Abstract
Repeated anaesthesia may be required in experimental protocols and in daily veterinary practice, but anaesthesia is known to alter physiological parameters in GPs (Cavia porcellus, GPs). This study investigated the effects of repeated anaesthesia with either medetomidine-midazolam-fentanyl (MMF) or isoflurane (Iso) on physiological parameters in the GP. Twelve GPs were repeatedly administered with MMF or Iso in two anaesthesia sets. One set consisted of six 40-min anaesthesias, performed over 3 weeks (2 per week); the anaesthetic used first was randomized. Prior to Iso anaesthesia, atropine was injected. MMF anaesthesia was antagonized with AFN (atipamezole-flumazenil-naloxone). Abdominally implanted radio-telemetry devices recorded the mean arterial blood pressure (MAP), heart rate (HR) and core body temperature continuously. Additionally, respiratory rate, blood glucose and body weight were assessed. An operable state could be achieved and maintained for 40 min in all GPs. During the surgical tolerance with MMF, the GPs showed a large MAP range between the individuals. In the MMF wake- up phase, the time was shortened until the righting reflex (RR) returned and that occurred at lower MAP and HR values. Repeated Iso anaesthesia led to an increasing HR during induction (anaesthesias 2–6), non-surgical tolerance (anaesthesias 3–6) and surgical tolerance (anaesthesias 4, 6). Both anaesthetics may be used repeatedly, as repeating the anaesthesias resulted in only slightly different physiological parameters, compared to those seen with single anaesthesias. The regular atropine premedication induced HR increases and repeated MMF anaesthesia resulted in a metabolism increase which led to the faster return of RR. Nevertheless, Iso’s anaesthesia effects of strong respiratory depression and severe hypotension remained. Based on this increased anaesthesia risk with Iso, MMF anaesthesia is preferable for repeated use in GPs.
Highlights
Repeated anaesthesia may be required in experimental protocols and in daily veterinary practice
The present study investigated the effects of recurrent MMF and Iso anaesthesias on physiological parameters in GPs
The animal was transferred to the surgical preparation area, where anaesthesia was induced with intramuscular
Summary
Repeated anaesthesia may be required in experimental protocols and in daily veterinary practice. For guinea pigs (Cavia porcellus, GPs), single medetomidine-midazolam-fentanyl (MMF), isoflurane (Iso) or ketamine-xylazine (KX) anaesthesia caused substantial effects on physiological parameters [3]. KX led to a prolonged wake-up phase, associated with catalepsy and hypothermic recovery, such that it is not recommendable for use in GPs. KX led to a prolonged wake-up phase, associated with catalepsy and hypothermic recovery, such that it is not recommendable for use in GPs Based on these results, the present study investigated the effects of recurrent MMF and Iso anaesthesias on physiological parameters in GPs. The duration of defined anaesthesia phases, mean arterial blood pressure (MAP), heart rate (HR), core body temperature (BT), respiratory rate (ReR), blood glucose (BG) and body weight (BW) were investigated. Few deviations from the course of the individual MMF and Iso anaesthesia were expected, based on the outcome of repeated MMF and Iso use in the rat [4]. The repeated i.m. injections could lead to local tissue alteration and possibly to a poorer resorption of the MMF anaesthesia. The used radio-telemetry technique was valuable for our study as it offered continuously measured data with low human intervention [6] and the possibility to repeatedly anaesthetize the same individual
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