Indirect calorimetry as a non-invasive method of cardiorespiratory monitoring in the intraoperative period in cardiac surgical patients

Introduction. Perioperative disturbances of energy metabolism in cardiac surgery patients significantly affect postoperative course and outcomes. Under conditions of surgical stress and cardiopulmonary bypass (CPB), conventional approaches to metabolic assessment have limited diagnostic value.

The objective was to evaluate perioperative changes in cardiorespiratory function and energy metabolism in cardiac surgery patients with uncomplicated operations performed under general anesthesia using CPB.

Materials and methods. Thirty patients were included in the study. Metabolic and hemodynamic parameters were assessed at four stages: after anesthesia induction, during sternotomy, before CPB initiation, and in the early post-perfusion period. Indirect calorimetry (IC) was used to measure oxygen consumption (VO2), carbon dioxide production (VCO₂), resting energy expenditure (REE), and respiratory quotient (RQ). Central hemodynamics were evaluated using transesophageal echocardiography. Blood gas parameters, lactate, and glucose levels were also analyzed.

Results. The lowest VO₂ index values were recorded after anesthesia induction (106.55 ± 30.69 ml∙min^–1⋅m^–2), reflecting a state of pharmacologically induced metabolic suppression. From the sternotomy stage onward, a persistently increased level of energy expenditure was observed until the end of surgery. In the early post-perfusion period, VO_2I index increased to 166.59 ± 44.69 ml⋅min^–1⋅m^–2, exceeding values calculated by the reverse Fick method by 76%. Predictive equations (Harris–Benedict) underestimated actual energy requirements by an average of 29%. Reduced RQ values (0.54–0.59) indicated predominant lipid substrate utilization. After CPB discontinuation, blood lactate levels increased 2.5-fold and blood glucose levels by 36%. A significant correlation between VO₂ and cardiac output was observed (r = 0.63; p = 0.001).

Conclusion. Perioperative changes in energy metabolism are stage-dependent and predominantly adaptive in nature. Indirect calorimetry enables objective assessment of metabolic and perfusion status at different stages of cardiac surgery.

1. Eremenko A. A., Sorokina L. S., Charchyan E. R. et al. Cardiorespiratory monitoring capabilities using indirect calorimetry during peripheral veno-arterial extracorporeal membrane oxygenation in a patient following emergency cardiac surgery. Messenger of anesthesiology and resuscitation, 2025, vol. 22, no. 4, pp. 86–92. (In Russ.). https://doi.org/10.24884/2078-5658-2025-22-4-86-92.

2. Kochoyan I. Sh., Obukhova А. А., Zaripova Z. A. Applying of classic parameters of cardiorespiratory exercise testing to identify high-risk patients in thoracic surgery. Messenger of anesthesiology and resuscitation, 2025, vol. 22, no. 2, pp. 40–46. (In Russ.) https://doi.org/10.24884/2078-5658-2025-22-2-40-46.

3. Bolli R. Mechanism of myocardial stunning. Circulation, 1990, vol. 82, no. 3, pp. 723–738. https://doi.org/10.1161/01.CIR.82.3.723.

4. Brandi L. S., Bertolini R., Pieri M. et al. Comparison between cardiac output measured by thermodilution technique and calculated by O2 and modified CO2 Fick methods using a new metabolic monitor. Intensive Care Medicine, 1997, vol. 23, no. 8, pp. 908–915. https://doi.org/10.1007/s001340050431.

5. Convertino V. A., Lye K. R., Koons N. J. et al. Physiological comparison of hemorrhagic shock and VO2max: a conceptual framework for defining the limitation of oxygen delivery. Experimental Biology and Medicine, 2019, vol. 244, no. 8, pp. 690–701. https://doi.org/10.1177/1535370219846425.

6. Cordoza M., Chan L. N., Bridges E. et al. Methods for estimating energy expenditure in critically ill adults. AACN Advanced Critical Care, 2020, vol. 31, no. 3, pp. 254–264. https://doi.org/10.4037/aacnacc2020110.

7. Crawford T. C., Magruder J. T., Grimm J. C. et al. Complications after cardiac operations: all are not created equal. Annals of Thoracic Surgery, 2017, vol. 103, no. 1, pp. 32–40. https://doi.org/10.1016/j.athoracsur.2016.10.022.

8. Czerny M., Baumer H., Kilo J. et al. Inflammatory response and myocardial injury following coronary artery bypass grafting with or without cardiopulmonary bypass. European Journal of Cardio-Thoracic Surgery, 2000, vol. 17, no. 6, pp. 737–742. https://doi.org/10.1016/S1010-7940(00)00420-6.

9. Donaldson L., Dodds S., Walsh T. S. Clinical evaluation of a continuous oxygen consumption monitor in mechanically ventilated patients. Anaesthesia, 2003, vol. 58, no. 5, pp. 455–460. https://doi.org/10.1046/j.1365-20 44.2003.03123.x.

10. Edwards F. H., Ferraris V. A., Kurlansky P. A. et al. Failure to rescue rates after coronary artery bypass grafting. Annals of Thoracic Surgery, 2016, 102, no. 2, pp. 458–464. https://doi.org/10.1016/j.athoracsur.2016.04.051.

11. Ferrannini E. Theoretical bases of indirect calorimetry. Metabolism, 1988, vol. 37, no. 3, pp. 287–301. https://doi.org/10.1016/0026-0495(88)90110-2.

12. Gilbert E. M., Haupt M. T., Mandanas R. Y. et al. The effect of fluid loading, blood transfusion, and catecholamine infusion on oxygen delivery and consumption in patients with sepsis. American Review of Respiratory Disease, 1986, vol. 134, no. 5, pp. 873–878. https://doi.org/10.1164/arrd.1986.134.5.873.

13. Inoue S., Kuro M., Furuya H. Hyperlactatemia after cardiac surgery with preserved oxygen delivery. European Journal of Anaesthesiology, 2001, vol. 18, no. 9, pp. 576–584. https://doi.org/10.1046/j.1365-2346.2001.00893.x.

14. Jakob S.M., Stanga Z. Perioperative metabolic changes in patients undergoing cardiac surgery. Nutrition, 2010, vol. 26, no. 4, pp. 349–353. https://doi.org/10.1016/j.nut.2009.07.014.

15. Jakobsson J., Vadman S., Hagel E. et al. The effects of general anaesthesia on oxygen consumption: a meta-analysis. Acta Anaesthesiologica Scandinavica, 2019, vol. 63, no. 2, pp. 144–153. https://doi.org/10.1111/aas.13265

16. Jentzer J. C., Berg D. D., Chonde M. D. et al. Mixed cardiogenic-vasodilatory shock: current insights and future directions. JACC: Advances, 2025, vol. 4, no. 1, 101432. https://doi.org/10.1016/j.jacadv.2024.101432.

17. Koekkoek W. A. C., Guan X., van Dijk D. et al. Resting energy expenditure by indirect calorimetry versus ventilator-derived VCO2 method. Clinical Nutrition ESPEN, 2020, vol. 39, pp. 137–143. https://doi.org/10.1016/j.clnesp.2020.07.005.

18. Levy J. H., Tanaka K. A. Inflammatory response to cardiopulmonary bypass. Annals of Thoracic Surgery, 2003, vol. 75, no. 2, pp. 715–720. https://doi.org/10.1016/S0003-4975(02)04650-7.

19. Lopaschuk G. D., Ussher J. R. Evolving concepts of myocardial energy metabolism. Canadian Journal of Cardiology, 2016, vol. 32, no. 7, pp. 850–859. https://doi.org/10.1016/j.cjca.2015.12.015.

20. Lopaschuk G. D., Ussher J. R., Folmes C. D. L. et al. Myocardial fatty acid metabolism in health and disease. Physiological Reviews, 2010, vol. 90, no. 1, pp. 207–258. https://doi.org/10.1152/physrev.00015.2009.

21. Maheshwari K. Principles for minimizing oxygen debt. Best Practice & Research Clinical Anaesthesiology, 2021, vol. 35, no. 4, pp. 543–549. https://doi.org/10.1016/j.bpa.2020.09.004.

22. Murphy E., Steenbergen C. Mechanisms underlying acute protection from cardiac ischemia-reperfusion injury. Physiological Reviews, 2008, vol. 88, no. 2, pp. 581–609. https://doi.org/10.1152/physrev.00024.2007.

23. Oshima T., Berger M. M., De Waele E. et al. Indirect calorimetry in critical care. Journal of Intensive Care, 2017, vol. 5, pp. 27. https://doi.org/10.1186/s40560-017-0222-0.

24. Papagiannakis N., Ragias D., Ntalarizou N. et al. Transitions from aerobic to anaerobic metabolism and oxygen debt during surgery. Biomedicines, 2024, vol. 12, no. 8, pp. 1754. https://doi.org/10.3390/biomedicines12081754.

25. Parolari A., Alamanni F., Juliano G. et al. Oxygen metabolism during and after cardiac surgery. Annals of Thoracic Surgery, 2003, vol. 76, no. 3, pp. 737–743. https://doi.org/10.1016/S0003-4975(03)00683-0.

26. Rousing M. L., Hahn-Pedersen M. H., Andreassen S. et al. Energy expenditure estimation by indirect calorimetry. Annals of Intensive Care, 2016, vol. 6, no. 1, pp. 16. https://doi.org/10.1186/s13613-016-0118-8.

27. Sessler D. I. Perioperative thermoregulation and heat balance. The Lancet, 2016, vol. 387, no. 10038, pp. 2655–2664. https://doi.org/10.1016/S0140-6736(15)00981-2.

28. Shoemaker W. C., Appel P. L., Kram H. B. Oxygen transport measurements to evaluate tissue perfusion. Critical Care Medicine, 1991, vol. 19, no. 5, pp. 672–688. https://doi.org/10.1097/00003246-199105000-00014.

29. Singer P., Reintam Blaser A., Berger M. M. et al. ESPEN practical guideline: clinical nutrition in the ICU. Clinical Nutrition, 2023, vol. 42, no. 9, pp. 1671–1689. https://doi.org/10.1016/j.clnu.2023.07.011.

30. Stanley W. C., Chandler M. P. Energy metabolism in the normal and failing heart. Heart Failure Reviews, 2002, vol. 7, no. 2, pp. 115–130. https://doi.org/10.1023/A:1015307803864

31. Stock M. C., Ryan M. E. Oxygen consumption calculated from the Fick equation has limited utility. Critical Care Medicine, 1996, vol. 24, no. 1, pp. 86–90. https://doi.org/10.1097/00003246-199601000-00015.

32. Teboul J. L., Saugel B., Cecconi M. et al. Less invasive hemodynamic monitoring. Intensive Care Medicine, 2016, vol. 42, no. 9, pp. 1350–1359. https://doi.org/10.1007/s00134-016-4375-7.

33. Terao Y., Miura K., Saito M. et al. Sedation and resting energy expenditure. Critical Care Medicine, 2003, vol. 31, no. 3, pp. 830–833. https://doi.org/10.1097/01.CCM.0000054868.93459.E1.

34. Uber A., Grossestreuer A. V., Ross C. E. et al. Systemic oxygen consumption after cardiac arrest. Resuscitation, 2018, vol. 127, pp. 89–94. https://doi.org/10.1016/j.resuscitation.2018.04.001.

35. Wan S., LeClerc J. L., Vincent J. L. Inflammatory response to cardiopulmonary bypass. Chest, 1997, vol. 112, no. 3, pp. 676–692. https://doi.org/10.1378/chest.112.3.676.

36. Weissman C. The metabolic response to stress: an overview and update. Anesthesiology, 1990, vol. 73, no. 2, pp. 308–327. https://doi.org/10.1097/00000542-199008000-00020.

37. Zilla P., Yacoub M., Zühlke L. et al. Global unmet needs in cardiac surgery. Global Heart, 2018, vol. 13, no. 4, pp. 293–303. https://doi.org/10.1016/j.gheart.2018.08.002.