Comparison of Acceleromyography and Electromyography in Obese Patients Undergoing General Anesthesia With Rocuronium: A Prospective Observational Study
Conditions: Obesity
Sponsor: University of Padova

Version 1.0 – Approved June 2025 
 
 
 
 
Study Title: OBAEG Study –Acceleromyography versus 
Electromyography in Obesity 
Official Title: Comparison between acceleromyography (AMG) and 
electromyography (EMG) in patients with obesity 
Document Type: Study Protocol and Statistical Analysis Plan 
Version: v1.0 – August 2025 
Document Date: October 2025 
NCT Number: Pending assignment 
 

Version 1.0 – Approved June 2025 
 
Study Protocol and Statistical Analysis Plan (Combined) 
 
Official Title: Comparison of Acceleromyography and Electromyography in Obese Patients Undergoing 
General Anesthesia With Rocuronium: A Prospective Observational Study Organization's Unique  
Acronym: OBAEG  
Protocol ID: AOP3692_CET 
Secondary ID: 6296/EST/25 (Territorial Ethics Committee – Central-East Veneto Area) 
 
 
This is the English translated version, faithfully aligned with the version registered and approved by the 
Ethics Committee. The original Italian version can be provided upon request. 
 
Table of Contents  
Part A – Study Protocol Synopsis 
Part B – Statistical Analysis Plan (SAP) 
 
 

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Part A – Study Protocol Synopsis 
 
Introduction 
Obesity is defined using the Body Mass Index (BMI), calculated as weight in kilograms divided by height 
in meters squared (kg/m²). Severity is classified as follows: Normal weight (BMI 20–24), Overweight 
(25–29), Obesity Class I (30–34), Class II (35–39), and Class III (>40). Obesity is a global public health 
problem due to its association with increased morbidity and mortality. Metabolic bariatric surgery is 
the most effective long-term treatment, requiring optimal perioperative management and tailored 
anesthetic approaches, especially in obese patients at higher risk of postoperative residual curarization 
(PORC). Quantitative neuromuscular monitoring is essential to prevent PORC. Acceleromyography 
(AMG) measures muscle movement but may have precision limitations, while electromyography (EMG) 
measures electrical muscle activity and is more reliable. 
Study Objective 
To compare the accuracy and precision of AMG and EMG in measuring the Train-of-Four (TOF) ratio 
during general anesthesia in patients with obesity undergoing bariatric surgery, and to assess 
perioperative usability, recovery times, and postoperative respiratory complications. 
Study Design 
Prospective observational cohort study. Thirty adult patients with pathological obesity (Class II with 
comorbidities or Class III) scheduled for bariatric surgery under general anesthesia will be monitored 
using both AMG and EMG (one sensor applied to each hand) throughout anesthesia and recovery. 
Population 
Inclusion criteria: Adults aged 18–65 years, pathological obesity (Class II with comorbidities or Class III), 
scheduled for bariatric surgery under general anesthesia, and able to provide informed consent. 
Exclusion criteria: Severe acute or chronic respiratory or cardiac disease, end-stage hepatic or renal 
disease, intolerance/allergy to study drugs, or absence of informed consent. 
Sample Size Justification 
Based on Wedemeyer Z. et al., who reported a mean difference of 0.12 (SD 0.13) between AMG and 
EMG TOF ratios in a non-paired comparison, the required sample size for the present paired study was 
estimated using a two-sample t-test for the comparison of means, with a significance level of α = 0.05 

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and a statistical power of 90%. The required number of patients is 25. Allowing for an anticipated 
dropout rate of 16%, a total of 30 patients will be enrolled. This approach is deliberately conservative: 
it provides protection against higher variability in the obese population, ensures robustness for the 
primary analysis of paired mean differences, and offers sufficient power for exploratory secondary 
endpoints. The calculation was performed in R. Unlike Wedemeyer et al., this study evaluates patients 
with obesity under general anesthesia with paired AMG–EMG measurements in the same subject; 
repeated measures will be collected but are analyzed as secondary outcomes and were not included in 
the sample size calculation. In the analysis, the distribution of paired differences will be assessed 
(Shapiro–Wilk, QQ-plots), and if normality is not satisfied, non-parametric methods (Wilcoxon signed-
rank test) will be applied. 
Anesthesiologic Approach 
Pre-anesthesia: Standard cardio-respiratory monitoring and peripheral venous access placement in the 
preoperative area. Intraoperative: Completion of monitoring with anesthesia depth sensor, TOF 
monitoring (AMG on one hand, EMG on the other), and radial arterial catheter placement.  
General anesthesia will follow the unit’s standardized bariatric protocol. Neuromuscular parameters 
will be recorded in the anesthesia record and on a dedicated case report form by an independent 
investigator. 
Post-anesthesia: After TOF ratio > 0.9 is reached, the patient will be extubated, monitored in PACU, 
and discharged to the ward once criteria are met. 
 
AMG 
EMG 
 
 
 

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Outcome Measures 
Primary: The primary endpoint will be the mean paired difference in TOF ratio values between AMG 
and EMG, evaluated on standardized paired measurements at baseline (before induction) and recovery 
(after reversal). The corresponding 95% confidence interval (CI) of the mean paired difference will be 
reported. 
Supportive analyses Accuracy and precision of AMG vs EMG will be further assessed using Bland–
Altman analysis (bias and limits of agreement, with SD of the bias as measure of precision) and Lin’s 
concordance correlation coefficient (CCC). Repeated intraoperative measurements (induction, 
maintenance, recovery progression) will be analyzed separately as exploratory endpoints to evaluate 
phase-related variations in AMG–EMG comparison. 
 
Secondary: Time to optimal intubation conditions (TOF count = 0 with PTC confirming deep block), 
duration and stability of deep block (PTC < 5), time to recovery (TOF ≥ 0.9) after sugammadex, 
usability/quality ratings of AMG and EMG (1–5 scale, including setup time, signal stability, and 
measurement quality), incidence of postoperative respiratory complications (from extubation until 
ward discharge), and perioperative changes in HR, MAP, SpO₂, and perfusion index. 
 
Statistical Analysis 

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Continuous variables will be summarized as mean ± standard deviation (SD) or median and 
interquartile range (IQR), with normality assessed using the Shapiro–Wilk test. Paired comparisons 
between AMG and EMG will be performed using the paired t-test or the Wilcoxon signed-rank test, as 
appropriate. Categorical variables will be expressed as counts and percentages. TOF ratios will be 
repeatedly measured at predefined perioperative timepoints (baseline, during block, and recovery). 
These repeated measures will be analyzed using repeated-measures ANOVA if assumptions hold, or 
the Friedman test otherwise. If the global test is significant, post-hoc pairwise comparisons between 
timepoints (e.g., vs baseline) will be performed with appropriate correction for multiple testing. 
Multivariate logistic regression will be used to explore predictors of dichotomous outcomes (e.g., 
postoperative respiratory complications). Stepwise selection with the Akaike Information Criterion 
(AIC) will guide model building. Multicollinearity among predictors will be assessed using the Variance 
Inflation Factor (VIF). Results will be reported as odds ratios (OR) with 95% confidence intervals (CIs). 
Statistical significance will be set at p < 0.05. Analyses will be performed in R. Missing data will not be 
imputed unless more than 10% of recovery values are missing and the absence is plausibly random, in 
which case a Last Observation Carried Forward (LOCF) approach will be considered. Accuracy will be 
evaluated relative to the clinical reference TOF ratio of 1.0 in predefined windows where 1.0 is 
expected (baseline pre-block and recovery prior to PACU discharge). Results will be reported both as 
raw TOF values and as baseline-normalized TOF (TOF/current ÷ TOF/baseline). Accuracy summaries will 
include bias and precision, the proportion of measurements within ±0.05 and ±0.10 of 1.0, and an 
equivalence assessment to 1.0 using two one-sided tests (TOST) with margins of ±0.10. Agreement 
between methods (AMG vs EMG) will be reported as supportive analyses using Bland–Altman plots 
(bias and 95% limits of agreement) and Lin’s concordance correlation coefficient (CCC). Primary 
comparisons will use paired statistical methods. Accuracy versus 1.0 will be summarized separately in 
baseline and recovery windows (bias, SD/RMSE, proportions within ±0.05 and ±0.10, TOST ±0.10). The 
detailed Statistical Analysis Plan (SAP) is included as a technical appendix to this protocol. 
 
 
 
 

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References 
1. NCD Risk Factor Collaboration (NCD-RisC). Worldwide trends in underweight and obesity from 
1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million 
children, adolescents, and adults. Lancet. 2024 Mar 16;403(10431):1027-1050 
2. Murphy GS, Szokol JW, Marymont JH, Greenberg SB, Avram MJ, Vender JS. Residual 
neuromuscular blockade and critical respiratory events in the postanesthesia care unit. Anesth 
Analg. 2008 Jul;107(1):130-7. 
3. Carron M, Tamburini E, Ieppariello G, Linassi F. Br J Anaesth. 2023 Jun;130(6):e461-e463. 
4. Fuchs-Buder T, Romero CS, Lewald H, Lamperti M, Afshari A, Hristovska AM, Schmartz D, 
Hinkelbein J, Longrois D, Popp M, de Boer HD, Sorbello M, Jankovic R, Kranke P. Peri-operative 
management of neuromuscular blockade: A guideline from the European Society of 
Anaesthesiology and Intensive Care. Eur J Anaesthesiol. 2023 Feb 1;40(2):82-94. 
5. Naguib M, Brull SJ, Johnson KB. Conceptual and technical insights into the basis of neuromuscular 
monitoring. Anaesthesia. 2017 Jan;72 Suppl 1:16-37 
6. Wedemeyer Z, Michaelsen KE, Jelacic S, Silliman W, Lopez A, Togashi K, Bowdle A. Accuracy and 
Precision of Three Acceleromyographs, Three Electromyographs, and a Mechanomyograph 
Measuring the Train-of-four Ratio in the Absence of Neuromuscular Blocking Drugs. 
Anesthesiology. 2024 Aug 1;141(2):262-271.  
7. Carron M, Safaee Fakhr B, Ieppariello G, Foletto M. Perioperative care of the obese patient. Br J 
Surg. 2020 Jan;107(2):e39-e55. 
8. Kotake Y, Ochiai R, Suzuki T, Ogawa S, Takagi S, Ozaki M, Nakatsuka I, Takeda J. Reversal with 
sugammadex in the absence of monitoring did not preclude residual neuromuscular block. Anesth 
Analg. 2013 Aug;117(2):345-51.  
9. Wan X, Wang W, Liu J, Tong T. Estimating the sample mean and standard deviation from the 
sample size, median, range and/or interquartile range. BMC Med Res Methodol. 2014 Dec 
19;14:135. 
 
 
 

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Part B – Statistical Analysis Plan (SAP) 
1. Introduction and Purpose 
This Statistical Analysis Plan (SAP) details the pre-specified analyses for the OBAEG study and 
complements the Study Protocol. 
2. Study Overview 
Design: Prospective observational cohort. 
Population: Adults 18–65 years with pathological obesity (Class II with comorbidities or Class III) 
undergoing bariatric surgery under general anesthesia. 
Sample size: 30 patients (25 required by power calculation + 16% anticipated dropout). 
3. Objectives and Endpoints 
Primary Objective: To evaluate the difference in Train-of-Four (TOF) ratio measurements between 
AMG and EMG during general anesthesia. 
Primary Endpoint: The mean paired difference in TOF ratio values between AMG and EMG, evaluated 
on standardized paired measurements at baseline (before induction) and recovery (after reversal). The 
corresponding 95% confidence interval will be reported. 
Supportive Endpoints: 
• Accuracy and precision of AMG vs. EMG will be further characterized through Bland–Altman 
analysis (bias and 95% limits of agreement, with the SD of the bias as measure of precision). 
• Concordance between AMG and EMG will be quantified using Lin’s concordance correlation 
coefficient (CCC) with 95% confidence intervals. 
• Repeated intraoperative AMG–EMG measurements (induction, maintenance, recovery 
progression) will be analyzed separately as exploratory endpoints to assess phase-related 
variations in AMG–EMG comparison. 
 
Secondary Endpoints: 
 - Time to optimal intubation conditions (TOF count = 0 with PTC confirming deep block). 
 - Duration and stability of deep neuromuscular block (PTC < 5). 
 - Time to recovery to TOF ratio ≥ 0.9 after sugammadex. 
 - Usability/quality ratings (1–5 scale) for AMG and EMG (setup time, signal stability, measurement   

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quality). 
 - Incidence of postoperative respiratory complications after tracheal extubation until ward discharge. 
 - Perioperative changes in HR, MAP, SpO₂, and perfusion index. 
4. Analysis Populations 
Full Analysis Set (FAS): All enrolled participants with at least one valid paired AMG–EMG measurement. 
Per-Protocol Set (PPS): Subset of FAS without major protocol deviations that could affect 
neuromuscular monitoring. 
Safety Set: All participants receiving general anesthesia and neuromuscular monitoring. 
5. General Statistical Principles 
Two-sided tests with α = 0.05. Continuous variables summarized as mean ± SD or median (IQR) per 
distribution (Shapiro–Wilk). Categorical variables summarized as counts and percentages with 95% CIs. 
Given the within-subject design, primary comparisons use paired methods. No formal multiplicity 
adjustment is planned; secondary analyses are supportive and considered exploratory. Therefore, p-
values for secondary and exploratory endpoints will be reported descriptively rather than 
confirmatory. 
6. Handling of Data and Missing Values 
The primary endpoint requires paired AMG–EMG values. If either value in a pair is missing at a time 
point, that pair is excluded from paired analyses but retained for descriptive summaries. No routine 
imputation is planned. If >10% of recovery-time data are missing and missingness is plausibly at 
random, a sensitivity analysis using last-observation-carried-forward (LOCF) may be conducted. 

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7. Statistical Methods 
7.1 Primary Endpoint: Mean Paired Difference Between AMG and EMG TOF Ratio 
The primary analysis will evaluate the mean paired difference in TOF ratio values between AMG and 
EMG, based on standardized paired measurements at baseline (before induction) and recovery (after 
reversal). The mean difference and corresponding 95% confidence interval will be estimated and 
reported. The hypothesis test will be performed using a paired t-test, or a Wilcoxon signed-rank test if 
normality assumptions are not met. 
Supportive Analyses 
Agreement between AMG and EMG will be further characterized using Bland-Altman analysis (mean 
bias and 95% limits of agreement) and Lin's concordance correlation coefficient (CCC) with 95% 
confidence intervals. Accuracy relative to the "ideal" TOF value of 1.0 will be evaluated as a supportive 
analysis in two specific time windows: 
• Baseline - median of at least 3 stable TOF measurements before rocuronium administration. 
• Recovery - median of at least 3 TOF measurements after the TOF ratio has reached ≥0.9. 
In addition to raw TOF values, a normalized TOF will be calculated as (current TOF / baseline TOF) to 
account for the known tendency of AMG to yield baseline values greater than 1.0. 
Repeated intraoperative paired measurements (post-induction, during surgery, and pre-extubation) 
will be analyzed as exploratory endpoints to assess phase-related variations. 
 
7.2 Secondary Endpoints 
Time-to-event analyses 
• Induction (TOF = 0) 
Paired times to reach the clinical threshold will be analyzed using the Wilcoxon signed-rank 
test. Kaplan–Meier curves (AMG vs EMG) will be presented to visualize time distributions 
and the proportion of patients not yet at the threshold over time. If censoring is non-
negligible, a stratified log-rank test (stratified by patient) will be performed as a supportive 
analysis. 
• Maintenance – duration of deep neuromuscular block (PTC < 5) 

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Paired times to block resolution (PTC ≥ 5) will be analyzed using the Wilcoxon signed-rank 
test. Kaplan–Meier curves will be used for visualization and to estimate the proportion of 
patients remaining in deep block over time. If censoring is non-negligible, a stratified log-
rank test will be applied as supportive. 
• Reversal (TOF ≥ 0.9 after sugammadex) 
Paired times to reach the clinical threshold will be analyzed using the Wilcoxon signed-rank 
test. Kaplan–Meier curves will be plotted to visualize time distributions and the proportion 
of patients still below threshold over time. If censoring is non-negligible, a stratified log-
rank test will be used as supportive analysis.  
• 
Usability and signal quality ratings: Analyzed as paired ordinal data using the Wilcoxon 
signed-rank test; effect sizes will also be reported. 
• 
Postoperative respiratory complications: Will be presented as absolute counts and 
percentages. 
• 
Physiological variables (heart rate, mean arterial pressure, SpO₂, perfusion index) 
1. Longitudinal description across predefined time points. 
Results will be reported as mean ± SD or median (IQR) with 95% CIs alongside p-values, 
and within-patient changes will be tested using repeated-measures ANOVA (if 
approximately normal) or Friedman’s test (if non-normal). Post-hoc pairwise 
comparisons will use Bonferroni/Holm adjustments.  
2. Event-aligned comparisons at clinical thresholds 
For each patient, physiological parameters recorded at the AMG trigger will be paired 
with those recorded at the EMG trigger for the same clinical threshold 
o Induction: values at TOF = 0 (AMG) vs TOF = 0 (EMG) 
o Reversal: values at TOF ≥ 0.9 (AMG) vs TOF ≥ 0.9 (EMG) 
This approach allows exploration of whether specific physiological variables (e.g., 
perfusion index, respiratory and hemodynamic parameters) show systematic differences 
depending on which monitoring modality reaches the threshold first. 
3. Paired comparisons will use the paired t-test or Wilcoxon signed-rank test, as 
appropriate. 

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Operational rule: the measurement at the trigger is the closest available within ±10 s (or 
within the same minute); otherwise set to missing. Results will be reported as mean (or 
median) paired differences with 95% confidence intervals, in addition to p-values, to 
allow assessment of both statistical and clinical relevance. 
7.3 Exploratory/Sensitivity Analyses 
Mixed-effects models (patient-level random effects) to account for repeated paired measurements 
with fixed effect for method and time window. 
8. Sample Size Justification 
Based on Wedemeyer Z. et al., who reported a mean difference of 0.12 (SD 0.13) between AMG and 
EMG TOF ratios in a non-paired comparison, the required sample size for the present paired study was 
estimated using a two-sample t-test for the comparison of means, with a significance level of α = 0.05 
and a statistical power of 90%. The required number of patients is 25. Allowing for an anticipated 
dropout rate of 16%, a total of 30 patients will be enrolled. This approach is deliberately conservative: 
it provides protection against higher variability in the obese population, ensures robustness for the 
primary analysis of paired mean differences, and offers sufficient power for exploratory secondary 
endpoints. The calculation was performed in R. Unlike Wedemeyer et al., this study evaluates patients 
with obesity under general anesthesia with paired AMG–EMG measurements in the same subject; 
repeated measures will be collected but are analyzed as secondary outcomes and were not included in 
the sample size calculation. In the analysis, the distribution of paired differences will be assessed 
(Shapiro–Wilk, QQ-plots), and if normality is not satisfied, non-parametric methods (Wilcoxon signed-
rank test) will be applied. 
9. Software 
Analyses will be conducted in R.  
10. Tables, Listings, and Figures (TLFs) 
TLFs will include: demographics/baseline characteristics; descriptive summaries of TOF measurements 
by method and time; Bland–Altman plots; concordance coefficients; Kaplan–Meier curves for time to 
event (induction and reversal); distributions of detection and recovery times; complications summary; 
and longitudinal plots of physiological parameters. 

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11. Deviations from SAP 
Any deviation from the pre-specified analyses will be documented in the final report with justification 
and impact assessment.