Testicular hyperthermia increases blood flow that maintains aerobic metabolism in rams.

There is a paradigm that testicular hyperthermia fails to increase testicular blood flow and that an ensuing hypoxia impairs spermatogenesis. However, in our previous studies, decreases in normal and motile spermatozoa after testicular warming were neither prevented by concurrent hyperoxia nor replicated by hypoxia. The objective of the present study was to determine the effects of increasing testicular temperature on testicular blood flow and O2 delivery and uptake and to detect evidence of anaerobic metabolism. Under general anaesthesia, the testicular temperature of nine crossbred rams was sequentially maintained at ~33°C, 37°C and 40°C (±0.5°C; 45min per temperature). As testicular temperature increased from 33°C to 40°C there were increases in testicular blood flow (13.2±2.7 vs 17.7±3.2mLmin-1 per 100g of testes, mean±s.e.m.; P<0.05), O2 extraction (31.2±5.0 vs 47.3±3.1%; P<0.0001) and O2 consumption (0.35±0.04 vs 0.64±0.06mLmin-1 per 100g of testes; P<0.0001). There was no evidence of anaerobic metabolism, based on a lack of change in lactate, pH, HCO3- and base excess. In conclusion, these data challenge the paradigm regarding scrotal-testicular thermoregulation, as acute testicular hyperthermia increased blood flow and tended to increase O2 delivery and uptake, with no indication of hypoxia or anaerobic metabolism.

Increased testicular blood flow maintains oxygen delivery and avoids testicular hypoxia in response to reduced oxygen content in inspired air.

Despite a long-standing assertion that mammalian testes operate near hypoxia and increased testicular temperature causes frank hypoxia, we have preliminary evidence that changes are due to hyperthermia per se. The objective was to determine how variations in inspired oxygen concentration affected testicular blood flow, oxygen delivery and extraction, testicular temperature and lactate production. Eight rams were maintained under general anesthesia, with successive decreases in oxygen concentration in inspired air (100, 21 and 13%, respectively). As oxygen concentration decreased from 100 to 13%, there were increases in testicular blood flow (9.6 ± 1.7 vs 12.9 ± 1.9 ml/min/100 g of testis, P < 0.05; mean ± SEM) and conductance (normalized flow; 0.46 ± 0.07 to 1.28 ± 0.19 ml/min/mm Hg/100 g testis (P < 0.05). Increased testicular blood flow maintained oxygen delivery and increased testicular temperature by ~1 °C; this increase was correlated to increased testicular blood flow (r = 0.35, P < 0.0001). Furthermore, oxygen utilization increased concomitantly and there were no significant differences among oxygen concentrations in blood pH, HCO3- or base excess, and no effects of venous-arterial differences in lactate production. In conclusion, under acute hypoxic conditions, testes maintained oxygen delivery and uptake by increasing blood flow and oxygen extraction, with no evidence of anaerobic metabolism. However, additional studies are needed to determine longer-term responses and potential evidence of anaerobic metabolism at the molecular level.

Clinical indicators of blood gas disturbances, elevated L-lactate concentration and other abnormal blood parameters in newborn beef calves.

Blood gas disturbances, commonly resulting from dystocia, are associated with failed transfer of passive immunity, morbidity and mortality in newborn calves. Modified APGAR scores intended to identify compromised calves are not widely adopted due to lack of practicality and inconsistent associations with blood parameters. The objective of this study was to determine clinical indicators of acidemia in newborn beef calves. Blood parameters at 10 min and 24 h after birth were compared to at-birth clinical examination parameters and calving characteristics in 77 commercial beef calves. There were no associations between heart rate or respiratory rate and blood pH or blood L-lactate concentration (LAC; r < 0.25); however, LAC was highly correlated with blood pH (r, -0.86). Abnormal mucous membrane color (red, white or blue) was associated with increased LAC (P = 0.002) but not decreased blood pH (P = 0.07). Abnormal results for tests of muscle tonicity and reflexes, namely inability to completely withdraw the tongue when pinched and a weak suckle reflex, were associated with decreased blood pH and increased LAC (P <0.05). Calves born to primiparous dams or from an assisted calving also had decreased blood pH and increased LAC (P <0.05). Differences in blood pH between at-birth categories resolved for all parameters by 24 h after birth, except for tongue withdrawal (P= 0.04). In conclusion, traditional APGAR parameters, heart rate, respiratory rate and mucous membrane color were not useful for the identification of acidemic calves; however, tongue withdrawal, calving ease, and parity should be included in such an assessment. Utilizing hand-held LAC meters may be a practical method to quickly identify compromised calves with acidemia in a field setting.

Effects of castration method and frequency of intramuscular injections of ketoprofen on behavioral and physiological indicators of pain in beef cattle.

Two experiments were conducted to determine the effect of a single or multiple intramuscular (i.m.) injection of ketoprofen and castration technique on physiological and behavioral indicators of pain in beef calves. A total of 150 bull calves (284.8 ± 22.7 kg BW) were used in both experiments, each 1 conducted as a 3 × 2 factorial design, where main factors included castration technique--no castration (CT), surgical (SU), or band (BA)--and drug administration--physiological solution (PS) or i.m. injection of ketoprofen (KP; 3 mg Anafen/kg BW) in the neck of calves. Animals were weighed weekly during the experiment to calculate ADG. Behavioral responses indicative of pain and discomfort during the castration procedure were documented using a visual analog score (VAS) by an experienced observer who was blind to the treatments. Movements of the animals in the chute during castration were quantified using a strain gauge system mounted on the head gate to evaluate the escape response of the cattle. Pens were equipped with an automated feed bunk monitoring system enabling feed intake and feeding behavior to be continuously monitored for each individual. Thermographic images of the scrotal area were evaluated 24 and 0.5 h before castration, 0.5, 1, 24, 48, and 270 h postcastration, and weekly thereafter until the end of the trial. Blood samples were obtained postcastration to evaluate changes in total white blood cell (WBC) count and neutrophil-to-lymphocyte (N:L) ratio. Saliva samples were taken 24 and 0.5 h before castration, immediately after castration, and 0.5, 1, 2, 5, 24, and 48 h and then 5, 7, and 14 d after castration to determine cortisol concentration. Scrotal temperature, VAS, total WBC, N:L ratio, salivary cortisol, mobility, and pressure exerted in the chute were greater (P < 0.05) and ADG and feed intake were lower (P < 0.05) in SU than in CT animals within the first week after castration. Also, BA calves had a greater (P < 0.05) scrotal temperature around wk 4 after castration and a lower feed intake and ADG at wk 2 and 3 and wk 6 and 7 after castration, respectively, compared to CT. Treatment KP had limited effects on reducing the indicators of pain associated with SU or BA, suggesting that further studies will be needed to assess the posology of the i.m. administration of ketoprofen to improve the consistency of its effects as a pain mitigation strategy after castration.

Pain mitigation after band castration of beef calves and its effects on performance, behavior, Escherichia coli, and salivary cortisol.

Eighty-nine steer and bull calves (210 +/- 20 d of age) were randomly assigned to a 2 x 2 factorial arrangement of treatments to study the effect of sham or band castration (CAST) with or without pain medication (MED) on performance, behavior, cortisol, and Escherichia coli shedding. Steers (serving as controls; C) were previously castrated at 34 +/- 10 d of age, whereas bulls (B) remained intact until band application on d 20 of the experiment. One-half of the calves in each group received pain medication (M; xylazine epidural and intravenous flunixin meglumine) or saline (NM) solutions at 0.5 h before castration. Feed intake, ADG, and feeding behavior were measured over a 3-wk period before (used as covariates) and a 6-wk period after castration. Fecal and saliva samples were collected from 32 calves for E. coli enumeration at -7 (covariate), 2, 5, and 7 d, and for cortisol concentration at -0.5 (covariate), 0, 0.5, 1, 2, 4, 24, 48, 168, and 336 h relative to castration, respectively. Lying behavior was measured in the home pen and step length at exit from the chute. There were no significant CAST x MED interactions on growth rate or feed intake. Overall ADG was less in B compared with C (P < 0.001), but feed intake was less during wk 4 only (P = 0.01). On average, M had less intake (P = 0.02) and eating rate (P = 0.04) than NM calves. The BM had less fecal E. coli counts than CM (P = 0.05) and castrated and nonmedicated calves (P = 0.08). Salivary cortisol was less in BM compared with the rest of treatments at 1 and 2 h after banding (P

The effect of nitrous oxide on halothane, isoflurane and sevoflurane requirements in ventilated dogs undergoing ovariohysterectomy.

OBJECTIVE: To examine the effect of 64% nitrous oxide (N2O) on halothane (HAL), isoflurane (ISO) or sevoflurane (SEV) requirements in dogs undergoing ovariohysterectomy. STUDY DESIGN: Prospective, randomized, clinical trial. ANIMALS: Ninety, healthy dogs of (mean +/- SD) body weight 21.2 +/- 10.0 kg and age 17.8 +/- 22.8 months. MATERIALS AND METHODS: After premedication with acepromazine, hydromorphone and glycopyrrolate, anesthesia was induced with thiopental administered to effect. Dogs received one of six inhalant protocols (n = 15 group): HAL; HAL/N2O; ISO; ISO/N2O; SEV; or SEV/N2O. End-tidal CO2 was maintained at 40 +/- 2 mmHg with intermittent positive pressure ventilation (IPPV). Body temperature, heart rate, indirect systemic arterial blood pressures, inspired and end-tidal CO2, volatile agent, N2O and O2 were recorded every 5 minutes. The vaporizer setting was decreased in 0.25-0.5% decrements to elicit a palpebral reflex, and this level maintained. Statistical analysis included two-way anova for repeated measures with Bonferroni's correction factor and statistical significance assumed when p < 0.05. Percentage reduction in end-tidal volatile agent was calculated at 60 minutes after starting study. RESULTS: End-tidal HAL, ISO and SEV decreased when N2O was administered. Percentage reduction: HAL (12.4%); ISO (37.1%) and SEV (21.4%). Diastolic, mean and systolic blood pressures increased in ISO/N2O compared with ISO. Heart rate increased in ISO/N2O and SEV/N2O compared with ISO and SEV, respectively. Systolic, mean and diastolic blood pressures increased in SEV compared with HAL and ISO. Systolic, mean, diastolic blood pressures and heart rate increased in SEV/N2O and ISO/N2O compared with HAL/N2O. CONCLUSIONS: N2O reduces HAL, ISO and SEV requirements in dogs undergoing ovariohysterectomy. Cardiovascular stimulation occurred when N2O was used with ISO, less so with SEV and not with HAL

Treatment of hypoxemia during xylazine-tiletamine-zolazepam immobilization of wapiti.

Hypoxemia is a commonly observed complication during the chemical immobilization of wild ruminants. If severe and left untreated, it can predispose animals to arrhythmias, organ failure, and capture myopathy. The following prospective study was designed to measure the degree of hypoxemia in wapiti that were immobilized with a combination of xylazine and tiletamine-zolazepam and to assess the response to nasal oxygen therapy. Pulse oximetry and arterial blood gas analysis were used to assess the degree of hypoxemia prior to nasal insufflation of oxygen and to demonstrate any beneficial effects of this intervention. All wapiti exhibited mild to marked hypoxemia (PaO2 = 43 +/- 11.8 mmHg) prior to treatment and showed marked improvement after 5 minutes of nasal insufflation of oxygen at 10 L/min (PaO2 = 207 +/- 60 mmHg). This inexpensive, noninvasive technique has great benefit in treating clinical hypoxemia under field conditions, and we recommend that nasal insufflation of oxygen be implemented during xylazine-tiletamine-zolazepam-induced immobilization of wapiti and other wild ruminants.

Comparison of analgesic techniques for antler removal in wapiti.

The purpose of this research was to compare the effectiveness of ring block anesthesia (LA) and electroanesthesia (A) for antler removal in elk given a long-acting tranquilizer to remove stress from restraint. Thirty-two male wapiti were given 1 mg/kg body weight of zuclopenthixol acetate; the next day, they were restrained in a hydraulic chute, provided with electroanesthesia or a lidocaine ring block, and had their antlers removed. Behavioral response to antler removal was scored. Significantly more (P = 0.032) animals responded to antler removal in the EA group. Heart rates and arterial pressures were measured by a catheter connected to a physiological monitor. Heart rate increased significantly over time with EA, but not with LA. Heart rate increased from baseline significantly more in the EA group immediately prior to antler removal (P = 0.017), immediately post antler removal (P = 0.001), and at 1 min post antler removal (P = 0.037). It was concluded that EA is not as effective a method of anesthesia as is LA for antler removal.

The use of a catheter to provide brachial plexus block in dogs.

The objective of the study was to devise a method to facilitate catheter placement to perform brachial plexus block in the dog. Lidocaine plus epinephrine was injected through a 3.5 French feeding tube secured in proximity of the brachial plexus. Cutaneous areas for the nerves of the distal forelimb were tested for nociceptive sensation by pinching the skin with hemostats. Five out of the 7 dogs developed a full motor and sensory block. The onset time for a full block and duration of blockade were 54 min, s = 17.1 and 39 min, s = 37.6, respectively. A second blockade was successfully achieved in 2 dogs in which the catheter was not displaced. An indwelling feeding tube is an effective way to provide blockade of the brachial plexus in the dog. The placement and the fixation of the catheter were critical for the production of a full block.

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.

Comparative cardiopulmonary effects of carfentanil-xylazine and medetomidine-ketamine used for immobilization of mule deer and mule deer/white-tailed deer hybrids.

Three mule deer and 4 mule deer/white-tailed deer hybrids were immobilized in a crossover study with carfentanil (10 microg/kg) + xylazine (0.3 mg/kg) (CX), and medetomidine (100 microg/kg) + ketamine (2.5 mg/kg) (MK). The deer were maintained in left lateral recumbency for 1 h with each combination. Deer were immobilized with MK in 230+/-68 s (mean +/- SD) and with CX in 282+/-83 seconds. Systolic, mean and diastolic arterial pressure were significantly higher with MK. Heart rate, PaO2, PaCO2, pH, and base excess were not significantly different between treatments. Base excess and pH increased significantly over time with both treatments. Both treatments produced hypoventilation (PaCO2 > 50 mm Hg) and hypoxemia (PaO2 < 60 mm Hg). PaO2 increased significantly over time with CX. Body temperature was significantly (P<0.05) higher with CX compared to MK. Ventricular premature contractions, atrial premature contractions, and a junctional escape rhythm were noted during CX immobilization. No arrhythmias were noted during MK immobilization. Quality of immobilization was superior with MK, with no observed movement present for the 60 min of immobilization. Movement of the head and limbs occurred in 4 animals immobilized with CX. The major complication observed with both of these treatments was hypoxemia, and supplemental inspired oxygen is recommended during immobilization. Hyperthermia can further complicate immobilization with CX, reinforcing the need for supplemental oxygen.

Anesthesia of wood bison with medetomidine-zolazepam/tiletamine and xylazine-zolazepam/tiletamine combinations.

This study was designed to evaluate 2 combinations for immobilization of bison. Seven wood bison received 1.5 mg/kg body weight (BW) of xylazine HCl + 1.5 mg/kg BW of zolazepam HCl and 1.5 mg/kg BW of tiletamine HCl on one occasion. The bison received 60 micrograms/kg BW of medetomidine HCl + 0.6 mg/kg BW of zolazepam HCl and 0.6 mg/kg BW of tiletamine HCL on another occasion. Xylazine was antagonized with 3 mg/kg BW of tolazoline HCl and medetomidine HCl was antagonized with 180 micrograms/kg (BW) of atipamezole HCl. Temporal characteristics of immobilization and physiological effects (acid-base status, thermoregulatory, cardiovascular, and respiratory effects) of the drug combinations were compared. Induction was significantly faster with xylazine HCl-zolazepam HCl/tiletamine HCl. Recovery following antagonist administration was significantly faster with medetomidine HCl-zolazepam HCl/tiletamine HCl. The average drug volumes required were 7.00 mL of xylazine HCl-zolazepam HCl/tiletamine HCL and 2.78 mL of medetomidine HCl-zolazepam HCl/tiletamine HCl. Hypoxemia, hypercarbia, and rumenal tympany were the major adverse effects with both drug combinations.

Anesthesia of polar bears (Ursus maritimus) with zolazepam-tiletamine, medetomidine-ketamine, and medetomidine-zolazepam-tiletamine.

A 1:1 combination (by weight) of zolazepam and tiletamine is the drug of choice for anesthetizing polar bears (Ursus maritimus), but recovery time is prolonged when additional doses are administered. Recoveries may last 24 hr and may threaten the health of the bears. We compared the anesthetic effects of zolazepam-tiletamine (ZT) with those of medetomidine-ketamine (MK) and medetomidine-zolazepam-tiletamine (MZT) in 93 free-ranging polar bears. The MZT combination was administered in smaller dose and volume, resulted in more rapid, safer, and more predictable induction, provided more reliable anesthesia, and was safely reversed with atipamezole. Frequent occurrence of sudden recoveries during anesthesia with MK limited our use of this combination. MK and MZT sometimes caused apnea and bradycardia initially and hyperthermia at increased ambient temperatures. Hypoxemia occurred transiently with all combinations. When anesthesia with ZT and MK exceeded 1 hr, frequent necessary top-up doses caused irregular physiologic function. ZT is recommended for short duration anesthesia (< or = 1 hr), but MZT is better for anesthesia of longer duration and under circumstances where reversibility is desirable.

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.

The effect of opioid and acepromazine premedication on the anesthetic induction dose of propofol in cats.

The median effective dosage (ED50) for induction of anesthesia with propofol was determined by using the up-and-down method in 31 unpremedicated cats, in 30 cats premedicated with butorphanol, 0.4 mg/kg body weight (BW), and acepromazine, 0.1 mg/kg BW, intramuscularly, and in 30 cats premedicated with morphine, 0.2 mg/kg BW, and acepromazine, 0.1 mg/kg BW, intramuscularly. The dose required for a satisfactory anesthetic induction in 50% of unpremedicated cats (ED50) was 7.22 mg/kg BW and of premedicated cats was 5.00 mg/kg BW. The reduction in dose was statistically significant in both premedicated groups compared with no premedication. There was no significant difference in ED50 between premedication regimes. Cyanosis was the most common adverse effect observed in all groups following anesthetic induction with propofol.

Comparative physiologic effects of telazol, medetomidine-ketamine, and medetomidine-telazol in captive polar bears (Ursus maritimus).

The cardiopulmonary effects of three drug combinations in polar bears (Ursus maritimus) were studied. In 1995, five adult polar bears received i.m. injections of either 8.2 +/- 1.3 mg/kg of Telazol or a combination of 159 +/- 34 microg/kg of medetomidine with 4 +/- 0.8 mg/kg of ketamine in a crossover design. Significantly higher mean arterial pressure, lower heart rate, and lower partial pressure of arterial oxygen (Pao2) occurred with medetomidine-ketamine. In 1996, six adult polar bears were immobilized with i.m. injections of either 8.2 +/- 2 mg/kg of zolazepam-tiletamine or a combination of 74.8 +/- 11.8 microg/kg of medetomidine plus 2.2 +/- 0.3 mg/kg of zolazepam-tiletamine in a crossover design. Significantly higher mean arterial pressure and lower heart rate, base excess, and Pao2 occurred with medetomidine-zolazepam-tiletamine compared with zolazepam-tiletamine alone. Hypertension, bradycardia, and decreased Pao2 were observed with both medetomidine-ketamine and medetomidine-zolazepam-tiletamine. Both combinations should be well tolerated by healthy bears, but both have the potential to produce adverse effects in animals with cardiopulmonary disease. Zolazepam-tiletamine produced minimal adverse cardiopulmonary effects, consistent with the wide margin of safety of this combination in bears. The analgesic effect of zolazepam-tiletamine was apparently poor on the basis of the marked increases in pulse rate and mean arterial pressure after noxious stimuli.

A comparison of indirect blood pressure monitoring techniques in the anesthetized cat.

OBJECTIVE: To determine the accuracy of three indirect blood pressure monitoring techniques (oscillometric technique [OS], Doppler [DOP], and optical plethysmography [OP] [blood pressure determined with a pulse oximeter waveform]) when compared with direct arterial pressure measurement in cats. STUDY DESIGN: Prospective study. ANIMAL POPULATION: Eight healthy (five female, three male), domestic short-hair cats weighing 3.5 +/- 0.8 kg METHODS: Cats were anesthetized with isoflurane. The inspired concentration of isoflurane was adjusted to produce mild hypotension (80 to 100 mm Hg direct systolic), moderate hypotension (60 to 80 mm Hg direct systolic), and severe hypotension (< 60 mm Hg direct systolic). Indirect pressure measurements were obtained from the thoracic limb and compared with concurrent direct measurement using regression analysis and a modification of Bland and Altman's technique. RESULTS: All three techniques underestimated systolic pressure. OS produced the best prediction of systolic pressure with a bias +/- precision of -15.9 +/- 8.1 mm Hg. DOP and OP were relatively inaccurate with a bias +/- precision of -25 +/- 7.4 mm Hg and -25 +/- 7.5 mm Hg. All three techniques correlated well with direct pressure with r values of 0.81, 0.88, and 0.88 for OS, DOP, and OP. DOP and OP provided an accurate prediction of direct mean arterial pressure with a bias +/- precision of -0.8 +/- 6 mm Hg and 0.6 +/- 5.5 mm Hg. Correlation was good between DOP and mean arterial pressure with r = 0.89. Correlation was also good between OP and mean arterial pressure with r = 0.90. CONCLUSIONS: OS provided the most accurate prediction of direct systolic pressure. DOP and OP provided a good prediction of mean arterial pressure in the cat. CLINICAL RELEVANCE: All three of these techniques are useful for detecting trends. Direct monitoring of blood pressure should be considered if accurate blood pressure measurement is required.

Cardiopulmonary effects of propofol and a medetomidine-midazolam-ketamine combination in mallard ducks.

OBJECTIVE: To compare safety of propofol with a medetomidine-midazolam-ketamine (MMK) combination as an anesthetic agent in mallard ducks. ANIMALS: 12 healthy adult female mallard ducks. PROCEDURE: Each duck was anesthetized twice in a crossover study design with 5 days between randomized treatments. Ducks were given medetomidine (50 micrograms), midazolam (2 mg), and ketamine (10 mg) in combination, i.v., or propofol (10 mg, i.v., followed by 1- to 4-mg boluses). Systolic, diastolic, and mean arterial pressures, heart and respiratory rates, and esophageal temperature were recorded before anesthesia and every 5 minutes after induction for 30 minutes, and at 5 minutes after reversal with atipamezole (250 micrograms) and flumazenil (25 micrograms; MMK group) or last bolus (propofol group). Arterial blood samples from 8 ducks were collected before anesthesia, 5, 10, 15, 30 minutes after induction, and after reversal or last bolus. RESULTS: 8 ducks survived the MMK anesthesia; 1 duck died and 3 ducks required resuscitation to prevent death. All ducks survived propofol anesthesia. Ducks anesthetized with either anesthetic agent had a significant increase in arterial carbon dioxide tension and decrease in arterial oxygen tension, arterial pH, and esophageal temperature. Ducks given MMK had a decrease in mean arterial pressure and respiratory rate, whereas ducks given propofol had an increase in respiratory rate. Rapid reversal of the effects of MMK was achieved with atipamezole and flumazenil. All physiologic variables, except esophageal temperature in the propofol group, returned to approximate baseline values after reversal or last bolus. CONCLUSIONS: The MMK combination in unsafe for use in ducks. Ducks can be anesthetized safely with propofol but should be monitored and ventilated artificially.

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

The objective of this study was to determine if the potent alpha 2 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, zolazepamtiletamine (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.