Use of a propofol infusion for anaesthetic maintenance in Guinea pigs (Cavia porcellus): a retrospective case series.

OBJECTIVE: To retrospectively evaluate the feasibility of a propofol infusion for anaesthetic maintenance in guinea pigs. STUDY DESIGN: Retrospective case series. ANIMALS: Client-owned guinea pigs undergoing general anaesthesia. METHODS: Anaesthetic records of guinea pigs anaesthetized between March 2015 and March 2018 were reviewed. Animals administered a propofol infusion for > 20 minutes were identified and evaluated. Procedure performed, pre-anaesthetic medication, preoperative and intraoperative respiratory rate (fR) and heart rates (HRs), total amount of propofol administered, total anaesthesia and recovery times were extracted from the records and analysed using descriptive statistics and Pearson correlation tests. Data are reported as mean (range). RESULTS: Records of 14 animals meeting the criteria were identified. Following drug combinations were administered for premedication: butorphanol 0.43 (0.3-0.5) mg kg-1, medetomidine 0.1 (0.05-0.2) mg kg-1 and midazolam 1 (0.5-2) mg kg-1 (n = 3); methadone 0.33 (0.25-0.5) mg kg-1, medetomidine 0.07 (0.01-0.1) mg kg-1 and midazolam 0.66 (0.5-1) mg kg-1 (n = 3); butorphanol 0.5 mg kg-1, medetomidine 0.05 mg kg-1 and ketamine 5 mg kg-1 (n = 2); buprenorphine 0.01 mg kg-1, medetomidine 0.07 (0.04-1) mg kg-1 and ketamine 4 (3-5) mg kg-1 (n = 3); butorphanol 0.5 mg kg-1, alfaxalone 1 mg kg-1 and midazolam 0.5 mg kg-1 (n = 1); and methadone 0.38 (0.25-0.5) mg kg-1, medetomidine 0.08 (0.06-1) mg kg-1 with midazolam 0.75 (0.5-1) mg kg-1 (n = 2). Preoperative and intraoperative HRs were 240 (160-300) and 170 (140-200) beats minute-1, respectively. Preoperative and intraoperative fR were 63 (50-86) and 37 (18-80) breaths minute-1, respectively. The propofol infusion rate was 0.45 (0.17-0.80) mg kg-1 minute-1. Total anaesthesia and recovery times were 60 (25-145) and 17 (8-60) minutes, respectively. A slight correlation was found between total propofol dose infused and recovery time (r = 0.58). CONCLUSION AND CLINICAL RELEVANCE: Propofol infusions may be a useful alternative to inhalant anaesthetics.

Evaluation of agreement between invasive and non-invasive blood pressure measurement using the PetMAP™ device in rabbits.

Background: Measurement of arterial blood pressure is recommended in anaesthetized animals to guide perioperative treatment. Invasive blood pressure measurement is considered the gold standard, however it is also technically challenging, requires specialised equipment and carries certain risks. For these reasons, non-invasive blood pressure measurement devices are commonly used and are expected to provide accurate and reliable results. This requirement is particularly true for rabbits, in whom peri-anaesthetic hypotension is commonly observed and in whom perioperative mortality remains disproportionally high. Several authors have compared different non-invasive devices with invasive measurements in rabbits and have reported contrasting results. However, to date no comparison between invasive measurements and the PetMAP™ device, that has been designed specifically for veterinary medicine, has been reported. Aim and hypothesis: The aim of the study was the comparison of invasive blood pressure measurement with PetMAP™ in rabbits. We hypothesised that PetMAP™ would show acceptable agreement with the invasive measurements according to the American College of Veterinary Internal Medicine guidelines. Materials and methods: Sixteen client-owned rabbits presenting for various surgical interventions were included in the study. Invasive measurements were performed by cannulation of an auricular artery. The PetMAP™ cuff was applied distal to the elbow according to the manufacturer's guidelines. For each measurement with PetMAP™, three invasive blood pressure values were recorded. The mean of the three invasive values was compared with one value measured with PetMAP™. Results: Data collected from 16 rabbits were used for statistical analysis. In the clinical setting, the PetMAP™ device showed significant overestimation of systolic, diastolic and mean arterial pressure, which were measured in the auricular artery. In addition, the bias was not constant, implying that the device poorly predicted changes in blood pressure. Conclusion: The PetMAP™ device did not meet any of the American College of Veterinary Internal Medicine recommendations.

Effect of dexmedetomidine vs. acepromazine-methadone premedication on limb to lung circulation time in dogs.

The study compared limb-to-lung circulation times (CT) in dogs under general anaesthesia after premedication with dexmedetomidine (DEX) or acepromazine-methadone (ACE-M). Healthy male and female dogs (n=20) were randomly assigned to receive acepromazine 0.04mg/kg and methadone 0.2mg/kg intramuscularly (IM), or DEX 0.01mg/kg IM. Anesthesia was induced with propofol and maintained with isoflurane at similar concentration in both groups. Mechanical ventilation was started immediately (20breaths/min; inspiratory to expiratory ratio 1:2) and tidal volume was adjusted to achieve an end-tidal CO2 concentration (PE'CO2) of between 3.9 and 5.3kPa. Ten minutes later arterial blood gas was analyzed and baseline data recorded for 3 minutes. A single dose of sodium bicarbonate 0,5mEq/kg was administered intravenously over 10 s starting with inspiration. Limb-to-lung CT was defined as the time interval between the start of bicarbonate injection and the recording of the highest PE'CO2. Following bicarbonate administration, PE'CO2 increased, and then rapidly decreased to baseline in both groups. CT was shorter in the ACE-M group (20±2.3 vs. 27±5.1s). Bodyweight was higher in the ACE-M group (30.6±3.9 vs. 23.3±6.8kg). Mean arterial blood pressure was higher in the DEX group (92±9 vs. 73±7mmHg) but premedication with DEX significantly prolonged CT compared to premedication with ACE-M.