Anaesthetics and Critical Care Revision Guide ✅

💉 Anaesthetics and critical care are physiology under pressure. Anaesthetics focuses on airway, analgesia, unconsciousness, immobility, monitoring and perioperative risk; critical care focuses on organ support, shock, ventilation, sepsis, sedation and escalation decisions. For exams and ward work, always start with physiology: is the airway safe?, is oxygen delivery adequate?, is perfusion failing?, is the patient ventilating?, and what reversible cause must be treated now?

✅ 1. Core Anaesthetic Principles

🫁 1.1 What Anaesthesia Does

• Hypnosis: unconsciousness or reduced awareness.
• Analgesia: pain relief using opioids, regional techniques and non-opioid analgesia.
• Amnesia: reduced memory of the procedure, depending on agents used.
• Immobility: muscle relaxation or depth of anaesthesia to allow surgery.
• Autonomic control: blunting sympathetic responses such as tachycardia and hypertension.
• Physiological support: airway protection, ventilation, oxygenation, haemodynamic support and temperature control.

💤 1.2 Types of Anaesthesia

🧠 Exam pearl: Sedation is not “light anaesthesia without risk”. Sedatives can obstruct the airway, suppress breathing and cause aspiration, especially in frail, obese, elderly or opioid-treated patients.

🧰 2. Pre-operative Assessment

Pre-operative assessment identifies modifiable risk, plans anaesthesia, reduces avoidable harm and supports informed consent. NICE NG45 covers routine preoperative testing for elective surgery, while CPOC guidance emphasises optimisation for adults being considered for surgery.

📝 2.1 Key Pre-op History

• Operation planned, urgency and expected physiological stress.
• Previous anaesthetics: difficult airway, postoperative nausea/vomiting, awareness, malignant hyperthermia, ICU admission.
• Cardiorespiratory disease: IHD, heart failure, valve disease, arrhythmia, COPD, asthma, OSA, pulmonary hypertension.
• Exercise tolerance: stairs, walking distance, functional limitation, frailty.
• Diabetes, CKD, liver disease, obesity, pregnancy possibility and neurological disease.
• Bleeding history, anticoagulants, antiplatelets and VTE history.
• Drug history: steroids, opioids, SGLT2 inhibitors, GLP-1 agonists, ACEi/ARB, diuretics, anticoagulants, antiplatelets.
• Allergies and exact reaction; distinguish nausea/intolerance from true anaphylaxis.
• Smoking, alcohol and recreational drugs.

🫁 2.2 Airway Assessment

• Mouth opening, dentition, loose teeth, jaw protrusion and Mallampati view.
• Neck movement, cervical spine disease, previous surgery/radiotherapy.
• Facial hair, obesity, OSA, large tongue, receding mandible.
• History of difficult intubation, tracheostomy, airway tumour or stridor.
• Plan for mask ventilation, supraglottic airway, intubation and rescue front-of-neck access where needed.

🧪 2.3 Pre-op Tests

• Testing should be targeted to surgical grade, comorbidity and whether results will change management.
• NICE NG45 advises reducing unnecessary routine testing and considering comorbidities such as cardiovascular, renal, respiratory disease, diabetes and obesity.
• Common tests: FBC, U&E/eGFR, LFT, clotting, HbA1c, ECG, CXR or group and save/crossmatch depending on risk.
• Pregnancy testing should be considered where relevant and discussed sensitively.
• Do not use “routine bloods” as a substitute for history, examination and risk assessment.

⚖️ 2.4 ASA Physical Status

📌 Clinical reasoning: ASA is useful but incomplete. Frailty, urgency, surgical magnitude, sepsis, anaemia, nutrition and patient priorities often matter as much as the ASA number.

💊 3. Perioperative Medication Management

💉 3.1 Diabetes Drugs and Surgery

• Perioperative diabetes plans must prevent hypoglycaemia, hyperglycaemia, ketosis and dehydration.
• Insulin regimens often need dose adjustment according to fasting time and surgery timing.
• SGLT2 inhibitors increase risk of euglycaemic DKA and are usually withheld pre-operatively according to local/CPOC guidance.
• Metformin may need withholding in renal impairment, contrast exposure or major surgery depending on local policy.
• GLP-1 receptor agonists may affect gastric emptying; local anaesthetic guidance should be followed.
• Check capillary glucose and ketones when clinically indicated, especially in type 1 diabetes or unwell patients.

🩸 3.2 Anticoagulants and Antiplatelets

• Balance bleeding risk of surgery against thrombosis risk of stopping therapy.
• Warfarin, DOACs, LMWH, aspirin, clopidogrel and dual antiplatelet therapy all need procedure-specific planning.
• Mechanical heart valves, recent VTE, recent coronary stent and AF stroke risk are high-yield considerations.
• Regional anaesthesia has strict timing rules around anticoagulants to reduce spinal/epidural haematoma risk.
• Emergency reversal may be needed for major bleeding or urgent surgery.

🧪 3.3 Steroids, ACEi/ARB and Other Drugs

• Long-term steroids can suppress the HPA axis; perioperative steroid cover may be required.
• ACE inhibitors/ARBs may contribute to intraoperative hypotension; local policy varies on withholding.
• Diuretics may worsen hypovolaemia/electrolyte disturbance.
• Opioid-tolerant patients need a specific analgesic plan and withdrawal prevention.
• Parkinson’s medications should not be delayed or omitted because severe rigidity and deterioration can occur.
• Oral contraceptives/HRT may be relevant to VTE planning depending on surgery and patient factors.

🫁 4. Airway Management

🧠 4.1 Basic Airway Manoeuvres

• Look, listen and feel for airway obstruction.
• Head tilt-chin lift opens airway unless cervical spine concern.
• Jaw thrust is preferred when C-spine injury is possible.
• Suction blood, vomit and secretions.
• Use airway adjuncts: oropharyngeal airway if unconscious; nasopharyngeal airway if tolerated and no contraindication.
• High-flow oxygen and bag-valve-mask ventilation may be lifesaving while preparing definitive airway.

🧰 4.2 Airway Devices

⚠️ 4.3 Difficult Airway and Failed Intubation

• Prioritise oxygenation over repeated laryngoscopy attempts.
• Call for help early.
• Optimise position, suction, oxygenation, equipment and operator.
• Limit attempts to prevent trauma, swelling and “can’t intubate, can’t oxygenate”.
• Use a difficult airway algorithm such as DAS/local guidance.
• Emergency front-of-neck access may be required if unable to intubate and unable to oxygenate.

🚨 Exam pearl: The failed airway death spiral is repeated attempts causing bleeding, swelling and hypoxia. Stop, oxygenate, change plan and call for help.

💤 5. Induction, Maintenance and Emergence

💉 5.1 Induction of Anaesthesia

• Preoxygenation increases oxygen reserve before apnoea.
• Induction agents include propofol, etomidate, ketamine and thiopental in selected settings.
• Opioids blunt sympathetic response and provide analgesia.
• Neuromuscular blockers facilitate intubation and surgery but remove ability to breathe.
• Hypotension can occur due to vasodilation, myocardial depression, hypovolaemia or drug effects.
• High-risk patients require careful titration, invasive monitoring and vasopressor readiness.

🍽️ 5.2 Aspiration Risk and Rapid Sequence Induction

• Aspiration risk increases with emergency surgery, bowel obstruction, pregnancy, obesity, reflux, delayed gastric emptying and inadequate fasting.
• RSI aims to reduce time between loss of consciousness and cuffed tube placement.
• Key principles: preoxygenation, prepared suction, induction agent, rapid neuromuscular blocker, avoid mask ventilation if appropriate, intubate promptly.
• Cricoid pressure practice varies and should follow local policy/training.
• Aspiration can cause hypoxia, pneumonitis, pneumonia and ARDS.

🌬️ 5.3 Maintenance

• Volatile anaesthetics or total intravenous anaesthesia maintain unconsciousness.
• Analgesia, muscle relaxation, fluids, temperature and haemodynamics are adjusted continuously.
• Monitoring includes ECG, BP, pulse oximetry, capnography, temperature, neuromuscular monitoring and anaesthetic depth where indicated.
• Capnography is essential for confirming ongoing ventilation and tube placement.

🌅 5.4 Emergence and Recovery

• Reverse neuromuscular blockade where appropriate and confirm adequate recovery.
• Ensure airway reflexes, ventilation, oxygenation and haemodynamics are safe before extubation.
• Common recovery issues: pain, nausea, hypoxia, shivering, hypotension, hypertension, bleeding, delirium.
• Extubation is an airway intervention; high-risk extubation requires a plan.

🧊 6. Regional Anaesthesia

🦴 6.1 Spinal and Epidural Anaesthesia

• Spinal anaesthesia injects local anaesthetic into CSF, producing dense block.
• Epidural anaesthesia places catheter in epidural space for continuous/bolus dosing.
• Benefits: excellent analgesia, reduced systemic opioids, useful for lower limb, pelvic, obstetric and abdominal procedures.
• Risks: hypotension, urinary retention, post-dural puncture headache, failed block, nerve injury, infection, epidural haematoma.
• Contraindications: patient refusal, coagulopathy/anticoagulation, infection at site, severe hypovolaemia, raised ICP in some contexts.

🧠 6.2 High Spinal

• Excessive neuraxial block can cause hypotension, bradycardia, breathing difficulty, arm weakness and reduced consciousness.
• Mechanism: sympathetic blockade, venous pooling and high block affecting respiratory muscles.
• Management: call for help, airway/ventilation support, left tilt in pregnancy, vasopressors, fluids and prepare for intubation if needed.

💉 6.3 Peripheral Nerve Blocks

• Provide targeted analgesia and reduce opioid requirement.
• Examples: fascia iliaca block, femoral nerve block, brachial plexus block, TAP block.
• Risks: nerve injury, bleeding, infection, local anaesthetic systemic toxicity, block failure.
• Warn about limb numbness/weakness and protect anaesthetised limb from injury.

🚨 6.4 Local Anaesthetic Systemic Toxicity

• Occurs when local anaesthetic enters systemic circulation or excessive dose is used.
• Early symptoms: perioral tingling, metallic taste, tinnitus, dizziness, agitation.
• Severe toxicity: seizures, arrhythmias, cardiovascular collapse.
• Management: stop injection, call for help, airway/oxygenation, seizure control, lipid emulsion therapy according to local/AAGBI-style protocol, prolonged resuscitation if needed.

💊 7. Analgesia and Pain Management

🧠 7.1 Pain Types

🧰 7.2 Multimodal Analgesia

• Use different drug classes and techniques to reduce opioid burden.
• Paracetamol: useful baseline analgesic; watch liver disease/weight-based dosing.
• NSAIDs: anti-inflammatory; avoid/caution in AKI, CKD, GI bleed, heart failure, asthma sensitivity and high bleeding risk.
• Opioids: effective for severe pain but cause constipation, nausea, sedation, respiratory depression and delirium.
• Regional anaesthesia: nerve blocks, epidural, wound catheters.
• Neuropathic agents: gabapentinoids, duloxetine, amitriptyline in selected chronic/neuropathic pain.

🫁 7.3 Opioid Safety

• Assess sedation and respiratory rate, not just pain score.
• Prescribe laxatives and antiemetics when appropriate.
• Use lower starting doses in opioid-naïve, elderly, frail, OSA, renal impairment or respiratory disease.
• Opioid toxicity: pinpoint pupils, sedation, low respiratory rate, hypoxia/hypercapnia.
• Naloxone reverses opioid effect but can precipitate pain/withdrawal; titrate to restore ventilation, not necessarily full alertness.

⚠️ Safety pearl: A comfortable but drowsy patient with respiratory rate 6 is not “well analgesed” — they may be opioid toxic.

💧 8. IV Fluids and Perioperative Physiology

NICE CG174 covers IV fluid therapy in adults in hospital. It emphasises assessing fluid needs, prescribing the correct type and volume, and monitoring response rather than giving “routine fluids” automatically.

🧃 8.1 The 5 Rs of Fluid Therapy

🩺 8.2 Assessing Volume Status

• Hypovolaemia: tachycardia, hypotension, dry mucosa, low JVP, poor capillary refill, oliguria, high lactate.
• Hypervolaemia: raised JVP, oedema, crackles, hypoxia, weight gain, positive fluid balance.
• Use trends: BP, HR, urine output, lactate, creatinine, weight, fluid balance, bedside ultrasound where trained.
• Frailty, heart failure, CKD and sepsis make fluid assessment difficult.
• Fluid challenge should have a defined goal and review point.

🧪 8.3 Fluid Types

• Balanced crystalloids are commonly used for resuscitation and replacement.
• 0.9% sodium chloride can cause hyperchloraemic metabolic acidosis if large volumes are given.
• Dextrose solutions provide water, not effective intravascular resuscitation.
• Colloids have specific indications/risks and are not routine first-line resuscitation fluids.
• Blood products are needed for haemorrhagic shock rather than large volumes of crystalloid.

🧠 Exam pearl: Fluids are drugs. Prescribe indication, type, rate, volume, monitoring and stop/review point.

🫀 9. Critical Care: Shock

⚡ 9.1 Shock Types

🧯 9.2 Initial Shock Management

• ABCDE assessment and senior help.
• High-flow oxygen if hypoxic or critically ill.
• IV/IO access, bloods, lactate, cultures if infection suspected.
• Fluid bolus if hypovolaemia/distributive shock, with reassessment after each bolus.
• Blood products and haemorrhage protocol for bleeding.
• Vasopressors if persistent vasodilatory shock despite appropriate fluids.
• Treat the cause: antibiotics/source control, PCI, thrombolysis, chest decompression, pericardiocentesis, surgery.

💊 9.3 Vasopressors and Inotropes

• Noradrenaline is commonly first-line for septic vasodilatory shock.
• Adrenaline may be used in anaphylaxis, cardiac arrest and selected shock states.
• Dobutamine provides inotropic support in selected low-output states.
• Vasopressors require careful monitoring, ideally arterial line and central access in critical care settings.
• Extravasation can cause tissue injury; peripheral use should follow local emergency policy.

🚨 Safety pearl: A rising lactate is a warning sign, not a diagnosis. It may reflect hypoperfusion, sepsis, seizures, beta-agonists, liver dysfunction or severe work of breathing — interpret the whole patient.

🫁 10. Respiratory Failure and Ventilation

🧪 10.1 Type 1 vs Type 2 Respiratory Failure

🌬️ 10.2 Oxygen Therapy

• Oxygen is a treatment for hypoxaemia, not breathlessness alone.
• Target saturations depend on risk of hypercapnic respiratory failure.
• Excess oxygen can worsen CO₂ retention in susceptible COPD/OHS patients.
• Monitor response using saturations, respiratory rate, work of breathing and blood gases.

🫧 10.3 Non-Invasive Ventilation and CPAP

• CPAP provides continuous positive pressure, improves oxygenation and recruits alveoli.
• NIV provides inspiratory and expiratory pressure support, improving ventilation and CO₂ clearance.
• NIV is useful in COPD exacerbation with acidosis and selected OHS/chest wall/neuromuscular cases.
• CPAP is useful in cardiogenic pulmonary oedema and selected hypoxic respiratory failure.
• Contraindications/cautions: vomiting, inability to protect airway, facial trauma, severe agitation, untreated pneumothorax, haemodynamic instability.
• Failure signs: worsening acidosis, rising CO₂, exhaustion, reduced consciousness, persistent hypoxia.

🧰 10.4 Invasive Mechanical Ventilation

• Indications: airway protection, refractory hypoxaemia, ventilatory failure, severe shock, reduced consciousness, surgery.
• Ventilator settings include mode, tidal volume, respiratory rate, FiO₂, PEEP and pressure limits.
• Lung-protective ventilation uses lower tidal volumes to reduce ventilator-induced lung injury, especially in ARDS.
• PEEP improves oxygenation but can reduce venous return and blood pressure.
• Complications: barotrauma, volutrauma, ventilator-associated pneumonia, haemodynamic compromise, delirium, weakness.

🚨 10.5 Ventilated Patient Deterioration: DOPES

🚨 Exam pearl: If a ventilated patient suddenly deteriorates, disconnect from ventilator and hand-ventilate with 100% oxygen while checking tube, chest and equipment.

🧯 11. ICU Organ Support

🧠 11.1 Neurological Support

• Monitor GCS, pupils, sedation score, pain and delirium.
• Sedation should be targeted and reviewed; over-sedation prolongs ventilation and delirium.
• Daily sedation holds may be used where appropriate.
• Raised intracranial pressure management includes oxygenation, avoiding hypotension, head elevation, temperature control and specialist neurosurgical measures.

🫘 11.2 Renal Support

• AKI in ICU is common due to sepsis, shock, nephrotoxins, rhabdomyolysis and contrast.
• Monitor urine output, creatinine, potassium, acid-base status and fluid balance.
• Renal replacement therapy indications include refractory hyperkalaemia, severe acidosis, fluid overload, uraemic complications and some toxins.
• Continuous modalities are often used in haemodynamically unstable ICU patients.

🩸 11.3 Haematological and Coagulation Support

• Critical illness can cause anaemia, thrombocytopenia, DIC and coagulopathy.
• Major haemorrhage requires balanced blood product resuscitation, calcium monitoring, warming and source control.
• VTE prophylaxis is essential unless bleeding risk prohibits.
• Line-associated thrombosis and HIT should be considered when platelets fall unexpectedly.

🍽️ 11.4 Nutrition and Gut

• Critical illness causes catabolism and muscle loss.
• Enteral feeding is preferred when gut works and is safe.
• Refeeding syndrome risk occurs in malnourished patients; monitor phosphate, potassium, magnesium and thiamine.
• Stress ulcer prophylaxis is used selectively in high-risk patients.

🦠 11.5 Sepsis and Source Control

• Sepsis management requires antimicrobials plus source control.
• Potential sources: pneumonia, urinary, intra-abdominal, line, skin/soft tissue, CNS, bone/joint.
• Persistent vasopressor need or fever despite antibiotics should prompt search for undrained collection, resistant organism, wrong source or non-infective mimic.

🧠 12. Sedation, Delirium and ICU-Acquired Weakness

💤 12.1 Sedation

• Sedation goals: comfort, safety, synchrony with ventilation, procedures and reduced distress.
• Over-sedation prolongs ventilation and increases delirium risk.
• Common agents: propofol, midazolam, dexmedetomidine, opioids; choice depends on haemodynamics, organ function and clinical goal.
• Propofol infusion syndrome is rare but serious: metabolic acidosis, rhabdomyolysis, cardiac failure, hyperkalaemia.

🌀 12.2 ICU Delirium

• Risk factors: age, sepsis, hypoxia, pain, sleep deprivation, benzodiazepines, immobility, sensory impairment.
• Features: inattention, fluctuating consciousness, agitation or hypoactivity.
• Prevention: reorientation, sleep, mobilisation, glasses/hearing aids, pain control, reduce unnecessary sedation.
• Antipsychotics may be used for severe distress/risk but do not treat the underlying cause.

💪 12.3 ICU-Acquired Weakness

• Critical illness polyneuropathy/myopathy causes diffuse weakness and delayed weaning.
• Risk factors: sepsis, multi-organ failure, immobility, hyperglycaemia, steroids/neuromuscular blockers in some contexts.
• Prevention: early mobilisation, nutrition, glycaemic control and minimising sedation where safe.

🚨 13. Anaesthetic Emergencies

⚡ 13.1 Perioperative Anaphylaxis

• Triggers: neuromuscular blockers, antibiotics, chlorhexidine, latex, dyes, colloids and other agents.
• Features under anaesthesia may be hypotension, bronchospasm, tachycardia/bradycardia or cardiovascular collapse.
• Skin signs may be absent in severe perioperative reactions.
• Management: call for help, stop suspected trigger, 100% oxygen, IV adrenaline by experienced anaesthetic/critical care clinicians, aggressive fluids, vasopressor infusion if refractory, CPR if arrest.
• Take mast cell tryptase samples according to local protocol and refer for allergy investigation.

🔥 13.2 Malignant Hyperthermia

• Life-threatening hypermetabolic reaction triggered by volatile anaesthetics and suxamethonium in susceptible patients.
• Early signs: rapidly rising end-tidal CO₂, tachycardia, muscle rigidity, acidosis, hyperkalaemia.
• Later signs: hyperthermia, rhabdomyolysis, arrhythmia, renal failure.
• Management: stop triggering agents, call for MH trolley/help, dantrolene, 100% oxygen, active cooling, treat hyperkalaemia/acidosis, ICU care.
• Family history of anaesthetic death or malignant hyperthermia matters.

🫁 13.3 Laryngospasm and Bronchospasm

• Laryngospasm: reflex glottic closure causing airway obstruction, often during light anaesthesia or airway stimulation.
• Management: remove stimulus, jaw thrust, CPAP/100% oxygen, deepen anaesthesia, suxamethonium if severe.
• Bronchospasm: wheeze, high airway pressures, prolonged expiration, capnography changes.
• Management: 100% oxygen, deepen anaesthesia, bronchodilators, adrenaline if severe/anaphylaxis, exclude tube obstruction/pneumothorax.

🩸 13.4 Major Haemorrhage

• Recognise early: tachycardia, hypotension, falling Hb, high lactate, surgical field bleeding, drain output.
• Activate major haemorrhage protocol when needed.
• Use balanced blood products, calcium replacement, warming and tranexamic acid where appropriate.
• Stop the bleeding: pressure, surgery, endoscopy, interventional radiology.
• Avoid hypothermia, acidosis and coagulopathy.

🫀 13.5 Perioperative Cardiac Arrest

• Use ALS algorithm but treat reversible causes aggressively.
• Common perioperative causes: hypoxia, hypovolaemia/bleeding, hyperkalaemia, local anaesthetic toxicity, anaphylaxis, tension pneumothorax, tamponade, PE, high spinal.
• Capnography helps confirm CPR quality and tube position.
• In theatre, surgical causes may require immediate surgical action.

🚨 14. Critical Care Emergencies

🧪 15. Blood Gas and Acid-Base Interpretation

🧠 15.1 ABG/VBG Stepwise Approach

• Check pH: acidaemia or alkalaemia.
• Check PaCO₂: respiratory component.
• Check bicarbonate/base excess: metabolic component.
• Check oxygenation: PaO₂, saturation, FiO₂ and A-a gradient where relevant.
• Check lactate: shock, sepsis, seizures, beta-agonists, liver dysfunction.
• Check potassium, glucose and haemoglobin.
• Ask whether compensation is appropriate or whether there is a mixed disorder.

🚨 15.2 Critical Blood Gas Clues

• Severe acidaemia reduces cardiac contractility and vasopressor response.
• Rising CO₂ with drowsiness suggests ventilatory failure.
• High lactate plus hypotension suggests shock until proven otherwise.
• Metabolic acidosis plus hyperkalaemia occurs in AKI, DKA, rhabdomyolysis and tissue hypoperfusion.
• Normal oxygen saturation does not exclude hypercapnia.

🧠 Exam pearl: A VBG is often good for pH, CO₂ trend, lactate and electrolytes, but ABG is better when accurate oxygenation or A-a gradient matters.

🧓 16. Frailty, OSA and High-Risk Perioperative Patients

👴 16.1 Frailty

• Frailty predicts postoperative complications, delirium, prolonged stay and loss of independence.
• Assess baseline mobility, cognition, ADLs, falls, nutrition, social support and goals.
• Optimisation includes exercise/prehabilitation, nutrition, anaemia management, medication review and delirium prevention.
• Shared decision-making should include realistic recovery trajectory and possible need for rehab/care.

😴 16.2 Obstructive Sleep Apnoea

• OSA increases risk of difficult airway, hypoxia, opioid sensitivity and postoperative respiratory complications.
• Clues: snoring, witnessed apnoea, daytime sleepiness, obesity, large neck circumference, resistant hypertension.
• Use CPAP perioperatively if already prescribed and follow local/CPOC pathways.
• Minimise opioids where possible and monitor post-op oxygenation/sedation carefully.

🫀 16.3 Cardiac Risk

• Assess active cardiac conditions: unstable angina, decompensated heart failure, severe arrhythmia, severe valve disease.
• Functional capacity helps risk stratify.
• Emergency surgery may proceed with parallel optimisation and invasive monitoring.
• Postoperative myocardial injury may present silently, especially in older/frail patients.

🫁 16.4 Respiratory Risk

• COPD, asthma, smoking, obesity and OSA increase pulmonary complications.
• Optimise bronchodilators, treat infection, encourage smoking cessation and plan postoperative physiotherapy.
• Pain control after thoracic/abdominal surgery helps breathing and cough.

📚 17. OSCE / Exam Pearls

• Airway always comes before breathing, but oxygenation is the goal.
• Preoxygenation buys time during apnoea.
• Capnography confirms ventilation and helps detect tube displacement.
• Hypotension after induction is often vasodilation plus unrecognised hypovolaemia.
• OSA patients are sensitive to sedatives and opioids.
• Fluids are drugs: prescribe indication, type, volume, rate and review.
• Neuraxial anaesthesia plus anticoagulation requires strict timing rules.
• Sudden high airway pressure under anaesthesia: think bronchospasm, tube obstruction, pneumothorax or biting.
• Perioperative anaphylaxis may not show rash.
• A ventilated patient who suddenly deteriorates needs tube, chest and equipment checked immediately.
• In shock, ask: volume, pump, pipes or obstruction?
• Lactate trend matters more than a single number.

📌 18. Quick Differentials Table

📚 References

• NICE. Routine preoperative tests for elective surgery. NG45.
• NICE. Intravenous fluid therapy in adults in hospital. CG174.
• Centre for Perioperative Care. Preoperative Assessment and Optimisation for Adult Surgery.
• Centre for Perioperative Care. Perioperative care of people with diabetes undergoing surgery.
• Resuscitation Council UK. Anaphylaxis guidance and peri-operative anaphylaxis algorithm.
• Resuscitation Council UK. 2025 Special circumstances guidelines for cardiac arrest and reversible causes.
• Difficult Airway Society, Royal College of Anaesthetists, Association of Anaesthetists and Faculty of Intensive Care Medicine guidance should be checked for specialist airway, anaesthetic and ICU pathways.
• Local anaesthetic, critical care, major haemorrhage, sepsis, diabetes, anticoagulation and perioperative policies should always be followed.

⚠️ Disclaimer

This article is for medical education and exam revision. Clinical decisions should follow current local anaesthetic, perioperative, critical care, airway, resuscitation, sepsis, anticoagulation, diabetes, analgesia, antimicrobial and major haemorrhage protocols, formularies, senior advice and national guidance. Anaesthetic and critical care emergencies such as failed airway, perioperative anaphylaxis, malignant hyperthermia, local anaesthetic systemic toxicity, major haemorrhage, septic shock, ARDS, severe hyperkalaemia and ventilated patient deterioration require urgent senior input.