JMIR Publications

ABSTRACT

Background:

Local anesthetics are widely used in clinical practice, but their administration carries the risk of local anesthetic systemic toxicity, a potentially fatal complication. Calculating maximum safe doses is complex and error-prone when considering multiple patient-specific factors. While existing tools and mobile apps have been developed to assist practitioners, most have not been scientifically validated and may propose unsafe doses. The LoAD Calc mobile app was developed at the Geneva University Hospitals to calculate maximum safe doses by integrating comprehensive patient parameters.

Objective:

The primary objective was to evaluate the overdose rate with the LoAD Calc app in comparison with traditional calculation method. Secondary objectives included assessing calculation time, user confidence, app usability, and inter-practitioner variability.

Methods:

This single center randomized controlled trial included 50 anesthesiologists randomized to use either LoAD Calc or their usual calculation methods. Participants completed 10 clinical vignettes requiring maximum safe dose calculations for lidocaine, levobupivacaine, and ropivacaine. Vignettes included various patient characteristics, comorbidities, and medication interactions requiring dose adjustments. For the primary outcome, maximum safe doses were determined using the most comprehensive, and thus conservative, set of calculation rules incorporating all patient-specific factors (primary outcome). Two simplified methods, based solely on actual weight or ideal body weight, were among the secondary outcomes, which also included underdose rates (defined as the maximum acceptable volume minus 20%), time to dose calculation, confidence in the method used, and, for the LoAD Calc group, assessment of the System Usability Scale. Overdose rates were compared using chi-squared tests, while calculation time and confidence levels were assessed using Student's t-test.

Results:

All 50 participants completed the study. Using the full set of calculation rules, the overdose rate was significantly lower when LoAD Calc was used (12.0% [30/250] vs 79.2% [198/250]; P<.001). This difference was consistent across all 3 local anesthetics: ropivacaine (5.0% vs 64.0%; P<.001), levobupivacaine (37.0% vs 90.0%; P<.001), and lidocaine (12.0% vs 88.0%; P<.001). When considering simplified weight-based methods, overdose rates remained significantly lower when LoAD Calc was used (actual weight: 3.2% vs 38.0%, P<.001; ideal body weight: 4.0% vs 60.4%, P<.001). Underdose rates were similar (10.0% vs 10.8%; P=.77). Calculation time did not differ (111±56 vs 115±89 seconds; P=.53). LoAD Calc users reported higher confidence (8.5±0.9 vs 6.3±1.7; P<.001) and the app achieved a median System Usability Scale score of 98 (95:100).

Conclusions:

Local anesthetic overdoses were significantly less likely when the LoAD Calc mobile app was used. There was no increase in calculation time or underdosing risk in comparison with standard calculation methods. Given its usability score and the improvement in practitioner confidence, implementation in clinical practice could be considered and may improve patient safety by reducing local anesthetic systemic toxicity risk while promoting dose calculation standardization. Clinical Trial: IRRID: PRR1-10.2196/53679