Anesthesia and Analgesia in Reptiles

PHARMACOKINETICS OF TRAMADOL AND O-DESMETHYLTRAMADOL IN GIANT TORTOISES (CHELONOIDIS VANDENBURGHI, CHELONOIDIS VICINA)

The objective of this study was to determine the pharmacokinetics of two orally administered doses of tramadol (1 mg/kg and 5 mg/kg) and its metabolite, O-desmethyltramadol (M1) in giant tortoises (Chelonoidis vandenburghi, Chelonoidis vicina). Eleven giant tortoises (C. vandenburghi, C. vicina) received two randomly assigned, oral doses of tramadol (either 1 mg/kg or 5 mg/kg), with a washout period of 3 wk between each dose. The half-life (t½) of orally administered tramadol at 1 mg/kg and 5 mg/kg was 11.9 ± 4.6 h and 13.2 ± 6.1 h, respectively. After oral administration of tramadol at 1 mg/kg and 5 mg/kg, the maximum concentration (Cmax) was 125 ± 69 ng/ml and 518 ± 411 ng/ml, respectively. There were not enough data points to determine pharmacokinetic (PK) parameters for the M1 metabolite from either dose. Tramadol administered orally to giant tortoises at both doses provided measurable plasma concentrations of tramadol for approximately 48 h with occasional transient sedation. Oral tramadol at 5 mg/kg, on average, achieves concentrations of >100 ng/ml, the reported human therapeutic threshold, for 24 h. Based on the low levels of M1 seen in this study, M1 may not be a major metabolite in this taxon.

Cardiovascular responses and the role of the neurohumoral cardiac regulation during digestion in the herbivorous lizard Iguana iguana

Carnivorous reptiles exhibit an intense metabolic increment during digestion, which is accompanied by several cardiovascular adjustments responsible for meeting the physiological demands of the gastrointestinal system. Postprandial tachycardia, a well-documented phenomenon in these animals, is mediated by the withdrawal of vagal tone associated with the chronotropic effects of non-adrenergic and non-cholinergic (NANC) factors. However, herbivorous reptiles exhibit a modest metabolic increment during digestion and there is no information about postprandial cardiovascular adjustments. Considering the significant impact of feeding characteristics on physiological responses, we investigated cardiovascular and metabolic responses, as well as the neurohumoral mechanisms of cardiac control, in the herbivorous lizard Iguana iguana during digestion. We measured oxygen consumption rate (O2), heart rate (fH), mean arterial blood pressure (MAP), myocardial activity, cardiac autonomic tone, fH/MAP variability and baroreflex efficiency in both fasting and digesting animals before and after parasympathetic blockade with atropine followed by double autonomic blockade with atropine and propranolol. Our results revealed that the peak of O2 in iguanas was reached 24 h after feeding, accompanied by an increase in myocardial activity and a subtle tachycardia mediated exclusively by a reduction in cardiac parasympathetic activity. This represents the first reported case of postprandial tachycardia in digesting reptiles without the involvement of NANC factors. Furthermore, this withdrawal of vagal stimulation during digestion may reduce the regulatory range for short-term fH adjustments, subsequently intensifying the blood pressure variability as a consequence of limiting baroreflex efficiency.

A Critical Review on the Pharmacodynamics and Pharmacokinetics of Non-steroidal Anti-inflammatory Drugs and Opioid Drugs Used in Reptiles

Non-steroidal anti-inflammatory drugs (NSAIDs) and opioids are analgesics used for moderate to severe pain in many animals, including reptiles. However, reptilian dosing regimens are often extrapolated from other animal species. This is not ideal as inter- and intra-species variability in physiology may result in varied drug disposition. Therefore, this critical review aims to collate data from pharmacological studies of selected NSAIDs and opioids performed in reptile and provide an analysis and discussion on the existing pharmacodynamic knowledge and pharmacokinetic data of NSAIDs and opioids use in reptiles. Additionally, key pharmacokinetic trends that may aid dosing of NSAIDs and opioids in reptiles will also be highlighted. Most of the existing reports of NSAID used in reptiles did not observe any adverse effects directly associated to the respective NSAID used, with meloxicam being the most well-studied. Despite the current absence of analgesic efficacy studies for NSAIDs in reptiles, most reports observed behavioural improvements in reptiles after NSAID treatment. Fentanyl and morphine were studied in the greatest number of reptile species with analgesic effects observed with the doses used, while adverse effects such as sedation were observed most with butorphanol use. While pharmacokinetic trends were drug- and species-specific, it was observed that clearance (CL) of drugs tended to be higher in squamates compared to chelonians. The half-life (t_1/2) of meloxicam also appeared to be longer when dosed orally compared to other routes of drug administration. This could have been due to absorption-rate limited disposition. Although current data provided beneficial information, there is an urgent need for future research on NSAID and opioid pharmacology to ensure the safe and effective use of opioids in reptiles.

Snake Sedation and Anesthesia

Snakes can be more challenging to anesthetize compared with other animals because of anatomic and physiologic differences, a wide range of patient sizes, and variable responses to anesthetic agents. Snakes have preferred optimal temperature zones, which, along with physiologic characteristics, such as the ability to shunt blood toward or away from the lungs, can have an impact on anesthesia. Injectable agents, including benzodiazepines, α₂-agonists, opioids, propofol, and alfaxalone, as well as inhalant anesthetics can be used to anesthetize snakes. Pain management must be incorporated to the anesthetic plan when performing procedures that are expected to produce nociception.

Respiratory and antinociceptive effects of dexmedetomidine and doxapram in ball pythons (Python regius)

OBJECTIVE

To determine the effects of dexmedetomidine, doxapram, and dexmedetomidine plus doxapram on ventilation ([Formula: see text]e), breath frequency, and tidal volume (Vt) in ball pythons (Python regius) and of doxapram on the thermal antinociceptive efficacy of dexmedetomidine.

ANIMALS

14 ball pythons.

PROCEDURES

Respiratory effects of dexmedetomidine and doxapram were assessed with whole-body, closed-chamber plethysmography, which allowed for estimates of [Formula: see text]e and Vt. In the first experiment of this study with a complete crossover design, snakes were injected, SC, with saline (0.9% NaCl) solution, dexmedetomidine (0.1 mg/kg), doxapram (10 mg/kg), or dexmedetomidine and doxapram, and breath frequency, [Formula: see text]e, and Vt were measured before and every 30 minutes thereafter, through 240 minutes. In the second experiment, antinociceptive efficacy of saline solution, dexmedetomidine, and dexmedetomidine plus doxapram was assessed by measuring thermal withdrawal latencies before and 60 minutes after SC injection.

RESULTS

Dexmedetomidine significantly decreased breath frequency and increased Vt but did not affect [Formula: see text]e at all time points, compared with baseline. Doxapram significantly increased [Formula: see text]e, breath frequency, and Vt at 60 minutes after injection, compared with saline solution. The combination of dexmedetomidine and doxapram, compared with dexmedetomidine alone, significantly increased [Formula: see text]e at 30 and 60 minutes after injection and did not affect breath frequency and Vt at all time points. Thermal withdrawal latencies significantly increased when snakes received dexmedetomidine or dexmedetomidine plus doxapram, versus saline solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Concurrent administration of doxapram may mitigate the dexmedetomidine-induced reduction of breathing frequency without disrupting thermal antinociceptive efficacy in ball pythons.

SPINAL ANESTHESIA IN GREEN SEA TURTLES (CHELONIA MYDAS) UNDERGOING SURGICAL REMOVAL OF CUTANEOUS FIBROPAPILLOMAS

Techniques for anesthesia of green sea turtles (Chelonia mydas) are required for medical treatment. The use of spinal anesthesia has been reported in a few species of turtles for different purposes. The objective of this study was to evaluate the use of 2% lidocaine for spinal anesthesia of green sea turtles undergoing surgical removal of cutaneous fibropapillomas. Ten free-ranging green turtles presenting with cutaneous fibropapillomas were included in the study. Animals were accidentally captured or rescued by local fishermen and brought to the Ubatuba Research Base (Sao Paulo, Brazil) of the Brazilian Sea Turtle Conservation Program for rehabilitation. Animals were administered 2% lidocaine (0.2 ml/10 cm of carapace) in the epidural/subarachnoid space of the tail and monitored throughout surgery. The technique was effective for all animals, with fast onset of motor and sensory blockade (3 ± 1.76 min) and relatively fast recovery time (83.9 ± 16.2 min). Fibropapillomas were removed from all animals with no signs of pain (i.e., no behavioral response during surgical procedure, such as head and forelimb movement, showing discomfort) and they were all rehabilitated and successfully returned to their natural habitat. The technique was considered effective, safe, and affordable for use on green turtles undergoing surgical removal of cutaneous fibropapillomas.

A systematic study of injectable anesthetic agents in the brown anole lizard (Anolis sagrei )

Anolis lizards have served as important research models in fields ranging from evolution and ecology to physiology and biomechanics. However, anoles are also emerging as important models for studies of embryo development and tissue regeneration. The increased use of anoles in the laboratory has produced a need to establish effective methods of anesthesia, both for routine veterinary procedures and for research procedures. Therefore, we tested the efficacy of different anesthetic treatments in adult female Anolis sagrei. Alfaxalone, dexmedetomidine, hydromorphone, ketamine and tribromoethanol were administered subcutaneously (SC), either alone or combined at varying doses in a total of 64 female anoles. Drug induction time, duration, anesthesia level and adverse effects were assessed. Differences in anesthesia level were observed depending on injection site and drug combination. Alfaxalone/dexmedetomidine and tribromoethanol/dexmedetomidine were the most effective drug combinations for inducing a surgical plane of anesthesia in anoles. Brown anoles injected SC with alfaxalone (30 mg/kg) plus dexmedetomidine (0.1 mg/kg) or with tribromoethanol (400 mg/kg) plus dexmedetomidine (0.1 mg/kg) experienced mean durations of surgical anesthesia levels of 31.2 ± 5.3 and 87.5 ± 19.8 min with full recovery after another 10.9 ± 2.9 and 46.2 ± 41.8 min, respectively. Hydromorphone given with alfaxalone/dexmedetomidine resulted in deep anesthesia with respiratory depression, while ketamine/hydromorphone/dexmedetomidine produced only light to moderate sedation. We determined that alfaxalone/dexmedetomidine or tribromoethanol/dexmedetomidine combinations were sufficient to maintain a lizard under general anesthesia for coeliotomy. This study represents a significant step towards understanding the effects of anesthetic agents in anole lizards and will benefit both veterinary care and research on these animals.

Autonomic control of cardiovascular adjustments associated with orthostasis in the scansorial snake Boa constrictor

Orthostatic hypotension is a phenomenon triggered by a change in the position or posture of an animal, from a horizontal to a vertical head-up orientation, characterised by a blood pooling in the lower body and a reduction in central and cranial arterial blood pressure (P _A). This hypotension elicits systemic vasoconstriction and tachycardia, which generally reduce blood pooling and increase P _A Little is known about the mediation and importance of such cardiovascular adjustments that counteract the haemodynamic effects of orthostasis in ectothermic vertebrates, and some discrepancies exist in the information available on this subject. Thus, we sought to expand our knowledge on this issue by investigating it in a more elaborate way, through an in vivo pharmacological approach considering temporal circulatory changes during head-up body inclinations in unanaesthetised Boa constrictor To do so, we analysed temporal changes in P _A, heart rate (f _H) and cardiac autonomic tone associated with 30 and 60 deg inclinations, before and after muscarinic blockade with atropine, double blockade with atropine and propranolol, and α₁-adrenergic receptor blockade with prazosin. Additionally, the animals' f _H variability was analysed. The results revealed that, in B. constrictor: (1) the orthostatic tachycardia is initially mediated by a decrease in cholinergic tone followed by an increase in adrenergic tone, a pattern that may be evolutionarily conserved in vertebrates; (2) the orthostatic tachycardia is important for avoiding an intense decrease in P _A at the beginning of body inclinations; and (3) α₁-adrenergic orthostatic vasomotor responses are important for the maintenance of P _A at satisfactory values during long-term inclinations.

Pharmacokinetics of subcutaneously administered hydromorphone in bearded dragons (Pogona vitticeps) and red-eared slider turtles (Trachemys scripta elegans)

OBJECTIVE

To determine pharmacokinetic dosing strategy in bearded dragons (Pogona vitticeps) and red-eared sliders (Trachemys scripta elegans) based on two subcutaneously (SC) administered doses of hydromorphone (0.5 and 1.0 mg kg^-1).

STUDY DESIGN

Randomized crossover study.

ANIMALS

Six healthy adult bearded dragons, seven healthy adult red-eared slider turtles.

METHODS

Hydromorphone (0.5 and 1.0 mg kg^-1; 2 mg mL^-1) was administered SC dorsolateral to the scapulae in the bearded dragons and between the head and thoracic limb of the red-eared slider turtles. Blood was collected for hydromorphone plasma concentration analysis from the ventral tail vein in bearded dragons and subcarapacial sinus in turtles before (time 0) hydromorphone administration and at 0.5, 1, 6, 12 and 24 hours.

RESULTS

The half-life of hydromorphone administered at 0.5 and 1.0 mg kg^-1 was 2.54 and 3.05 hours in bearded dragons and 2.67 and 2.01 hours in red-eared sliders, respectively. The maximum plasma concentrations for 0.5 and 1.0 mg kg^-1 were 142 and 369 ng mL^-1 in bearded dragons and 1610 and 5142 ng mL^-1 in red-eared sliders, respectively. Peak plasma concentrations were detected at 30 minutes for both species. Hydromorphone administered at both dosages provided plasma concentrations of 13-14 ng mL^-1 for at least 24 hours in bearded dragons and of 5-6 ng mL^-1 for at least 12 hours in red-eared sliders. Clinical sedation was observed for up to 1 hour posthydromorphone (1.0 mg kg^-1) administration for five of six bearded dragons characterized by low body carriage and decreased response to stimuli. No evidence of clinical sedation was observed in red-eared sliders at either dose.

CONCLUSIONS AND CLINICAL RELEVANCE

Recommended dosing strategy for hydromorphone is 0.5 mg kg^-1 administered SC every 24 hours in bearded dragons and every 12-24 hours in red-eared sliders.

A fixed moderate-dose combination of tiletamine+zolazepam outperforms midazolam in induction of short-term immobilization of ball pythons (Python regius)

Laboratory animals are commonly anesthetized to prevent pain and distress and to provide safe handling. Anesthesia procedures are well-developed for common laboratory mammals, but not as well established in reptiles. We assessed the performance of intramuscularly injected tiletamine (dissociative anesthetic) and zolazepam (benzodiazepine sedative) in fixed combination (2 mg/kg and 3 mg/kg) in comparison to 2 mg/kg of midazolam (benzodiazepine sedative) in ball pythons (Python regius). We measured heart and respiratory rates and quantified induction parameters (i.e., time to loss of righting reflex, time to loss of withdrawal reflex) and recovery parameters (i.e., time to regain righting reflex, withdrawal reflex, normal behavior). Mild decreases in heart and respiratory rates (median decrease of <10 beats per minute and <5 breaths per minute) were observed for most time points among all three anesthetic dose groups. No statistically significant difference between the median time to loss of righting reflex was observed among animals of any group (p = 0.783). However, the withdrawal reflex was lost in all snakes receiving 3mg/kg of tiletamine+zolazepam but not in all animals of the other two groups (p = 0.0004). In addition, the time for animals to regain the righting reflex and resume normal behavior was longer in the drug combination dose groups compared to the midazolam group (p = 0.0055). Our results indicate that midazolam is an adequate sedative for ball pythons but does not suffice to achieve reliable immobilization or anesthesia, whereas tiletamine+zolazepam achieves short-term anesthesia in a dose-dependent manner.

Evaluation of sedative and antinociceptive effects of dexmedetomidine, midazolam and dexmedetomidine-midazolam in tegus (Salvator merianae)

OBJECTIVE

To evaluate dexmedetomidine, midazolam and dexmedetomidine-midazolam for sedation and antinociception in tegus.

STUDY DESIGN

Prospective, crossover, randomized, blinded study.

ANIMALS

Six healthy tegus (Salvator merianae) weighing 1.6±0.3 kg.

METHODS

Tegus were administered intramuscularly saline (0.5 mL; CON), dexmedetomidine (0.2 mg kg^-1; DX), midazolam (1 mg kg^-1; MZ) and dexmedetomidine-midazolam (same doses; DM). Heart rate (HR) and respiratory frequency (f_R) were recorded before treatment (baseline) and 15, 30 minutes, 1, 2, 3, 4, 6, 8, 12 and 24 hours after the treatments. Sedation scores were recorded according to resistance to manual restraint, posture and response to noxious stimulus, at baseline and 5, 10, 15, 30 minutes, 1, 2, 3, 4, 6, 8, 12 and 24 hours after the treatments. Antinociception was evaluated by measurement of latency of limb withdrawal reflex (LWR) to thermal stimulus, recorded at baseline and 15 minutes, 1, 2, 4, 8, 12 and 24 hours after the treatments.

RESULTS

Lower HR (DX and DM) and f_R (MZ, DX and DM) than CON were measured 15 minutes after the treatment and for up to 6 hours. Sedation was mild to moderate in MZ, deep in DM and absent in DX, although animals showed behavioral changes in DX, with increase in aggressiveness. Median (interquartile range) duration of sedation were 170 (50; 235) minutes in MZ and 230 (115; 235) minutes in DM. Recovery period was prolonged in both treatments, surpassing the duration of the experiment. Higher LWR than CON was detected from 15 minutes until 12 hours in DX and DM.

CONCLUSIONS AND CLINICAL RELEVANCE

Midazolam provided sedation without antinociception, and dexmedetomidine provided antinociception without sedation. Drug combination increased the duration of sedation but not antinociception. Due to increased duration of sedation, reversal of effects with flumazenil and atipamezole should be considered after conclusion of clinical procedures.

The influence of midazolam on heart rate arises from cardiac autonomic tones alterations in Burmese pythons, Python molurus

The GABA_A receptor agonist midazolam is a compound widely used as a tranquilizer and sedative in mammals and reptiles. It is already known that this benzodiazepine produces small to intermediate heart rate (HR) alterations in mammals, however, its influence on reptiles' HR remains unexplored. Thus, the present study sought to verify the effects of midazolam on HR and cardiac modulation in the snake Python molurus. To do so, the snakes' HR, cardiac autonomic tones, and HR variability were evaluated during four different experimental stages. The first stage consisted on the data acquisition of animals under untreated conditions, in which were then administered atropine (2.5mgkg^-1; intraperitoneal), followed later by propranolol (3.5mgkg^-1; intraperitoneal) (cardiac double autonomic blockade). The second stage focused on the data acquisition of animals under midazolam effect (1.0mgkg^-1; intramuscular), which passed through the same autonomic blockade protocol of the first stage. The third and fourth stages consisted of the same protocol of stages one and two, respectively, with the exception that atropine and propranolol injections were reversed. By comparing the HR of animals that received midazolam (second and fourth stages) with those that did not (first and third stages), it could be observed that this benzodiazepine reduced the snakes' HR by ~60%. The calculated autonomic tones showed that such cardiac depression was elicited by an ~80% decrease in cardiac adrenergic tone and an ~620% increase in cardiac cholinergic tone - a finding that was further supported by the results of HR variability analysis.

The effects of decreased body temperature on the onset, duration and action of medetomidine and its antagonist atipamezole in juvenile farmed estuarine crocodiles (Crocodylus porosus)

OBJECTIVE

To determine the efficacy of medetomidine for immobilisation of captive juvenile crocodiles over a range of temperatures, and its reversibility with atipamezole.

STUDY DESIGN

Prospective experimental study.

ANIMALS

Forty male estuarine crocodiles (body weight 2.0 to 4.8 kg).

METHODS

Each crocodile was randomly assigned to one of four temperature groups: Group 1:32 °C; Group 2:27 °C; Group 3:22 °C; and Group 4:17 °C (n = 10 for each group). Medetomidine (0.5 mg kg(-1) ) was administered intramuscularly (IM) into the thoracic limb of all crocodiles. After 50 minutes, all animals from each group received 2.5 mg kg(-1) atipamezole IM in the opposite thoracic limb and time to recovery was documented. Heart and respiratory rates and the degree of immobilisation were monitored every 5 minutes until recovery, and behaviour monitored for 7 subsequent days.

RESULTS

Onset of immobilisation occurred at 15 ± 10 minutes in Group 1, and at 30 ± 10 minutes in Groups 2 and 3. In Group 4, animals were not immobilised. Recovery following atipamezole was 10 ± 5 minutes at all temperatures. One-way analysis of variance (anova) demonstrated a significant difference in induction times between groups (p < 0.01) but not in recovery times following atipamezole administration (p < 0.25). Heart and respiratory rates decreased markedly following medetomidine administration and increased markedly following atipamezole reversal.

CONCLUSIONS AND CLINICAL RELEVANCE

Medetomidine administered in the thoracic limb of juvenile captive estuarine crocodiles provides profound sedation or immobilisation at temperatures of 22 °C and above. Atipamezole administered in the contralateral thoracic limb results in consistent reversal of the effects of medetomidine and a return to normal behaviour within 15-20 minutes regardless of temperature. Even though immobilisation is not induced at 17 °C, profound reversible sedation does occur reliably and repeatably.

Association of acepromazine with propofol in giant Amazon turtles Podocnemis expansa reared in captivity

PURPOSE

To evaluate the effects of different concentrations of an anesthetic association in giant amazon turtles (Podocnemis expansa).

METHODS

Twenty healthy P. expansa of both sexes weighing between 1.0 and 1.5kg commercially bred in the Araguaia River Valley, Goias, Brazil, were separated into two groups (G1 n=10 and G2 n=10). Each group received a respective protocol: P1= acepromazine (0.5 mg/kg IM) and propofol (5 mg/kg IV) and P2 = acepromazine (0.5 mg/kg IM) and propofol (10 mg/kg IV). The acepromazine was administered in the left thoracic member and the propofol in the cervical vertebral sinus. Assessments were made of the anesthetic parameters of locomotion, muscle relaxation, response to pain stimuli in the right thoracic and pelvic members and heartbeat.

RESULTS

The anesthetic induction time was the same for both protocols (P1 and P2); however the P2 effects were of a longer duration.

CONCLUSION

The sedation achieved with both protocols (P1 and P2) were satisfactory for the biological sample collection, physical examinations and minor surgeries on this species.

Preliminary studies of chemical immobilization of captive juvenile estuarine (Crocodylus porosus) and Australian freshwater (C. johnstoni) crocodiles with medetomidine and reversal with atipamezole

OBJECTIVE

To establish a safe, reliable and reversible immobilization protocol for captive juvenile crocodiles.

STUDY DESIGN

Prospective, randomized, clinical study.

ANIMALS

Thirty male estuarine crocodiles (body mass 1-12.1 kg) and 10 male Australian freshwater crocodiles (body mass 4.1-12.8 kg).

METHODS

An optimized dose of medetomidine (0.5 mg kg(-1)) was administered intramuscularly (IM) into the tail (Group 1; n = 5), pelvic limb (Group 2; n = 5) and thoracic limb (Groups 3 and 4; n = 5 in each group) of estuarine crocodiles weighing 3-12.1 kg. Their heart and respiratory rates and degree of immobilization were monitored every 15 minutes until recovery and daily thereafter for 3 subsequent days. In Group 4 (n = 5), medetomidine was antagonized with an optimized dose of atipamezole (2.5 mg kg(-1)) given IM into the thoracic limb and time to recovery recorded. The effects of increasing doses of medetomidine given IM in the thoracic limb (n = 4) and intravenously (n = 6) were determined in 1-2 kg estuarine crocodiles. Australian freshwater crocodiles (4.1-12.8 kg) were administered medetomidine IM into the thoracic limb in divided doses at 0.5 mg kg(-1) (n = 5) and 0.75 mg kg(-1) (n = 5) and similarly monitored.

RESULTS

Immobilization was achieved only in the estuarine crocodiles >3 kg and when medetomidine was administered into the thoracic limb. Immobilization was achieved within 30 minutes and the duration of immobilization lasted approximately 90 minutes. Immobilization in estuarine crocodiles was readily reversed with atipamezole. A dose of 0.75 g kg(-1) was required to immobilize Australian freshwater crocodiles and the onset of immobilization was longer and the duration shorter than seen in the estuarine crocodiles. The heart and respiratory rates of all immobilized animals decreased significantly and arterial blood pressure became undetectable in the animals in which it was measured.

CONCLUSIONS AND CLINICAL RELEVANCE

Medetomidine administered in the thoracic limb of captive estuarine and Australian freshwater crocodiles, ranging from 3 to 12.8 kg, provides a predictable onset and duration of immobilization sufficient for physical examination, sample collection, short minor procedures and translocation of the animals. Atipamezole administered in the thoracic limb results in complete reversal of the effects of medetomidine in the estuarine crocodile and a rapid return to normal behaviour.

Clinical and histologic effects of intracardiac administration of propofol for induction of anesthesia in ball pythons (Python regius)

OBJECTIVE

To assess the clinical differences between induction of anesthesia in ball pythons with intracardiac administration of propofol and induction with isoflurane in oxygen and to assess the histologic findings over time in hearts following intracardiac administration of propofol.

DESIGN

Prospective randomized study.

ANIMALS

30 hatchling ball pythons (Python regius).

PROCEDURES

Anesthesia was induced with intracardiac administration of propofol (10 mg/kg [4.5 mg/lb]) in 18 ball pythons and with 5% isoflurane in oxygen in 12 ball pythons. Induction time, time of anesthesia, and recovery time were recorded. Hearts from snakes receiving intracardiac administration of propofol were evaluated histologically 3, 7, 14, 30, and 60 days following propofol administration.

RESULTS

Induction time with intracardiac administration of propofol was significantly shorter than induction time with 5% isoflurane in oxygen. No significant differences were found in total anesthesia time. Recovery following intracardiac administration of propofol was significantly longer than recovery following induction of anesthesia with isoflurane in oxygen. Heart tissue evaluated histologically at 3, 7, and 14 days following intracardiac administration of propofol had mild inflammatory changes, and no histopathologic lesions were seen 30 and 60 days following propofol administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Intracardiac injection of propofol in snakes is safe and provides a rapid induction of anesthesia but leads to prolonged recovery, compared with that following induction with isoflurane. Histopathologic lesions in heart tissues following intracardiac injection of propofol were mild and resolved after 14 days.

Improved procedure for implanting radiotransmitters in the coelomic cavity of snakes

OBJECTIVE

To investigate the expulsion of radiotransmitters in snakes and modify the surgical technique for coelomic implantation to prevent its occurrence.

DESIGN

To enable monitoring of snakes for an ecological study, radiotransmitters were implanted in 23 south-west carpet pythons (Morelia spilota imbricata) using the standard surgical technique. In a further 23 pythons we used a refinement of the technique, which anchored the tracking device, using non-dissolvable sutures, to the snake's rib-cage. We also investigated the potential mechanisms for expelling the radiotransmitters in one snake that underwent an exploratory coeliotomy.

RESULTS

Of the initial group of snakes, 12 (52%) expelled the radiotransmitter between 4 days and 3 years post implantation. In the later group, which underwent the refined technique of implantation, none of the radiotransmitters was expelled and no adverse responses were observed.

CONCLUSION

An appropriately sized radiotransmitter anchored to the rib-cage of the snake will prevent expulsion of the device and appears to be well tolerated. Non-attachment of the tracking device enables it to migrate along the length of the body, particularly during feeding and reproduction. Caudal positioning of the transmitter's antenna provides a possible pathogenesis for expulsion into the cloaca.

Pain and analgesia in domestic animals

The biggest challenge to the use of analgesic agents in animals is the determination of the efficacy of these agents. In humans, the verbal communication of the alleviation of pain is fundamental to the effective use of analgesics. In animals, the lack of verbal communication not only confounds the diagnosis and characterisation of the experience of pain, but also challenges the evaluation of the analgesic therapy. As animals possess the same neuronal pathways and neurotransmitter receptors as humans, it seems reasonable to expect that their perceptions of painful stimuli will be similar, and this is a basis for the use of laboratory animals for screening of analgesics for human use. However, as the evaluation in the laboratory animal tests is based mainly on behavioural responses, and although some physiological responses do occur, it is often difficult to separate these from stress responses. The use of behavioural responses to evaluate analgesics in a range of species is complicated by the fact that different species show different behaviours to a similar pain stimulus, and different pain stimuli produce different pain responses in the same species. Thus behaviours may be species- and pain-specific and this can complicate analgesic evaluation. As most animals possess similar neuronal mechanisms to humans for pain perception, it is not surprising that the standard human pain control strategies can be applied to animals. For instance, local anaesthetics, opioids, non-steroidal anti-inflammatory drugs (NSAIDs), as well as other analgesics used in humans are all found to be effective for animal use. Differences in metabolism and distribution between various species, as well as financial considerations in larger animals can affect efficacy and thus limit their use. In addition, the use of any drug in a species that may be intended for human consumption will be limited by residue considerations. The treatment of pain in animals presents many challenges, but the increasing public concerns regarding animal welfare will ensure that studies into the nature and control of animal pain will continue to have a high profile.

Influência da temperatura corporal de cascavéis (Crotalus durissus) submetidas à anestesia com cetamina

O estudo objetivou verificar a influência da temperatura corporal nos parâmetros fisiológicos e nos períodos de indução e recuperação anestésicos de cascavéis (Crotalus durissus) anestesiadas com cetamina. Os animais foram previamente submetidos à hipotermia (HIPO) (<22°C) e normotermia (30°C) (NORMO) e anestesiados com 80mg/kg IM de cetamina. Foram avaliados os períodos de latência e recuperação da anestesia por meio do tônus de cabeça, tônus muscular e reflexo de endireitamento. Mensurou-se a frequência cardíaca (FC), tempo de apnéia e temperatura corporal em 0 min e 5, 10, 15, 30, 60, 90, 120 min e análise dos gases sanguíneos em 0 min, 30 e 60 min. Não houve diferença em relação ao período de latência entre os grupos. A recuperação dos animais em HIPO foi mais prolongada (5,5 horas) que em NORMO (3,5 horas). Obteve-se FC no grupo NORMO superior que no grupo HIPO. O tempo de apnéia manteve o mesmo padrão em ambos os grupos. Em relação ao basal, tanto em HIPO quanto em NORMO o tempo de apnéia diminuiu acentuadamente entre 5 e 30 min. Observou-se acidose respiratória no grupo NORMO apenas em 0 min. O SvO2 elevou-se significativamente após 30 min, o mesmo ocorrendo com a PvO2. A PvCO2 diminuiu em ambos os grupos após 30 min. Evidenciou-se que a temperatura corporal influencia intrinsecamente o período de recuperação de cascavéis anestesiadas com cetamina.

Emergency care of reptiles

Most reptile emergencies are the result of improper husbandry and nutrition. Reptiles are good at masking disease, and owners, failing to recognize early signs of illness, only seek veterinary assistance when issues are advanced and near terminal. The veterinarian should be familiar with reptile species-specific husbandry and nutritional requirements and basic clinical techniques. The same principles and techniques used in small animal medicine can be applied to reptile emergencies. This article reviews general emergency principles that apply to the reptilian patient and common emergency presentations. The main areas of discussion focus on cardiopulmonary resuscitation, fluid therapy, and analgesia.