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.

Midazolam, as a co-induction agent, has propofol sparing effects but also decreases systolic blood pressure in healthy dogs.

OBJECTIVE: To evaluate the effects of the co-administration of midazolam on the dose requirement for propofol anesthesia induction, heart rate (HR), systolic arterial pressure (SAP) and the incidence of excitement. STUDY DESIGN: Prospective, randomized, controlled and blinded clinical study, with owner consent. ANIMALS: Seventeen healthy, client owned dogs weighing 28 ± 18 kg and aged 4.9 ± 3.9 years old. METHODS: Dogs were sedated with acepromazine 0.025 mg kg(-1) and morphine 0.25 mg kg(-1) intramuscularly (IM), 30 minutes prior to induction of anesthesia. Patients were randomly allocated to receive midazolam (MP; 0.2 mg kg(-1) ) or sterile normal saline (CP; 0.04 mL kg(-1) ) intravenously (IV) over 15 seconds. Propofol was administered IV immediately following test drug and delivered at 3 mg kg(-1)  minute(-1) until intubation was possible. Scoring of pre-induction sedation, ease of intubation, quality of induction, and presence or absence of excitement following co-induction agent, was recorded. HR, SAP and respiratory rate (fR ) were obtained immediately prior to, immediately following, and 5 minutes following induction of anesthesia. RESULTS: There were no significant differences between groups with regard to weight, age, gender, or sedation. Excitement occurred in 5/9 dogs following midazolam administration, with none noted in the control group. The dose of propofol administered to the midazolam group was significantly less than in the control group. Differences in HR were not significant between groups. SAP was significantly lower in the midazolam group compared with baseline values 5 minutes after its administration. However, values remained clinically acceptable. CONCLUSIONS AND CLINICAL RELEVANCE: The co-administration of midazolam with propofol decreased the total dose of propofol needed for induction of anesthesia in sedated healthy dogs, caused some excitement and a clinically unimportant decrease in SAP.

Increases in heart rate and systolic blood pressure in anesthetized dogs affected with X-linked muscular dystrophy after cisatracurium administration: a retrospective study.

BACKGROUND: Most patients affected with Duchenne muscular dystrophy (DMD) present with arrhythmias and cardiomyopathies. Drugs which potentially may induce tachycardia or hypertension could precipitate acute cardiac failure in these patients and should be avoided. METHODS: Thirty anesthesia records of five experimental male golden retriever cross-bred dogs affected with X-linked muscular dystrophy (GRDM), a model of DMD, were retrospectively reviewed (DMD group). Anesthesia records were compared with those of 10 golden retriever dogs not affected with muscular dystrophy (control group). Records were excluded if dogs received anticholinergics or vasoactive amines. Anesthesia was induced with fentanyl followed by propofol, both intravenously. After orotracheal intubation, all dogs' lungs were mechanically ventilated. Anesthesia was maintained with infusion of fentanyl and propofol (DMD group) or isoflurane in oxygen (control group). Pure O(2) was provided to the DMD group. Cisatracurium (0.1 mg·kg(-1) ) was administered intravenously to all dogs. Five-min interval recordings of HR and systolic blood pressures (SAP) were obtained. RESULTS: Immediately after the administration of cisatracurium, absolute values for HR and SAP significantly increased by 78.3 ± 37.0 b·min(-1) (115.4 ± 64.9%) and 33.0 ± 28.3 mmHg (33.5 ± 31.2%), respectively, in all DMD dogs and remained significantly increased for 10 and 30 min, respectively. Dogs in the control group did not show significant increases in HR or SAP after cisatracurium administration. All dogs recovered from anesthesia without complications. CONCLUSION: In this report, increases in HR and SAP could be associated with the administration of cisatracurium in individuals affected with X-linked muscular dystrophy. These cardiovascular changes deserve further investigation.