spinal nerve root and plexus function.
This study aims to compare the baseline monitorability and amplitude of MEPs during cervical and lumbar procedures. This is based on a maintenance anesthetic regimen that includes total intravenous anesthesia (TIVA) versus a balanced regimen with volatile inhalational and intravenous agents.
Baseline MEP data was pulled from 16,559 cervical and 6,196 lumbar extradural spine procedures for adults 18 and older, utilizing multimodality intraoperative neuromonitoring (IONM), including MEPs during January 2017 and March 2020.
Results of the Study
Cervical Procedures
Of the 16,559 cervical procedures, 13,112 were in the TIVA cohort, and 3,447 were in the Balanced cohort. Results showed that:
- Baseline MEPs from all upper extremity muscles were monitorable in 86.8% of cases in the TIVA cohort
- 59.3% of cases in the Balanced cohort were monitorable
- The model-adjusted difference in monitorability for intrinsic hand and foot muscles was 1.1%
- The disparity in monitorability for the proximal upper extremity muscles proves that the TIVA cohort has significantly greater monitorability than the Balanced cohort in cervical procedures
Lumbar Procedures
Of the 6,196 lumbar procedures, 5,440 were in the TIVA cohort 756 in the Balanced cohort. Results showed that:
- Baseline MEPs from all lower extremity muscles were monitorable in 83% of procedures in the TIVA cohort
- 61% of procedures in the Balanced cohort were monitorable
- The model-adjusted difference in monitorability for the intrinsic hand MEPs was 0.2% and 0.4% for intrinsic foot MEPs
- The disparity in monitorability for the proximal muscles proves that the TIVA cohort has significantly greater monitorability than the Balanced cohort in lumbar procedures
Conclusion
Baseline MEPs from proximal muscles can’t be reliably obtained because inhalational agents are negatively impacted, significantly limiting the ability to diagnose evolving nerve root or plexus dysfunction during spine surgery. IONM’s effectiveness in facilitating safer surgery is further enhanced by using a TIVA regimen whenever possible. Results showed that:
- Compared to TIVA, a balanced IV and inhalational regimen significantly decreases the monitorability and amplitude of all muscle MEPs leading to increased false negatives and decreased sensitivity when gas is used
- This effect is more pronounced on proximal muscle MEPs, such as the deltoid and biceps in the upper extremities or quadriceps and tibialis anterior in the lower extremities
- TIVA is ideal for monitoring motor function with MEPs and critical for monitoring nerve root function
- TIVA is the preferred anesthetic regimen for optimizing MEP monitoring during spine surgery
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