Effect of yohimbine on xylazine-ketamine anesthesia in cats

Xylazine and ketamine are an anesthetic combination used in feline practice for routine surgical procedures. In a controlled study, we evaluated the effects of yohimbine, an antagonist of xylazine, on the anesthesia induced by this anesthetic combination in cats. Two intramuscular doses of xylazine and ketamine (2.2 mg of xylazine/kg plus 6.6 mg of ketamine/kg and 4.4 mg of xylazine/kg plus 6.6 mg of ketamine/kg) caused approximately 60 and 100 minutes of anesthesia, respectively, in control cats. When yohimbine (0.1 mg/kg) was given intravenously 45 minutes after ketamine administration, the cats regained consciousness within 3 minutes. They were ambulatory 1 to 2 minutes after regaining consciousness. Yohimbine also reversed the bradycardia and respiratory depression elicited by xylazine-ketamine. The results indicated that yohimbine may be useful for controlling the duration of xylazine-ketamine anesthesia in cats.     

Effects of xylazine and acetylpromazine upon induced ventricular fibrillation in dogs anesthetized with thiamylal and halothane.

Ventricular arryhythmias including ventricular fibrillation were produced with epinephrine in dogs induced to an anesthetic state with thiamylal and maintained with halothane. In dogs given (premedicated) xylazine 20 minutes prior to anesthesia, ventricular arrhythmias, including ventricular fibrillation, were induced with much smaller doses of epinephrine than in nonpremedicated dogs. Dogs premedicated with acetylpromazine 20 minutes prior to anesthesia with thiamylal and halothane displayed protection from epinephrine-induced arrhythmias. Caution is advised from using xylazine in the presence of halothane if epinephrine is to be administered.     

Neurohormonal and metabolic effects of medetomidine compared with xylazine in healthy cats

The purpose of this study was to investigate and compare the effects of medetomidine and xylazine on some neurohormonal and metabolic variables in healthy cats. Five cats were used repeatedly in each of 11 groups, which were injected intramuscularly with physiological saline solution (control), 20, 40, 80, 160, and 320 microg/kg of medetomidine, and 0.5, 1, 2, 4, and 8 mg/kg of xylazine. Blood samples were taken over 24 h from the jugular vein for determination of plasma glucose, insulin, cortisol, epinephrine, norepinephrine, glucagon, and nonesterified fatty acid concentrations. Both medetomidine and xylazine induced remarkable hyperglycemia that was dose-dependent except for the response to medetomidine from 0 to 3 h. Both agents suppressed epinephrine and norepinephrine release but not in a dose-dependent manner at the tested dosages. Both agents inhibited insulin release and lipolysis, with similar potency, and tended to suppress cortisol release. The glucagon levels did not change significantly in any of the groups. These results suggest that the effects of medetomidine and xylazine on glucose metabolism and catecholamine release may not be due only to the actions mediated by alpha2-adrenoceptors.     

Analgesic efficacy of preoperative administration of meloxicam or butorphanol in onychectomized cats

OBJECTIVE: To determine analgesic efficacy and adverse effects of preemptive administration of meloxicam or butorphanol in cats undergoing onychectomy or onychectomy and neutering. DESIGN: Randomized controlled study. ANIMALS: 64 female and 74 male cats that were 4 to 192 months old and weighed 1.09 to 705 kg (2.4 to 15.5 lb). PROCEDURE: Cats received meloxicam (0.3 mg/kg [0.14 mg/lb], s.c.) or butorphanol (0.4 mg/kg [0.18 mg/lb], s.c.) 15 minutes after premedication and prior to anesthesia. A single blinded observer measured physiologic variables, assigned analgesia and lameness scores, and withdrew blood samples for each cat at baseline and throughout the 24 hours after surgery. Rescue analgesia (butorphanol, 0.4 mg/kg, i.v. or s.c.) or administration of acepromazine (0.025 to 0.05 mg/kg [0.011 to 0.023 mg/lb], i.v.) was allowed. RESULTS: Meloxicam-treated cats were less lame and had lower pain scores. Cortisol concentration was higher at extubation and lower at 1, 5, and 12 hours in the meloxicam-treated cats. Fewer meloxicam-treated cats required rescue analgesia at 3, 5, 12, and 24 hours after extubation. General impression scores were excellent or good in 75% of meloxicam-treated cats and 44% of butorphanol-treated cats. There was no treatment effect on buccal bleeding time; PCV and BUN concentration decreased in both groups, and glucose concentration decreased in meloxicam-treated cats. CONCLUSIONS AND CLINICAL RELEVANCE: Preoperative administration of meloxicam improved analgesia for 24 hours without clinically relevant adverse effects in cats that underwent onychectomy or onychectomy and neutering and provided safe, extended analgesia, compared with butorphanol.     

Reversal of pentobarbital anesthesia with 4-aminopyridine and yohimbine in cats pretreated with acepromazine and xylazine

In 2 separate experiments, groups of atropinized cats (6 cats/group) were given acepromazine (0.25 mg/kg of body weight) or xylazine (2.2 mg/kg) IM and anesthetized with pentobarbital. The mean dose of pentobarbital was decreased approximately 36% by acepromazine, and approximately 80% by xylazine, compared with published doses. Anesthetized cats were given IV saline solution (control groups) or were given the antagonists 4-aminopyridine (4-AP; 0.5 mg/kg), yohimbine (0.4 mg/kg), or 4-AP + yohimbine (0.5 mg/kg and 0.4 mg/kg, respectively). In acepromazine-treated cats, 4-AP + yohimbine was the most effective antagonist; arousal and walking occurred in an average of 10.4 minutes and 91.7 minutes, respectively. Yohimbine enhanced the antagonistic effects of 4-AP. In xylazine-treated cats, yohimbine was an effective antagonist; arousal and walking occurred in an average of 2.8 minutes and 12.8 minutes, respectively. Yohimbine did not enhance the antagonistic effects of 4-AP. Mean respiratory rates were decreased by acepromazine, but were increased by xylazine. Thus, respiratory rate depression by pentobarbital was not as marked with xylazine as it was with acepromazine. Changes in mean heart rate were not remarkable with either sedative, and cardiac irregularities were not palpated or auscultated. In healthy cats, the duration of pentobarbital anesthesia can be controlled by 4-AP + yohimbine (acepromazine-pretreated cats) or by yohimbine alone (xylazine-pretreated cats).     

Effect of postoperative analgesic protocol on limb function following onychectomy in cats

OBJECTIVE: To evaluate the analgesic effects of topical administration of bupivacaine, i.m. administration of butorphanol, and transdermal administration of fentanyl in cats undergoing onychectomy. DESIGN: Prospective study. ANIMALS: 27 healthy adult cats. PROCEDURE: Cats were randomly assigned to 1 of 3 treatment groups, and unilateral (left forefoot) onychectomy was performed. Gait analysis was performed before and 1, 2, 3, and 12 days after surgery. All forces were expressed as a percentage of the cat's body weight. RESULTS: On day 2, peak vertical force (PVF) was significantly decreased in cats treated with bupivacaine, compared with cats treated with butorphanol or fentanyl. The ratio of left forelimb PVF to PVF of the other 3 limbs was significantly lower on day 2 in cats treated with bupivacaine than in cats treated with fentanyl. No significant differences in vertical impulse (VI) were found between groups on any day. Values for PVF, VI, and the PVF ratio increased progressively following surgery. However, for all 3 groups, values were still significantly decreased, compared with baseline values, 12 days after surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that limb function following onychectomy is significantly better in cats treated with fentanyl transdermally or butorphanol i.m. than in cats treated with bupivacaine topically. Regardless of the analgesic regimen, limb function was still significantly reduced 12 days after surgery, suggesting that long-term analgesic treatment should be considered for cats undergoing onychectomy. Irrigation of the surgical incisions with bupivacaine prior to wound closure cannot be recommended as the sole method for providing postoperative analgesia in cats undergoing onychectomy.     

Effect of xylazine on the arrhythmogenic dose of epinephrine in thiamylal/halothane-anesthetized horses.

The effect of xylazine on the arrhythmogenic dose of epinephrine (ADE) was studied in 9 horses. Anesthesia was induced by administration of guaifenesin (50 mg/kg of body weight, IV) followed by thiamylal (4 to 6 mg/kg, IV) and was maintained at 1 minimal alveolar concentration (MAC) of halothane (0.89%). Base apex ECG and facial artery pressure were recorded. Epinephrine was infused in a sequence of arithmetically spaced increasing rates (initial rate 0.25 micrograms/kg/min) for a maximum of 10 minutes. The ADE was defined as the lowest epinephrine infusion rate to the nearest 0.25 micrograms/kg/min at which at least 4 premature ventricular depolarizations occurred in a 15-second period. Xylazine (1.1 mg/kg, IV) was administered after the control ADE was determined. Xylazine did not significantly alter the ADE (control, 1.12 +/- 0.38 micrograms/kg/min; xylazine, 1.21 +/- 0.46 micrograms/kg/min). Blood pressure increased transiently for 8 minutes after xylazine administration. Baseline systolic and diastolic arterial pressures and heart rate were not significantly different from control baseline pressures and heart rate 15 minutes after xylazine administration. Blood pressure and heart rate increased significantly during control and xylazine ADE determinations. Significant differences in pH, PaO2, PaCO2, or base excess were not observed between baseline and ADE in the control or xylazine groups. One horse developed atrial fibrillation, and 2 horses developed ventricular fibrillation during ADE determinations.     

The effects of different anesthetics on blood steroid concentrations in domestic tom-cats

Testosterone and androstenedione were measured in the plasma of mature tom-cats before, during and after anesthesia with thiopentone, ketamine, xylazine and alphaxolone/alphadolone. Samples were collected via an indwelling jugular catheter at 30 min intervals before anesthesia (5 samples) and during the recovery phase (8 samples), and at intervals of 15 min during anesthesia (7 samples). Thiopentone and ketamine anesthesia significantly depressed testosterone and androstenedione concentrations during and after anesthesia. Xylazine significantly increased testosterone concentrations during anesthesia but they returned to pre-anesthetic concentrations during recovery. Androstenedione concentrations were significantly depressed during the recovery phase from xylazine anesthesia. Alphaxolone/alphadolone anesthesia had no significant effect of testosterone concentrations but significantly increased and androstenedione concentrations during anesthesia and recovery. Testosterone and androstenedione concentrations in cats were significantly altered by these 4 commonly used anesthetics and this must be taken into account if hormone concentrations are measured while cats are anesthetised.     

Evaluation of short-term limb function following unilateral carbon dioxide laser or scalpel onychectomy in cats

OBJECTIVE: To evaluate short-term postoperative forelimb function after scalpel and laser onychectomy in cats. DESIGN: Randomized, prospective study. ANIMALS: 20 healthy adult cats. PROCEDURES: Cats were randomly assigned to the laser (n = 10) or scalpel (10) onychectomy group. Unilateral left forelimb onychectomy was performed. In the scalpel group, a tourniquet was used during surgery and a bandage was applied after surgery. Pressure platform gait analysis was performed prior to and 1, 2, 3, and 12 days after onychectomy. Peak vertical force (PVF), vertical impulse, and the ratio of the PVF of the left forelimb to the sum of the remaining limbs (PVF ratio) were used as outcome measures. RESULTS: The laser onychectomy group had significantly higher ground reaction forces on days 1 and 2 and significantly higher PVF ratio on day 12, compared with the scalpel group. Similarly, significant differences were found in change in ground reaction forces on days 1 and 2 and the PVF ratio on day 12, compared with day -1. No cats required rescue analgesia during the course of the study. One cat in the laser group had signs of depression and was reluctant to walk on day 2 after surgery, had physical examination findings consistent with cardiac insufficiency, and was euthanized. CONCLUSIONS AND CLINICAL RELEVANCE: Cats had improved limb function immediately after unilateral laser onychectomy, compared with onychectomy with a scalpel, tourniquet, and bandage. This improved limb function may result from decreased pain during the 48 hours following unilateral laser onychectomy.     

Anesthetic interaction in cardiovascular research models: effects of xylazine and pentobarbital in cats

The effects of xylazine given to cats before anesthetization was induced with pentobarbital were determined. Cardiac hemodynamic variables and regional blood flow rates in the heart and other organs were measured, using radiolabeled microspheres. Two groups, each of 10 cats, were included in the study: one group (group 1) was anesthetized with pentobarbital given intraperitoneally and subsequently given xylazine; the other group (group 2) was first given 1 mg of xylazine/kg, IM, and then anesthetized with pentobarbital given IV. Anesthesia was maintained in both groups with nitrous oxide. The preanesthetic administration of xylazine decreased the amount of pentobarbital used for surgical anesthesia by approximately 50%. It also resulted in decreased heart rate, cardiac contractility, and cardiac output and increased left ventricular end-diastolic pressure, compared with those values in cats given pentobarbital (group 1). After the latter cats (anesthetized with pentobarbital) were given xylazine, heart rate, cardiac contractility, and cardiac output decreased and left ventricular end-diastolic pressure increased to values similar to those found in group 2 (given xylazine before anesthetization). Myocardial tissue blood flow rates in the left and right ventricles were lower in the cats of group 2. In group 1 cats, myocardial blood flow rates decreased when xylazine was subsequently added. Blood flow rates in the kidneys and gastrointestinal tract were generally decreased by xylazine. Xylazine profoundly changed cardiac hemodynamic function and perfusion in the heart, as well as several other organ systems, because of marked cardiodepression.     

Comparison of transdermal administration of fentanyl versus intramuscular administration of butorphanol for analgesia after onychectomy in cats

OBJECTIVE: To compare postoperative discomfort assessed by subjective pain score and plasma cortisol concentrations in cats undergoing onychectomy that received analgesia by use of transdermal fentanyl (TDF) patches or an i.m. injection of butorphanol. DESIGN: Randomized prospective clinical trial. ANIMALS: 22 client-owned cats weighing 2.2 to 5 kg (4.84 to 11 lb) undergoing onychectomy. PROCEDURE: Researchers were blinded to which cats received a TDF patch (25 microg/h) 18 to 24 hours prior to surgery or an i.m. injection of butorphanol (0.2 mg/kg (0.09 mg/lb]) at the time of sedation, immediately following extubation, and at 4-hour intervals thereafter for 12 hours. Clinical variables, plasma cortisol concentration, and pain scores were evaluated and recorded 24 hours prior to surgery, at extubation, and 2, 4, 8, 12, 24, 36, and 48 hours after surgery. RESULTS: The TDF group had a lower pain score than the butorphanol group only at 8 hours after surgery. Both groups had significantly lower mean plasma cortisol concentrations 0, 24, 36, and 48 hours after surgery, compared with mean plasma cortisol concentrations prior to surgery. No significant differences in appetite or response to handling the feet were observed between the 2 groups. CONCLUSIONS AND CLINICAL RELEVANCE: Our data did not reveal a difference in pain relief between administration of TDF and butorphanol. Plasma cortisol concentrations were not different between groups. Fentanyl appeared to provide equivalent analgesia to butorphanol in cats undergoing onychectomy. The primary advantage of using a TDF patch is that repeated injections are not required.     

Cardiovascular Effects of Enoximone and Epinephrine on Heparin Reversal With Protamine in Conscious Dogs

Objective—To compare enoximone with epinephrine as treatments for the cardiotoxic effects of protamine sulfate.
Study Design—Prospective randomized study.
Animal Population—12 healthy cross-bred dogs weighing 23 ± 4 kg.
Methods—The dogs were anesthetized with xylazine and ketamine to allow instrumentation. Femoral arterial and venous catheters were inserted for pressure monitoring and to allow drug infusion. A thermodilution catheter mounted with a fast response thermistor was inserted into the pulmonary artery via the jugular vein to measure cardiac output and right ventricular volumes. Heparin 300 units/kg followed by protamine 4.5 mg/kg were administered 45 minutes after the xylazine/ketamine. Four animals were not treated (controls), four received enoximone, and four were given epinephrine. Cardiopulmonary parameters were monitored for a period of 30 minutes.
Results—Cardiac index was 104 ± 15 mL/kg/min in the enoximone group, 72 ± 13 mL/kg/ min in the epinephrine group, and 63 ± 10 mL/kg/min in the control group ( P < .05 enoximone versus control and epinephrine). Right ventricular end systolic volume was 18 ± 3, 27 ± 4, and 29 ± 6 mL in the enoximone, epinephrine, and control groups ( P < .05 enoximone versus control and epinephrine). There were no differences in mean arterial pressure or pulmonary and systemic vascular resistance between the groups.
Conclusions and Clinical Relevance—In this study, enoximone was more effective than epinephrine at reversing the hemodynamic changes associated with protamine sulfate administration.     

Comparison of four drug combinations for total intravenous anesthesia of horses undergoing surgical removal of an abdominal testis

OBJECTIVE: To evaluate anesthetic effects of 4 drug combinations used for total intravenous anesthesia of horses undergoing surgical removal of an abdominal testis. DESIGN: Clinical trial. ANIMALS: 32 healthy cryptorchid horses. PROCEDURE: Horses were sedated with xylazine and butorphanol and were randomly assigned to 1 of 4 groups: induction of anesthesia with ketamine and diazepam and maintenance with bolus administration of ketamine and xylazine (KD/KX); induction and maintenance of anesthesia with bolus administration of tiletamine-zolazepam, ketamine, and detomidine (TKD); induction and maintenance of anesthesia with continuous infusion of xylazine, guaifenesin, and ketamine; and induction and maintenance of anesthesia with continuous infusion of guaifenesin and thiopental. Horses that moved 3 consecutive times in response to surgical stimulation or for which surgery time was > 60 minutes were administered an inhalant anesthetic, and data from these horses were excluded from analysis. RESULTS: Quality of induction was not significantly different among groups. Muscle relaxation and analgesia scores were lowest for horses given KD/KX, but significant differences among groups were not detected. Horses anesthetized with TKD had a significantly greater number of attempts to stand, compared with the other groups, and mean quality of recovery from anesthesia for horses in the TKD group was significantly worse than for the other groups. Anesthesia, surgery, and recovery times were not significantly different among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that all 4 drug combinations can be used to induce short-term anesthesia for abdominal cryptorchidectomy in horses. However, horses receiving TKD had a poorer recovery from anesthesia, often requiring assistance to stand.     

Comparison of quality of induction of anaesthesia between intramuscularly administered ketamine, intravenously administered ketamine and intravenously administered propofol in xylazine premedicated cats

The quality of induction of general anesthesia produced by ketamine and propofol, 2 of the most commonly used anaesthetic agents in cats, was assessed. Eighteen cats admitted for elective procedures were randomly assigned to 3 groups and then premedicated with xylazine 0.75 mg/kg intramuscularly before anaesthesia was induced with ketamine 15 mg/kg intramuscularly (KetIM group), ketamine 10 mg/kg intravenously (KetIV group) or propofol 4 mg/kg intravenously (PropIV group). Quality of induction of general anaesthesia was determined by scoring ease of intubation, degree of struggling, and vocalisation during the induction period. The quality of induction of anaesthesia of intramuscularly administered ketamine was inferior to that of intravenously administered ketamine, while intravenously administered propofol showed little difference in quality of induction from ketamine administered by both the intramuscular and intravenous routes. There were no significant differences between groups in the ease of intubation scores, while vocalisation and struggling were more common in cats that received ketamine intramuscularly than in those that received intravenously administered ketamine or propofol for induction of anaesthesia. Laryngospasms occurred in 2 cats that received propofol. The heart rates and respiratory rates decreased after xylazine premedication and either remained the same or decreased further after induction for all 3 groups, but remained within normal acceptable limits. This study indicates that the 3 regimens are associated with acceptable induction characteristics, but administration of ketamine intravenously is superior to its administration intramuscularly and laryngeal desensitisation is recommended to avoid laryngospasms.     

Clinical assessment of repeated propofol-associated anesthesia in cats

OBJECTIVE: To assess the effects of repeated episodes of propofol-associated anesthesia on quality of recovery from anesthesia, clinical status, and erythrocyte physiology in cats. DESIGN: Original study. ANIMALS: 37 cats undergoing short-duration anesthesia for radiotherapy. PROCEDURES: Twice daily on 5 consecutive days, 13 cats with squamous cell carcinoma of the nasal planum (group 1) underwent anesthesia: first via administration of propofol or a midazolam (0.2 mg/kg [0.09 mg/lb])-propofol combination and then via administration of ketamine and midazolam each day (latter data were not analyzed). During a 19-day period, 24 cats with vaccine associated sarcoma (group 2) were anesthetized 12 times with propofol or a midazolam-propofol combination. Anesthesia was maintained with propofol in both groups. Hematologic analysis was performed before, during, and on completion of radiotherapy; changes in Hct and hemoglobin concentration between groups were compared. RESULTS: Mean duration of anesthesia was 8.1 minutes (range, 5 to 20 minutes); no adverse events were detected during recovery. Total dose of propofol administered did not differ between groups 1 (6.34 mg/kg [2.88 mg/lb]) and 2 (4.71 mg/kg [2.14 mg/lb]). Midazolam administration decreased the propofol dose by 26%. Overall decreases from baseline in Hct and hemoglobin concentration were not significantly different between the 2 groups, nor clinically important; however, compared with baseline, values in group 2 were significantly lower after 6 and 12 anesthetic episodes for both protocols. Heinz bodies were identified in low numbers in both groups during radiotherapy. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that repeated propofol-associated short-duration anesthesia does not lead to clinically relevant hematologic changes in cats undergoing short-duration radiotherapy.     

A comparison of preoperative tramadol and morphine for the control of early postoperative pain in canine ovariohysterectomy

Objective To compare morphine with tramadol for the management of early postoperative pain following ovariohysterectomy after pyometra in dogs. Study design Prospective randomized blinded clinical trial. Animals Thirty female dogs, 2–14 years old. Methods Animals were randomly divided into two equal groups. Group 1 received 0.2 mg kg^?1 of morphine IV and group 2 received 2 mg kg^?1 of tramadol IV after the induction of anesthesia. The dogs were premedicated with acepromazine, and anesthesia was induced with intravenous midazolam and ketamine. Isoflurane was used for the maintenance of anesthesia. The variables measured were: analgesia; sedation; cardiac and respiratory rates; arterial blood pressure; end‐tidal isoflurane and carbon dioxide (Pe ′CO₂); oxyhemoglobin saturation (SpO₂); plasma catecholamines; serum cortisol and glucose concentrations; pH and blood gases. The animals were monitored for 6 hours after the administration of the analgesic agent. Results There were no differences between the two groups with regard to analgesia, sedation, SpO₂, pH and blood gases, cardiovascular variables, glucose, catecholamine and cortisol concentrations. Forty minutes postopioid administration, the end‐tidal isoflurane concentration was significantly lower in the morphine‐treated group as compared to the tramadol group. At 30 minutes following opioid injection, Pe ′CO₂ was significantly higher in the morphine group than in the tramadol group. Two dogs in the tramadol group and one in the morphine group were given morphine postoperatively because of increasing pain scores. Conclusion and clinical relevance Morphine and tramadol, administered preemptively can be used safely in dogs to control early pain after ovariohysterectomy without significant adverse effects.     

Effects of dexamethasone on emesis in cats sedated with xylazine hydrochloride

OBJECTIVE: To determine antiemetic efficacy of prophylactic administration of dexamethasone and its influence on sedation in cats sedated with xylazine hydrochloride. ANIMALS: 6 healthy adult cats (3 males and 3 females). PROCEDURE: The prophylactic antiemetic effect of 4 doses of dexamethasone (1, 2, 4, and 8 mg/kg of body weight, IM) or saline (0.9% NaCl) solution (0.066 ml/kg, IM) administered 1 hour before administration of xylazine (0.66 mg/kg, IM) was evaluated. Cats initially were given saline treatment (day 0) and were given sequentially increasing doses of xylazine on days 7, 14, 21, and 28. After xylazine injection, all cats were observed for 30 minutes to allow assessment of frequency of emesis and time until onset of the first emetic episode.The influence of dexamethasone on xylazine-induced sedation in these cats also was evaluated. RESULTS: Prior treatment with 4 or 8 mg/kg of dexamethasone significantly reduced the frequency of emetic episodes and also significantly prolonged the time until onset of the first emetic episode after xylazine injection. Time until onset of the first emetic episode also was significantly prolonged for dexamethasone at a dose of 2 mg/kg. Time until onset of sedation after administration of xylazine was not altered by administration of dexamethasone. CONCLUSIONS AND CLINICAL RELEVANCE: Dexamethasone (4 or 8 mg/kg, IM) significantly decreased the frequency of emetic episodes induced by xylazine without compromising sedative effects in cats. Dexamethasone may be used prophylactically as an antiemetic in cats treated with xylazine.     

A comparison of sedative effects of xylazine alone or combined with levomethadone or ketamine in calves prior to disbudding

ObjectiveTo compare the sedative effects of intramuscular xylazine alone or combined with levomethadone or ketamine in calves before cautery disbudding.Study designRandomized, blinded, clinical trial.AnimalsA total of 28 dairy calves, aged 21 ± 5 days and weighing 61.0 ± 9.3 kg (mean ± standard deviation).MethodsCalves were randomly allocated to three groups: xylazine (0.1 mg kg^–1) and levomethadone (0.05 mg kg^–1; group XL), xylazine (0.1 mg kg^–1) and ketamine (1 mg kg^–1; group XK) and xylazine alone (0.2 mg kg^–1; group X). Local anaesthesia (procaine hydrochloride) and meloxicam were administered subcutaneously 15 minutes after sedation and 15 minutes before disbudding. The calves’ responses to the administration of local anaesthesia and disbudding were recorded. Sedation was assessed at baseline and at intervals up to 240 minutes postsedation. Times of recumbency, first head lift and first standing were recorded. Drug plasma concentrations were measured.ResultsData were obtained from 27 animals. All protocols resulted in sedation sufficient to administer local anaesthesia and to perform disbudding. Sedation scores significantly correlated with drug plasma concentrations (p ≤ 0.002). Times to recumbency did not differ among protocols (2.8 ± 0.3, 3.1 ± 1.1 and 2.1 ± 0.8 minutes for groups XL, XK and X, respectively), whereas interval from drug(s) administration until first head lift was significantly shorter in group XK than X (47.3 ± 14.1, 34.4 ± 5.3 and 62.6 ± 31.9 minutes for groups XL, XK and X, respectively). The area under the time-sedation curve was significantly greater in group X than XK or XL (754 ± 215, 665 ± 118 and 1005 ± 258 minutes for groups XL, XK and X, respectively).Conclusions and clinical relevanceLevomethadone or ketamine with a low dose of xylazine produced short but sufficient sedation for local anaesthesia and disbudding with minimum resistance.     

Hypertension in bulls and steers anesthetized with guaifenesin-thiobarbiturate-halothane combination

Eight bulls and steers (research animals) and 18 bulls (surgical patients) were anesthetized with guaifenesin and thiopental or thiamylal and for 90 minutes with halothane. Arterial blood pressure and heart rate were recorded in all animals. Cardiac output, plasma glucose and lactate concentrations, PCV, plasma proteins and plasma thromboxane B2 values were determined before (control) and every 15 minutes during anesthesia in the research animals. Plasma catecholamine concentrations were measured in 3 of the research animals and 3 of the surgical patients. Arterial pressure, heart rate, and plasma thromboxane B2 and catecholamine concentrations were also measured immediately after the trachea was intubated. All animals, except one, were hypertensive during anesthesia. Heart rate during anesthesia was significantly increased, compared with control measurements, and cardiac output was decreased. Plasma glucose and lactate values significantly increased when the animals were restrained on their sides. Plasma glucose concentrations remained increased during anesthesia, but lactate decreased. Packed cell volume and plasma proteins were unchanged by the induction of anesthesia. Plasma norepinephrine concentration was unchanged during anesthesia, and epinephrine concentration was decreased. Endotracheal intubation caused a transient significant increase in arterial pressure, heart rate, and thromboxane B2 and a nonsignificant increase in norepinephrine.     

Comparison of 3 methods of onychectomy

The frequency of claw regrowth, bony remnants, and complications in cats that underwent forelimb onychectomy using laser, scalpel, or guillotine techniques were evaluated. Eighty-seven client-owned cats were recruited from 27 veterinary clinics in the Canadian Atlantic provinces. At least 1 year after onychectomy the cats underwent a physical examination, gait analysis, and radiographic evaluation by 1 of 2 authors. There was no significant difference in the frequency of claw regrowth among the 3 methods (P = 0.283). Significantly more cats had bony remnants following guillotine onychectomy (P < 0.001). Bony remnants were significantly associated with claw regrowth (P = 0.001). Cats that underwent laser onychectomy had significantly less post-operative complications (P = 0.023). The long-term outcome was not significantly different among the 3 methods. We conclude that leaving remnants of the third phalanx in situ is associated with an increased frequency of claw regrowth. Laser onychectomy may be preferred to reduce the risk of post-operative complications, bony remnants, and claw regrowth.