Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Subject: search.filters.subject.Veterinary anesthesia

Search Results

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Perioperative fluid administration to optimise haemodynamics without fluid overload in anaesthetised dogs : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Manawatu, New Zealand
    (Massey University, 2021) Sano, Hiroki
    Perioperative fluid therapy is the mainstay of anaesthetic management. Fluid administration improves haemodynamics during anaesthesia as it increases preload and thus cardiac output and blood pressure. However, excessive fluid administration can cause detrimental adverse effects, such as haemodulution and oedema, resulting in prolonged hospital stay and increased morbidity and mortality in people. Therefore, fluid administration should be restricted to those who are able to increase stroke volume or cardiac output in response to the fluid administration (responders) and should not be given to those who are unable to do so (non-responders) based on the famous “Frank–Starling law of the heart” Previously static parameters such as central venous pressure were believed to be a clinical gold standard to estimate preload and fluid responsiveness. Over the last decade, dynamic parameters such as pulse pressure variation and pleth variability index have been shown to be reliable predictors for fluid responsiveness in people. This study found that pulse pressure variation and pleth variability index were more accurate than central venous pressure for predicting fluid responsiveness in dogs. Mini-fluid challenge is another technique that is currently available and can be reliably used to determine fluid responsiveness in human medicine. Mini-fluid challenge is an administration of a small amount of fluid to increase preload. Thus, fluid responsiveness can be assessed based on whether stroke volume increases following mini-fluid challenge according to the Frank-Starling curve. The change in stroke volume of a heart at the steep portion of the Frank-Starling curve will be greater than at the plateau portion after mini-fluid challenge. The studies revealed a percentage change in pulse wave transit time (a surrogate parameter of stroke volume, which was also one of results in this thesis) following mini-fluid challenge could predict fluid responsiveness in mechanically ventilated anaesthetised dogs under an experimental condition, and spontaneously breathing anaesthetised dogs undergoing stifle surgery in clinical setting. Lastly, these methods are still of limited use in veterinary clinical practice because of availability of equipment, difficulty of their interpretation and a cumbersome process. The main purpose of this thesis was to obtain evidence on how to optimise haemodynamics in anaesthetised dogs and prevent excessive fluid administration. The time when most practitioners administer a bolus of fluid during anaesthesia is when hypotension is encountered because of anaesthesia. Thus, prevention of hypotension could avoid excessive fluid administration. Therefore, the study found that prophylactic noradrenaline administration, which counteracts some of the cardiovascular adverse effects of anaesthesia, was able to prevent hypotension, and thus minimise fluid administration in anaesthetised dogs. Although all of these methods tested in this thesis have pros and cons in clinical veterinary practice, they were shown to be able to optimise haemodynamics without fluid overload in anaesthetised dogs.
  • Thumbnail Image
    Item
    The minimal anaesthesia model : development and refinement of the concept and subsequent practical applications : a collection of papers and a monograph presented in application for the degree of Doctor of Science at Massey University, Manawatu
    (Massey University, 2020) Johnson, Craig
    The research presented in this thesis represents both my development of the minimal anaesthesia model and its application in a number of theoretical and applied areas of animal welfare science. The use of this methodology, especially when combined with other techniques such as behavioural analysis, has proven to be a very powerful way to investigate the perception of noxious stimuli. In particular it enables clear links between physical responses and the underlying affective state of the animal to be made. These links have both expanded our understanding of the development and mechanisms of pain perception in the central nervous system of mammals and also enabled the extent to which animal husbandry procedures such as castration, tail docking and killing are painful to be measured. These latter applied studies have been used as the basis for significant changes to the ways in which painful procedures are carried out. They have contributed to new ways of providing pain relief in a variety of contexts and to changing legislation to ensure that pain relief is used in practice.
  • Thumbnail Image
    Item
    Analgesic efficacy and pharmacokinetics of combinations of morphine, dexmedetomidine and maropitant in dogs : a thesis presented in partial fulfilment of the requirement for the degree of Doctor of Philosophy at Massey University, Palmerston North, New Zealand
    (Massey University, 2020) Karna, Sandeep Raj
    Multimodal analgesia is gaining popularity in veterinary medicine. It is an approach that involves the administration of two or three classes of analgesic drugs with different modes of actions to enhance the analgesic effects and lower the adverse effects associated with high dose of a single drug. In a series of experiments conducted in this thesis, the combinations of morphine, dexmedetomidine and maropitant were evaluated using different pain models with the aim of using them in a multimodal strategy in dogs undergoing ovariohysterectomy or other surgical procedures. Firstly, a pilot study evaluating the efficacy of combinations of the test drugs was performed using a hot-plate test and tail-flick test in rats. The combination of morphine and maropitant showed a significantly higher (p < 0.0001) tail-flick latency compared to all other treatment groups indicating a supra-additive effect of spinal analgesia between morphine and maropitant. A pharmacokinetic study to investigate the disposition of the test drug combinations after intramuscular (IM) administration in dogs under anaesthesia was conducted. The results showed that the elimination half-life of morphine was higher and the clearance rate was lower when combined with dexmedetomidine compared to morphine and maropitant combination or morphine alone at higher doses. This effect may have a clinical advantage of prolonging the dosing interval of morphine. A study to evaluate and compare the analgesic efficacy of the combination of morphine, dexmedetomidine and maropitant in dogs undergoing ovariohysterectomy was conducted. The study showed that dogs receiving the combination of morphine and dexmedetomidine had significantly lower (p < 0.05) pain scores, obtained by the short form of the Glasgow composite measure pain scale and visual analogue pain scale, in the postoperative period. All dogs that received dexmedetomidine showed arrhythmia and second-degree heart block immediately after IM administration. Finally, the efficacy of the test drug combinations was evaluated using changes in electroencephalographic indices of nociception (median frequency, spectral edge frequency and total power) in anaesthetised dogs subjected to a noxious electrical stimulus. The combination of morphine and dexmedetomidine showed a significantly lower change in the post stimulation median and spectral edge frequencies compared to all other treatment groups. The dogs receiving dexmedetomidine also demonstrated arrhythmia and second-degree heart block. In conclusion, the combination of morphine and dexmedetomidine showed a superior analgesic effect compared to morphine alone at higher dose and appeared to be the most effective combination among other combinations of morphine, dexmedetomidine and maropitant. The cardiovascular changes produced by the test drugs may be clinically insignificant in fit and healthy dogs. In future, the efficacy of the combination of morphine, dexmedetomidine and maropitant at other different doses rates and ratios should also be evaluated.
  • Thumbnail Image
    Item
    Evaluation of dehorning distress and its alleviation in calves : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physiology at Massey University
    (Massey University, 2002) Sylvester, Shauna P
    In this thesis, the pain-induced distress caused by the husbandry practice of dehorning cattle is assessed and methods to alleviate it are evaluated. At the time this work was conducted there were no comprehensive studies on the effects of amputation dehorning upon the welfare of the cattle. The aims of the study were to assess the distress response after dehorning and to explore the possibilities of alleviating that distress through the use of different dehorning tools, local anaesthetic and/or cautery of the scoop wound. Changes in plasma Cortisol concentrations and behaviour were used as indices of distress. It was anticipated that this research would provide scientific data to aid in the writing of welfare codes and advisory material concerning the dehorning of cattle. The Cortisol and behavioural responses of six-month-old male Friesian calves after treatment were studied. In the Cortisol studies, blood samples were taken by venipuncture from the jugular vein of each calf prior to, for the first 9 hours and at 36 h after treatment. Behavioural responses were scored by point scan behaviour sampling for the first 10 h after and on day two between 26 and 29 h after treatment. Amputation dehorning elicited a marked, biphasic Cortisol response that lasted six hours. Dehorning elicited similar Cortisol responses irrespective of the tool employed. ACTH bolus (iv. 0.28μg/kg) elicited a maximal Cortisol response. The similarity of the magnitude of the dehorning and ACTH responses suggests that dehorning was extremely distressing. The plateauing of the plasma Cortisol values between 1.5 and 3 hours after dehorning suggests the appearance of a second phase of pain, presumably from inflammation. Local anaesthesia virtually abolished the first three hours of the Cortisol response after dehorning, after which Cortisol concentrations rose transiently. Overall, this equated to a 50% reduction in the integrated Cortisol response. Cauterizing the scoop wounds effected a marginal reduction in the Cortisol response. The combination of local anaesthesia plus cauterizing the scoop wound virtually abolished the Cortisol response to amputation dehorning. This striking result is reminiscent of pre-emptive analgesia. The destruction of, and the prevention of sensitization of, nociceptors in the wound is thought to contribute to this effect. The four behaviours of tail shaking, head shaking, ear flicking and rumination, met the criteria required to use behaviour as evidence of distress. The interpretation of the behaviour data corresponded with that of the Cortisol data. Taken together, the Cortisol and behaviour data from this study, along with the subsequent work it generated, indicate that scoop dehorning is extremely noxious. If the cattle are older and amputation dehorning is necessary, it is recommended that local anaesthetic be given and if practicable combined with either ketoprofen (McMeekan et al., 1998b) or wound cautery. However, it is preferable to dehorn calves when they are younger by cautery disbudding (Petrie et al., 1996b).
  • Thumbnail Image
    Item
    The effects of four different induction techniques on anaesthetic maintenance and recovery in horses : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science at Massey University
    (Massey University, 1991) Dickson, Linda Rose
    Anaesthetic recoveries have been the target of little research, and the information available on the effect of anaesthetic induction agents on recovery lacks detail and specificity. The aim of this study was to compare the anaesthetic recovery periods after 4 different induction procedures: (1) acetylpromazine, glycerol guaiacolate, thiopentone; (2) xylazine, glycerol guaiacolate, thiopentone; (3) xylazine, ketamine; (4) acetylpromazine, glycerol guaiacolate, ketamine, which were followed by 1 hour of halothane in oxygen anaesthesia . Ten horses each received all 4 techniques with at least 1 week between successive anaesthetics. The 10 results for each induction technique were grouped, means determined, and statistical analysis performed on these group means. Strikingly, the use of thiopentone, when compared to ketamine combinations, resulted in consistently poorer recoveries. The possibility that this may be due to the persistence of subanaesthetic barbiturate levels during the recovery period is discussed. In man, residual barbiturate levels have been shown to increase the awareness of pain, and it is possible that a similar effect may be present in horses, detrimentally affecting their anaesthetic recoveries. The role of ketamine in the consistently better recoveries is unclear. It is hypothesised that it may be due to residual ketamine levels in plasma exerting a stimulatory effect on areas of the central nervous system. Interestingly, the use of acctylpromazine as a premedicant before both thiopentone and ketamine combinations, prolongs recovery and significantly increases 3 hour post anaesthetic creatinine phosphokinase (CPK) levels. No statistical relationship was found between longer recumbency times and elevated CPK levels, and it is postulated that the CPK rise may have been indirectly caused by acetylpromazine lowering the packed cell volume, and therefore muscle tissue oxygen supply. The difference in pharmacokinetics of the individual drugs used apparently influenced the smoothness and the rate of recovery observed. It cannot be assumed therefore, that horses experiencing longer or shorter anaesthetic periods would show similar recovery atttributes to those found in this study. It was concluded that, after 1 hour of anaesthetic maintenance using halothane in oxygen mixtures, there is a better chance of horses having a coordinate recovery if ketamine combinations are used as induction agents; and a more rapid recovery if xylazine/ketamine is used to induce anaesthesia.