Evaluation of a lithium dilution cardiac output technique as a method for measurement of cardiac output in anesthetized cats

Abstract

Objective - To evaluate the use of a lithium dilution cardiac output (LiDCO) technique for measurement of CO and determine the agreement between LiDCO and thermodilution CO (TDCO) values in anesthetized cats. Animals - 6 mature cats. Procedure - Cardiac output in isoflurane-anesthetized cats was measured via each technique. To induce different rates of CO in each cat, anesthesia was maintained at > 1.5X end-tidal minimum alveolar concentration (MAC) of isoflurane and at 1.3X end-tidal isoflurane MAC with or without administration of dobutamine (1 to 3 μg/kg/min, IV). At least 2 comparisons between LiDCO and TDCO values were made at each CO rate. The TDCO indicator was 1.5 mL of 5% dextrose at room temperature; with the LiDCO technique, each cat received 0.005 mmol of lithium/kg (concentration, 0.015 mmol/mL). Serum lithium concentrations were measured prior to the first and following the last CO determination. Results - 35 of 47 recorded comparisons were analyzed; via linear regression analysis (LiDCO vs TDCO values), the coefficient of determination was 0.91. The mean bias (TDCO-LiDCO) was -4 mL/kg/min (limits of agreement, -35.8 to + 272 mL/kg/min). The concordance coefficient was 0.94. After the last CO determination, serum lithium concentration was < 0.1 mmol/L in each cat. Conclusions and clinical relevance - Results indicated a strong relationship and good agreement between LiDCO and TDCO values; the LiDCO method appears to be a practical, relatively noninvasive method for measurement of CO in anesthetized cats.