Evaluation of sedative R51703 in cattle: effects on cardiorespiratory functions and rumen contraction rate.

R51703, a substance with 5-hydroxytryptamine type 2 receptor antagonist properties, was studied to assess its potential as a sedative in cattle. Six cattle in the study group were given R51703 intramuscularly at a dose rate of 0.15 mg/kg. Sedation became obvious between 10 and 15 minutes postinjection in five of these animals and lasted for approximately 120 minutes. No significant changes (P less than or equal to 0.05) were observed in respiratory rate, arterial blood gas, acid-base values or systemic arterial blood pressure. Heart rate was significantly elevated at 40, 60, 90 and 120 minutes posttreatment, but dysrhythmias were not detected. Rumen motility, as judged by the contraction rate, was decreased but not to significant levels. All animals ate normally at the end of the study period. The results indicated that R51703 may have a role in the management of domestic cattle and that further work is indicated to assess its potential in this area.

Comparative hemodynamic effects of halothane and halothane-acepromazine at equipotent doses in dogs.

The purpose of this study was to compare the cardiovascular effects of halothane when used alone at increasing doses (1.2, 1.45 and 1.7 minimum alveolar concentration, MAC) to those produced with equipotent doses of halothane after potentiation of the anesthetic effect with acepromazine (ACP) sedation (45% reduction of halothane MAC). Six healthy mature dogs were used on three occasions. The treatments were halothane and intramuscular (IM) saline (1.0 mL), halothane and ACP (0.04 mg/kg IM), or halothane and ACP (0.2 mg/kg IM). Anesthesia was induced and maintained with halothane in oxygen and the dogs were prepared for the collection of arterial and mixed venous blood and for the determination of heart rate, systolic, diastolic and mean arterial pressure, mean pulmonary arterial pressure (PAP), central venous pressure and cardiac output. Following animal preparation the saline or ACP was administered and positive pressure ventilation instituted. Twenty-five minutes later the dogs were exposed to the first of three anesthetic levels, with random assignment of the sequence of administration. At each anesthetic level, measurements were obtained at 20 and 35 min. Calculated values included cardiac index, stroke index, left ventricular work, systemic vascular resistance, arterial oxygen content, mixed venous oxygen content, oxygen delivery and oxygen consumption. Heart rate was significantly higher with halothane alone than with both halothane-ACP combinations and was significantly higher with high dose ACP compared to low dose ACP. Systolic and mean blood pressures were lowest with halothane alone and highest with 0.2 mg/kg ACP, the differences being significant for each treatment. Oxygen uptake and PAP were significantly lower in dogs treated with ACP. It was concluded that ACP does not potentiate the cardiovascular depression that accompanies halothane anesthesia when the resultant lower dose requirements of halothane are taken into consideration.

Antagonism of xylazine induced sedation by idazoxan in calves.

Idazoxan was studied at three dose rates to assess its potential as an antagonist to xylazine. Calves in the study group were initially given xylazine at a dose rate of 0.2 mg/kg intravenously followed 12 minutes later by idazoxan at a dose rate of either 0.05, 0.075 or 0.10 mg/kg intravenously. A control group received a saline injection instead of idazoxan. All three dose levels of idazoxan successfully reversed the xylazine induced central nervous depression and all animals stood within two minutes of injection. No residual signs of sedation were noticed and relapse did not occur. In addition idazoxan was successful in reversing respiratory and cardiovascular depression produced by xylazine. The results indicated that idazoxan may be used for rapid reversal of xylazine induced sedation in calves.

Cardiopulmonary effects of a ketamine/acepromazine combination in hypovolemic cats.

The cardiopulmonary effects of a ketamine/ acepromazine combination was studied in ten cats subjected to a 25% whole blood volume loss. Test parameters included cardiac output, measured via thermodilution, heart rate, respiratory rate, arterial blood pressure (systolic, diastolic and mean) and blood gas analysis. Values for cardiac index, stroke volume and systemic vascular resistance were calculated from these data. Posthemorrhage, cardiac output, cardiac index, stroke volume, heart rate and measurements of arterial blood pressure were significantly decreased (p less than 0.05). Following the induction of ketamine/ acepromazine anesthesia, cardiac output, cardiac index, stroke volume and heart rate showed mild but statistically insignificant declines and were above their respective posthemorrhage values 120 min into ketamine/ acepromazine anesthesia. Measurements of arterial blood pressure showed further declines from their respective posthemorrhage values that were statistically significant (p less than 0.05). Following hemorrhage, respiratory rate increased significantly (p less than 0.05), associated with a fall in arterial CO2 tension. During ketamine/ acepromazine anesthesia, respiratory rate showed a dramatic and significant decline (p less than 0.05) with arterial CO2 tension rising to prehemorrhage values. Systemic vascular resistance, arterial O2 tension and pH remained essentially unchanged throughout the experimental period.

Cardiopulmonary effects of a halothane/oxygen combination in hypovolemic cats.

The cardiopulmonary effects of a halothane/oxygen combination were studied in eight cats subjected to a 25% whole blood volume loss. Test parameters included cardiac output measured via thermodilution, heart rate, respiratory rate, arterial blood pressure (systolic, diastolic and mean) and blood gas analysis. Values for cardiac index, stroke volume and systemic vascular resistance were calculated from these data. Posthemorrhage cardiac output, cardiac index, stroke volume and measurements of arterial blood pressure were significantly decreased (p less than 0.05). Heart rate remained unchanged. Following induction of halothane anesthesia the above parameters experienced a further significant decline (p less than 0.05) from their immediate preanesthetic (i.e. posthemorrhage) values. Heart rate also significantly decreased (p less than 0.05). Thirty minutes following the cessation of halothane anesthesia these values returned to near-hemorrhage levels, being above their respective preanesthetic values. Systemic vascular resistance initially rose, peaking ten minutes into halothane anesthesia, before gradually falling to prehemorrhage values at the end of halothane anesthesia. Following hemorrhage, respiratory rate demonstrated a transient increase, associated with an arterial CO2 tension fall, before returning to initial values at the preanesthetic time. During halothane anesthesia respiratory rate remained unchanged whereas arterial CO2 tension rose significantly (p less than 0.05) and pH declined slightly from preanesthetic readings. These returned to prehemorrhage values 30 minutes following the cessation of halothane anesthesia.

Determination of a sedative dose and influence of midazolam on cardiopulmonary function in Canada geese.

Midazolam HCl (1.0 or 2.0 mg/kg of body weight) was administered IM to 6 Canada geese to determine a sedative dose that would allow positioning for radiologic examination. The effects of both test doses on cardiopulmonary function were evaluated at 5, 10, 15, 20, 30, and 40 minutes after drug administration and were compared with 2 end-tidal isoflurane concentrations (1.5 and 2.5%). The 2.0 mg/kg dosage induced moderate sedation at 15 and 20 minutes; sedation was adequate for positioning the geese. Sedation induced by the 1.0 mg/kg dosage was inadequate. The effects of both test doses on blood pressure, heart rate, and temperature were not significantly different from each other and from baseline data. Respiratory rate increased significantly (P less than 0.05) at 10, 15, 20, and 30 minutes with the 2.0 mg/kg dosage, and at 15 and 20 minutes with the 1.0 mg/kg dosage. Blood pressure and respiratory rate were significantly (P less than 0.05) decreased with isoflurane when compared with baseline data and the midazolam test doses. The results of this study indicate that midazolam at a dosage of 2.0 mg/kg induces adequate sedation with minimal cardiopulmonary changes, and, as an alternative to general anesthesia with isoflurane, provides a satisfactory level of restraint for radiography.

Comparison of the hemodynamic effects of halothane alone and halothane combined with epidurally administered morphine for anesthesia in ventilated dogs.

The hemodynamic effects of 1.5 minimal alveolar concentration of halothane alone (1.6% end-tidal) and 1.5 minimal alveolar concentration of halothane (1.1% end-tidal concentration) combined with epidurally administered morphine were compared during controlled ventilation in 10 dogs used on 2 occasions and randomly allocated to 2 groups. Arterial blood pressure, cardiac index, stroke volume, left ventricular work, and pulmonary arterial pressure were significantly (P less than 0.05) higher in dogs of the morphine-treated group before administration of morphine. After epidural administration of morphine (0.1 mg/kg of body weight diluted in 0.26 ml of saline solution/kg), hemodynamic changes were not observed, and the aforementioned variables remained significantly (P less than 0.05) higher than values in dogs of the halothane only group. Compared with halothane (1.6%) alone, the reduction in halothane end-tidal concentration (1.1%) associated with epidurally administered morphine is beneficial in maintaining hemodynamic function.

Nephrotoxicity in dogs associated with methoxyflurane anesthesia and flunixin meglumine analgesia.

Uremia unexpectedly developed in five dogs 24 hours after undergoing thoracotomy in a student laboratory. In all dogs general anesthesia had been maintained with methoxyflurane, muscle relaxation had been induced with gallamine, and each dog received a single intravenous dose of 1.0 mg/kg flunixin meglumine for analgesia upon termination of anesthesia. In a subsequent group of dogs undergoing an orthopedic procedure, we assessed the effects on renal function of methoxyflurane anesthesia plus oxymorphone, or of methoxyflurane or halothane anesthesia in combination with a single IM 1.0 mg/kg dose of flunixin meglumine. Significant elevations in serum urea and creatinine values, and necrosis of collecting ducts and loops of Henle, were noted only in the dogs receiving methoxyflurane and flunixin meglumine.We conclude that the use of combination of methoxyflurane and flunixin meglumine is contraindicated in dogs.

A comparison of ketorolac with flunixin, butorphanol, and oxymorphone in controlling postoperative pain in dogs.

Ketorolac tromethamine, a nonsteroidal anti-inflammatory analgesic, was compared with flunixin and butorphanol for its analgesic efficacy and potential side effects after laparotomy or shoulder arthrotomy in dogs. Sixty-four dogs were randomly assigned to receive butorphanol 0.4 mg/kg body weight (BW) (n = 21), flunixin 1.0 mg/kg BW (n = 21), or ketorolac 0.5 mg/kg BW (n = 22), in a double blind fashion. The analgesic efficacy was rated from 1 to 4 (1 = inadequate, 4 = excellent) for each dog. The average scores after laparotomy were ketorolac, 3.4; flunixin, 2.7; and butorphanol, 1.6. After shoulder arthrotomy, the average scores were ketorolac, 3.5; flunixin, 3.0; and butorphanol, 1.4 (5/11 dogs). As butorphanol was unable to control pain after shoulder arthrotomy, oxymorphone, 0.05 mg/kg BW, replaced butorphanol in a subsequent group of dogs and had a score of 2.0 (6/11 dogs). Serum alanine aminotransferase and creatinine were significantly elevated above baseline at 24 hours postoperatively in dogs receiving flunixin. One dog in each group developed melena or hematochezia. One dog receiving ketorolac had histological evidence of gastric ulceration. We concluded that ketorolac is a good analgesic for postoperative pain in dogs.

Intraosseous cannulation and drug administration for induction of anesthesia in chickens.

Twenty-four chickens were randomly assigned to one of three treatments (ketamine, 30 mg/kg; thiopental, 20 mg/kg; saline, 0.8 mL). Baseline data (heart rate, respiratory rate, systolic blood pressure, and cloacal temperature) were recorded before ulnar intraosseous cannulation and administration of drug treatment and for 30 minutes after administration. One investigator, unaware of the treatment administered, assessed the reaction to cannulation, number of attempts per cannulation, reaction to injection, time to induction and recovery, and quality of induction and recovery. Respiratory rate increased significantly (p < .05) from baseline after thiopental. Other parameters did not vary within groups or between groups. Most birds did not react or had a mild reaction to cannulation and injection, and on average fewer than two attempts were necessary. Quality of recovery was significantly (p < .05) better after thiopental. Time to recovery was significantly (p < .05) shorter after thiopental. No major histopathologic changes were noted in bone marrow samples from the injection site. This study demonstrates that the intraosseous route may be used to induce anesthesia in chickens, and that minimal changes in the variables studied were produced by ketamine and thiopental.

Evaluation of pentobarbital as a drug for standing sedation in cattle.

Pentobarbital (1.0, 1.5, and 2.0 mg/kg intravenously [IV]) was administered to four adult cows to determine a dose suitable for producing standing sedation in adult cattle, and to evaluate its effects on cardiopulmonary function and rumen motility. The response was assessed after 15, 30, 60, and 90 minutes. The 1.0 and 1.5 mg/kg doses induced mild sedation at 15 and 30 minutes, and no sedation at 60 and 90 minutes. The 2.0 mg/kg dose produced moderate sedation at 15 and 30 minutes, and mild sedation at 60 minutes. The 2.0 mg/kg dose was judged to be the most suitable. The effects of pentobarbital (2.0 mg/kg IV) on heart rate, blood pressure, respiratory rate, blood gases, and rumen motility were measured in five cows during a 90 minute period. Respiratory rate was significantly depressed at 15, 30, and 60 minutes, but there were no significant changes in the other variables. Pentobarbital (2.0 mg/kg IV) is reliable in adult cattle for standing sedation of short duration.

The effect of occlusive and semi-occlusive dressings on the healing of acute full-thickness skin wounds on the forelimbs of dogs.

This project compared the effects of hydrocolloid (HC) and hydrogel (HG) occlusive dressings and a polyethylene (PE) semi-occlusive dressing on the healing of acute full-thickness skin wounds on the forelimbs of 10 dogs. All treatments resulted in a similar degree of healing at postoperative days 4 and 7. No significant differences existed in the number of wounds that were more than 90% healed at postoperative day 28 between the group treated with the HG dressing and the group treated with the PE dressing. There were significantly fewer wounds more than 90% healed at postoperative day 28 in the group treated with the HC dressing. Wounds under the HG dressing had the largest mean percentage of contraction at postoperative days 21 and 28. Wounds under the HG dressing also had the largest contraction/re-epithelialization ratio (postoperative days 21 and 28) compared with wounds under the PE and HC dressings. Wounds under the PE dressing had a significantly higher mean percentage of re-epithelialization than wounds under both occlusive dressings on postoperative days 14, 21, and 28. Wounds under the two occlusive dressings had exuberant granulation tissue present more often than wounds under the PE dressing. The two occlusive dressings had significantly higher bacterial counts on wounds compared with wounds under the PE dressing; analysis of variance (ANOVA), P = .0008. Wounds under the HC dressing showed the poorest healing in all parameters.