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Impact of Escalating Cognitive Workload and Temporal Demands on Surgeons Cognitive Function

Harsimrat Singh1*, Hemel Modi1, Guang-Zhong Yang2, Ara Darzi1 and Daniel R. Leff1
  • 1 Imperial College London, Surgery and Cancer, United Kingdom
  • 2 Faculty of Engineering, Imperial College London, Hamlyn Centre of Medical Robotics, United Kingdom

Introduction: The use of neuroimaging to investigate surgeons’ cognition is rapidly expanding and has deepened our understanding of technical skill acquisition, decision-making processes and the effects of fatigue. However, there is little evidence regarding the impact of intraoperative mental demands on operator brain function. Surgery is a complex endeavour requiring high levels of attention and concentration to maintain precise motor control and technical proficiency. However, the operating environment is full of distractions and interruptions which require the surgeon to attend to multiple events simultaneously in addition to performing the procedure at hand. However, mismatch between operative demands and cognitive resources potentially disrupts surgical performance (Arora, Sevdalis, Aggarwal, et al., 2010; Arora, Sevdalis, Nestel, et al., 2010; Darzi, Munz, Dosis, Bann, & Moorthy, 2003; Goodell, Cao, & Schwaitzberg, 2006; Pluyter, Buzink, Rutkowski, & Jakimowicz, 2010), jeopardising patient outcomes (Birkmeyer et al., 2013; Hogg et al., 2016). The impact of distraction is expertise-dependent (Ghazanfar, Cook, Tang, Tait, & Alijani, 2015; Meneghetti, Pachev, Zheng, Panton, & Qayumi, 2012); suggesting that experienced surgeons possess greater cognitive capacity to attend to additional stressors during surgery without jeopardising motor ability. Novice surgeons may sacrifice attention on one task in order to stabilise their performance on another. Whilst previous work (Guru et al., 2015; Leff et al., 2008, 2010, 2017; Modi, Singh, Orihuela-Espina, et al., 2017; Modi, Singh, Yang, Darzi, & Leff, 2017) demonstrated an expertise-related disparity in attention and concentration when performing a surgical task under a temporal demand, the cumulative effect of escalating mental demands and temporal stress (reflecting a more realistic operating environment) on operator brain function remains unknown. We hypothesise that prefrontal activation increases to cope with these cognitive demands until a critical point beyond which no further increase is possible. This paper tests this hypothesis by addressing the impact of distracting stressors during complex surgical procedures using optical brain imaging. Specifically, we assessed PFC haemodynamic responses in surgeons performing a laparoscopic suturing drill (motor task) under time pressure whilst simultaneously engaging in medical decision-making scenarios (cognitive task). Methods and Materials Subjects and Experimental Set-up Twenty-nine surgeons enrolled in the study (median age=33 years, 9F) and were grouped based on expertise into ‘junior’, ‘intermediate’, and ‘senior’ cohorts. The ETG-4000 Optical Topography System (Hitachi Medical Co, Japan) was used to measure haemodynamic data across 24 prefrontal channels. Subjective workload was quantified using the Surgical Task Load Index [SURG-TLX (au)] questionnaire. Heart rate was continuously recorded using a portable electrocardiogram (Bioharness, Zephyr Technology, USA). Technical skill was assessed using Task Progression Score (au), Error Score(mm), Leak Volume(ml) and Knot Tensile Strength(N). Task Paradigm Subjects performed a laparoscopic suturing task on a bench-top trainer (iSim2, iSurgicals, UK). The task involved inserting a 2-0 Vicryl® suture on either side of a defect in a Penrose drain, and formulating a surgical knot under four conditions: (1) ‘self-paced’ (SP), in their own time; (2) ‘time pressure’ (TP), a two-minute per knot time restriction; (3) ‘self-paced’ knot tying whilst simultaneously answering a medical decision-making scenario (SP-DM); and (4) ‘time pressure’ knot tying with a decision-making scenario (TP-DM). A block design with five trials per experimental condition with 30 second inter-trial rest periods between each knot was designed. Results Subjective Workload In junior residents, subjective workload was significantly greater in TP compared to SP (mean SURG-TLX score ± SD: SP=158.82 ± 41.99, TP=229.27 ± 26.48; p=0.002), SP-DM compared to SP, and finally TP-DM compared to SP. Additionally, subjective workload was greater in TP-DM compared to TP, and TP-DM compared to SP-DM. Although SURG-TLX scores increased in the time pressure and decision-making conditions in intermediate and senior groups, these differences were not statistically significant (Figure1(a)). Technical Performance Amongst junior residents, a significantly lower progression score was observed in the TP compared to SP, and compared to SP-DM. Furthermore, task progression was significantly inferior in TP-DM compared to SP, and compared to SP-DM. Similarly, in intermediate residents progression was significantly inferior in TP compared to SP, and compared to SP-DM (see Figure 1(b)). Additionally, inferior progression was identified in TP-DM compared to SP, and compared to SP-DM. There were no significant differences in progression between conditions amongst the senior residents. There were no significant differences in error score between experimental conditions in any group. However, there was significant differences in leak volume between experimental conditions in all groups with mean leak volume in the TP condition significantly greater than in the SP condition. In all resident groups, leak volume in TP-DM condition was significantly greater than in the SP-DM condition while leak volume in the SP condition was significantly less than in the SP-DM condition. There were no significant differences in knot tensile strength between experimental conditions in any group. Prefrontal Cortical Haemodynamic Data Senior residents demonstrated HbO2 activation responses in SP (16 channels), SP-DM (15 channels), and TP (21 channels) conditions, chiefly in the bilateral VLPFC and DLPFC, and in-line with the hypothesis, deactivation responses in the highest workload condition i.e. TP-DM (17 channels), primarily within the bilateral VLPFC. In junior and intermediate groups, increases in HbO2 concentration were evident in a similar number of channels in both the SP as in the TP condition (juniors: 11 channels, intermediates: 13 channels). The remaining channels exhibited a decrease in HbO2 (juniors: 13 channels, intermediates: 11 channels), particularly in the bilateral VLPFC. In both these residents subgroups, most channels demonstrated a decrease in HbO2 in the SP-DM condition (juniors: 15 channels, intermediates: 16 channels), especially within the bilateral VLPFC and DLPFC; whereas in the TP-DM condition, more channels exhibited a HbO2 increase (juniors: 16 channels, intermediates: 12 channels), particularly within the bilateral VLPFC and DLPFC. Conclusions Experienced surgeons maintain attention when faced with single intraoperative stressors, but demonstrate prefrontal disengagement during the highest workload states when simultaneously processing temporal and cognitive demands. Less experienced surgeons struggle to maintain prefrontal engagement even when faced with a single stressor, but when experiencing multiple demands prefrontal engagement is observed, possibly reflecting task allocation preferences, focusing cognitive resources on one stressor/task rather than processing multiple demands simultaneously.

Figure 1
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Keywords: functional near-infrared spectroscopy (fNIRS), prefrontal cortex (PFC), Surgeons, Performance monitoring, mental stress

Conference: 2nd International Neuroergonomics Conference, Philadelphia, PA, United States, 27 Jun - 29 Jun, 2018.

Presentation Type: Oral Presentation

Topic: Neuroergonomics

Citation: Singh H, Modi H, Yang G, Darzi A and Leff DR (2019). Impact of Escalating Cognitive Workload and Temporal Demands on Surgeons Cognitive Function. Conference Abstract: 2nd International Neuroergonomics Conference. doi: 10.3389/conf.fnhum.2018.227.00062

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Received: 02 Apr 2018; Published Online: 27 Sep 2019.

* Correspondence: Dr. Harsimrat Singh, Imperial College London, Surgery and Cancer, London, United Kingdom, singhharsimrat@gmail.com