Swine model in transplant research: Review of anaesthesia and perioperative management

Tailoring anaesthetic strategies for diabetes research: Acepromazine vs. medetomidine in Aachen minipigs

Pre-established anaesthetic protocols in animal models might unexpectedly interfere with the main outcome of scientific projects and therefore they need to account for the specific research goals. We aimed to optimize the anaesthetic protocol and animal handling strategies in a diabetes-related-study exemplifying how the anaesthetic approach must be adjusted for individual research targets. Aachen minipigs were used as a model to test long-lasting skin glucose sensors for diabetic human patients. A total of 6 animals participated in two or three rounds of experiments. Each round lasted 2 months, with a maximum of 2 rounds per year. In each round, animals were anaesthetised 4 times: for glucose sensors insertion, twice for glucagon stress tests (GST), and a last time for removal of sensors. Acepromazine (ACE) was compared to medetomidine (MED) in association with butorphanol (BUT) and Ketamine (KET) and 4 parameters were analysed to define the optimum anaesthetic protocol including: sedation level, anaesthesia duration, effects on blood glucose and safety. ACE-BUT demonstrated a weaker sedative effect but reduced overall experimental time, minimized anaesthetic risk and minimally interfered with the glucose metabolism. The improvement obtained by animal conditioning and handling strategies applied in this study were not objectively estimated, although the aversion behavior was completely abolished. Based on the analysed parameters, the use of acepromazine is proposed to be superior when Aachen Minipigs are used specifically as a model for diabetes-related studies, albeit the recommendations for the anaesthesia of minipigs suggest otherwise.

Physiological and Clinical Responses in Pigs in Relation to Plasma Concentrations during Anesthesia with Dexmedetomidine, Tiletamine, Zolazepam, and Butorphanol

Simple Summary

Reliable protocols are needed for short-term anesthesia in pigs. The study’s aim is to identify an anesthetic procedure that, without the use of sophisticated equipment, ensures an acceptable depth and length of anesthesia, a regular spontaneous breathing pattern, and a stable hemodynamic condition for the animal. A total of 12 pigs were given a single intramuscular injection of dexmedetomidine, tiletamine, zolazepam, and butorphanol. To investigate the possibility of prolonging the anesthesia, six of the pigs also received an intravenous dose of the drug combination after one hour. Physiological and clinical responses and drug plasma concentrations were examined. The main results suggest that intramuscular administration of the drug combination provides up to two hours of anesthesia with stable physiological parameters and an acceptable level of analgesia. An intravenous administration of one-third of the original dosage prolonged the anesthesia for another 30 min. Since the pigs were able to breathe spontaneously, none of them were intubated. The study also provides new information about each drug’s plasma concentrations and the impact of the drug combination in pigs. This technique can be used to perform nonsurgical operations or transports when short-term anesthesia is required.

Abstract

Reliable protocols for short-term anesthetics are essential to safeguard animal welfare during medical investigations. The aim of the study was to assess the adequacy and reliability of an anesthetic protocol and to evaluate physiological and clinical responses, in relation to the drug plasma concentrations, for pigs undergoing short-term anesthesia. A second aim was to see whether an intravenous dosage could prolong the anesthesia. The anesthesia was induced by an intramuscular injection of dexmedetomidine, tiletamine-zolazepam, and butorphanol in 12 pigs. In six of the pigs, a repeated injection intravenously of one-third of the initial dose was given after one hour. The physiological and clinical effects from induction to recovery were examined. Plasma concentrations of the drugs were analyzed and pharmacokinetic parameters were calculated. Each drug’s absorption and time to maximal concentration were rapid. All pigs were able to maintain spontaneous respiration. The route of administration did not alter the half-life of the drug. The results suggest that intramuscular administration of the four-drug combination provides up to two hours of anesthesia with stable physiological parameters and an acceptable level of analgesia while maintaining spontaneous respiration. A repeated intravenous injection may be used to extend the time of anesthesia by 30 min.

Prolonged Delivery of Apomorphine Through the Buccal Mucosa, Towards a Noninvasive Sustained Administration Method in Parkinson's Disease: In Vivo Investigations in Pigs

In the current work, prolonged systemic delivery of apomorphine via buccal mucosa was shown to be a promising treatment for Parkinson's disease as a substitute for clinically utilized subcutaneous infusions. Due to extensive 'first-pass' metabolism, apomorphine is administered parenterally to bypass liver metabolism. Drawbacks of parenteral administration cause low patient compliance and adherence to treatment. On the other hand, while also bypassing the liver, delivery through buccal mucosa has a superior safety profile, is less costly, lacks pain and discomfort, and possesses excellent accessibility, overall augmenting patient compliance. Current in vivo study in pigs showed: (1) steady plateau levels of apomorphine in plasma were obtained 30 min following administration and remained constant for 8 h until a delivery device was removed, (2) bioavailability of apomorphine was 55%-80% as opposed to <2% peroral and (3) simulation of the pharmacokinetic profile obtained in pigs predicted therapeutically relevant levels of apomorphine in human. Furthermore, antipyrine was incorporated as a permeation marker to enable mechanistic investigation of apomorphine release from the delivery device and its permeation through the buccal mucosa. In addition, limitations of an Ussing diffusion chamber as an ex vivo research tool were also discussed.

Prolonged oral transmucosal delivery of highly lipophilic drug cannabidiol

Delivery of drugs through oral mucosa enables bypass of the gastrointestinal tract and "first pass" metabolism in the liver and the gut. Thus, a higher and less variable bioavailability can be obtained. Mechanisms of this administration route for cannabidiol were investigated in the current research in pigs. Results show that cannabidiol has substantially low permeability rate over 8 h through oral mucosa and accumulates significantly within it. Furthermore, following the removal of the delivery device, residual prolongation of release from the oral mucosa into systemic blood circulation continues for several hours. This method of delivery enabled acquisition of clinically relevant plasma levels of cannabidiol. The absorption profile indicates that cannabidiol, as well as other lipophilic molecules, should be delivered through oral mucosa for systemic absorption from a device that conceals the drug and prevents its washout by the saliva flow and subsequent ingestion into gastrointestinal tract.