Influence of calcium chloride on the cardio–respiratory effects of a bolus of enoximone in isoflurane anaesthetized ponies

Obejctive To investigate the influence of calcium chloride (CaCl 2 ) on the cardio–respiratory effects of enoximone in isoflurane anaesthetized ponies. Study design Prospective consecutive experimental trial. Animals Six healthy ponies, weighing 287 ± 55 kg were included in this study. Methods After sedation (romifidine, 80 μg kg −1 ), anaesthesia was induced with midazolam (0.06 mg kg −1 ) and ketamine (2.2 mg kg −1 ) and maintained with isoflurane in oxygen. The ponies’ lungs were ventilated to maintain normocapnia. After 90 minutes, a bolus of enoximone (0.5 mg kg −1 ) was administered, followed by a CaCl 2 infusion (0.5 mg kg −1 minute −1 over 10 minutes) (treatment EC). Sodium, potassium, ionized and total calcium concentrations, cardiovascular variables and blood–gases were measured in the 120 minutes after treatment. Using a mixed model anova , the results were compared to those of a previous report [ Vet Anaesth Analg , 34 (2007) 416], evaluating the effects of 0.5 mg kg −1 enoximone in the same ponies and under identical circumstances (treatment E). Both an overall comparison and comparisons at specific time points after treatment were performed (α = 0.05). Results Although ionized and total calcium concentrations were higher during treatment EC, the cardio–respiratory effects of enoximone were comparable for both treatments. A small but significant difference in packed cell volume was detected. Conclusions and clinical relevance Calcium chloride did not enhance the effects of enoximone in normocalcaemic anaesthetized ponies.