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  • Author or Editor: L. Chris Sanchez x
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Objective—To compare cardiac output (CO) measured by use of the partial carbon dioxide rebreathing method (NICO) or lithium dilution method (LiDCO) in anesthetized foals.

Sample Population—Data reported in 2 other studies for 18 neonatal foals that weighed 32 to 61 kg.

Procedures—Foals were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, end-tidal isoflurane and carbon dioxide concentrations, and CO. Various COs were achieved by administration of dobutamine, norepinephrine, vasopressin, phenylephrine, and isoflurane to allow comparisons between LiDCO and NICO methods. Measurements were obtained in duplicate or triplicate. We allowed 2 minutes between measurements for LiDCO and 3 minutes for NICO after achieving a stable hemodynamic plane for at least 10 to 15 minutes at each CO.

Results—217 comparisons were made. Correlation (r = 0.77) was good between the 2 methods for all determinations. Mean ± SD measurements of cardiac index for all comparisons with the LiDCO and NICO methods were 138 ± 62 mL/kg/min (range, 40 to 381 mL/kg/min) and 154 ± 55 mL/kg/min (range, 54 to 358 mL/kg/min), respectively. Mean difference (bias) between LiDCO and NICO measurements was −17.3 mL/kg/min with a precision (1.96 × SD) of 114 mL/kg/min (range, −131.3 to 96.7). Mean of the differences of LiDCO and NICO measurements was 4.37 + (0.87 × NICO value).

Conclusions and Clinical Relevance—The NICO method is a viable, noninvasive method for determination of CO in neonatal foals with normal respiratory function. It compares well with the more invasive LiDCO method.

Full access
in American Journal of Veterinary Research


Objective—To determine the effects of dobutamine, norepinephrine, and vasopressin on cardiovascular function and gastric mucosal perfusion in anesthetized foals during isoflurane-induced hypotension.

Animals—6 foals that were 1 to 5 days of age.

Procedures—6 foals received 3 vasoactive drugs with at least 24 hours between treatments. Treatments consisted of dobutamine (4 and 8 μg/kg/min), norepinephrine (0.3 and 1.0 μg/kg/min), and vasopressin (0.3 and 1.0 mU/kg/min) administered IV. Foals were maintained at a steady hypotensive state induced by a deep level of isoflurane anesthesia for 30 minutes, and baseline cardiorespiratory variables were recorded. Vasoactive drugs were administered at the low infusion rate for 15 minutes, and cardiorespiratory variables were recorded. Drugs were then administered at the high infusion rate for 15 minutes, and cardiorespiratory variables were recorded a third time. Gastric mucosal perfusion was measured by tonometry at the same time points.

Results—Dobutamine and norepinephrine administration improved cardiac index. Vascular resistance was increased by norepinephrine and vasopressin administration but decreased by dobutamine at the high infusion rate. Blood pressure was increased by all treatments but was significantly higher during the high infusion rate of norepinephrine. Oxygen delivery was significantly increased by norepinephrine and dobutamine administration; O2 consumption decreased with dobutamine. The O2 extraction ratio was decreased following norepinephrine and dobutamine treatments. The gastric to arterial CO2gap was significantly increased during administration of vasopressin at the high infusion rate.

Conclusion and Clinical Relevance—Norepinephrine and dobutamine are better alternatives than vasopressin for restoring cardiovascular function and maintaining splanchnic circulation during isofluraneinduced hypotension in neonatal foals.

Full access
in American Journal of Veterinary Research