Veterinary Anaesthesia

Principles to Practice

Alexandra Dugdale, Georgina Beaumont, Carl Bradbrook, Matthew Gurney, Alexandra H. A. Dugdale

• Publisher: Wiley-Blackwell
• Year: 2020
• Print ISBN: 9781119246770
• eBook ISBN: 9781119246787
• Edition: 2
• Topic: Medizin
• Subtopic: Veterinärmedizin

Thorough revision of a comprehensive and highly readable textbook on veterinary anaesthesia

A popular book amongst veterinary students and veterinary anaesthesia residents, the new edition of Veterinary Anaesthesia: Principles to Practice continues to be a comprehensive textbook covering the key principles of veterinary anaesthesia, encompassing a wide range of species.                                                                                                                   

Fully revised, the information is summarised in a simple, accessible format to help readers navigate and locate relevant information quickly. Filled with technical and species-based chapters, it offers a quick reference guide to analgesic infusions, as well as emergency drug dose charts for canines, felines, and equines.

• Provides broad coverage of the basics of veterinary anaesthesia and how it is implemented in clinical practice
• Includes new information on mechanisms of general anaesthesia
• Features new and improved photographs and line illustrations, plus end of chapter questions to test your knowledge
• Covers veterinary anaesthesia for a wide range of species, including dogs, cats, horses, rabbits, donkeys, and pigs
• Expands example case material to increase relevance to day-to-day clinical practice

Updated to contain the latest developments in the field, Veterinary Anaesthesia: Principles to Practice is designed specifically for veterinary students and those preparing to take advanced qualifications in veterinary anaesthesia. It is also a useful reference for veterinarians in practice and advanced veterinary nurses and technicians.

1
Concepts and Mechanisms of General Anaesthesia

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LEARNING OBJECTIVES

• To be able to define general anaesthesia.
• To be able to discuss general anaesthesia in terms of its component parts, i.e. the triad of general anaesthesia.
• To be able to define balanced anaesthesia.

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1.1 Definitions

Anaesthesia literally means ‘lack of sensation/feeling’ (from an meaning ‘without’ and aesthesia pertaining to ‘feeling’). Therefore, general anaesthesia means global/total lack of sensations, whereas local anaesthesia relates to lack of sensation in a localised part of the body.

General anaesthesia can be defined as a state of unconsciousness produced by a process of controlled, reversible, intoxication of the central nervous system (CNS), whereby the patient neither perceives nor recalls noxious (or other) stimuli.

General anaesthesia is, however, often referred to as the state of the patient when the three criteria in the triad of general anaesthesia have been met.

1.1.1 The Triad of General Anaesthesia

1. Unconsciousness: no perception or memory (therefore including amnesia), of any sensory, or indeed motor, event.
2. Analgesia (or, more correctly in an unconscious patient, antinociception): can also be thought of as suppressed responses/reflexes to nociceptive sensory inputs.
3. Suppressed reflexes: autonomic (e.g. haemodynamic, respiratory and thermoregulatory) and somatic (e.g. proprioceptive reflexes such as the righting reflex).
   • Suppression of somatic reflexes can be useful, e.g. it can provide a degree of muscular weakness/relaxation.
   • Suppression of autonomic reflexes can be a nuisance (see Chapter 18 on Monitoring), but autonomic stability can be a desirable component of anaesthesia and is often listed as a fourth component.

All these components could potentially be achieved in a patient following administration of a single ‘anaesthetic’ drug but, e.g. if that drug did not have very good analgesic properties, then large doses would be required to produce sufficiently ‘deep’ unconsciousness to reduce the response to noxious stimuli. Such deep anaesthesia is often associated with extreme depression of the CNS and homeostatic reflexes (Table 1.1).

An alternative approach, therefore, would be to produce each component (of the ‘triad’) separately by administering several drugs, each of which targets one component more specifically. This latter approach is theoretically advantageous because, by ‘titrating to specific effect’, relatively smaller doses of each individual drug tend to be sufficient, thereby minimising both each individual drug's, and the overall, side effects. This ‘polypharmacy’ approach is often referred to as balanced anaesthesia.

1.1.2 Balanced Anaesthesia

The administration of a number of different drugs, each with different actions, given during the immediate peri‐operative period, to produce an overall state of general anaesthesia, which fulfils the criteria of unconsciousness, analgesia, and muscle relaxation.

Table 1.1 Summary of effects of general anaesthesia.

Central Nervous System Depression Loss of consciousness Damping of reflexes Cardiovascular → Hypotension Respiratory → Hypoventilation Thermoregulatory → Hypothermia Postural → Reduced muscle tone Central modulation of nociception (hopefully providing analgesia/antinociception) Cardiovascular System Depression (→ Hypotension) Reflex (e.g. baroreflex) suppression (centrally and peripherally) Changes in autonomic balance Changes in vasomotor tone (drug effects, centrally and peripherally) Myocardial depression Direct (drugs) Indirect (e.g. hypoxaemia, hypercapnia [acidosis]) Respiratory Depression (→ Hypoventilation; resulting in hypercapnia/hypoxaemia) Reflex suppression (↓ventila...

Table of contents

• Cover
• Table of Contents
• Preface
• Acknowledgements
• About the Companion Website
• 1 Concepts and Mechanisms of General Anaesthesia
• 2 Patient Safety
• 3 Pain
• 4 Sedation and Premedication
• 5 Injectable Anaesthetic Agents
• 6 Analgesic Infusions
• 7 Intravascular Catheters/Cannulae
• 8 Inhalation Anaesthetic Agents
• 9 Anaesthetic Breathing Systems and Airway Devices
• 10 Anaesthetic Machines, Vaporisers, and Gas Cylinders
• 11 Anaesthetic Machine Checks
• 12 Local Anaesthetics
• 13 Local Anaesthetic Techniques for the HeadSmall Animals
• 14 Local Anaesthetic Techniques for the Limbs
• 15 Miscellaneous Local Anaesthetic Techniques
• 16 Local Anaesthetic Techniques
• 17 Muscle Relaxants
• 18 Monitoring Animals during General Anaesthesia
• 19 Troubleshooting Some of the Problems Encountered in Anaesthetised Patients
• 20 Inadvertent Peri‐operative Hypothermia
• 21 Blood Gas Analysis
• 22 Lactate
• 23 Fluid Therapy
• 24 Electrolytes
• 25 Drugs Affecting the Cardiovascular System
• 26 Shock, SIRS, MODS/MOF, Sepsis
• 27 Gastric Dilation/Volvulus (GDV)
• 28 Equine Sedation and Premedication
• 29 Equine Heart Murmurs
• 30 Equine Anaesthesia
• 31 Equine Intravenous Anaesthesia in the Field and Standing Chemical Restraint
• 32 Donkeys
• 33 Ruminants
• 34 Lamoids (South American Camelids)
• 35 Pigs
• 36 Rabbit Anaesthesia
• 37 Neonates/Paediatrics
• 38 Senescent/Geriatric Patients
• 39 Pregnancy and Caesarean Sections
• 40 Obesity
• 41 Dental and Oral Considerations
• 42 Ocular Surgery Considerations
• 43 Orthopaedic and Neurosurgery Considerations
• 44 Renal Considerations
• 45 Hepatic Considerations
• 46 Endocrine Considerations
• 47 Background to Neuroanaesthesia for the Brain
• 48 Cardiac Considerations
• 49 Respiratory Considerations
• 50 Respiratory Emergencies
• 51 Cardiopulmonary Cerebral Resuscitation (CPCR)
• Appendix A: Canine Emergency Drug Doses
• Appendix B: Feline Emergency Drug Doses
• Appendix C: Equine Emergency Drug Doses
• Answers to Self‐test Questions
• Index
• End User License Agreement