Cardiac output during total hip replacement in dogs

Trans-oesophageal pulsed-wave Doppler echocardiography was evaluated as a n oninvasive method of determining cardiac output during total hip replacemen t in 10 dogs. Cardiac output was estimated by determining the cross-section al area of the aorta via caudal transverse echocardiography and the outflow velocity of the ascending aorta via cranial transverse Doppler echocardiog raphy. Thermodilution was used as the reference method. In addition, cardio pulmonary changes, at the time of femoral prosthesis insertion, were determ ined. Comparison of 160 measurements yielded a correlation coefficient of 0 .48. Linear regression analysis revealed the equation, cardiac output (Dopp ler echocardiography) = 0.45 cardiac output (thermodilution) + 3.3. In comp arison to thermodilution, trans-oesophageal pulsed-wave Doppler echocardiog raphy overestimated cardiac output at flow rates less than 61/min and under estimated the cardiac output at flow rates greater than 61/min. There was a significant decrease in the partial pressure of carbon dioxide at end-expi ration (PETCO2), the systolic arterial blood pressure (mmHg) and the invasi ve stroke volume (ml/beat/m(2)) and a significant increase in the pulmonary vascular resistance (dynes/sec/cm(5)) immediately after insertion of the f emoral prosthesis.