Anaesthesia

Definition & the Chain of Survival

Cardiopulmonary resuscitation (CPR) is the emergency support of the circulation and breathing in a person in cardiac arrest. Survival depends on the ‘chain of survival’: early recognition and calling for help, early CPR, early defibrillation, and post-resuscitation care. Basic life support (BLS) maintains oxygenation and circulation with no (or minimal) equipment until advanced help arrives.

The Adult BLS Sequence

On finding a collapsed person: ensure safety, check responsiveness, and open the airway (head-tilt/chin-lift) while checking for normal breathing (look, listen, feel for up to 10 seconds). If not breathing normally, call for help / the emergency team and get a defibrillator, and start chest compressions.

High-Quality Chest Compressions

Effective compressions are the priority: centre of the chest, depth 5–6 cm, rate 100–120/min, allowing full recoil, and minimising interruptions. Combine with rescue breaths at a ratio of 30 compressions : 2 breaths (for a trained rescuer with the means to ventilate). Apply an automated external defibrillator (AED) as soon as it arrives and follow its prompts.

When to Use It

BLS is started for anyone unresponsive and not breathing normally. It buys time — maintaining some oxygen delivery to the brain and heart — until defibrillation and advanced life support can be delivered, which are what most often restart the heart.

The Importance of Bystander CPR

The single greatest determinant of survival from an out-of-hospital cardiac arrest, after the arrest itself, is whether immediate bystander CPR is given, because the chance of survival falls by roughly ten per cent for every minute that passes without chest compressions and defibrillation. This is why training the public in basic life support, and reducing the barriers to acting, are public-health priorities, and why even compression-only CPR by an untrained bystander is far better than doing nothing: keeping some blood flowing to the brain and heart preserves the chance that a subsequent defibrillation will succeed. The whole design of modern resuscitation — simple recognition, an emphasis on early compressions, and widely-available automated defibrillators — is aimed at getting effective help to the patient in the first few minutes.

Compression-Only CPR & Its Place

For the untrained or unwilling bystander, or where there is a barrier to giving rescue breaths, compression-only CPR — continuous chest compressions without ventilation — is recommended and is far better than no CPR at all, because in the first minutes of a sudden cardiac arrest the blood still contains oxygen and the priority is to keep it circulating. Trained rescuers with the means to ventilate use the conventional thirty-compressions-to-two-breaths ratio, but the overarching message of modern guidelines is to push hard, push fast and minimise interruptions, since the quality and continuity of compressions matter more than the addition of breaths in the earliest phase of resuscitation.

• CPR supports circulation/breathing in cardiac arrest; chain of survival = early recognition, CPR, defibrillation, post-arrest care.
• BLS: safety, check response, open airway, check breathing (≤10 s); if abnormal → call for help + AED, start compressions.
• High-quality compressions: 5–6 cm, 100–120/min, full recoil, minimal interruptions; 30:2 with breaths.
• Agonal gasping is NOT normal breathing — start CPR.
• BLS buys time until defibrillation/ALS restart the heart.

Advanced Life Support

Advanced (cardiac) life support (ALS/ACLS) builds on BLS with a defibrillator, drugs, advanced airway and treatment of reversible causes. The team continues high-quality CPR while the rhythm is assessed and classified as shockable or non-shockable, which determines the pathway.

Shockable vs Non-shockable

Shockable rhythms — ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT) — are treated with immediate defibrillation and CPR; adrenaline and amiodarone are added for refractory cases. Non-shockable rhythms — pulseless electrical activity (PEA) and asystole — are not shocked; they are treated with CPR and adrenaline, with the focus on finding and treating a reversible cause.

Drugs & Reversible Causes

Adrenaline is given every 3–5 minutes (immediately in non-shockable arrest; after the third shock in shockable). Amiodarone is given for shock-refractory VF/VT. Throughout, the team searches for and treats the reversible causes — the ‘4 Hs and 4 Ts’: Hypoxia, Hypovolaemia, Hypo-/hyperkalaemia (& metabolic), Hypothermia; Tension pneumothorax, Tamponade, Toxins, Thrombosis (coronary/pulmonary).

Advanced Airway & Team Working

During advanced life support the airway is secured — by a supraglottic device or tracheal intubation — to allow continuous chest compressions without the pauses needed for mouth-to-mask or bag-mask ventilation, and continuous waveform capnography is used to confirm tube placement, to gauge the quality of compressions, and to detect the return of spontaneous circulation as a sudden rise in end-tidal carbon dioxide. Equally important is good team working: a team leader coordinates the resuscitation, allocates roles, keeps track of the cycles of CPR and rhythm checks and the timing of drugs, and ensures the reversible causes are being addressed, because a well-led, well-drilled team delivers the high-quality, minimally-interrupted CPR on which outcome depends.

• ALS = BLS + defibrillator, drugs, advanced airway, treating reversible causes; assess rhythm as shockable/non-shockable.
• Shockable (VF, pulseless VT) → defibrillate + CPR; adrenaline & amiodarone if refractory.
• Non-shockable (PEA, asystole) → CPR + adrenaline (no shock); focus on reversible cause.
• Adrenaline every 3–5 min; amiodarone for refractory VF/VT.
• Reversible causes — 4 Hs (hypoxia, hypovolaemia, hypo/hyperkalaemia, hypothermia) & 4 Ts (tension pneumothorax, tamponade, toxins, thrombosis).

Oxygen Therapy

Oxygen therapy is the administration of oxygen at a concentration greater than that of air to treat or prevent hypoxaemia. It is a drug — given for an indication, at a dose (concentration/flow), and with awareness of hazards. The device is chosen for the concentration required and whether it must be fixed or variable.

Variable vs Fixed Performance

Variable-performance devices (nasal cannulae, simple mask) deliver an oxygen concentration that depends on the patient’s breathing (their inspiratory flow dilutes the oxygen with air), so the exact FiO₂ is unknown. Fixed-performance devices — the Venturi mask — entrain a constant proportion of air to deliver a precise, known concentration regardless of breathing, important when a controlled dose is needed (e.g. COPD).

Hazards

Oxygen has hazards: oxygen toxicity (prolonged high concentrations cause pulmonary damage and, in neonates, retinopathy); absorption atelectasis; CO₂ retention in some patients with chronic type-2 respiratory failure (give controlled oxygen via a Venturi mask, titrated to a target saturation); and it supports combustion (fire risk).

Choosing a Device

Match the device to the need: nasal cannulae for comfort and low requirements, a non-rebreathing reservoir mask for a critically ill/hypoxic patient needing high concentration, and a Venturi mask for a precise, controlled concentration. Always titrate to a target oxygen saturation.

Physiology & Prescribing Oxygen

Oxygen therapy corrects hypoxaemia by raising the alveolar and hence arterial oxygen tension, improving the saturation of haemoglobin and the delivery of oxygen to the tissues, and it is one of the commonest treatments given in acute care. The modern principle is that it should be prescribed and titrated to a target saturation like any other drug rather than given routinely at a fixed high flow, because both too little and too much oxygen can be harmful — hypoxaemia damages the tissues, while unnecessary hyperoxia carries its own risks and, in the carbon-dioxide-retaining patient, can be dangerous. Choosing the device and flow to achieve the target saturation, and reviewing the response, is therefore central to safe oxygen therapy.

Humidification & High-Flow Oxygen

Oxygen drawn from a cylinder or wall supply is dry and cold, and prolonged administration of dry oxygen can dry the airway secretions and mucosa, so humidification is added for longer-term or high-flow therapy. A notable modern development is high-flow nasal oxygen, which delivers warmed, humidified oxygen at very high flow rates through wide-bore nasal cannulae, allowing a high and relatively predictable inspired concentration, some positive airway pressure and improved comfort; it has found a role in acute hypoxaemic respiratory failure and in supporting oxygenation around the time of intubation. These developments reflect the same principle of matching the device to the concentration, flow and duration of oxygen the patient needs.

• Oxygen is a drug: give for an indication, at a dose, titrated to a target saturation, aware of hazards.
• Variable-performance (nasal cannulae, simple mask): FiO₂ depends on the patient’s breathing (unknown).
• Fixed-performance (Venturi): precise, known concentration — for controlled therapy (COPD).
• Non-rebreathing reservoir mask: high concentration for the critically ill/hypoxic.
• Hazards: oxygen toxicity, absorption atelectasis, CO₂ retention (type-2 failure), fire.

Principles of Acute Pain Management

Good postoperative pain management improves comfort, allows early mobilisation and breathing, reduces complications, and improves recovery. Modern practice is multimodal — combining drugs from different classes and regional techniques so that each is used at a lower dose, giving better analgesia with fewer side-effects (especially opioid-sparing).

The WHO Analgesic Ladder

The WHO analgesic ladder (originally for cancer pain, widely applied) matches analgesia to severity: Step 1 — non-opioids (paracetamol, NSAIDs) ± adjuvant; Step 2 — weak opioids (codeine, tramadol) + non-opioid; Step 3 — strong opioids (morphine) + non-opioid. Adjuvants (e.g. for neuropathic pain) are added at any step. For acute postoperative pain the ladder is often used in reverse (starting strong and stepping down).

Routes & Techniques

Analgesia is delivered by many routes: oral (when tolerated), intravenous (including patient-controlled analgesia, PCA), and regional techniques (epidural, nerve blocks, local infiltration) which provide excellent, opioid-sparing analgesia. Pain is assessed regularly (a pain score) and treatment adjusted.

Consequences of Poor Pain Control

Effective acute pain relief is not merely a matter of comfort but has real effects on recovery and complications: poorly-controlled pain prevents patients from breathing deeply and coughing, predisposing to atelectasis and chest infection, discourages the early mobilisation that reduces the risk of venous thromboembolism, raises the surgical stress response, and is associated with the later development of chronic post-surgical pain. Good analgesia, by contrast, allows early mobilisation, physiotherapy and feeding, and is a cornerstone of enhanced-recovery programmes. This is why pain is assessed regularly as a vital sign and treated proactively with a planned, multimodal regimen rather than reactively, and why the balance is struck between adequate analgesia and the side-effects of the drugs used.

• Postoperative analgesia aids comfort, mobilisation, breathing & recovery; approach is multimodal & opioid-sparing.
• WHO ladder: Step 1 non-opioids ± adjuvant → Step 2 weak opioids + non-opioid → Step 3 strong opioids + non-opioid.
• Adjuvants added at any step; acute pain often uses the ladder in reverse (start strong, step down).
• Routes: oral, IV (incl. PCA), regional (epidural/nerve blocks/infiltration — opioid-sparing).
• Assess pain regularly; balance under-treatment against opioid side-effects.

Overview

The main analgesic drug groups — paracetamol, NSAIDs and opioids — act by different mechanisms and are combined (multimodal analgesia) so each can be used at a lower, safer dose. Adjuvants are added for specific pain types.

Paracetamol & NSAIDs

Paracetamol is a safe, effective basic analgesic and antipyretic (central action; hepatotoxic in overdose) — a cornerstone of multimodal analgesia. NSAIDs (e.g. ibuprofen, diclofenac) inhibit cyclo-oxygenase (COX), reducing prostaglandins — good for inflammatory and musculoskeletal pain and strongly opioid-sparing, but with important cautions: gastrointestinal ulceration/bleeding, renal impairment, bronchospasm (in sensitive asthmatics), and antiplatelet effects.

Opioids

Opioids (μ-receptor agonists) are the mainstay for moderate–severe pain: weak (codeine, tramadol) and strong (morphine, fentanyl, oxycodone). They provide powerful analgesia but share class side-effects: respiratory depression (the main danger), sedation, nausea/vomiting, constipation, pruritus, miosis, and, with long-term use, tolerance and dependence. Respiratory depression is reversed by naloxone.

Adjuvants

Adjuvant analgesics target specific pain: anti-neuropathic agents (gabapentinoids, tricyclic antidepressants) for neuropathic pain, ketamine (NMDA antagonist) for severe/opioid-resistant pain, and local anaesthetics (regional techniques). These broaden multimodal analgesia beyond the three main groups.

Combining the Groups Rationally

The rationale for combining analgesics is that each group has a ceiling of usefulness and its own side-effects, so relying on any one drug at high dose maximises its harms; by combining paracetamol, an anti-inflammatory and an opioid, each acting by a different mechanism, good analgesia is achieved at lower, safer doses of each. Paracetamol and the NSAID form a sensible baseline for almost all patients in whom they are not contraindicated, providing genuine opioid-sparing, while the opioid is titrated on top for the more severe pain and weaned as the pain settles. Adjuvants are added for pain that does not respond well to this combination, particularly neuropathic pain, so that the regimen is tailored to the type as well as the severity of the pain.

Cautions & Contraindications in Summary

Each analgesic group carries cautions that shape its safe use: paracetamol is very safe at normal doses but dangerous in overdose because of hepatotoxicity, so the total daily dose is respected; NSAIDs are avoided or used cautiously in renal impairment, in those at risk of gastrointestinal bleeding, in aspirin-sensitive asthma and in certain cardiac patients; and opioids cause dose-dependent respiratory depression and sedation and must be titrated and monitored, with particular care in the elderly, the patient with sleep apnoea and the opioid-naïve. Knowing these limits is what allows the groups to be combined safely, each contributing analgesia while its individual dose and its particular risks are kept in check.

• Main analgesics: paracetamol, NSAIDs, opioids — different mechanisms, combined (multimodal) for lower doses.
• Paracetamol: safe basic analgesic/antipyretic (hepatotoxic in overdose).
• NSAIDs: COX inhibition, opioid-sparing; cautions — GI bleeding, renal impairment, asthma, antiplatelet.
• Opioids (weak/strong): powerful; respiratory depression (main danger, reversed by naloxone), sedation, nausea, constipation, dependence.
• Adjuvants: gabapentinoids/TCAs (neuropathic), ketamine, local anaesthetics.