Avian anaesthesia in general practice

This paper reviews the management of General Anaesthesia in 32 birds. The methods adopted are outlined with particular reference to the drug CT 1341*, which was used for induction and, on some occasions, maintenance of anaesthesia.     

Maintenance of anaesthesia in sheep with isoflurane, desflurane or sevoflurane

Rapid recovery from anaesthesia is advantageous in small ruminants, to reduce the risk of regurgitation. Theoretically, the least soluble inhalation agents should result in the fastest recoveries, but using additional injectable agents may negate this advantage. This study compared three inhalation agents for the maintenance of anaesthesia in sheep. Eighteen ewes that were to undergo orthopaedic surgery were allocated to one of three groups. Each group was premedicated with xylazine (0.1 mg/kg intramuscularly), anaesthesia was induced using ketamine (2 mg/kg) and midazolam (0.03 mg/kg) intravenously and analgesia provided by buprenorphine (0.008 mg/kg intramuscularly). Anaesthesia was then maintained with either isoflurane, sevoflurane or desflurane. Cardiopulmonary parameters were monitored throughout. All three inhalation agents provided adequate stable anaesthesia and there was no significant difference between the groups in their cardiopulmonary parameters or their recovery times. The mead (sd) postanaesthetic times to first swallow, first chewing attempts and ability to maintain their head lifted for five minutes were, respectively, 3.95 (2.53), 6.37 (3.68) and 32.8 (18.1) minutes for isoflurane, 3.62 (0.98), 7.66 (0.78) and 38.8 (16.6) minutes for sevoflurane, and 4.37 (1.65), 6.95 (1.52) and 29.8 (11.5) minutes for desflurane. Two sheep had poor quality recoveries after the use of sevoflurane, but all the other sheep recovered uneventfully. All three inhalation agents were suitable for the maintenance of anaesthesia in sheep but, as used in this study, there were no differences between them in speed of recovery.     

A survey of anaesthesia in small animal practice: AVA/BSAVA report

Over 150 veterinary surgeons from 53 small animal practices collaborated in a prospective survey of anaesthetic accidents and emergencies by recording all anaesthetics administered and detailing the problems they encountered. From these records it is estimated that 1 in 679 of the healthy dogs and cats died primarily as a result of anaesthesia; many of these deaths apparently occurred at a time when the animal was not under close observation. Anaesthetics involving the use of xylazine seemed to result in an exceptionally high mortality rate. Complications following endotracheal intubation appeared to be associated with several deaths in cats. The death rate in cats and dogs with pathological but not immediately life-threatening conditions was estimated to be 1 in 31. There was no evidence to suggest that some breeds (with the possible exception of the Pekingese) were more likely than others to die under anaesthesia.     

The stress response to anaesthesia in ponies: barbiturate anaesthesia

Information on the equine stress response to anaesthesia and surgery is sparse but offers a promising approach to elucidating the high anaesthetic risk in this species. Previous work has shown that halothane anaesthesia induces substantial metabolic and endocrine changes. This paper reports the effects of barbiturate anaesthesia. Anaesthesia was induced with thiopentone in six ponies and no further agents were given. They stood within 30 mins. On another occasion, these animals, and three further ponies, were anaesthetised with pentobarbitone and anaesthesia was maintained for 2 h. No surgery was performed on either occasion. Plasma concentrations of glucose, lactate, non esterified fatty acids, cortisol, insulin, catecholamines and adrenocorticotrophic hormone were measured at the same time intervals in both groups before, during and after anaesthesia. There were no significant changes in hormones or metabolites during either period of anaesthesia and normotension was maintained. This was in marked contrast to the substantial stress response and hypotension under halothane anaesthesia in the same ponies. These results suggest that barbiturates may induce less of a stress response than halothane in horses. Recovery after 2 h of pentobarbitone anaesthesia was poor, precluding its clinical use. The need for a non-cumulative intravenous agent or a non-hypotensive volatile agent for use in equine anaesthesia is discussed.     

Maintenance of equine anaesthesia over the last 50 years: Controlled inhalation of volatile anaesthetics and pulmonary ventilation

In the first edition of this journal, Barbara Weaver wrote a review titled ‘Equine Anaesthesia’, stating that, at that time, it was quickly becoming accepted practice that many horses were being anaesthetised ‘by essentially similar procedures, i.e. premedication, induction and then maintenance by controlled inhalation’. To celebrate the 50th anniversary of the first edition of this journal, this review covers the development of understanding and practice of inhalational anaesthesia and controlled ventilation in horses over the last 50 years. We review how the perceived benefits of halothane led to its widespread use, but subsequently better understanding of halothane's effects led to changes in equine anaesthetic practice and the utilisation of different inhalation agents (e.g. isoflurane and sevoflurane). We discuss how more recently, better understanding of the effects of the ‘newer’ inhalation agents’ effects has led to yet more changes in equine anaesthetic practice, and while, further new inhalation agents are unlikely to appear in the near future, further enhancements to anaesthetic practice may still lead to improved outcomes. We review advances in our understanding of the anatomy and pathophysiology of the equine lung as well of the effects of anaesthesia on lung function and how these predispose to some of the common problems of gas exchange and ventilation during anaesthesia. We identify the aims of optimal mechanical ventilation for anaesthetic management and whether the various methods of ventilatory support during equine anaesthesia achieve them. We also highlight that further developments in equipment and optimal ventilator modes are likely in the near future.     

Propofol anaesthesia in cats

Propofol was administered to 49 cats to induce anaesthesia. The mean dose required was 6.8 mg/kg and this was not affected by prior administration of acepromazine maleate. In 27 cases, propofol was also used as the principal maintenance agent (mean dose rate 0.51 mg/kg/minute). Inductions were very smooth and problem free. Intubation was easily achieved in 15 cats with the aid of local desensitisation by lignocaine spray or neuromuscular relaxation by suxamethonium. Heart rate did not vary significantly during induction or maintenance of anaesthesia but respiratory rates did fall significantly. Recovery from anaesthesia was remarkably smooth in all cases and there was no significant difference in recovery times between the cats in which halothane was the principal maintenance agent and cats which received propofol alone. Side effects were seen during recovery in eight cats and included retching, sneezing and pawing of the face.     

桥梁预防性养护在高速公路养护中的应用

本文通过查阅大量的资料,结合对混凝土的碳化、裂缝、钢筋锈蚀、支座损坏等桥梁病害进行了总结,提出了混凝土碳化预防性养护技术、混凝土裂缝的预防性养护技术、钢筋锈蚀的预防性养护技术等桥梁预防性养护技术进行了分析,以保证桥梁的质量,促进桥梁预防性养护技术的优化发展。     

预防性养护在公路养护中的应用

预防性养护是在公路还没有发生大的损害,或还没有破损严重之前,采取积极有效的措施,把公路病害控制、处治在初期阶段。在能行之有效的养护公路,保障公路正常运行的同时,最大限度的节约成本,延长公路使用寿命。本文从前期的调查摸底,到具体养护措施的实施;从整体的预防目标,到有针对性的操作进行了深入的探讨。     

Depth of anaesthesia

One hundred and fifty years after the first general anaesthetic in 1846 our knowledge about the mechanisms of general anaesthetics is still very sparse. The concept ‘depth of anaesthesia’ was introduced by John Snow (1847). He described ‘5° of narcotism’. Because one single agent had to provide all the components of general anaesthesia, the main problem for the anaesthetist was to avoid morbidity and mortality associated with excessively deep anaesthesia. The introduction of curare in 1942 allowed muscle relaxation required for surgery during a lighter level of anaesthesia, but also changed the emphasis from the problem of too deep anaesthesia and death, to too light anaesthesia and litigation. The problem of awareness during general anaesthesia with muscle relaxants provided the main impetus for monitoring depth of anaesthesia. During daily clinical practice the anaesthesiologist relies on clinical signs to evaluate anaesthetic depth, although several studies have shown a poor correlation between the 2 (Cullen et al. 1972; Evans and Davies 1984; Russell 1993). Different methods have been used in attempts to measure anaesthetic depth (Evans and Davies 1984; Stanski 1994), but none have been developed to a state where they can be used routinely in the operating theatre. This review will cover some of the parameters used to evaluate anaesthetic depth.     

Prolonged anaesthesia

Prolonged surgical anaesthesia presents different problems from those encountered in the provision of immobilization and unconsciousness for intensive therapy. Meticulous care in applying basic principles will provide surgical anaesthesia of several hours' duration. In dogs, prolonged immobilization for intensive therapy may be obtained by a routine of morphine and diazepam administration, while in cats it may be achieved by 'Saffan' anaesthesia. During prolonged unconsciousness careful monitoring of the patient is essential; an adequate urine flow can be ensured by the intravenous infusion of appropriate electrolyte solutions, and particular care has to be given to maintenance of body temperature.     

Complications of saffan anaesthesia in cats

Complications associated with Saffan anaesthesia were recorded following 100 administrations of the anaesthetic to cats. Hyperaemia or oedema of the pinnae or forepaws was recorded in 69 per cent of administrations. Other common complications included coughing and partial laryngean spasm at intubation, cyanosis, postoperative vomiting and opisthotonus. Suggestions are made for minimising the incidence of such complications.