A retrospective study of the isoflurane-sparing and cardiovascular effects of combined remifentanil-ketamine infusions with and without lidocaine in cats.

OBJECTIVE

This retrospective study aimed to evaluate the intraoperative isoflurane-sparing and cardiovascular effects of a combined infusion of remifentanil-lidocaine-ketamine versus remifentanil-ketamine for balanced anaesthesia in cats to investigate the effect of lidocaine infusion in various clinical situations.

MATERIALS AND

METHODS

Among patients with various health statuses undergoing surgical procedures, 18 cats administered remifentanil-lidocaine-ketamine were compared with 20 cats administered remifentanil-ketamine. In the remifentanil-lidocaine-ketamine group, lidocaine was initially infused at 50 μg/kg/minute with a loading dose of 0.6 mg/kg, and the infusion rate was controlled depending on cardiovascular alterations. Linear regression was used to relate end-tidal isoflurane and cardiovascular effects, including blood pressure [expressed as the ratio of mild hypotension duration (mean arterial pressure <60 mmHg) to total anaesthesia time] and heart rate (interquartile range) with patient, surgical and anaesthetic variables including lidocaine infusion.

RESULTS

In the remifentanil-lidocaine-ketamine group, the average lidocaine infusion rate during the entire anaesthetic period was 46.00 ± 12.00 (range: 22.67 to 64.63) μg/kg/minute. The multivariable regression model of end-tidal isoflurane showed a correlation with the duration of the procedure and lidocaine infusion. The end-tidal isoflurane concentration exhibited a significant reduction in the remifentanil-lidocaine-ketamine group (1.16% ± 0.19%), compared with that of the remifentanil-ketamine group (1.27% ± 0.14%). The association between lidocaine administration and hypotension was not significant, nor was that with heart rate.

CLINICAL SIGNIFICANCE: Although the use of intravenous lidocaine in cats has been associated with concerns regarding cardiovascular toxicity, the findings of this study suggest that lidocaine infusion, as part of the remifentanil-lidocaine-ketamine combination, can be considered a component of balanced anaesthesia in cats.