Enhancing Laparoscopic Skill Acquisition and Retention With Transcranial Direct-current Stimulation

Rationale: Recent changes in medical training environments have resulted in many trainees lacking sufficient opportunity to acquire specific skills necessary for their specialty. New methods to enhance the acquisition and retention of medical and surgical skills are required to ensure the quality of the future physician workforce. Transcranial direct-current stimulation (tDCS) is an emerging method of non-invasive brain stimulation that has been show to safely enhance motor learning in adults and children. Even a modest enhancement of acquisition and retention of medical-surgical skill with tDCS carries the potential to accelerate skill training for health care providers, thereby contributing to greater training efficiency and improved patient outcomes.

Objectives: The objective of this study is to assess whether tDCS can enhance the acquisition and retention of laparoscopic surgical ability.

Ethics:This study has been approval by the University of Calgary Research Ethics Board

Design: Randomized, double blind, sham-controlled trial to evaluate the ability of tDCS to enhance learning and retention of laparoscopic skills.

Transcranial Direct-Current Stimulation: The tDCS methods used are based on best-available evidence and practices, and will be applied in a standardized fashion by experienced investigators. Anodal tDCS will be delivered through saline-soaked sponge electrodes using a NeuroConn Direct-Current Stimulator (NeuroConn, Ilmenau, Germany). The anode will be centered 2cm posterior to the left primary motor cortex (localized using the 10-20 EEG System), with the cathode over the contralateral supraorbital area. Both anodal and sham tDCS groups will have the current ramped up to 1milliamp over 30 seconds. In the anodal tDCS group, the current will be held for 20 minutes. In the sham tDCS condition, the current will be held for only 60 seconds (no changes in cortical excitability) followed by a 30 second ramp-down.

Participants: Medical students (years 1-3) and general surgery residents (Post-Graduate Year 1-5) from the Cumming School of Medicine (University of Calgary) will be recruited. To ensure comparable baseline skills, trainees will be excluded if they have undergone formal laparoscopic training in the past 3 months (medical students only).

Sample size calculations are based on the performance measures for the pattern cutting score, determined through pilot studies (discussed below). Based on a two-fold greater improvement in score at post-training, power of 90% and type-1 error of 0.05, the investigators estimate a sample size of a minimum of 48 participants (n=24 per stimulation condition, with an equal number of residents and medical students per arm).

Study Design: A short questionnaire will be completed to determine demographic characteristics, including: gender, age, level of training, date of last completed Fundamentals of Laparoscopic Surgery course (if applicable), how many times participants have performed laparoscopic surgery on a patient, how many times participants have performed laparoscopic tasks on a laparoscopic simulator, how often participants play video games, and how often participants play a musical instrument.

Participants will be recruited at the Advanced Technical Skills and Simulation Laboratory (University of Calgary) and be oriented to the workspace. Participants will complete laparoscopic task training on a laparoscopic box trainer (Fundamentals of Laparoscopic Surgery Trainer System, Limbs \& Things Inc, Georgia, USA) consisting of an optic camera, laparoscopic instruments, and a monitor that displays the field of view. The optic camera view will be recorded for retroactive scoring. Participants will view a standardized laparoscopic training video, created by an expert in laparoscopic surgery, demonstrating two Fundamentals of Laparoscopic Surgery (FLS) tasks that will be performed using the simulator: a peg-transfer (A) and pattern cutting task (B). The peg-transfer task requires the use of two dissectors to transfer six rings to pegs on the opposite end of the pegboard, and back to the original location. The pattern-cutting task involves a 10x10cm piece of gauze with a 4cm-diameter circle pre-drawn in the middle that is placed at the center of the work-board. Participants are required to use a dissector and endoscopic scissors to cut the marked circle, freeing it from the surrounding unmarked gauze. A time score will be calculated by subtracting the completion time in seconds from the task cut-off time of 300 seconds. An error score will be calculated for each tasks as either: the percentage of pegs that could not be transferred due to being dropped outside of the field of view (i.e. 1 of 6 pegs lost = 17 second penalty), or the percentage area deviation of cutting a perfect circle. A total score is calculated by subtracting the error score from the time score. These two FLS tasks represent skills that require bimanual (peg-transfer) or unimanual (pattern cutting) abilities. Furthermore, these two tasks were chosen as scores correlate with training level, and are predictive of intraoperative performance.

Participants will complete task A followed by task B, establishing baseline skill. Tasks will be recorded and scored retroactively, blinded to group allocation, to quantify time and error scores. Participants will be computer randomized to receive sham or active tDCS. Participants will perform the two FLS tasks in an interleaved manner (ABAB), a paradigm suggested to enhance laparoscopic skill acquisition, with eight training repetitions of each task. Following the final training block, the tDCS electrodes will be removed, and a final task evaluation will be performed for both task A and B. The Purdue Pegboard Test (PPT) will be performed at baseline and post-training to examine unilateral hand function, serving as a safety measure. Six weeks following the training the participants will return to assess retention of laparoscopic skill, with a single repetition of task A and B. Emerging evidence suggests that a significant decay in laparoscopic skill is present six weeks following training. The amount of laparoscopic practice between the training day and follow-up will be factored for residents, to ensure that standard training remains uninterrupted.

Data Analysis: Mean change in each outcome from baseline to post-training to follow-up will be compared between tDCS and sham (two-way repeated-measure ANOVA for factors "stimulation type" and "evaluation time point"). Two-way repeated-measures ANOVA for factors "stimulation type" and "training block" will explore the interaction between tDCS and training with or without feedback for each outcome. Any decay in PPT score in either sham or anodal tDCS groups will be evaluated using a paired-tDCS. Medical students and specialty residents will be evaluated independently. Level of training of residents will be factored retroactively into our analysis.