Why Quantitative Train-of-Four (TOF) Monitoring Is Essential for Modern Anesthesia Practice

Beyond the Mask Podcast Summary – The Case for Quantitative Neuromuscular Monitoring

This blog is based on a recent episode of the Beyond the Mask podcast, featuring CRNAs Richie Flowers and Lisandro Hernandez. In the episode, they share their firsthand experiences transitioning from traditional qualitative monitoring to electromyography (EMG)-based quantitative TOF monitoring—highlighting the clinical, workflow, and patient safety benefits they’ve seen along the way.

If you’d like to dive deeper into their discussion and earn Class B CE credit, you can listen to the full episode and complete the CE process using the links at the end of this blog.

Residual paralysis remains a concern for anesthesia providers despite decades of progress. Traditional subjective monitoring methods often fail to detect dangerous levels of neuromuscular blockade, putting patients at risk.

Even with sugammadex—and without quantitative monitoring—residual paralysis can still occur in up to 16% of cases. (1-2)

Methods such as head lifts and hand grips are inherently subjective, and even the most experienced clinician can typically detect recovery only at a TOF ratio of about 0.4—leaving a dangerous “blind spot” where patients may appear ready for extubation but have not yet fully recovered.

Quantitative TOF monitoring uses precise EMG data to measure muscle responses to nerve stimulation. The TOF ratio—fourth twitch amplitude divided by the first—objectively indicates recovery level.

Recovery targets

• 0.9 TOF ratio: Minimum recovery threshold
• Avoid reversal agents when TOF ratio is ≥0.9 with spontaneous recovery

Monitoring sites (best to least)

1. Hand (ulnar nerve): Most accurate, correlates with upper airway muscle recovery

2. Foot (tibial nerve): Acceptable alternative if hand is inaccessible

3. Face (facial nerve): Least reliable; often overestimates recovery

In 2023, the American Society of Anesthesiology released updated guidelines for neuromuscular block management. The key points were:

1. Quantitative monitoring over qualitative is now the standard of care.
2. Recovery threshold increased from 0.7 to 0.9 TOF ratio.

Savings

• Reduce unnecessary NMBA dosing and drug waste – avoid overmedication and excess supply costs
• Optimize reversal agent use – guide precise dosing for cost control and safety
• Shorten OR turnover times – make confident, data-backed extubation decisions to improve throughput

Avoided costs

• Fewer post-op complications – including reduced reintubation rates, lower incidence of pneumonia, and shorter hospital stays
• Lower readmissions – from improved recovery and fewer post-operative issues
• Improved efficiency – smoother PACU operations and better overall patient flow

Concerns:

• “Our current methods work fine.” → Data shows traditional methods miss critical residual paralysis.
• It’s another device to manage.” → Modern monitors integrate seamlessly into anesthesia workflows.
• “It’s too expensive.” → Savings from fewer complications and improved efficiency often offset the cost.

Solutions:

• Provide staff training on device use and interpretation
• Identify early adopters to champion adoption
• Track measurable outcomes (PACU stay, complications)

Quantitative TOF monitoring aligns with the move toward precision medicine and evidence-based practice. Providers who embrace it will lead in delivering safer, more efficient patient care.

Taking action

The evidence is clear: quantitative TOF monitoring improves patient safety and reduces complications.

1. Review your current practice and identify gaps.
2. Evaluate quantitative monitors that meet your clinical needs.
3. Provide training to build team confidence.
4. Learn from peers already using the technology effectively.

1. Domenech, G., Kampel, M.A., García Guzzo, M.E. et al. Usefulness of intra-operative neuromuscular blockade monitoring and reversal agents for postoperative residual neuromuscular blockade: a retrospective observational study. BMC Anesthesiol 19, 2019. 
2. Kotake, Y. Reversal with sugammadex in the absence of monitoring did not preclude residual neuromuscular block. Anesth. Analg, 2013.