The National Aeronautics and Space Administration-task load index: NASA-TLX: evaluation of its use in surgery

Background The technical difficulty an operation creates for a surgeon is difficult to measure. Current measures are poor surrogates. In both research and teaching settings it would be valuable to be able to accurately measure this degree of difficulty. The National Aeronautics and Space Administration Task Load Index (NASA TLX) is a multi-dimensional scale designed to obtain workload estimates relating to a task. This study aimed to evaluate the NASA TLX as an objective measure of technical difficulty of an operation. Methods Seven surgeons performed 127 pre-defined operations (minimally invasive right hemicolectomy & re-do bariatric surgery) and recorded a NASA TLX score after each operation. These scores were compared to numerous clinical parameters and the score was correlated with the subjective measure of whether the surgeon categorized the operation as "easy", "moderate" or "difficult". Results The NASA TLX score was significantly correlated with operative duration, blood loss, previous abdominal surgery and the surgeons' assessment of difficulty. It did not correlate with intra-operative or post-operative complications, conversion to open surgery or length of stay. Conclusions The NASA TLX score provides a graded numerical score that that correlated significantly with the surgeon's assessment of the technical difficulty, and with operative duration, intra-operative blood loss and previous abdominal surgery. This novel application of this tool could be employed in both research and teaching settings to score surgical difficulty and monitor a trainee's proficiency over time.