Veterinary Anaesthesia (eBook)

Principles to Practice

Alexandra Dugdale, Georgina Beaumont, Carl Bradbrook, Matthew Gurney (Autoren)

eBook Download: EPUB

2020 | 2. Auflage
John Wiley & Sons (Verlag)
978-1-119-24678-7 (ISBN)

Infos

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.

Alex Dugdale, MA, VetMB, PhD, DVA, Dip.ECVAA, PGCert (LTHE), FHEA, MRCVS, joined ChesterGates Veterinary Specialists CVS (UK) Ltd. as a Clinical Anaesthetist in 2016, after 17 years' teaching veterinary anaesthesia at the University of Liverpool's Veterinary School, UK. She is an RCVS Recognised Specialist in Veterinary Anaesthesia and an EBVS® European Specialist in Veterinary Anaesthesia and Analgesia.

Georgina Beaumont, BVSc (Hons), MANZCVSc (VA&CC), Dip.ECVAA, MRCVS, joined Manchester Veterinary Specialists CVS (UK) Ltd. in 2017 as a Clinical Anaesthetist. She is an RCVS Recognised Specialist in Veterinary Anaesthesia and an EBVS® European Specialist in Veterinary Anaesthesia and Analgesia.

Carl Bradbrook, BVSc, CertVA, Dip.ECVAA, MRCVS, joined Anderson Moores Veterinary Specialists in 2018. He is an RCVS Recognised Specialist in Veterinary Anaesthesia and an EBVS® European Specialist in Veterinary Anaesthesia and Analgesia.

Matthew Gurney, BVSc, CertVA, Dip.ECVAA, MRCVS, joined Northwest Surgeons in early 2009, and moved to Anderson Moores Veterinary Specialists in 2018. He is an RCVS Recognised Specialist in Veterinary Anaesthesia and an EBVS® European Specialist in Veterinary Anaesthesia and Analgesia.

Inhalt

Preface ix

Acknowledgements xi

About the Companion Website xiii

1 Concepts and Mechanisms of General Anaesthesia 1

2 Patient Safety 7

3 Pain 19

4 Sedation and Premedication: Small Animals 55

5 Injectable Anaesthetic Agents 77

6 Analgesic Infusions 95

7 Intravascular Catheters/Cannulae: Some Considerations and Complications 99

8 Inhalation Anaesthetic Agents 117

9 Anaesthetic Breathing Systems and Airway Devices 139

10 Anaesthetic Machines, Vaporisers, and Gas Cylinders 167

11 Anaesthetic Machine Checks 187

12 Local Anaesthetics 191

13 Local Anaesthetic Techniques for the Head: Small Animals 205

14 Local Anaesthetic Techniques for the Limbs: Small Animals 215

15 Miscellaneous Local Anaesthetic Techniques: Small Animals 237

16 Local Anaesthetic Techniques: Horses 243

17 Muscle Relaxants 259

18 Monitoring Animals during General Anaesthesia 279

19 Troubleshooting Some of the Problems Encountered in Anaesthetised Patients 307

20 Inadvertent Peri-operative Hypothermia 313

21 Blood Gas Analysis 321

22 Lactate 337

23 Fluid Therapy 347

24 Electrolytes 377

25 Drugs Affecting the Cardiovascular System 393

26 Shock, SIRS, MODS/MOF, Sepsis 401

27 Gastric Dilation/Volvulus (GDV) 423

28 Equine Sedation and Premedication 427

29 Equine Heart Murmurs 443

30 Equine Anaesthesia 445

31 Equine Intravenous Anaesthesia in the Field and Standing Chemical Restraint 477

32 Donkeys 481

33 Ruminants: Local and General Anaesthesia 485

34 Lamoids (South American Camelids) 519

35 Pigs: Sedation and Anaesthesia 529

36 Rabbit Anaesthesia 541

37 Neonates/Paediatrics 547

38 Senescent/Geriatric Patients 551

39 Pregnancy and Caesarean Sections 555

40 Obesity 561

41 Dental and Oral Considerations 567

42 Ocular Surgery Considerations 571

43 Orthopaedic and Neurosurgery Considerations 575

44 Renal Considerations 579

45 Hepatic Considerations 583

46 Endocrine Considerations 587

47 Background to Neuroanaesthesia for the Brain 595

48 Cardiac Considerations 603

49 Respiratory Considerations 607

50 Respiratory Emergencies 611

51 Cardiopulmonary Cerebral Resuscitation (CPCR) 627

Appendix A Canine Emergency Drug Doses 637

Appendix B Feline Emergency Drug Doses 639

Appendix C Equine Emergency Drug Doses 641

Answers to Self-test Questions 643

Index 651

Textauszug

1
Concepts and Mechanisms of General Anaesthesia

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.

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 (↓ventilatory response to ↑PCO2 [↓pH], and ↓PO2) Reduced respiratory muscle activity (↓ sighing and yawning) Alveolar collapse/small airway closure (atelectasis) Reduced functional residual capacity Ventilation/perfusion mismatch

1.1.2.1 Components of the Peri‐operative Period

• Pre‐operative assessment: patient stabilisation; provision of (pre‐emptive) analgesia.
• Premedication: anxiolysis/sedation and initiation/continuation of analgesia provision if not already provided.
• Induction of anaesthesia.
• Maintenance of anaesthesia; provision of muscle relaxation; continuation of analgesia/antinociception provision.
• Recovery from anaesthesia (sometimes referred to as ‘reanimation’): aftercare; continuation of (‘preventive’) analgesia provision.

1.2 The Depth of General Anaesthesia

Some texts refer to various stages and planes of anaesthesia that try to mark the progression of the continuum between consciousness and death. When ether was used as the sole anaesthetic agent, five ‘degrees’ of progression through ever ‘deeper’ stages of anaesthesia in people, from consciousness to deep coma, were described by John Snow; Overton did similar for chloroform. Guedel developed Snow's ideas further and, in 1937, produced a chart outlining the patient's responses at each of four successive stages of diethyl ether anaesthesia. This was developed still further by Artusio in 1954, who divided Guedel's stage 1 into three planes.

Table 1.2, included purely for historical interest, describes the features of diethyl ether anaesthesia in the dog, after Guedel. The features of these stages and planes, however, do not necessarily apply similarly to other inhalant agents, and apply even less to injectable agents, to say nothing of the combination of inhalational and injectable agents that can be administered when balanced anaesthesia is practised. Furthermore, the chart is not necessarily transferrable to other species.

So, when we do not want to use ether, when we need to consider species other than dogs, when we prefer to practise ‘polypharmacy’ to achieve the desired state/depth of general anaesthesia, and when we add surgical stimulation to the anaesthetised patient (because depth of anaesthesia is not only related to the ‘dose’ of drug/s administered, but is also dependent upon the degree of stimulation [usually surgery] at the time), we should still monitor the patient's physiological responses to, and status during, anaesthesia, which are considered in more detail in Chapter 18.

Although Table 1.2 is included purely for interest, it is important to note that during induction of anaesthesia, stage II (involuntary excitement/movement) may be witnessed; and during recovery from anaesthesia, all the stages are traversed in the reverse order, such that emergence excitement/delirium (stage II) may be observed.

1.3 Mechanisms of Action of General Anaesthetic Drugs

Compounds that exert general anaesthetic effects exhibit a wide diversity of chemical structure and can be administered by injection (usually intravenously), or by inhalation. Although a unifying target for their action has been sought, the diversity in their structure makes a single target site unlikely.

Nevertheless, Meyer (1899) and Overton (1901), independently, reported that anaesthetic potency was strongly correlated with lipid solubility which sparked interest in lipid membranes as the site of action. It was variously hypothesised that anaesthetic agents may exert a non‐selective physical perturbation of a lipid site within the membrane or possibly perturb the volume or fluidity of the membrane itself. That physical dissolution of lipid‐soluble agents within plasma membranes caused their expansion, sparked the ‘critical volume’ and ‘membrane expansion’ hypotheses, with some demonstration of pressure‐reversal. The lipid theory, however, had several problems, including the fact that some isomers with identical lipid solubilities had different anaesthetic potencies, not all anaesthetic effects were reversible with applied pressure, and small temperature changes could also change membrane volume but without anaesthetic effects.

Table 1.2 Stages of ether anaesthesia in the dog, after Guedel.

Stage of anaesthesia

Depression of CNS

MM colour

Pupil size

Eyeball activity

Breathing

Stage I: stage of voluntary movement/excitement

?Sensory cortex

N / flushed

Small

Voluntary

Rapid/irregular

Stage II: stage of involuntary movement/excitement ‘delirium’

Motor cortex Decerebrate rigidity...

Produkt-Details

• Erscheint lt. Verlag: 26.5.2020
• Sprache: englisch
• Themenwelt: Veterinärmedizin
• Schlagworte: Anaesthesiology • anaesthetic • anaesthetic machines • analgesia infusions • Anesthesiology • anesthetic • anesthetic machines • animal anaesthesia • Animal anesthesia • animal medicine • cannulae • General anaesthesia • horse local block • inhalation agents • injectable agents • injured animal • local anaesthetic • managed sedation • miscell block • muscle relaxant • pain management • pain relief • patient safety • Sedation • small animal head block • small animal leg block • Veterinäranästhesie, Analgesie, Schmerzbehandlung • Veterinärmedizin • veterinary anaesthesiology • veterinary analgesia • Veterinary Anesthesia, Analgesia & Pain Medicine • Veterinary Medicine • veterinary surgery
• ISBN-10: 1-119-24678-4 / 1119246784
• ISBN-13: 978-1-119-24678-7 / 9781119246787