Quantifying the Stress Levels of Cardiac Surgery Residents during Coronary Artery Bypass Grafting

Objectives: Coronary artery bypass grafting (CABG) is associated with stress for surgeons, especially for residents in training. The aim of this study was to investigate the extent of intraoperative stress by measuring the heart rate variability (HRV) of cardiac surgery residents and to compare stress levels during different steps of CABG.

Methods: HRV was measured in two residents, who performed CABG operations as the first operator under guidance of a senior physician. Both residents were in the surgical training program for 7 years and were between 30 and 35 years old. They were healthy with no previous conditions or medication. Overall, 23 elective CABG operations were assessed. A portable Holter-2-channel electrocardiogram (ECG) was used to measure the HRV. HRV analysis was performed using the Kubios HRV 2.0 software. Two different HRV levels were compared with regard to two steps of the operation: the preparation of the left internal mammary artery (LIMA) and the aortic cross-clamping. By HRV analysis, different indicators of stress were evaluated: mean heart rate (HR), mean RR interval, stress index (SI), index of sympathetic (SNSI) and parasympathetic (PNSI) nervous system.

Result: The mean operation time was 248 minutes and mean cross-clamp time was 68 minutes. The HRV analysis of the intraoperative ECGs revealed a higher stress level amongst the residents during harvesting of the LIMA in comparison to cross-clamp time. The mean HR [bpm] (95.5 vs. 87.3; p < 0.001), the SI (15.28 vs. 11.85; p = 0.001), and SNSI (3.07 vs. 1,95; p < 0.001) were significantly higher in the LIMA takedown period. The lower values of mean RR [ms] (631.8 vs. 691.9; p < 0.001) and PNSI (−2.28 vs. −1.79; p < 0.001) during cross-clamp time confirmed the findings too, revealing a higher stress response during LIMA preparation.

Conclusion: HRV is an objective method for the assessment of surgeons´ stress response during surgery. Interestingly, our results show that residents are exposed to higher stress levels during preparation of the LIMA in comparison to the cross-clamp period. Possible explanations for our findings are the presence of senior physicians during the cross-clamp time or the importance of harvesting an intact LIMA for a successful operation which may influence the stress level. Further investigations are required to confirm our findings and might bear options to reduce stress levels in surgical training programs.

Publication History

Article published online:
19 February 2021