Fig. 7.1 The Mallampati score. Reproduced from Allman and Wilson, Oxford Handbook of Anaesthesia 4th edition, 2015 with permission from Oxford University Press.
Anaesthesia stems from the Greek words ‘an’ and ‘aesthesis’ meaning without sensation.
• General anaesthesia (GA): a complete loss of consciousness and loss of reflexes.
• Regional anaesthesia: analgesia, muscle relaxation, and loss of reflexes.
• Labour analgesia: local anaesthetic in the epidural space during labour providing sensory blockade but preserving motor function.
• Day surgery: a select group of patients who meet certain criteria are admitted and discharged after surgical procedures on the same day.
• Patient-controlled analgesia (PCA): a drug (e.g. IV morphine or epidural) administered in a locked syringe driver with a set dose and a lock-out time, providing control to the patient and also preventing overdose.
• Anaesthetic gases: inhalation agents used for maintenance of GA (e.g. isoflurane, sevoflurane, desflurane).
• IV anaesthetic agents: IV drugs used for induction and or maintenance of anaesthesia (e.g. thiopentone, propofol, etomidate, ketamine).
• Muscle relaxants: drugs which cause muscle relaxation by blocking receptors at the neuromuscular junction (e.g. suxamethonium, atracurium).
• Reversal agents: drugs which reverse muscle relaxation (e.g. neostigmine/glycopyrrolate).
• Preoperative assessment, examination, and type and side of surgery.
• Airway assessment and fasting history.
• Previous anaesthetic history, drug history, and allergies.
• Quantifying risk of anaesthesia and surgery.
• Familiarity with anaesthetic room and theatre.
• Anaesthetic machine check and emergency equipment.
• Drugs: pre-medication, induction/maintenance/emergence, analgesia and postoperative medications, and emergency drugs.
• Surgeon, theatre team, and operating department practitioner/assistant.
• Acknowledge roles of each team member.
• Discuss optimal running of theatre and list.
• Any concerns regarding cases (allergies, anaesthetics).
• Specific surgical and anaesthetic requirements.
• WHO checklist for each case.
Usually nurse led with a named anaesthetist for advice or review.
• Checklist and proforma based.
• Assess patient suitability for the procedure and anaesthesia.
• Highlight any serious medical conditions.
• Optimize physiological variables (e.g. BP, blood glucose).
• Advice on medications (e.g. anticoagulants, antihypertensive).
• Request additional investigations.
• Corroborate the history and complete a thorough examination to elicit new changes.
• Anaesthetic plan and consent.1
• Emergency surgical patients require pre-optimization.
A detailed history of the presenting condition and concurrent medical condition should be taken and a systematic physical examination conducted. Emphasis should be given to the cardiorespiratory system.
• Allergies: latex, antibiotics, etc.
• Antihypertensive: risk of perioperative hypotension.
• Anticoagulants: risk of perioperative bleeding.
• Opioid analgesics: high pain scores.
• Details of previous anaesthesia.
• Postoperative nausea and vomiting (N&V).
• Review old anaesthetic chart for previous operations looking for issues and problems.
• Visit the preoperative clinic and discuss the assessment with the nurse.
• Accompany the anaesthetist on the preoperative visit round.
• Have a chat with the patients regarding any apprehensions, anxiety, and the consent process.
Factors such as a class 3–4 Mallampati score (patient is asked to open the mouth with tongue protruded), thyromental distance <6 cm, restricted jaw and neck movements (e.g. arthritis), limited mouth opening, and syndromic facial presentation predict difficult intubation.
See Fig 7.1.
Fig. 7.1 The Mallampati score. Reproduced from Allman and Wilson, Oxford Handbook of Anaesthesia 4th edition, 2015 with permission from Oxford University Press.
The Association of Anaesthetists of Great Britain and Ireland (AAGBI) recommends:
• 6 hours for solid food, milk, and infant formula (children)
• 4 hours for breast milk (children)
• 2 hours for clear non-particulate and non-carbonated fluids.
Fluid balance should be assessed if the patients are elderly, have undergone bowel preparation, or have diarrhoea and vomiting (D&V). IV fluids should be prescribed.
Make sure that the following have been completed:
• Mark site and side of surgery.
• Complete preoperative checklist.
Discussion with the boss
• Ask to demonstrate each airway assessment and discuss importance.
• Discuss importance of fasting and complications of full stomach.
• Read through the hospital’s preoperative checklist and policies.
See Tables 7.1–7.3 for different scoring systems.
The POSSUM (Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity) score is more commonly used for general surgical patients. The score is based on current physiological and operative parameters. It accurately predicts the 30-day mortality and morbidity scores.
Table 7.1 Cardiac risk stratification based on surgical procedure
| High risk >5% | Intermediate risk <5% | Low risk <1% |
| Emergency major operations Aortic and major vascular surgery Peripheral vascular surgery Surgical procedures associated with large fluid shifts and/or blood loss | Carotid endarterectomy Head and neck surgery Intraperitoneal and intrathoracic surgery Orthopaedic surgery Prostate surgery | Endoscopic procedures Superficial procedures Cataract surgery Breast surgery |
This score is helpful in determining the level of fitness and physiological reserve to determine the likely outcome from a general anaesthetic.
Table 7.2 MET score
| METs >7 | METs 5–7 | METs 1–4 |
| 8. Rapidly climbing stairs, jogging slowly 9. Jumping rope slowly, moderate cycling 10. Swimming quickly, running/jogging briskly 11. Skiing, cross country, basketball 12. Running rapidly for moderate-long distances | 5. Climbing 1 flight of stairs, dancing, cycling 6. Playing golf, carrying clubs 7. Playing singles tennis | 1. Eating, working at computer, dressing 2. Walking down stairs or at home, cooking 3. Walking 1–2 blocks 4. Raking leaves, gardening |
1 MET = consumption of 3.5 mL O2/min/kg of body weight. Patients with METs <4 and undergoing high-risk surgery are more likely to suffer from perioperative cardiac events.
Table 7.3 ASA scoring system
| ASA rating | Description | Mortality (%) |
| Class I | Healthy individual | 0.1 |
| Class II | Mild systemic disease | 0.2 |
| Class III | Severe systemic disease but not incapacitating | 1.8 |
| Class IV | Incapacitating systemic disease with constant threat to life | 7.8 |
| Class V | Moribund patient not expected to survive without surgery | 9.4 |
| Class VI | Brain dead patient | |
| Class E | Suffix added for emergency surgery |
Reference
1. Yentis SM, Hartle AJ, Barker IR, et al. AAGBI: Consent for anaesthesia 2017: Association of Anaesthetists of Great Britain and Ireland. Anaesthesia 72(1):93–105.
Modern anaesthetics machines are very complex and digitalized, but the aims are the same:
1. Supply O2 and anaesthetic gases to the patient.
3. Vaporize the anaesthetic agent.
4. Breathing system for delivering gases to the patients.
5. Provide mechanical ventilation.
The anaesthetic machine is a circle system where the O2 from the back wall is delivered into the machine. The pressure and flow of the gases are regulated by pressure regulators and flow restrictors. There is a pressure release valve, which release gases if pressure increases in the system. The patients can breathe spontaneously or can be mechanically ventilated by switching on the ventilator.
• Atmospheric air consists of 21% O2, 78% N2, and 1% other gases.
• It is a major component of metabolism/aerobic respiration.
• Hyperbaric O2 therapy saturates the circulatory system resulting in increased O2 delivery to tissues.
• Observe and perform an anaesthetic machine check.
• Learn about other methods of measuring O2 concentrations in blood/gas mixtures.
• Ask your anaesthetist to show you the different Mapleson circuits available in your theatres and wards. Discuss the advantages and disadvantages of each.
O2 is the most used gas in the hospital. It is supplied at the point of use by a cylinder or a piped O2 supply. The O2 cylinders are black with a white top (international standard for colour coding for medical gases). The piped O2 in the hospital is either from a manifold or vacuum-insulated evaporator. The supply pressure is 4 bar. Most commonly oxygenation is measured by a pulse oximeter, which uses the principles of spectrophotometry, where the absorption of red and infrared waves is measured by application of Beer’s and Lambert’s laws. The ratio of absorption by oxy and de-oxy Hb is measured against a scale and O2 saturations displayed. Breathing systems are classified into open (no rebreathing), semi-open (partial rebreathing), and closed systems (total rebreathing).
The gases are measured by an in-stream or side-stream analyser and will give a breath-to-breath trace of CO2 (see Fig. 7.2).
Fig. 7.2 Capnography measurement. Reproduced from Catherine Spoors and Kevin Kiff, Training in Anaesthesia, 2010, Figure 4.15, Page 77, with permission from Oxford University Press.
The AAGBI has set minimum monitoring requirements for during and immediately after anaesthesia. This is the minimum and further monitoring such as invasive BP, urine output, arterial blood gases, cardiac output, neuromuscular blockade, temperature, and depth of anaesthesia should be considered according to the type and complexity of the surgery and anaesthesia.1
• Inhalation gases—infrared analyser.
• Identify different vaporizers and their contents.
• Identify a capnography trace. Discuss different types of traces and the underlying pathology.
• Identify all the traces on your monitor and discuss the underlying physics of their measurement.
• Discuss the interference with these traces and how it is overcome in these monitors.
1. Checketts MR, Alladi R, Ferguson K, et al. (2016). Recommendations for standards of monitoring during anaesthesia and recovery 2015: Association of Anaesthetists of Great Britain and Ireland. Anaesthesia 71(1):85–93.
The principles of anaesthesia are based on a triad of hypnosis, analgesia, and muscle relaxation. The chronology of a general anaesthetic broadly involves a number of stages:
1. Induction: usually IV agent (e.g. propofol: white milky drug), but gaseous agent can also be used (e.g. sevoflurane—in young children or presumed difficult airway).
2. Airway control: starting with face mask (Hudson) and using simple adjuncts (nasopharyngeal airway, oropharyngeal airway) proceeding to laryngeal mask airway (LMA) or endotracheal tube (ETT) intubation.
3. Intubation: often requires a muscle relaxant. These can be divided into depolarizing agents (e.g. suxamethonium, used in rapid sequence induction) and non-depolarizing agents (e.g. atracurium, rocuronium).
4. Maintenance of anaesthesia with gaseous agents or propofol infusion and potent opiates (e.g. fentanyl, remifentanil).
5. Emergence from anaesthesia by discontinuing anaesthetic agents and leading to spontaneous ventilation and extubation.
See Table 7.4.
Table 7.4 Dosages (max.) recommended for a 70 kg adult
| Anaesthetic | Dosages (max.) |
| Lidocaine | 200 mg (3 mg/kg) |
| Lidocaine with adrenaline (epinephrine) | 500 mg (7 mg/kg) |
| Prilocaine* | 400 mg (6 mg/kg) |
| Prilocaine* with adrenaline (epinephrine) | 600 mg (8 mg/kg) |
* Prilocaine is not used for local infiltration but only for Bier’s block.
• Routes: subcutaneous, topical cream, Instillagel® (e.g. for catheterization), IV (Bier’s), intra-articular.
• Complications: CVS (also used as an antiarrhythmic drug) and CNS side effects avoided if not injected intravenously and if used within maximum safe dose.
• Treatment of adverse reactions: resuscitate, treat with Intralipid®, convulsions to be treated with IV benzodiazepine.
Can be provided by central neuraxial blockade (spinal/epidural anaesthesia) or by specific nerve blocks with local anaesthetic drugs (e.g. femoral nerve block for fractured hips, transversus abdominis plane block for lower abdominal surgery). IV regional anaesthesia is better known as Bier’s block and uses tourniquets to exsanguinate limbs (below elbow and knee) to avoid systemic spread and toxicity. Tourniquet time should not exceed more than 2 hours. A Bier’s block should not exceed more than an hour.
You will be asked the differences between epidurals vs spinal anaesthesia (see Fig. 7.3 and Table 7.5).
Fig. 7.3 Midsagittal section through the lumbar spinal column with spinal puncture needle in place between the spinous processes of lumbar vertebrae L3 and L4. Notice the slightly ascending direction of the needle. The needle has pierced three ligaments and the dura/arachnoid and is in the subarachnoid space. Reproduced with permission from David L. Seiden and Siobhan Corbett, Lachman's Case Studies in Anatomy, 2013, Oxford University Press.
Table 7.5 Epidural and spinal anaesthesia
| Epidural | Spinal | |
| Onset | Slower: 25 min | Faster: 5 min |
| Site | Thoracic and lumbar spine | Below L2 to prevent spinal cord injury |
| Mode | Indwelling catheter | Single-shot injection, rarely indwelling catheter |
| Effect | Sensory loss with lower concentration and both motor and sensory with higher concentration | Sensory and motor blockade |
| Purpose | Postoperative pain relief, labour analgesia, and top-ups for caesarean section | Regional anaesthesia for procedures for pelvic and lower limb surgeries |
A patient’s impression of whether you are a good doctor may be based entirely on how promptly you relieve their pain. Ask the patient to score their pain intensity on a scale of 1–10. Pain is rated as:
• Treat the cause of the pain (if possible).
• If the pain is continuous, give regular analgesia.
• Before switching analgesia, ensure a full therapeutic dose is used.
• Avoid effervescent preparations in those with hypertension (high salt content).
• Tolerance and dependence can occur with weak opioids and adverse effects are more common in the elderly, therefore start with lower doses and titrate slowly.
See Fig. 7.4.
Fig. 7.4 Example of an analgesic ladder following WHO guidelines.
Other treatments include neuropathic analgesia (e.g. gabapentin, amitriptyline, capsaicin) 
alternative treatments (transcutaneous electrical nerve stimulation (TENS) machine, acupuncture, etc.).
Splintage of injuries, elevation, and ice packs to reduce swelling, hot water bottle for muscle spasm pain, simple dressings for minor burns/wounds.
Fear and anxiety heighten the experience of pain. The reassurance of caring staff along with an explanation of what is happening can be very helpful, as well as the presence of family or friends.
This is an emergency scenario where the patient is asleep, not breathing, and the anaesthetist is neither able to ventilate the patient by bag mask nor intubate. The primary goal here is oxygenation. There is an algorithm produced by the Difficult Airway Society and by the end of it either the patient is woken up to breathe spontaneously or a needle cricothyroidotomy is performed. A difficult airways trolley will be around in these cases.1
This is the most common critical incident during an anaesthetic, and antibiotics are the common culprits. Consider latex allergy if the presentation is slightly delayed into the surgery. The AAGBI has recommended a clear guideline and protocol to follow during an anaphylactic reaction. The main goal is initial resuscitation with oxygenation, fluids, and adrenaline (epinephrine), followed up with hydrocortisone and chlorpheniramine. Clearly document the sequence of events and take blood samples for mast cell tryptase levels at 0-, 1-, and 24-hour intervals. Follow-up and referral to the allergy clinic is very important to identify the agent causing anaphylaxis, with clear documentation in the notes and letters to the GP and patient.2
This is a serious complication of using local anaesthetic agents. The risk is very high and toxicity occurs when an excess dose is administered, inadvertently administered intravascularly or the blood concentration increases when administered around highly vascular structures. The symptoms can vary from confusion, convulsions, and arrhythmias to cardiac arrest. The key to the management is early recognition, resuscitation, and administering a 20% lipid emulsion to scavenge the local anaesthetic. Adding adrenaline (epinephrine) also reduces absorption. Common ones include lidocaine (lignocaine) and bupivacaine (or Marcaine®).3
This is a unique but very serious complication during an anaesthetic. Some patients have a genetic predisposition and are sensitive to inhalational agents and suxamethonium. When the patients are exposed to these agents there is excessive Ca2+ release from the sarcoplasmic reticulum due to defective receptors. The patients under anaesthetic become tachycardia, hypertensive, with raising temperature and end-tidal CO2. The key in management is early recognition, disconnecting patients from the inhalation agent and circuit, resuscitation, temperature control, and dantrolene.4
References
1. Difficult Airway Society (2015). Difficult Intubation Guidelines. 
www.das.uk.com/guidelines/das_intubation_guidelines
2. Association of Anaesthetists of Great Britain and Ireland (2009). Suspected anaphylactic reactions associated with anaesthesia. Anaesthesia 64:199–211.
3. Association of Anaesthetists of Great Britain and Ireland (2010). Guidelines for the Management of a Severe Local Anaesthetic Toxicity. London: AAGBI.
4. Association of Anaesthetists of Great Britain and Ireland (2011). Guidelines for the Management of a Malignant Hyperthermia Crisis. London: AAGBI.