Agreement between Electrical Cardiometry and Pulmonary Artery Thermodilution for Measuring Cardiac Output in Isoflurane-Anesthetized Dogs

Simple Summary Using general anesthesia on animals causes significant changes to the heart and blood vessels that disrupt normal cardiovascular performance. Blood pressure (BP) is used for closely monitoring hemodynamics in anesthetized animals. However, BP is affected by various factors and may not always accurately correlate with the total body blood flow. Pulmonary artery thermodilution (PATD) is the gold standard for cardiac output (CO) measurements, but, due to the high risks associated with its invasiveness, it is not performed in clinical settings. This study evaluates noninvasive electrical cardiometry's (EC) performance in measuring CO and other hemodynamic variables in healthy anesthetized dogs during acute blood volume manipulation. The EC measurements consistently underpredict the CO values as compared with PATD, but have a better performance when acute blood loss occurs. Even though the EC readings have a slightly higher error than the accepted error, this method is very good at showing trends in the CO measured using PATD. Other EC-derived variables are able to closely track the changes in the CO measured using PATD. In clinics, noninvasive EC may benefit the patient care quality for anesthetized dogs by monitoring the trends in hemodynamics and guiding anesthetists to diagnose and treat cardiovascular complications. In animals, invasive pulmonary artery thermodilution (PATD) is a gold standard for cardiac output (CO) monitoring, but it is impractical in clinical settings. This study evaluates the agreement between PATD and noninvasive electrical cardiometry (EC) for measuring CO and analyzes the other EC-derived hemodynamic variables in six healthy anesthetized dogs subjected to four different hemodynamic events in a sequential order: (1) euvolemia (baseline); (2) hemorrhage (33% blood volume loss); (3) autologous blood transfusion; and (4) 20 mL/kg colloid bolus. The CO measurements obtained using PATD and EC are compared using Bland-Altman analysis, Lin's concordance correlation (LCC), and polar plot analysis. Values of p < 0.05 are considered significant. The EC measurements consistently underpredict the CO values as compared with PATD, and the LCC is 0.65. The EC's performance is better during hemorrhage, thus indicating its capability in detecting absolute hypovolemia in clinical settings. Even though the percentage error exhibited by EC is 49.4%, which is higher than the standard (<30%), EC displays a good trending ability. Additionally, the EC-derived variables display a significant correlation with the CO measured using PATD. Noninvasive EC may have a potential in monitoring trends in hemodynamics in clinical settings.