Concordância entre a termodiluição transpulmonar e a termodiluição pulmonar para mensuração do débito cardíaco em cães anestesiados com isofluorano

Cardiac output monitoring by transpulmonary thermodilution (COTP) is a less invasive alternative compared to cardiac output derived from pulmonary thermodilution (COP). This study aimed to determine agreement between COP and COTP using two volumes of thermal indicator in dogs. The COP and COTP were measured in eight adult isoflurane-anesthetized dogs (25 ± 3.6 kg) via thermodilution catheters positioned in the pulmonary and femoral arteries, respectively. Cardiac output was assessed during normodynamic (isoflurane: 1.5 MAC), hypodynamic (remifentanil: 0.3 and 0.6 μg/kg/min, IV) and hyperdynamic (dobutamine: 2.5 and 5.0 μg/kg/min, IV) states. Drug infusion rates and end-tidal isoflurane concentrations were held constant for 15 minutes prior to three simultaneous measurements of COP and COTP, using 5 and 10 mL of ice-cold saline (< 6°C) during stable hemodynamic conditions (defined as HR and MBP recorded at the beginning and end of each series of measurements differing by less than 10%). A Bland-Altman analysis for multiple measurements per subject was performed (positive bias: overestimation of COP). Maximum percentage error (2 x SD of bias between methods / average COP x 100) was predefined as < 30% for acceptance of COTP. Maximum and minimum values of COP were 5.67 ± 0.52 and 1.88 ± 0.25 L/min, respectively. Mean bias, (limits of agreement: ± 1.96 SD), and the percentage error were 0.62 (-0.11/1.35) L/min and 22% for 5 mL and 0.33 (-0.25/0.91) L/min and 18% for 10 mL of thermal indicator. The COTP tended to overestimate COP. Although the agreement with the reference method was acceptable for both volumes of thermal signal, the 10 mL injectate volume could be advantageous for COTP measurements because its percentage error was smaller.