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Schmidt MT, Studer M, Kunz A, Studer S, Bonvini JM, Bueter M, Kook L, Haile SR, Pregernig A, Beck-Schimmer B, Schläpfer M. There is no evidence that carbon dioxide-enriched oxygen before apnea affects the time to arterial desaturation, but it might improve cerebral oxygenation in anesthetized obese patients: a single-blinded randomized crossover trial. BMC Anesthesiol 2023; 23:41. [PMID: 36747148 PMCID: PMC9900199 DOI: 10.1186/s12871-023-01982-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 01/09/2023] [Indexed: 02/08/2023] Open
Abstract
PURPOSE Carbon dioxide (CO2) increases cerebral perfusion. The effect of CO2 on apnea tolerance, such as after anesthesia induction, is unknown. This study aimed to assess if cerebral apnea tolerance can be improved in obese patients under general anesthesia when comparing O2/Air (95%O2) to O2/CO2 (95%O2/5%CO2). METHODS In this single-center, single-blinded, randomized crossover trial, 30 patients 18-65 years, with body mass index > 35 kg/m2, requiring general anesthesia for bariatric surgery, underwent two apneas that were preceded by ventilation with either O2/Air or O2/CO2 in random order. After anesthesia induction, intubation, and ventilation with O2/Air or O2/CO2 for 10 min, apnea was performed until the cerebral tissue oxygenation index (TOI) dropped by a relative 20% from baseline (primary endpoint) or oxygen saturation (SpO2) reached 80% (safety abortion criterion). The intervention was then repeated with the second substance. RESULTS The safety criterion was reached in all patients before cerebral TOI decreased by 20%. The time until SpO2 dropped to 80% was similar in the two groups (+ 6 s with O2/CO2, 95%CI -7 to 19 s, p = 0.37). Cerebral TOI and PaO2 were higher after O2/CO2 (+ 1.5%; 95%CI: from 0.3 to 2.6; p = 0.02 and + 0.6 kPa; 95%CI: 0.1 to 1.1; p = 0.02). CONCLUSION O2/CO2 improves cerebral TOI and PaO2 in anesthetized bariatric patients. Better apnea tolerance could not be confirmed.
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Affiliation(s)
- Marc T. Schmidt
- grid.412004.30000 0004 0478 9977Institute of Anesthesiology, University Hospital Zurich, Zurich, Switzerland
| | | | | | - Sandro Studer
- grid.412004.30000 0004 0478 9977Clinical Trials Center, University Hospital Zurich, Zurich, Switzerland
| | - John M. Bonvini
- grid.412004.30000 0004 0478 9977Institute of Anesthesiology, University Hospital Zurich, Zurich, Switzerland
| | - Marco Bueter
- grid.412004.30000 0004 0478 9977Department of Surgery, University Hospital Zurich, Zurich, Switzerland
| | - Lucas Kook
- grid.7400.30000 0004 1937 0650Epidemiology, Biostatistics and Prevention Institute, University Zurich, Zurich, Switzerland
| | - Sarah R. Haile
- grid.7400.30000 0004 1937 0650Epidemiology, Biostatistics and Prevention Institute, University Zurich, Zurich, Switzerland
| | - Andreas Pregernig
- grid.412004.30000 0004 0478 9977Institute of Anesthesiology, University Hospital Zurich, Zurich, Switzerland
| | - Beatrice Beck-Schimmer
- grid.412004.30000 0004 0478 9977Institute of Anesthesiology, University Hospital Zurich, Zurich, Switzerland ,grid.185648.60000 0001 2175 0319Department of Anesthesiology, University of Illinois at Chicago, Chicago, USA ,grid.7400.30000 0004 1937 0650Institute of Physiology, Zurich Center for Integrative Human Physiology, University Zurich Irchel, Zurich, Switzerland
| | - Martin Schläpfer
- Institute of Anesthesiology, University Hospital Zurich, Zurich, Switzerland. .,Institute of Physiology, Zurich Center for Integrative Human Physiology, University Zurich Irchel, Zurich, Switzerland.
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Domogo AA, Ottesen JT. Patient-specific parameter estimation: Coupling a heart model and experimental data. J Theor Biol 2021; 526:110791. [PMID: 34087267 DOI: 10.1016/j.jtbi.2021.110791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 05/01/2021] [Accepted: 05/28/2021] [Indexed: 10/21/2022]
Abstract
This study develops a hemodynamic model involving the atrium, ventricle, veins, and arteries that can be calibrated to experimental results. It is a Windkessel model that incorporates an unsteady Bernoulli effect in the blood flow to the atrium. The model is represented by ordinary differential equations in terms of blood volumes in the compartments as state variables and it demonstrates the use of conductance instead of resistance to capture the effect of a non-leaking heart valve. The experimental results are blood volume data from 20 young (half of which are women) and 20 elderly (half of which are women) subjects during rest, inotropic stress (dobutamine), and chronotropic stress (glycopyrrolate). The model is calibrated to conform with data and physiological findings in 4 different levels. First, an optimization routine is devised to find model parameter values that give good fit between the model volume curves and blood volume data in the atrium and ventricle. Patient-specific information are used to get initial parameter values as a starting point of the optimization. Also, model pressure curves must show realistic behavior. Second, parametric bootstrapping is performed to establish the reliability of the optimal parameters. Third, statistical tests comparing mean optimal parameter values from young vs elderly subjects and women vs men are examined to support and present age and sex related differences in heart functions. Lastly, statistical tests comparing mean optimal parameter values from resting condition vs pharmacological stress are studied to verify and quantify the effects of dobutamine and glycopyrrolate to the cardiovascular system.
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Affiliation(s)
- Andrei A Domogo
- University of the Philippines Baguio, Baguio City, Philippines; Roskilde University, Roskilde, Denmark.
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