Clinical monitoring of cardiac output assessed by transoesophageal echocardiography in anaesthetised dogs: a comparison with the thermodilution technique.

Abstract

BACKGROUND: Cardiac output (CO) is an important haemodynamic parameter to monitor in patients during surgery. However, the majority of the techniques for measuring CO have a limited application in veterinary practice due to their invasive approach and associated complexity and risks. Transoesophageal echocardiography (TEE) is a technique used to monitor cardiac function in human patients during surgical procedures and allows CO to be measured non-invasively. This prospective clinical study aimed to compare the transoesophageal echocardiography using a transgastric view of the left ventricular outflow tract (LVOT) and the thermodilution (TD) technique for the assessment of CO during mean arterial pressure of 65-80&#xa0;mmHg (normotension) and <65&#xa0;mmHg (hypotension) in dogs undergoing elective surgery. Eight dogs were pre-medicated with acepromazine (0.05&#xa0;mg/kg, IM), tramadol (4&#xa0;mg/kg, IM) and atropine (0.03&#xa0;mg/kg, IM), followed by anaesthetic induction with propofol (3-5&#xa0;mg/kg IV) and maintenance with isoflurane associated with a continuous infusion rate of fentanyl (bolus of 3 &#x3bc;g/kg followed by 0.3&#xa0;&#x3bc;g/kg/min). The CO was measured by TEE (CO) and TD (CO) at the end of expiration during normotension and hypotension (induced by isoflurane). RESULTS: There was a strong positive correlation between COand CO&#x200b;&#x200b;(r&#xa0;=&#xa0;0.925; P&#xa0;<&#xa0;0.0001). The bias between COand COwas 0.14&#xa0;&#xb1;&#xa0;0.29&#xa0;L/min (limits of agreement, -0.44 to 0.72&#xa0;L/min). The percentage error of CO measured by the two methods was 12.32%. In addition, a strong positive correlation was found between COand COduring normotension (r&#xa0;=&#xa0;0.995; P&#xa0;<&#xa0;0.0001) and hypotension (r&#xa0;=&#xa0;0.78; P&#xa0;=&#xa0;0.0223). CONCLUSIONS: The results of this study indicated that the transgastric view of the LVOT by TEE was a minimally invasive alternative to clinically monitoring CO in dogs during anaesthesia. However, during hypotension, the CO obtained by TEE was less reliable, although still acceptable.