Physiological and biochemical variables in captive tigers (Panthera tigris) immobilised with dexmedetomidine and ketamine or dexmedetomidine, midazolam and ketamine

SERIAL CHANGES IN METABOLIC ACID-BASE STATUS IN THREE SPECIES OF ANESTHETIZED CAPTIVE LARGE FELID

Determination of acid-base status contributes important information about patient health, including for patients under anesthesia. There is a paucity of information about the determinants of acid-base status of large felids managed under anesthesia, and advancement of such knowledge may contribute to patient safety. This study serially monitored the individual metabolic acid-base status of 11 large felids, including lions (Panthera leo), tigers (Panthera tigris), and cheetahs (Acinonyx jubatus), under general anesthesia. We analyzed the contributions of measured strong ions (sodium, chloride, potassium, lactate), weak acids and buffers (albumin, phosphate and bicarbonate), and unmeasured anions to standardized extracellular base excess (SBE). A general linear model assessed for species differences in these parameters, with time since immobilization, SBE, and mean arterial pressure as covariates. By employing a Stewart-based analytical approach, it was possible to separate chloremic and unmeasured anion contributions to metabolic acid base status. This provided a basis for identifying mixed metabolic processes, generating differentials for underlying causes. Using normal acid base parameters for domestic felids, metabolic acidosis was found to be prevalent. Frequent evidence of unmeasured anion accumulation was also found, with unmeasured anions occasionally exceeding 5mmol/L. These findings warrant further inquiry into the drivers and clinical significance of metabolic acidosis and unmeasured anion accumulations in anesthetized large felids, encouraging further anion identity studies to elucidate possible causes. Reference ranges need to be established for acid-base parameters in large felids as a foundation for interpreting more controlled, prospective research into determinants of metabolic acid-base status in these animals under anesthesia.

Dexmedetomidine and ketamine simultaneous administration in tigers (Panthera tigris): pharmacokinetics and clinical effects

Background

The study determines the pharmacokinetic profiles of dexmedetomidine (DEX), ketamine (KET) and its active metabolite, norketamine (NORKET), after simultaneous administration. Moreover, the study evaluates the sedative effects of this protocol, its influence on the main physiological variables and the occurrence of adverse effects.

Methods

Eighteen captive tigers were initially administered with a mixture of DEX (10 µg/kg) and KET (2 mg/kg) by remote intramuscular injection. In case of individual and specific needs, the protocol was modified and tigers could receive general anaesthesia, propofol or additional doses of DEX and KET.

Results

Based on the immobilisation protocol, nine animals were assigned to the standard protocol group and the other nine to the non-standard protocol group. Higher area under the first moment curve (AUMC_0-last) and longer mean residence time (MRT_0-last) (P<0.05) were observed in the non-standard protocol group for DEX, KET and NORKET, and higher area under the concentration-time curve from administration to the last measurable concentration (AUC_0-last) only for KET. The KET metabolisation rate was similar (P=0.296) between groups. No differences between groups were detected in terms of stages of sedation and recoveries. All physiological variables remained within normality ranges during the whole observation period. During the hospitalisation period, no severe adverse reactions and signs of resedation were observed.

Conclusion

The simultaneous administration of 10 µg/kg of DEX and 2 mg/kg of KET can be considered an effective protocol for chemical immobilisation of captive tigers, along with dosage adjusments or when other drugs are needed.

Systemic arterial hypertension secondary to chronic kidney disease in two captive-born large felids

Systemic arterial hypertension (SHT) has been widely described in the domestic cat (Felis catus). In these feline patients, SHT is considered as the most common vascular disorder of middle-aged to older animals, and secondary SHT related to chronic kidney disease (CKD) represents the most common form of the disease. We describe here the first two cases of spontaneous SHT in large felids, i.e. one 18-year old, 34.4 kg, male North-Chinese leopard (Panthera pardus japonensis, case #1) and one 20-year old, 28.7 kg, female snow leopard (Panthera uncia, case #2), both captive-bred and previously diagnosed with CKD. Both animals underwent complete echocardiographic examination under general anesthesia due to abnormal cardiac auscultation (heart murmur and/or gallop sound), and recurrent lethargy in case #1. The combination of left ventricular remodeling with moderate aortic regurgitation of high velocity was highly suggestive of SHT, which was confirmed by indirect blood pressure measurement (systolic arterial blood pressure of 183 mmHg for case #1 and 180 mmHg for case #2). Amlodipine was prescribed (0.35-0.70 mg/kg/day orally) for 31 and 6 months respectively after the initial diagnosis. In case #1, concurrent amlodipine and benazepril treatment was associated with decreased heart murmur grade and reduced aortic insufficiency severity. These reports illustrate that, similarly to domestic cats, SHT should be suspected in old large felids with CKD and that amlodipine is a well-tolerated antihypertensive drug in these species.