Avian anaesthesia related mortality and the associated risk factors in a UK zoological collection

Ultrasound-guided sciatic nerve block injections in barred owl (Strix varia) cadavers

OBJECTIVE

To describe an ultrasound-guided approach to the sciatic nerve and the distribution of nerve staining using two injectate volumes of dye in barred owls.

STUDY DESIGN

Descriptive, randomized, assessor-blinded, cadaveric study.

ANIMALS

Twelve barred owl cadavers.

METHODS

The sciatic nerve was visualized with a 13-6 MHz linear ultrasound probe placed on the medial aspect of the proximal femur in barred owl cadavers. A needle was inserted at the proximal caudal thigh, and cranially advanced in-plane until the tip was immediately adjacent and ventral to the sciatic nerve. Eleven owls were injected bilaterally with a 1:1 solution of 1% methylene blue and 0.5% ropivacaine, with high-volume (HV; 0.4 mL kg-1) and low-volume (LV; 0.2 mL kg-1) treatments. Nerve staining ≥ 1 cm circumferentially was determined by dissection 15 minutes post-injection. The coelom was then opened to inspect for aberrant dye spread. In one barred owl cadaver, a 1:1 solution of 1% methylene blue and 74% ioversol contrast was injected, and computed tomography was performed immediately before and 15 minutes after injection for evaluation of injectate spread.

RESULTS

The HV treatment (0.4 mL kg-1) resulted in successful nerve staining in 100% of injections, whereas the LV treatment (0.2 mL kg-1) resulted in successful nerve staining in 91% of injections. There was no leakage of injectate into undesired locations (e.g. coelomic cavity) in any cadaver.

CONCLUSIONS AND CLINICAL RELEVANCE

In barred owls, the sciatic nerve can be visualized with ultrasound and injecting a ropivacaine/dye solution under ultrasound guidance successfully stained the sciatic nerve in the majority of cases. This technique holds potential for providing analgesia distal to the stifle joint; however, further investigations are necessary to evaluate its practical application in a clinical setting.

Minimum anesthetic concentration of isoflurane and sevoflurane and cardiorespiratory effects of varying inspired oxygen fractions in Magellanic penguins (Spheniscus magellanicus)

The aim of this study was to determine the minimum anesthetic concentration of isoflurane (MACISO) and sevoflurane (MACSEVO) and evaluate the cardiorespiratory changes induced by varying fractions of inspired oxygen (FiO2) in Magellanic penguins (Spheniscus magellanicus). Twenty adult penguins (3.53 ± 0.44 kg) of undetermined sex were used. Both MACISO (n = 9) and MACSEVO (n = 13) were established using an up-and-down design. Next, twelve mechanically ventilated penguins were maintained at 1 MACISO or 1 MACSEVO (n = 6 per group) with the FiO2 initially set at 1.0. Three FiO2 values (0.6, 0.4 and 0.2) were then held constant during anesthesia for 20 minutes each. Arterial blood samples were collected for gas analysis after the 20-minute period for each FiO2. Mean ± SD MACISO was 1.93 ± 0.10% and MACSEVO was 3.53 ± 0.13%. Other than heart rate at 0.6 FiO2 (86 ± 11 beats/minute in MACISO and 132 ± 37 beats/minute in MACSEVO; p = 0.041), no significant cardiorespiratory differences were detected between groups. In both groups, decreasing the FiO2 produced increased pH values and reduced partial pressures of carbon dioxide and bicarbonate. Partial pressures of oxygen (PaO2) gradually lowered from 1.0 FiO2 through 0.2 FiO2, though hypoxemia (PaO2 < 80 mmHg) occurred only with the latter FiO2. The MACISO and the MACSEVO for the Magellanic penguin fell within the upper range of reported avian MAC estimates. To prevent hypoxemia in healthy, mechanically ventilated, either isoflurane- or sevoflurane-anesthetized Magellanic penguins, a minimum FiO2 of 0.4 should be used.

Establishing an MRI-Based Protocol and Atlas of the Bearded Dragon (Pogona vitticeps) Brain

The bearded dragon (Pogona vitticeps) has become a popular companion lizard, and as such, clients have increasingly come to expect the application of advanced diagnostic and therapeutic options in their care. The purpose of this study was to establish an MRI-based protocol and brain atlas to improve diagnostic capabilities in bearded dragons presenting with neurologic dysfunction. Using a high-field 3T magnet, in vivo MRI of the brain was successfully performed in seven healthy bearded dragons utilizing an injectable anesthetic protocol utilizing intravenous alfaxalone. From this, we created an atlas of the brain in three planes, identifying nine regions of interest. A total scan time of 35 min allowed for the collection of a quality diagnostic scan and all lizards recovered without complication. This study provides practitioners a neuroanatomic reference when performing brain MRI on the bearded dragon along with a concise and rapid MRI protocol.