Xylazine-midazolam-ketamine versus medetomidine-midazolam-ketamine anesthesia in captive Siberian tigers (Panthera tigris altaica)

Perioperative dobutamine infusion in an African lion (Panthera leo)

Laparoscopic ovariectomy under general anesthesia was planned in a 10-year-old, 146 kg, apparently healthy female African lion (Panthera leo). The lion was immobilized via intramuscular darts containing midazolam (0.033 mg/kg), medetomidine (50 µg/kg) and ketamine (2.5 mg/kg), and intubated using an endotracheal tube (16 mm internal diameter). The anesthesia was maintained using sevoflurane (0.9-2.1% end-tidal concentration), in combination with remifentanil (0.1 µg/kg/min) and ketamine (11 µg/kg/min) at a constant rate infusion (CRI), with Hartmann's solution (5 mL/kg/hr). Surgery was conducted with stable vital signs, but hypotension (mean arterial blood pressure 55 mmHg) developed, requiring dobutamine treatment. The hypotension was effectively controlled by adjusting dobutamine from 5 µg/kg/min to 0.2 to 0.3 µg/kg/min. This case suggests possibilities that dosages in this range can be clinically useful for peri-anesthetic hypotension in lions.

Comparison of the cardiovascular effects of immobilization with three different drug combinations in free-ranging African lions

Thirty-six free-ranging lions (12 per group) were immobilized with tiletamine-zolazepam (Zoletil 0.6 mg/kg i.m.) plus medetomidine (0.036 mg/kg i.m.) (TZM), ketamine (3.0 mg/kg i.m.) plus medetomidine (0.036 mg/kg i.m.) (KM) or ketamine (1.2 mg/kg i.m.) plus butorphanol (0.24 mg/kg i.m.) plus medetomidine (0.036 mg/kg i.m.) (KBM). During immobilization cardiovascular variables were monitored at 5-minute intervals for a period of 30 minutes. Lions immobilized with all three drug combinations were severely hypertensive. Systolic arterial pressure was higher at initial sampling in lions immobilized with KM (237.3 ± 24.8 mmHg) than in those immobilized with TZM (221.0 ± 18.1 mmHg) or KBM (226.0 ± 20.6 mmHg) and decreased to 205.8 ± 19.4, 197.7 ± 23.7 and 196.3 ± 17.7 mmHg, respectively. Heart rates were within normal ranges for healthy, awake lions and decreased throughout the immobilization regardless of drug combination used. Lions immobilized with TZM had a higher occurrence (66%) of skipped heart beats than those immobilized with KBM (25%). The three drug combinations all caused negative cardiovascular effects, which were less when KBM was used, but adverse enough to warrant further investigations to determine if these effects can be reversed or prevented when these three combinations are used to immobilize free-living lions.

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.

Effect of Intramuscular Medetomidine Administration on Tear Flow in Rats

Medetomidine has been reported to decrease tear flow significantly in dogs, cats, and pigs when used as a sedative or analgesic; however, there are no such reports when it comes to rats. The present study aimed to investigate the effect of medetomidine on tear flow in rats. Medetomidine in doses of 50, 100, or 200 µg/kg or a physiological saline solution as the control, were administered intramuscularly to male Slc:Wistar/ST rats. After the administration of medetomidine, tear flow in both eyes was measured using a phenol red thread tear test. The area under the curve (AUC) of phenol red thread test values from baseline to 8 h was calculated. Data were plotted against the dose of medetomidine and simple linear regression analysis was performed. The effect of the drug on phenol red thread test values was considered dose-related when linear analysis yielded a significant relationship. In all medetomidine-treated groups, tear flow decreased significantly in both eyes after administration, while no significant changes were observed in either eye in the control group. The AUC values from baseline to 8 h after administration in groups treated with 100 and 200 µg/kg of medetomidine were significantly lower in both the left and right eyes compared to the control group. The linear regression of the AUC values was significant for both eyes. Our results indicated that the intramuscular administration of medetomidine in rats decreased tear flow significantly in a dose-dependent manner.

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

Physiological and biochemical variables in captive tigers (Panthera tigris) immobilised with dexmedetomidine and ketamine or dexmedetomidine, midazolam and ketamine were evaluated. Thirty tigers received either dexmedetomidine (0.025 mg/kg) and ketamine (3 mg/kg) (group DK) or dexmedetomidine (0.0125 mg/kg), midazolam (0.1 mg/kg) and ketamine (3 mg/kg) (group DMK). Heart rate, SPO2 and blood pressure were measured at five-minute intervals. Arterial pH, PO2, PCO2, glucose, K+ and arterial and venous lactate were measured at 15 and 45 minutes after immobilisation. A generalised linear mixed model was used for statistical comparison. There was no difference within or between groups at any time point for any measured variable. Measured PO2 was 73.2±17.5 mm Hg and SPO2 was 88.9±10.8 per cent. Systolic, mean and diastolic blood pressures were 170.5±48.4, 138.9±41.8 and 121.8±37.2 mm Hg, respectively. Venous lactate was higher than arterial lactate within groups at each time point. Seizure-like behaviour was observed in 25 per cent of tigers in group DK but not in group DMK. The addition of midazolam into a protocol for immobilisation of tigers did not result in a difference in any of the measured variables but may have prevented the development of seizure-like behaviour.

Immobilization of captive tigers (Panthera tigris) with a combination of tiletamine, zolazepam, and detomidine

The aims of this study were to evaluate the effects of the administration of a combination of tiletamine-zolazepam and detomidine (TZD) in 9 tigers (Panthera tigris). Nine captive tigers were immobilized with tiletamine-zolazepam and detomidine administered intramuscularly. At the end of the procedure immobilization was partially reversed with atipamezole. Lateral recumbency was achieved in 15.6 ± 5.9 min. The median induction score [scored 1 (excellent) to 4 (poor)] was 1. The immobilization score [scored 1 (poor) to 6 (too deep)] was 5 (4-5) at all study times. After atipamezole administration, all tigers experienced severe ataxia and incoordination. Median recovery score [scored 1 (excellent) to 4 (poor)] was 2.5 (range 2-3). No neurologic and/or important adverse reactions were noticed within 5 days after recovery. The combination tiletamine-zolazepam with detomidine proved to be effective in immobilizing captive healthy tigers but it maybe associated with hypertension and ataxia during recovery. Zoo Biol. 34:40-45, 2015. © 2014 Wiley Periodicals Inc.

Chemical immobilization and anesthesia of free-living aardvarks (Orycteropus afer) with ketamine-medetomidine-midazolam and isoflurane

Abstract We evaluated the effectiveness of a ketamine-medetomidine-midazolam drug combination administered intramuscularly by remote injection followed by isoflurane anesthesia in free-living aardvarks (Orycteropus afer). Seven aardvarks weighing 33-45 kg were immobilized to perform surgical implantation of temperature loggers using 3.8 mg/kg ketamine, 0.1 mg/kg medetomidine, and 0.25 mg/kg midazolam. Immobilized aardvarks were transported to a surgical theater and received 0.5-1% isoflurane in oxygen after tracheal intubation. After surgery, medetomidine was antagonized with 0.5 mg/kg atipamezole, and aardvarks were released at the site of capture. We recorded induction and recovery times, clinical and physiologic parameters, and conducted blood gas analyses before and during isoflurane administration. Aardvarks showed initial effects within 3 min and reached lateral recumbency within 7 min after drug administration. Heart rate (50-67 beats/min), respiratory rate (10-15 breaths/min), oxygen hemoglobin saturation (SaO2; 90-97%), and rectal temperature (34.0-37.5 C) were within acceptable physiologic ranges. Mean arterial blood pressure was initially high (146 ± 12 mmHg), but the hypertension resolved over time. Rectal temperature dropped significantly during anesthesia. Four animals had to be treated to relieve apnea. Blood gas analyses revealed mild to moderate hypercapnia but no hypoxaemia. The ketamine-medetomidine-midazolam combination provided effective immobilization. Combined with a low concentration of isoflurane, it can be used for prolonged surgical procedures in wild aardvarks. However, caution is needed, and monitoring of clinical parameters is required.

Comparison of anesthesia with fully reversible dexmedetomidine-butorphanol-midazolam versus ketamine-midazolam in captive Asian small-clawed otters (Aonyx cinereus)

OBJECTIVE

To evaluate the efficacy and safety of a combination of dexmedetomidine, butorphanol, and midazolam administered IM for anesthesia in captive Asian small-clawed otters (Aonyx cinereus) and to compare this combination with a combination of ketamine and midazolam.

DESIGN

Prospective crossover study.

ANIMALS

10 captive Asian small-clawed otters.

PROCEDURES

A combination of either dexmedetomidine (0.03 mg/kg [0.014 mg/lb]), butorphanol (0.2 mg/kg [0.091 mg/lb]), and midazolam (0.15 mg/kg [0.068 mg/lb]) or ketamine (10.1 mg/kg [4.59 mg/lb]) and midazolam (0.3 mg/kg [0.14 mg/lb]) was administered IM to otters for immobilization to allow scheduled wellness examinations. Otters were intubated and administered 100% oxygen during the examination. Anesthesia was supplemented with isoflurane in oxygen if necessary. Routine medical procedures, including blood collection, radiography, echocardiography, dental scaling, vaccinations, and contraception administration, were performed as indicated during the immobilization. Physiologic, clinicopathologic, and anesthetic variables were recorded and compared. Otters given dexmedetomidine-butorphanol-midazolam were administered atipamezole (0.2 mg/kg [0.091 mg/lb]), naltrexone (0.6 mg/kg [0.27 mg/lb]), and flumazenil (0.05 mg/kg [0.023 mg/lb]) IM at the completion of the examination.

RESULTS

The need for and duration of isoflurane administration were greater for ketamine-midazolam anesthesia, compared with dexmedetomidine-butorphanol-midazolam anesthesia. Recoveries were shorter and subjectively smoother with dexmedetomidine-butorphanol-midazolam. Heart rates were significantly higher during ketamine-midazolam anesthesia. Regardless of protocol, all otters developed hypothermia and hypercapnia during anesthesia.

CONCLUSIONS AND CLINICAL RELEVANCE

Both protocols were safe and effective for this species, but the reversible nature of dexmedetomidine-butorphanol-midazolam resulted in more rapid recoveries than did ketamine-midazolam. Otters anesthetized with ketamine-midazolam may require additional anesthetic medications for routine examinations, and assisted ventilation and thermal support may be of benefit with either protocol.

Anaesthetic management of two Bengal tiger (Panthera tigris tigris) cubs for fracture repair

This case series describes the anaesthetic management of two sibling Bengal tiger (Panthera tigris tigris) cubs that were found to have spontaneous femur fractures due to severe nutritional secondary hyperparathyroidism. Both cubs received a combination of medetomidine (25 µg/kg) and ketamine (4 mg/kg) intramuscularly and were maintained with isoflurane in oxygen. An epidural injection of morphine (0.1 mg/kg) and ropivacaine (1.6 mg/kg) was administered to both tigers, which allowed a low end-tidal isoflurane concentration to be maintained throughout the femur fracture reduction operations. Both cubs experienced profound bradycardia and hypotension during general anaesthesia, and were unresponsive to anticholinergic treatment. Possible causes for these cardiovascular complications included: drug pharmacodynamics (medetomidine, morphine, isoflurane), decreased sympathetic tone due to the epidural (ropivacaine) and hypothermia. These possible causes are discussed in detail.

Immobilization of grizzly bears (Ursus arctos) with dexmedetomidine, tiletamine, and zolazepam

Safe and effective immobilization of grizzly bears (Ursus arctos) is essential for research and management. Fast induction of anesthesia, maintenance of healthy vital rates, and predictable recoveries are priorities. From September 2010 to May 2012, we investigated these attributes in captive and wild grizzly bears anesthetized with a combination of a reversible α2 agonist (dexmedetomidine [dexM], the dextrorotatory enantiomer of medetomidine) and a nonreversible N-methyl-d-aspartate (NMDA) agonist and tranquilizer (tiletamine and zolazepam [TZ], respectively). A smaller-than-expected dose of the combination (1.23 mg tiletamine, 1.23 mg zolazepam, and 6.04 µg dexmedetomidine per kg bear) produced reliable, fast ataxia (3.7 ± 0.5 min, x̄±SE) and workable anesthesia (8.1 ± 0.6 min) in captive adult grizzly bears. For wild bears darted from a helicopter, a dose of 2.06 mg tiletamine, 2.06 mg zolazepam, and 10.1 µg dexmedetomidine/kg produced ataxia in 2.5 ± 0.3 min and anesthesia in 5.5 ± 1.0 min. Contrary to published accounts of bear anesthesia with medetomidine, tiletamine, and zolazepam, this combination did not cause hypoxemia or hypoventilation, although mild bradycardia (<50 beats per min) occurred in most bears during the active season. With captive bears, effective dose rates during hibernation were approximately half those during the active season. The time to first signs of recovery after the initial injection of dexMTZ was influenced by heart rate (P<0.001) and drug dose (P<0.001). Intravenous (IV) injection of the reversal agent, atipamezole, significantly decreased recovery time (i.e., standing on all four feet and reacting to the surrounding environment) relative to intramuscular injection. Recovery times (25 ± 8 min) following IV injections of the recommended dose of atipamezole (10 µg/µg of dexmedetomidine) and half that dose (5 µg/µg) did not differ. However, we recommend use of the full dose based on the appearance of a more complete recovery. Field trials confirmed that the dexMTZ + atipamezole protocol is safe, reliable, and predictable when administered to wild grizzly bears, especially during helicopter capture operations.

A Comparative Clinical Study of Three Different Dosages of Intramuscular Midazolam?Medetomidine?Ketamine Immobilization in Cats

A low dose of midazolam-medetomidine-ketamine (MMK) combination was evaluated in three increasing dosages. Each of the 18 cats was randomly allocated for several times to one of four groups. Five minutes after premedication with intramuscular (IM) 0.04 mg/kg atropine, group A (n = 43), B (n = 40) and C (n = 28) all were anaesthetized with 0.5 mg/kg midazolam, combined with 10, 20 or 30 microg/kg medetomidine, and 1.0, 2.0 or 3.0 mg/kg ketamine, respectively, IM in one syringe. Group D (n = 11) received the established combination of 50 microg/kg medetomidine and 10.0 mg/kg ketamine for comparison. Because this study was in cooperation with a project on dental prophylaxis, cats had to be immobilized for approximately 1 h. Therefore, anaesthesia was prolonged with propofol to effect, if necessary. Duration of MMK anaesthesia was between 30 +/- 15, 45 +/- 19 and 68 +/- 28 min in groups A, B and C respectively. A significant decrease of respiratory rate was observed with increasing dosage, but venous carbon dioxide (pCO(2)) and pH values in combination with arterial oxygen saturation (SpO(2)) values were not alarming. The diastolic blood pressure particularly showed an increase. MMK combination A showed the best cardiovascular results, but it cannot be recommended due to disadvantages like a long induction time sometimes accompanied by excitations and the short duration of surgical immobilization. Dosage C in contrast had fewer side effects but less favourable cardiovascular results and a longer recovery period. However, either dosage B or C was suitable as a repeatable IM immobilization method for non-invasive procedures in healthy cats.