The effect of neuraxial morphine on postoperative pain in dogs after extrahepatic portosystemic shunt attenuation.

OBJECTIVE: To investigate the analgesic effect of epidural morphine after surgical extrahepatic portosystemic shunt (EHPSS) attenuation. STUDY DESIGN: Randomized clinical trial. ANIMALS: A total of 20 dogs with a congenital EHPSS. METHODS: Dogs were randomly allocated to be given either a single epidural dose of 0.2 mg kg-1 preservative-free morphine (group M) or not (group C) before surgery. All dogs were administered 0.3 mg kg-1 methadone intravenously (IV) as preanaesthetic medication. Pain scores were determined every 2 hours for the first 24 hours postoperatively using the short-form Glasgow Composite Measure Pain Scale (GCMPS-SF). Dogs with a GCMPS-SF pain score >4/20 or >5/24 received 0.1 mg kg-1 methadone IV as rescue analgesia and were reassessed 30 minutes later. If more than three doses of methadone were administered in a 2 hour period, alternative pain relief was provided and a treatment failure recorded. The GCMPS-SF pain scores and number of rescue analgesia injections were analysed over 24 hours. The last observation carried forward method was applied in case of treatment failure. Food consumption and time to first urination were recorded. Data were analysed using a Mann-Whitney U test and presented as median (minimum-maximum range), with significance set at p < 0.05. RESULTS: Group M showed lower GCMPS-SF pain scores [15 (11-41) versus 31 (11-86); p = 0.023] and lower postoperative methadone requirements [0 (0-0.2) versus 0.25 (0-0.5) mg kg-1; p = 0.029] than group C. There were three treatment failures in group C only. Food consumption and time to first urination did not differ between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Epidural morphine reduced the requirement for postoperative analgesia in this study population.

The Use of Alfaxalone in Quaker Parrots (Myiopsitta monachus).

Alfaxalone is a neurosteroid anesthetic that acts on gamma-aminobutyric acid alpha-receptors. The objective of this study was to evaluate the clinical safety and efficacy of alfaxalone (Alfaxan CD). Due to observed hyperexcitability in the subject animals when alfaxalone was the only drug used during the initial trials, premedication with midazolam was also evaluated during the final study. Ten adult Quaker parrots (Myiopsitta monachus) were assigned to 3 groups: 1) low-dose alfaxalone 10 mg/kg (LD), 2) high-dose alfaxalone 25 mg/kg (HD), and 3) alfaxalone 10 mg/ kg with midazolam 1 mg/kg premedication (AM), administered intramuscularly. Induction time, sedation quality, duration of action, and vital parameters, including heart rate, respiratory rate, and temperature, were recorded. All protocols achieved adequate sedation; however, muscle tremors and hyperexcitation were variable. The LD group had a significantly longer mean ± SD induction time (13.5 ± 4.5 minutes) as compared to the HD (6.0 ± 1.3 minutes, P = .002) and AM (6.5 ± 2.9 minutes, P = .006) groups, while recovery time was significantly longer in the HD group (86.2 ± 13.4 minutes) than the LD group (44.4 ± 10.8 minutes, P < .001). Midazolam premedication resulted in reduction of both muscle tremors and hyperexcitation associated with alfaxalone administration, but the recovery time was significantly longer (103.5 ± 15.1 minutes, P < .001) than for the LD group. Alfaxalone as a sole agent resulted in muscle tremors and hyperexcitation during induction, which was attenuated by premedication with midazolam. Further investigation is warranted to characterize the effects of alfaxalone and drugs used to premedicate Quaker parrots.

Evaluation of two different radiotherapy anaesthetic protocols for dogs: a randomized clinical crossover trial.

OBJECTIVES: To describe alfentanil-propofol admixture for induction of anaesthesia for canine radiotherapy and compare it to alfentanil-atropine followed by propofol induction in terms of heart rate (HR), mean arterial pressure (MAP), recovery duration and quality. STUDY DESIGN: Prospective, masked, randomized clinical crossover trial. ANIMALS: A group of 40 client-owned dogs anaesthetized from October 2017 to June 2018. METHODS: Dogs were randomly assigned to be administered one of two protocols. For both protocols, IV preanaesthetic medication was given 30 seconds before rapid IV administration of a set volume of induction agent, with further induction agent administered as needed to permit intubation. For protocol ADMIX, the preanaesthetic medication was 0.04 mL kg-1 0.9% sodium chloride and the induction agent was 0.2 mL kg-1 propofol-alfentanil admixture. For protocol ATRO, the preanaesthetic medication was 10 µg kg-1 alfentanil with 12 µg kg-1 atropine (0.04 mL kg-1 total volume) and the induction agent was 0.2 mL kg-1 propofol. Anaesthesia was maintained with sevoflurane. Cardiorespiratory variables, agitation, hypotension, or inadequate depth of anaesthesia requiring supplemental boluses of propofol or increased vaporizer settings were recorded. Time to extubation, sternal recumbency and walking was noted. Videos were recorded for recovery quality scoring. Owner questionnaires gave feedback about recoveries at home. The other protocol was administered for the next radiotherapy session. RESULTS: The only significantly different variable between protocols was mean HR during anaesthesia, which was lower in ADMIX (p < 0.001). Hypotension was recorded in seven (17.5%) dogs in ATRO and three (7.5%) in ADMIX, with an association (p < 0.005) between ATRO and hypotension. Owners reported animals recovered 'normal' behaviour and appetite by the next morning. CONCLUSIONS AND CLINICAL RELEVANCE: Both protocols were acceptable for dogs undergoing radiotherapy, with minimal differences in anaesthetic quality, recovery duration and quality. Although MAP did not differ overall, the incidence of hypotension was higher in ATRO.

The analgesic effects of buprenorphine (Vetergesic or Simbadol) in combination with carprofen in dogs undergoing ovariohysterectomy: a randomized, blinded, clinical trial.

BACKGROUND: Buprenorphine is a potent lipophilic opioid analgesic that is largely used in the multimodal treatment of acute pain. Simbadol (buprenorphine hydrochloride) is the first and only FDA-approved high-concentration formulation of buprenorphine for use in cats. The aim of this study was to evaluate the analgesic efficacy of carprofen in combination with one of two commercial formulations of buprenorphine (Simbadol and Vetergesic, 1.8 mg/mL and 0.3 mg/mL, respectively) in dogs undergoing ovariohysterectomy. Twenty-four dogs were included in a randomized, prospective, controlled, clinical trial. Patients were randomly divided into 2 groups as follows. Dogs were premedicated with acepromazine (0.02 mg/kg) and either 0.02 mg/kg of Vetergesic or Simbadol intramuscularly (Vetergesic group - VG; Simbadol group - SG, respectively; n = 12/group). General anesthesia was induced with propofol and maintained with isoflurane in 100% oxygen. Carprofen (4.4 mg/kg SC) was administered after induction of anesthesia. Heart rate, respiratory rate, blood pressure, pulse oximetry, pain scores using the Glasgow Composite Pain Scale Short Form (CMPS-SF), sedation scores using a dynamic interactive visual analogue scale and adverse events were evaluated before and after ovariohysterectomy by an observer who was unaware of treatment administration. If CMPS-SF scores were ≥ 5/20, dogs were administered rescue analgesia (morphine 0.5 mg/kg IM). Statistical analysis was performed using linear mixed models and Fisher's exact test (p < 0.05). RESULTS: Pain and sedation scores and physiological parameters were not significantly different between treatments. Three dogs in VG (25%) and none in SG (0%) required rescue analgesia (p = 0.109). Adverse effects (i.e. vomiting and melena) were observed in two dogs in SG and were thought to be related to stress and/or nonsteroidal anti-inflammatory drug toxicity. CONCLUSIONS: The administration of buprenorphine with carprofen preoperatively provided adequate postoperative analgesia for the majority of dogs undergoing OVH without serious adverse events. Prevalence of rescue analgesia was not significantly different between groups; however, it could be clinically relevant and explained by a type II error (i.e. small sample size). Future studies are necessary to determine if analgesic efficacy after Simbadol and Vetergesic is related to individual variability or pharmacokinetic differences.

Effects of buprenorphine, butorphanol or tramadol premedication on anaesthetic induction with alfaxalone in common marmosets (Callithrix jacchus).

OBJECTIVE: To investigate the clinical and physiological effects of intravenous (IV) alfaxalone alone or in combination with buprenorphine, butorphanol or tramadol premedication in marmosets. STUDY DESIGN: Prospective, randomized, blinded, crossover design. ANIMALS: Nine healthy marmosets (391 ± 48 g, 3.7 ± 2.2 years old). METHODS: Meloxicam 0.20 mg kg-1 subcutaneously, atropine 0.05 mg kg-1 intramuscularly (IM) and either buprenorphine 20 µg kg-1 IM (BUP-A), butorphanol 0.2 mg kg-1 IM (BUT-A), tramadol 1.5 mg kg-1 IM (TRA-A) or no additional drug (control) were administered to all marmosets as premedication. After 1 hour, anaesthesia was induced with 16 mg kg-1 alfaxalone IV. All animals received all protocols. The order of protocol allocation was randomized with a minimum 28 day wash-out period. During anaesthesia, respiratory and pulse rates, rectal temperature, haemoglobin oxygen saturation, arterial blood pressure, palpebral and pedal withdrawal reflexes and degree of muscle relaxation were assessed and recorded every 5 minutes. Quality of induction and recovery were assessed. Duration of induction, immobilization and recovery were recorded. Blood samples were analysed for aspartate aminotransferase, creatine kinase and lactate dehydrogenase concentrations. The protocols were compared using paired t tests, Wilcoxon's signed-rank test with Bonferroni's corrections and linear mixed effect models where appropriate. RESULTS: Out of nine animals, apnoea was noted in eight animals administered protocol BUP-A and two animals administered protocol BUT-A. With TRA-A and control protocols, apnoea was not observed. No other significant differences in any of the parameters were found; however, low arterial blood pressures and hypoxia occurred in TRA-A. CONCLUSIONS AND CLINICAL RELEVANCE: Our study employing different premedications suggests that the previously published dose of 16 mg kg-1 alfaxalone is too high when used with premedication because we found a high incidence of complications including apnoea (BUP-A), hypotension and hypoxaemia (TRA-A). Appropriate monitoring and countermeasures are recommended.

Effect of premedication with butorphanol or methadone on ease of endoscopic duodenal intubation in dogs.

OBJECTIVE: The effect of premedication with butorphanol or methadone on ease of endoscopic duodenal intubation. STUDY DESIGN: Prospective, randomized, blinded clinical trial. ANIMALS: A group of 20 client-owned dogs. METHODS: Dogs were assigned randomly to be administered intravenous (IV) premedication with either butorphanol (0.4 mg kg-1) or methadone (0.3 mg kg-1). General anaesthesia was induced with propofol to effect and maintained with isoflurane in 100% oxygen. Sedation score 20 minutes after premedication administration and induction dose of propofol were recorded. Heart rate, mean arterial pressure, haemoglobin oxygen saturation, respiratory rate and end-tidal isoflurane concentration were recorded every 5 minutes. Spontaneous lower oesophageal and pyloric sphincter opening, presence of gastro-oesophageal and duodeno-gastric reflux, antral peristaltic contractions and response to endoscopy were recorded as yes or no. Ease of duodenal intubation (EDI) was graded on a scale ranging from 1 (immediate entry with minimal manoeuvring required) to 4 (no entry after 2 minutes). Time (seconds) from the start of pyloric intubation to successfully entering the duodenum was recorded. RESULTS: Median EDI score [3 ± 1 (butorphanol), 4 ± 1 (methadone), p = 0.035], time [65 ± 36 seconds (butorphanol), 120 ± 38 seconds (methadone), p = 0.028] and number of dogs with spontaneous pyloric sphincter opening [7/10 (butorphanol), 2/10 (methadone), p = 0.035] differed between groups. No other significant differences were found. CONCLUSIONS AND CLINICAL RELEVANCE: In these clinical cases, duodenal intubation was performed with greater ease, shorter time and more frequent spontaneous opening of the pyloric sphincter after premedication with butorphanol in comparison to methadone. The use of butorphanol facilitated the passage of the endoscope and is therefore recommended for premedication prior to upper gastrointestinal tract endoscopy.

Effect of rate of administration of propofol or alfaxalone on induction dose requirements and occurrence of apnea in dogs.

OBJECTIVE: To evaluate the effect of rate of administration of propofol or alfaxalone on induction dose requirements and incidence of postinduction apnea (PIA) in dogs following premedication with methadone and dexmedetomidine. STUDY DESIGN: Prospective, randomized clinical trial. ANIMALS: Thirty-two healthy American Society of Anesthesiologists class I client-owned dogs (seven females, 25 males), aged between 5 and 54 months, weighing between 2.0 and 48.2 kg. METHODS: Dogs were premedicated intramuscularly with 0.5 mg kg-1 methadone and 5 µg kg-1 dexmedetomidine. Thirty minutes after premedication, dogs were preoxygenated for 5 minutes before the induction agent was administered intravenously via a syringe driver until orotracheal intubation was achieved. Dogs were randomized to receive alfaxalone 0.5 mg kg-1 minute-1 (A-Slow), alfaxalone 2 mg kg-1 minute-1 (A-Fast), propofol 1 mg kg-1 minute-1 (P-Slow), or propofol 4 mg kg-1 minute-1 (P-Fast). Oxygen saturation of hemoglobin (SpO2), end-tidal carbon dioxide and respiratory rate were monitored. If PIA (≥30 seconds without a breath) occurred, the time to the first spontaneous breath was measured. If SpO2 decreased below 90%, the experiment was stopped and manual ventilation initiated. RESULTS: The mean±standard deviation induction doses of alfaxalone and propofol were lower in the A-Slow [A-Slow 0.9±0.3 mg kg-1, A-Fast 2.2±0.5 mg kg-1 (p≤0.001)] and P-Slow [P-Slow 1.8±0.6 mg kg-1, P-Fast 4.1±0.7 mg kg-1 (p≤0.001)] groups, respectively. The incidence of PIA was 25% for the A-Slow and P-Slow groups and 100% for the A-Fast and P-Fast groups (p = 0.007). CONCLUSIONS AND CLINICAL RELEVANCE: Both propofol and alfaxalone following methadone and dexmedetomidine premedication caused PIA. Induction dose requirement and incidence of PIA were affected by the rate of administration of both drugs. When possible, propofol and alfaxalone doses should be reduced and administered slowly to reduce PIA.

Clinical comparison of alfaxalone, ketamine and propofol following medetomidine and methadone in dogs.

OBJECTIVE: To compare the clinical effects of alfaxalone, ketamine and propofol in dogs following premedication with medetomidine and methadone. STUDY DESIGN: Prospective, 'blinded' and randomized clinical study. ANIMALS: A total of 75 male dogs presented for neutering at a charity clinic. METHODS: Dogs were allocated to be administered alfaxalone, ketamine or propofol following premedication with medetomidine (20 µg kg-1) and methadone (0.2 mg kg-1). Dogs were temperament scored prior to premedication. Quality of sedation, induction of anaesthesia, recovery and recovery environment were scored by simple descriptive scales. Physiological variables during anaesthesia were recorded. Continuous numerical data were analysed using analysis of variance with repeated measures as necessary. Nonparametric data were analysed using Kruskal-Wallis tests and multiple comparisons using Dunn's test. Statistical significance was set at p < 0.05. RESULTS: The mean (± standard deviation) dose of alfaxalone was 0.6 ± 0.2 mg kg-1, that for ketamine was 1.5 ± 0.7 mg kg-1 and that for propofol was 0.8 ± 0.3 mg kg-1. Alfaxalone inductions were significantly smoother compared to ketamine but not to propofol. Only one of 75 of the inductions was deemed poor. There were no differences in cardiopulmonary variables between groups except immediately after induction of anaesthesia. There were no differences in quality of recovery between groups. CONCLUSIONS AND CLINICAL RELEVANCE: All three induction agents provided reliable, predictable anaesthesia conditions that were clinically indistinguishable and ideal for teaching anaesthesia skills. The medetomidine and methadone premedication resulted in profound, heavy sedation and the quality of induction of anaesthesia was better with alfaxalone compared to ketamine. No significant difference in induction quality was detected between alfaxalone and proprofol or propofol and ketamine, and these findings are likely to be of limited clinical significance when choosing an induction agent.

Effect of choline chloride premedication on xylazine-induced hypoxaemia in sheep.

OBJECTIVE: To determine the anti-inflammatory efficacy of choline in vivo and in vitro and to investigate the anti-inflammatory mechanisms of choline. STUDY DESIGN: Randomized, controlled studies. ANIMALS: In vivo trials used 16 Romney sheep. In vitro experiments utilized RAW 264.7 mouse macrophage cells. METHODS: Hypoxaemia induced in 16 sheep by intravenous (IV) injection of 50 µg kg-1 xylazine, an α-2 agonist, was measured in sheep at 0, 1 and 4 minutes using arterial blood gas analysis with and without 50 mg kg-1 IV choline chloride premedication. Cell culture studies used enzyme-linked immunosorbent assay to measure the release of tumour necrosis factor (TNF-α) from lipopolysaccharide (LPS) stimulated macrophages with and without choline chloride premedication. TNF-α release was compared to thalidomide suppressed and untreated cells. RESULTS: Choline premedication in sheep mitigated a reduction in arterial partial pressure of oxygen (PaO2) but did not prevent development of clinically significant hypoxaemia. Decrease in mean PaO2 of choline treated sheep was 6.36 kPa (47.7 mmHg) compared to 9.81 kPa (73.6 mmHg) in control sheep. In vitro studies demonstrate that choline administered concurrent with LPS activation did not significantly suppress TNF-α expression but that treatment of cells with choline 10 minutes prior to LPS activation did significantly suppress TNF-α expression. Choline pretreated cells expressed 23.99 ± 4.52 ng mg-1 TNF-α while LPS only control cells expressed 33.83 ± 3.20 ng mg-1. CONCLUSIONS: Choline is able to prevent macrophage activation in vitro when administered prior to LPS activation and may reduce hypoxaemia in sheep developing pulmonary oedema after xylazine administration. This effect requires premedication with choline. CLINICAL RELEVANCE: Pharmacological manipulation of autonomic inflammatory responses holds promise for the treatment of inflammation. However, the complex cellular mechanisms involved in this reflex means that an adequate therapy should approach multiple pathways and mechanisms of the inflammatory response.

Postinduction apnoea in dogs premedicated with acepromazine or dexmedetomidine and anaesthetized with alfaxalone or propofol.

OBJECTIVE: To compare incidence and duration of postinduction apnoea in dogs after premedication with methadone and acepromazine (MA) or methadone and dexmedetomidine (MD) followed by induction with propofol (P) or alfaxalone (A). STUDY DESIGN: Prospective, randomized clinical trial. ANIMALS: A total of 32 American Society of Anesthesiologists class I dogs (15 females, 17 males), aged between 4 months and 4 years, weighing between 3 and 46 kg. METHODS: Dogs were randomly allocated to be administered MA+P, MA+A, MD+P or MD+A (methadone 0.5 mg kg-1 and acepromazine 0.05 mg kg-1 or dexmedetomidine 5 µg kg-1). Induction agents were administered intravenously via syringe driver (P at 4 mg kg-1 minute-1 or A at 2 mg kg-1 minute-1) until successful endotracheal intubation and the endotracheal tube connected to a circle system with oxygen flow at 2 L minute-1. Oxygen saturation of haemoglobin (SpO2), end tidal partial pressure of carbon dioxide and respiratory rate were monitored continuously. If apnoea (≥ 30 seconds without breathing) occurred, the duration until first spontaneous breath was measured. If SpO2 decreased below 90% the experiment was stopped and manual ventilation initiated. Data were analysed with general linear models with significance set at p ≤ 0.05. RESULTS: There was no statistical difference in the incidence (11 of 16 dogs in A groups and 12 of 16 dogs in P groups), or mean ± standard deviation duration (A groups 125 ± 113 seconds, P groups 119 ± 109 seconds) of apnoea. The SpO2 of one dog in the MD+P group decreased below 90% during the apnoeic period. CONCLUSIONS AND CLINICAL RELEVANCE: Propofol and alfaxalone both cause postinduction apnoea and the incidence and duration of apnoea is not influenced by the use of acepromazine or dexmedetomidine in premedication. Monitoring of respiration is recommended when using these premedication and induction agent combinations.

Comparison of arterial blood pressure measurements obtained invasively or oscillometrically using a Datex S/5 Compact monitor in anaesthetised adult horses.

OBJECTIVE: To assess agreement between noninvasive blood pressure (NIBP) oscillometrically-derived values from a multiparameter monitor (Datex Ohmeda S/5 Compact) with those obtained by invasive blood pressure (IBP) measurement in anaesthetised horses undergoing elective surgery. STUDY DESIGN: Prospective clinical study. ANIMALS: A total of 40 healthy adult horses. METHODS: Horses were anaesthetised with various anaesthetic protocols (based on clinical requirements). Depending on positioning, cannulation of the facial or lateral metatarsal artery was performed for IBP measurement. The cannula was connected via a transducer to the monitor. An appropriately sized NIBP cuff was placed around the tail base and connected to the same monitor. Systolic (SAP), mean (MAP) and diastolic (DAP) arterial blood pressures were continuously recorded from the invasive system, and at 3 minute intervals from the oscillometric system, throughout the surgical procedure using a Datex iCollect program. An appropriate arithmetic correction factor was applied to the oscillometric results where the cuff was not level with the heart. Assessment of the degree of agreement between invasive and noninvasive readings at each time point was performed using a modified Bland-Altman analysis. RESULTS: While in many horses there was relatively close correlation between the values obtained over time, there was substantial variability in individual animals which resulted in wide Bland-Altman limits of agreement. The oscillometric device over-reads by approximately 32, 23 and 22 mmHg, and under-reads by 26, 17 and 19 mmHg for SAP, MAP and DAP, respectively, compared with the IBP values. However, using the mean difference and standard deviation, the device conforms to American College of Veterinary Internal Medicine (ACVIM) standards. CONCLUSIONS AND CLINICAL RELEVANCE: Oscillometric blood pressure measurement using the Datex Ohmeda S/5 Compact multiparameter monitor conforms to ACVIM standards when the NIBP cuff is placed on the tail. However, because of the wide variability in measurements, we cannot recommend this technique to guide therapy in anaesthetised adult horses.

Effect of detomidine or romifidine constant rate infusion on plasma lactate concentration and inhalant requirements during isoflurane anaesthesia in horses.

OBJECTIVE: Influence of detomidine or romifidine constant rate infusion (CRI) on plasma lactate concentration and isoflurane requirements in horses undergoing elective surgery. STUDY DESIGN: Prospective, randomised, blinded, clinical trial. ANIMALS: A total of 24 adult healthy horses. METHODS: All horses were administered intramuscular acepromazine (0.02 mg kg-1) and either intravenous detomidine (0.02 mg kg-1) (group D), romifidine (0.08 mg kg-1) (group R) or xylazine (1.0 mg kg-1) (group C) prior to anaesthesia. Group D was administered detomidine CRI (10 µg kg-1 hour-1) in lactated Ringer's solution (LRS), group R romifidine CRI (40 µg kg-1 hour-1) in LRS and group C an equivalent amount of LRS intraoperatively. Anaesthesia was induced with ketamine and diazepam and maintained with isoflurane in oxygen. Plasma lactate samples were taken prior to anaesthesia (baseline), intraoperatively (three samples at 30 minute intervals) and in recovery (at 10 minutes, once standing and 3 hours after end of anaesthesia). End-tidal isoflurane percentage (Fe'Iso) was analysed by allocating values into three periods: Prep (15 minutes after the start anaesthesia-start surgery); Surgery 1 (start surgery-30 minutes later); and Surgery 2 (end Surgery 1-end anaesthesia). A linear mixed model was used to analyse the data. A value of p<0.05 was considered significant. RESULTS: There was a difference in plasma lactate between 'baseline' and 'once standing' in all three groups (p<0.01); values did not differ significantly between groups. In groups D and R, Fe'Iso decreased significantly by 18% (to 1.03%) and by 15% (to 1.07%), respectively, during Surgery 2 compared with group C (1.26%); p<0.006, p<0.02, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Intraoperative detomidine or romifidine CRI in horses did not result in a clinically significant increase in plasma lactate compared with control group. Detomidine and romifidine infusions decreased isoflurane requirements during surgery.

A comparison of cardiopulmonary effects and anaesthetic requirements of two dexmedetomidine continuous rate infusions in alfaxalone-anaesthetized Greyhounds.

OBJECTIVE: To determine the effects of two dexmedetomidine continuous rate infusions on the minimum infusion rate of alfaxalone for total intravenous anaesthesia (TIVA), and subsequent haemodynamic and recovery effects in Greyhounds undergoing laparoscopic ovariohysterectomy. STUDY DESIGN: Prospective, randomized and blinded clinical study. ANIMALS: Twenty-four female Greyhounds. METHODS: Dogs were premedicated with dexmedetomidine 3 µg kg-1 and methadone 0.3 mg kg-1 intramuscularly. Anaesthesia was induced with IV alfaxalone to effect and maintained with a TIVA mixture of alfaxalone in combination with two different doses of dexmedetomidine (0.5 µg kg-1 hour-1 or 1 µg kg-1 hour-1; groups DEX0.5 and DEX1, respectively). The alfaxalone starting dose rate was 0.07 mg kg-1 minute-1 and was adjusted (± 0.02 mg kg-1 minute-1) every 5 minutes to maintain a suitable depth of anaesthesia. A rescue alfaxalone bolus (0.5 mg kg-1 IV) was administered if dogs moved or swallowed. The number of rescue boluses was recorded. Heart rate, arterial blood pressure and arterial blood gas were monitored. Qualities of sedation, induction and recovery were scored. Differences between groups were tested for statistical significance using a Student's t test or Mann-Whitney U test as appropriate. RESULTS: There were no differences between groups in sedation, induction and recovery quality, the median (range) induction dose of alfaxalone [DEX0.5: 2.2 (1.9-2.5) mg kg-1; DEX1: 1.8 (1.2-2.9) mg kg-1], total dose of alfaxalone rescue boluses [DEX0.5: 21.0 (12.5-38.8) mg; DEX1: 22.5 (15.5-30.6) mg] or rate of alfaxalone (DEX0.5: 0.12±0.04 mg kg-1 minute-1; DEX1: 0.12±0.03 mg kg-1 minute-1). CONCLUSIONS AND CLINICAL RELEVANCE: Co-administration of dexmedetomidine 1 µg kg-1 hour-1 failed to reduce the dose rate of alfaxalone compared with dexmedetomidine 0.5 µg kg-1 hour-1 in Greyhounds undergoing laparoscopic ovariohysterectomy. The authors recommend an alfaxalone starting dose rate of 0.1 mg kg-1 minute-1. Recovery quality was good in the majority of dogs.

Intraoperative end-tidal concentration of isoflurane in cats undergoing ovariectomy that received tramadol, buprenorphine or a combination of both.

Objectives The aim of the study was to evaluate the end-tidal concentration of isoflurane required to maintain heart and respiratory rate within ± 20% of basal measurement in cats undergoing ovariectomy that received buprenorphine, tramadol or a combination of both. Methods Thirty cats, divided into three groups, were enrolled in a simple operator-blinded, randomised study. Cats received acepromazine (0.03 mg/kg) and one of the following treatments: buprenorphine (0.02 mg/kg), tramadol (2 mg/kg) or a combination of both. Anaesthesia was induced with propofol and maintained with isoflurane titrated in order to maintain heart and respiratory rate within the target values recorded before premedication. Results Groups were similar for age, weight, dose of propofol administered, sedation and recovery scores. Cats receiving tramadol with buprenorphine were extubated earlier after isoflurane discontinuation. No statistical differences were detected in end-tidal fraction of isoflurane between buprenorphine alone or with tramadol. In cats that received tramadol or buprenorphine alone, ovarian pedicle traction caused a statistical increase in end-tidal isoflurane concentration compared with that measured during incision and suture of the skin. In cats that received the combination of tramadol plus buprenorphine no differences among surgical time points were observed. Conclusions and relevance Tramadol added to buprenorphine did not provide any advantage in decreasing the end-tidal fraction of isoflurane compared with buprenorphine alone, although it is speculated there may be an infra-additive interaction between tramadol and buprenorphine in cats.

Comparison of medetomidine-morphine and medetomidine-methadone for sedation, isoflurane requirement and postoperative analgesia in dogs undergoing laparoscopy.

OBJECTIVE: To compare the effects of intravenous (IV) medetomidine-morphine and medetomidine-methadone on preoperative sedation, isoflurane requirements and postoperative analgesia in dogs undergoing laparoscopic surgery. STUDY DESIGN: Randomized, crossover trial. ANIMALS: Twelve adult Beagle dogs weighing 15.1 ± 4.1 kg. METHODS: Dogs were administered medetomidine (2.5 µg kg-1) IV 5 minutes before either methadone (MET) or morphine (MOR) (0.3 mg kg-1) IV. Anaesthesia was induced with propofol, maintained with isoflurane in oxygen, and depth was clinically assessed and adjusted by an anaesthetist blinded to the treatment. Animals underwent laparoscopic abdominal biopsies. Sedation and nausea scores, pulse rate (PR), respiratory rate (fR), noninvasive systolic arterial blood pressure (SAP), rectal temperature (RT) and pain scores were recorded before drug administration, 5 minutes after medetomidine injection and 10 minutes after opioid administration. Propofol dose, PR, fR, SAP, oesophageal temperature (TOES), end-tidal carbon dioxide and end-tidal isoflurane concentration (Fe'Iso) were recorded intraoperatively. Pain scores, PR, fR, SAP and RT were recorded 10 minutes after extubation, every hour for 6 hours, then at 8, 18 and 24 hours. The experiment was repeated with the other drug 1 month later. RESULTS: Nine dogs completed the study. After opioid administration and intraoperatively, PR, but not SAP, was significantly lower in MET. Fe'Iso was significantly lower in MET. Temperature decreased in both treatments. Pain scores were significantly higher in MOR at 3 hours after extubation, but not at other time points. Two dogs required rescue analgesia; one with both treatments and one in MOR. CONCLUSION AND CLINICAL RELEVANCE: At the dose used, sedation produced by both drugs when combined with medetomidine was equivalent, while volatile anaesthetic requirements and PR perioperatively were lower with methadone. Postoperative analgesia was deemed to be adequate for laparoscopy with either protocol, although methadone provided better analgesia 3 hours after surgery.

Controlled mechanical ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvres during anaesthesia in laterally or dorsally recumbent horses.

OBJECTIVE: To compare the effects of controlled mechanical ventilation (CMV) and constant positive end-expiratory pressure (PEEP) and interposed recruitment manoeuvres (RMs) with those of CMV without PEEP on gas exchange during general anaesthesia and the early recovery period. STUDY DESIGN: Prospective, randomized clinical trial. ANIMALS: A total of 48 Warmblood horses undergoing elective surgery in lateral (Lat) (n = 24) or dorsal (Dors) (n = 24) recumbency. METHODS: Premedication (romifidine), induction (diazepam and ketamine) and maintenance (isoflurane in oxygen) were identical in all horses. Groups Lat- CMV and Dors-CMV (each n = 12) were ventilated using CMV. Groups Lat-RM and Dors-RM (each n = 12) were ventilated using CMV with constant PEEP (10 cmH2O) and intermittent RMs (three consecutive breaths with peak inspiratory pressure of 60 cmH2O, 80 cmH2O and 60 cmH2O, respectively). RMs were applied as required to maintain PaO2 at > 400 mmHg (> 53.3 kPa). Dobutamine was given to maintain mean arterial blood pressure at > 60 mmHg. Physiological parameters were recorded every 10 minutes. Arterial blood gases were measured intra- and postoperatively. Statistical analyses were conducted using analyses of variance (anova),t tests and the Mann-Whitney U-test. RESULTS: Horses in Dors-RM had higher PaO2 values [478 ± 35 mmHg (63.7 ± 4.6 kPa)] than horses in Dors-CMV [324 ± 45 mmHg (43.2 ± 6 kPa)] during anaesthesia and the early recovery period. There were no differences between horses in groups Lat-CMV and Lat-RM. Other measured parameters did not differ between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Ventilation with CMV, constant PEEP and interposed RM provided improved arterial oxygenation in horses in dorsal recumbency that lasted into the early recovery period, but had no benefit in horses in lateral recumbency. This mode of ventilation may provide a clinically practicable method of improving oxygenation in anaesthetized horses, especially in dorsal recumbency.

Effects of orally administered enalapril on blood pressure and hemodynamic response to vasopressors during isoflurane anesthesia in healthy dogs.

OBJECTIVE: To examine whether preanesthetic administration of enalapril, compared with placebo, results in a greater decline in blood pressure (BP) or decreased responsiveness of BP to isotonic fluids or vasopressors in healthy dogs during isoflurane anesthesia. STUDY DESIGN: Randomized, experimental, placebo-controlled, blinded, crossover study. ANIMALS: Twelve healthy, female, purpose-bred beagles. METHODS: Dogs underwent the following week-long treatment protocols, each preceded by a 1 week washout period: oral placebo twice daily (PLA); oral enalapril, 0.5 mg kg(-1) twice daily, with the 15th dose withheld on the day of anesthesia (ENA-W), and oral enalapril, 0.5 mg kg(-1) twice daily, with the 15th dose administered 90 minutes prior to anesthetic induction (ENA). On day 8 of each treatment period, dogs were anesthetized in random order utilizing a standard protocol. Following stabilization at an end-tidal isoflurane concentration (Fe'Iso) of 1.3%, invasively measured systolic (SAP), diastolic (DAP) and mean (MAP) arterial blood pressure were continuously recorded via telemetry. Hypotension (SAP < 85 mmHg) was treated with the following sequential interventions: lactated Ringer's solution (LRS) bolus (10 mL kg(-1) ); repeated LRS bolus; dopamine (7 µg kg(-1)  min(-1) ); and dopamine (10 µg kg(-1)  min(-1) ) first without and then with vasopressin (1 mU kg(-1)  hour(-1) ). RESULTS: Compared with the PLA but not the ENA-W group, the ENA group had significantly lower average SAP, DAP and MAP at an Fe'Iso of 1.3%, spent more minutes in hypotension, and required a greater number of interventions to correct moderate-to-severe mean arterial hypotension. CONCLUSIONS: In healthy dogs, enalapril administered 90 minutes prior to isoflurane anesthesia increases the degree of intra-anesthetic hypotension and the number of interventions required to correct moderate-to-severe hypotension. CLINICAL RELEVANCE: Dogs receiving angiotensin-converting enzyme inhibitors on the day of anesthesia may exhibit clinically significant intra-anesthetic hypotension.

Evaluation of the influence of atipamezole on the postoperative analgesic effect of buprenorphine in cats undergoing a surgical ovariohysterectomy.

OBJECTIVE: To evaluate the influence of atipamezole on postoperative pain scores in cats. STUDY DESIGN: Controlled, randomized, masked clinical trial. ANIMALS: Twelve healthy female domestic cats. METHODS: Cats admitted for ovariohysterectomy (OVH) surgery were randomly allocated to group atipamezole (n = 6) or group saline (n = 6) and were premedicated with buprenorphine 20 µg kg(-1) intramuscularly (IM) and alfaxalone 3.0 mg kg(-1) subcutaneously (SC). Anaesthesia was induced with alfaxalone intravenously (IV) to effect and maintained with isoflurane in oxygen. Ten minutes after extubation, cats from group atipamezole received IM atipamezole (0.0375 mg kg(-1) ) whereas group saline received an equivalent volume [0.0075 mL kg(-1) (0.003 mL kg(-1) IM)] of 0.9% saline. A validated multidimensional composite scale was used to assess pain prior to premedication and postoperatively (20 minutes after extubation). If postoperative pain scores dictated, rescue analgesia consisting of buprenorphine and meloxicam were administered. Pain score comparisons were made between the two groups using a Mann-Whitney exact test. Results are reported as the median and range. RESULTS: Preoperatively, all cats scored 0. At the postoperative pain evaluation, the pain scores from group atipamezole [16 (range, 12-20)] were not significantly different from group saline [18 (range, 15-23)] (p = 0.28). All cats required rescue analgesia post-operatively. CONCLUSIONS AND CLINICAL RELEVANCE: Atipamezole (0.0375 mg kg(-1) IM) administration did not significantly affect the postoperative pain scores in cats after OVH. Preoperative administration of buprenorphine (20 µg kg(-1) IM) did not provide adequate postoperative analgesia for feline OVH.

Effect of intravenous lidocaine on cough response to endotracheal intubation in propofol-anaesthetized dogs.

OBJECTIVE: To determine whether the administration of intravenous (IV) lidocaine before the induction of anaesthesia in premedicated dogs reduces the cough response associated with endotracheal intubation and the propofol dose required. STUDY DESIGN: Prospective, randomized, blinded clinical study. ANIMALS: A total of 84 client-owned dogs, with American Society of Anesthesiology physical status I and II. METHODS: Dogs received intramuscular (IM) acepromazine 0.02 mg kg(-1) and methadone 0.3 mg kg(-1) and were randomly allocated to one of two groups: saline (group S) and lidocaine (group L). Five minutes before the induction of anaesthesia and 40-50 minutes after premedication, group L received lidocaine (1.5 mg kg(-1) ) and group S received an equal volume of saline solution, each administered slowly IV. Anaesthesia was induced with propofol, initially 2 mg kg(-1) IV over 40 seconds, and then in increments of 0.5 mg kg(-1) every 15 seconds to effect. The same investigator anaesthetized all cases, unaware of group allocation. The following parameters were recorded: pulse rate (PR), mean arterial pressure (MAP, oscillometry), respiratory rate (fR ), sedation score immediately before and 5 minutes after treatment, and total dose of propofol required. Differences in pulse rate, MAP and propofol dose were analysed using the two-sample t-test, coughing incidence was analysed with the chi-square test, and differences in sedation score were analysed with the Mann-Whitney test. RESULTS: After treatment, the incidence of coughing at endotracheal intubation was significantly reduced in group L compared with group S (21% versus 45%; p = 0.022). There was no significant difference between the groups with regard to propofol dose required for endotracheal intubation (p = 0.122), PR (p = 0.611), MAP (p = 0.508) or sedation score (p = 0.051). CONCLUSIONS AND CLINICAL RELEVANCE: IV lidocaine can decrease the incidence of cough during endotracheal intubation in dogs premedicated with acepromazine and methadone, but does not appear to have a sparing effect on the dose of propofol required for endotracheal intubation. Use of IV lidocaine, prior to induction of anaesthesia with propofol may be beneficial in dogs where coughing at intubation would be detrimental.

The cardiovascular status of isoflurane-anaesthetized horses with and without dexmedetomidine constant rate infusion evaluated at equivalent depths of anaesthesia.

OBJECTIVE: To compare cardiac index and oxygen extraction at equivalent depths of anaesthesia between isoflurane-anaesthetized horses and horses anesthetized with isoflurane and dexmedetomidine CRI. STUDY DESIGN: Sequential, blinded, randomized, balanced, crossover study. ANIMALS: Eight horses weighing a mean ± standard deviation of 478 ± 58 kg. METHODS: Horses were premedicated with 0.03 mg kg(-1) acepromazine intramuscularly (IM) and 8 µg kg(-1) dexmedetomidine intravenously (IV). Anaesthesia was induced with 2.5 mg kg(-1) ketamine and 0.1 mg kg(-1) midazolam IV and maintained with isoflurane in oxygen and air. Horses were mechanically ventilated. Fractional concentration of end-tidal isoflurane (Fe'Iso) was stabilized at 1.7% with a CRI of 0.9% NaCl (IsoNaCl), or at 1.1% with 1.75 µg kg(-1)  hour(-1) dexmedetomidine (IsoDex). Mean arterial blood pressure was maintained above 60 mmHg by dobutamine infusion. Following nociceptive electrical stimulation, Fe'Iso was stabilized at a 0.1% lower concentration and nociceptive stimulation was repeated. This procedure was continued until the horse moved. Fe'Iso values prior to the concentration at which movement occurred were considered to indicate equivalent depths of anaesthesia between treatments. Cardiac index and oxygen extraction were compared at equivalent depths of anaesthesia using a paired Student's t-test. RESULTS: Cardiac index differed between IsoNaCl at 61 ± 12 mL kg(-1)  minute(-1) and IsoDex at 48 ± 10 mL kg(-1)  minute(-1) (p = 0.047). In addition, oxygen extraction differed between IsoNaCl at 3.4 ± 0.8 mL kg(-1)  minute(-1) and IsoDex at 4.5 ± 0.5 mL kg(-1)  minute(-1) (p = 0.0042). Two horses receiving IsoNaCl were administered dobutamine at equivalent depths of anaesthesia (7.0 and 28.8 µg kg(-1)  hour(-1) , respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Cardiovascular function in horses receiving isoflurane and 1.75 µg kg(-1)  minute(-1) dexmedetomidine is more compromised than in horses receiving a higher concentration of isoflurane and 0.9% NaCl CRI.