Dexmedetomidine Alone or Combined With Morphine for Epidural Anesthesia in Bitches Undergoing Elective Ovariohysterectomy.

The purpose of this study was to assess perioperative analgesia provided by the combination of epidural dexmedetomidine and morphine in bitches undergoing elective ovariohysterectomy. Twenty-four bitches were included in the study and allocated into 3 groups: GM, morphine 0.1 mg/kg; GD, dexmedetomidine 2 µg/kg; and GDM, dexmedetomidine and morphine at the same doses. All solutions were diluted in saline to a total of 0.36 mL/kg. Heart rate (HR), respiratory rate (FR) and systolic blood pressure (SAP) were recorded prior to epidural analgesia (TB), immediately following epidural analgesia (TEA), at surgical incision (TSI), at the first ovarian pedicle clamping (TOP1), at the second pedicle clamping (TOP2), at uterine stump clamping (TUC), at the start of abdominal cavity closure (TSC) and at the end of skin closure (TEC). Rescue analgesia with fentanyl was administered at 2 µg/kg IV if nociception corresponding to a 20% increase of any cardiorespiratory variables was noted. Postoperative pain assessment was performed using a modified composite Glasgow pain scale along the first 6 hours following the end of surgery. Numeric data were compared using ANOVA for repeated measures followed by Tukey test and ovarian ligament relaxation was analyzed using chi-square test under 5% significance. No differences were found on FR among times or groups, although HR showed significant differences between GM and GD at TSI, TOP1, TOP2, TSC and TEC and between GM and GDM at TEA and TSI (significantly lower HR values recorded in dexmedetomidine groups). Differences among time points were found on HR between TB and TEA in GD and on PAS between TOP1 and TSC in GM and between TOP1 and TUC in GDM (P < .05). Ovarian ligament relaxation was significantly more present in groups using dexmedetomidine, although the number of rescue analgesia administrations did not differ among groups. Kaplan-Meyer analysis failed to show significant differences on time of rescue analgesia administration among groups (P > .05). In conclusion, the combination of epidural dexmedetomidine and morphine is a more interesting choice for elective ovariohysterectomy in bitches for producing analgesia comparable to that of each drug alone, with noticeable relaxation of ovarian ligaments and lesser cardiovascular consequences.

Hemodynamic Effects of Different Combinations of Midazolam and Opioids in Healthy Dogs.

The purpose of this study was to compare the hemodynamic effects of four different combinations of midazolam and opioids in healthy dogs. Twenty-four healthy dogs were divided in four groups (n = 6) using intramuscular midazolam 0.3 mg/kg and morphine 0.3 mg/kg (GMOR), methadone 0.3 mg/kg (GMET), butorphanol 0.2 mg/kg (GBUT) or fentanyl 5 ug/kg (GFEN). Cardiovascular variables were recorded before (TB) and 20 minutes following drug administration (T20) and comprised arterial blood pressure, heart rate and cardiac index. Subsequently, left ventricular work index and total peripheral resistance index were calculated using the previous variables. At the end of the study, data were compared using analysis of variance followed by Tukey test and Friedman followed by Dunn test, all under 5% significance. No differences were found on cardiovascular variables at all times among the groups, which indicates that all combinations provide hemodynamic stability for clinical sedation of healthy dogs. However, a few animals showed paradoxical excitation in GBUT. In conclusion, the association of midazolam with morphine, methadone, butorphanol or fentanyl provides cardiovascular stability and can be used to sedate dogs undergoing cardiovascular examination, although caution is warranted with the use of midazolam with butorphanol due to possible paradoxical excitation.