Cardiopulmonary effects of romifidine/ketamine or xylazine/ketamine when used for short duration anesthesia in the horse

The cardiovascular changes associated with anesthesia induced and maintained with romifidine/ketamine versus xylazine/ ketamine were compared using 6 horses in a cross over design. Anesthesia was induced and maintained with romifidine (100 microg/kg, IV)/ketamine (2.0 mg/kg, IV) and ketamine (0.1 mg/kg/min, IV), respectively, in horses assigned to the romifidine/ ketamine group. Horses assigned to the xylazine/ketamine group had anesthesia induced and maintained with xylazine (1.0 mg/kg, IV)/ketamine (2.0 mg/kg, IV) and a combination of xylazine (0.05 mg/kg/min, IV) and ketamine (0.1 mg/kg/min, IV), respectively. Cardiopulmonary variables were measured at intervals up to 40 min after induction. All horses showed effective sedation following intravenous romifidine or xylazine and achieved recumbency after ketamine administration. There were no significant differences between groups in heart rate, arterial oxygen partial pressures, arterial carbon dioxide partial pressures, cardiac index, stroke index, oxygen delivery, oxygen utilization, systemic vascular resistance, left ventricular work, or any of the measured systemic arterial blood pressures. Cardiac index and left ventricular work fell significantly from baseline while systemic vascular resistance increased from baseline in both groups. The oxygen utilization ratio was higher in the xylazine group at 5 and 15 min after induction. In conclusion, the combination of romifidine/ketamine results in similar cardiopulmonary alterations as a xylazine/ketamine regime, and is a suitable alternative for clinical anesthesia of the horse from a cardiopulmonary viewpoint.     

Postoperative Catecholamine Response to Onychectomy in Isoflurane-anesthetized Cats Effect of Analgesics

Twenty-four healthy adult cats were anesthetized with isoflurane in oxygen. Six cats (group 1) served as controls; onychectomy of the forefeet was performed in the other three groups. Saline was administered intravenously to group 1, and morphine, xylazine, and salicylate were administered to groups 2, 3, and 4, respectively. Mixed venous blood samples were drawn for catecholamine analysis before induction of anesthesia, after recovery from anesthesia, and 30 minutes and 60 minutes after administration of the analgesic agent. Plasma catecholamine concentrations were determined by high performance liquid chromatography. Isoflurane anesthesia alone induced a transient increase in epinephrine concentration. Norepinephrine and epinephrine concentrations increased significantly after onychectomy. Morphine and xylazine significantly decreased postoperative norepinephrine and epinephrine concentrations; salicylate did not.     

Effects of Thiopental, Ketamine, Diazepam, Xylazine, and Nitrous Oxide on EEG Spike Activity and Convulsive Bfehavior During Enflurane Anesthesia in Spontaneously Breathing Atropinized Cats Effect at Surgical Depth

The effects of thiopental, ketamine, diazepam, xylazine and nitrous oxide, and combinations of thiopental-nitrous oxide and ketamine-nitrous oxide on electroencephalographic (EEG) spike activity and convulsive behaviors in atropinized cats at surgical depth of enflurane anesthesia were assessed quantitatively for 60 minutes during spontaneous ventilation. Mean inspired enflurane concentrations (MIEC) were reduced 16% to 29% by pretreatment with thiopental, ketamine, diazepam, and xylazine, and were reduced 19% by 66% nitrous oxide. The MIEC of cats anesthetized with thiopental-nitrous oxide-enflurane and ketamine-nitrous oxide-enflurane were 35% to 38% lower than that with nitrous oxide-enflurane. Pretreatment with thiopental, ketamine, diazepam, and xylazine did not reduce the EEG spike frequency during anesthesia but did markedly reduce the spike amplitude. The addition of 66% nitrous oxide did not alter the spike frequency during anesthesia but tended to reduce the spike amplitude. Combinations of thiopental-nitrous oxide and ketamine-nitrous oxide almost abolished the spike activity. The addition of 66% nitrous oxide prevented convulsive responses elicited by photic and auditory stimulation during enflurane anesthesia. Treatment with thiopental, ketamine, diazepam and xylazine, and combinations of thiopental-nitrous oxide and ketamine-nitrous oxide, completely prevented convulsive responses during enflurane anesthesia.     

Effects of anesthetic agents on serum parathyroid hormone and calcium concentrations in mice

OBJECTIVE: To determine the effects of three anesthetic regimens on serum calcium and parathyroid hormone (PTH) in mice. STUDY DESIGN: Prospective experimental study. ANIMALS: Twenty-seven, 12-week-old, FVB mice. METHODS: Mice were anesthetized with either isoflurane, a combination of ketamine plus xylazine (100 and 10 mg kg(-1), respectively) or ketamine alone (100 mg kg(-1)). Blood was collected before and after the induction of anesthesia. Serum calcium and PTH concentrations were measured and compared. RESULTS: Isoflurane or ketamine did not significantly alter either serum calcium or serum PTH concentrations. A combination of ketamine plus xylazine significantly increased serum PTH, but not serum calcium concentrations. CONCLUSIONS: A combination of ketamine and xylazine should be avoided prior to collection of blood for measurement of serum PTH concentrations. Isoflurane is suitable for this purpose.     

A comparison of three combinations of injectable anesthetics in miniature donkeys

Objective To compare three combinations of injectable anesthetics in miniature donkeys for quality of induction, recovery, muscle relaxation, cardiopulmonary changes during anesthesia and duration of recumbency. Design Prospective, randomized experimental study. Animals Six miniature donkeys (< 90 cm in height at the withers) weighing 92–127 kg were used. Materials and methods The drug combinations were: xylazine?butorphanol?ketamine (XBK), xylazine?butorphanol?tiletamine?zolazepam (XBT) and xylazine?propofol (XP). Each miniature donkey was anesthetized with each combination at 1‐week intervals in random order. Heart and respiratory rates, indirect blood pressure and temperature were measured before and at 5‐minute intervals during recumbency. Arterial blood samples were drawn for blood‐gas analysis before and at 5, 15 and 30 minutes of anesthesia when samples could be collected. Recumbency time to sternal and time to standing were recorded and a subjective evaluation of induction, muscle relaxation and recovery were made. Results Mean recumbency time ± SD was 14.7 ± 9.4, 33.8 ± 6.3 and 14.6 ± 1.9 minutes with XBK, XBT and XP, respectively. Mean time to standing ± SD was 28.4 ± 11.3, 43.7 ± 7.2 and 26.3 ± 2.9 minutes with XBK, XBT and XP, respectively. Heart and respiratory rates and blood pressures varied from baseline but were always within normal ranges. Hemoglobin saturation, pH and PaO₂ tended to be lower with these doses of XBT and XP. Conclusions and clinical relevance Overall quality of anesthesia was poor with XBK. At the doses used this combination did not provide sufficient anesthesia compared with the combinations of XBT and XP, which appeared to provide acceptable anesthesia of short duration in miniature donkeys.     

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.     

Sedative and physiologic effects of orally administered alpha 2-adrenoceptor agonists and ketamine in cats

OBJECTIVE: To compare efficacy of 3 regimens of orally administered sedatives and determine physiologic effects of 1 of these regimens in healthy cats. DESIGN: Prospective randomized study. ANIMALS: 34 cats. PROCEDURE: Cats were assigned to 1 of 3 groups that were treated by oral administration of detomidine and ketamine, xylazine and ketamine, or medetomidine and ketamine. Cats were monitored for degree of sedation at 5-minute intervals for 60 minutes. Physiologic effects in cats treated with detomidine and ketamine were measured at 5-minute intervals for 30 minutes and compared with effects in cats treated i.m. with detomidine and ketamine or xylazine and ketamine. RESULTS: All cats treated orally with detomidine and ketamine became laterally recumbent; sedation was more variable in the other 2 groups treated orally. Vomiting and excessive salivation were the only adverse effects. Bradycardia (heart rate < 145 beats/min) was detected at each evaluation time in cats treated orally with detomidine and ketamine and in all cats treated i.m. Minimal differences among groups were detected for heart and respiratory rates, rectal temperature, and hemoglobin oxygen saturation. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of detomidine and ketamine is an effective method of sedating healthy cats and induces minimal physiologic effects that are similar to those resulting from i.m. administration of sedatives.     

Effects of xylazine/ketamine on cardiac function and serum ionised calcium in horses

Haemodynamic variables, with emphasis on right ventricular (RV) contractility, were measured in horses prior to, during and following anaesthesia with xylazine/ketamine. In an attempt to elicit mechanisms of anaesthetic-induced alteration of myocardial function, serum ionised and total calcium concentrations were also measured. Xylazine caused decreased cardiac function, including RV contractility, that was not reversed immediately by ketamine but was insignificant from pre-anaesthetic baseline by recovery (45 min following induction). Serum ionised and total calcium concentrations did not change.     

Evaluation of a combination of xylazine, ketamine, and halothane for anesthesia in llamas

Anesthesia induced by use of a combination of xylazine, ketamine, and halothane, under conditions of spontaneous and mechanically controlled ventilation, was evaluated in 5 llamas positioned in dorsal recumbency. Using chronically implanted catheters, systemic arterial blood pressure, pulmonary arterial pressure, right atrial pressure, heart rate and rhythm, cardiac output, blood pH and gas tensions, body temperature, and respiratory rate were measured before anesthesia induction (baseline), throughout the anesthetic period, and for 1 hour into the recovery period. During anesthesia, llamas undergoing spontaneous ventilation developed hypercapnia and respiratory acidosis. Cardiovascular function was decreased during both types of ventilation. The combination of xylazine, ketamine, and halothane in various doses and 2 ventilation procedures (spontaneous and controlled) provided a reliable method for general anesthesia in llamas, but marked cardiovascular depression developed during anesthesia maintenance with halothane. Spontaneous ventilation resulted in potentially clinically important respiratory acidosis.     

A comparison of romifidine and xylazine when used with diazepam/ketamine for short duration anesthesia in the horse.

The purpose of this study was to compare and evaluate sedation with intravenous xylazine (1.1 mg/kg bodyweight [BW]) versus intravenous romifidine (100 micrograms/kg BW) followed by induction of anesthesia with intravenous diazepam (0.04 mg/kg BW) and ketamine (2.2 mg/kg BW). Twelve healthy horses were used in a blinded, randomized, cross-over design. Heart rate, presence of 2nd degree atrioventricular heart blocks (2 degrees AVB), respiratory rate, arterial blood pressures, blood gases, packed cell volume, total serum proteins, and duration of anesthesia and recumbency were recorded. Induction and recovery quality was evaluated using a 0 to 4 score. Response to stimulation with noise, pressure, and cutaneous electrical stimulation was assessed at 5 minute intervals during recumbency to evaluate the depth of anesthesia. Heart rate was lower and 2 degrees AVB more frequent in the romifidine group, while blood pressure was lower in the xylazine group. Duration of anesthesia was longer in the romifidine group (mean 20.8, s mean 2.3 min) versus the xylazine group (mean 15.8, s mean 1.6 min), while induction and recovery were excellent in both groups. Respiratory rates, blood gas values, packed cell volumes, and total protein levels did not differ between groups. The results indicate that romifidine premedication followed by diazepam and ketamine is a very satisfactory regime for short duration intravenous anesthesia in horses.     

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.     

Anesthetic and physiologic effects of tiletamine, zolazepam, ketamine, and xylazine combination (TKX) in feral cats undergoing surgical sterilization

Tiletamine (12.5 mg), zolazepam (12.5 mg), ketamine (20 mg), and xylazine (5 mg) (TKX; 0.25 ml, IM) combination was evaluated as an anesthetic in 22 male and 67 female adult feral cats undergoing sterilization at high-volume sterilization clinics. Cats were not intubated and breathed room air. Oxygen saturation (SpO(2)), mean blood pressure (MBP), heart rate (HR), respiration rate (RR), and core body temperature were recorded. Yohimbine (0.25 ml, 0.5 mg, IV) was administered at the completion of surgery. TKX produced rapid onset of lateral recumbency (4+/-1 min) and surgical anesthesia of sufficient duration to complete surgical procedures in 92% of cats. SpO(2) measured via a lingual pulse oximeter probe averaged 92+/-3% in male cats and 90+/-4% in females. SpO(2) fell below 90% at least once in most cats. MBP measured by oscillometry averaged 136+/-30 mm Hg in males and 113+/-29 mm Hg in females. MBP increased at the onset of surgical stimulation suggesting incomplete anti-nociceptive properties. HR averaged 156+/-19 bpm, and RR averaged 18+/-8 bpm. Neither parameter varied between males and females or over time. Body temperature decreased significantly over time, declining to 38.0+/-0.8 degrees C at the time of reversal in males and 36.6+/-0.8 degrees C at the time of reversal in females. Time from anesthetic reversal to sternal recumbency was prolonged (72+/-42 min). Seven cats (8%) required an additional dose of TKX to maintain an adequate plane of anesthesia at the onset of surgery, and this was associated with significantly longer recovery times (108+/-24 min).     

Xylazine-Ketamine and Detomidine-Tiletamine-Zolazepam Anesthesia in Horses

Eight horses were anesthetized three times, by intravenous administration of xylazine (1.1 mg/kg) and ketamine (2.2 mg/kg), detomidine (0.02 mg/kg) and tiletamine-zolazepam (1.1 mg/kg), or detomidine (0.04 mg/kg) and tiletamine-zolazepam (1.4 mg/kg). The sequences were randomized. The duration of analgesia and the times to sternal and standing positions were recorded. Heart rate, arterial pressure, pHa, PaCO2, and PaO2 were measured before and during anesthesia. The duration of analgesia with the two doses of detomidine-tiletamine-zolazepam, 26 +/- 4 minutes and 39 +/- 11 minutes, respectively, was significantly longer than the 13 +/- 6 minutes obtained with xylazine-ketamine. Bradycardia occurred after administration of detomidine, but heart rates returned to baseline values 5 minutes after administration of tiletamine and zolazepam. Arterial pressure was significantly higher and PaO2 significantly lower during anesthesia with detomidine-tiletamine-zolazepam than with xylazine-ketamine. Some respiratory acidosis developed with all anesthetic combinations. The authors conclude that detomidine-tiletamine-zolazepam can provide comparable anesthesia of a longer duration than xylazine and ketamine, but hypoxemia will develop in some horses.     

Stereoselective pharmacokinetics of ketamine and norketamine after racemic ketamine or S-ketamine administration in Shetland ponies sedated with xylazine

The pharmacokinetics of ketamine and norketamine enantiomers after administration of intravenous (IV) racemic ketamine (R-/S-ketamine; 2.2 mg/kg) or S-ketamine (1.1 mg/kg) to five ponies sedated with IV xylazine (1.1mg/kg) were compared. The time intervals to assume sternal and standing positions were recorded. Arterial blood samples were collected before and 1, 2, 4, 6, 8 and 13 min after ketamine administration. Arterial blood gases were evaluated 5 min after ketamine injection. Plasma concentrations of ketamine and norketamine enantiomers were determined by capillary electrophoresis and were evaluated by non-linear least square regression analysis applying a monocompartmental model. The first-order elimination rate constant was significantly higher and elimination half-life and mean residence time were lower for S-ketamine after S-ketamine compared to R-/S-ketamine administration. The maximum concentration of S-norketamine was higher after S-ketamine administration. Time to standing position was significantly diminished after S-ketamine compared to R-/S-ketamine. Blood gases showed low-degree hypoxaemia and hypercarbia.     

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.     

A preliminary trial comparison of several anesthetic techniques in cats

The aim of this study was to investigate the effect of several drug combinations (atropine, xylazine, romifidine, methotrimeprazine, midazolam, or fentanyl) with ketamine for short term anesthesia in cats. Twelve cats were anesthetized 6 times by using a cross-over Latin square protocol: methotrimeprazine was combined with midazolam, ketamine, and fentanyl; midazolam and ketamine; romifidine and ketamine; and xylazine and ketamine. Atropine was combined with romifidine and ketamine, and xylazine and ketamine. Temperature, heart rate, and respiratory rate decreased in all groups. Apnea occurred in 1 cat treated with methotrimeprazine, romifidine, and ketamine, suggesting that ventilatory support may be necessary when this protocol is used. Emesis occurred in some cats treated with alpha 2-adrenoceptor agonists, and this side effect should be considered when these drugs are used.     

Anesthesia in the Richardson's ground squirrel: comparison of ketamine, ketamine and xylazine, droperidol and fentanyl, and sodium pentobarbital

A combination of ketamine and xylazine (88.9 mg of ketamine/ml and 11.1 mg of xylazine/ml) given IM (85.5 +/- 3.4 mg of ketamine/kg of body weight and 10.6 +/- 0.5 mg of xylazine/kg) or subcutaneously (85.6 +/- 4.0 mg of ketamine/kg and 10.7 +/- 0.7 mg of xylazine/kg) induced effective surgical anesthesia for 20 to 30 minutes in Richardson's ground squirrels. Use of ketamine alone (86 +/- 7 mg/kg, IM), a droperidol and fentanyl combination (2.6 +/- 0.4 mg of droperidol/kg and 52 +/- 8 micrograms of fentanyl/kg, IM), or sodium pentobarbital (50 +/- 2 mg/kg, intraperitoneally) did not induce surgical anesthesia, but did induce depressed respiratory rates in the squirrels.     

Anesthesia induced by administration of xylazine hydrochloride alone or in combination with ketamine hydrochloride and reversal by administration of yohimbine hydrochloride in captive Axis deer (Axis axis)

OBJECTIVE: To determine the anesthetic dose and cardiopulmonary effects of xylazine hydrochloride when used alone or in combination with ketamine hydrochloride and evaluate the efficacy of yohimbine hydrochloride to reverse anesthetic effects in captive Axis deer. ANIMALS: 35 adult (10 males and 25 females) Axis deer (Axis axis). PROCEDURES: All deer were anesthetized by IM administration of xylazine (3.5 mg/kg; experiment 1), a combination of ketamine and xylazine (1.25 and 1.5 mg/kg, respectively; experiment 2), or another combination of ketamine and xylazine (2.5 and 0.5 mg/kg, respectively; experiment 3). In addition, female deer were also anesthetized by IM administration of a third combination of ketamine and xylazine (1.5 and 1 mg/kg, respectively; experiment 4). Ten to 40 minutes after induction, anesthesia was reversed by IV administration of yohimbine (5, 8, or 10 mg). RESULTS: In male deer, experiment 3 yielded the most rapid induction of anesthesia. In females, experiment 4 yielded the best induction of anesthesia without adverse effects. All doses of yohimbine reversed anesthesia. Duration of anesthesia before administration of yohimbine had no effect on recovery time. CONCLUSIONS AND CLINICAL RELEVANCE: A combination of ketamine and xylazine can be used to induce anesthesia in Axis deer. Furthermore, anesthetic effects can be reversed by administration of yohimbine.     

Prolongation of anesthesia with xylazine, ketamine, and guaifenesin in horses: 64 cases (1986-1989)

On 74 occasions, 54 horses and 6 foals were anesthetized with xylazine and ketamine or xylazine, guaifenesin, and ketamine, with or without butorphanol. On 64 occasions, anesthesia was prolonged for up to 70 minutes (34 +/- 15 min) by administration of 1 to 9 supplemental IV injections of xylazine and ketamine at approximately a third the initial dosage. All horses except 5 were positioned in lateral recumbency, and oxygen was insufflated. In adult horses, the time from induction of anesthesia to the first supplemental xylazine and ketamine injection was 13 +/- 4 minutes and the time between supplemental injections was 12.1 +/- 3.7 minutes. These results were consistent with predicted plasma ketamine concentration calculated from previously published pharmacokinetic data for ketamine in horses. Respiratory and heart rates and coccygeal artery pressure remained consistent for the duration of anesthesia. The average interval between the last injection of ketamine and assumption of sternal position was approximately 30 minutes, and was the same regardless of the number of supplemental injections. The time to standing was significantly longer (P less than 0.05) in horses given 2 supplemental injections, compared with those not given any or only given 1, but was not longer in horses given 3 supplemental injections. Recovery was considered unsatisfactory in 5 horses, but did not appear to be related to prolongation of anesthesia.