Cardiovascular and behavioral responses of gray wolves to ketamine-xylazine immobilization and antagonism by yohimbine

Adult wolves (Canis lupus) were immobilized with 6.6 mg/kg ketamine hydrochloride (KET) and 2.2 mg/kg xylazine hydrochloride (XYL) administered intramuscularly. Induction time was 4.6 +/- 0.3 min (mean +/- SE). Immobilization resulted in significant bradycardia and hypertension (P less than 0.05). Twenty min after induction, the wolves were given 0.05-0.60 mg/kg yohimbine hydrochloride (YOH). Yohimbine given intravenously produced dose-related increases in heart rate (HR) with doses greater than 0.15 mg/kg resulting in extreme tachycardia (greater than 300 bpm). All doses of YOH caused a temporary decrease in mean arterial blood pressure (MABP) with some individual animals manifesting profound hypotension (less than 30 torr) at doses greater than 0.15 mg/kg. Increasing the dose of YOH above 0.15 mg/kg did not significantly decrease either arousal or ambulation times. Administering YOH at 40 or 60 min after induction resulted in decreased arousal and ambulation times. Stimulation by weighing and taking repeated blood samples during anesthesia did not shorten arousal times. We recommend that wolves immobilized with XYL-KET be antagonized with doses of YOH less than 0.15 mg/kg.     

Immobilization of white-tailed deer by etorphine and xylazine and its antagonism by nalmefene and yohimbine

White-tailed deer (Odocoileus virginianus) were immobilized with either 4.0 mg etorphine hydrochloride (ETOR) or 3.5 mg ETOR and 50.0 mg xylazine (XYL). Deer immobilized with ETOR only were given 4.0 mg nalmefene hydrochloride (NAL), a new opioid antagonist, 20 min after induction. Deer immobilized with ETOR and XYL received 3.5 mg NAL and 0.125 mg/kg yohimbine hydrochloride (YOH). The dose of 4.0 mg ETOR did not provide acceptable immobilization and was discontinued. A NAL:ETOR ratio of 1:1 was insufficient for complete and sustained antagonism of ETOR. Subsequently, deer were immobilized with ETOR and XYL as before which was then antagonized with 35.0 mg NAL and 0.125 mg/kg YOH. The 10:1 ratio of NAL:ETOR appeared to provide complete antagonism with no evidence of renarcotization. Although more study is required, NAL could become a useful antagonist for opioid-induced immobilizations.     

Ketamine-xylazine anesthesia in red-tailed hawks with antagonism by yohimbine

Five red-tailed hawks (Buteo jamaicensis) were anesthetized at weekly intervals with intravenous ketamine hydrochloride (KET, 4.4 mg/kg) and xylazine hydrochloride (XYL, 2.2 mg/kg). Twenty min after anesthesia, yohimbine hydrochloride (YOH, 0.05, 0.10, 0.20 and 0.40 mg/kg) or a control was administered. All doses of YOH significantly reduced the head-up times (F = 20.84, df = 1,24, P less than 0.0001) and the standing times (F = 12.30, df = 1,24, P less than 0.0001), compared to the control group. The heart and respiratory rates following YOH (all doses) were significantly greater (P less than 0.01) than the anesthetized rates, but were comparable to the rates observed in restrained, unanesthetized hawks. Yohimbine did not appear to have any significant effect on body temperature. Based upon administration of 4.4 mg/kg KET and 2.2 mg/kg XYL, a dose of 0.10 mg/kg YOH was recommended to achieve antagonism without causing profound cardiovascular or respiratory changes.     

Use of xylazine sedation with yohimbine antagonism in captive gray wolves

Captive gray wolves (Canis lupus) were given 2.2 mg/kg xylazine hydrochloride intramuscularly resulting in profound sedation in 9.1 +/- 0.6 min (mean +/- SE). Heart rate was 42.0 +/- 1.0 beats per minute and respiratory rate was 20.1 +/- 1.6 respirations per minute during sedation. A variety of manipulations could be performed on sedated animals in relative safety. Thirty min after xylazine administration, the animals were given either 0.15 mg/kg yohimbine hydrochloride or 5% dextrose solution intravenously causing recovery in 5.3 +/- 1.0 and 97.1 +/- 14.0 min, respectively (P less than 0.001).     

Immobilization of gray wolves (Canis lupus) with sufentanil citrate

Gray wolves (Canis lupus) were immobilized with 0.5 mg/kg xylazine plus 7.5 micrograms/kg of either sufentanil (n = 8), etorphine (n = 8), or carfentanil (n = 2). Drug doses used in this study were selected to provide consistency for comparison and are not recommended doses for effective immobilization of wolves. Induction times were similar among groups (11.9 +/- 1.0 min). Thirty min after induction, wolves were given either 0.5 mg/kg naloxone hydrochloride plus 0.15 mg/kg yohimbine hydrochloride or saline only intravenously. Arousal times for wolves given naloxone and yohimbine (1.2 +/- 0.1 min) were shorter than wolves given saline (35.5 +/- 6.4 min). Respiratory rates were similar among the three drug groups (6.9 +/- 1.0 breaths/min). One animal given sufentanil then saline was found dead 108 min after induction. Presumptive diagnosis was renarcotization and hypothermia. Results indicated that sufentanil is an effective opioid immobilizing agent for gray wolves.     

Xylazine hydrochloride-ketamine hydrochloride immobilization of wolves and its antagonism by tolazoline hydrochloride

Fourteen wolves (Canis lupus L.) were singularly or repeatedly immobilized with 30 mg xylazine hydrochloride (HCl) and 400 mg ketamine HCl. Mean induction time was 5.3 +/- 4.6 min (mean +/- SD). Administration of 8.0 mg/kg tolazoline HCl as an antagonist significantly reduced immobilization times from 148.0 +/- 52.7 to 47.9 +/- 8.9 min (F = 63.69, df = 1,17, P less than 0.05). The average times from injection to ambulation for 2.0, 4.0, and 8.0 mg/kg tolazoline HCl were 35.2 +/- 31.8, 18.5 +/- 11.7, and 10.2 +/- 9.1 min. Tolazoline HCl increased heart rates significantly (P less than 0.001) from 75 +/- 14 to 120 +/- 23 beats/min, reversing a xylazine HCl-induced bradycardia. Respiratory rates also increased significantly (P less than 0.01) after tolazoline HCl injection from 19 +/- 7 to 28 +/- 8 breaths/min. Immobilization resulted in an initial hypertension which was normalized after tolazoline HCl administration. One female wolf had a single sinoatrial block within 1 min of receiving tolazoline HCl. Tolazoline HCl appears to be an effective antagonist for xylazine HCl-ketamine HCl immobilization of wolves.     

Influence of naloxone and yohimbine administration on pulsatile LH secretion in luteal phase beef cows

This study examined the effects of two specific neurotransmitter receptor antagonists, naloxone (NAL; mu-opioid) and yohimbine (YOH; alpha(2)-adrenergic), on pulsatile luteinizing hormone (LH) release during the luteal phase (Day 10; Day 0 = estrus) of beef cows. Treatments were saline i.m. (C; n = 4); 1mg/kg NAL i.m. followed 3 h later by two 0.5 mg/kg injections spaced 2.5 h apart (N; n = 4); 0.2 mg/kg YOH i.v. (Y; n = 3); or combined N and Y regimens, with Y preceding N by 30 min (NY; n = 4). Blood samples were collected for 8 h before (Period I) and after (Period II) initiation of treatment. Respiration rates of Y cows were similar to C cows during Period II. However, respiration rates of N and NY animals increased 70% within 30 min of the first NAL injection. Acute LH release was not observed in response to either NAL or YOH. Pulsatile LH secretion was unchanged in N, Y and NY cows during Period II when compared with Period I. In contrast, basal and pulsatile LH secretion was inhibited in C cows during Period II. The inhibition of LH secretion in C animals following NAL indicate that the cows were under stress during Period II. Thus, these data suggest that the inhibition of LH release in stressed animals can be overcome by pharmacologic attenuation of inhibitory (N) or accentuation of stimulatory (Y) signals to LHRH-containing neurons.     

Chemical restraint of Weddell seals (Leptonychotes weddellii) with a combination of tiletamine and zolazepam.

A 1:1 combination by weight of tiletamine hydrochloride and zolazepam hydrochloride was administered to 30 adult Weddell seals (Leptonychotes weddellii) in doses varying from 100 to 300 mg. Full immobilization was achieved in 16 seals, moderate sedation in seven and light sedation in seven. Three animals died; two were fully immobilized and one was moderately sedated prior to death. The drug combination was considered satisfactory, although its usefulness was limited by the lack of chemical antagonists when complications were encountered in immobilized animals.     

Antagonism of xylazine hydrochloride sedation in raptors by yohimbine hydrochloride

The mean time to initial reversal response (MTIRR) and the mean time to perching (MTP) were measured in 34 raptors sedated with xylazine hydrochloride with dosages ranging from 1.0 to 20 mg/kg intravenously (i.v.) and 2.5 to 20.0 mg/kg intramuscularly (i.m.). Yohimbine hydrochloride, given i.v. (0.2 mg/kg), 30 min after the injection of the xylazine, shortened the MTIRR and MTP compared to the controls. No adverse effects were noted due to the use of yohimbine. Yohimbine appeared to be a safe and effective antagonist for xylazine sedation in raptors.     

Physiological and behavioral responses of gray wolves (Canis lupus) to immobilization with tiletamine and zolazepam

We conducted a series of experiments to examine the efficacy of Telazol (TEL) for immobilization of captive gray wolves (Canis lupus). Ten wolves were immobilized with either 5 or 10 mg/kg TEL. There was no difference in induction time (6.5 +/- 0.8 versus 5.8 +/- 1.2 min; P = 0.63) between the two doses, but the time to initial arousal was longer for the higher dose (P = 0.0008). Wolves were again immobilized with 10 mg/kg TEL and upon initial arousal were given additional doses of either 5.0 mg/kg TEL or 2.5 mg/kg ketamine (KET) to maintain immobilization. Wolves given boosters of TEL had longer second recovery times than wolves given KET (P = 0.01). There were no differences in induction times or arousal times for wolves immobilized with TEL that had been reconstituted with sterile water and stored at 20 C for 30 days (P greater than or equal to 0.11) or 60 days (P greater than or equal to 0.27) when compared to immobilization times using fresh solution. Induction times for wolves given TEL reconstituted with water and propylene glycol and stored for 60 days at -9 C were longer (P less than 0.05) than such times for wolves given standard TEL, but time to initial arousal was unchanged (P greater than or equal to 0.44). There were no differences in heart rates (P = 0.36), blood pressures (P = 0.32), respiratory rates (P = 0.91), and rectal temperatures (P = 0.62) between the two TEL doses. Telazol was shown to be an effective and safe immobilizing agent for gray wolves.     

Yohimbine reversal of ketamine-xylazine immobilization of raccoons (Procyon lotor)

Six adult raccoons (Procyon lotor) were sedated with a combination of ketamine hydrochloride (KH) at 10 mg/kg body weight and xylazine hydrochloride (XH) at 2 mg/kg body weight intramuscularly (i.m.). Twenty min after the KH-XH combination was given, yohimbine hydrochloride (YH) at either 0.1 mg/kg (Trial 1) or 0.2 mg/kg (Trial 2) body weight or a saline control (Trial 3) was administered intravenously (i.v.). The time to arousal, time to sternal recumbency and time to walking were recorded. These times were significantly shortened after YH administration [e.g., mean time to walking (MTW) at 0.2 mg/kg YH = 23.7 min] as compared to the saline controls (MTW = 108.8 min). Heart and respiratory rates both increased after YH administration, while body temperature remained constant. A fourth trial was performed using a higher ratio of KH to XH (45:1 rather than 5:1) to mimic sedation as performed in the field. The mean time to arousal (MTA) and MTW in this trial (1.3 and 23.7 min, respectively) were significantly shorter than controls and similar to YH trials performed after immobilization with 5:1 KH-XH. Yohimbine hydrochloride may be useful in field studies that require sedation of raccoons using KH-XH combinations.     

Antagonism of xylazine hydrochloride-ketamine hydrochloride immobilization in guineafowl (Numida meleagris) by yohimbine hydrochloride

The mean time to arousal (MTA), the mean time to sternal recumbency (MTSR) and the mean time to walking (MTW) were measured in 10 adult guineafowl (Numida meleagris) immobilized with a combination of xylazine hydrochloride (1 mg/kg) and ketamine hydrochloride (25 mg/kg). Yohimbine hydrochloride, given intravenously (1 mg/kg) at 40 min after the injection of the xylazine-ketamine, significantly shortened the MTA, the MTSR and the MTW compared to saline controls. Increasing the dosage of yohimbine to 2.5 mg/kg did not shorten recovery when compared to the lower dosage. No adverse effects were noted at either dosage of yohimbine. Yohimbine appeared to be a safe and effective antagonist of xylazine-ketamine immobilization in guineafowl and may prove useful in other avian species to produce more rapid recovery from xylazine-ketamine immobilization, xylazine sedation or xylazine overdosage.     

A comparison of carfentanil/xylazine and Telazol/xylazine for immobilization of white-tailed deer

October 2001 to January 2002, captive free-ranging white-tailed deer (Odocoileus virginianus) were immobilized with a combination of carfentanil citrate and xylazine hydrochloride. From this study, we selected a dose of carfentanil/xylazine for the purpose of comparing immobilization parameters and physiologic effects with those of a combination of tiletamine and zolazepam (Telazol) and xylazine. Animals were initially given intramuscular injections of 10 mg xylazine and one of four doses of carfentanil (i.e., 0.5, 1.0, 1.5, and 2.0 mg). A carfentanil dose of 1.2 mg (x +/- SD = 23.5 +/- 3.2 microg/kg) and 10 mg xylazine (0.2 +/- 0.03 mg/kg) were selected, based on induction times and previously published reports, to compare with a combination of 230 mg of Telazol (4.5 +/- 0.6 mg/kg) and 120 mg xylazine (2.3 +/- 0.3 mg/kg). Time to first observable drug effects and to induction were significantly longer for deer treated with carfentanil/xylazine than with Telazol/xylazine (P < 0.01). Hyperthermia was common in deer immobilized with carfentanil/xylazine, but heart rate, respiration rate, and hemoglobin saturation were within acceptable levels. Degree of anesthesia of deer immobilized with Telazol/xylazine was superior to deer immobilized with carfentanil/xylazine. The combination of 120 mg of naltrexone hydrochloride and 6.5 mg of yohimbine hydrochloride provided rapid and complete reversal (1.9 +/- 1.1 min) of carfentanil/xylazine immobilization. Animals immobilized with Telazol/xylazine had long recovery times with occasional resedation after antagonism with 6.5 mg of yohimbine. The combination of carfentanil and xylazine at the doses tested did not provide reliable induction or immobilization of white-tailel (leer even though drug reversal was rapid and safe using naltrexone and yohimbine.     

Relative efficiency of succinylcholine, xylazine, and carfentanil/xylazine mixtures to immobilize free-ranging moose

We compared the efficiency of succinylcholine chloride, xylazine hydrochloride and carfentanil/xylazine mixtures in immobilizing 364 free-ranging moose (Alces alces) between 1987 and 1997 in Québec (Canada). With succinylcholine chloride (0.070, 0.062, 0.051 mg/kg of estimated body weight for calves, juveniles and adults), 63% of the 252 immobilization attempts led to complete immobilization and marking, whereas 7% of the darted animals died of respiratory paralysis during handling. The moose took an average of 13 min to lay down after darting (down time). Injection of xylazine (3.67-4.22 mg/kg) permitted sedation (the animal laid down but got up again when approached) or complete immobilization in 78% of the 40 darted adult moose, the mean down time being 8.7 min. No mortality was noted with this drug but 58% of the marked animals were only sedated. The use of RX821002A (0.058 mg/kg) as an antagonist, permitted a mean recovery time of 2.8 min after intravenous injection. With the carfentanil/xylazine mixtures (0.0071 and 0.181 mg/kg), 96% of the immobilization trials (n = 72) led to complete (88%) or partial (8%) immobilization, but 6% of the moose died several days after capture. The mean down time was 6.6 min, and injection of naltrexone (0.709 mg/kg) antagonized the effect of the immobilizing agent within 3.7 min. The respiratory rate was higher (P < 0.05) among moose immobilized with xylazine (35/min) than among those immobilized with carfentanil/xylazine mixtures (19/min) but this variation could be related to a longer pursuit time (z = 3.60; P < 0.01) and higher stress levels during handling. Rectal temperature also was higher with xylazine but the difference was small (39.7 vs. 39.3, P = 0.03) and did not differ significantly between the sexes (P > 0.05). Considering loss of materials and helicopter flight time due to non-successful marking trials, carfentanil/xylazine mixtures were the least expensive ($333 Cdn/animal).     

USE OF A PETHIDINE AND MIDAZOLAM COMBINATION FOR THE REVERSIBLE SEDATION OF CRABEATER SEALS (LOBODON CARCINOPHAGUS)

Between October and December of 1996–1999, off eastern Antarctica (60°-150°E), we darted 31 crabeater seals with midazolam and pethidine at estimated dose rates of 0.15–0.4 mg/kg and 1–3 mg/kg, respectively. Maximum sedation was reached at 23 ± 9 min (n = 18) and first signs of recovery were noted at 54 ± 24 min (n = 4). Seals greater than 250 kg body-mass were sedated by administration of approximately 90–100 mg midazolam and 600 mg pethidine, but the degree of sedation was unpredictable and did not permit invasive procedures in some cases. Behavior of the seal and adjacent conspecifics affected the success of procedures and our ability to monitor vital signs. Naloxone and flumazenil reversed sedation, making this combination attractive for use in animals adjacent to water. Additional ketamine was administered to two seals, resulting in improved restraint.     

Effectiveness of antagonists for tiletamine-zolazepam/xylazine immobilization in female white-tailed deer

A combination of tiletamine-zolazepam/xylazine (TZ/X) is effective in the chemical immobilization of white-tailed deer (Odocoileus virginianus); however, the lengthy duration of immobilization may limit its usefulness. From October to November 2002, 21 captive female deer were assigned randomly to an alpha(2) antagonist treatment to reverse xylazine-induced sedation (seven does per group). All deer were given 220 mg of TZ (4.5+/-0.4 mg/kg) and 110 mg of X (2.2+/-0.2 mg/kg) intramuscularly (IM). Antagonist treatments were either 200 mg of tolazoline (4.0+/-0.4 mg/kg), 11 mg of atipamezole (0.23+/-0.02 mg/kg), or 15 mg of yohimbine (0.30+/-0.02 mg/kg) injected, half intravenously and half subcutaneously, 45 min after the IM TZ/X injection. In addition, 10 other deer (five per group) were immobilized as before and then given tolazoline (200 mg) after 45 min, with either a carrier (dimethyl sulfoxide [DMSO]) or carrier (DMSO) plus flumazenil (5 mg) to reverse the zolazepam portion of TZ. Mean times from antagonist injection until a deer raised its head were different for alpha(2) antagonist treatments (P=0.02). Times were longer for yohimbine (62.3+/-42.7 min) than for either atipamezole (24.3+/-17.1 min) or tolazoline (21.3+/-14.3 min). Mean times from antagonist injection until standing were not different (P=0.15) among yohimbine (112.0+/-56.4 min), atipamezole (89.7+/-62.8 min), or tolazoline (52.6+/-37.2 min). A sedation score based on behavioral criteria was assigned to each deer every 30 min for 5 hr. On the basis of sedation scores, tolazoline resulted in a faster and more complete reversal of immobilization. Flumazenil treatment did not affect recovery.     

Influence of hypothalamic-pituitary-adrenocortical hormones on reproductive hormones in gray wolves (Canis lupus).

The release of hypothalamic-pituitary-adrenocortical hormones was studied in intact and neutered gray wolves (Canis lupus) to determine how these hormones interact and affect reproductive hormones. Experiments were performed on adult wolves anesthetized with 400 mg ketamine and 50 mg promazine. Intravenous (i.v.) injections with 50 micrograms ovine corticotropin releasing factor (oCRF) significantly increased adrenocorticotropin (ACTH; P < or = 0.01), cortisol (CORT; P < or = 0.004), and progesterone (P < or = 0.036), but not beta-endorphin (P > or = 0.52). Since neutered wolves demonstrated dose-dependent elevations in response to ACTH, it was concluded that the progesterone was secreted from the adrenal gland. Basal luteinizing hormone (LH) concentrations in neutered wolves were similar before and 60 min after i.v. injection of 1, 5, or 25 IU ACTH (P > or = 0.36) or 2.2 mg/kg cortisol (P = 0.42). Neither 25 IU ACTH (P = 0.55) nor 0.22 mg/kg dexamethasone (P = 0.49) altered the LH response to injection of LH releasing hormone in neutered wolves. Chronic administration of 0.22 mg/kg/day dexamethasone for 3 d did not alter baseline LH concentrations (P = 0.75). Injection of 1.0 mg/kg naloxone (NAL), however, increased LH concentrations relative to baseline values in both intact (P = 0.032) and neutered (P = 0.0005) female wolves, but not in intact (P = 0.19) or neutered males (P = 0.07). These results indicated that in gray wolves (1) oCRF stimulated the release of pituitary and adrenal hormones in a fashion similar to that of other mammals; (2) the adrenal cortex was capable of secreting progesterone into the systemic circulation; (3) exogenous glucocorticoids did not alter LH concentrations; and (4) endogenous opioids may modulate LH secretion in female wolves.     

An evaluation of three anaesthetic regimes in the gray short-tailed opossum (Monodelphis domestica)

The effect of several anaesthetic agents on the gray short-tailed opossum (Monodelphis domestica) was investigated. Pentobarbitone sodium at a dose of 50 mg/kg sedated the animals but did not produce analgesia or anaesthesia. A combination of ketamine hydrochloride and xylazine at 40 mg/kg and 5 mg/kg, respectively, sedated the animals, but anaesthetic levels were not attained. Halothane was most effective in producing anaesthesia in Monodelphis domestica. Hypothermia was a major side effect with all three anaesthetic regimes.     

Presynaptic alpha-adrenoceptor regulation of transmitter release in the conscious rat

1. Blood pressure (BP) and heart rate (HR) were recorded in conscious, adrenal demedulated rats. The rats were subjected to a 1-min period of mild "stress", induced by jet-air directed into the experimental cage. The plasma content of noradrenaline (NA), dopamine (DA) and 3, 4-dihydroxy-phenylacetic acid (DOPAC) was determined 1 min after termination of "stress". 2. The presynaptic alpha 2-adrenoceptor antagonist yohimbine (YOH) (10(-7) - 10(-6) mol/kg, given 5 min prior to "stress") did not alter the increase in BP and HR, induced by "stress", when compared to control rats (receiving NaCl instead of YOH at the corresponding time). 3. Pre-treatment with atropine (ATR) (2.5 mg/kg) 5 min before YOH (10(-6) mol/kg) or NaCl increased HR but not BP significantly in both groups of rats. "Stress", as above, gave a significant prolongation of the increase in HR in rats receiving YOH, when compared to control rats. The increase in BP was not significantly altered, compared to controls. 4. The neuronal re-uptake inhibitor desmethylimipramine (DMI) (0.1 mg/kg) was given together with ATR (2.5 mg/kg) 5 min before YOH (10(-6) mol/kg) or NaCl in one group of rats. This treatment induced a significant increase in HR but did not affect BP. "Stress", induced as above, extended the duration of the increase in HR in the YOH-treated rats, compared to controls. The increase in BP was not significantly different between the YOH-treated rats and the controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antagonism of xylazine hydrochloride with yohimbine hydrochloride and 4-aminopyridine in captive wapiti

Eight captive wapiti (Cervus elaphus nelsoni) were injected with xylazine hydrochloride on two occasions during March and April 1984. Animals were grouped into a modified Latin square design and were given either successive injections of yohimbine hydrochloride and 4-aminopyridine (4-AP) to antagonize the sedative effects of xylazine hydrochloride or permitted an unantagonized recovery. Induction times ranged from 3 to 26 min with excited and wild animals requiring a supplementary dose. Time until walking was significantly (P less than 0.005) shorter in the group given successive injections (given i.v.) of the reversal drugs yohimbine hydrochloride (0.15 mg/kg) and 4-AP (0.30 mg/kg) than those animals during unantagonized recoveries. Marked increase in heart rate and respiratory rate were observed in animals within 3 min after successive injections of yohimbine hydrochloride and 4-AP. There was no occurrence of convulsions and animals did not relapse to profound sedation. Slight muscle tremors were observed in one animal which received a dose of 0.35 mg/kg of 4-AP. This drug combination can reduce markedly the duration of recovery from xylazine hydrochloride-induced sedation in wapiti.