Related Experiment Video
Updated: Jun 23, 2025
The Evoked Potential Operant Conditioning System EPOCS: A Research Tool and an Emerging Therapy for Chronic Neuromuscular Disorders
Published on: August 25, 2022
Pediatric Intraoperative Electromyographic Responses at the Adductor Pollicis and Flexor Hallucis Brevis Muscles: A
Joseph D Tobias1, Richard H Epstein2, Julie Rice-Weimer3
1From the Department of Anesthesiology & Pain Medicine, Nationwide Children's Hospital, The Ohio University, Columbus, Ohio.
Insights
Quantitative neuromuscular monitoring in pediatric patients shows that while the foot offers an alternative site, it exhibits delayed onset and recovery compared to the hand. This difference is crucial for accurate assessment of neuromuscular block depth and recovery for tracheal extubation.
Area of Science:
- Anesthesiology
- Pediatric Anesthesia
- Neuromuscular Monitoring
Background:
- Train-of-four (TOF) stimulation assesses neuromuscular block depth during surgery.
- Quantitative monitoring in children is challenging due to size and equipment limitations.
- The foot is an alternative monitoring site when the hand is unavailable, but comparative data are scarce.
Purpose of the Study:
- To compare evoked neuromuscular responses between the hand and foot in pediatric patients receiving neuromuscular blocking agents (NMBAs).
- To evaluate the feasibility and implications of using the foot for quantitative neuromuscular monitoring in children.
Main Methods:
- Simultaneous electromyographic (EMG) monitoring was performed at the hand (adductor pollicis) and foot (flexor hallucis brevis) in pediatric surgical patients.
- Patients received NMBAs, and TOF stimulation was used to assess neuromuscular block and recovery.
Main Results:
- Baseline twitch amplitude was higher at the foot, but baseline and maximum TOF ratios (TOFR) were similar between sites.
- Onset of neuromuscular block (T1 decrease) was delayed by ~90 seconds at the foot compared to the hand.
- Recovery of TOFR to ≥0.9 was delayed by ~191 seconds at the foot versus the hand.
Conclusions:
- TOF monitoring is feasible in young children using either the hand or foot.
- Delayed onset and recovery at the foot necessitates careful interpretation of neuromuscular block depth and recovery.
- These delays may influence the timing of tracheal intubation and extubation decisions.
Background:
Peripheral nerve stimulation with a train-of-four (TOF) pattern can be used intraoperatively to evaluate the depth of neuromuscular block and confirm recovery from neuromuscular blocking agents (NMBAs). Quantitative monitoring can be challenging in infants and children due to patient size, equipment technology, and limited access to monitoring sites. Although the adductor pollicis muscle is the preferred site of monitoring, the foot is an alternative when the hands are unavailable. However, there is little information on comparative evoked neuromuscular responses at those 2 sites.
Methods:
Pediatric patients undergoing inpatient surgery requiring NMBA administration were studied after informed consent. Electromyographic (EMG) monitoring was performed simultaneously in each participant at the hand (ulnar nerve, adductor pollicis muscle) and the foot (posterior tibial nerve, flexor hallucis brevis muscle).
Results:
Fifty patients with a mean age of 3.0 ± standard deviation (SD) 2.9 years were studied. The baseline first twitch amplitude (T1) of TOF at the foot (12.46 mV) was 4.47 mV higher than at the hand (P <.0001). The baseline TOF ratio (TOFR) before NMBA administration and the maximum TOFR after antagonism with sugammadex were not different at the 2 sites. The onset time until the T1 decreased to 10% or 5% of the baseline value (T1) was delayed by approximately 90 seconds (both P =.014) at the foot compared with the hand. The TOFR at the foot recovered (TOFR ≥0.9) 191 seconds later than when this threshold was achieved at the hand (P =.017). After antagonism, T1 did not return to its baseline value, a typical finding with EMG monitoring, but the fractional recovery (maximum T1 at recovery divided by the baseline T1) at the hand and foot was not different, 0.81 and 0.77, respectively (P =.68). The final TOFR achieved at recovery was approximately 100% and was not different between the 2 sites.
Conclusions:
Although this study in young children demonstrated the feasibility of TOF monitoring, interpretation of the depth of neuromuscular block needs to consider the delayed onset and the delayed recovery of TOFR at the foot compared to the hand. The delay in achieving these end points when monitoring the foot may impact the timing of tracheal intubation and assessment of adequate recovery of neuromuscular block to allow tracheal extubation (ie, TOFR ≥0.9).
