Echocardiographic Assessment of Healthy Midazolam/Butorphanol or Midazolam/Morphine-Sedated Dogs.

The purpose of this study was to assess the effects of midazolam combined with morphine or butorphanol on echocardiographic variables of healthy dogs. Twenty-four dogs of various breeds aged 34.33 ± 23.41 months and weighing 8.1 ± 4.7 kg were enrolled in the study. Subjects were randomly allocated in one of two experimental groups of sedation with intramuscular midazolam (0.3 mg/kg) combined with butorphanol (0.2 mg/kg) (GB, n = 12) or morphine (0.3 mg/kg) (GM, n = 12). Transthoracic echocardiographic examinations comprised B-Mode, M-Mode, spectral Doppler and pulsed tissue Doppler assessment. Data were recorded before sedation (TB) and 20 minutes following intramuscular administration of either sedation protocol (TS). Data were analyzed using repeated measures ANOVA followed by Tukey's posthoc test. Shortening fraction, ejection fraction, left ventricular diameter and volume did not differ among groups and time points. The A and E' waves were decreased in GM at TS compared to TB. Isovolumic relaxation time, Ae/Ao ratio, aortic and pulmonary flows and S' wave did not differ among time points and groups. These sedation protocols did not cause clinically relevant changes in echocardiographic variables, therefore can be used for sedation of uncooperative dogs during echocardiographic evaluation.

Conventional Echocardiography and Two-Dimensional Speckle Tracking in Healthy Sevoflurane-Anesthetized Dogs Undergoing Continuous Rate Infusion of Nalbuphine.

Nalbuphine is an agonist-antagonist opioid with adequate analgesic properties and few depressant effects on the respiratory system. However, there are no detailed reports available on cardiovascular effects of nalbuphine in dogs. The aim of this study was to assess the effects of a continuous rate infusion (CRI) of nalbuphine on left ventricular systolic and diastolic function of healthy sevoflurane-anesthetized dogs. Eighteen mixed-breed bitches aged 1-4 years and weighing 9.9 ± 3.8 kg were used. Dogs were randomly assigned to one of two groups: nalbuphine (GN, n = 9) and control (GC, n = 9). Anesthesia was induced and maintained with sevoflurane (2V%) followed by an intravenous (IV) bolus of nalbuphine (0.3 mg/kg) or 0.9% NaCl at equal volume and then CRI of nalbuphine (0.4 mg/kg/h) or 0.9% NaCl at an equal infusion rate. Echocardiographic and hemodynamic variables were determined at baseline and 20, 40, 60, and 80 minutes following start of CRI. No differences were found between groups for left ventricular systolic and diastolic variables obtained through conventional echocardiography and two-dimensional speckle tracking. Likewise, hemodynamic variables did not differ between groups. The E'/A' ratio significantly increased at 20 minutes compared to baseline only in GN. Nalbuphine given at a CRI does not influence left ventricular systolic and diastolic function in healthy sevoflurane-anesthetized dogs.

Effect of a constant rate infusion of remifentanil hydrochloride on left ventricular systolic and diastolic function in propofol-anesthetized dogs.

OBJECTIVE To assess the effects of a constant rate infusion (CRI) of remifentanil hydrochloride on left ventricular systolic and diastolic function in healthy propofol-anesthetized dogs. ANIMALS 6 healthy Beagles. PROCEDURES Each dog underwent 2 experimental treatments separated by a 7-day interval. In 1 treatment, anesthesia was induced with propofol and maintained with a CRI of propofol (0.6 mg/kg/min); dogs also received a CRI of saline (0.9% NaCl) solution. In the other treatment, anesthesia was similarly induced and maintained with propofol; dogs also received a CRI of remifentanil (0.3 µg/kg/min). Doppler echocardiographic and hemodynamic variables of interest were determined at baseline (before anesthesia) and at 20, 40, and 60 minutes following the simultaneous start of the 2 CRIs of each treatment; all CRIs were administrated for 60 minutes. RESULTS For the 2 treatments, end-diastolic and end-systolic volume indices did not differ from baseline or at any time point. Peak tissue Doppler-derived mitral annulus systolic velocity decreased from baseline with both treatments; however, no differences were found between treatments at any time point. Mean arterial blood pressure decreased similarly with both treatments. Heart rate and Doppler-determined cardiac index decreased significantly with the propofol-remifentanil treatment, compared with findings for the propofol-saline solution treatment. For the propofol-remifentanil treatment, the ratio of peak velocity flow in early diastole to that in late diastole remained > 1.80, whereas the ratio of early to late Doppler-derived mitral annulus velocity had a normal relaxation pattern. CONCLUSIONS AND CLINICAL RELEVANCE Results of this study indicated that a CRI of remifentanil administered along with a CRI of propofol does not impair left ventricular systolic and diastolic function in healthy dogs.