A Continuous Noninvasive Method to Assess Mixed Venous Oxygen Saturation: A Proof-of-Concept Study in Pigs. (June 2021)

• Record Type: Journal Article
• Authors: Karlsson, Jacob; Lönnqvist, Per-Arne; Wallin, Mats; Hallbäck, Magnus
• Is Part Of: Anesthesia & analgesia. Volume 132:Number 6(2021)
• Publication Date: 2021-06
• Subjects: Anesthesiology -- Periodicals; Anesthesia; Anesthesiology; Analgesia; Analgesics; Anesthesiology -- Periodicals; 617.9605
• DOI: 10.1213/ANE.0000000000005188
• Languages: English
• ISSNs: 0003-2999

Abstract

Abstract : BACKGROUND: Mixed venous oxygen saturation (SvO2 ) is important when evaluating the balance between oxygen delivery and whole-body oxygen consumption. Monitoring SvO2 has so far required blood samples from a pulmonary artery catheter. By combining volumetric capnography, for measurement of effective pulmonary blood flow, with the Fick principle for oxygen consumption, we have developed a continuous noninvasive method, capnodynamic SvO2, for assessment of SvO2 . The objective of this study was to validate this new technique against the gold standard cardiac output (CO)-oximetry SvO2 measurement of blood samples obtained from a pulmonary artery catheter and to assess the potential influence of intrapulmonary shunting. METHODS: Eight anesthetized mechanically ventilated domestic-breed piglets of both sexes (median weight 23.9 kg) were exposed to a series of interventions intended to reduce as well as increase SvO2 . Simultaneous recordings of capnodynamic and CO-oximetry SvO2 as well as shunt fraction, using the Berggren formula, were performed throughout the protocol. Agreement of absolute values for capnodynamic and CO-oximetry SvO2 and the ability for capnodynamic SvO2 to detect change were assessed using Bland-Altman plot and concordance analysis. RESULTS: Overall bias for capnodynamic versus CO-oximetry SvO2 was −1 percentage point (limits of agreement −13 to +11 percentage points), a mean percentage error of 22%, and a concordance rate of 100%. Shunt fraction varied between 13% at baseline and 22% at the end of the study and was associated with only minor alterations in agreement between the tested methods. CONCLUSIONS: In the current experimental setting, capnodynamic assessment of SvO2 generates absolute values very close to the reference method CO-oximetry and is associated with 100% trending ability.