Table of Contents
Title page
Copyright page
Preface
How to use your textbook
Features contained within your textbook
About the companion website
Abbreviations
1: History of anaesthesia
First documented anaesthetic
Ether and chloroform
Anaesthesia as a medical specialty
The development and use of local anaesthetics
Typical career path in anaesthesia
Useful links
2: Monitoring
Electrocardiography (ECG)
Oximetry
Blood pressure (BP) and cardiac output
Gas analysis
End tidal CO2 (ETCO2) monitoring
Airway pressure
Central venous pressure (CVP)
3: Equipment
Anaesthetic machine
Vaporizer
Safety features
Breathing circuits
4: Airway devices
Supraglottic devices
Infraglottic devices
Emergency airway devices
5: Fluid management
Fluid compartments
Intravenous fluids
Fluid prescribing
Assessment of fluid status
6: Preoperative preparation of the patient for surgery
Timing of surgery
Assessment of risk
Preoperative assessment clinics
Fasting
Preoperative care
Arrival in theatre
7: Temperature regulation
Consequences of hypothermia
Monitoring temperature during anaesthesia
Maintaining temperature during anaesthesia
Postoperative shivering
8: The perioperative patient journey
Preoperative stage
Intraoperative stage
Postoperative stage
9: General anaesthesia – inhalational anaesthetics
Minimum alveolar concentration (MAC)
General effects
10: General anaesthesia – intravenous anaesthetics
Propofol (2,6-diisopropylphenol)
Thiopental
Benzodiazepines (e.g. midazolam)
Ketamine
Etomidate
11: Local anaesthetics
Uses
Mechanism of action
Speed of onset of action
Duration of action
Toxicity
Other side effects
Eutectic mixture of local anaesthetics (EMLA) and intravenous regional anaesthesia (IVRA)
12: Neuromuscular blocking drugs
Depolarizing neuromuscular blocking drugs (NMBDs) – suxamethonium
Non-depolarizing neuromuscular blocking drugs
Monitoring of muscle paralysis
13: Acute pain
Pain management
14: Postoperative nausea and vomiting
Mechanism
Treatment
Management
15: Chronic pain
Neuropathic pain
Chronic back pain
Neck pain
Fibromyalgia (FMS) and myofascial (MFS) syndromes
Headache and facial pain
16: The airway
Airway assessment
Management of the airway (basic)
The expected difficult airway
The unexpected difficult airway
Unstable neck
17: Emergency anaesthesia
What is an emergency?
Resuscitation
Gastric emptying
Preparing a patient for emergency surgery
18: Obstetric anaesthesia
Epidurals for pain relief in labour
Lower segment Caesarean section
Other areas
Risks
19: Ophthalmic anaesthesia
Cataract surgery
Squint surgery
Vitreoretinal surgery
Penetrating eye injury
Problems in ophthalmic anaesthesia
20: Paediatric anaesthesia
Anaesthetic management of children
Areas of interest
21: Cardiac and thoracic anaesthesia
Cardiac anaesthesia
Thoracic surgery
22: Regional anaesthesia
Central (neuraxial) blockade
Nerve plexus blockade
23: Anaesthetic emergencies in the operating theatre
Aspiration
Air embolism
Laryngospasm
Failed or difficult intubation
Malignant hyperthermia (MH)
24: Anaesthetic emergencies in the wider hospital
Anaphylaxis
Cardiac arrest
Status asthmaticus
Choking/airway obstruction
25: Trauma
Primary survey
Secondary survey
Investigations
26: Orthopaedic anaesthesia
Preoperative care
Peroperative care
Postoperative care
27: Anaesthesia and obesity
Fat distribution
Respiratory system
Cardiovascular system
Other factors
Anaesthetic management
28: Anaesthesia and old age
Anaesthetic management of elderly patients
29: Anaesthesia and diabetes
General management of blood glucose in patients with diabetes
Management of blood glucose for diabetic patients undergoing surgery
General management of diabetic patients undergoing surgery
30: Anaesthesia for vascular surgery
Preoperative assessment
Preoperative treatment
Postoperative care
Ruptured abdominal aortic aneurysm (AAA): a common vascular emergency
31: Anaesthesia for ENT and maxillofacial surgery
Preoperative assessment
Special areas
Emergency surgery
32: Awareness
Causes of awareness
Methods of assessment and measurement
33: Anaesthesia for ECT, dental surgery and special needs
Anaesthesia for electroconvulsive therapy
Anaesthesia for dental surgery
Anaesthesia for those with special needs
34: Postoperative management
Analgesia
Fluids
Referral to high dependency unit/intensive care unit
Early warning scores (EWS)
Oxygen therapy
Others
35: Anaesthesia away from the hospital setting
Trauma
Battle scenarios
Index
This edition first published 2013 © 2013 by Julian Stone and William Fawcett.
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Library of Congress Cataloging-in-Publication Data
Stone, Julian, author.
Anaesthesia at a glance / Julian Stone, William Fawcett.
p. ; cm. – (At a glance)
Includes bibliographical references and index.
ISBN 978-1-4051-8756-5 (pbk. : alk. paper) – ISBN 978-1-118-76533-3 (ePub) – ISBN 978-1-118-76532-6 – ISBN 978-1-118-76531-9 – ISBN 978-1-118-76530-2 (Mobi) – ISBN 978-1-118-76529-6
I. Fawcett, William, 1962– author. II. Title. III. Series: At a glance series (Oxford, England)
[DNLM: 1. Anesthesia–methods. 2. Anesthesiology–instrumentation. 3. Anesthetics. WO 200]
RD81
617.9′6–dc23
2013018954
A catalogue record for this book is available from the British Library.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.
Cover image: © iStockphoto/Beerkoff
Cover design by Meaden Creative
Preface
Anaesthesia is often intimidating for students. Within the relatively short time allocated to this disciplines on most undergraduate curricula, there seems to be a bewildering array of unfamiliar drugs, equipment and practical procedures. Yet at the very heart of anaesthesia is the modern concept of perioperative medicine. The fundamentals of anaesthesia, such as assessment and management of the airway, respiration, circulation and analgesia, are applicable to all hospital staff involved in the care of the surgical patient.
Both authors are practising clinical anaesthetists and also actively involved in undergraduate teaching. Moreover, as anaesthetists are the largest single group of doctors within hospital medicine it seems appropriate that a contemporary undergraduate textbook is available as an introduction to the specialty.
The aim of the authors has been to cover the practice of anaesthesia to a level appropriate for a medical student who is about to embark on the Foundation Programme. Certain specialized subjects that are traditionally taught, such as physics, have therefore been omitted.
Each chapter has a self assessment section of both multiple choice questions and case studies. The answers are not exhaustive, but should encourage further reading on the subject.
Whilst this book is aimed primarily at undergraduate medical students, it may also prove of value to Foundation Doctors looking after patients in the perioperative period, doctors embarking on a career in anaesthesia and theatre staff such as Operating Department Practitioners
The authors would like to thank Laura Murphy, Helen Harvey, Elizabeth Norton, Simon Jones, Ruth Swan, Kevin Fung and Brenda Sibbald. They acknowledge and dedicate this book to those who have given encouragement and support throughout. JS would like to thank Edwina, Freddie, Hugo and Lucinda. WF would like to thank Victoria, George, Alice and Joseph.
Julian Stone
William Fawcett
How to use your textbook
Each topic is presented in a double-page spread with clear, easy-to-follow diagrams supported by succinct explanatory text.
Section not available in this digital edition
About the companion website
This book is accompanied by a companion website:
www.ataglanceseries.com/anaesthesiaThe website includes:
Abbreviations
| ABC | airway, breathing and circulation |
| AICD | automated implantable cardioverter-defibrillator |
| APL | adjustable pressure-limiting valve |
| ASA | American Society of Anesthesiologists |
| AT | anaerobic threshold |
| ATLS | advanced trauma life support |
| AVPU | alert, verbal, pain, unresponsive |
| BCIS | bone cement implantation syndrome |
| BMI | body mass index |
| BP | blood pressure |
| <C>ABC | catastrophic haemorrhage, airway, breathing and circulation |
| CABG | coronary artery bypass graft |
| CBT | cognitive behavioural therapy |
| CC | closing capacity |
| CGO | common gas outlet |
| CMRO2 | cerebral metabolic requirement for oxygen |
| CNS | central nervous system |
| CO | cardiac output |
| COPA | cuffed oropharyngeal airway |
| COPD | chronic obstructive pulmonary disease |
| CPAP | continuous positive airway pressure |
| CPB | cardiopulmonary bypass |
| CPET | cardiopulmonary exercise testing |
| CRPS | complex regional pain syndrome |
| CSE | combined spinal epidural |
| CT | computed tomography |
| CVA | cerebrovascular accident |
| CVCI | can't ventilate can't intubate |
| CVP | central venous pressure |
| CVS | cardiovascular system |
| DHCA | deep hypothermic circulatory arrest |
| DKA | diabetic ketoacidosis |
| DLT | double-lumen tube |
| DRG | dorsal root ganglion |
| DVT | deep venous thrombosis |
| ECG | electrocardiogram |
| ECT | electroconvulsive therapy |
| EMLA | eutectic mixture of local anaesthetics |
| ESR | erythrocyte sedimentation rate |
| ETCO2 | end tidal CO2 |
| ETT | endotracheal tube |
| EVAR | endovascular aneurysm repair |
| EWS | early warning scores |
| FES | fat embolism syndrome |
| FGF | fresh gas flow |
| FMS | fibromyalgia syndrome |
| FRC | functional residual capacity |
| FRCA | Fellowship of the Royal College of Anaesthetists |
| GA | general anaesthetic |
| GABA | γ-aminobutyric acid |
| GIK | glucose, insulin and potassium |
| HDU | high dependency unit |
| HR | heart rate |
| IBW | ideal body weight |
| ICM | intensive care medicine |
| ICU | intensive care unit |
| ILMA | intubating laryngeal mask airway |
| INR | international normalized ratio |
| IO | intraosseous |
| IOP | intraocular pressure |
| IPPV | intermittent positive pressure ventilation |
| IVC | inferior vena cava |
| IVRA | intravenous regional anaesthesia |
| LA | local anaesthetic |
| LiDCO | A device for measuring cardiac output continuously from an arterial line using lithium dilution |
| LMA | laryngeal mask airway |
| LV | left ventricle |
| LVEDP | left ventricular end diastolic pressure |
| LVEDV | left ventricular end diastolic volume |
| MAC | minimum alveolar concentration |
| MEOWS | modified early obstetric warning scores |
| MERT | medical emergency response team |
| MEWS | modified early warning scores |
| MFS | myofascial syndrome |
| MH | malignant hyperthermia |
| MI | myocardial ischaemia |
| MRI | magnet resonance imaging |
| NCA | nurse-controlled analgesia |
| NIDDM | non-insulin-dependent diabetes mellitus |
| NIST | non-interchangeable screw thread |
| NMBD | neuromuscular blocking drug |
| NMDA | N-methyl-d-aspartate |
| NSAID | non-steroid anti-inflammatory drug |
| OLA | one-lung anaesthesia |
| OSA | obstructive sleep apnoea |
| PCA | patient-controlled analgesia |
| PCI | percutaneous coronary intervention |
| POCD | postoperative cognitive dysfunction |
| PONV | postoperative nausea and vomiting |
| RAE | Ring–Adair–Elwyn tube |
| RS | respiratory system |
| RVEDP | right ventricular end diastolic pressure |
| SSRI | selective serotonin reuptake inhibitor |
| SVC | superior vena cava |
| SVR | systemic vascular resistance |
| TENS | transcutaneous electrical nerve stimulation |
| TIA | transient ischaemic attack |
| TIVA | total intravenous anaesthesia |
| U&E | urea and electrolytes |
| URTI | upper respiratory tract infection |
| UTI | urinary tract infection |
| VIE | vacuum insulated evaporator |
| VQ | ventilation–perfusion |
1
History of anaesthesia
Before the introduction of anaesthesia, it would not have been possible to carry out the majority of modern operations. Development of the triad of hypnosis, analgesia and muscle relaxation has enabled surgery to be performed that would otherwise be inconceivable.
Early attempts at pain reduction included the use of opium (described in Homer's Odyssey 700 bc), alcohol and coca leaves (these were chewed by Inca shamans and their saliva used for its local anaesthetic effect).
Attempts at relieving childbirth pain could (and did) result in accusations of witchcraft.
If surgery had to be performed, it usually involved restraint, administration of alcohol and the procedure being performed as quickly as possible (amputations often took a matter of seconds).
Nitrous oxide (N2O) was described and first synthesized by Joseph Priestly in 1772. It was used experimentally by Humphry Davy, who also introduced its use to London intellectuals at the time, such as the poet Samuel Taylor Coleridge, engineer James Watt and potter Josiah Wedgewood. Priestly also discovered oxygen, describing it as ‘dephlogisticated air’.
The first documented use of N2O was in North America, by Horace Wells (a dentist) in Hartford, Connecticut in December 1844, for a dental extraction in front of a medical audience. The patient cried out during the procedure (although later denied feeling any pain) and Wells was discredited, never to fully recover and eventually committing suicide.
N2O subsequently entered general dental practice in 1863.
In October 1846, William Morton (also a dentist) used ether at the Massachusetts General Hospital, Boston during an operation on a neck tumour, performed by surgeon John Warren. Dr Oliver Holmes, who was present, described the state induced by ether as ‘anaesthesia’.
On 19th December 1846, ether was used in Dumfries (during a limb amputation of a patient who had been run over by a cart) and in London (for a tooth extraction).
James Simpson (Professor of Obstetrics in Edinburgh) introduced chloroform in November 1847, having discovered its effectiveness at a dinner party held at his house on 4th November that year.
John Snow administered chloroform to Queen Victoria during the birth of Prince Leopold (chloroform a la reine). Her positive endorsement of pain relief during labour removed religious objections to the practice at that time. (Snow is also famous for his epidemiological work, which identified the Broad Street water pump as the source of a cholera epidemic in London in 1854, confirming it as a water-borne disease.)
Chloroform was later replaced due to its toxicity and potential to cause fatal cardiac dysrhythmias.
The development of anaesthesia as a specialty has been attributed to Joseph Clover. He advocated examining the patient before giving an anaesthetic as well as palpating a pulse throughout the duration of anaesthesia. He described cricothrotomy as a means of treating airway obstruction during ‘chloroform asphyxia’.
Carl Koller (an ophthalmologist from Vienna) described the use of topical cocaine for analgesia of the eye in 1884, having been given a sample by his friend Sigmund Freud (the founder of modern-day psychoanalysis) who worked in the same hospital.
In 1884, William Halstead and Richard Hall, in New York, injected local anaesthetic into tissue and nerves to produce analgesia for surgery. The following year, also in New York, Leonard Corning, a neurologist, described cocaine spinal anaesthesia in dogs; he had inadvertently performed an epidural block. Six months later, Walter Essex Wyntner in the UK and Heinrich Quincke in Germany independently described dural puncture (this was used for the treatment of hydrocephalus secondary to tubercular meningitis).
In 1899, Gustav Bier performed spinal anaesthesia on six patients as well as on his assistant – who also performed the same procedure on Bier. They tested the efficacy of the anaesthetic on each other with lit cigars and hammers. Both reported significant post dural puncture headache, which at the time they attributed to too much alcohol consumed in celebration of their achievement. He also described intravenous regional anaesthesia (IVRA), in which local anaesthetic is injected intravenously (usually prilocaine) in a limb vein, with proximal spread prevented by a tourniquet – the Bier's block.
In 1902, Henry Cushing described regional anaesthesia (blocking large nerve plexi under direct vision in patients receiving a general anaesthetic).
The Spanish surgeon Fidel Pagés Miravé described epidural anaesthesia for surgery in 1921.
Throughout all levels of training, summative assessments are carried out to ensure standards are achieved, with increasing responsibility and the opportunity for subspecialization in the more advanced years of training, for example paediatrics, obstetrics, cardiac, intensive care and pain management.
Royal College of Anaesthetists: www.rcoa.ac.uk
Association of Anaesthetists of Great Britain and Ireland: www.aagbi.org
2
Monitoring
Routine monitoring can be divided into three categories.
The anaesthetist is continuously present during the entire administration of an anaesthetic. Information obtained from clinical observation of the patient, monitoring equipment and the progress of the operation allows for the provision of a balanced anaesthetic in terms of: anaesthesia and analgesia, fluid balance, muscle relaxation and general appearance (skin colour, temperature, sweatiness etc.).
The minimum monitoring consists of: electrocardiogram (ECG), pulseoximetry, non-invasive blood pressure, capnography and other gas analysis (O2, anaesthetic vapour), airway pressure, neuromuscular blockade; see Chapter 12.
This includes: oxygen analyser, vapour analyser, breathing system, alarms and infusion limits on infusion devices. A means of recording the patient's temperature must be available, as well as a peripheral nerve stimulator when a muscle relaxant is used.
Other monitoring devices are used depending on the type of operation and the medical condition of the patient (e.g. to measure cardiovascular function). These include invasive blood pressure monitoring, central venous pressure, echocardiography, oesophageal Doppler and awareness monitors.
Continuous assessment of the heart's electrical activity can detect dysrhythmias (lead II) (Figures 2.1 and 2.2) and ischaemia (CM5 position). Most commonly, the standard lead position is used. From this the monitor can be used to measure the electrical activity between two of the leads whilst the third acts as a neutral.
It is important to remember that the heart's electrical activity does not reflect cardiac output or perfusion, for example pulseless electrical activity (ECG complexes associated with no cardiac output) may be recorded.
A pulse oximeter consists of a light source that emits red and infrared light (650 nm and 805 nm) and a photodetector. The absorption of light at these wavelengths differs in oxygenated and deoxygenated haemoglobin. Thus the relative amount of light detected after passing through a patient's body can be used to estimate the percentage oxygen saturation. The detecting probe is typically placed on the fingernail bed, or ear lobe, and only analyses the pulsatile (arterial) haemoglobin saturation.
Inaccurate readings may be caused by high ambient light levels, poor tissue perfusion (e.g. cardiac failure, hypothermia), cardiac dysrhythmias (e.g. tricuspid regurgitation), nail varnish, methaemoglobinaemia (under reads), carboxyhaemoglobin (over reads) or methylene blue (transient reduction in reading).
There can be a significant delay between an acute event (e.g. apnoea, airway obstruction, disconnection) and a reduction in the Sao2 especially if the patient is receiving supplemental oxygen, and any reading should be considered along with other monitoring parameters as well as clinical signs.
A cuff is inflated to above systolic pressure (or to a predetermined figure when taken for the first time in a new patient). A sensing probe detects arterial pulsation at systolic pressure. The maximum amplitude of pulsation is the mean arterial pressure, and the diastolic pressure is derived from the systolic and mean arterial pressures. It is important to be able to measure blood pressure by auscultating the Korotkoff heart sounds. Accurate BP measurement requires an appropriately sized cuff. The width of the cuff should be 20% greater than the diameter of the arm. A large cuff under reads BP, a small cuff over reads.
Care must be taken to avoid soft tissue injury (especially in the elderly) with prolonged periods of use, and nerve entrapment with incorrect cuff placement.
Invasive BP measurement uses an indwelling catheter to measure beat-to-beat variation in BP, and is commonly sited in the radial artery. It has the advantage of recording changes in BP immediately as opposed to non-invasive BP measurement with a cuff, which will only indicate changes in BP when it next cycles.
Indications for invasive BP measurement include: cardiovascular system (CVS) disease (e.g. ischaemic heart disease, valvular heart disease), anticipated instability (e.g. cardiac surgery, operations with large fluid shifts), serial blood samples (e.g. arterial blood gases) in patients who will be going to intensive care postoperatively, and major laparoscopic cases.
Oesophageal Doppler is a non-invasive technique for measuring cardiac output by using ultrasound to measure blood velocity in the descending aorta. This is increasingly used in major operations, especially abdominal surgery.