Impact of procedural handling on the physiological effects of alfaxalone anaesthesia in the ball python (Python regius)

To describe the cardiovascular changes following intramuscular (handled) and intravascular (undisturbed, via intraarterial catheter) alfaxalone administration, we studied 20 healthy ball pythons (Python regius) in a randomised, prospective study. The pythons were instrumented with occlusive arterial catheters to facilitate undisturbed, continuous monitoring of heart rate and blood pressure. Six pythons were administered intramuscular (IM) saline, followed by 20 mg/kg IM alfaxalone, and were manually restrained for both injections. Six pythons received intraarterial (IA) saline, followed by 10 mg/kg IA alfaxalone, and remained undisturbed for both injections. Arterial blood samples were taken at 0, 12 and 60 min post-injection, and heart rate and blood pressure were recorded for 60 min. The remaining eight snakes received 20 mg/kg IM or 10 mg/kg IA alfaxalone (n = 4 per treatment) and were not handled for intubation 10 min post-injection, to examine the effects of handling during anaesthesia. IM administration of 20 mg/kg alfaxalone or an equivalent volume of saline elicited a profound tachycardia and hypertension, which recovered to resting values after 20 min. However, when 10 mg/kg alfaxalone or saline were injected IA, mild hypotension and a lower magnitude tachycardia occurred. Arterial PCO2 and PO2, pH and lactate concentrations did not change following IA alfaxalone, but an acidosis was observed during IM alfaxalone anaesthesia. There were no significant changes in plasma catecholamines and corticosterone among treatments. Handling for injection and during anaesthesia associated with intubation significantly affects cardiovascular parameters, whereas alfaxalone per se only elicits minor changes in cardiovascular physiology.

Retrospective evaluation of intravenous catheterization in client-owned lizards at a veterinary teaching hospital: 21 cases (2018-2021)

OBJECTIVE

To assess the prevalence of lizards presenting to a university teaching hospital that had an IV catheter placed, the catheterization sites used, and complications arising with the placement of the catheter both in the short and long term.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

ANIMALS

Twenty-one lizards, including inland bearded dragons (Pogona vitticeps; 15/21), green iguanas (Iguana iguana; 4/21), and veiled chameleons (Chamaeleo calyptratus; 2/21).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 129 lizard consultations performed between September 27, 2018 and September 27, 2021, 21 catheters were placed, resulting in an overall prevalence of 16.3%. Reasons for catheter placement included hospitalization for fluid therapy (10/21 [47.6%]), anesthesia or surgery ± hospitalization (7/21 [33.3%]), computed tomography scan with contrast (2/21 [9.5%]), euthanasia only (1/21 [4.8%]), and CPR only (1/21 [4.8%]). All catheters were placed in the ventral coccygeal vein via a ventral approach. Sedation was used in 6 of 21 (28.6%) of the catheters placed. Seven of the catheters (35%) were used for administration of fluids only, 4 (20%) were used for administering drugs/medications only, and 9 (45%) catheters administered both fluids and drugs/medications. No complications were noticed in any of the lizards that had catheters placed, both in the short and long term.

CONCLUSIONS

Based on the retrospective evaluation of medical records at a veterinary teaching hospital, IV catheter placement in lizards is feasible, including in conscious animals, with roughly 1 consultation out of 6 resulting in a catheter placed. The most frequent reason for catheter placement was for administration of fluids.

Heart Diseases in Reptiles: Diagnosis and Therapy

The notion that poikilotherms do not suffer from cardiovascular conditions is being increasingly challenged as diagnostic tools used in companion animal practice are applied to reptiles. However, the cause, diagnosis, and treatment of cardiac conditions in reptiles is difficult because of the scarcity of published literature. Auscultation, electrocardiography, radiography, and ultrasonography are helpful diagnostic techniques in herpetologic practice. Although the pharmacokinetics and pharmacodynamics of cardiovascular drugs are poorly understood in these animals, basic principles remain applicable; these include pharmacologic and nonpharmacologic interventions. Further research is needed to establish species-specific cardiac reference ranges and evidence-based treatment options.

Congestive heart failure in a veiled chameleon (Chamaeleo calyptratus): A case report

A two-year-old male veiled chameleon (Chamaeleo calyptratus) was referred for a gular oedema and bilateral blepharoedema. The echocardiography revealed a ventricular hypertrophy, pericardial effusion, and valvular regurgitation of the right atrioventricular valve. Treatment with hydrochlorothiazide, enalapril, and carvedilol was commenced. Within 3 weeks of treatment, the valvular regurgitation was noticeably decreased. In the 4th week of treatment, the echocardiography revealed a reduction in the myocardium hypertrophy. After an additional month of home treatment, the patient was presented with anorexia and decreased activity. Despite the supportive care, the patient died. The histopathology revealed mild to moderate fibrosis of the epicardium. Moderate to severe fibrosis, degeneration of the myofibrils, fatty atrophy, interstitial oedema and mild calcification was seen in the atria. The tunica intima, media and adventitia of the major cardiac vessels were moderately fibrotic, swollen and interfused by myxoedema. The kidney histopathology revealed moderate sclerosis and atrophy of the glomeruli, vacuolation of the tubular epithelium, fibrosis, and infiltration of the leucocytes in the interstitium. The therapeutic protocol with hydrochlorothiazide, ACE inhibitor enalapril and β-blocker carvedilol reduced the myocardium hypertrophy and the valvular regurgitation; however, the prolonged use of diuretics jeopardized the renal function in our patient. Frequent blood analyses are necessary using diuretics in reptile patients.

Sedation and Anesthesia of Lizards

The field of lizard sedation, anesthesia, and locoregional anesthesia is advancing with new drug protocols being evaluated, and new locoregional techniques being developed and evaluated. Inducing and maintaining effective and safe chemical restraint in lizards can be challenging, particularly in systemically diseased individuals. Understanding the anatomic and physiologic adaptations of lizards, using reversible or partially reversible injectable protocols, and using locoregional anesthesia may increase the quality of chemical restraint, facilitate faster recoveries, and limit anesthesia-related morbidity and mortality.

Pharmacodynamics of propofol and alfaxalone in rattlesnakes (Crotalus durissus)

To characterise the effect of two common induction agents, propofol and alfaxalone, on mean arterial blood pressure (MAP) and heart rate (HR), we equipped 19 adult South American rattlesnakes (Crotalus durissus) with an indwelling arterial catheter approximately 24 h prior to recording of baseline resting values. Then, seven snakes received alfaxalone (15 mg kg^-1) intravascularly (IV) through the catheter, while groups two and three (both n = 6) received propofol (15 mg kg^-1 IV). The first two groups were not handled, while the group 3 was manually restrained for 2 min for a mock injection of 0.2 ml saline into the ventral tail vein. Baseline HR was similar in all groups and handling caused a significant tachycardia (p = 0.031) in group three. When given IV to undisturbed animals, both propofol and alfaxalone induced a significant increase in HR (p = 0.0022 and p = 0.0045, respectively) lasting approximately 30 min, but with values only significantly exceeding baseline for the first 5 min for propofol and the first 10 min with alfaxalone. Handling caused a significant increase in MAP (p = 0.0313). Propofol did not affect MAP (p = 0.1064), while alfaxalone caused a marked hypertension (although only significant at 2 min; p = 0.031). Manual restraint significantly increases both HR and MAP, which may lead to a masking of true cardiovascular effects of anaesthetic agents.

Proximal duodenoileal anastomosis for treatment of small intestinal obstruction and volvulus in a green iguana (Iguana iguana)

CASE DESCRIPTION A 13-year-old female green iguana (Iguana iguana) was examined because of a 6-day history of vomiting, anorexia, and lethargy and a 4-day history of decreased fecal and urate output. CLINICAL FINDINGS Physical examination revealed a distended abdomen, signs of depression, pallor, tachycardia, harsh lung sounds, and vomiting. Abdominal radiographs revealed gas distention of the stomach and small intestine with fluid lines evident on the lateral view. Plasma biochemical analysis indicated hypochloremic metabolic alkalosis, hyperglycemia, and hyperuricemia. TREATMENT AND OUTCOME Exploratory laparotomy confirmed a diagnosis of small intestinal entrapment and 170° volvulus involving approximately 80% (20 to 30 cm) of the small intestine. The portion of the small intestine extending from the middle portion of the duodenum to the caudal extent of the ileum was resected, and end-to-end anastomosis of the remaining small intestine was performed. The iguana recovered without apparent complications and was reportedly doing well 1 year after surgery. CLINICAL RELEVANCE Findings suggested that iguanas, as hindgut fermenters, may tolerate > 70% resection of the small intestine with a good outcome and no clinical evidence of residual gastrointestinal dysfunction.

ANESTHETIC INDUCTION AND RECOVERY PARAMETERS IN BEARDED DRAGONS (POGONA VITTICEPS): COMPARISON OF ISOFLURANE DELIVERED IN 100% OXYGEN VERSUS 21% OXYGEN

Inland bearded dragons (Pogona vitticeps, n=6) were anesthetized for 1 hr using isoflurane in either 100% oxygen or 21% oxygen (FI 21; medical-grade room air). Parameters of anesthetic depth were recorded throughout both induction and recovery by an observer blinded to the fraction of inspired oxygen (FiO2), including the loss and return of withdrawal and righting reflexes, muscle tone, ability to intubate or extubate, and return to spontaneous respiration. Physiologic data were recorded every 5 min throughout the anesthetic procedures, including heart rate, body temperature, end-tidal CO2, hemoglobin oxygen saturation (SpO2), and percent expired isoflurane. Lizards were subjected to application of a noxious stimulus (needle stick) at 0, 30, and 60 min, and responses recorded. Following a minimum 7-day washout period, the experiment was repeated with each lizard subjected to the other protocol in a randomized, complete crossover design. The only statistically significant difference was a lower mean SpO2 in the group inspiring 21% oxygen (P<0.0020). No statistically significant differences were detected in any parameters during induction or recovery; however, all values were uniformly shorter for the FI 21 group, indicating a possible clinically significant difference. A larger sample size may have detected statistically significant differences. Further studies are needed to evaluate these effects in other reptile species and with the concurrent use of injectable anesthetic and analgesic drugs.