Laboratory animal anaesthesia: a practical introduction for research workers and technicians

274 Pages·1996·4.1 MB·English

by  P A Flecknell

Preface
The majority of laboratory animals are anaesthetized by staff who have not
received specialist training in this field. Unfortunately, most textbooks of
human or veterinary anaesthesia assume that the reader has a basic knowledge
of the subject. Because of this, a good deal of published information has
remained relatively inaccessible and this has limited the introduction of new
techniques into the field of laboratory animal anaesthesia.
This handbook attempts to provide a basic guide to anaesthesia for research
workers and animal technicians. It is not intended to be a comprehensive text
on animal anaesthesia, but concentrates on those areas that are of greatest
practical importance when anaesthetizing laboratory animals.
The first sections of the book deal with the general principles of pre
operative care, anaesthetic techniques and anaesthetic management. The
most important properties of the anaesthetic and other agents used are out
lined, but a detailed description of their pharmacology has been deliberately
excluded. These sections also provide details of some of the equipment that the
author has found useful when anaesthetizing laboratory animals.
These general sections of the book should be read before using any of the
anaesthetic regimens described in the final sections. In particular, it is hoped
that the reader will study the sections on post-operative care and the provision
of effective pain reliejf before carrying out any operative procedures on
animals.
In order to provide rapid, easily accessible guidelines a list of recommended
anaesthetic regimens for each of the common laboratory species is given in
Appendix 1. For research workers who require alternative techniques, a wider
range of anaesthetic regimens is discussed together with an extensive list of
dose rates for each species in Chapter 7.
In addition to providing guidance on basic anaesthetic technique, an intro
duction to more specialist procedures such as long-term anaesthesia and the
use of neuromuscular blocking agents has been included. These sections
provide only initial guidance and it is recommended that, whenever possi
ble, an experienced veterinary anaesthetist should be consulted before attempt
ing these techniques.
P. A, FLECKNELL
Preface to the second edition
Since writing the first edition of this book there has been a welcome
increase in concern for the welfare of laboratory animals. One result of
this has been the introduction by a number of countries of formal training
requirements for new research workers. This increased interest in animal
welfare has also led to the improved dissemination of information regard
ing 'best practice' in many aspects of laboratory animal science. The
second edition of Laboratory Animal Anaesthesia has benefited from this
exchange of information, and the additions and revisions which have been
included owe much to comments from my colleagues around the world. A
major addition to this new edition is the inclusion of illustrations of
techniques and equipment. The format of the book remains relatively
unchanged, except for Chapter 7, which now incorporates some of the
information previously included in the Appendices. This enables more of
the information relating to a particular species to be accessed quickly and
easily. Brief descriptions of anaesthetic techniques for fish, amphibia,
reptiles and birds have also been included, to provide some guidance for
dealing with these species.
P. A. FLECKNELL
Glossary
Inevitably, a number of specialist terms are used throughout this book and
these are defined below.
Anaesthesia a state of controllable, reversible insensibil
ity in which sensory perception and motor
responses are both markedly depressed
Analgesia the temporary abolition or diminution of
pain perception
Analeptic drug which stimulates respiration
Anoxia complete deprivation of oxygen for tissue
respiration
Apnoea temporary cessation of breathing
Arrhythmia (cardiac) arrhythmias are alterations in the
normal rhythm of the heart
Asystole lack of cardiac muscle contractions
Ataxia lack of co-ordination, 'wobbliness'
BMR basal metabolic rate
Bradycardia slowing of the heart rate
CNS central nervous system
CNS depressant any agent that modifies function by depres
sing sensory or motor responses in the CNS
Xll GLOSSARY
Cyanosis blue or purple colouring of the skin or visible
membranes due to the presence of an
increased concentration of reduced haemo
globin in capillary blood, symptomatic of
hypoxia.
Dosages all dosages are expressed as milligrams of
drug per kilogram of body weight (mg kg
~^), except for the neuroleptanalgesic com
binations which are more conveniently
expressed as ml of commercial or diluted
premixed solution per kg body weight (ml
kg"')
Dosage schedules u.i.d. — once daily
b.i.d. — twice daily
t.i.d. — three times daily
q.i.d. — four times daily
Dyspnoea laboured breathing
ECG electrocardiogram
Hypercapnia elevated blood carbon dioxide content
Hyperpnoea fast or deep breathing
Hypertension elevated (arterial) blood pressure
Hypnotic a drug that induces a state resembling deep
sleep, but usually with little analgesic effect
Hypocapnia reduced blood carbon dioxide content
Hypopnoea slow or shallow breathing
Hypotension a fall in (arterial) blood pressure
Hypothermia a fall in body temperature
Hypovolaemia a fall in circulating blood volume
GLOSSARY xiii
Hypoxia depressed levels of oxygen
Induction (of anaesthesia) the initial establishment of a state of anaes
thesia
Injections routes of administration are abbreviated as
follows:
i/v — intravenous
i/m — intramuscular
i/p — intraperitioneal
s/c — subcutaneous
Laryngospasm spasm of the vocal cords, producing com
plete or partial obstruction of the airway
Minute volume the volume of gas breathed in 1 minute, i.e.
the product of tidal volume and respiratory
rate
Narcosis a state of insensibility or stupor from which
it is difficult to arouse the animal
Normovolaemic having a normal circulating blood volume
PC02 partial pressure of carbon dioxide
per OS by mouth
P02 partial pressure of oxygen
Polypnoea rapid, panting breathing
Pulmonary ventilation the mechanical expansion and contraction of
the lungs in order to renew alveolar air with
fresh atmospheric air
Tachycardia an increase in heart rate
Tachypnoea rapid respiration
Tidal volume the volume of gas expired with each breath
List of Tables
Table 1.1 Pre-anaesthetic checks of anaesthetic equipment. 2
Table 3.1 Endotracheal intubation, equipment required. 21
Table 3.2 Recommended fresh gas flow rates for different anaesthetic circuits. 26
Table 3.3 Induction and maintenance concentrations of inhalation anaesthetic
agents. 44
Table 3.4 Physical characteristics and relative potency (MAC50) of different
volatile anaesthetics. 45
Table 3.5 Minimum Alveolar Concentration (MAC50) values (%) for inhalation
anaesthetics in different species. 46
Table 3.6 Checklist of criteria for selection of an anaesthetic regimen for
laboratory animals. 72
Table 4.1
Blood gas values for animals breathing air. 91
Table 4.2
Basic guide for coping with cardiovascular emergencies, and infusion
rates of some drugs commonly used for cardiovascular support. 96
Table 5.1 Dose rates for neuromuscular blocking agents. 104
Table 5.2 Characteristics of a selection of commercially available mechanical
ventilators. 106
Table 5.3 Suggested ventilation rates for laboratory animals. 109
Table 5.4 Suggested regimens for total intravenous anaesthesia for long term
anaesthesia. 112
Table 6.1 Approximate volumes for fluid replacement therapy by intraperitoneal
or subcutaneous administration. 132
Table 6.2a Antibiotic and antibacterial drug doses for laboratory animals (small
mammals). 134
Table 6.2b Antibiotic and antibacterial drug doses for laboratory animals (larger
species). 135
Table 6.3a Suggested dose rates for Non-Steroidal Anti-Inflammatory Drugs in
laboratory animals (small mammals). 144
Table 6.3b Suggested dose rates for Non-Steroidal Anti-Inflammatory Drugs in
laboratory animals (larger species). 145
Table 6.3c Suggested dose rates for Opioid analgesics in laboratory animals
(small mammals). 146
XVI LIST OF TABLES
Table 6.3d Suggested dose rates for Opioid analgesics in laboratory animals
(larger species). 147
Table 7.1 Sedatives, tranquillisers and other pre-anaesthetic medication for use
in the rat. 162
Table 7.2
Anaesthetic dose rates in the rat. 164-5
Table 7.3
Antagonists to anaesthetic regimens for use in rodents and rabbits. 166
Table 7.4
Sedatives, tranquillisers and other pre-anaesthetic medication for use
in the mouse. 168
Table 7.5
Anaesthetic dose rates in the mouse. 170
Table 7.6
Sedatives, tranquillisers and other pre-anaesthetic medication for use
Table 7.7 in the hamster. 172
Table 7.8 Anaesthetic dose rates in the hamster. 174
Sedatives, tranquillisers and other pre-anaesthetic medication for use
Table 7.9
in the gerbil. 175
Table 7.10
Anaesthetic dose rates in the gerbil. 177
Sedatives, tranquillisers and other pre-anaesthetic medication for use
Table 7.11
in the guinea pig. 179
Table 7.12
Anaesthetic dose rates in the guinea pig. 180
Table 7.13 Sedatives, tranquillisers and other pre-anaesthetic medication for use
Table 7.14 in the rabbit. 184
Anaesthetic dose rates in the rabbit. 186-7
Table 7.15
Sedatives, tranquillisers and other pre-anaesthetic medication for use
Table 7.16
in the cat. 191
Anaesthetic dose rates in the cat. 194-5
Table 7.17
Sedatives, tranquillisers and other pre-anaesthetic medication for use
Table 7.18
in the dog. 197
Table 7.19 Anaesthetic dose rates in the dog. 199
Table 7.20 Sedatives, tranquillisers and other pre-anaesthetic medication for use
in the ferret. 201
Table 7.21
Anaesthetic dose rates in the ferret. 203
Table 7.22
Seadtives, tranquillisers and other pre-anaesthetic medication for use
Table 7.23 in the pig. 204
Table 7.24 Anaesthetic dose rates in the pig. 206-7
Sedatives, tranquillisers and other pre-anaesthetic medication for use
Table 7.25
in sheep and goats. 210
Table 7.26 Anaesthetic dose rates in sheep and goats. 212
Sedatives, tranquillisers and other pre-anaesthetic medication for use
in non-human primates. 214
Anaesthetic dose rates in the non-human primate. 215
Anaesthetic, sedative and analgesic drugs for use in birds. 219
List of Figures
Fig 3.1 Mobile anaesthetic workstation for use with small laboratory animals. 18
Fig 3.2 Concentric mask system to enable effective gas scavenging. 19
Fig 3.3 Endotracheal tubes. 20
Fig 3.4 Laryngoscope blades. 22
Fig 3.5 Anaesthetic induction chamber for small animals. 23
Fig 3.6 Double chamber system for anaesthetising small mammals. 24
Fig 3.7 Open anaesthetic circuit with delivery of anaesthetic gases by means
of a face-mask. 25
Fig 3.8 Waste anaesthetic gas scavenging system for use with small laboratory
animals. 26
Fig 3.9 i) Ayre's T-piece. ii) Jackson-Rees modified T-piece. 28
Fig 3.10 Ayre's T-piece. 28
Fig 3.11 i) Bain (coaxial) circuit. ii) Modified Bain (coaxial) circuit. 30
Fig 3.12 a) Bain (coaxial) circuit. b) Modified Bain (coaxial) circuit. 31
Fig 3.13 Magill circuit. 32
Fig 3.14 Magill circuit. 33
Fig 3.15 Circle system. 34
Fig 3.16 Circle system. 35
Fig 3.17 To and fro system. 35
Fig 3.18 To and fro system. 36
Fig 3.19 Apparatus required for endotracheal intubation of a rabbit under
direct vision. 40
Fig 3.20 Rabbit positioned for blind intubation. 41
Fig 3.21 Intubation of the rat using a purpose-made laryngoscope blade. 42
Fig 3.22 Apparatus for intubation of the rat. 42
Fig 3.23 Apparatus for intravenous injection and intravenous infusions in
small animals. 53
Fig 3.24 Placement and anchoring of an intravenous catheter in the rabbit. 54
Fig 3.25 Variation in sleep times following a standard dose of pentobarbitone
(60 mg/kg) in a range of different inbred strains of mouse. 56
xviii LIST OF FIGURES
Fig 3.26 Typical anaesthesia (black) and sleep times (shaded) in laboratory
rats anaesthetised with injectable anaesthetics. 58
Fig 3.27
Effect of anaesthesia on arterial blood pressure in the cat. 63
Fig 4.1
Pulse oximetry in the guinea pig. 82
Fig 4.2
Pulse oximetry in the rabbit. 82
Fig 4.3
Sleep time in mice anaesthetised with pentobarbitone (60 mg/kg, 1/p)
and maintained at three different room temperatures. 99
Fig 4.4
Rat wrapped in bubble-packing to minimise heat loss. 100
Fig 4.5
The rate of fall of body temperature in 5 rats anaesthetised with
fentanyl/fluanisone/midazolam, using a range of different techniques
to reduce heat loss. 101
Fig 6.1 Subcutaneous administration of fluid to the guinea pig immediately
prior to recovery from anaesthesia. 131
Acknowledgements
I would like to thank my colleagues at the Clinical Research Centre,
Harrow and the University of Newcastle upon Tyne for their advice and
helpful criticism of various parts of this text. In particular, I am grateful to
Dr Richard Wootton for his many helpful comments during the develop
ment of this book.
Thanks are also due to Anne Al-Jumaili and Maggie Smith for typing the
manuscript and for coping with the numerous revisions of the text so
cheerfully.
I am particularly grateful to Ruth, my wife, for her constant assistance
during all stages of the preparation of this book.
During the preparation of the second edition, many colleagues and
friends have provided helpful advice and comments, in particular Julie
Drage, Anna Meredith, Tim Morris, Peter Nolan and Simon Young.
Special thanks are due to Ken Boschert, the instigator and operator of
COMPMED. Without the benefit of this electronic conferencing system,
the new edition of this book could not have benefited from the comments,
contributions and requests for additional information from the many
'COMPMEDDERs' involved in anaesthetizing laboratory animals around
the world.
Finally, I wish to thank my colleagues in the Audio-Visual Centre at
Newcastle for providing the illustrations for this new edition.