Perioperative anaesthetic complications in healthy cats undergoing anaesthesia for neutering in first opinion practice

OBJECTIVES

The aim of the present study was to identify the incidence of common perioperative anaesthetic complications in cats undergoing anaesthesia for neutering in three UK first opinion practices.

METHODS

A retrospective anaesthetic record analysis was performed on cats anaesthetised for neutering at practices 1 and 2 between 9 December 2017 and 2 February 2021 and practice 3 between 9 March 2020 and 7 January 2021. A search of the practice management system identified all cats that had undergone neutering in the selected timeframe. Data from 1019 cats were included in the study. Information relating to patient characteristics and data from the anaesthesia session were extracted from electronic patient records and anaesthesia record charts and entered into an Excel spreadsheet. A definition of the complications was created after reviewing the literature and their incidence determined from the data set. Comparisons between different groups of cats in the study were made using a χ2 test for homogeneity or Fisher's exact tests to identify factors associated with increased incidence of complications.

RESULTS

The anaesthetic-related mortality was 1/1019 (0.10%). The most common complications were hypotension (22.6%), bradycardia (16.7%) and hypothermia (13.8%). Less common complications were hypocapnia (12.7%), hypercapnia (8.7%), tachycardia (6.6%), apnoea (3.1%), hyperthermia (1.7%), hypertension (1.4%), endotracheal tube obstruction (1.1%), hypoxia (0.3%), undesirable recovery (0.6%) and cardiac arrhythmia (0.2%). Factors associated with increased risk of hypotension were acepromazine pre-anaesthetic medication, higher maximum isoflurane dose, longer anaesthetic duration and lower body weight. Factors associated with increased risk of bradycardia were medetomidine pre-anaesthetic medication, longer anaesthetic duration and higher body weight. Factors associated with increased risk of hypothermia were higher maximum isoflurane dose, increased anaesthetic duration and lower body weight.

CONCLUSIONS AND RELEVANCE

This study showed that anaesthetic complications were frequently observed, with complications documented in 53.4% of the cats in the study. The information in this study may help to guide prioritisation of monitoring in feline anaesthesia.

Comparison of analgesic efficacy of tramadol, morphine and methadone in cats undergoing ovariohysterectomy

OBJECTIVES

The aim of this study was to compare the analgesic efficacy and the effect on physiological variables and behavior of the use of tramadol, methadone and morphine as preoperative analgesia in healthy cats undergoing elective ovariohysterectomy.

METHODS

Cats undergoing ovariohysterectomy were randomly assigned to receive one of the following premedication treatments intramuscularly: methadone (0.2 mg/kg; n = 10); morphine (0.2 mg/kg; n = 10); or tramadol (3 mg/kg; n = 10). Induction of anesthesia was done with propofol, and maintenance of anesthesia was done with isoflurane. Intraoperative heart rate, arterial blood pressure, respiratory rate, end-tidal isoflurane concentration and frequency of rescue analgesia (fentanyl 2.5 µg/kg) were compared between groups. Postoperative analgesia was assessed using the UNESP-Botucatu Multidimensional Composite Pain Scale, and perioperative serum glucose, cortisol concentrations and postoperative rescue analgesia were evaluated.

RESULTS

Intraoperative rescue analgesia was required in 76.5% of cats at some time during surgery, and 27% of cats required postoperative rescue analgesia up to 6 h after extubation. There were no significant differences between groups with respect to intraoperative and postoperative rescue analgesia, pain scale scores and end-tidal isoflurane concentrations. In the immediate postoperative period, after extubation, most of the patients presented with hypothermia; however, 1-6 h postoperatively, hyperthermia was observed in most of the patients, and was most common in the tramadol group.

CONCLUSIONS AND CLINICAL RELEVANCE

Under the conditions of this study, methadone, morphine and tramadol produced satisfactory postoperative analgesia in most of the cats undergoing ovariohysterectomy, and the effects lasted up to 6 h postoperatively. Intraoperative analgesia was not sufficient in most cases. Significant cardiovascular or respiratory effects contraindicating the use of these drugs were not found. Postanesthetic hyperthermia occurred with all opioids studied and was more frequent in the tramadol group.

Effect of a single intravenous injection of branched chain amino acids on body temperature of cats undergoing general anesthesia

OBJECTIVE

To evaluate the effect of a single intravenous injection of branched chain amino acids (BCAAs) on body temperature in cats undergoing general anesthesia.

STUDY DESIGN

Prospective, blinded, randomized, crossover, experimental study.

ANIMALS

A total of 10 healthy adult cats (five female and five male).

METHODS

Cats were anesthetized three times with three different treatments in a random order: 3 mL kg-1 lactated Ringer's solution (LRS), 100 mg kg-1 BCAAs (B100) or 200 mg kg-1 BCAAs (B200) solution immediately before induction of anesthesia. After induction, rectal temperature was measured every 5 minutes. Blood samples were collected for the measurement of blood glucose (BG) just before induction, at the end of the 90 minute period of anesthesia, and 24 hours after anesthesia induction. The differences between baseline and each subsequent rectal temperature, and BG measurements were analyzed. Areas under the curve (AUCs) for temperature differences were calculated for each animal for the anesthetic period (AUCT0-90). Parametric or nonparametric data were analyzed by one-way repeated measures anova or Friedman test. A value of p < 0.05 was considered significant.

RESULTS

There were no significant differences in AUCT0-90 between groups: 41.6 ± 7.7 for LRS, 43.4 ± 6.9 for B100 and 42.9 ± 7.5 for B200 (p = 0.368). No significant differences were observed in BG between groups at 90 minutes and 24 hours after anesthesia induction (p = 0.283 and p = 0.089, respectively). The incidence of hypoglycemia [BG ≤ 3.17 mmol L-1 (57 mg dL-1)] after anesthesia tended to be higher in both B100 (4/10 cats) and B200 groups (3/10 cats) than in LRS group (1/10 cats).

CONCLUSIONS AND CLINICAL RELEVANCE

A single, preanesthetic intravenous injection of BCAAs did not attenuate heat loss during anesthesia. More cats were hypoglycemic in the BCAA groups than in the LRS group.

High and Hyper: Fentanyl Induces Psychomotor Side-Effects in Healthy Pigs

Analgesic effects of fentanyl have been investigated using behavior. The behavioral effects of fentanyl and possible serotonergic influence are largely unknown. We therefore investigated behavioral effects of fentanyl, with or without the serotonin antagonist ketanserin, in pigs. Fourteen mixed-breed pigs, weighing 17-25 kg were included in a randomised blinded prospective, balanced three-group study. Ten pigs received first 5 and then 10 µg/kg of fentanyl intravenously. Ketanserin at 1 mg/kg or saline was given intravenously as a third injection. Four control pigs received three injections of saline. Behavior was video-recorded. The distance moved was automatically measured by commercially available software, and behaviors manually scored in retrospect. Fentanyl inhibited resting and playing, and induced different repetitive behaviors. The mean (SD) distance moved in the control group and fentanyl group was 21.3 (13.0) and 57.8 (20.8) metres respectively (p < 0.05 for pairwise comparison). A stiff gait pattern was seen after fentanyl injection for median (range) 4.2 (2.8-5.1) minutes per 10 min, which was reduced to 0 (0-4) s after ketanserin administration. Conclusion: fentanyl-induced motor and behavioral effects, and serotonergic transmission may be involved in some of them. The psychomotor side effects of fentanyl could potentially interfere with post-operative pain evaluation in pigs.

Chemical immobilisation of lions: weighing up drug effectiveness versus clinical effects

Selection of an effective drug combination to immobilise African lions (Panthera leo) requires balancing immobilisation effectiveness with potential side effects. We compared the immobilisation effectiveness and changes to physiological variables induced by three drug combinations used for free-ranging African lions. The lions (12 animals per drug combination) were immobilised with tiletamine-zolazepam-medetomidine (TZM), ketamine-medetomidine (KM) or ketamine-butorphanol-medetomidine (KBM). Induction, immobilisation, and recovery were timed, evaluated using a scoring system, and physiological variables were monitored. The drugs used for immobilisation were antagonised with atipamezole and naltrexone. The quality of induction was rated as excellent for all drug combinations and induction times (mean ± SD) did not differ between the groups (10.54 ± 2.67 min for TZM, 10.49 ± 2.63 min for KM, and 11.11 ± 2.91 min for KBM). Immobilisation depth was similar over the immobilisation period in the TZM and KBM groups, and initially light, progressing to deeper in lions administered KM. Heart rate, respiratory rate and peripheral arterial haemoglobin saturation with oxygen were within the expected range for healthy, awake lions in all groups. All lions were severely hypertensive and hyperthermic throughout the immobilisation. Following antagonism of immobilising drugs, lions immobilised with KM and KBM recovered to walking sooner than those immobilised with TZM, at 15.29 ± 10.68 min, 10.88 ± 4.29 min and 29.73 ± 14.46 min, respectively. Only one lion in the KBM group exhibited ataxia during recovery compared to five and four lions in the TZM and KM groups, respectively. All three drug combinations provided smooth inductions and effective immobilisations but resulted in hypertension. KBM had an advantage of allowing for shorter, less ataxic recoveries.

Successful autologous transfusion from the subcutaneous space in a domestic shorthair cat with suspected anticoagulant rodenticide toxicity

Case summary

A 6-month-old female entire domestic shorthair cat was presented with a 4-day history of progressive swelling over the dorsal cranium. Subsequent diagnostics revealed a large haematoma, a secondary haemostatic defect and a moderate anaemia. The owner disclosed access to multiple brodifacoum bait stations. The anaemia and haematoma progressed despite treatment with fresh frozen plasma and phytonadione and the cat developed signs of haemorrhagic shock. Allogenic transfusion was declined due to cost and 18 ml of blood was aspirated from the haematoma and transfused. The cat stabilised quickly and was discharged the next day with oral phytonadione.

Relevance and novel information

Autologous transfusion from the subcutaneous space has not been previously reported. It was well tolerated and life-saving in this case.

Sedation quality of alfaxalone associated with butorphanol, methadone or pethidine in cats injected into the supraspinatus or the quadriceps muscle

OBJECTIVES

The aim of this study was to compare the quality of sedation with three different anaesthetic protocols (alfaxalone combined with butorphanol, methadone or pethidine) administered intramuscularly in cats, and to evaluate the influence of the injection site (between supraspinatus and quadriceps muscles) on the onset and quality of sedation.

METHODS

A total of 151 cats were selected for this study. Cats were sedated with alfaxalone (3 mg/kg) combined with either butorphanol (0.3 mg/kg; n = 50), methadone (0.3 mg/kg; n = 53) or pethidine (5 mg/kg; n = 48). The combination was injected intramuscularly into the supraspinatus (n = 79) or quadriceps muscle (n = 72). The data included a scoring system for the quality of sedation and physiological parameters, such as heart rate (HR), respiratory rate, body temperature and occurrence of mydriasis, monitored during the first 30 mins of anaesthesia.

RESULTS

The opioid associated with alfaxalone influenced the overall sedation score, the degree of myorelaxation, the occurrence of mydriasis and HR. The overall sedation score was poorer with butorphanol than with methadone (P = 0.008), and butorphanol induced a lower degree of myorelaxation than methadone (P = 0.013). The injection into the supraspinatus showed better qualitative results for sedation and a faster onset time (in about 3 mins) than that into the quadriceps (P <0.001). HR decreased from baseline (P <0.001) and over time (P <0.001), mainly in cats of the butorphanol-supraspinatus and pethidine-quadriceps groups (P = 0.004). The occurrence of mydriasis was lower after butorphanol than after methadone and pethidine (P = 0.025), while the incidence of side effects did not differ among groups.

CONCLUSIONS AND RELEVANCE

All three protocols provided a good quality of sedation and allowed performing the scheduled procedure. Moreover, the injection into the supraspinatus muscle showed superior results in all the qualitative scores of sedation and quicker onset time than that into the quadriceps muscle.

Single-dose pharmacokinetics and bioavailability of a novel extended duration transdermal buprenorphine solution in cats

A novel transdermal buprenorphine solution (TBS) was developed for evaluation in order to make available an extended duration opioid analgesic for cats. Healthy adult cats were administered a single TBS dose of 10 mg (1.57-4.35 mg/kg), 30 mg (4.72-13.0 mg/kg), or 50 mg (7.87-21.7 mg/kg) (4 cats per group) applied topically to the unclipped dorsal cervical skin and plasma buprenorphine concentrations were evaluated through 7 days. To determine the absolute bioavailability of TBS, healthy cats were administered single TBS dose of 20 mg (3.33-4.76 mg/kg) or 0.05 mg (0.008-0.011 mg/kg) IV buprenorphine (6 cats per group). The mean ± standard deviation maximum plasma buprenorphine concentrations (C_max ) were 10.5 ± 6.28, 18.6 ± 8.68, and 22.5 ± 4.47 ng/ml following 10, 30, and 50 mg doses, respectively, with the time of C_max occurrence (t_max ) typically occurring at 2-12 h post-dosing. Mean plasma buprenorphine terminal half-lives ranged between 78.3 and 91.2 h. Increasing the dose threefold and fivefold from the 10 mg dose increased the exposure by 2.8- and 3.6-fold, respectively, indicating that plasma buprenorphine exposure increased in a less than proportional manner at doses >30 mg. Transient sedation, mydriasis, and euphoria were observed within 4 h post-dosing. Mean rectal temperatures were increased 0.6-0.9°C greater than baseline (37.4-37.8°C) through 168 h post-dosing. The absolute bioavailability was 16.0% (90% CI: [11.8%-21.7%]). Flip-flop pharmacokinetics were observed with a terminal elimination half-life of 0.82 ± 0.13 and 64.9 ± 15.0 h for IV buprenorphine and 20 mg of TBS, respectively. A single administration of TBS over a range of doses resulted in extended plasma buprenorphine concentrations and opioid physiological and behavioral effects.

Multicentered masked placebo-controlled phase 3 clinical study of an extended duration transdermal buprenorphine solution for post-operative pain in cats

A prospective, double masked, placebo-controlled, multicentered phase 3 clinical study was conducted to evaluate the safety and effectiveness of transdermal buprenorphine solution (TBS) for the control of post-operative pain in cats. A total of 228 cats from 12 US investigational sites met the enrollment criteria of which 107 placebo- and 112 TBS-treated cats were included into the per protocol efficacy analysis. The dose of TBS was 8 mg (0.4 ml) to cats 1.2 to 3 kilograms and 20 mg (1 ml) to cats >3 to 7.5 kilograms applied topically to the dorsal unclipped cervical skin 1-2 h prior to the undergoing elective surgical reproductive sterilization in conjunction with forelimb onychectomy. Interactive pain assessments and physiological variables were quantified through 96 h following recovery from anesthesia, and rescue analgesia was administered any time that pain control was scored inadequate. Cats requiring rescue analgesia or experiencing an adverse event suspected to be treatment related were considered treatment failures. Sixty-five and 23 cats were considered treatment failures in the placebo and TBS groups, respectively, with most occurring on the day of surgery. The treatment success rates were 0.40 (95% confidence interval [CI]: [0.28-0.53]) and 0.81 (95% CI: [0.70-0.89]) in the placebo and TBS groups, respectively, and the difference was significant (p < .05). Adverse events occurred at a similar frequency and were not clinically meaningful in either treatment group. The post-operative body temperatures over the duration of the study were on average 0.35 (95% CI: [0.20-0.50]) °C higher than baseline in TBS-treated cats and were not clinically meaningful, an observation typical of opioids in cats. These results serve as substantial evidence that TBS is safe and effective for the control of orthopedic and soft tissue post-operative pain in cats when a single topical dose is applied 1-2 h prior to surgery.

Multicentered masked placebo-controlled phase 2 clinical study of an extended duration transdermal buprenorphine solution for postoperative pain in cats

A prospective, double-masked, placebo-controlled, multicentered phase 2 clinical study was conducted to select the transdermal buprenorphine solution (TBS) dosage for the control of postoperative pain in cats. One-hundred fifteen (115) cats were randomized to a single topical dose of placebo solution, low-TBS dosage (1.91-2.07 mg/kg) or high-TBS dosage (4.27-4.88 mg/kg) prior to surgical reproductive sterilization in conjunction with forelimb onychectomy. The low- and high-TBS doses were applied 2-4 and 1-2 hours prior to surgery. Interactive pain assessments and physiological variables were quantified through 96 hours post-anesthetic recovery and rescue analgesia was administered any time that analgesia was considered inadequate. Cats requiring rescue analgesia were considered treatment failures. The estimated overall treatment success rates from generalized linear mixed effects model analysis were 0.10 (95% CI: [0.02-0.36]), 0.56 (95% CI: [0.25-0.83]), 0.71 (95% CI: [0.38-0.91]) in the placebo-, low-, and high-TBS dose groups, respectively. Success rates for both TBS treatment groups were superior to placebo. Adverse events were infrequent in all treatment groups although the postoperative body temperatures over the duration of the study were on average 0.31 (95% CI: [0.08-0.55]) and 0.30 (95% CI: [0.05-0.53]) °C higher in low- and high-TBS dose cats, respectively, compared to placebo. It is concluded that both the low- and high-TBS dosages were safe and effective. The high-TBS dosage resulted in a greater proportion of treatment successes over 96 h, had a more acceptable preoperative application time of 1-2 h prior to surgery, and was therefore selected for further study.

2022 AAHA Pain Management Guidelines for Dogs and Cats

These updated guidelines present a practical and logical approach to the assessment and management of acute and chronic pain in canine and feline patients. Recognizing pain is fundamental to successful treatment, and diagnostic guides and algorithms are included for assessment of both acute and chronic pain. Particularly for chronic pain, capturing owner evaluation is important, and pain-assessment instruments for pet owners are described. Expert consensus emphasizes proactive, preemptive pain management rather than a reactive, "damage control" approach. The guidelines discuss treatment options centered on preemptive, multimodal analgesic therapies. There is an extensive variety of pharmacologic and nonpharmacologic therapeutic options for the management of acute and chronic pain in cats and dogs. The guidelines include a tiered decision tree that prioritizes the use of the most efficacious therapeutic modalities for the treatment of acute and chronic pain.

Retrospective investigation of an association between high-dose buprenorphine and perpetuation of post-anesthesia hyperthermia in cats following ovariohysterectomy

OBJECTIVES

We evaluated a potential association between the administration of high-dose buprenorphine and perpetuation of hyperthermia in cats following ovariohysterectomy (OVH). We hypothesized that buprenorphine 0.24 mg/kg subcutaneously (SC) would result in longer-lasting postoperative hyperthermia in cats vs a group receiving morphine 0.1 mg/kg SC.

METHODS

Anesthetic records from cats admitted for OVH as part of surgical exercises for second year veterinary medicine students in 2018 and 2019 were collected. All cats were sedated with dexmedetomidine 20 µg/kg and morphine 0.1 mg/kg intramuscularly. Anesthesia was induced with propofol and maintained with isoflurane in oxygen. At extubation, cats received morphine 0.1 mg/kg SC in 2018 and buprenorphine 0.24 mg/kg SC in 2019. Temperature was measured rectally prior to sedation, esophageally during anesthesia and rectally at 1, 4 and 16-20 h after extubation. Demographic data and temperature prior to administration of postoperative opioids were compared with t-tests. The effects of treatment (opioids) and time on postoperative rectal temperature and on the incidence of hyperthermia (temperature >39.2°C) were evaluated with mixed and generalized linear mixed-effect models. Significance was set at P <0.05.

RESULTS

There were no differences in demographic characteristics between treatment groups (all P ⩾0.2). Intraoperative esophageal temperature was lower in cats scheduled to receive morphine (mean ± SD 36.6 ± 0.2) than in those receiving buprenorphine (36.9 ± 1.0) (P <0.0001). Postoperative temperature was higher for cats receiving buprenorphine than for those receiving morphine (P <0.0001). The incidence of hyperthermia 16-20 h after opioid administration was 56% for morphine and 73% for buprenorphine (P = 0.03).

CONCLUSIONS AND RELEVANCE

Buprenorphine 0.24 mg/kg SC for postoperative analgesia in cats was associated with hyperthermia that persisted for 16-20 h after administration, and the incidence of hyperthermia for this group was higher than in the cats that received morphine 0.1 mg/kg SC.

Comparison of the effects of butorphanol-midazolam-medetomidine and butorphanol-azaperone-medetomidine in wild common palm civets (Paradoxurus musangus)

OBJECTIVE

To assess the efficacy of butorphanol-azaperone-medetomidine (BAM) and butorphanol-midazolam-medetomidine (BMM) protocols for immobilization of wild common palm civets (Paradoxurus musangus) with subsequent antagonization with atipamezole.

STUDY DESIGN

Prospective, randomized, blinded clinical trial.

ANIMALS

A total of 40 adult wild common palm civets, 24 female and 16 male, weighing 1.5-3.4 kg.

METHODS

The civets were randomly assigned for anesthesia with butorphanol, azaperone and medetomidine (0.6, 0.6 and 0.2 mg kg^-1, respectively; group BAM) or with butorphanol, midazolam and medetomidine (0.3, 0.4 and 0.1 mg kg^-1, respectively; group BMM) intramuscularly (IM) in a squeeze cage. When adequately relaxed, the trachea was intubated for oxygen administration. Physiological variables were recorded every 5 minutes after intubation. Following morphometric measurements, sampling, microchipping and parasite treatment, medetomidine was reversed with atipamezole at 1.0 or 0.5 mg kg^-1 IM to groups BAM and BMM, respectively. Physiological variables and times to reach the different stages of anesthesia were compared between groups.

RESULTS

Onset time of sedation and recumbency was similar in both groups; time to achieve complete relaxation and tracheal intubation was longer in group BAM. Supplementation with isoflurane was required to enable intubation in five civets in group BAM and one civet in group BMM. All civets in group BAM required topical lidocaine to facilitate intubation. End-tidal carbon dioxide partial pressure was lower in group BAM, but heart rate, respiratory rate, rectal temperature, peripheral hemoglobin oxygen saturation and mean arterial blood pressure were not different. All civets in both groups recovered well following administration of atipamezole.

CONCLUSIONS AND CLINICAL RELEVANCE

Both BAM and BMM combinations were effective for immobilizing wild common palm civets. The BMM combination had the advantage of producing complete relaxation that allowed intubation more rapidly.

Minimally invasive ethyl cellulose ethanol ablation in domesticated cats with naturally occurring head and neck cancers: Six cats

It is difficult to retain tumoricidal doses of ethanol in large or unencapsulated tumours without causing intoxication or damaging surrounding tissue. Ethyl cellulose-ethanol ablation (ECEA) overcomes this limitation by trapping ethanol intratumorally. To evaluate the safety of ECEA and to develop a clinically feasible workflow, a single-arm pilot study was performed in cats with lingual/sublingual squamous cell carcinoma (SCC). Six cats underwent intratumoral injection of 6% ethyl cellulose in ethanol. Subjects were observed overnight. There was mild bleeding and transient hyperthermia, and injection site pain and swelling that improved with anti-inflammatory drugs. Serum ethanol was minimally elevated; the mean concentration peaked 1 hour after injection (129 +/- 15.1 nM). Cats were rechecked at weeks 1 and 2; booster treatments were given in cats (n = 3) with stable quality of life and partial response to therapy. Recheck examinations were then performed monthly. The longest tumour dimension increased in each animal (progressive disease via cRECIST); however, estimated tumour volume was reduced in 3 of 6 cats, within 1 week of ECEA. All cats were euthanized (median survival time 70 days) because of local tumour progression and/or lingual dysfunction that was likely hastened by ECEA. ECEA is not a viable treatment for feline lingual/sublingual SCC; tumour volume was effectively reduced in some cats, but the simultaneous loss of lingual function was poorly tolerated. Further optimization may make ECEA a useful option for SCC at other oral sites in the cat, and for head and neck malignancies in other species.

Sustained release buprenorphine effectively attenuates postoperative hypersensitivity in an incisional pain model in neonatal rats (Rattus norvegicus)

Despite the need for safe and effective postoperative analgesia in neonates, research regarding pain management in neonatal rodents is relatively limited. Here, we investigate whether sustained release buprenorphine (Bup SR) effectively attenuates thermal hypersensitivity in a neonatal rat model of incisional pain. Male and female postnatal day 3 Sprague Dawley rat pups (n = 34) were randomly assigned to one of four treatment groups: 1) saline (control), 0.1 mL, once subcutaneously (SC); 2) buprenorphine HCl (Bup HCl), 0.05 mg/kg, once SC; 3) low dose Bup SR (low-SR), 0.5 mg/kg, once SC; 4) high dose Bup SR (high-SR), 1 mg/kg, once SC. Pups were anesthetized with sevoflurane and a 0.5-cm long skin incision was made over the left lateral thigh. The underlying muscle was dissected and closed using surgical glue. Thermal hypersensitivity testing was performed at 24 h prior to surgery and subsequently at 1, 4, 8, 24, and 48 h post-surgery using an infrared diode laser. Thermal hypersensitivity was attenuated at 1 h post-surgery in the Bup HCl group, while it was attenuated through the entire postoperative period in both low-SR and high-SR groups. This data suggests that a single dose of low-SR (0.5 mg/kg) or high-SR (1 mg/kg) effectively attenuates thermal hypersensitivity for at least 8 h in neonatal rat pups.

Use of nociceptive threshold testing in cats in experimental and clinical settings: a qualitative review

OBJECTIVE

The objective of this study was to review the scientific articles on the use of nociceptive threshold testing (NTT) in cats and to summarize the clinical and experimental applications in this species.

DATABASES USED

Pertinent literature was searched with PubMed, Scopus, Web of Science, Universitätsbibliothek Basel (swissbib Basel Bern) and Google Scholar. The search was then refined manually based first on article titles and abstracts, and subsequently on full texts.

CONCLUSIONS

Of the four classical acute nociceptive models used for NTT, thermal and mechanical are most commonly used in cats. Thermal stimulation is applicable in experimental settings and has been used in pharmacodynamics studies assessing feline antinociception. Although mechanical stimulation is currently less used in cats, in the future it might play a role in the evaluation of clinical feline pain. However, the low response reliability after stimulus repetition within a narrow time interval represents a major limitation for the clinical use of mechanical thresholds in this species. Challenges remain when thermal thresholds are used to investigate analgesics that have the potential to affect skin temperature, such as opioids and α2-adrenergic agonists, and when a model of inflammatory pain is reproduced in experimental cats with the purpose of evaluating non-steroidal anti-inflammatory drugs as analgesics.

Basic Approach to Veterinary Care of Ferrets

The approach to preventive medicine and basic veterinary care in ferrets is very similar to that used in dogs and cats. Special equipment needs are minimal, and pet ferrets can be easily incorporated into a general small animal practice. This chapter describes the unique aspects of handling, restraint, and clinical and treatment techniques used in ferrets.

Hydromorphone-induced Neurostimulation in a Yorkshire Swine (Sus scrofa) after Myocardial Infarction Surgery

Opiates play an important role in the control of pain associated with thoracotomy in both people and animals. However, key side effects, including sedation and respiratory depression, could limit the use of opiates in animals that are lethargic due to cardiac disease. In addition, a rare side effect-neuroexcitation resulting in pathologic behavioral changes (seizures, mania, muscle fasciculation)-after the administration of morphine or hydromorphone is well-documented in many species. In pigs, however, these drugs have been shown to stimulate an increase in normal activity. In the case presented, we describe a Yorkshire-cross pig which, after myocardial infarction surgery, went from nonresponsive to alert, responsive, and eating within 30 min of an injection of hydromorphone. This pig was not demonstrating any signs associated with pain at this time, suggesting that the positive response was due to neural stimulation. This case report is the first to describe the use of hydromorphone-a potent, pure μ opiate agonist-for its neurostimulatory effect in pigs with experimentally-induced cardiac disease.

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.

The antinociceptive effects of intravenous administration of three doses of butorphanol tartrate or naloxone hydrochloride following hydromorphone hydrochloride to healthy conscious cats

OBJECTIVE

To evaluate thermal antinociception from intravenous (IV) administration of hydromorphone alone or followed by butorphanol or naloxone in cats.

STUDY DESIGN

Randomized, controlled, masked, crossover design.

ANIMALS

A group of eight adult female cats.

METHODS

Cats were administered six treatments of two IV injections 30 minutes apart: treatments S-S, two 0.9% saline; H-S, hydromorphone (0.1 mg kg^-1) and saline; H-LB, hydromorphone and butorphanol (0.02 mg kg^-1); H-MB, hydromorphone and butorphanol (0.1 mg kg^-1); H-HB, hydromorphone and butorphanol (0.2 mg kg^-1); H-N, hydromorphone and naloxone (0.04 mg kg^-1). Skin temperature (ST), thermal threshold (TT) and sedation score (SS) were recorded before (baseline) and for 8 hours after the first injection. Percentage maximum possible effect (%MPE), thermal excursion (TE), TT, SS and ST were compared using two-way repeated measures anova or Friedman test followed by Tukey's or Dunn's multiple comparisons test when appropriate. Significance was set at p ≤ 0.05.

RESULTS

Data from seven cats were analyzed. There were no significant differences among treatments in baseline values, SS and within S-S over time. Compared with respective 0.5 hour values following hydromorphone administration, %MPE was significantly lower at 4-8 hours for H-S; at 3-8 hours for H-LB; at 4-8 hours for H-MB; at 6-8 hours for H-HB and at 1-8 hours for H-N. Compared with respective 0.5 hour values, TE was significantly lower at 4-8 hours for H-S; at 3-8 hours for H-LB; at 2 and 4-8 hours for H-MB; at 6 and 8 hours for H-HB and at 1-8 hours for H-N.

CONCLUSIONS AND CLINICAL RELEVANCE

Butorphanol and naloxone reduced hydromorphone-induced thermal antinociception. Butorphanol preserved hydromorphone antinociceptive properties better than naloxone. Butorphanol is recommended during non-life-threatening scenarios as a partial reversal agent for hydromorphone in cats.

Cardiovascular, respiratory and sedative effects of intramuscular alfaxalone, butorphanol and dexmedetomidine compared with ketamine, butorphanol and dexmedetomidine in healthy cats

Objectives The aim of the study was to evaluate the cardiorespiratory effects, quality of sedation and recovery of intramuscular alfaxalone-dexmedetomidine-butorphanol (ADB) and ketamine-dexmedetomidine-butorphanol (KDB), in cats. Methods Nine adult, healthy cats (6.63 ± 1.42 kg) were enrolled in a blinded, randomized, crossover experimental design. Cats were sedated twice intramuscularly, once with ADB (alfaxalone 1 mg/kg, dexmedetomidine 0.005 mg/kg, butorphanol 0.2 mg/kg), and once with KDB (ketamine 5 mg/kg, dexmedetomidine 0.005 mg/kg, butorphanol 0.2 mg/kg), in random order. Data collected included heart rate (HR), arterial blood pressure and blood gas analysis, respiratory rate and sedation score. Analysis of variance with Bonferroni post-hoc correction was used for parametric data, and a Wilcoxon signed rank test was used for non-parametric data. Significance was set at P <0.05. Results Total sedation time was shorter for ADB (90.71 ± 15.12 mins vs 147.00 ± 47.75 mins). Peak sedation was observed within 15 mins in both groups. Quality of recovery was excellent in both groups. HR decreased over time in both groups. Diastolic and mean arterial pressure decreased over time for ADB, becoming significant after 30 mins. All cardiovascular variables were within the clinically acceptable range in both groups. Arterial partial pressure of oxygen was significantly decreased from baseline for KDB at all time points (73 ± 2.5 mmHg [9.7 ± 0.3 kPa] vs ADB 83 ± 2.6 mmHg [11 ± 0.3 kPa]). Hypoventilation was not observed. Conclusions and relevance Both protocols produced acceptable cardiovascular stability. Sedation and recovery quality were good, albeit sedation was shorter with ADB. Although oxygenation was better maintained in the ADB group, all sedated cats should receive oxygen supplementation.

AAFP Feline Anesthesia Guidelines

AIM

The overarching purpose of the AAFP Anesthesia Guidelines (hereafter referred to as the 'Guidelines') is to make anesthesia and sedation safer for the feline patient. Scope and accessibility: It is noteworthy that these are the first exclusively feline anesthesia guidelines authored by an expert panel, making them particularly useful as an extensively referenced, practical resource for veterinary practice teams. Because much of the key content is presented in tabular or visual format, the Guidelines have a high level of accessibility and convenience that invites regular usage. While the recommendations in the Guidelines focus primarily on client-owned cats, the content is also applicable to community-sourced animals with an unknown medical history.

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.

Antinociceptive effects of intravenous administration of hydromorphone hydrochloride alone or followed by buprenorphine hydrochloride or butorphanol tartrate to healthy conscious cats

OBJECTIVE

To evaluate antinociceptive effects of IV administration of hydromorphone alone or followed by buprenorphine or butorphanol to cats.

ANIMALS

6 healthy adult cats.

PROCEDURES

In a randomized, blinded crossover design, cats received each of 4 treatments in which 2 IV injections were given 30 minutes apart: 2 of saline (0.9% NaCl) solution (Sal-Sal) or 1 each of hydromorphone HCl and saline solution (H-Sal), hydromorphone and buprenorphine HCl (H-Bupre), or hydromorphone and butorphanol tartrate (H-Butor). Skin temperature and thermal threshold were recorded before (baseline) and for 12 hours after the first injection. Percentage of maximum possible effect (%MPE) and thermal excursion (TE) were compared among treatments and measurement points.

RESULTS

Compared with baseline values, skin temperature was higher from 0.75 to 2 hours after the first injection for H-Sal; at 0.5, 1, 3, and 4 hours for H-Bupre; from 0.5 to 3 hours for H-Butor; and from 0.5 to 1 hours for Sal-Sal. Thermal excursion was higher than at baseline from 0.25 to 2 hours for H-Sal and H-Bupre and 0.25 to 0.75 hours for H-Butor; %MPE increased from 0.25 to 2 hours for H-Sal, 0.25 to 3 hours for H-Bupre, and 0.25 to 0.75 hours for H-Butor. Results were similar for comparisons with Sal-Sal, except TE was greater for H-Sal versus Sal-Sal and TE and %MPE were greater for H-Bupre versus Sal-Sal from 0.25 to 1 hours after the first injection.

CONCLUSIONS AND CLINICAL RELEVANCE

Butorphanol administration decreased the duration of antinociception achieved with hydromorphone administration in cats. This opioid interaction and its impact on pain management require additional investigation.

[Perioperative pain therapy in dogs and cats - an overview]

Undermanaged pain leads to negative systemic effects that may greatly disturb our patients' welfare. Therefore, a pain assessment tool should be routinely implemented into clinical practice. Validated pain assessment tools are available for dogs and cats. Advanced analgesic therapy follows the principle of a multimodal approach. This means that different analgesic drugs, which act on different targets within the nociceptive pathway, are combined to achieve the desired analgesic effects. In addition to opioids, nonsteroidal anti-inflammatory drugs and local anaesthetics, α2-receptor-agonists, ketamine and gabapentin as well as different nonpharmacologic analgesic techniques are used within the framework of a multimodal analgesic plan.

Application of fast-track surgery principles to evaluate effects of atipamezole on recovery and analgesia following ovariohysterectomy in cats anesthetized with dexmedetomidine-ketamine-hydromorphone

OBJECTIVE

To evaluate the effects of atipamezole hydrochloride on recovery and analgesia following ovariohysterectomy in cats anesthetized with a dexmedetomidine hydrochloride, ketamine hydrochloride, and hydromorphone hydrochloride combination, in accordance with fast-track surgery principles.

DESIGN

Prospective, randomized, clinical trial.

ANIMALS

44 cats.

PROCEDURES

Cats were anesthetized with a combination of dexmedetomidine (15 μg/kg [6.8 μg/lb]), ketamine (5 mg/kg [2.3 mg/lb]), and hydromorphone (0.05 mg/kg [0.023 mg/lb]), IM, supplemented with isoflurane in oxygen. Immediately after ovariohysterectomy, cats received meloxicam (0.2 mg/kg [0.09 mg/lb]) SC and either atipamezole (75 μg/kg [34.1 μg/lb]) or an equivalent volume of saline (0.9% NaCl) solution IM. Pain and sedation were scored at baseline (prior to surgery) and at predetermined intervals after surgery. Time to sternal recumbency was recorded.

RESULTS

The atipamezole group recovered to sternal recumbency faster (median, 15 minutes; range, 5 to 60 minutes) than the saline solution group (median, 60 minutes; range, 15 to 90 minutes]). Pain scores did not differ between groups or at any time, compared with baseline, and were below the intervention threshold for most cats. Sedation scores were significantly greater in the saline solution group (median, 0; range, 0 to 2) at 2 hours after surgery, compared with the atipamezole group (median, 0; range, 0 to 0).

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that administration of atipamezole, compared with saline solution, allowed for a faster recovery from anesthesia with dexmedetomidine-ketamine-hydromorphone in cats following ovariohysterectomy without compromising analgesia. These findings have implications for the provision of appropriate postoperative analgesia following ovariohysterectomy in cats.

Practical use of opioids in cats: a state-of-the-art, evidence-based review

RATIONALE

Recent recognition of the need to improve pain management in cats has led to the investigation of the pharmacokinetics and efficacy of opioid analgesic drugs in this species. The results of these studies may be difficult to interpret because the effect of these drugs varies with dose, route of administration and the method used to assess them. As equipotency of different opioids is not known, it is hard to compare their effects. Animals do not verbalise the pain they feel and, in cats, it may be more difficult to recognise signs of pain in comparison with other species such as dogs.

AIM

This article reviews the use of opioid analgesics in cats. It must be remembered that not all drugs are licensed for use in cats, and that marketing authorisations vary between different countries.

The safety of high-dose buprenorphine administered subcutaneously in cats

The safety of a proprietary formulation of buprenorphine hydrochloride administered subcutaneously (SC) to young cats was investigated in a blinded, randomized study. Four cohorts of eight cats aged approximately 4 months were administered saline, 0.24, 0.72 or 1.20 mg/kg/day buprenorphine SC for nine consecutive days, representing 0×, 1×, 3× and 5× of the intended dose. Cats were monitored daily for evidence of clinical reactions, food and water intake and adverse events (AEs). Physical examinations, clinical pathology, vital signs and electrocardiograms (ECGs) were evaluated at protocol-specified time points. Complete necropsy and histopathologic examinations were performed following humane euthanasia. Four buprenorphine-treated cats experienced AEs during the study, two unrelated and two related to study drug administration. The two cats with AEs considered related to drug administration had clinical signs of hyperactivity, difficulty in handling, disorientation, agitation and dilated pupils in one 0.24 mg/kg/day cat and one 0.72 mg/kg/day cat. All of these clinical signs were observed simultaneously. There were no drug-related effects on survival, injection response, injection site inspections, body weight, food or water consumption, bleeding time, urinalysis, respiration rate, heart rate, ECGs, blood pressures, body temperatures, macroscopic examinations or organ weights. Once daily buprenorphine s.c. injections at doses of 0.24, 0.72 and 1.20 mg/kg/day for 9 consecutive days were well tolerated in young domestic cats.

A review of the studies using buprenorphine in cats

Pain management is a crucial component of feline medicine and surgery. This review critically evaluates studies using buprenorphine in cats and highlights the clinical application of the opioid in this species. The pharmacokinetic-pharmacodynamic (PK-PD) modeling of IV buprenorphine has been best described by a combined effect compartmental/receptor association-dissociation model with negative hysteresis. Therefore, plasma concentrations of the drug are not correlated with analgesia, and clinicians should not expect to observe pain relief immediately after drug administration. In addition, a ceiling effect has not been demonstrated after administration of clinical doses of buprenorphine in cats; dosages of up to 0.04 mg/kg have been reported. The route of administration influences the onset, duration, and magnitude of antinociception and analgesia when using this drug in cats. At clinical dosages, the SC route of administration does not appear to provide adequate antinociception and analgesia whereas the buccal route has produced inconsistent results. Intravenous or IM administration at a dosage of 0.02-0.04 mg/kg is the preferred for treatment of pain in the acute setting. A literature search found 14 clinical trials evaluating buprenorphine sedation, analgesia, or both in cats. There were 22 original research studies reporting the antinociceptive effects of buprenorphine by means of thermal threshold, mechanical threshold, or both, minimal alveolar concentration, or PK-PD. Individual variability in response to buprenorphine administration has been reported, indicating that buprenorphine may not provide sufficient analgesia in some cats. Pain assessment is important when evaluating the efficacy of buprenorphine and determining whether additional analgesic treatment is needed.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

Effect of anesthetic breathing circuit type on thermal loss in cats during inhalation anesthesia for ovariohysterectomy

OBJECTIVE

To compare the effects of a nonrebreathing circuit versus a reduced volume circle anesthetic breathing circuit on body temperature change in cats during inhalation anesthesia for ovariohysterectomy.

DESIGN

Randomized, controlled clinical trial.

ANIMALS

141 female domestic cats hospitalized for routine ovariohysterectomy.

PROCEDURES

Cats were randomly assigned to receive inhalation anesthetics from either a nonrebreathing circuit or a reduced volume circle system with oxygen flow rates of 200 and 30 mL/kg/min (90.9 and 13.6 mL/lb/min), respectively. Body temperatures were monitored throughout the anesthetic period via an intrathoracic esophageal probe placed orally into the esophagus to the level of the heart base.

RESULTS

No difference in body temperature was found between the 2 treatment groups at any measurement time. The duration of procedure had a significant effect on body temperature regardless of the type of anesthetic circuit used.

CONCLUSIONS AND CLINICAL RELEVANCE

Duration of the procedure rather than the type of anesthetic circuit used for inhalation anesthesia was more influential on thermal loss in cats undergoing ovariohysterectomy.

Unusual perianesthetic malignant hyperthermia in a dog

CASE DESCRIPTION

A 7-month-old male Siberian Husky affected by lower motor neuron tetraparesis was anesthetized for electrodiagnostic testing and collection of muscle and nerve biopsy specimens.

CLINICAL FINDINGS

Preanesthetic physical examination revealed a high rectal temperature, and serum biochemical analysis revealed high muscle and liver enzyme activities. The dog was anesthetized twice. The dog was anesthetized with isoflurane and developed moderate hypercarbia and mild hyperthermia. Injectable anesthetic agents were used to anesthetize the dog the second time, during which the dog developed severe malignant hyperthermia. A genetic test performed after anesthesia did not reveal a mutation of the RYR1 gene, the gene that mediates calcium-release channels in skeletal muscle. On the basis of clinical features, and because other neuromuscular disorders were ruled out, a genetic channelopathy involving the skeletal muscle ion channels was suspected.

TREATMENT AND OUTCOME

The dog was disconnected from the breathing system, and active cooling of the body was performed with ice packs applied to the body surface and alcohol applied to the foot pads. Cold crystalloid solutions were administered i.v.. Intermittent positive-pressure ventilation with 100% oxygen was performed to decrease end-tidal partial pressure of carbon dioxide. Because dantrolene was not available, acepromazine was administered to facilitate a decrease in body temperature. The dog recovered from malignant hyperthermia and was discharged to the owner after 13 days of hospitalization.

CLINICAL RELEVANCE

Dogs affected by genetic muscle disorders should be considered at risk for perianesthetic malignant hyperthermia, even in the absence of an RYR1 gene mutation.

Help stop teenage pregnancy! Early-age neutering in cats

PRACTICAL RELEVANCE

neutering kittens at an early age, typically between 6 and 14 weeks, has received increasing attention and gained prominence in recent years, particularly in the United States and in shelter medicine in the UK. However, in private practice it has yet to be generally endorsed.

GLOBAL IMPORTANCE

among many of the animal welfare charities, early neutering is seen as a crucial step in conquering and controlling cat overpopulation.

CLINICAL CHALLENGES

physiological differences between kittens and adult cats are very important to consider before undertaking elective early neutering. Increased sensitivity to drugs, prolongation of effects and a limited capacity for cardiovascular compensation are the principal anaesthetic concerns in kittens.

EVIDENCE BASE

the optimal age for neutering, traditionally deemed to be between 5 and 8 months, is now questioned, as short- and longer-term studies demonstrate no significant behavioural and physical advantages conferred by traditional-age neutering. Furthermore, a number of safe anaesthetic and surgical protocols have been documented that produce lower morbidity and similar mortality rates in early-age neuters compared with traditional-age neuters.