June 2023 newsletter
Hello, Vetaheader! Our monthly newsletter is here. This time, we have papers for mammals, birds and reptiles!
First, we have a paper on the feasibility of ultrasonographic assessment of the tympanic bullae of conscious rabbits. Rabbits are prone to otitis media due to infectious agent spreading through auditory tube or extension of otitis externa, and inflammation may cause accumulation of fluid, thickening of bone, or boney lysis of bullae.
Forty healthy rabbits were used in this study to evaluate if non-sedated US exams of the tympanic bullae would be possible. For each rabbit, fur was clipped over a 3×3 cm area at the level of the angular process of each mandible, then three ultrasonographic planes of each TB were imaged via ventral approach, with measurement of the time taken to complete the examination. A compact linear ultrasound transducer with 7-15MHz (3 cm long x 1 cm wide) was used, and rabbits were positioned in sternal recumbency on an upside-down cushion to increase space available under chin. This procedure required two handlers, and lasted for less than 10 minutes. Three items were assessed for each plane: TB depth, wall integrity, and contents (present or absent).
Results showed that the examination could be carried out successfully in 36 of 40 (90%) of rabbits with clipping, and only the transverse sections were not well tolerated by the animals. Oblique and longitudinal sections were carried out on 33 of 40 (83%) rabbits of all sizes. Visualization of the distal bulla wall was observed in 2 of the 40 (5%) subjects, consistent with abnormal fluid contents or bulla osteitis.
The take home message is: these examinations were well tolerated by rabbits, but did require clipping. This modality, which was fast and easy to learn, allowed for suspicion of subclinical otitis media in 2 rabbits. Transverse image was not possible in most rabbits, particularly in small ones.
Second, we have a study on the comparison of IM alfaxolone +midazolam and midazolam+butorphanol in hens. Chickens often undergo veterinary procedures requiring sedation; however, there is little published research evaluating the efficacy of sedation protocols in this species. Besides, elevations in body temperature and heart rate have been documented secondary to handling stress in chickens, and stress can result in decreased egg production.
Eleven healthy adult hens were randomly administered midazolam 2.5 mg/kg IM combined with either alfaxalone 15 mg/kg IM (AM) or butorphanol 3 mg/kg IM (BM), with a 35-day washout period between groups. Time to first effects, recumbency, standing, and recovery were recorded, as well as physiologic parameters and sedation scores. Positioning for whole body radiographs was attempted for bo. At 30 minutes, flumazenil 0.05 mg/kg IM was administered to all hens.
Results showed that radiograph positioning successful in all birds in the AM group by 25 minutes; for the BM group, 7/11 could be positioned. AM protocol had faster onset, longer duration of recumbency, and deeper sedation when compared to BM. However, 4 birds in the AM group displayed mild hyperexcitability, transient opisthotonos, or both; also elevation of feathers and muscle fasciculations was seen in one bird. Cardiorespiratory derangements were not seen in any of the birds.
The take home message is: alfaxalone 15 mg/kg and midazolam 2.5 mg/kg IM were effective for chemical restraint of chickens for minor, noninvasive procedures and did not result in significant cardiorespiratory derangements.
Lastly, we have a pharmacodynamic study on the effects of ICe, SC, IM and IV injections of alfaxolone in bearded dragons. Ten animals were used for this complete crossover study. Injection sites used in the study are listed below:
🦎Intravenous (IV): ventral coccygeal vein
🦎Intramuscular (IM): both on right and left biceps muscles, to split the dose
🦎Subcutaneous (SC): left scapula-humeral joint
🦎Intracelomatic (ICe): caudoventral coelom
The results showed that the IV route had a predictably deep plane of sedation, including loss of deep pain, for 35-140 minutes. Other routes of administration were less predictable in inducing deep sedation. End-systolic volume increased up to 2.1 mL in all bearded dragons after alfaxalone at time to maximum effect, suggesting an alteration in contractility; therefore, use caution if wanting to use this drug in cardiac patients!
The take home message is: alfaxalone 15 mg/kg IV provides consistent sedation quality in bearded dragons, but does increase end-systolic volume. IM or SC are reasonable alternatives.
Hope these help you and, as always, I will see you next month!)
Sincerely,
Laila Proença
