Cardiopulmonary effects of medetomidine, oxymorphone, or butorphanol in selegiline-treated dogs

ECHOCARDIOGRAPHY AND DIRECT ARTERIAL BLOOD PRESSURE MEASUREMENT IN CAPTIVE CHIMPANZEES (PAN TROGLODYTES) DURING TWO PHASES OF AN ANESTHETIC PROTOCOL

The effects of α-2 agonists on echocardiographic findings in great apes are not well documented, and knowledge of these effects would expand the understanding of cardiac examinations of chimpanzees under anesthesia with protocols using these drugs. Ten adult chimpanzees (Pan troglodytes), four males and six females, underwent echocardiographic examinations after anesthesia with dexmedetomidine, midazolam, and ketamine (phase 1). Four animals required isoflurane to achieve an adequate plane of anesthesia. Atipamezole was used to antagonize dexmedetomidine, and all remaining animals were placed on isoflurane (phase 2), and then a second echocardiogram was performed. Direct arterial blood pressure was monitored during the anesthetic event. Measurements and recordings were assessed for statistically significant differences between the two phases and sex. There were no significant differences between phases or sex for any two-dimensional echocardiographic measurement of systolic function, although interventricular septum thickness at end systole approached a significant decrease from phase 1 to phase 2 (P = 0.058) when sex was considered a between-subject factor. Left ventricular outflow tract (P = 0.017) and pulmonary artery (P = 0.028) velocities increased after reversal of the dexmedetomidine. Diastolic transmitral flow was consistent with grade 3 diastolic dysfunction (median early to late ventricular filling velocities (E/A) of 2.02, interquartile range [IQR], 1.53-2.13) with a nonsignificant decrease of E velocity and increase in A velocity and decreased E/A after reversal. Trace mitral and tricuspid regurgitation were common findings in the sample population. Arterial blood pressure significantly decreased between phase 1 and phase 2 (P < 0.01). All chimpanzees entered a hypotensive state (mean arterial pressure < 60 mm Hg) during phase 2. Although limited by the small number of chimpanzees, this study showed an increase in afterload, potential diastolic dysfunction, and a decrease in blood pressure after the antagonism of dexmedetomidine. Additional studies to further assess the effects of α-2 agonists in chimpanzees are warranted.

GREAT APE HEART PROJECT GUIDELINES FOR THE ECHOCARDIOGRAPHIC ASSESSMENT OF GREAT APES

Cardiovascular disease (CVD) has been identified as a major cause of mortality in all four great ape taxa in zoologic institutions. In an effort to better understand and treat CVD in captive great apes, a program called the Great Ape Heart Project (GAHP), based at Zoo Atlanta, collects and maintains a database of echocardiograms and other relevant medical information relating to the cardiac health status of great apes. Cardiac health assessments have become standard practice among North American zoos that house great apes and are recommended by all four great ape Species Survival Plans (SSP) for the assessment of CVD in captive great apes. As of December 31, 2017, more than 70 ape-holding institutions have submitted approximately 1,100 cardiac examinations of great apes to the GAHP, information from which is stored in the GAHP database. Transthoracic echocardiography is one of the most practical and cost-effective diagnostic imaging techniques for the evaluation of cardiac function in great apes. Standardization of echocardiographic measurements is critical for maximizing the diagnostic value of an echocardiographic exam and for utilization of stored information in comparative studies within and between the great ape taxa. The following manuscript offers suggestions for standardization of nomenclature, imaging technique, echocardiographic measurements, data storage, and reporting of cardiac exams for submission into the GAHP database with the goal of promoting consistency and quality in data collection.

ECHOCARDIOGRAPHIC PARAMETERS IN EIGHT ADULT TIGERS ( PANTHERA TIGRIS) DURING TWO PHASES OF AN ANESTHETIC PROTOCOL

Eight adult tigers ( Panthera tigris) underwent a complete echocardiographic examination following sedation with medetomidine, midazolam, and induction of general anesthesia using ketamine and isoflurane (phase 1). Atipamezole was used to antagonize medetomidine (phase 2) and a second echocardiographic examination was performed. Physiologic tricuspid and pulmonic regurgitations were common findings in the sample population and one tiger was excluded from final analyses due to the finding of a ventricular septal defect. Measurements and mean arterial pressure were assessed for statistically significant differences between the two examination phases as well as gender and weight. There was a statistically significant difference between interventricular septum thickness at end systole, ejection fraction, and mean arterial pressure between anesthetic phases while fractional shortening and left ventricular internal dimension at end-systole approached, but did not reach, statistical significance between phases. Weight was found to be a statistically significant predictor of stroke volume and left ventricular internal dimension at end-diastole. The echocardiographic measurements obtained during this study can be used as guidelines for future examinations in adult tigers. The effects of medetomidine on these measurements and systolic function should be taken into account when performing echocardiograms and monitoring anesthetic events.

The cardiopulmonary effects of a peripheral alpha-2-adrenoceptor antagonist, MK-467, in dogs sedated with a combination of medetomidine and butorphanol

OBJECTIVE

To compare the cardiopulmonary effects of intravenous (IV) and intramuscular (IM) medetomidine and butorphanol with or without MK-467.

STUDY DESIGN

Prospective, randomized experimental cross-over.

ANIMALS

Eight purpose-bred beagles (two females, six males), 3-4 years old and weighing 14.5 ±1.6 kg (mean ± SD).

METHODS

All dogs received four different treatments as follows: medetomidine 20 μg kg(-1) and butorphanol tartrate 0.1 mg kg(-1) IV and IM (MB), and MB combined with MK-467,500 μg kg(-1) (MBMK) IV and IM. Heart rate (HR), arterial blood pressures (SAP, MAP, DAP), central venous pressure (CVP), cardiac output, respiratory rate (fR ), rectal temperature (RT) were measured and arterial blood samples were obtained for gas analysis at baseline and at 3, 10, 20, 30, 45 and 60 minutes after drug administration. The cardiac index (CI), systemic vascular resistance index (SVRI) and oxygen delivery index (DO2 I) were calculated. After the follow-up period atipamezole 50 μg kg(-1) IM was given to reverse sedation.

RESULTS

HR, CI and DO2 I were significantly higher with MBMK after both IV and IM administration. Similarly, SAP, MAP, DAP, CVP, SVRI and RT were significantly lower after MBMK than with MB. There were no differences in fR between treatments, but arterial partial pressure of oxygen decreased transiently after all treatments. Recoveries were uneventful following atipamezole administration after all treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

MK-467 attenuated the cardiovascular effects of a medetomidine-butorphanol combination after IV and IM administration.

Evaluation of aqueous tear production in dogs after general anaesthesia with medetomidine-propofol-carprofen-halothane

The influence of an anaesthetic protocol, which included medetomidine, propofol, carprofen and halothane on tear production in the dog. There are no previous studies on the effects of this combination on tear production in dogs or in any other species. The present study included 39 dogs, which underwent non-ophthalmic surgery in our clinic. Preanaesthetically, all dogs had normal tear production (18.62±3.65 mm/minute) as this was recorded with Schirmer tear test I (STT I) and the ophthalmologic examination did not reveal anything abnormal. Tear production readings were recorded before the administration of premedication, at the end of anaesthesia, one hour and two hours postanaesthesia. No reverse agent was administrated. At the end of anaesthesia (right eye (oculus dexter, OD) P<0.0005, left eye (oculus sinister, OS) P<0.0005), as well as one hour postanaesthesia (OD P=0.020, OS P=0.001) there was a statistically significant reduction in tear production, which returned to normal values two hours postanaesthesia, regardless of the duration of the operation. This anaesthetic combination resulted in a decrease in tear production and, therefore, the use of tear substitute treatment in dogs undergoing anaesthesia with this protocol (combination) from the time the sedative is given until at least two hours after the end of anaesthesia is highly recommended.

Contact heat thermal threshold testing in beagle dogs: baseline reproducibility and the effect of acepromazine, levomethadone and fenpipramide

BACKGROUND

In this methodology article a thermal threshold testing device designed to test nociception in cats was assessed in six dogs. The purpose of this study was to investigate baseline reproducibility of thermal thresholds obtained by the contact heat testing device, to assess the influence of acepromazine and levomethadone and fenpipramide in dogs. The relationship between change in nociceptive thermal threshold and the opioid's plasma concentration was determined. Six adult beagle dogs received levomethadone (0.2 mg/kg), acepromazine (0.02 mg/kg) or saline placebo by intramuscular injection (IM) in a randomized cross-over design. Three baseline nociceptive thermal threshold readings were taken at 15 minutes intervals prior to treatment. Further readings were made at 15, 30, 45, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, 360, 420 and 480 minutes after injection. A sedation score was assigned at every reading. Four saline placebo treatments were performed to assess baseline reproducibility. Levomethadone serum concentrations were measured prior and 0.5, 1, 2, 4, 8, 12 and 24 hours after drug dosing in a separate occasion.

RESULTS

Acepromazine did not seem to increase the thermal threshold at any time. After levomethadone there was a significant rise of the thermal threshold between 15 to 120 minutes at serum concentrations between 22.6-46.3 ng/mL. Baseline reproducibility was stable in adult beagle dogs.

CONCLUSION

The thermal threshold testing system is a suitable device for nociceptive threshold testing in dogs.

Continuous infusion in adult females dogs submitted to ovariohysterectomy with midazolam-xylazine and/or medetomidine pre-treated with methotrimeprazine and buprenorphine

PURPOSE: To compare, by continuous infusion of ketamine or medetomidine combined to methotrimeprazine and buprenorphine, ketamine and midazolam, the degree of hypnosis, myorelaxation, anesthetic quality and surgical feasibility through evaluation of possible parametric alterations and recovery quality. METHODS: 20 healthy adult females dogs, aged 3 to 5 years, body weight between 7 and 15 kg, were assigned randomly and homogenously to 2 groups of 10 animals each (n=10), group 1 (G1) and group 2 (G2), respectively. Animals of G1 were subjected to a pre-treatment with intravenous 1.0 mg/kg methotrimeprazine and or 3ì/kg. After 15 minutes, a 5.0 mg/kg ketamine and 0.2 mg/kg midazolam were intravenously injected. Immediately after induction, an anesthetic combination of 0.4 mg/kg/h midazolam, 20 mg/kg/h ketamine and 1.0 mg/kg/h xylazine, was continuously and intravenously administered for 30 minutes. The same techniques were used in G2 except for the substitution of xylazine for 30ìg/kg/h medetomidine. RESULTS: In G1 there was a 1st and 2nd degree atrioventricular heart block, a longer recovery period and lower quality. In G2 a 1st degree atrioventricular heart block occurred but isolated and ephemeral. CONCLUSIONS: The continuous infusion method, besides reducing drugs utilization, prevented collateral effects allowing a more tranquil recovery with no excitations, both protocols permitted the surgical procedure (ovary-hysterectomy) bringing about a reduction in hypnosis and an accentuated myorelaxation. Xylazine and medetomidine showed a similar pharmacodynamic behavior but with different clinical aspects. The electrocardiographic alterations observed in G2 and in a lower degree in G1 must be well studied. Describers: dogs, ketamine, methotrimeprazine, medetomidine, midazolam and xylazine.

Endogenous opiates and behavior: 2004

This paper is the 27th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over 30 years of research. It summarizes papers published during 2004 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.