The effect of body condition on propofol requirement in dogs

Anaesthetic mortality in dogs: A worldwide analysis and risk assessment

BACKGROUND

Ensuring patient safety during small animal anaesthesia is crucial. This study aimed to assess anaesthetic-related deaths in dogs globally, identify risks and protective factors and inform clinical practice.

METHODS

This prospective cohort multicentric study involved 55,022 dogs from 405 veterinary centres across various countries. Data on anaesthesia-related deaths from premedication to 48 hours post-extubation were collected. Logistic regression was used to analyse patient demographics, American Society of Anesthesiologists (ASA) classification, procedure type and anaesthetic drugs used.

RESULTS

Anaesthetic-related mortality was 0.69%. Most deaths occurred postoperatively (81%). Age, obesity and a higher ASA classification score were associated with increased mortality. Urgent procedures, non-urgent but unscheduled anaesthesias and short procedures also had higher mortality. Some sedatives, systemic analgesics, hypnotics and the use of locoregional anaesthesia were linked to a decrease in mortality.

LIMITATIONS

The limitations of the study include the non-randomised sample, potential selection bias, lack of response rate quantification, variable data quality control, subjectivity in classifying causes of death and limited analysis of variables.

CONCLUSION

Careful patient evaluation, drug selection and monitoring can be associated with reduced mortality. These findings can be used to develop guidelines and strategies to improve patient safety and outcomes. Further research is needed to refine protocols, enhance data quality systems and explore additional risk mitigation measures.

The effect of age on the induction dose of propofol for general anesthesia in dogs

OBJECTIVE

In people, the dose of propofol (DOP) required for procedural sedation and anesthesia decreases significantly with age. The objective of this study was to determine if the DOP required to perform endotracheal intubation decreases with age in dogs.

STUDY DESIGN

Retrospective case series.

ANIMALS

1397 dogs.

METHODS

Data from dogs anesthetized at referral center (2017-2020) were analyzed with three multivariate linear regression models with backward elimination using a combination of either absolute age, physiologic age, or life expectancy (ratio between age at the time of anesthetic event and expected age of death for each breed obtained from previous literature) as well as other factors as independent variables, and DOP as the dependent variable. The DOP for each quartile of life expectancy (<25%, 25-50%, 50-75%, 75-100%, >100%) was compared using one-way ANOVA. Significance was set at alpha = 0.025.

RESULTS

Mean age was 7.2 ± 4.1 years, life expectancy 59.8 ± 33%, weight 19 ± 14 kg, and DOP 3.76 ± 1.8 mg kg-1. Among age models, only life expectancy was a predictor of DOP (-0.37 mg kg-1; P = 0.013) but of minimal clinical importance. The DOP by life age expectancy quartile was 3.9 ± 2.3, 3.8 ± 1.8, 3.6 ± 1.8, 3.7 ± 1.7, and 3.4 ± 1.6 mg kg-1, respectively (P = 0.20). Yorkshire Terrier, Chihuahua, Maltese, mixed breed dogs under 10 kg, and Shih Tzu required higher DOP. Status of neutered male, ASA E, and Boxer, Labrador and Golden Retriever breeds decreased DOP, along with certain premedication drugs.

CONCLUSIONS AND CLINICAL RELEVANCE

In contrast to what is observed in people, an age cut-off predictive of DOP does not exist. Percentage of elapsed life expectancy along with other factors such as breed, premedication drug, emergency procedure, and reproductive status significantly alter DOP. In older dogs, the dose of propofol can be adjusted based on their elapsed life expectancy.

Effect of atropine and propofol on the minimum anaesthetic concentration of isoflurane in the freshwater turtle Trachemys scripta (yellow-bellied slider)

OBJECTIVE

To determine if the administration of atropine would reduce the measured minimum anaesthetic concentration of isoflurane (MAC_isoflurane) in freshwater turtles - the yellow-bellied slider (Trachemys scripta scripta).

STUDY DESIGN

Paired, blinded, randomized, prospective studies of 1) the effect of atropine in isoflurane anaesthetized freshwater turtles (T. scripta scripta) and 2) the effect of atropine in yellow-bellied sliders in which anaesthesia was induced with propofol and maintained with isoflurane.

ANIMALS

T. scripta scripta (n = 8), female, adult.

METHODS

Atropine (2 mg kg^-1) or an isovolumetric control injection of saline was administered intraperitoneally 15 minutes prior to induction of anaesthesia with isoflurane. Individual MAC_isoflurane was then determined by end-tidal gas analysis in a bracketing design by an experimenter blinded to the administered drug, with a 2 week washout period. The experiment was repeated, with atropine (2 mg kg^-1) or saline administered intravascularly in combination with propofol for anaesthetic induction. Linear mixed modelling was used to determine the effects of atropine and propofol on the individual MAC_isoflurane. Data are presented as mean ± standard deviation.

RESULTS

Premedication with atropine significantly reduced MAC_isoflurane (p = 0.0039). In isoflurane-induced T. scripta scripta, MAC_isoflurane decreased from 4.2 ± 0.4% to 3.3 ± 0.8% when atropine had been administered. Propofol as an induction agent had a MAC-sparing effect (p < 0.001) such that MAC_isoflurane following propofol and a control injection of saline was 2.3 ± 1.0%, which decreased further to 1.5 ± 0.8% when propofol was combined with atropine.

CONCLUSIONS AND CLINICAL RELEVANCE

Atropine, presumably by inhibiting parasympathetically mediated pulmonary artery constriction, decreases right-to-left cardiac shunting and the MAC_isoflurane in yellow-bellied sliders, and thereby may facilitate control of inhalant anaesthesia. Propofol can be used for induction of anaesthesia and reduces the required concentration of inhaled anaesthesia assessed 1.5 hours following induction.

Pre-anaesthetic clinical examination influences anaesthetic protocol in dogs undergoing general anaesthesia and sedation

OBJECTIVES

Identify whether pre-anaesthetic clinical examination influences anaesthetic and analgesic agents and techniques protocol in dogs presented for general anaesthesia and sedation at a large referral hospital.

MATERIALS AND METHODS

In this prospective clinical audit, 554 dogs, undergoing general anaesthesia or sedation for surgical, diagnostic or imaging procedures were included. Multiple attending anaesthetists completed a questionnaire divided into four sections (American Society of Anesthesiologists physical status classification, anaesthetic and analgesic agents and techniques protocol, pre-anaesthetic clinical examination findings and changes made to the anaesthetic protocol). The attending anaesthetist was able to review the patient's history before planning the anaesthetic and analgesic agents and techniques protocol. The patients were examined and changes in American Society of Anesthesiologists physical status classification or anaesthetic protocol were recorded.

RESULTS

The initial anaesthetic and analgesic agents and techniques protocol was altered in 23.3% (n=129/554) of cases following a pre-anaesthetic clinical examination, but American Society of Anesthesiologists physical status reclassification occurred in only 8.0% (n=37/464) of cases. Multivariable logistic regression analysis showed that pre-anaesthetic clinical examination performed by European College of Veterinary Anaesthesia and Analgesia diplomates (odds ratio 5.8, 95% confidence interval 2.0 to 17.2), compared to anaesthesia interns, and the presence of an audible heart murmur (odds ratio 2.4, 95% confidence interval 1.4 to 4.4) were factors linked to changes in anaesthetic and analgesic agents and techniques protocol, whereas for each one kilogram increase in patient's weight, the odds of a change in anaesthetic and analgesic agents and techniques protocol to occur decreased by 1.7% (odds ratio 0.98, 95% confidence interval 0.97 to 1.0).

CLINICAL SIGNIFICANCE

Pre-anaesthetic clinical examination has impact on American Society of Anesthesiologists physical status classification, therefore estimation of patient's anaesthetic risk, and influences anaesthetic and analgesic agents and techniques protocol choice.

Comparative study of anaesthesia induction in obese dogs using propofol dosages based on lean body weight or total body weight

The objective of this study was to compare the dosages for anesthesia induction in obese dogs using propofol based on lean body weight or total body weight. For this purpose, seven dogs with ideal body condition score (BCS) (BCS 4-5; 17.3 ± 2.5% fat mass) were included in the control group (CG), seven obese dogs (BCS 8-9; 45.7 ± 2.9% fat mass) in the total body weight group (TBWG) and seven obese dogs (BCS 8-9; 42.8 ± 6.3% fat mass) in the lean body weight group (LBWG). Anaesthesia was induced by a constant rate infusion of propofol at 150 mg kg-1 hour-1 through a propofol infusion pump until the loss of consciousness; the animals in CG and TBWG received a propofol infusion based on total body weight; the animals in LBWG received a propofol infusion based on lean body mass (in kg) determined by the deuterium dilution method. The results were compared between the groups using the Tukey test (p < 0.05). The propofol dosage used was 11.4 ± 3.2 mg kg-1, 8.0± 2.0 mg kg-1 and 14.1 ± 4.7 mg kg-1 in groups CG, TBWG and LBWG, respectively, and they were different among all groups (p < 0.001). There was also a statistical difference in the time between the start of propofol infusion and loss of consciousness in which LBWG took longer than CG and TBWG (p = 0.004). This study shows that obese dogs require lower dosages of propofol when inducing anesthesia than ideal BCS dogs anesthetized with dosages based on total body weight, when the propofol dosages are calculated on the basis of muscle mass it should be increased.

Evaluation and optimisation of propofol pharmacokinetic parameters in cats for target-controlled infusion

The aim of this study was to develop and evaluate a pharmacokinetic model-driven infusion of propofol in premedicated cats. In a first step, propofol (10 mg/kg) was administered intravenously over 60 seconds to induce anaesthesia for the elective neutering of seven healthy cats, premedicated intramuscularly with 0.3 mg/kg methadone, 0.01 mg/kg medetomidine and 2 mg/kg ketamine. Venous blood samples were collected over 240 minutes, and propofol concentrations were measured via a validated high-performance liquid chromatography assay. Selected pharmacokinetic parameters, determined by a three-compartment open linear model, were entered into a computer-controlled infusion pump (target-controlled infusion-1 (TCI-1)). In a second step, TCI-1 was used to induce and maintain general anaesthesia in nine cats undergoing neutering. Predicted and measured plasma concentrations of propofol were compared at specific time points. In a third step, the pharmacokinetic parameters were modified according to the results from the use of TCI-1 and were evaluated again in six cats. For this TCI-2 group, the median values of median performance error and median absolute performance error were -1.85 per cent and 29.67 per cent, respectively, indicating that it performed adequately. Neither hypotension nor respiratory depression was observed during TCI-1 and TCI-2. Mean anaesthesia time and time to extubation in the TCI-2 group were 73.90 (±20.29) and 8.04 (±5.46) minutes, respectively.

Anaesthetic induction and recovery characteristics of a diazepam-ketamine combination compared with propofol in dogs

Induction of anaesthesia occasionally has been associated with undesirable behaviour in dogs. High quality of induction of anaesthesia with propofol has been well described while in contrast variable induction and recovery quality has been associated with diazepam-ketamine. In this study, anaesthetic induction and recovery characteristics of diazepam-ketamine combination with propofol alone were compared in dogs undergoing elective orchidectomy. Thirty-six healthy adult male dogs were used. After habitus scoring (simple descriptive scale [SDS]), the dogs were sedated with morphine and acepromazine. Forty minutes later a premedication score (SDS) was allocated and general anaesthesia was induced using a combination of diazepam-ketamine (Group D/K) or propofol (Group P) and maintained with isoflurane. Scores for the quality of induction, intubation and degree of myoclonus were allocated (SDS). Orchidectomy was performed after which recovery from anaesthesia was scored (SDS) and times to extubation and standing were recorded. Data were analysed using descriptive statistics and Kappa Reliability and Kendall Tau B tests. Both groups were associated with acceptable quality of induction and recovery from anaesthesia. Group P, however, was associated with a poorer quality of induction (p = 0.014), prolonged induction period (p = 0.0018) and more pronounced myoclonus (p = 0.003), but had better quality of recovery (p = 0.000002) and shorter recovery times (p = 0.035) compared with Group D/K. Diazepam-ketamine and propofol are associated with acceptable induction and recovery from anaesthesia. Propofol had inferior anaesthetic induction characteristics, but superior and quicker recovery from anaesthesia compared with diazepam-ketamine.

Pharmacokinetics and pharmacodynamics of propofol with or without 2% benzyl alcohol following a single induction dose administered intravenously in cats

OBJECTIVE

To compare the pharmacokinetics and pharmacodynamics of propofol with or without 2% benzyl alcohol administered intravenously (IV) as a single induction dose in cats.

STUDY DESIGN

Prospective experimental study.

ANIMALS

Six healthy adult cats, three female intact, three male castrated, weighing 4.8 ± 1.8 kg.

METHODS

Cats received 8 mg kg(-1) IV of propofol (P) or propofol with 2% benzyl alcohol (P28) using a randomized crossover design. Venous blood samples were collected at predetermined time points to 24 hours after drug administration to determine drug plasma concentrations. Physiologic and behavioral variables were also recorded. Propofol and benzyl alcohol concentrations were determined using high pressure liquid chromatography with fluorescence detection. Pharmacokinetic parameters were described using a 2-compartment model. Pharmacokinetic and pharmacodynamic parameters were analyzed using repeated measures anova (p < 0.05).

RESULTS

Plasma concentrations of benzyl alcohol were below the lower limits of quantification (LLOQ) at all time points for two of the six cats (33%), and by 30 minutes for the remaining four cats. Propofol pharmacokinetics, with or without 2% benzyl alcohol, were characterized by rapid distribution, a long elimination phase, and a large volume of distribution. No differences were noted between treatments with the exception of clearance from the second compartment (CLD2), which was 23.6 and 38.8 mL kg(-1)  minute(-1) in the P and P28 treatments, respectively. Physiologic and behavioral variables were not different between treatments with the exception of heart rate at 4 hours post administration.

CONCLUSIONS AND CLINICAL RELEVANCE

The addition of 2% benzyl alcohol as a preservative minimally altered the pharmacokinetics and pharmacodynamics of propofol 1% emulsion when administered as a single IV bolus in this group of cats. These data support the cautious use of propofol with 2% benzyl alcohol for induction of anesthesia in healthy cats.