The echocardiographic effects of romifidine in dogs with and without prior or concurrent administration of glycopyrrolate

To determine the cardiopulmonary response to romifidine (RO) in the dog with or without prior or concurrent administration of glycopyrrolate. Randomized, cross–over experimental study. Six (three male, three female) cross–bred dogs weighing 23 ± 2.4 kg. Two–dimensional guided M–mode echocardiography was performed in conscious dogs simultaneously with measurement of systolic arterial blood pressure (SBP) and heart rate (HR). Dimensions of the left ventricle (LVID), interventricular septum (IVS), and left ventricular free wall (LVFW) were obtained in systole (S) and diastole (D). Amplitude of motion (Amp) of the IVS and LVFW were also measured. From these, measures of wall stress (WS) and fractional shortening (FS) of the left ventricle were derived. Baseline echocardiographic measurements were recorded, following which one of the five treatments was administered. Glycopyrrolate (G) 0.01 mg kg−1, or saline (S) 0.5 mL, was administered IM as pre–medication (Gp or Sp), or G was administered concurrently (Gc) with romifidine (RO). Treatments were: T1, Sp + RO (40 μg kg−1); T2, Gp + RO (40 μg kg−1); T3, Sp + RO (120 μg kg−1); T4, Gp + RO (120 μg kg−1); and T5, Sp + Gc +RO (120 μg kg−1). Romifidine or RO + Gc was administered SC 20 minutes after pre–medication (time 0), and further measurements were taken 10, 20, 30, 60, and 90 minutes after RO. Echocardiographic indices of cardiac systolic function (LVID–S, FS, Amp–LVFW) and HR were decreased in RO–sedated dogs (p < 0.0001) . The magnitude of change in cardiac indices was least with low–dose RO. At most sampling times, high–dose RO produced significantly more alteration in cardiac indices. Systolic blood pressure increased in all treatment groups, with the greatest increases in those groups receiving G. Glycopyrrolate significantly increased HR; however, cardiac indices were further reduced. Wall stress significantly increased, with a more dramatic increase in groups receiving G. Indices of LV systolic function were reduced in RO–sedated dogs in a dose–related manner. Glycopyrrolate further reduced these indices and dramatically increased measurements of wall stress in dogs sedated with RO. Use of low–dose RO minimizes cardiac dysfunction; however, it should still be used cautiously in dogs with cardiomyopathy or heart failure. The routine use of G is not recommended to alleviate the bradycardia associated with RO in conscious dogs.