Sedative and cardiorespiratory effects of three doses of romifidine in comparison with medetomidine in five cats

Effect of Intramuscular Medetomidine Administration on Tear Flow in Rats

Medetomidine has been reported to decrease tear flow significantly in dogs, cats, and pigs when used as a sedative or analgesic; however, there are no such reports when it comes to rats. The present study aimed to investigate the effect of medetomidine on tear flow in rats. Medetomidine in doses of 50, 100, or 200 µg/kg or a physiological saline solution as the control, were administered intramuscularly to male Slc:Wistar/ST rats. After the administration of medetomidine, tear flow in both eyes was measured using a phenol red thread tear test. The area under the curve (AUC) of phenol red thread test values from baseline to 8 h was calculated. Data were plotted against the dose of medetomidine and simple linear regression analysis was performed. The effect of the drug on phenol red thread test values was considered dose-related when linear analysis yielded a significant relationship. In all medetomidine-treated groups, tear flow decreased significantly in both eyes after administration, while no significant changes were observed in either eye in the control group. The AUC values from baseline to 8 h after administration in groups treated with 100 and 200 µg/kg of medetomidine were significantly lower in both the left and right eyes compared to the control group. The linear regression of the AUC values was significant for both eyes. Our results indicated that the intramuscular administration of medetomidine in rats decreased tear flow significantly in a dose-dependent manner.

Evaluation of a ketamine-propofol drug combination with or without dexmedetomidine for intravenous anesthesia in cats undergoing ovariectomy

OBJECTIVE

To evaluate the use of a ketamine-propofol combination, with or without dexmedetomidine, in cats undergoing ovariectomy and to assess Heinz body formation following administration of these drugs.

DESIGN

Randomized clinical trial.

ANIMALS

15 client-owned female cats.

PROCEDURES

Anesthesia was induced with a ketamine (2.0 mg/kg [0.91 mg/lb])-propofol (2.0 mg/kg) combination with (n = 7) or without (8) dexmedetomidine (0.003 mg/kg [0.0013 mg/lb]) and was maintained via continuous IV infusion of a 1:1 ketamine-propofol combination (administration rate for each drug, 10.0 mg/kg/h [4.54 mg/lb/h]). Cats underwent ovariectomy; duration of infusion was 25 minutes. Physiologic variables were measured at predetermined time points. Heinz bodies were quantified via examination of blood smears. Numeric scales were used to assess quality of recovery, degree of sedation, and signs of pain after surgery.

RESULTS

The ketamine-propofol group had a significantly higher mean heart rate at several time points during drug infusion, a significantly shorter time from the end of infusion to extubation (7 vs 29 minutes), and significantly lower sedation scores for the first hour after surgery than did the ketamine-propofol-dexmedetomidine group. Other variables were similar between groups; recovery was smooth, and anesthesia and postoperative analgesia were deemed adequate for all cats. The number of RBCs with Heinz bodies was not increased after surgery, compared with values immediately after anesthetic induction.

CONCLUSIONS AND CLINICAL RELEVANCE

Total IV anesthesia with a ketamine-propofol combination, with or without dexmedetomidine, appeared to be effective in healthy cats. These short-term infusions produced smooth recovery and adequate analgesia during the postoperative period.

Sedative effects of three doses of romifidine in comparison with medetomidine in cats

OBJECTIVE

To compare the sedative effects of three doses of romifidine with one dose of medetomidine.

STUDY DESIGN

Prospective blinded experimental cross-over.

ANIMALS

Five adult Domestic Short Hair cats.

METHODS

Cats were administered romifidine at 80, 120 and 160 μg kg(-1) or medetomidine at 20 μg kg(-1) (M20) intramuscularly (IM). Sedative effects were assessed for 3 hours by summing the scores given to posture, auditory response, resistance to positioning, muscular relaxation, and response to noxious stimuli, giving a total sedation score (TS). The area under the curve (AUC) of TS ≥7 (the score considered as clinically useful sedation) was calculated. Times to stages of sedation were determined. Some physiological parameters were measured. Data to compare treatments were analysed by anova or Kruskal-Wallis test as relevant.

RESULTS

All treatments gave a TS considered clinically useful. There were no significant differences between treatments for times to onset of sedation, maximum TS reached, or AUC. Differences between romifidine treatments for other sedation parameters were not significant but the time to maximum TS and to recovery was shortest in M20. Heart rate (HR) fell significantly with all treatments and, although with M20 it recovered at 65 minutes, it remained significantly depressed for 3 hours after all romifidine treatments. Most cats vomited, and/or hypersalivated after all treatments.

CONCLUSIONS

Doses of 80, 120 and 160 μg kg(-1) romifidine IM produce sedation in cats which is similar to that following medetomidine 20 μg kg(-1) . Recovery from sedation and of physiological parameters was quickest after M20.

CLINICAL RELEVANCE

Doses of romifidine considerably lower than those investigated by previous authors give a clinically useful level of sedation, and their use might result in less side effects and a quicker recovery.

Evaluation of cardiorespiratory effects of combinations of dexmedetomidine and atropine in cats

The cardiovascular effects of dexmedetomidine alone or in combination with atropine were studied in six cats. Cats underwent four treatments in a randomized crossover design as follows: DEX15, saline+dexmedetomidine 15 μg/kg; DEX30, saline+dexmedetomidine 30 μg/kg; ADEX15, atropine+dexmedetomidine 15 μg/kg; ADEX30, atropine+dexmedetomidine 30 μg/kg. Pulse rate (PR) and systolic arterial pressure (SAP) decreased in DEX15 and DEX30. Premedication with atropine was effective in preventing bradycardia (PR<100 beats/min) and resulted in a biphasic effect in blood pressure. Hypertension was followed by a gradual decrease in SAP. Rate pressure product decreased in DEX15 and DEX30 whereas in ADEX15 and ADEX30 it remained within baseline values for at least 60 min. Although premedication with atropine in cats sedated with dexmedetomidine prevents bradycardia, it induces hypertension and increases myocardial oxygen consumption. The magnitude of cardiovascular effects produced by dexmedetomidine in cats does not seem to be dose-related.