Recovery of grizzly and American black bears from xylazine, zolazepam, and tiletamine

COMPARISON OF ISOFLURANE GAS VERSUS A GUAIFENESIN, KETAMINE, AND MEDETOMIDINE CONSTANT-RATE INFUSION FOR MAINTENANCE ANESTHESIA IN AMERICAN BLACK BEARS (URSUS AMERICANUS)

Published anesthetic protocols for captive and free-ranging bears are limited to injectable inductions with maintenance via inhalants or additional injectable boluses. Though common in other species, intravenous (IV) continuous-rate infusions (CRI) using guaifenesin combinations have not been evaluated in ursids. This study evaluated the use of a CRI compared to an inhalant for maintenance anesthesia. Seven healthy American black bears (Ursus americanus) were anesthetized in a crossover design with two different anesthetic maintenance protocols. Bears were immobilized with ketamine (2.02 ± 0.14 mg/kg) and medetomidine (0.04 ± 0.003 mg/kg) for both protocols. The anesthetic maintenance control protocol consisted of isoflurane gas (ISO) started at 2% delivered by endotracheal tube; the experimental protocol consisted of guaifenesin, medetomidine, ketamine (GMK) IV CRI started at 50 mg/kg/hr guaifenesin, 0.01 mg/kg/hr medetomidine, and 1 mg/kg/hr ketamine. Induction and recovery parameters including time to first effect, recumbency, and hands on; duration of maintenance protocol; and time from reversals administered to head up, standing on all four feet, no ataxia, and to fully recovered were recorded and compared between protocols. Heart rate, respiratory rate, rectal temperature, blood pressure, end tidal carbon dioxide, and hemoglobin oxygen saturation were recorded at 5-min intervals and compared between protocols. Venous blood gases were obtained at the start, middle, and end of the maintenance anesthesia and compared between protocols. All bears exhibited hypertension with mild respiratory acidosis throughout procedures. Measured physiologic parameters did not differ significantly between the isoflurane and the GMK CRI maintenance protocols, with the exception of higher endpoint (ISO) pCO2 measurements. No adverse events were recorded with either protocol, and adequate depth of anesthesia was maintained with both protocols. GMK CRI provides a safe, effective, and more portable alternative to inhalant anesthetics for maintenance anesthesia in bears in captivity or in the field.

REVIEW OF ANESTHETIC PROTOCOLS IN ANDEAN BEARS (TREMARCTOS ORNATUS), SLOTH BEARS (MELURSUS URSINUS), AND GIANT PANDAS (AILUROPODA MELANOLEUCA) AT THE SMITHSONIAN INSTITUTION'S NATIONAL ZOOLOGICAL PARK, 1995-2016

A review of anesthetic procedures used in Andean bears (Tremarctos ornatus), sloth bears (Melursus ursinus), and giant pandas (Ailuropoda melanoleuca) housed at the Smithsonian Institution's National Zoological Park (NZP) from 1995 to 2016 was performed. A total of 146 anesthetic procedures (55 procedures on 12 Andean bears, 38 procedures on nine sloth bears, and 53 procedures on five giant pandas) occurred at NZP during this time frame. Induction protocols involved some combination of ketamine (K; n = 121), tiletamine-zolazepam (TZ; n = 91), medetomidine (M; n = 67), xylazine (X; n = 42), midazolam (Mid; n = 9), and butorphanol (B; n = 1). The most commonly used protocols were TZKM for both Andean bears (n = 29) and sloth bears (n = 12), and KX in giant pandas (n = 17). Supplemental injections of K, TZ, Mid, or M were required to complete inductions in 66 cases (45%). Anesthetic maintenance was most often completed with isoflurane, ketamine, or propofol. The most commonly reported complications included perianesthetic emesis (n = 47), ptyalism (n = 16), and seizure-like activity (n = 11). The most frequent physiologic findings included low pulse oximetry values (n = 95), bradycardia (n = 95), hypothermia (n = 74), and hypertension (n = 55). Dose ranges, induction, and recovery times, supplementation and complication rates, and physiologic values are reported for each protocol by species.

Prediction of arterial blood gas values from venous blood gas values in Asiatic black bears (Ursus thibetanus) anesthetized with intramuscular medetomidine and zolazepam-tiletamine

The objective of this study was to measure differences between arterial and venous blood gas parameters and to evaluate whether arterial blood gas values can be estimated from venous blood in Asiatic black bears (ABBs). Twelve healthy captive ABBs (8 males and 4 females; 8-16 years; 76.8-220 kg) were included in this study. The bears were immobilized with medetomidine and zolazepam-tiletamine using a dart gun. Arterial and venous samples were collected simultaneously at 5 and 35 min after recumbency (5- and 35-min points). Partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2), pH, bicarbonate (HCO3-), total carbon dioxide (TCO2), oxygen saturation of hemoglobin (SO2) and base excess (BEecf) were analyzed using a portable blood gas analyzer. There was no marked difference in measured and calculated variables over time in both venous and arterial blood except for PO2. However, arterial PO2, SO2 and pH were significantly higher and arterial PCO2, TCO2 and HCO3- were lower than those of venous samples at both 5- and 35-min points. In the regression analysis to estimate arterial values from venous values, PCO2, TCO2, HCO3-, BEecf and pH significantly showed over 0.45 in coefficient of determination value (R2), and there were little differences between actual and predicted arterial values. Although there were limits in venous gas values replaced those of arterial blood, if we could not get the arterial samples, the regression formulas for arterial values from venous blood in this study would be useful clinically, except for PO2 and SO2.

Immobilization of Asiatic Black Bears ( Ursus thibetanus ) with Medetomidine-Zolazepam-Tiletamine in South Korea

The Asiatic black bear ( Ursus thibetanus ; ABB) is a globally endangered species for which a restoration program has been ongoing in South Korea since 2001. However, there is little information on immobilization protocols for ABBs. We evaluated the use of medetomidine-zolazepam-tiletamine for their immobilization. During 2005-13, we anesthetized 60 ABBs (32 males, 28 females; 7 mo to 12 yr old) with medetomidine 0.03-0.045 mg/kg and zolazepam-tiletamine 1.54-2.3 mg/kg; reversal of anesthesia was done with atipamezole 0.15-0.225 mg/kg administered intravenously alone or intravenously and intramuscularly (50:50). Mean (and SD) for physiologic collected for 373 immobilizations of at least 60 min were: time to sedation, 7.8 (5.4) min; anesthesia induction time, 13.7 (8.1) min; complete recovery time, 14.8 (12.4) min; respiratory rate, 14 (7) breaths/min; heart rate, 51 (16) beats/min; rectal temperature, 37.3 (1.3) C; and hemoglobin oxygen saturation, 88% (6%). Few cardiopulmonary side effects occurred during immobilization and adequate depth of anesthesia was maintained for >60 min without need for supplementation. The dosage and drug combination used was effective for immobilization of ABBs with minimal adverse effects on vital signs and can be recommended in most clinical applications.

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.