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.     

Evaluation of intramuscular butorphanol, azaperone, and medetomidine and nasal oxygen insufflation for the chemical immobilization of white-tailed deer, Odocoileus virginianus

Chemical immobilization of wildlife often includes opioids or cyclohexamines. These substances are problematic as a result of their required storage, handling, and record-keeping protocols. A potentially useful alternative sedation protocol includes a combination of butorphanol, azaperone, and medetomidine (BAM: 0.43 mg/kg butorphanol, 0.36 mg/kg azaperone, 0.14 mg/kg medetomidine). One risk of wildlife immobilization with any drug combination is hypoxemia. This may be of particular importance when using an alpha 2 agonist such as medetomidine because of its powerful vasoconstrictive effect. In this prospective study, the BAM combination was evaluated for chemical immobilization of white-tailed deer. Additionally, selected physiologic parameters associated with BAM immobilization, including oxygen saturation via pulse oximetry and arterial blood gas measurement, with and without nasal insufflation of oxygen at a relatively low flow of 3 L/min, were evaluated. The BAM combination resulted in a predictable onset of sedation, with a mean induction time to lateral recumbency of 9.8 +/- 3.6 min. All deer recovered smoothly within a range of 5-20 min after reversal with intramuscular administration of naltrexone, atipamazole, and tolazoline (NAT). Clinically relevant decreases in arterial partial pressure of oxygen (PaO2) and oxygen saturation (SpO2) were observed in animals not receiving supplemental oxygen, while both parameters significantly improved for oxygen-supplemented deer. Pulse oximetry with this protocol was an unreliable indicator of oxygen saturation. In this study, altitude, recumbency, hypoventilation, butorphanol- and medetomidine-specific effects, as well as the potential for alpha 2 agonist-induced pulmonary changes all may have contributed to the development of hypoxemia. Overall, capture of white-tailed deer with the BAM/NAT protocol resulted in excellent chemical immobilization and reversal. Because the BAM combination caused significant hypoxemia that is unreliably detected by pulse oximetry but that may be resolved with nasal oxygen insufflation, routine use of oxygen supplementation is recommended.     

Use of medetomidine and ketamine for immobilization of free-ranging giraffes

OBJECTIVE: To develop a dosage correlated with shoulder height (SH) in centimeters for effective immobilization of free-ranging giraffes, using a combination of medetomidine (MED) and ketamine (KET) and reversal with atipamezole (ATP). DESIGN: Prospective study. ANIMALS: 23 free-ranging giraffes. PROCEDURE: The drug combination (MED and KET) was administered by use of a projectile dart. Quality of induction, quality of immobilization, and time to recovery following injection of ATP were evaluated. Physiologic variables measured during immobilization included PaO2, PaCO2, oxygen saturation, end-tidal CO2, blood pH, indirect arterial blood pressure, heart and respiratory rates, and rectal temperature. RESULTS: Sixteen giraffes became recumbent with a dosage (mean +/- SD) of 143 +/- 29 microg of MED and 2.7 +/- 0.6 mg of KET/cm of SH. Initially, giraffes were atactic and progressed to lateral recumbency. Three giraffes required casting with ropes for data collection, with dosages of 166 +/- 5 microg of MED and 3.2 +/- 0.6 mg of KET/cm of SH. Four giraffes required administration of etorphine (n = 2) or were cast with ropes (2) for capture but remained dangerous to personnel once recumbent, precluding data collection. In giraffes successfully immobilized, physiologic monitoring revealed hypoxia and increased respiratory rates. Values for PaCO2, end-tidal CO2, and heart rate remained within reference ranges. All giraffes were hypertensive and had a slight increase in rectal temperature. Atipamezole was administered at 340 +/- 20 microg/cm of SH, resulting in rapid and smooth recoveries. CONCLUSIONS AND CLINICAL RELEVANCE: Medetomidine and KET was an effective immobilizing combination for free-ranging giraffes; however, at the dosages used, it does not induce adequate analgesia for major manipulative procedures. Quality of induction and immobilization were enhanced if the giraffe was calm. Reversal was rapid and complete following injection of ATP.     

Effect of intranasal oxygen administration on blood gas variables and outcome in neonatal calves with respiratory distress syndrome: 20 cases (2004-2006)

OBJECTIVE: To determine the effect of intranasal oxygen administration on blood gas variables and outcome in neonatal calves with respiratory distress syndrome (RDS). DESIGN: Retrospective case series. ANIMALS: 20 neonatal calves with RDS. PROCEDURES: Arterial partial pressure of oxygen (PaO(2)), arterial partial pressure of carbon dioxide, and arterial oxygen saturation (SaO(2)) before and after intranasal administration of oxygen were analyzed. RESULTS: There were significant increases in PaO(2) and SaO(2) in the first 24 hours after oxygen administration was begun, with mean +/- SD PaO(2) increasing from 38.4+/-8.8 mm Hg to 58.7+/-17.8 mm Hg during the first 3 hours of treatment. Calves with PaO(2)>55 mm Hg within the first 12 hours after oxygen administration was begun had a significantly higher survival rate (9/10) than did calves that did not reach this threshold (4/10). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that intranasal oxygen administration was a simple method of improving blood gas variables in neonatal calves with RDS and that PaO(2) could be used to predict outcome.     

Effects of ketamine on carfentanil and xylazine immobilization of white-tailed deer (Odocoileus virginianus).

Using a crossover design, the effects of the addition of ketamine to a previously determined optimal hand-injected immobilization dosage of carfentanil/xylazine were evaluated in 11 adult white-tailed deer (Odocoileus virginianus). Two i.m. ketamine dosages were evaluated: 0.15 mg/kg (low ketamine) and 0.30 mg/kg (high ketamine). Each deer was immobilized twice 2 wk apart. Inductions were video recorded and reviewed by observers, who had been blinded to drugs and dosages, who rated qualitative aspects. There were significant (P < 0.05) dosage-dependent decreases in heart rate, SaO2, and arterial pH, and a significant dosage-dependent increase in PaCO2. Induction times with both dosages were more rapid (mean 2.3 +/- 0.9 min for low ketamine and 2.3 +/- 0.6 min for high ketamine) than those reported for the same carfentanil/xylazine dosage used without ketamine. Mean quality ratings, though improved compared to those reported for carfentanil/xylazine alone, were considered "undesirable" for both dosages. Hyperthermia (temperature > 41 degrees C) was noted in 13 of 22 immobilizations. Arterial pH and PaO2 increased significantly from 10 to 20 min postrecumbency, but acidemia (pH < 7.3) was present throughout immobilization periods for all deer. There were ketamine dosage-dependent increases in respiratory components of this acidemia compared with that associated with carfentanil/xylazine alone. Possible hypoxemia was present at both sampling times for both groups, while hypercapnea (PaCO2 > 60 mm Hg) was present for the high-ketamine group only. Reversal times for naltrexone and yohimbine were rapid (mean 2.9 +/- 0.7 min for low ketamine and 3.3 +/- 0.8 min for high ketamine), with no evidence of renarcotization. Although the addition of ketamine to carfentanil/xylazine caused faster inductions and improved induction qualities, it also produced an increased incidence of hyperthermia, acidemia, hypoxemia, and hypercapnea. Supplemental oxygen and close monitoring of body temperature is recommended when using this immobilization regimen.     

Chemical restraint of fishers (Martes pennanti) with ketamine and medetomidine-ketamine.

We chemically restrained fishers (Martes pennanti) as part of a captive-management protocol designed to facilitate veterinary evaluation and treatment, and conditioning on a high-calorie diet before reintroduction in Pennsylvania. We compared the safety and efficacy of ketamine (KET) and medetomidine-ketamine (MED-KET) by monitoring immobilization intervals (induction time, down time, alert time, and recovery time) and physiologic responses (pulse rate, respiration rate, rectal temperature, blood pressure, oxygen saturation, and mean arterial pressure) during restraint. We administered MED-KET at 0.4 mg MED combined with 20.0 mg KET to males and at 0.2 mg MED combined with 10.0 mg KET to females. The x +/- SD dosages were MED 0.07 +/- 0.008 mg/kg + KET 3.7 +/- 0.5 mg/ kg for males and MED 0.07 +/- 0.007 mg/kg + KET 3.6 +/- 0.3 mg/kg for females. KET alone was administered at 100.0 mg to males and at 50.0 mg to females. resulting in x +/- SD dosages of 18.7 +/- 1.8 mg/kg for males and 19.2 +/- 2.2 mg/kg for females. Mean induction time did not differ between fishers restrained with MED-KET (4.6 min) and KET (4.5 min). However, compared with KET, MED-KET resulted in longer mean down time (36.2 vs. 142.2 min), alert time (40.8 vs. 146.8). and recovery time (81.1 vs. 199.4 min). Fishers that received MED-KET were mildly bradycardic and hypertensive compared with those that received KET. Although KET resulted in increased muscle tension and labored respiration, it would be effective for performing brief, noninvasive procedures for fishers because induction was rapid, recovery was short and calm, anesthesia was not profound, and physiologic response was generally expected on the basis of known drug pharmacology. Medetomidine-ketamine also immobilized fishers effectively, providing rapid induction, physiologic response typical to alpha2 agonism, calm recovery, and possibly a plane of anesthesia adequate for invasive procedures such as tooth removal or surgery.     

Effect of medetomidine infusion on the anaesthetic requirements of desflurane in dogs

The objective of this paper was to evaluate the effect of constant rate infusion of medetomidine on the anaesthetic requirements of desflurane in dogs. For this, six healthy dogs were studied. Measurements for baseline were taken in the awake, unsedated dogs, then each dog received intravenously (i.v.) three anaesthetic protocols: M (no medetomidine infusion), M0.5 (infusion of medetomidine at 0.5 microg/kg/h, i.v.) or M1 (infusion of medetomidine at 1 microg/kg/h, i.v.). All dogs were sedated with medetomidine (2 microg/kg, i.v.) and measurements repeated in 10 min. Induction of anaesthesia was delivered with propofol (3 mg/kg, i.v.) and maintained with desflurane for 90 min to achieve a defined surgical plane of anaesthesia in all cases. After tracheal intubation infusion of medetomidine was initiated and maintained until the end of anaesthesia. Cardiovascular, respiratory, arterial pH (pHa) and arterial blood gas tensions (PaO(2), PaCO(2)) variables were measured during the procedure. End tidal desflurane concentration (EtDES) was recorded throughout anaesthesia. Time to extubation, time to sternal recumbency and time to standing were also noted. Heart rate and respiratory rate were significantly decreased during sedation in all protocols compared to baseline values. Mean heart rate, mean arterial pressure, systolic arterial pressure, diastolic arterial pressure, respiratory rate, tidal volume, arterial oxygen saturation, end-tidal CO(2), pHa, PaO(2), and PaCO(2) during anaesthesia were similar for all protocols. EtDES for M (8.6 +/- 0.8%) was statistically higher than for M0.5 (7.6 +/- 0.5%) and M1 (7.3 +/- 0.7%) protocols. Infusion of medetomidine reduces desflurane concentration required to maintain anaesthesia in dogs.     

Cardiopulmonary assessment of medetomidine, ketamine, and butorphanol anesthesia in captive Thomson's gazelles (Gazella thomsoni).

This investigation evaluated the cardiopulmonary effects of medetomidine, ketamine, and butorphanol anesthesia in captive juvenile Thomson's gazelles (Gazella thomsoni). Butorphanol was incorporated to reduce the dose of medetomidine necessary for immobilization and minimize medetomidine-induced adverse cardiovascular side effects. Medetomidine 40.1 +/- 3.6 microg/kg, ketamine 4.9 +/- 0.6 mg/kg, and butorphanol 0.40 +/- 0.04 mg/kg were administered intramuscularly by hand injection to nine gazelles. Times to initial effect and recumbency were within 8 min postinjection. Cardiopulmonary status was monitored every 5 min by measuring heart rate, respiratory rate, indirect blood pressure, end-tidal CO2, and indirect oxygen-hemoglobin saturation by pulse oximetry. Venous blood gases were collected every 15 min postinjection. Oxygen saturations less than 90% in three gazelles suggested hypoxemia. Subsequent immobilized gazelles were supplemented with intranasal oxygen throughout the anesthetic period. Sustained bradycardia (<60 beats per minute, as compared with anesthetized domestic calves, sheep, and goats) was noted in eight of nine gazelles. Heart and respiratory rates and rectal temperatures decreased slightly, whereas systolic, mean, and diastolic blood pressure values were consistent over the anesthetic period. Mild elevations in end tidal CO2 and PCO2 suggested hypoventilation. Local lidocaine blocks were necessary to perform castrations in all seven of the gazelles undergoing the procedure. Return to sternal recumbency occurred within 7 min and return to standing occurred within 12 min after reversal with atipamezole (0.2 +/- 0.03 mg/kg) and naloxone (0.02 +/- 0.001 mg/kg). Medetomidine, ketamine, and butorphanol can be used to safely anesthetize Thomson's gazelles for routine, noninvasive procedures. More invasive procedures, such as castration, can be readily performed with the additional use of local anesthetics.     

Oral induction of anesthesia with droperidol and transmucosal carfentanil citrate in chimpanzees (Pan troglodytes).

Five chimpanzees (Pan troglodytes) initially received oral droperidol sedation (1.25 mg for a juvenile chimpanzee, body wt = 18.5 kg, and 2.5 mg for adults, body wt >20 kg, range: 18.5-71 kg) followed by transmucosal carfentanil administration at 2.0 microg/kg. This preinduction regimen was developed to produce heavy sedation or even light anesthesia in order to eliminate the need for or at least minimize the stress of darting with tiletamine/zolazepam at 3 mg/kg i.m. This study was designed to assess the safety and efficacy of transmucosal carfentanil. Once each animal was unresponsive to external stimuli, or at approximately 25 min (range 24-34 min) after carfentanil administration, naltrexone and tiletamine/zolazepam (N/T/Z) were combined into one intramuscular injection for anesthetic induction. Naltrexone was administered at 100 times the carfentanil dose in milligrams. For comparison, two chimpanzees received only droperidol, 2.5 mg p.o., followed by tiletamine/zolazepam, 3 mg/kg i.m. The preinduction period for all animals receiving carfentanil was characterized as smooth, with chimpanzees becoming gradually less active and less responsive to external stimuli. Two animals became very heavily sedated at 24 and 35 min, respectively, and were hand injected with N/T/Z. The other three chimpanzees became sternally recumbent but retained some response to stimuli, and N/T/Z was administered by remote injection with minimal response. Rectal body temperatures, pulse and respiratory rates, arterial oxygen hemoglobin saturation, and arterial blood gases were measured at initial contact (t = 0 min) and at 10-min intervals thereafter. Respiratory depression was present in all chimpanzees, regardless of protocol. Mean hemoglobin saturation was 91% for both groups. Mean partial pressure of oxygen, arterial values for carfentanil-treated and control animals were 64.4 +/- 7.6 and 63.5 +/- 6.0 at t = 0, respectively. Only the partial pressure of carbon dioxide, arterial (Paco2) and pH showed significant differences between treated and control animals. Mean Paco2 was greater and mean pH lower for the carfentanil-treated group compared with the controls at t = 0 (58.9 +/- 3.7 and 50.3 +/- 3.1 for Paco2 and 7.33 +/- 0.02 and 7.40 +/- 0.30 for pH, respectively). The results of this study suggest that oral droperidol followed by transmucosal carfentanil can be used effectively as a premedication regimen to produce profound sedation, which limits the stress of darting during parenteral anesthetic induction with tiletamine/zolazepam in chimpanzees. The main side effect of respiratory depression appears to be adequately managed by reversing the carfentanil at the time of induction.     

Cardiopulmonary effects of three different anaesthesia protocols in cats.

To develop an alternative anaesthetic regimen for cats with cardiomyopathy, the cardiopulmonary effects of three different premedication-induction protocols, followed by one hour maintenance with isoflurane in oxygen: air were evaluated in six cats. Group I: acepromazine (10 microg/kg) + buprenorphine (10 microg/kg) IM, etomidate (1-2 mg/kg) IV induction. Group II: midazolam (1 mg/kg) + ketamine (10 mg/kg) IM induction. Group III: medetomidine (1.5 mg/m2 body surface) IM, propofol (1-2 mg/kg) IV induction. Heart rate, arterial blood pressure, arterial blood gases, respiration rate, and temperature were recorded for the duration of the experiment. In group I the sedative effect after premedication was limited. In the other groups the level of sedation was sufficient. In all groups premedication resulted in a reduced blood pressure which decreased further immediately following induction. The reduction in mean arterial pressure (MAP) reached statistical significance in group I (142+/-22 to 81+/-14 mmHg) and group II (153+/-28 to 98+/-20 mmHg) but not in group III (165+/-24 to 134+/-29 mmHg). Despite the decrease in blood pressure, MAP was judged to have remained within an acceptable range in all groups. During maintenance of anaesthesia, heart rate decreased significantly in group III (from 165+/-24 to 125+/-10 b.p.m. at t=80 min). During anaesthesia the PCO2 and PO2 values increased significantly in all groups. On the basis of the results, the combination acepromazine-buprenorphine is preferred because heart rate, MAP, and respiration are acceptable, it has a limited sedative effect but recovery is smooth.     

Effects of xylazine on ventilation in horses.

The effects of 3 commonly used dosages (0.3, 0.5, and 1.1 mg/kg of body weight, IV) of xylazine on ventilatory function were evaluated in 6 Thoroughbred geldings. Altered respiratory patterns developed with all doses of xylazine, and horses had apneic periods lasting 7 to 70 seconds at the 1.1 mg/kg dosage. Respiratory rate, minute volume, and partial pressure of oxygen in arterial blood (PaO2) decreased significantly (P less than 0.001) with time after administration of xylazine, but significant differences were not detected among dosages. After an initial insignificant decrease at 1 minute after injection, tidal volume progressively increased and at 5 minutes after injection, tidal volume was significantly (P less than 0.01) greater than values obtained before injection. Partial pressure of carbon dioxide in arterial blood (PaCO2) was insignificantly increased. After administration of xylazine at a dosage of 1.1 mg/kg, the mean maximal decrease in PaO2 was 28.2 +/- 8.7 mm of Hg and 22.2 +/- 4.9 mm of Hg, measured with and without a respiratory mask, respectively. Similarly, the mean maximal increase in PaCO2 was 4.5 +/- 2.3 mm of Hg and 4.2 +/- 2.4 mm of Hg, measured with and without the respiratory mask, respectively. Significant interaction between use of mask and time was not detected, although the changes in PaO2 were slightly attenuated when horses were not masked. The temporal effects of xylazine on ventilatory function in horses should be considered in selecting a sedative when ventilation is inadequate or when pulmonary function testing is to be performed.     

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.     

Comparison of intranasal and intratracheal oxygen administration in healthy awake dogs.

Intranasal (IN) and intratracheal (IT) oxygen administration techniques were compared by measuring inspired oxygen concentrations (FIO2) and partial pressures of arterial oxygen (PaO2) in 5 healthy dogs at various IN (50, 100, 150, and 200 ml/kg of body weight/min) and IT (10, 25, 50, 100, 150, 200, and 250 ml/kg/min) oxygen flow rates. Intratracheal administration of oxygen permitted lower oxygen flow rates than IN administration. Each IT oxygen flow rate produced significantly higher FIO2 and PaO2 than the corresponding IN flow rate. An IT oxygen flow rate of 25 ml/kg/min produced FIO2 and PaO2 values equivalent to those produced by an IN oxygen flow rate of 50 ml/kg/min. An IT oxygen flow rate of 50 ml/kg/min produced FIO2 and PaO2 values equivalent to those produced by IN oxygen flow rates of 100 and 150 ml/kg/min. All IT oxygen flow rates greater than or equal to 100 ml/kg/min produced FIO2 and PaO2 values that were greater than FIO2 and PaO2 values produced by IN oxygen flow rates of 200 ml/kg/min. The lowest flow rates studied (50 ml/kg/min, IN, and 10 ml/kg/min, IT) produced PaO2 capable of maintaining 97% hemoglobin saturation, which should be adequate for most clinical situations. Arterial blood gas analysis and FIO2 measurements are necessary to accurately guide oxygen flow adjustments to achieve the desired PaO2 and to prevent oxygen toxicity produced by excessive FIO2.     

Effects of tiletamine/zolazepam-romifidine-atropine in ocelots (Leopardus pardalis)

OBJECTIVES: To evaluate the effects of a combination of tiletamine-zolazepam-romifidine-atropine in ocelots. DESIGN: Prospective experimental trial. ANIMALS: Eight captive adult ocelots (three females and five males). METHODS: Calculated doses of tiletamine-zolazepam (3.75 mg kg(-1)), romifidine (50 microg kg(-1)) and atropine (0.04 mg kg(-1)) were administered intramuscularly. After immobilization, animals were weighed and the real doses determined. Heart rate, respiratory frequency, noninvasive systolic, diastolic, and mean arterial pressure, arterial oxygen hemoglobin saturation, and rectal temperature were measured. Data were analyzed by means of anova for repeated measures, followed by the Tukey test to compare values over time. RESULTS: Doses administered were 3.4 +/- 0.6 mg kg(-1) of tiletamine-zolazepam, 0.04 +/- 7.0 mg kg(-1) of romifidine, and 0.03 +/- 0.007 mg kg(-1) of atropine. The mean time to recumbency and duration of immobilization were 7.0 +/- 4.5 and 109.2 +/- 27.9 minutes, respectively. The median times to standing and walking were 52.3 [0-90] and 2.3 [0-69.3] minutes, respectively. A decrease in heart rate was observed 45 minutes following drug administration. Arterial blood pressure was maintained during the study. CONCLUSIONS AND CLINICAL RELEVANCE: This protocol produced good immobilization in ocelots with minimal changes over time in cardiovascular parameters.     

Field anesthesia of wild ring-tailed lemurs (Lemur catta) using tiletamine-zolazepam, medetomidine, and butorphanol

Telazol has been commonly used for field anesthesia of wild lemurs, including ring-tailed lemurs (Lemur catta). Telazol alone provides good induction, but doesn't cause adequate muscle relaxation and sedation for collecting consistent somatic measurements and high-quality dental impressions that are sometimes needed. Variability in induction response has been seen between individuals that have received similar dosages, with young lemurs seeming to need more anesthetic than mature lemurs. This investigation evaluated Telazol induction in young (2.0-4.9 yr) and mature (> or = 5.0 yr) ring-tailed lemurs and compared postinduction supplementation with medetomidine or medetomidine-butorphanol. Forty-eight lemurs were anesthetized with Telazol administered via blow dart; then, 20 min after darting, they were supplemented via hand injection with either medetomidine (0.04 mg/ kg) or medetomidine-butorphanol (0.04 mg/kg and 0.2 mg/kg, respectively). The odds ratio for young lemurs to need more than one dart for induction, relative to mature lemurs, was 3.8, even though the initial dose of Telazol received by young lemurs (19 +/- 7 mg/kg) was significantly higher than the initial dose administered to mature lemurs (12 +/- 5 mg/kg). The total Telazol dosage was also significantly different between young lemurs (33 +/- 15 mg/kg) and mature lemurs (18 +/- 9 mg/kg). Both medetomidine and medetomidine-butorphanol provided good muscle relaxation and sedation for all procedures. Physiologic values were similar between the two protocols. Oxygen saturation by pulse oximetry was generally good, although there were a few SaO2 values < 90%. Recoveries were smooth, but long. Time to head up was correlated with total Telazol dosage in mature lemurs. In young lemurs, time to standing was correlated with Telazol induction dosage and time of last Telazol administration. Lemurs that received hand injections of Telazol took longer to recover than those that did not. Further refinements are needed to increase induction reliability and to decrease recovery time, particularly in young lemurs.     

Immobilisation of impala (Aepyceros melampus) with a ketamine hydrochloride/medetomidine hydrochloride combination, and reversal with atipamezole hydrochloride

A combination of medetomidine hydrochloride (medetomidine) and ketamine hydrochloride (ketamine) was evaluated in 16 boma-confined and 19 free-ranging impalas (Aepyceros melampus) to develop a non-opiate immobilisation protocol. In free-ranging impala a dose of 220 +/- 34 microg/kg medetomidine and 4.4 +/- 0.7 mg/kg ketamine combined with 7500 IU of hyaluronidase induced recumbency within 4.5 +/- 1.5 min, with good muscle relaxation, a stable heart rate and blood pH. PaCO2 was maintained within acceptable ranges. The animals were hypoxic with reduced oxygen saturation and low PaO2 in the presence of an elevated respiration rate, therefore methods for respiratory support are indicated. The depth of sedation was adequate for minor manipulations but additional anaesthesia is indicated for painful manipulations. Immobilisation was reversed by 467 +/- 108 microg/kg atipamezole hydrochloride (atipamezole) intramuscularly, but re-sedation was observed several hours later, possibly due to a low atipamezole:medetomidine ratio of 2:1. Therefore, this immobilisation and reversal protocol would subject impalas to possible predation or conspecific aggression following reversal if they were released into the wild. If the protocol is used on free-ranging impala, an atipamezole:medetomidine ratio of 5:1 should probably be used to prevent re-sedation.     

Anesthetic and cardiopulmonary effects of total intravenous anesthesia using a midazolam, ketamine and medetomidine drug combination in horses

The anesthetic and cardiopulmonary effects of midazolam, ketamine and medetomidine for total intravenous anesthesia (MKM-TIVA) were evaluated in 14 horses. Horses were administered medetomidine 5 microg/kg intravenously as pre-anesthetic medication and anesthetized with an intravenous injection of ketamine 2.5 mg/kg and midazolam 0.04 mg/kg followed by the infusion of MKM-drug combination (midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.1 mg/ml). Nine stallions (3 thoroughbred and 6 draft horses) were castrated during infusion of MKM-drug combination. The average duration of anesthesia was 38 +/- 8 min and infusion rate of MKM-drug combination was 0.091 +/- 0.021 ml/kg/hr. Time to standing after discontinuing MKM-TIVA was 33 +/- 13 min. The quality of recovery from anesthesia was satisfactory in 3 horses and good in 6 horses. An additional 5 healthy thoroughbred horses were anesthetized with MKM- TIVA in order to assess cardiopulmonary effects. These 5 horses were anesthetized for 60 min and administered MKM-drug combination at 0.1 ml/kg/hr. Cardiac output and cardiac index decreased to 70-80%, stroke volume increased to 110% and systemic vascular resistance increased to 130% of baseline value. The partial pressure of arterial blood carbon dioxide was maintained at approximately 50 mmHg while the arterial partial pressure of oxygen pressure decreased to 50-60 mmHg. MKM-TIVA provides clinically acceptable general anesthesia with mild cardiopulmonary depression in horses. Inspired air should be supplemented with oxygen to prevent hypoxemia during MKM-TIVA.     

Cardiopulmonary and acid-base effects of desflurane and sevoflurane in spontaneously breathing cats

The cardiopulmonary effects of desflurane and sevoflurane anesthesia were compared in cats breathing spontaneously. Heart (HR) and respiratory (RR) rates; systolic (SAP), diastolic (DAP) and mean arterial (MAP) pressures; partial pressure of end tidal carbon dioxide (PETCO2), arterial blood pH (pH), arterial partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2); base deficit (BD), arterial oxygen saturation (SaO2) and bicarbonate ion concentration (HCO3) were measured. Anesthesia was induced with propofol (8+/-2.3mg/kg IV) and maintained with desflurane (GD) or sevoflurane (GS), both at 1.3 MAC. Data were analyzed by analysis of variance (ANOVA), followed by the Tukey test (P<0.05). Both anesthetics showed similar effects. HR and RR decreased when compared to the basal values, but remained constant during inhalant anesthesia and PETCO2 increased with time. Both anesthetics caused acidemia and hypercapnia, but BD stayed within normal limits. Therefore, despite reducing HR and SAP (GD) when compared to the basal values, desflurane and sevoflurane provide good stability of the cardiovascular parameters during a short period of inhalant anesthesia (T20-T60). However, both volatile anesthetics cause acute respiratory acidosis in cats breathing spontaneously.     

Detomidine-Propofol Anesthesia for Abdominal Surgery in Horses

OBJECTIVE: To evaluate propofol for induction and maintenance of anesthesia, after detomidine premedication, in horses undergoing abdominal surgery for creation of an experimental intestinal adhesion model. STUDY DESIGN: Prospective study. ANIMALS: Twelve horses (424 +/- 81 kg) from 1 to 20 years of age (5 females, 7 males). METHODS: Horses were premedicated with detomidine (0.015 mg/kg i.v.) 20 to 25 minutes before induction, and a propofol bolus (2 mg/kg i.v.) was administered for induction. Propofol infusion (0.2 mg/kg/min i.v.) was used to maintain anesthesia. The infusion rate was adjusted to maintain an acceptable anesthetic plane as determined by muscle relaxation, occular signs, response to surgery, and cardiopulmonary responses. Oxygen (15 L/min) was insufflated through an endotracheal tube as necessary to maintain the SpO2 greater than 90%. Systolic (SAP), mean (MAP), and diastolic (DAP) arterial pressures, heart rate (HR), electrocardiogram (ECG), respiratory rate (RR), SpO2 (via pulse oximetry), and nasal temperature were recorded at 15 minute intervals, before premedication and after induction of anesthesia. Arterial blood gas samples were collected at the same times. Objective data are reported as mean (+/-SD); subjective data are reported as medians (range). RESULTS: Propofol (2.0 mg/kg i.v.) induced anesthesia (mean bolus time, 85 sec) within 24 sec (+/-22 sec) after the bolus was completed. Induction was good in 10 horses; 2 horses showed signs of excitement and these two inductions were not smooth. Propofol infusion (0.18 mg/kg/min +/- 0.04) was used to maintain anesthesia for 61 +/- 19 minutes with the horses in dorsal recumbency. Mean SAP, DAP, and MAP increased significantly over time from 131 to 148, 89 to 101, and 105 to 121 mm Hg, respectively. Mean HR varied over time from 43 to 45 beats/min, whereas mean RR increased significantly over anesthesia time from 4 to 6 breaths/min. Mean arterial pH decreased from a baseline of 7.41 +/- 0.07 to 7.30 +/- 0.05 at 15 minutes of anesthesia, then increased towards baseline values. Mean PaCO2 values increased during anesthesia, ranging from 47 to 61 mm Hg whereas PaO2 values decreased from baseline (97 +/- 20 mm Hg), ranging from 42 to 57 mm Hg. Muscle relaxation was good and no horses moved during surgery: Recovery was good in 9 horses and acceptable in 3; mean recovery time was 67 +/- 29 minutes with 2.4 +/- 2.4 attempts necessary for the horses to stand. CONCLUSIONS: Detomidine-propofol anesthesia in horses in dorsal recumbency was associated with little cardiovascular depression, but hypoxemia and respiratory depression occurred and some excitement was seen on induction. CLINICAL RELEVANCE: Detomidine-propofol anesthesia is not recommended for surgical procedures in horses if dorsal recumbency is necessary and supplemental oxygen is not available (eg, field anesthesia).     

Dexmedetomidine or medetomidine premedication before propofol-desflurane anaesthesia in dogs

The objective of this study was to evaluate dexmedetomidine as a premedicant in dogs prior to propofol-desflurane anaesthesia, and to compare it with medetomidine. Six healthy dogs were anaesthetized. Each dog received intravenously (i.v.) five preanaesthetic protocols: D1 (dexmedetomidine, 1 microg/kg, i.v.), D2 (dexmedetomidine, 2 microg/kg, i.v.), M1 (medetomidine, 1 microg/kg, i.v.), M2 (medetomidine, 2 microg/kg, i.v.), or M4 (medetomidine, 4 microg/kg, i.v.). Anaesthesia was induced with propofol (2.3-3.3 mg/kg) and maintained with desflurane. The following variables were studied: heart rate (HR), mean arterial pressure, systolic arterial pressure, diastolic arterial pressure, respiratory rate (RR), arterial oxygen saturation, end-tidal CO2, end-tidal concentration of desflurane (EtDES) required for maintenance of anaesthesia and tidal volume. Arterial blood pH (pHa) and arterial blood gas tensions (PaO2, PaCO2) were measured during anaesthesia. Time to extubation, time to sternal recumbency and time to standing were also recorded. HR and RR decreased significantly during sedation in all protocols. Cardiorespiratory variables during anaesthesia were statistically similar for all protocols. EtDES was significantly different between D1 (8.1%) and D2 (7.5%), and between all doses of medetomidine. Desflurane requirements were similar for D1 and M2, and for D2 and M4 protocols. No statistical differences were observed in recovery times. The combination of dexmedetomidine, propofol and desflurane appears to be effective for induction and maintenance of general anaesthesia in healthy dogs.