Bioreactance noninvasive cardiac output monitoring in euvolemic adult horses subjected with 7.2% saline and 6% hydroxyethyl starch (130/0.4) solution infusions.

Objective: To compare the ability of bioreactance noninvasive cardiac output (BR-NICO) with thermodilution cardiac output (TDCO) for the measurement of cardiac output (CO) in healthy adult horses receiving 2 different IV volume replacement solutions.

Design: Prospective randomized crossover study from September to November 2021.

Setting: University teaching hospital.

Animals: Six university-owned adult horses.

Interventions: Horses were randomly assigned to receive 7.2% hypertonic saline solution (HSS) or 6% hydroxyethyl starch (130/0.4) solution (HETA). BR-NICO and TDCO were measured simultaneously at baseline, 10, 20, 30, 40, 50, 60, 90, and 120 minutes before fluid administration and again at the same times after starting a bolus infusion of IV volume replacers. All solutions were administered within 10 minutes.

Measurements And Main Results: BR-NICO and TDCO were strongly correlated (Pearson r = 0.93; P < 0.01). Regression analysis showed the relationship between TDCO and BR-NICO was BR-NICO = 0.48 × TDCO + 0.6. For the corrected BR-NICO values, the Bland-Altman agreement mean bias and lower/upper limits of agreement were -0.62 and -5.3 to 3.9 L/min, respectively. Lin's concordance (95% confidence interval) between methods was 0.894 (0.825-1.097). Compared with baseline, HSS increased the CO at 10 and 20 minutes (TDCO and BR-NICO). Compared with baseline, HETA decreased the CO at 10 and 20 minutes (TDCO and BR-NICO) and increased the CO at 90 (TDCO only) and 120 minutes (TDCO and BR-NICO).

Conclusions: BR-NICO strongly agreed with TDCO in the measurement of CO in healthy unsedated adult horses. HSS administration significantly increased CO in the first 30 minutes, while HETA initially decreased CO at 10 minutes but increased CO to above baseline values by 90 minutes.