Cardiovascular changes associated with anaesthesia induced by medetomidine combined with ketamine in cats

Effects of intramuscular alfaxalone and dexmedetomidine alone and combined on ocular, electroretinographic, and cardiorespiratory parameters in normal cats

Background

This study aimed to determine the effects of intramuscular (IM) administration of alfaxalone with or without dexmedetomidine on short electroretinography (ERG), ocular parameters and cardiorespiratory in healthy cats.

Methods

Eight healthy female spayed cats were treated with three sedation protocols: IM administration of 5 μg/kg dexmedetomidine (DEX), 5 mg/kg alfaxalone (ALF), and 5 μg/kg dexmedetomidine plus 5 mg/kg alfaxalone (DEX + ALF). The washout period after each treatment was 2 weeks. Physiological parameters, time metrics, intraocular pressure (IOP), Schirmer tear test 1 (STT-1) and a short ERG protocol were recorded. For age data, weight data, time metrics and ERG data, one-way ANOVA with Bonferroni posterior comparisons were performed. For physiological parameters, IOP and STT-1 data, two-way repeated measures ANOVA with Bonferroni posterior comparisons were performed. Statistical significance was set at a p-value <0.05.

Results

IOPs were increased in all three groups compared to baseline and showed no significant differences among three groups at any time point. STT-1 values were decreased significantly during the process. Significant differences were noticed between a-wave amplitude in the dark-adapted response between DEX and ALF, and a-wave amplitude in light-adapted response between ALF and DEX + ALF.

Conclusion

This study demonstrates the feasibility of three sedation protocols for short ERG recording in cats. All these treatments resulted in increased IOP values and reduced STT-1 values. But baseline data of ERG was not obtained as a blank control in cats.

The Effect of a Subsequent Dose of Dexmedetomidine or Other Sedatives following an Initial Dose of Dexmedetomidine on Sedation and Quality of Recovery in Cats: Part I

Dexmedetomidine is an a2-agonist commonly used in veterinary practice. Occasionally, the administered dose of dexmedetomidine may result in insufficient sedation, and an additional dose or drug may be required. The sedative effects of seven different drugs administered at subsequent time points after an initial, insufficient dose of dexmedetomidine were evaluated. Seven adult cats participated in this crossover, blind, randomised study. The groups consisted of two consecutive doses of dexmedetomidine (15 + 10 μg/kg) (DD) or a dose of dexmedetomidine (15 μg/kg) followed by either NS 0.9% (DC-control group), tramadol 2 mg/kg (DT), butorphanol 0.2 mg/kg (DBT), buprenorphine 20 μg/kg (DBP), ketamine 2 mg/kg (DK), or midazolam 0.1 mg/kg (DM). Sedation was evaluated using the Grint sedation scale. In all groups, atipamezole was administered at the end of the evaluation, and recovery was assessed using the Lozano and Sams recovery scales. The DC and DM groups exhibited minimal sedative effects. The maximum sedative effect was observed in the DD and DK groups, while sedation in the DD and DK groups was significantly higher compared to the DC group. Recovery in all groups was uneventful, except in the DM group, where it was prolonged and difficult, although no statistically significant difference was detected. Therefore, insufficient sedation with dexmedetomidine can be enhanced by a subsequent dose of dexmedetomidine, ketamine, or butorphanol, whereas the addition of midazolam reduces sedation and prolongs recovery.

Comparison of the cardiovascular effects of immobilization with three different drug combinations in free-ranging African lions

Thirty-six free-ranging lions (12 per group) were immobilized with tiletamine-zolazepam (Zoletil 0.6 mg/kg i.m.) plus medetomidine (0.036 mg/kg i.m.) (TZM), ketamine (3.0 mg/kg i.m.) plus medetomidine (0.036 mg/kg i.m.) (KM) or ketamine (1.2 mg/kg i.m.) plus butorphanol (0.24 mg/kg i.m.) plus medetomidine (0.036 mg/kg i.m.) (KBM). During immobilization cardiovascular variables were monitored at 5-minute intervals for a period of 30 minutes. Lions immobilized with all three drug combinations were severely hypertensive. Systolic arterial pressure was higher at initial sampling in lions immobilized with KM (237.3 ± 24.8 mmHg) than in those immobilized with TZM (221.0 ± 18.1 mmHg) or KBM (226.0 ± 20.6 mmHg) and decreased to 205.8 ± 19.4, 197.7 ± 23.7 and 196.3 ± 17.7 mmHg, respectively. Heart rates were within normal ranges for healthy, awake lions and decreased throughout the immobilization regardless of drug combination used. Lions immobilized with TZM had a higher occurrence (66%) of skipped heart beats than those immobilized with KBM (25%). The three drug combinations all caused negative cardiovascular effects, which were less when KBM was used, but adverse enough to warrant further investigations to determine if these effects can be reversed or prevented when these three combinations are used to immobilize free-living lions.

Comparison of anesthetic effects of tiletamine-zolazepam-medetomidine or ketamine-medetomidine in captive Amur leopard cats (Prionailurus bengalensis euptailurus)

OBJECTIVE

To evaluate the effects and utility of tiletamine-zolazepam-medetomidine (TZM) and ketamine-medetomidine (KM) for anesthesia of Amur leopard cats (Prionailurus bengalensis euptailurus).

STUDY DESIGN

Prospective, randomized experimental trial.

ANIMALS

A total of six female (3.70 ± 0.49 kg) and six male (5.03 ± 0.44 kg; mean ± standard deviation) Amur leopard cats aged 2-6 years.

METHODS

Each animal was administered four protocols separated by ≥3 weeks. Each protocol included medetomidine (0.05 mg kg^-1) combined with tiletamine-zolazepam (1 mg kg^-1; protocol MTZ_LO); tiletamine-zolazepam (2 mg kg^-1; protocol MTZ_HI); ketamine (2 mg kg^-1; protocol MK_LO); or ketamine (4 mg kg^-1; MK_HI) administered intramuscularly. At time 0 (onset of lateral recumbency) and 30 minutes, heart rate (HR), respiratory rate (f_R), rectal temperature, noninvasive mean arterial pressure (MAP) and hemoglobin oxygen saturation (SpO₂) were recorded. Times to onset of lateral recumbency, duration of anesthesia and time to standing were recorded.

RESULTS

Overall, animals were anesthetized with all protocols within 10 minutes, anesthesia was maintained ≥57 minutes, and recovery (time from the first head lift to standing) was completed within 5 minutes. During anesthesia with all protocols, HR, f_R, rectal temperature, SpO₂ and MAP were 99-125 beats minute^-1, 33-44 breaths minute^-1, 37.6-39.4 °C, 90-95% and 152-177 mmHg, respectively. No adverse event was observed.

CONCLUSIONS AND CLINICAL RELEVANCE

TZM and KM at various dosages resulted in rapid onset of anesthesia, duration of >57 minutes and rapid recovery without administration of an antagonist. Accordingly, all these combinations are useful for anesthetizing Amur leopard cats and for performing simple procedures. However, the low doses of the anesthetic agents are recommended because there was no difference in duration of anesthesia between the dose rates studied.

Assessment of hydromorphone and dexmedetomidine for emesis induction in cats

OBJECTIVE

To compare the efficacy of hydromorphone and dexmedetomidine at inducing emesis in cats.

DESIGN

Prospective, blinded, randomized crossover study.

SETTING

Veterinary university teaching hospital.

ANIMALS

12 healthy purpose-bred cats.

INTERVENTIONS

Cats were randomly assigned to receive hydromorphone (0.1 mg/kg, subcutaneously) or dexmedetomidine (7 μg/kg, IM). Following administration, the incidences of emesis, number of emetic events, signs of nausea (hypersalivation, lip licking), temperature, heart rate, respiratory rate, and sedation score were recorded for 6 hours.

MEASUREMENTS AND MAIN RESULTS

Emesis was successful in 9 of 12 (75%) cats when treated with hydromorphone and in 7 of 12 (58%) cats when treated with dexmedetomidine (P = 0.67). Dexmedetomidine was more likely to cause sedation than hydromorphone (P < 0.001). Heart rate in cats was significantly decreased at 1 and 2 hours post-hydromorphone (P = 0.003, 0.014, respectively) and at 1, 2, 3, 5, 6 hours post-dexmedetomidine (P = 0.001, 0.003, 0.038, 0.013, 0.001, respectively). Cats were more likely to develop an increase in body temperature with hydromorphone administration although this was not clinically significant.

CONCLUSIONS

Results of the present study indicate that hydromorphone is an effective alternative to dexmedetomidine for the induction of emesis in cats. Hydromorphone appears to cause less sedation and less decrease in heart rate. Further investigation into the most adequate dose of hydromorphone for optimizing emesis is warranted.

Effects of sedation with dexmedetomidine and buprenorphine on echocardiographic variables, blood pressure and heart rate in healthy cats

Objectives Sedative agents are occasionally used to enable echocardiographic examination when screening cats for heart disease, such as hypertrophic cardiomyopathy (HCM). Owing to their haemodynamic effects, sedative agents may alter echocardiographic measurements. The aim of the study was to evaluate the effects of the sedative combination dexmedetomidine and buprenorphine on echocardiographic variables, blood pressure (BP) and heart rate (HR) in healthy cats. Methods Fifty healthy, client-owned cats were prospectively recruited and included after physical examination. Cats were sedated intramuscularly with dexmedetomidine and buprenorphine, according to body weight. Blood pressure and HR measurements, echocardiographic and Doppler examinations were performed prior to sedation and repeated once cats had achieved acceptable sedation. Results Left ventricular internal diameter at end-diastole and systole, right ventricular internal diameter at end-diastole, left atrium (LA), pulmonary artery (PA) deceleration time, and systolic, diastolic and mean arterial blood pressure increased after sedation ( P ⩽0.022). Aortic and PA maximum velocity, fractional shortening, PA acceleration/deceleration time and HR decreased after sedation ( P <0.0001). Interventricular septum at end-diastole and systole, left ventricular posterior wall at end-diastole and systole, aortic diameter (Ao), left atrial/aortic diameter (LA/Ao) and pulmonic acceleration time did not change. Conclusions and relevance Blood pressure increased and HR decreased post-sedation. While wall thickness and LA/Ao were not affected by sedation, indices of LA and left ventricular size increased. Further studies are needed using cats with HCM to assess the effect of this sedative combination on HCM screening results.

Role of fetal nutrient restriction and postnatal catch-up growth on structural and mechanical alterations of rat aorta

KEY POINTS

Intrauterine growth restriction (IUGR), induced by maternal undernutrition, leads to impaired aortic development. This is followed by hypertrophic remodelling associated with accelerated growth during lactation. Fetal nutrient restriction is associated with increased aortic compliance at birth and at weaning, but not in adult animals. This mechanical alteration may be related to a decreased perinatal collagen deposition. Aortic elastin scaffolds purified from young male and female IUGR animals also exhibit increased compliance, only maintained in adult IUGR females. These mechanical alterations may be related to differences in elastin deposition and remodelling. Fetal undernutrition induces similar aortic structural and mechanical alterations in young male and female rats. Our data argue against an early mechanical cause for the sex differences in hypertension development induced by maternal undernutrition. However, the larger compliance of elastin in adult IUGR females may contribute to the maintenance of a normal blood pressure level.

ABSTRACT

Fetal undernutrition programmes hypertension development, males being more susceptible. Deficient fetal elastogenesis and vascular growth is a possible mechanism. We investigated the role of aortic mechanical alterations in a rat model of hypertension programming, evaluating changes at birth, weaning and adulthood. Dams were fed ad libitum (Control) or 50% of control intake during the second half of gestation (maternal undernutrition, MUN). Offspring aged 3 days, 21 days and 6 months were studied. Blood pressure was evaluated in vivo. In the thoracic aorta we assessed gross structure, mechanical properties (intact and purified elastin), collagen and elastin content and internal elastic lamina (IEL) organization. Only adult MUN males developed hypertension (systolic blood pressure: MUN_males  = 176.6 ± 5.6 mmHg; Control_males  = 136.1 ± 4.9 mmHg). At birth MUN rats were lighter, with smaller aortic cross-sectional area (MUN_males  = (1.51 ± 0.08) × 10⁵  μm² , Control_males  = (2.8 ± 0.04) × 10⁵  μm² ); during lactation MUN males and females exhibited catch-up growth and aortic hypertrophy (MUN_males  = (14.5 ± 0.5) × 10⁵  μm² , Control_males  = (10.4 ± 0.9) × 10⁵  μm² ), maintained until adulthood. MUN aortas were more compliant until weaning (functional stiffness: MUN_males  = 1.0 ± 0.04; Control_males  = 1.3 ± 0.03), containing less collagen with larger IEL fenestrae, returning to normal in adulthood. Purified elastin from young MUN offspring was more compliant in both sexes; only MUN adult females maintained larger elastin compliance (slope: MUN_females  = 24.1 ± 1.9; Control_females  = 33.3 ± 2.8). Fetal undernutrition induces deficient aortic development followed by hypertrophic remodelling and larger aortic compliance in the perinatal period, with similar alterations in collagen and elastin in both sexes. The observed alterations argue against an initial mechanical cause for sex differences in hypertension development. However, the maintenance of high elastin compliance in adult females might protect them against blood pressure rise.

Anaesthetic and cardiorespiratory effects of ketamine plus dexmedetomidine for chemical restraint in black capuchin monkeys (Sapajus nigritus)

AIMS

To evaluate the quality of anaesthesia and cardiorespiratory effects of ketamine and two doses of dexmedetomidine in captive black capuchin monkeys (Sapajus nigritus) undergoing routine clinical examination.

METHODS

Twenty-four animals undergoing routine clinical examination were enrolled in the study. Animals were briefly physically restrained and examined to ensure no obvious illness was present and that they were healthy. Monkeys were randomly allocated to two groups (n=12 per group) and then treated with a combination of I/M 7.5 mg/kg ketamine and either 30 µg/kg or 50 µg/kg dexmedetomidine (Dex30 or Dex50 groups, respectively). Interval to onset and duration of anaesthesia were recorded, and the quality of induction of anaesthesia and recovery were subjectively evaluated. Heart rate, respiratory rate, systolic arterial pressure (SAP), rectal temperature, degree of sedation, analgesia, muscle relaxation and response to auditory stimulus were measured every 5 minutes from onset of anaesthesia until recovery.

RESULTS

The mean interval to onset of anaesthesia was 7.3 (SD 6.6) and 9.1 (SD 5.0) minutes for the Dex30 and Dex50 groups, respectively (p=0.208). Mean duration of anaesthesia was longer for monkeys in the Dex50 (85.5 (SD 15.3) minutes) compared to those in Dex30 (63.9 (SD 16.4) minutes) group (p=0.003). Induction was considered excellent in 23/24 animals, and recovery was excellent in all animals. Heart rate, respiratory rate and body temperature decreased in both groups when compared to baseline, with no differences between groups. No differences between groups were found for assessments of sedation, analgesia, muscle relaxation or response to auditory stimulus.

CONCLUSION AND CLINICAL RELEVANCE

Administration of ketamine and dexmedetomidine at the two doses produced adequate, dose-dependent chemical restraint, with excellent induction and recovery, and minimal clinically significant cardiorespiratory effects in captive capuchin monkeys. Due to the occurrence of arrhythmias, electrocardiographic monitoring is recommended when this combination is used. The administration of higher doses of dexmedetomidine produced longer lasting anaesthesia without further compromise of cardiorespiratory parameters.

Comparison of intramuscular alfaxalone and ketamine combined with dexmedetomidine and butorphanol for castration in cats

Objectives Cardiorespiratory parameters and anaesthesia quality in cats anaesthetised with either intramuscular (IM) alfaxalone or ketamine both combined with dexmedetomidine and butorphanol for castration were evaluated. Methods Thirty-two client-owned cats were randomly assigned to receive either alfaxalone (A; 3 mg/kg IM) or ketamine (K; 5 mg/kg IM), combined with dexmedetomidine (10 μg/kg) and butorphanol (0.2 mg/kg). Heart rate (HR), respiratory rate (RR) and rectal temperature (T°) were recorded prior to drug administration. Pulse rate (PR) and RR were recorded 10 (T10) and 15 (T15) mins after injection (T0). Cardiorespiratory values (PR, RR, SPO2, blood pressure, PE'CO2) were recorded every 5 mins for the duration of the procedure. Pain at injection, intubation and recovery were evaluated with simple descriptive scores. Feasibility of anaesthesia was evaluated by the number of top-ups of anaesthetic needed. Cat attitude, ability to walk and presence of ataxia were assessed several times after extubation (Texmin) and the time between injection and extubation recorded. Pain was assessed at Tex120 and Tex240 with the 4Avet-pain score. Results The RR was significantly lower in group K at T10 (RRK = 28 ±13.35 breaths per minute [brpm], RRA= 43.24 ±7.04 brpm) and T15 (RRK = 28 ±11.53 brpm vs RRA = 43 ±12.18 brpm). Time to extubation was significantly longer in group A (TA = 62 ±14.6 mins, TK = 45.13 ± 7.38 mins). Cats in group K needed more top-ups, were more ataxic at Tex120, had a worse recovery score at Tex60 and were less willing to walk at Tex30. Conclusions and relevance Cats receiving alfaxalone had a longer but better quality recovery. Cardiorespiratory parameters were stable and within clinically acceptable values following IM injection of either alfaxalone or ketamine in healthy cats. Intramuscular alfaxalone is a suitable alternative to ketamine for short procedures requiring anaesthesia when used in combination with dexmedetomidine and butorphanol.

Adverse reactions of α2-adrenoceptor agonists in cats reported in 2003-2013 in Finland

OBJECTIVE

To describe suspected adverse drug reactions in cats associated with use of α₂-adrenoceptor agonists.

STUDY DESIGN

Retrospective study.

ANIMALS

A total of 90 cats.

METHODS

Data were collected from reports on adverse reactions to veterinary medicines sent to the Finnish Medicines Agency during 2003-2013. All reports of suspected adverse reactions associated with use of α₂-adrenoceptor agonists in cats were included. Probable pulmonary oedema was diagnosed based on post mortem or radiological examination, or presence of frothy or excess fluid from the nostrils or trachea. If only dyspnoea and crackles on auscultation were reported, possible pulmonary oedema was presumed.

RESULTS

Pulmonary oedema was suspected in 61 cases. Of these cats, 37 were categorised as probable and 24 as possible pulmonary oedema. The first clinical signs had been noted between 1 minute and 2 days (median, 15 minutes) after α₂-adrenoceptor agonist administration. Many cats probably had no intravenous overhydration when the first clinical signs were detected, as either they presumably had no intravenous cannula or the signs appeared before, during or immediately after cannulation. Of the 61 cats, 43 survived, 14 died and for four the outcome was not clearly stated.

CONCLUSIONS AND CLINICAL RELEVANCE

Pulmonary oedema is a perilous condition that may appear within minutes of an intramuscular administration of sedative or anaesthetic agent in cats. The symptoms were not caused by intravenous overhydration, at least in cats having no venous cannula when the first clinical signs were detected.

The Association of Shelter Veterinarians' 2016 Veterinary Medical Care Guidelines for Spay-Neuter Programs

As community efforts to reduce the overpopulation and euthanasia of unwanted and unowned cats and dogs have increased, many veterinarians have increasingly focused their clinical efforts on the provision of spay-neuter services. Because of the wide range of geographic and demographic needs, a wide variety of spay-neuter programs have been developed to increase delivery of services to targeted populations of animals, including stationary and mobile clinics, MASH-style operations, shelter services, community cat programs, and services provided through private practitioners. In an effort to promote consistent, high-quality care across the broad range of these programs, the Association of Shelter Veterinarians convened a task force of veterinarians to develop veterinary medical care guidelines for spay-neuter programs. These guidelines consist of recommendations for general patient care and clinical procedures, preoperative care, anesthetic management, surgical procedures, postoperative care, and operations management. They were based on current principles of anesthesiology, critical care medicine, infection control, and surgical practice, as determined from published evidence and expert opinion. They represent acceptable practices that are attainable in spay-neuter programs regardless of location, facility, or type of program. The Association of Shelter Veterinarians envisions that these guidelines will be used by the profession to maintain consistent veterinary medical care in all settings where spay-neuter services are provided and to promote these services as a means of reducing sheltering and euthanasia of cats and dogs.

COMPARISON BETWEEN DEXMEDETOMIDINE-S-KETAMINE AND MIDAZOLAM-S-KETAMINE IN IMMOBILIZATION OF ONCILLA (LEOPARDUS TIGRINUS)

Established immobilization protocols are required for safe procedures on wildlife and zoo animals. This study evaluated the cardiovascular, respiratory, and anesthetic effects of dexmedetomidine (40 μg/kg) with S-ketamine (5 mg/kg) and midazolam (0.5 mg/kg) with S-ketamine (5 mg/kg) in 12 specimens of oncilla (Leopardus tigrinus) at Quinzinho de Barros Municipal Zoo Park in Sorocaba, São Paulo, Brazil, between January and March 2010. Each animal underwent both protocols, totaling 24 anesthetic procedures. The dexmedetomidine-S-ketamine group (DK) showed a decrease in heart rate compared to initial values and significantly lower heart rate and oxyhemoglobin saturation values compared to Midazolam-S-Ketamine Group (MK). Four animals in DK had episodes of sinus pauses. Systemic blood pressure, respiratory frequency, and rectal temperature showed no significant differences between groups. The dexmedetomidine-S-ketamine group showed a greater degree of muscle relaxation and allowed for more thorough and longer oral evaluations. The dexmedetomidine-S-ketamine group had a shorter period of recumbency, longer period to return of muscle tone, and shorter recovery time. Two animals in MK did not reach recumbency. The dexmedetomidine-S-ketamine group had better qualities of induction and recovery. It may be concluded that both protocols can be safely used in oncillas. Midazolam-S-ketamine promotes effective chemical restraint for quick and minimally invasive procedures and dexmedetomidine-S-ketamine promotes effective chemical restraint for prolonged and more invasive procedures.

Evaluation of medetomidine, ketamine and buprenorphine for neutering feral cats

A combination of medetomidine (M, 100 μg/kg), ketamine (K, 10 mg/kg) and buprenorphine (B, 10 μg/kg), administered by intramuscular injection, was evaluated for spaying and castration (neutering) of feral cats (n = 101). Eleven animals (11%) required supplemental anesthesia (isoflurane by mask) to maintain an adequate plane of surgical anesthesia. Atipamezole (A, 125 μg/kg) was administered subcutaneously at the completion of surgery. All cats recovered from surgery and were released the following day. A hemoglobin saturation (SpO(2)) value of < 95% was recorded at least once during anesthesia in all cats. This MKB combination can be used in a feral cat sterilization clinic, but isoflurane supplementation may be necessary. Further research is indicated to determine the clinical significance of the low SpO(2) values associated with this anesthetic regimen.

Reversible immobilization of giant otters (Pteronura brasiliensis) using medetomidine-ketamine and atipamezole

This communication reports a partially reversible chemical immobilization protocol used for translocation and veterinary care in giant otter (Pteronura brasiliensis; GO). Six GOs (three males and three females) weighing 24.8 +/- 4.0 kg (mean +/- SD) and ranging in age from 16 to 42 mo old were anesthetized with an i.m. combination of medetomidine (29 +/- 3 microg/kg) and ketamine (3.9 +/- 0.4 mg/kg). To perform all procedures, two otters required an additional dose of ketamine (1.5 mg/kg). Anesthesia was reversed with atipamezole i.m. (147 +/- 14 mg/kg). The mean induction time and recovery times were 12 +/- 5 and 4 min (range, 0-9 min), respectively, with an anesthesia time of 47 +/- 16 min. According to these results, the combination of medetomidine (30 microg/kg i.m.) and ketamine (4 mg/kg i.m.) is a reasonable choice for inducing anesthesia in GOs.

Acupuncture effects on cardiac functions measured by cardiac magnetic resonance imaging in a feline model

The usefulness of acupuncture (AP) as a complementary and/or alternative therapy in animals is well established but more research is needed on its clinical efficacy relative to conventional therapy, and on the underlying mechanisms of the effects of AP. Cardiac magnetic resonance imaging (CMRI), an important tool in monitoring cardiovascular diseases, provides a reliable method to monitor the effects of AP on the cardiovascular system. This controlled experiment monitored the effect electro-acupuncture (EA) at bilateral acupoint Neiguan (PC6) on recovery time after ketamine/xylazine cocktail anesthesia in healthy cats. The CMRI data established the basic feline cardiac function index (CFI), including cardiac output and major vessel velocity. To evaluate the effect of EA on the functions of the autonomic nervous and cardiovascular systems, heart rate, respiration rate, electrocardiogram and pulse rate were also measured. Ketamine/xylazine cocktail anesthesia caused a transient hypertension in the cats; EA inhibited this anesthetic-induced hypertension and shortened the post-anesthesia recovery time. Our data support existing knowledge on the cardiovascular benefits of EA at PC6, and also provide strong evidence for the combination of anesthesia and EA to shorten post-anesthesia recovery time and counter the negative effects of anesthetics on cardiac physiology.

The Association of Shelter Veterinarians veterinary medical care guidelines for spay-neuter programs

As efforts to reduce the overpopulation and euthanasia of unwanted and unowned dogs and cats have increased, greater attention has been focused on spay-neuter programs throughout the United States. Because of the wide range of geographic and demographic needs, a wide variety of programs have been developed to increase delivery of spay-neuter services to targeted populations of animals, including stationary and mobile clinics, MASH-style operations, shelter services, feral cat programs, and services provided through private practitioners. In an effort to ensure a consistent level of care, the Association of Shelter Veterinarians convened a task force of veterinarians to develop veterinary medical care guidelines for spay-neuter programs. The guidelines consist of recommendations for preoperative care (eg, patient transport and housing, patient selection, client communication, record keeping, and medical considerations), anesthetic management (eg, equipment, monitoring, perioperative considerations, anesthetic protocols, and emergency preparedness), surgical care (eg, operating-area environment; surgical-pack preparation; patient preparation; surgeon preparation; surgical procedures for pediatric, juvenile, and adult patients; and identification of neutered animals), and postoperative care (eg, analgesia, recovery, and release). These guidelines are based on current principles of anesthesiology, critical care medicine, microbiology, and surgical practice, as determined from published evidence and expert opinion. They represent acceptable practices that are attainable in spay-neuter programs.

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.

Xylazine-midazolam-ketamine versus medetomidine-midazolam-ketamine anesthesia in captive Siberian tigers (Panthera tigris altaica)

Two alpha2-adrenoceptor agents, xylazine and medetomidine, in combination with midazolam and ketamine safely and effectively immobilized Siberian tigers (Panthera tigris altaica). The medetomidine protocol used smaller drug volumes, and induction and recovery times were shorter. Although cardiopulmonary abnormalities were noted, none were likely to be life threatening.

Pain management in cats--past, present and future. Part 2. Treatment of pain--clinical pharmacology

Opioids have an unjustified reputation for causing mania in cats, but with refinements in dosing they are now used successfully in this species. The mu-opioid agonists are generally considered the best analgesics. Morphine (0.1-0.3 mg/kg) is effective in a clinical setting. Methadone (up to 0.5 mg/kg) has a similar profile to morphine. Pethidine (Demerol, meperidine; 2-5 mg/kg) is a useful analgesic with a faster onset but shorter duration of action than morphine. Oxymorphone and hydromorphone (0.05-0.1 mg/kg) are widely used in the USA. These opioids are more potent (up to 10 times), and longer acting than morphine in cats. Butorphanol (0.1-0.4 mg/kg) is a mu-opioid antagonist that produces its analgesic actions through kappa agonist activity. It rapidly reaches a ceiling effect, is short acting and is a weaker analgesic than pure mu opioids. Buprenorphine (0.01-0.02 mg/kg), a partial mu-agonist, is the most popular opioid used in small animal practice in the UK, other parts of Europe, Australia and South Africa. In clinical studies it has produced better analgesia than several other opioids and appears to be highly suitable for perioperative pain management in cats. NSAIDs are also used in cats for pain management, although cats metabolise these differently from other species. With appropriate dosing, carprofen (1-4 mg/kg) and meloxicam (0.3 mg/kg) have proved highly effective with few side effects. The use of ketoprofen (2 mg/kg), tolfenamic acid (4 mg/kg) and vedaprofen (0.5 mg/kg) has been reported in cats. Other less traditional analgesics such as ketamine, medetomidine and local anaesthetics are also used for clinical pain management. The transmucosal, transdermal and epidural routes offer novel methods for administration of analgesic drugs and have considerable potential for improving techniques in feline pain management.

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.

Clinical use of dexmedetomidine as premedicant in cats undergoing propofol-sevoflurane anaesthesia

The purpose of this report was to evaluate the cardiorespiratory effects and efficacy of dexmedetomidine as a premedicant agent in cats undergoing ovariohysterectomy anaesthetized with propofol-sevoflurane. Cats were randomly divided into two groups of eight animals each. Dexmedetomidine (0.01 mg/kg) or 0.9% saline was administered intravenously (D and S, respectively). After 5 min, propofol was administered intravenously and anaesthesia was maintained with sevoflurane. Heart and respiratory rates, arterial blood pressure, oxygen saturation, rectal temperature and the amount of propofol needed for induction were measured. Premedication with dexmedetomidine reduced the requirement of propofol (6.7+/-3.8 mg/kg), but induced bradycardia, compared with the administration of saline (15.1+/-5.1 mg/kg). Recovery quality was significantly better in D but no significant difference in time to return of swallowing reflex was observed between groups (D=2.5+/-0.5 min; S=3.2+/-1.8 min). In conclusion, dexmedetomidine is a safe and effective agent for premedication in cats undergoing propofol-sevoflurane anaesthesia with minimal adverse effects.

Evaluation of the sedative and cardiorespiratory effects of dexmedetomidine, dexmedetomidine-butorphanol, and dexmedetomidine-ketamine in cats

OBJECTIVE

To determine sedative and cardiorespiratory effects of dexmedetomidine alone and in combination with butorphanol or ketamine in cats.

DESIGN

Randomized crossover study.

ANIMALS

6 healthy adult cats.

PROCEDURES

Cats were given dexmedetomidine alone (10 microg/kg [4.5 mg/lb], IM), a combination of dexmedetomidine (10 microg/kg, IM) and butorphanol (0.2 mg/kg [0.09 mg/lb], IM), or a combination of dexmedetomidine (10 microg/kg, IM) and ketamine (5 mg/kg [2.3 mg/lb], IM). Treatments were administered in random order, with > or = 1 week between treatments. Physiologic variables were assessed before and after drug administration. Time to lateral recumbency, duration of lateral recumbency, time to sternal recumbency, time to recovery from sedation, and subjective evaluation of sedation, muscle relaxation, and auditory response were assessed.

RESULTS

Each treatment resulted in adequate sedation; time to lateral recumbency, duration of lateral recumbency, and time to recovery from sedation were similar among treatments. Time to sternal recumbency was significantly greater after administration of dexmedetomidine-ketamine. Heart rate decreased significantly after each treatment; however, the decrease was more pronounced after administration of dexmedetomidine-butorphanol, compared with that following the other treatments. Systolic and diastolic blood pressure measurements decreased significantly from baseline with all treatments; 50 minutes after drug administration, mean blood pressure differed significantly from baseline only when cats received dexmedetomidine and butorphanol.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that in cats, administration of dexmedetomidine combined with butorphanol or ketamine resulted in more adequate sedation, without clinically important cardiovascular effects, than was achieved with dexmedetomidine alone.

Evaluation of sedative and cardiorespiratory effects of romifidine and romifidine-butorphanol in cats

OBJECTIVE

To determine sedative and cardiorespiratory effects of romifidine alone and romifidine in combination with butorphanol and effects of preemptive atropine administration in cats sedated with romifidine-butorphanol.

DESIGN

Randomized crossover study.

ANIMALS

6 healthy adult cats.

PROCEDURES

Cats were given saline (0.9% NaCl) solution followed by romifidine alone (100 microg/kg [45.4 microg/lb], i.m.), saline solution followed by a combination of romifidine (40 microg/kg [18.1 microg/lb], i.m.) and butorphanol (0.2 mg/kg [0.09 mg/lb], i.m.), or atropine (0.04 mg/kg [0.02 mg/lb], s.c.) followed by romifidine (40 microg/kg, i.m.) and butorphanol (0.2 mg/kg, i.m.). Treatments were administered in random order, with > or = 1 week between treatments. Physiologic variables were determined before and after drug administration. Time to recumbency, duration of recumbency, time to recover from sedation, and subjective evaluation of sedation, muscle relaxation, and analgesia were assessed.

RESULTS

Bradycardia developed in all cats that received saline solution and romifidine-butorphanol or romifidine alone. Preemptive administration of atropine prevented bradycardia for 50 minutes in cats given romifidine-butorphanol. Oxyhemoglobin saturation was significantly decreased 10 minutes after romifidine-butorphanol administration in atropine-treated cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that administration of romifidine alone or romifidine-butorphanol causes a significant decrease in heart rate and that preemptive administration of atropine in cats sedated with romifidine-butorphanol effectively prevents bradycardia for 50 minutes.

Comparison of medetomidine and dexmedetomidine as premedication in isoflurane anaesthesia for orthopaedic surgery in domestic sheep

The objective of the present study was to determine the potency of dexmedetomidine in relation to medetomidine in sheep undergoing orthopaedic surgery by comparing the anaesthetic requirements and cardiovascular changes at a dose relationship that represented equipotency in vitro. Twenty-four non-pregnant, female sheep were used. The study was carried out as a blind, randomized, experimental trial. Group 1 received 5 micrograms/kg bodyweight (BW) dexmedetomidine and group 2 received 10 micrograms/kg BW medetomidine intravenously 5 min prior to induction of anaesthesia. Anaesthesia was induced with ketamine (2.0 mg/kg BW intravenously) and maintained with isoflurane in 100% oxygen. End expired anaesthetic concentration (FEIso), end expired carbon dioxide concentration (FECO2), respiratory frequency (fR), direct arterial blood pressures, heart rates (HR) and arterial blood gases were monitored. Data were averaged over time and tested for differences between groups by independent t-tests, and analysis of variance for repeated measures. Average FEIso concentrations required to maintain a surgical plane of anaesthesia were not different between groups (1: 1.02 +/- 0.04%; 2: 0.99 +/- 0.07%). There was no difference in HR, arterial blood pressures, fR, FECO2 and arterial blood gases between groups. Average mean PaO2 were 279.54 +/- 113.37 mmHg and 220.21 +/- 102.15 mmHg with individual minimum values of 27.2 mmHg and 58.5 mmHg in groups 1 and 2, respectively. In conclusion, intravenous dexmedetomidine at 5 micrograms/kg BW and medetomidine at 10 micrograms/kg BW have the same effects on isoflurane requirements and cardiopulmonary parameters in sheep, indicating an equipotent dose relationship. Both preparations induced moderate to severe hypoxaemia in individual sheep.

Cardiorespiratory effects of four alpha2-adrenoceptor agonist-ketamine combinations in captive red wolves

OBJECTIVE

To evaluate the cardiopulmonary effects of immobilizing doses of xylazine-ketamine (XK), medetomidine-ketamine (MK), medetomidine-ketamine-acepromazine (MKA), and medetomidine-butorphanol-ketamine (MBK) in captive red wolves.

DESIGN

Prospective study.

ANIMALS

32 adult captive red wolves.

PROCEDURE

Wolves were randomly assigned to 1 of 4 treatment groups: XK, MK, MKA, or MBK. Physiologic variables measured included heart rate, blood pressure, respiratory rate, tidal volume, oxygen-hemoglobin saturation (Spo2), end-tidal CO2, arterial blood gases, and rectal temperature. Induction time, muscle relaxation, and quality of recovery were assessed.

RESULTS

Heart rates were lower in wolves in the MBK group than for the other groups. All 4 drug combinations induced considerable hypertension, with diastolic pressures exceeding 116 mm Hg. Blood pressure was lowest in wolves receiving the MBK combination. Respiratory rate was significantly higher in wolves receiving XK, MK, and MKA. Tidal volumes were similar for all groups. Wolves receiving XK, MK, and MKA were well-oxygenated throughout the procedure (SPo2 > 93%), whereas those receiving MBK were moderately hypoxemic (87% < Spo2 < 93%) during the first 20 minutes of the procedure. Hyperthermia was detected initially following induction in all groups.

CONCLUSIONS AND CLINICAL RELEVANCE

The alpha2-adrenoceptor agonist-ketamine combinations provide rapid reversible anesthesia for red wolves but cause severe sustained hypertension. Such an adverse effect puts animals at risk for development of cerebral encephalopathy, retinal hemorrhage, pulmonary edema, and myocardial failure. Although the MBK combination offers some advantages over the others, it is advised that further protocol refinements be made to minimize risks associated with acute hypertension.