Nigel A. Caulkett

Physiologic responses of grizzly bears to different methods of capture

The physiologic effects of two methods of capture, chemical immobilization of free-ranging (FR) bears by remote injection from a helicopter and physical restraint (PR) by leg-hold snare prior to chemical immobilization, were compared in 46 grizzly bears (Ursus arctos) handled during 90 captures between 1999 and 2001. Induction dosages and times were greater for FR bears than PR bears, a finding consistent with depletion of, or decreased sensitivity to, catecholamines. Free-ranging bears also had higher rectal temperatures 15 min following immobilization and temperatures throughout handling that correlated positively with induction time. Physically restrained bears had higher white blood cell counts, with more neutrophils and fewer lymphocytes and eosinophils, than did FR bears. This white blood cell profile was consistent with a stress leukogram, possibly affected by elevated levels of serum cortisol. Serum concentrations of alanine aminotransferase, aspartate aminotransferase, and creatine kinase were higher in PR bears that suggested muscle injury. Serum concentrations of sodium and chloride also were higher in PR bears and attributed to reduced body water volume through water deprivation and increased insensible water loss. Overall, different methods of capture resulted in different patterns of physiologic disturbance. Reducing pursuit and drug induction times should help to minimize increase in body temperature and alteration of acid-base balance in bears immobilized by remote injection. Minimizing restraint time and ensuring snare-anchoring cables are short should help to minimize loss of body water and prevent serious muscle injury in bears captured by leg-hold snare.

ANESTHESIA OF POLAR BEARS USING XYLAZINE-ZOLAZEPAM-TILETAMINE OR ZOLAZEPAM-TILETAMINE

Immobilization features and physiologic effects of combinations of xylazine-zolaze-pam-tiletamine (XZT) and zolazepam-tiletamine (ZT or Telazol®) were compared in nine captive and 17 free-ranging polar bears (Ursus maritimus) between 1998 and 2001. Although induction time was similar between drugs, induction dosage and volume were less with XZT. Induction of immobilization with XZT was predictable and smooth, muscle relaxation was good, and all bears remained completely immobilized and unresponsive to stimuli throughout a 1 hr handling period. The combination XZT was safely tolerated at two to three times the recommended dosage of 5 mg/kg (i.e., xylazine at 2 mg/kg + Telazol® at 3 mg/kg). Bears immobilized with XZT had slower pulse rates, higher mean arterial pressures, and lower arterial oxygen tensions than bears immobilized with ZT. Rectal temperature increased slowly over time (∼0.5 C per hr) following immobilization with XZT. Based on response to a painful stimulus (compression of a claw bed), XZT was a more effective analgesic than ZT. Although the immobilization effects of XZT could not be reversed with the α2-antagonist drug tolazoline, they were reversed with yohimbine or atipamezole. However, the time to complete reversal of effects (i.e., standing and ambulatory) was highly variable among bears.

Evaluation of zuclopenthixol acetate to decrease handling stress in wapiti.

Handling stress and capture myopathy are important consequences of intensively managing wildlife species. Over the last 15 yr, the use of long-acting neuroleptic (LAN) drugs in wildlife has increased, and these drugs have become a valuable tool for decreasing capture and handling stress in many species. At this time, reports on the use of these drugs in North American species are limited. The major objective of this study was to evaluate the use of the LAN, zuclopenthixol acetate (Clopixol-Acuphase®), to decrease both quantifiable and subjective measurements of stress and activity in wild wapiti (Cervus elaphus, North American elk). This blinded, randomized study took place in February 1999 in Manitoba (Canada) and involved 11 animals receiving the drug and 12 animals acting as controls. At 24 hr after drug administration, there were measurable and significant decreases in the stress and activity of treated animals versus controls during handling. Treated animals had significantly lower mean body temperatures (39.0 versus 40.6 C), less hemoconcentration (mean packed cell volume 0.42 versus 0.49, mean hemoglobin 159.09 versus 181.75 g/L, mean total protein 65.0 versus 70.25 g/L), lower mean serum cortisol (97.91 versus 139.50 mmol/L), lower mean blood lactate (3.39 versus 5.98 mmol/L), and were less metabolically acidotic (mean pHv 7.45 versus 7.34, mean bicarbonate 29.36 versus 24.25 mmol/L, mean base excess 5.64 versus −0.83 mmol/L). Only control animals had evidence of muscle damage based on serum biochemistry (creatine phosphate values of two animals of 42,080 and 25,887 U/L). No animals developed clinical capture myopathy, and no animals died. Measurable effects of this drug were still apparent at 72 hr post-administration. The results of this study support the use of Clopixol-Acuphase® in wapiti as a means to decrease handling stress and activity.

Reversible immobilization of free-ranging polar bears with medetomidine-zolazepam-tiletamine and atipamezole.

The objective of this study was to determine if the potent α2 agonist, medetomidine, and its specific antagonist, atipamezole, could be effectively used to immobilize polar bears (Ursus maritimus). Specifically, our goal was to develop a drug combination containing medetomidine that addressed some of the problems such as prolonged recovery time, non-reversibility, and poor analgesia that have been identified with the currently preferred drug combination, zolazepam-tiletamine (Telazol® or Zoletil®). During 1995 and 1996, 51 free-ranging polar bears along the western coast of Hudson Bay, Canada, were immobilized with a combination of medetomidine, zolazepam, and tiletamine (MZT). Immobilization with MZT was characterized by a short induction time, low volume, reliable and predictable immobilization and reversibility, adequate analgesia, and relative safety in handling for field personnel. Few adverse physiological effects were observed in any target animals with the exception of a single bear which convulsed and died shortly after it was reversed from anesthesia with atipamezole. We conclude that MZT is an effective drug combination for immobilizing polar bears. However, because of an unexplained mortality, further investigation of the physiological effects of MZT and atipamezole is warranted.

Evaluation of isoflurane and propofol anesthesia for intraabdominal transmitter placement in nesting female canvasback ducks.

Heart rate, occurrence of apnea, body temperature, quality of anesthesia and nest abandonment were compared during either propofol or isoflurane anesthesia of nesting female canvasback ducks (Aythya valisineria) at 15 to 18 days of incubation. One hundred eighteen canvasbacks were assigned randomly to three treatments so that nest abandonment could be compared among treatments from May to July 1995 and 1996. Sterile dummy silicone implants were placed during an abdominal laparotomy while ducks were anesthetized with either propofol or isoflurane, or ducks were flushed from the nest but not captured (control). Propofol was delivered through an intravenous catheter, while isoflurane was delivered in oxygen. Propofol provided smooth, rapid induction and recovery, whereas ducks recovering from isoflurane tended to struggle. At the nest, ducks in the propofol group were given additional boluses until they were lightly anesthetized, whereas birds that received isoflurane were released. All birds survived surgery but one death occurred prior to surgery in 1995 using propofol during a period without ventilation and monitoring. Adequate artificial ventilation is recommended to prevent complications. Heart rate declined significantly in both years during isoflurane anesthesia and in 1995 during propofol anesthesia but not 1996. During both isoflurane and propofol anesthesia, body temperature declined significantly over time. Nest abandonment was significantly different among treatments and occurred in all treatment groups in both years, but propofol (15%) and control groups (8%) had lower than expected abandonment compared to isoflurane (28%). Propofol offers several advantages over isoflurane for field use; equipment is easily portable, lower anesthetic cost, and ambient temperature does not alter physical characteristics of the drug. Advantages over isoflurane, including lower nest abandonment following intraabdominal radio transmitter placement, make propofol a good anesthetic choice for field studies.

Intranasal Administration of Xylazine to Reduce Stress in Elk Captured by Net Gun

Forty free-ranging elk (Cervus elaphus manitobensis) were captured by net gun in Riding Mountain National Park (Manitoba, Canada) during February 2002 and were administered either saline (control) or xylazine by the intranasal route, to evaluate the efficacy and benefit of intranasal xylazine to reduce stress. Elk that received xylazine had higher relaxation scores than control elk, and the onset of sedation occurred quickly, often <1 min. Serum concentrations of cortisol, creatine kinase, and γ-glutamyltransferase were lower in elk that received xylazine than in control elk. At the conclusion of handling, the intravenous administration of yohimbine quickly abolished the sedative effect of xylazine, which allowed elk to be released without concern of physical injury due to ataxia. The intranasal administration of xylazine can be used to reduce stress in wild animals under situations where they are being handled while physically restrained.

Physiological Effects of Medetomidine-Zolazepam-Tiletamine Immobilization in Black Bears

A combination of medetomidine-zolazepam-tiletamine (MZT) was used to immobilize four black bears (Ursus americanus). The drugs were used at a dose of approximately 52 μg/kg of medetomidine, 0.86 mg/kg of zolazepam, and 0.86 mg/kg of tiletamine. Induction occurred in 6.3 ± 3.3 min (mean ± SD). The combination produced minimal adverse cardiopulmonary effects. Hypertension occured in all four bears. Oxygenation and ventilation was good in three of the four bears. One bear demonstrated slight hypoxemia and hypoventilation at 15 min following drug administration. At one 1hr following drug administration atipamezole was administered at a dose of approximately 240 μg/kg. Recovery time was taken as the time from administration of the atipamezole until the time that the bear was sitting in the trap. Recovery occurred in 6.0 ± 4.1 min. MZT produced rapid, reliable immobilization in black bears with minimal adverse physiological effects. Immobilization, produced by this combination, was readily reversible with atipamezole.

Efficacy of a Portable Oxygen Concentrator with Pulsed Delivery for Treatment of Hypoxemia During Anesthesia of Wildlife

Abstract:u2003 Portable battery-driven oxygen concentrators provide an alternative to the use of oxygen cylinders for treatment of hypoxemia during field anesthesia. The aim of this study was to evaluate the use of the EverGoTM Portable Oxygen Concentrator (Respironics®, Murrysville, Pennsylvania 15668, USA) with pulse-dose delivery for improvement of arterial oxygenation during anesthesia of wildlife. This concentrator delivers oxygen in a pulsed flow with pulse volumes from 12 to 70 ml, up to a maximum capacity of 1.05 L/min. The pulse-dose setting shall be adjusted according to the respiratory rate of the animal, e.g., setting 6 for a respiratory rate ≤15/min. The study included 16 free-ranging brown bears (Ursus arctos), 18 free-ranging bighorn sheep (Ovis canadensis), and five captive reindeer (Rangifer tarandus). Oxygen was administered via two nasal lines that were inserted through the nostrils to the level of the medial canthus of the eyes. Arterial blood samples were collected before, during, and after oxygen therapy and immediately analyzed. When providing oxygen from the portable concentrator, the arterial oxygenation markedly improved in all brown bears and some reindeer, whereas no or minor improvement was seen in the bighorn sheep. The mean ± SD (range) PaO2 during oxygen supplementation was 134 ± 29 (90–185) mmHg in the brown bears, 52 ± 11 (32–67) mmHg in the bighorn sheep, and 79 ± 19 (61–110) mmHg in the reindeer. The efficacy of the evaluated method may be influenced by ambient temperature, altitude, pulse-dose setting on the concentrator, the animals respiratory rate, and species-specific physiology during anesthesia. Advantages of the portable oxygen concentrator included small size and low weight, ease of operate, and rechargeablity.

Physiologic effects of nasal oxygen or medical air administered prior to and during carfentanil-xylazine anesthesia in North American elk (Cervus canadensis manitobensis).

Abstract This study compared the physiologic effects of carfentanil–xylazine anesthesia in elk administered nasal oxygen or medical air. Eight female 5 ± 2-yr-old (mean ± SD) captive elk (Cervus canadensis manitobensis) weighing 245 ± 20 kg and habituated to chute restraint were studied in a randomized crossover. Nasal insufflation of oxygen or medical air (10 L/min) was provided prior to and throughout anesthesia. Baseline data were collected before i.m. injection of carfentanil (10 μg/kg) and xylazine (0.2 mg/kg). Arterial blood gases (PaO2 and PaCO2), arterial blood pressure, heart and respiratory rate, and observations of muscle rigidity and movement were collected every 3 min for 30 min. Drugs were antagonized at 30 min with i.m. naltrexone (1 mg/kg) and tolazoline (2 mg/kg). Induction and recovery were significantly faster (mean ± SD) in elk receiving oxygen (208 ± 39 and 333 ± 63 sec, respectively), vs. medical air (306 ± 84 and 532 ± 201 sec). Elk receiving oxygen had a significantly higher PaO2 and PaCO2, and significantly lower pH and heart rate. Minimum PaO2 was 75 ± 30 mm Hg (oxygen), and 28 ± 6 mm Hg (air). Maximum PaCO2 was 89 ± 5 mm Hg (oxygen), and 64 ± 4 mm Hg (air). Frequency of rigidity and movement decreased when PaO2 ≥ 70 mm Hg. Animals breathing air demonstrated slower inductions and recoveries, severe hypoxemia, and increased rigidity and movement. Oxygen administration reduced hypoxemia and improved anesthesia quality, but caused prolonged periods of apnea, and moderate to severe hypercarbia and respiratory acidosis.

CARDIOPULMONARY RESPONSE OF ANESTHETIZED POLAR BEARS TO SUSPENSION BY NET AND SLING

Since 1995, at least three polar bears (Ursus maritimus) have died in the area of Churchill (Manitoba, Canada) as a direct result of being suspended in a net during helicopter-assisted translocations. To assess and improve methods of suspending anesthetized polar bears, we conducted a study during November 1997 to determine the cardiopulmonary responses of eight captive polar bears to suspension by net and by sling. Each bear was anesthetized on two occasions in which the sequence of activities followed and the type of data collected was identical, with only the method of suspension differing. Control data obtained from 11 captive polar bears during 1995–96 was included in the statistical analyses of cardiopulmonary data to help clearly differentiate the cardiopulmonary effects of suspension from those of drug metabolism. Suspending polar bears above the ground by net caused acute hypertension (e.g., 17 to 49% increase in mean arterial pressure), possibly as a result of increased venous return due to body compression. Increased arousal (e.g., head, tongue, and limb movement) also occurred consistently during net-suspension and suggested a stress response. Surprisingly, most suspended bears showed little change in blood gas values, but at least one bear became hypoxemic (i.e., PaO2 < 60 mm Hg) with each method of suspension. Because of the potential health risks of hypertension and hypoxemia, we recommend modifying the method by which polar bears are suspended with the goal of reducing body compression.