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

To investigate the influence of calcium chloride (CaCl2) on the cardio-respiratory effects of enoximone in isoflurane anaesthetized ponies. Prospective consecutive experimental trial. Six healthy ponies, weighing 287 +/- 55 kg were included in this study. After sedation (romifidine, 80 mu g 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 CaCl2 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 (alpha = 0.05). 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. Calcium chloride did not enhance the effects of enoximone in normocalcaemic anaesthetized ponies.