Introduction Administration of dobutamine can be used as pharmacological stress testing in echocardiography like a substitute of exercise stress testing. The aim of the study was to investigate by echocardiography the effects of different dosages of dobutamine on heart activity in anaesthetized horses. Materials and Methods Six healthy trotter female horses aged 8±1.5 years old and weighted 468±24 kg were used. Each horse was premedicated with acepromazine (0.03 mg/kg). Twenty minutes later, xylazine 0.5 mg/kg was administered. After ten minutes general anaesthesia was induced with ketamine (2.2 mg/kg) and diazepam (0.1 mg/kg) and maintained with isoflurane and oxygen. Horses were placed on operating table in left recumbency. No surgical procedure was carried out. Echocardiography was performed before (T0) dobutamin infusion, at 2.5 μg/kg/min (T1), 5.0 μg/kg/min (T2), and 7.5 μg/kg/min (T3) dosages. The lower dosage was started 15’ after induction of anaesthesia, then each dosage was infused IV for 15’. Registration of the different parameters of echocardiography and of the mean artery pressure (MAP) was made at the end of each infusion time. Interventricular septal dimension (IVS), left ventricular internal diameter (LVID), left ventricular volume (LVVol), stroke volume (SV), ejection fraction (EF) and cardiac output (CO) were recorded both in systole (s) and diastole (d). A one-way analysis of variance for repeated measures and a Tukey posthoc test were used to compare the effect of treatment between basal condition and the 3 different dosages. Significance was P < .05. Results Two/6 (33%) horses developed supraventricular tachycardia (HR>60 bm) at T2, 5/6 (83%) showed HR>60 bm at T3 and 1/5 (20%) developed ventricular extrasystole. The measures were reported in average±standard deviation. Significative differences were found for IVSs, LVVols (T0vsT2, T3); LVDs, EF (T0vsT1, T2, T3), CO (T0vsT3). Discussion and conclusions This study shows the effect of different dosages of dobutamine on heart activity in anaesthetized. No significant differences were found among IVSd, LVDd, LVVold and SV values at different dosages of dobutamine. Significative differences were found for IVSs, LVVols (T0vsT2, T3); LVDs, EF (T0vsT1, T2, T3), CO (T0vsT3). Discussion and conclusions This study shows the effect of different dosages of dobutamine on heart activity in anaesthetized horses. According with previous studies,the 2.5 μg/kg/min infusion improved cardiac work with positive effect on haemodynamics and did not produce chronotropic effects and arrhythmias. The higher dosages produced similar changes in heart parameters to those produced during exercise.
Evaluation of echocardiographic parameters during dobutamine infusion in anesthetized horses
SGORBINI, MICAELA;BRIGANTI, ANGELA;BARAGLI, PAOLO;
2011-01-01
Abstract
Introduction Administration of dobutamine can be used as pharmacological stress testing in echocardiography like a substitute of exercise stress testing. The aim of the study was to investigate by echocardiography the effects of different dosages of dobutamine on heart activity in anaesthetized horses. Materials and Methods Six healthy trotter female horses aged 8±1.5 years old and weighted 468±24 kg were used. Each horse was premedicated with acepromazine (0.03 mg/kg). Twenty minutes later, xylazine 0.5 mg/kg was administered. After ten minutes general anaesthesia was induced with ketamine (2.2 mg/kg) and diazepam (0.1 mg/kg) and maintained with isoflurane and oxygen. Horses were placed on operating table in left recumbency. No surgical procedure was carried out. Echocardiography was performed before (T0) dobutamin infusion, at 2.5 μg/kg/min (T1), 5.0 μg/kg/min (T2), and 7.5 μg/kg/min (T3) dosages. The lower dosage was started 15’ after induction of anaesthesia, then each dosage was infused IV for 15’. Registration of the different parameters of echocardiography and of the mean artery pressure (MAP) was made at the end of each infusion time. Interventricular septal dimension (IVS), left ventricular internal diameter (LVID), left ventricular volume (LVVol), stroke volume (SV), ejection fraction (EF) and cardiac output (CO) were recorded both in systole (s) and diastole (d). A one-way analysis of variance for repeated measures and a Tukey posthoc test were used to compare the effect of treatment between basal condition and the 3 different dosages. Significance was P < .05. Results Two/6 (33%) horses developed supraventricular tachycardia (HR>60 bm) at T2, 5/6 (83%) showed HR>60 bm at T3 and 1/5 (20%) developed ventricular extrasystole. The measures were reported in average±standard deviation. Significative differences were found for IVSs, LVVols (T0vsT2, T3); LVDs, EF (T0vsT1, T2, T3), CO (T0vsT3). Discussion and conclusions This study shows the effect of different dosages of dobutamine on heart activity in anaesthetized. No significant differences were found among IVSd, LVDd, LVVold and SV values at different dosages of dobutamine. Significative differences were found for IVSs, LVVols (T0vsT2, T3); LVDs, EF (T0vsT1, T2, T3), CO (T0vsT3). Discussion and conclusions This study shows the effect of different dosages of dobutamine on heart activity in anaesthetized horses. According with previous studies,the 2.5 μg/kg/min infusion improved cardiac work with positive effect on haemodynamics and did not produce chronotropic effects and arrhythmias. The higher dosages produced similar changes in heart parameters to those produced during exercise.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
