K. Yamanouchi1, N. Hayashida1,2, S. Kuba1, C. Sakimura1, F. Fujita1, K. Kanetaka1, M. Takatsuki1, T. Kuroki1, N. Takamura2, S. Eguchi1 1Nagasaki University,Department Of Surgery,Nagasaki, Nagasaki, Japan 2Nagasaki University,Department Of Global Health, Medicine And Welfare, Atomic Bomb Disease Institute,Nagasaki, Nagasaki, Japan
Introduction: Surgeons sometimes experience tension and stress for long periods of time when performing operations. The heart rate variability (HRV) is the variability within single heart beats compared to each other, and has been used as a parameter of the mental load, for example, to assess pilots’ stress levels during flight. The purpose of this study was to evaluate the mental workload of surgeons before, during and after surgical operations, especially during (1) pancreatoduodenectomy (PD), performed by open or laparoscopic methods, and (2) living donor liver transplantation (LDLT), both of which are complex and usually take a long time to complete. Additionally, the parameters were compared in various aspects during the operations.
Methods: We studied 2 surgeons who each had more than 20 years of experience. Before, during and after the operations, the surgeons put on a small monitoring device, which included a bi-axial accelerometer (ACM), thermometer, ECG, central processing unit (CPU), and memory IC. By using the frequency domain method with ECG, we measured the high frequency (HF; with a frequency ranging from 0.15 to 0.4 Hz), which represents parasympathetic activity, the low frequency (LF; with a frequency ranging from 0.04 to 0.15 Hz)/HF frequency ratio, which represents the sympathetic activity, as well as the heart rate.
Results: (1) In all 5 cases of PD, the HF components were significantly lower and the LF/HF ratios were higher during the operation than those before the operation (181.4 vs 479.5 Hz p<0.01, 9.1 vs 2.9 p<0.01). When we reviewed the fluctuations of the values during and after the operation, the HF did not drop in any of these cases. (2) Out of the 4 LDLT, the HF were lower in 2 and the LF/HF higher in 3 procedures during the operation compared to those before the operation. These sympathetic nerve-predominant changes in status did not returned to the baseline for at least one hour after surgery. LDLT is associated with risks of bleeding due to the patients’ liver failure or portal hypertension, and consists of various fatal aspects, i.e., removal of the whole liver, reconstruction of the hepatic veins, portal veins, hepatic artery and bile duct, and reperfusion of the implanted liver. When we compared the values in various aspects in LDLT, in all cases, the HF were significantly lower and/or LF/HF were significantly higher during the reconstruction of vessels or bile ducts than during the removal of the liver.
Conclusion: While the sympathetic nerve activity increased during surgeries in most cases compared with the levels before the operation, the autonomic nerve status did not return to the baseline for quite a while after surgery. Moreover, various procedures during operations induce diverse autonomic nerve changes in surgeons. Thus, monitoring the changes in the autonomic nervous activities could provide a powerful tool for the objective evaluation of the mental workload of operations for surgeons.