Capnodynamic Cardiac Output (Dynamic capngraphy)

Cardiac output monitoring is gaining increased importance in pediatric anesthesia and intensive care.(1) Karlsson et al (2) investigated effective pulmonary blood flow (CO_EPBG) technique in pediatric surgical patients, compared with suprasternal two-dimensional Doppler (CO_SSD). CO_EPBF was measured continuously using the differential Fick’s principle.  The method is based on the differential Fick principle and utilizes the molar balance for pulmonary carbon dioxide exchange. A total of 15 children undergoing cleft lip/palate surgery were investigated. Before the start of surgery, maneuvers that were anticipated to reduce (increase in PEEP from 3 to 10 cm H₂O) and increase (atropine) CO were undertaken. A study in mechanically ventilated piglets was also undertaken under general anesthesia, measuring CO_EPBF and pulmonary artery (CO_TS) flow by ultrasonic probe as the comparator. Bias (Bland−Altman plots) and limits of agreement were assessed for effective pulmonary blood flow and CO_SSD or CO_TS. In pediatric patients (median age 8.5 months), overall bias was −8.1 (limits of agreement −82 to +66) ml kg⁻¹ min⁻¹, with a mean percentage error of 48% and a concordance rate of 64%. In the piglet model, overall bias was −1 (−36 to +38) ml kg⁻¹ min⁻¹, with a mean percentage error of 31% and a concordance rate of 95%.  The authors concluded that under controlled experimental conditions, CO_EPBF is associated with excellent agreement and good trending ability when compared with the gold standard CO_TS. In the pediatric clinical setting, CO_EPBF performs well; by contrast, CO_SSD, an operator- and anatomy-dependent technology, appears less reliable than CO_EPBF.

In another study, Karlsson et al (3) used capnodynamic cardiac output to esophageal Doppler cardiac output (CO_EDM). Cardiac output changes were caused by the manipulation of PEEP. CO_EDM was unable to detect the reduction of CO caused by increased PEEP, whereas CO_EPBF and to a minimal extent, NIBP detected these changes in CO. The ability of CO_EPBF to react to minor reductions in CO, before noticeable changes in NIBP are seen, suggests that CO_EPBF may be a potentially useful tool for hemodynamic monitoring in mechanically ventilated children. (Anesth Analg 2022;134:644–52).

1. Singh Y, Villaescusa JU, da Cruz EM, et al. Recommendations for hemodynamic monitoring for critically ill children-expert consensus statement issued by the cardiovascular dynamics section of the European Society of Paediatric and Neonatal Intensive Care (ESPNIC). Crit Care. 2020;24:620.

2. Karlsson J, Winberg P, Scarr B, et al. Validation of capnodynamic determination of cardiac output by measuring effective pulmonary blood flow: a study in anesthetized children and piglets. Br J Anaesth. 2018;121:550–558.

3. Karlsson et al. Cardiac Output Assessments in Anesthetized Children: Dynamic Capnography Versus Esophageal Doppler. Anesth Analg 2022;134:644–5.