Assessment of the number of mast cells in the soft palate of dogs affected by brachycephalic obstructive airway syndrome.

BACKGROUND: Oedema is described in the soft palate of dogs affected by brachycephalic obstructive airway syndrome (BOAS). Activated mast cells (MCs) release vasoactive mediators that temporarily increase vascular permeability. METHODS: Data and caudal soft palate tissue were prospectively collected from a population of dogs undergoing surgical management of BOAS and a control group of greyhound cadavers with no previous history of respiratory signs. Histological assessment was performed to quantify the number of MCs within the lamina propria of each group. RESULTS: The mean number of MCs in the BOAS group (53 MCs/10 400× high-power fields [HPF]; standard deviation [SD] = 23) was significantly greater than that in the greyhound group (24 MCs/10 400×HPF; SD = 10). LIMITATIONS: The small size of the control group and the heterogeneous nature of the dogs in the BOAS group limit the generalisability of the findings. The use of different surgical techniques in the BOAS group may have also affected the degree of inflammation present within the samples. The cohort was not screened for concurrent disease processes that could potentially increase the number of circulating MCs. CONCLUSION: This study demonstrated a statistically significant difference between the numbers of MCs in the soft palate of brachycephalic dogs with clinically significant BOAS and the greyhound control group.

Comparison of two doses of ketamine for induction of anaesthesia in ponies undergoing field castration.

BACKGROUND: Ketamine-based total intravenous anaesthesia techniques are commonly used in equine practice for ponies requiring short procedures such as castration in field conditions. When a longer duration of recumbency than provided by the initial dose of anaesthetic agents is required, administration of supplementary 'top-up' doses of anaesthetic agents is required. Ideally, a single dose of anaesthetic agents would reliably achieve a longer duration of action whilst maintaining adequate anaesthetic, surgical and recovery qualities. AIM: This prospective, randomised and blinded study aimed to compare the UK-licensed induction dose of ketamine with an increased dose in ponies undergoing castration in field conditions. The hypothesis was that an increased dose would produce a longer duration of action without negatively affecting qualities of anaesthesia, surgical conditions and recovery. METHODS: Ponies were randomly allocated to receive ketamine at either 2.2 mg kg-1 (K2.2) or 3 mg kg-1 (K3) combined with diazepam 20 µg kg-1 following pre-anaesthetic medication with romifidine and butorphanol. Quality of anaesthesia, surgery and recovery were scored using simple descriptive scales (SDS) and timings of key events recorded. Top-up doses of ketamine 0.5 mg kg-1 were administered if anaesthesia was inadequate during surgery. Time of top-up doses and total ketamine doses were recorded. Data were analysed using Student t-tests or the Mann-Whitney U test (p < 0.05). RESULTS: Thirty-six ponies completed the study. Six ponies enrolled were excluded due to cryptorchidism or surgical complications that required deviation from the anaesthetic protocol. There were no differences in timing of events recorded, number of ponies requiring top-up ketamine, timing and frequency of top-ups or total ketamine dose. Scores for anaesthetic and recovery qualities, and surgical conditions were similar between groups. CONCLUSION: Both induction doses of ketamine provided a similar duration of action and provided conditions suitable to anaesthetise ponies undergoing castration.

Comparison of sedation in dogs: methadone or butorphanol in combination with dexmedetomidine intravenously.

OBJECTIVE: Opioids can be combined with alpha-2-adrenoreceptor agonists to sedate dogs for radiography. The study investigated the sedative effects of methadone or butorphanol in combination with dexmedetomidine in dogs undergoing stifle radiography. STUDY DESIGN: Prospective, blinded, randomized, clinical trial. ANIMALS: A total of 52 healthy dogs requiring sedation for stifle radiography were enrolled. METHODS: Dogs were assessed for body condition [body condition score (BCS)], temperament and pain using the short-form composite measure pain scale (CMPS-SF). Dogs were randomized to be administered methadone 0.2 mg kg-1 (group M) or butorphanol 0.2 mg kg-1 (group B) in combination with dexmedetomidine 2 µg kg-1 intravenously (IV). Sedation was assessed using a numerical descriptive score, from 0 (no sedation) to 11 (greatest sedation), before administration and at 5, 10, 15 and 20 minutes by one blinded assessor. Onset signs of sedation, pulse rate and respiratory rates were recorded. Positioning for radiography was attempted at 5 minutes. If positioning was not possible at 10 minutes, dexmedetomidine 2 µg kg-1 was administered IV, with the dog recorded as failed sedation and withdrawn from further analysis. Following normality testing, data were assessed using Student t test, Mann-Whitney test, two-way analysis of variance and Fisher's exact test for failed sedations. Results are reported as mean ± standard deviation. Statistical significance was set at p < 0.05. RESULTS: Groups were similar for sex, age, weight, BCS, temperament and CMPS-SF. The onset of sedation was faster in group B than in group M (p = 0.048). Sedation scores were higher in group B at 10 minutes compared to group M (p = 0.003). Failed sedation occurred in 12 dogs in group M and two in group B (p = 0.002). Pulse rates were lower in group B at 5 and 10 minutes (p = 0.002). CONCLUSION AND CLINICAL RELEVANCE: IV butorphanol provides more effective sedation at 10 minutes than methadone, in combination with dexmedetomidine.

Comparison of intramuscular butorphanol and buprenorphine combined with dexmedetomidine for sedation in cats.

Objectives The objective of this study was to compare the sedative effect of butorphanol-dexmedetomidine with buprenorphine-dexmedetomidine following intramuscular (IM) administration in cats. Methods Using a prospective, randomised, blinded design, 40 client-owned adult cats were assigned to receive IM dexmedetomidine (10 µg/kg) combined with either butorphanol (0.4 mg/kg) ('BUT' group) or buprenorphine (20 µg/kg) ('BUP' group). Sedation was scored using a previously published multidimensional composite scale before administration (T0) and 5, 10, 15 and 20 mins afterwards (T5, T10, T15 and T20, respectively). Alfaxalone (1.5 mg/kg) was administered IM at T20 if the cat was not deemed adequately sedated to place an intravenous catheter. Adverse events were recorded. Friedman two-way ANOVA analysed sedation scores within groups. Mann-Whitney Rank Sum test compared sedation scores between groups; Fisher's exact test analysed the frequency of alfaxalone administration and adverse events. P <0.05 was considered statistically significant. Results Sedation scores between groups were similar at baseline, but at T5, T10, T15 and T20 scores were higher in the BUT group ( P <0.01). Within both groups, sedation scores changed over time and the highest sedation scores were reached at T10. Requirement for additional sedation was similar between groups: two cats in the BUT group and five cats in the BUP group. One cat and 11 cats vomited ( P = 0.002) in the BUT and BUP groups, respectively. No other adverse events were recorded. Conclusions and relevance At these doses, IM buprenorphine-dexmedetomidine provides inferior sedation and a higher incidence of vomiting than butorphanol-dexmedetomidine in cats. Butorphanol-dexmedetomidine may be preferred for feline sedation, especially where vomiting is contraindicated.

Diabetes mellitus does not affect the neuromuscular blocking action of atracurium in dogs.

OBJECTIVE: To compare the duration of action of atracurium in diabetic and nondiabetic dogs. STUDY DESIGN: Prospective, blinded, clinical study. ANIMALS: A total of 26 diabetic and 29 nondiabetic dogs. METHODS: Following preanaesthetic medication and intravenous (IV) propofol induction, anaesthesia was maintained with isoflurane in oxygen. Atracurium 0.2 mg kg-1 IV was administered to provide neuromuscular blockade (NMB) and the responses (twitches; T) to train-of-four nerve stimulation were recorded by palpation and electromyography (EMG). Time to onset of NMB (from atracurium administration to loss of T4 by EMG), duration of NMB (to return of T1 by EMG) and also times to loss and return of T2-T4 were recorded. Heart rate (HR), mean arterial pressure, end-tidal isoflurane (Fe'Iso), end-tidal CO2 concentrations and oesophageal temperature were recorded at onset of NMB and when T1EMG returned. Groups were compared using t tests and Mann-Whitney U tests (p<0.05). RESULTS: Diabetic dogs were older (9.9±0.3 compared with 6.8±0.7 years, p=0.0003). Group parameters were similar at onset and offset of NMB apart from HR at offset, which was higher for diabetics compared to nondiabetics (114±4 compared with 100±3 beats minute-1, respectively, p=0.004), Fe'Iso was higher in the diabetic group at onset (1.3±0.03% compared with 1.2±0.04%, p=0.026) and offset (1.4±0.03% compared with 1.3±0.03%, p=0.007), and temperature was higher for diabetics at onset (37.5±0.1 °C compared with 37.0±0.2 °C, p=0.012) and offset (37.5±0.1 °C compared with 36.9±0.2 °C, p=0.004). The duration of action of atracurium(tactile) and atracurium(EMG) were similar for both groups. CONCLUSIONS AND CLINICAL RELEVANCE: The duration of action of atracurium was similar in diabetic and nondiabetic dogs as indicated by tactile and EMG monitoring.

Intramuscular injection of alfaxalone in combination with butorphanol for sedation in cats.

OBJECTIVE: To assess quality of sedation following intramuscular (IM) injection of two doses of alfaxalone in combination with butorphanol in cats. STUDY DESIGN: Prospective, randomized, 'blinded' clinical study. ANIMALS: A total of 38 cats undergoing diagnostic imaging or noninvasive procedures. METHODS: Cats were allocated randomly to be administered butorphanol 0.2 mg kg-1 combined with alfaxalone 2 mg kg-1 (group AB2) or 5 mg kg-1 (group AB5) IM. If sedation was inadequate, alfaxalone 2 mg kg-1 IM was administered and cats were excluded from further analysis. Temperament [1 (friendly) to 5 (aggressive)], response to injection, sedation score at 2, 6, 8, 15, 20, 30, 40, 50 and 60 minutes, overall sedation quality scored after data collection [1 (excellent) to 4 (inadequate)] and recovery quality were assessed. Heart rate (HR), respiratory rate (fR) and arterial haemoglobin saturation (SpO2) were recorded every 5 minutes. Groups were compared using t tests and Mann-Whitney U tests. Sedation was analysed using two-way anova, and additional alfaxalone using Fisher's exact test (p < 0.05). RESULTS: Groups were similar for sex, age, body mass and response to injection. Temperament score was lower in group AB2 [2 (1-3)] compared to AB5 [3 (1-5)] (p = 0.006). Group AB5 had better sedation at 6, 8, 20 and 30 minutes and overall sedation quality was better in AB5 [1 (1-3)], compared to AB2 [3 (1-4)] (p = 0.0001). Additional alfaxalone was required for 11 cats in AB2 and two in AB5 (p = 0.005). Recovery quality, HR, fR and SpO2 were similar. Seven cats required oxygen supplementation. Complete recovery times were shorter in AB2 (81.8 ± 24.3 versus 126.6 ± 33.3 minutes; p = 0.009). Twitching was the most common adverse event. CONCLUSIONS AND CLINICAL RELEVANCE: In combination with butorphanol, IM alfaxalone at 5 mg kg-1 provided better quality sedation than 2 mg kg-1. Monitoring of SpO2 is recommended.

Effect of prewarming on the body temperature of small dogs undergoing inhalation anesthesia.

OBJECTIVE: To investigate whether prewarming affects body temperature of small dogs (weighing < 10 kg [22 lb]) undergoing inhalation anesthesia. DESIGN: Prospective, randomized, blinded clinical trial. Animals: 20 dogs weighing < 10 kg with American Society of Anesthesiologists physical status I or II. PROCEDURES: Baseline rectal temperature was recorded. Before IM administration of buprenorphine hydrochloride and acepromazine maleate, dogs were randomly assigned to be placed in a pediatric incubator at 33°C (91.4°F) for approximately 30 to 60 minutes (prewarming group) or to receive no prewarming (control group); subsequently, dogs underwent inhalation anesthesia with isoflurane in oxygen. Rectal, esophageal, and ambient temperatures were measured every 5 minutes from induction of anesthesia (IOA) for > 1 hour by an observer who was unaware of treatment. If a dog became hypothermic (esophageal temperature < 36°C [96.8°F]), it was withdrawn from the study. Variables of interest relating to dogs, anesthesia, temperatures, hypothermia, and study withdrawal were compared between groups. RESULTS: 1 dog was excluded from the prewarming group after becoming excessively excited in the incubator. Between groups, age, weight, body condition score, degree of preanesthesia sedation, interval from sedation to IOA, duration of anesthesia, baseline rectal temperature, rectal temperatures immediately prior to IOA, esophageal temperature following IOA, ambient temperature during the first 70 minutes of anesthesia, esophageal or rectal temperature during the first 90 minutes of anesthesia, and incidence of hypothermia and study withdrawal (5 dogs/group) did not differ significantly. CONCLUSIONS AND CLINICAL RELEVANCE: Prewarming in an incubator prior to IOA failed to improve or maintain body temperature of dogs weighing < 10 kg during inhalation anesthesia.

Analgesic effects of maxillary and inferior alveolar nerve blocks in cats undergoing dental extractions.

The aim of this study was to evaluate the analgesic effects of maxillary and/or inferior alveolar nerve blocks with lidocaine and bupivacaine in cats undergoing dental extractions. Twenty-nine cats were enrolled. Using an adapted composite pain scale, cats were pain scored before the dental procedure and 30 mins, and 1, 2 and 4 h after isoflurane disconnection. Cats were sedated with buprenorphine (20 µg/kg), medetomidine (10 µg/kg) and acepromazine (20 µg/kg) intramuscularly. Anaesthesia was induced using alfaxalone (1-2 mg/kg) intravenously and maintained with isoflurane in oxygen. Each cat was randomly assigned to receive maxillary and/or inferior alveolar nerve blocks or no nerve blocks prior to dental extractions. Each nerve block was performed using lidocaine (0.25 mg/kg) and bupivacaine (0.25 mg/kg). Heart rate, systolic arterial blood pressure, respiratory rate, end tidal carbon dioxide and isoflurane vaporiser settings were recorded 5 mins before and after the dental extractions, and the difference calculated. Group mean differences (mean ± SD) for heart rate (-9.7 ± 10.6 vs 7.6 ± 9.5 beats/min [nerve block vs control group, respectively], P <0.0001), systolic arterial blood pressure (-10.33 ± 18.44 vs 5.21 ± 15.23 mmHg, P = 0.02) and vaporiser settings (-0.2 ± 0.2 vs 0.1 ± 0.4, P = 0.023) were significantly different between groups. The control group had higher postoperative pain scores (median [interquartile range]) at 2 h (3 [1.75-4.00] vs 1 [0-2], P = 0.008) and 4 h (4 [2-6] vs 2 [1-2], P = 0.006) after the dental extractions. Maxillary and inferior alveolar nerve blocks with lidocaine and bupivacaine administered prior to dental extractions resulted in a reduction in heart rate and blood pressure while allowing for a reduction in isoflurane. Cats receiving nerve blocks had lower postoperative pain scores than the group without nerve blocks.

Analgesia for pelvic limb surgery. A review of peripheral nerve blocks and the extradural technique.

OBJECTIVES: To describe the anatomy and approaches reported for peripheral nerve blockade (PNB) of the pelvic limb in dogs and cats and to consider the role of PNB in relation to the extradural technique. DATABASES USED: This review was conducted using the terms 'nerve block', 'extradural' 'dog' and 'cat' entered into Pubmed and Google. Results were filtered manually to narrow the field to pelvic limb nerve blocks. The reference lists of retrieved papers were scrutinized to identify further studies for inclusion. CONCLUSIONS: Successful PNB techniques require thorough anatomical knowledge for the establishment of reliable landmarks, puncture sites, the direction and depth of needle insertion, and relevant structures to be avoided. To date, clinical evaluations have been made in subjects undergoing stifle surgery where the sciatic nerve has been blocked in combination with various approaches to the femoral nerve. Currently the bulk of literature examines new approaches to these nerves and each of these is described. To date there are no veterinary studies directly comparing one approach versus another, and therefore one is unable to draw conclusions of superiority. The role of PNB's versus the extradural technique is discussed.

Comparison of propofol with ketofol, a propofol-ketamine admixture, for induction of anaesthesia in healthy dogs.

OBJECTIVE: To compare anaesthetic induction in healthy dogs using propofol or ketofol (a propofol-ketamine mixture). STUDY DESIGN: Prospective, randomized, controlled, 'blinded' study. ANIMALS: Seventy healthy dogs (33 males and 37 females), aged 6-157 months and weighing 4-48 kg. METHODS: Following premedication, either propofol (10 mg mL(-1)) or ketofol (9 mg propofol and 9 mg ketamine mL(-1)) was titrated intravenously until laryngoscopy and tracheal intubation were possible. Pulse rate (PR), respiratory rate (f(R)) and arterial blood pressure (ABP) were compared to post-premedication values and time to first breath (TTFB) recorded. Sedation quality, tracheal intubation and anaesthetic induction were scored by an observer who was unaware of treatment group. Mann-Whitney or t-tests were performed and significance set at p ≤ 0.05. RESULTS: Induction mixture volume (mean ± SD) was lower for ketofol (0.2 ± 0.1 mL kg(-1)) than propofol (0.4 ± 0.1 mL kg(-1)) (p < 0.001). PR increased following ketofol (by 35 ± 20 beats minute(-1)) but not consistently following propofol (4 ± 16 beats minute(-1)) (p < 0.001). Ketofol administration was associated with a higher mean arterial blood pressure (MAP) (82 ± 10 mmHg) than propofol (77 ± 11) (p = 0.05). TTFB was similar, but ketofol use resulted in a greater decrease in f(R) (median (range): ketofol -32 (-158 to 0) propofol -24 (-187 to 2) breaths minute(-1)) (p < 0.001). Sedation was similar between groups. Tracheal intubation and induction qualities were better with ketofol than propofol (p = 0.04 and 0.02 respectively). CONCLUSION AND CLINICAL RELEVANCE: Induction of anaesthesia with ketofol resulted in higher PR and MAP than when propofol was used, but lower f(R). Quality of induction and tracheal intubation were consistently good with ketofol, but more variable when using propofol.

Preliminary investigations into the analgesic effects of topical ocular 1% morphine solution in dogs and cats.

OBJECTIVE: To perform preliminary evaluations into the ocular analgesic effect of topical 1% morphine in a clinical setting and to determine onset, duration and complications. STUDY DESIGN: Prospective, randomised, blinded clinical study. ANIMALS: Twenty six dogs and seventeen cats, all client-owned. METHODS: Dogs and cats with corneal ulceration requiring medical treatment or corneal conditions requiring surgery were included and randomly assigned to receive one drop of topical morphine (group M) or base solution (group B). Recordings were made prior to application and at 5, 10, 20, 30, 40, 50 and 60 minutes, then 2, 3, 4, 5 and 6 hours. Corneal aesthesiometry, blink rates and scores for blepharospasm (BLEPH), conjunctival hyperaemia (CH) and lacrimation (LAC) were recorded. Statistical analyses used anova, t-tests and Mann-Whitney U tests as relevant. RESULTS: No significant effect of treatment group on any recordings was found at any time point in either dogs or cats. Adverse effects of increased BLEPH, CH or blink rate were observed in six animals (three cats from group M and three dogs from group B), occurring within 5 minutes of drop application and lasting for between 10 minutes and 6 hours. CONCLUSIONS AND CLINICAL RELEVANCE: Topical ocular morphine showed no measurable analgesic effect against corneal pain in dogs and cats.

Thoracic epidural catheter placement using a paramedian approach with cephalad angulation in three dogs.

OBJECTIVE: To describe a technique for insertion of a thoracic epidural catheter. STUDY DESIGN: Clinical report. ANIMALS: Dogs (n = 3) undergoing thoracic wall resection and thoracotomy. METHODS: A paramedian approach with cephalic angulation was used to place a 24-g epidural catheter in 3 dogs. Dogs 1 and 2 had left caudal thoracic wall resection and dog 3 had left thoracotomy. In dog 1, the epidural catheter was inserted at L2-L3 intervertebral space and the tip of the catheter advanced to the level of T13 vertebral body. In dog 2, the epidural catheter was inserted at T12-T13 intervertebral space and the tip of the catheter was advanced to the level of T8 vertebral body. In dog 3, the epidural catheter was inserted at T13-L1 intervertebral space and its tip advanced until reaching the vertebral body of T10. All dogs were administered a combination of bupivacaine and morphine through the epidural catheter to provide intra- and postoperative analgesia. RESULTS: The peridural space was identified and the tip of the catheter was positioned where intended in all dogs. Dog 1 developed transient Horner's syndrome and dog 3 required intraoperative fentanyl during the first part of the procedure. CONCLUSION: Paramedian approach with cephalad angulation is a suitable technique to place thoracic epidural catheters in dogs.

Diabetes mellitus affects the duration of action of vecuronium in dogs.

OBJECTIVE: To compare the duration of action of vecuronium in diabetic dogs with a control group. STUDY DESIGN: Prospective clinical study. ANIMALS: Forty client-owned diabetic (n = 20) and non-diabetic dogs. METHODS: Dogs were considered free from other concurrent disease based on clinical examination and laboratory data. After pre-anaesthetic medication with acepromazine and methadone, anaesthesia was induced with intravenous (IV) propofol and maintained with isoflurane-nitrous oxide in oxygen. Neuromuscular blockade (NMB) was achieved with vecuronium, 0.1 mg kg(-1) IV and its effects recorded by palpation (pelvic limb digital extension) and electromyography (m. tibialis cranialis) of responses (twitches; T) to repeated train-of-four (TOF) nerve stimulation. Time to onset of NMB was the period between vecuronium injection and loss of fourth twitch (T4) in the TOF pattern recorded by EMG and palpation. Duration of NMB was defined as the time from drug administration to return of T1 by palpation (T1(tactile) ) and EMG (T1(EMG) ). Times to return of T2-4 were also recorded. Time from induction of anaesthesia to vecuronium injection was recorded. Heart rate, non-invasive mean arterial pressure, body temperature, end-tidal isoflurane and end-tidal CO(2) concentrations were recorded at onset of NMB and when T1(EMG) returned. Loss and return of palpable and EMG responses for diabetic and non-diabetic dogs were compared using t-tests and Mann Whitney U-tests. RESULTS: There were significant (p < 0.05) differences between diabetic and non-diabetic dogs for the return of all four palpable and EMG responses. Times (mean ± SD) for return of T1(tactile) were 13.2 ± 3.5 and 16.9 ± 4.2 minutes in diabetic and non-diabetic dogs respectively. There were no differences between diabetic and non-diabetic dogs in the time to onset of vecuronium with EMG or tactile monitoring. CONCLUSIONS AND CLINICAL RELEVANCE: The duration of action of vecuronium was shorter in diabetic dogs as indicated by both tactile and EMG monitoring.

Comparison of pain on injection during induction of anaesthesia with alfaxalone and two formulations of propofol in dogs.

OBJECTIVE: To compare the incidence of pain during injection of three intravenous induction agents in dogs. STUDY DESIGN: Prospective, crossover, randomized, blinded, clinical study. ANIMALS: Thirty dogs requiring anaesthesia for radiotherapy. METHODS: Dogs were anaesthetized on three occasions at weekly intervals. An IV cephalic catheter was placed, flushed with saline and alfentanil 0.01 mg kg(-1) and atropine 0.02 mg kg(-1) administered. After 30 seconds either: propofol lipid macroemulsion (Drug(P) ), propofol lipid-free microemulsion (Drug(PC) ) or alfaxalone (Drug(A)) was administered over 60 seconds. Each induction agent was administered once to each dog. Induction was recorded by video and reviewed by an assessor, unaware of treatment. Catheter placement (number of attempts, site, size and recent vein use) were recorded. Behavioural changes associated with pain or excitation, were recorded. Severity of pain on injection was recorded (mild, moderate or severe pain). Incidence of pain was analysed using logistic regression, excitation using McNemar's test (p < 0.05) and association of pain with induction agent and catheter placement using the Akaike Information Criterion (AIC). RESULTS: No dogs reacted to saline or Drug(A,) thus Drug(A) was excluded from analysis. Pain on injection occurred in six dogs (20%) with Drug(PC) and one dog (3.3%) with Drug(P). Pain was severe in four dogs with Drug(PC). Drug(P) resulted in a trend for reduced risk of pain compared to Drug(PC) (p = 0.076, odds ratio [confidence intervals] 0.14 [0.027-0.86]). Both propofol formulations resulted in greater risk of excitation than Drug(A) (p = 0.0003, odds ratio 4.5 [1.86-10.90]). Induction agent was associated with pain, whilst catheter placement was not. One dog developed facial oedema and one other dog skin necrosis adjacent to the catheter site following Drug(PC.) The study was terminated early due to ethical concerns about the severity of reactions with Drug(PC). conclusions and clinical relevance: Drug(PC) was associated with clinically relevant moderate to severe pain behaviour whilst Drug(A) and Drug(P) were not.

Immersion and branchial/transcutaneous irrigation anaesthesia with alfaxalone in a Mexican axolotl.

INTRODUCTION: Immersion anaesthetic techniques are commonly used in amphibian species. Alfaxalone has been reported as an immersion anaesthetic in fish but not amphibians. CASE HISTORY AND EXAMINATION: A Mexican 56 g axolotl was presented with a 3-day history of anorexia. Anaesthesia was required for the surgical retrieval of two gastric foreign bodies. Prior to anaesthesia, on visual inspection the axolotl was bright and active. Branchial and gular respiratory movements occurred at approximately 24 respirations minute(-1) and heart rate was approximately 52 beats minute(-1) . MANAGEMENT: The axolotl was exposed to increasing concentrations (up to 5 mg L(-1) ) of alfaxalone (Alfaxan; Vetóquinol, UK) in a water bath. After becoming sedated the axolotl was removed from the water bath. Anaesthesia was induced and maintained with alfaxalone (5 mg L(-1) ) via continuous irrigation of the gills (branchial) and skin (cutaneous) with additional 30 µL drops of alfaxalone (10 mg mL(-1) ) administered branchially as required. Endoscopy and surgery were performed to remove two gastric foreign bodies. Branchial and gular respiratory movements persisted at what was considered an appropriate anaesthetic depth. Anaesthetic depth could be rapidly deepened by branchial irrigation of alfaxalone solutions and lightened by irrigation using fresh water. Anaesthesia lasted approximately 1 hour and recovery was rapid (within 15 minutes). Recovery was assisted through branchial and cutaneous irrigation with fresh water. FOLLOW-UP: No obvious adverse effects of anaesthesia were observed immediately post-anaesthesia or, according to the owner, in the following week. Conclusions Axolotls can be anaesthetized using alfaxalone administered via immersion and branchial/transcutaneous irrigation offering an alternative technique for anaesthetising axolotls for clinical and research purposes.

Arrhythmias and transient changes in cardiac function after topical administration of one drop of phenylephrine 10% in an adult cat undergoing conjunctival graft.

HISTORY: A 2-year-old, entire female, Somali cat weighing 3.8 kg was admitted for a conjunctival graft on the right eye, for treatment of an acute descemetocele. Medetomidine 4.2 µg kg(-1) and methadone 0.2 mg kg(-1) were administered by intramuscular injection as preanaesthetic medication. Anaesthesia was induced using diazepam 0.26 mg kg(-1) and propofol 4 mg kg(-1) administered by intravenous (i.v.) injection. Following endotracheal intubation, anaesthesia was maintained with isoflurane delivered in oxygen (1 L minute(-1)) and nitrous oxide (2 L minute(-1)) via a non-rebreathing system. Twenty minutes after induction of anaesthesia, one drop of a 10% phenylephrine hydrochloride solution was administered topically to the right eye. PHYSICAL EXAMINATION: After phenylephrine administration, a decrease in heart rate (from 95 to 80 beats minute(-1)) and an increase in arterial blood pressure occurred. The pulse then became difficult to palpate manually and multifocal ventricular premature contractions were observed on the electrocardiogram. MANAGEMENT: Nitrous oxide was discontinued and the isoflurane vaporizer setting was decreased from 1.5% to 0.5%. Lidocaine 1 mg kg(-1) i.v. was administered, this resulted in ventricular bigeminy. The quality of the femoral pulse improved and was regular in rhythm and character. Surgery was completed as fast as possible. The bigeminy progressively disappeared and before disconnecting the cat from the breathing system, there was a normal sinus rhythm with a heart rate of 85 beats minute(-1). FOLLOW-UP: Echocardiography was performed during recovery and showed mitral and aortic valve insufficiency and dilation of the left ventricle, suggesting a reduction in systolic function. Echocardiography was repeated the following day and was normal. CONCLUSIONS: In order to diminish the potential for cardiovascular sequelae associated with systemic absorption of ocular phenylephrine, less concentrated solutions, smaller drop size or different instillation techniques should be considered for topical use in small patients.

Comparison of ketamine and alfaxalone for induction and maintenance of anaesthesia in ponies undergoing castration.

OBJECTIVE: To compare alfaxalone with ketamine for total intravenous anaesthesia in ponies undergoing castration. STUDY DESIGN: Prospective, randomised, blinded clinical study. ANIMALS: Forty-two, 12-month-old Welsh Mountain ponies. METHODS: Ponies were assigned randomly to receive ketamine or alfaxalone. After administration of romifidine 100 µg kg(-1) and butorphanol 50 µg kg(-1) intravenously (IV), sedation and response to tactile stimulation were scored. If sedation was insufficient, romifidine 30 µg kg(-1) was administered IV. Anaesthesia was induced with ketamine 2.2 mg kg(-1) or alfaxalone 1 mg kg(-1) , both in combination with diazepam 20 µg kg(-1) IV. Time from end of injection to lateral recumbency was recorded. Simple descriptive scores were used to score quality of induction, surgical conditions and recovery. Ketamine 0.5 mg kg(-1) or alfaxalone 0.2 mg kg(-1) were administered if movement was observed. Times to first head lift, sternal recumbency and standing, and number of attempts needed were recorded. All scores were performed by the same observer, unaware of treatment. Normally distributed data were compared using t-test and non-normally distributed data with Mann-Whitney test. Level of significance was set at p<0.05. RESULTS: Three ponies needed additional sedation. Mean induction times were 30 ± 6 and 18 ± 4 seconds following ketamine and alfaxalone respectively (p<0.0001). Additional doses were required by four ponies given ketamine and seven given alfaxalone. Sedation, induction and surgical scores were similar for both groups. Recovery scores (scale of 1-4 with 1 best) differed statistically between groups [ketamine group, median 1 (1-2); alfaxalone group 1.5 (1-4) (p=0.04)]. No differences in anaesthesia time or times taken from end of surgery to head lift, sternal recumbency and standing were detected. CONCLUSION AND CLINICAL RELEVANCE: Induction times following alfaxalone were shorter than following ketamine. Both anaesthetic agents provided acceptable quality of anaesthesia for castration.

Suspected anaphylactoid reaction following intravenous administration of a gadolinium-based contrast agent in three dogs undergoing magnetic resonance imaging.

OBSERVATIONS: Anaphylactoid reactions were suspected in three dogs following the intravenous administration of the contrast agent gadobenate dimeglumine 0.05 mmol kg(-1) (Multihance). Case 1: A 14 kg 6-year-old atopic female dog was anaesthetized for brain magnetic resonance imaging (MRI). All monitored parameters remained stable during the procedure. Fifteen minutes following MR completion; facial, peri-orbital and sublingual oedema were noted. Resolution of the oedema was rapid and uneventful following treatment of clinical signs over 2 hours. Case 2: A 16 kg 10-month-old male dog was anaesthetized for brain and neck MRI. Ten minutes after MR contrast intravenous (IV) injection; heart rate (HR) increased (85-120 beats minute(-1)), mean arterial blood pressure (MAP) decreased (from 70 to 43 mmHg) and PE'CO(2) decreased (from 4.66 to 3.19 kPa). Labial, periorbital and lingual oedema were noted. Clinical signs responded to fluid bolus administration. The dog vomited in recovery but oedema resolved within one hour. Case 3: A 34 kg 2-year-old atopic male dog was anaesthetized for head MRI. Within 5 minutes of MR contrast IV injection; the dog suffered severe cardiovascular collapse. MRI procedure was aborted and administration of anaesthetics discontinued. Aggressive IV fluid resuscitation and IV epinephrine administration were necessary to re-establish cardiovascular stability. Some periorbital and labial oedema were noted. The dog vomited once and had soft faeces but made a complete recovery. CONCLUSIONS: The administration of contrast medium may result in mild to severe anaphylactoid reactions.