Cardiac Output Measurement in Ventilated Lambs with a Significant Left-to-Right Shunt Using the Modified Carbon Dioxide Fick Method

Abstract

Background: It remains a great challenge to measure systemic blood flow in critically ill newborns. In a former study we validated the modified carbon dioxide Fick (mCO₂F) method for measurement of cardiac output in a newborn lamb model. In this new study we studied the influence of a left-to-right shunt on the accuracy of the mCO₂F method. Objective: To analyze the influence of a left-to-right shunt on the agreement between cardiac output measurement with the mCO₂F method and ultrasonic transit time pulmonary blood flow in a lamb model. Methods: The study was approved by the Ethical Committee on Animal Research of the Radboud University Nijmegen and performed in 8 random-bred lambs. A Gore-Tex® shunt was placed between the left pulmonary artery and the descending aorta. This aortopulmonary shunt was intermittently opened and closed, while cardiac output was manipulated by creating hemorrhagic hypotension. Cardiac output measurement with the mCO₂F method (Q^mCO2F) was compared with pulmonary blood flow obtained by a transit time ultrasonic flow probe positioned around the common pulmonary artery (Q^APC). Results: Bias, defined as Q^mCO2F – Q^APC, was calculated for each measurement. With an open shunt there was a significant left-to-right shunt (mean Qp/Qs ratio 2.26; range 1.56–3.69). Mean bias (SD) was –12.3 (50.4) ml·kg^–1·min^–1 and –12.3 (42.7) ml·kg^–1·min^–1 for measurements with a closed and open shunt, respectively (no statistical significant difference). Conclusions: Cardiac output measurement with the mCO₂F method is reliable and easily applicable in ventilated newborn lambs, also in the presence of a significant left-to-right shunt.

Advanced Hemodynamic Monitoring in Critically Ill Children

“…However, the transpulmonary thermodilution technology and the modified CO 2 Fick methods might be feasible in this situation. 29,30 Nonetheless, in adults there is no evidence that the use of a pulmonary artery catheter improves morbidity and/or mortality rates. 31 However, fluid therapy guided by CO measurement using esophageal Doppler might improve outcome after major adult surgery but not in critically ill patients.…”

Cardiac output measurement with transpulmonary ultrasound dilution is feasible in the presence of a left-to-right shunt: a validation study in lambs

“…Many of the other current CO measurement techniques have not been validated in patients with shunts, 13 -15 with the exception of the modified carbon dioxide Fick method. 16 Transpulmonary ultrasound dilution (TPUD) was introduced in 1995 to enable measurement of several haemodynamic parameters in patients during haemodialysis. 17 18 The technique was adapted for CO measurements and tested in vitro, 19 in animals, 20 -22 adults, 23 -25 and children, 26 27 using isotonic saline at body temperature as an indicator, that is injected in a low-volume extracorporeal arterio-venous (AV) tubing loop inserted between an indwelling arterial and central venous catheter.…”

Impact of intravenous fluid administration on cardiac output and oxygenation during cardiopulmonary resuscitation

“…The COstatus CO monitor (Transonic Systems, Ithaca, NY USA) was used to measure CO via ultrasound dilution technology and has been validated for measurement of CO in both human and pig subjects when compared with the gold standard of thermodilution [10][11][12][13][14]. Baseline measurements of CO, blood pressure, and heart rate were obtained.…”