Cardiopulmonary effects of dorsal recumbency and high-volume caudal epidural anaesthesia with lidocaine or xylazine in calves

The objective of this study was to investigate the cardiopulmonary effects of dorsal recumbency and high-volume caudal epidural anaesthesia induced by xylazine or lidocaine in calves. Twenty-eight German Holstein–Friesian calves (57.7 ± 5.8 kg bodyweight) were randomly allocated to four equal (n = 7) groups for one of the following treatments, each injected into the caudal epidural space: (1) no treatment (control); (2) sterile saline (0.4 mL/kg); (3) lidocaine (2%), or (4) xylazine (0.1 mg/kg), with the latter two treatments diluted with sterile saline to a final volume of 0.4 mL/kg. Cardiac output was measured by thermodilution and cardiopulmonary function parameters were determined at preset time intervals over an observation period of 335 min. After baseline measurements in the standing animals, the calves received the epidural injection and were positioned in dorsal recumbency for 95 min. control group, dorsal recumbency caused a significant (P < 0.05) decrease in cardiac index (CI) (baseline 210 ± 12 mL/kg/min, minimum value 174 ± 11 mL/kg/min), without significant change in blood-gas values. Calves treated with lidocaine or saline did not differ from the control group in any of the parameters measured. The epidural injection of xylazine caused a more pronounced decrease in CI (baseline 209 ± 12 mL/kg/min, minimum value 127 ± 11 mL/kg/min), compared to the control group. At the same time, the heart rate was significantly (P < 0.05) decreased (baseline 113 ± 7 beats per min, minimum value 86 ± 4 beats per min). Furthermore, a significant (P < 0.05) increase in the oxygen extraction ratio was observed in the xylazine group (baseline 39 ± 7%, maximum value 47 ± 7%). In all groups, cardiorespiratory parameters remained within physiological limits. Changes in cardiopulmonary function induced by dorsal recumbency and high-volume caudal epidural anaesthesia with lidocaine or xylazine were well tolerated in healthy calves.