Objective: To test the hypothesis that fatigue-induced performance decline in surgical residents is associated with changes in brain function as detected by functional near-infrared spectroscopy.
Methods: Surgical residents (n = 7) participated in a prospective study involving 2-hourly objective measurements of neurocognitive skill (arithmetic calculations using Nintendo “brain training”), technical performance (surgical knot tying on a trainer, and monitoring time taken, path length and number of movements), and introspective fatigue (questionnaire-based) across 10 hours of acute sleep deprivation (10:00 PM to 8:00 PM. Simultaneously, changes in cortical oxyhemoglobin (HbO2), deoxyhemoglobin (HHb), and total hemoglobin (HbT), inferring prefrontal function, were recorded by using functional near-infrared spectroscopy.
Results: Arithmetic performance remained stable despite increasing levels of subject fatigue (time: P = 0.07, errors: P = 0.70, efficiency: P = 0.58). Technical skill improved between the first (10:00 PM and the second (12:00 AM sessions (P < 0.05) and stabilized thereafter (12:00 AM to 8:00 AM. Greater activation was required to complete cognitive versus technical drills. Stimulus type (0: cognitive, 1: technical) was found to be an independent predictor of changes in cortical excitation (HbO2: P < 0.01, HHb: P < 0.05, HbT: P < 0.01). Cortical responses to the cognitive task increased over the course of the simulated night shift. In addition, “time interval” was observed to be an independent predictor of cortical hemodynamic change (HbO2: P < 0.01, HbT: P < 0.01).
Conclusions: Neurocognitive tasks may tax the sleep-deprived resident more than well-learned technical skills. Performing cognitive skills at night, such as decision making, may depend upon enhanced prefrontal recruitment indicative of a focused attentional strategy and/or compensation to sleep deprivation. Further work should focus on determining whether errors in performance are associated with attentional lapses and failure of cortical compensation.
Seven surgical residents participated in a longitudinal observational study of technical and cognitive skills, incorporating 168 functional brain imaging sessions acquired across the circadian low. Stable technical and cognitive performance was coupled to increasing subjective fatigue and enhanced prefrontal activation. The results suggest that prefrontal excitation may assist trainees in ameliorating the effects of acute sleep deprivation.
*Royal Wolfson Image Computing Laboratory and Department of Biosurgery and Surgical Technology, Imperial College London, United Kingdom;
†Biomedical Optics Research Laboratory, Department of Medical Physics and Bioengineering, University College London, United Kingdom.
Article accepted for 130th Annual Meeting of the American Surgical Association, The Fairmount, Chicago, Ill, April 8 to 10, 2010.
DRL drafted the article and was involved in all aspects of the investigation, including study design, data collection, and data analysis. FOE assisted with data collection and data analysis and provided a critical evaluation of the article. VK assisted with data acquisition. TA advised on statistical methodology and assisted with statistical analysis of the data. CE provided advice and support on aspects of functional near-infrared spectroscopy study design and experimentation. GZY and AWD led the research project and were involved in all aspects of study design, ethical approval, hypothesis testing, provision of equipment, and laboratory time. JW, GZY, and AWD also critically edited the final draft of the article.
Reprints: Ara W. Darzi, Department of Biosurgery and Surgical Technology, Division of Surgery, Oncology, Reproductive Biology, and Anaesthetics, Imperial College London, 10th Floor, QEQM Wing, St Mary's Hospital, Praed St, London W2 1NY, United Kingdom. E-mail: firstname.lastname@example.org.