1.1 The ABCDE Approach, Adult Resuscitation & Shock
Key Takeaways
Systematic ABCDE assessment ensures immediate recognition and prioritized management of life-threatening airway, ventilatory, and circulatory compromise before proceeding to secondary diagnostics.
Resuscitation Council UK (RCUK) adult advanced life support (ALS) distinguishes shockable rhythms (VF/pVT) from non-shockable rhythms (asystole/PEA), with adrenaline 1 mg and amiodarone 300 mg delivered strictly after the 3rd shock in VF/pVT.
Non-shockable cardiac arrest requires immediate administration of adrenaline 1 mg IV/IO upon obtaining vascular access, followed by rapid identification and correction of the reversible 4 Hs and 4 Ts.
Shock is categorized into hypovolaemic, cardiogenic, obstructive, and distributive mechanisms; neurogenic shock uniquely presents with hypotension accompanied by inappropriate bradycardia and warm extremities due to loss of sympathetic tone.
The ABCDE Approach, Adult Resuscitation & Shock
In acute clinical practice, the systematic ABCDE (Airway, Breathing, Circulation, Disability, Exposure) approach provides a structured, reproducible algorithm to assess and resuscitate deteriorating patients. The core principle of ABCDE is that life-threatening abnormalities must be treated immediately upon recognition before progressing to the next step.
The Systematic ABCDE Assessment Framework
| Assessment Step | Primary Clinical Targets | Immediate Emergency Interventions |
|---|---|---|
| A – Airway | Patency, vocalisation, stridor, secretions, foreign bodies | Head-tilt chin-lift or jaw thrust (trauma/c-spine); suction; oropharyngeal (Guedel) or nasopharyngeal airway; definitive endotracheal intubation |
| B – Breathing | Respiratory rate, SpO2, chest expansion symmetry, percussion, auscultation | High-flow oxygen (15 L/min via non-rebreathe reservoir mask); target SpO2 94–98% (or 88–92% in hypercapnic risk); needle decompression for tension pneumothorax |
| C – Circulation | Pulse rate and rhythm, blood pressure, capillary refill time, skin temperature | Two wide-bore IV cannulae (14G or 16G) or intraosseous (IO) access; direct haemorrhage control; 500 mL balanced crystalloid bolus over <15 min; crossmatch blood |
| D – Disability | AVPU or Glasgow Coma Scale (GCS), pupillary size/reactivity, blood glucose | Capillary blood glucose (rule out hypoglycaemia); IV 10–20% glucose if <4.0 mmol/L; IV naloxone for opioid toxidrome; intubate if GCS ≤ 8 |
| E – Exposure | Head-to-toe examination, rashes, urticaria, trauma, core temperature | Remove clothing while preserving dignity; active warming (Bair Hugger) to prevent hypothermia; inspect surgical wounds, drains, and calves |
Airway with Cervical Spine Protection
A patient who can speak clearly in full sentences has a patent airway. Gurgling indicates liquid secretions or vomit, snoring indicates pharyngeal obstruction by the tongue, and inspiratory stridor indicates critical upper airway obstruction. In suspected trauma, maintain in-line spinal stabilization and avoid head-tilt; perform a jaw thrust instead.
- Oropharyngeal Airway (Guedel): Sized from the incisors to the angle of the mandible. Insert upside down toward the hard palate and rotate 180° upon entering the oropharynx (adults only). Only tolerate in deeply unconscious patients (loss of gag reflex).
- Nasopharyngeal Airway (NPA): Sized 6–7 mm in adults. Lubricate and insert along the floor of the nasal cavity. Contraindication: Suspected basal skull fracture (periorbital bruising/panda eyes, battle sign, CSF rhinorrhoea/otorrhoea), where cribriform plate disruption risks intracranial placement.
Breathing & Critical Thoracic Emergencies
Normal adult respiratory rate is 12–20 breaths/min; tachypnoea (>20) is the most sensitive early marker of physiological decompensation.
Important
Tension Pneumothorax Identification: Ipsilateral hyper-resonance, absent breath sounds, respiratory distress, hypotension, and contralateral tracheal deviation. Do not delay treatment for a chest radiograph. Immediately perform emergency needle decompression using a 14G/16G cannula in the 2nd intercostal space mid-clavicular line (or 4th/5th intercostal space anterior axillary line), followed immediately by formal tube thoracostomy in the triangle of safety (lateral border of pectoralis major, anterior border of latissimus dorsi, apex below axilla, 5th intercostal space horizontal to nipple).
Circulation & Vascular Access
Assess peripheral perfusion via capillary refill time (normal <2 seconds), pulse volume, blood pressure, and core-peripheral temperature gradient. If venous access cannot be achieved within 2 attempts or 90 seconds in an unstable or arrested patient, establish intraosseous (IO) access into the proximal tibia or proximal humerus. Fluid resuscitation should utilize balanced crystalloids (e.g., Hartmann's solution or Plasma-Lyte); avoid unbuffered 0.9% normal saline in large volumes due to the risk of hyperchloraemic metabolic acidosis.
Resuscitation Council UK (RCUK) Adult ALS Algorithm
The RCUK 2025 adult ALS guideline (published October 2025) made no major changes to the 2021 algorithm: high-quality compressions with minimal interruption and early defibrillation remain the priorities, with more emphasis on effective oxygenation and ventilation.
Cardiac arrest is diagnosed when a patient is unresponsive with absent or abnormal breathing (agonal gasps). Rescuers should assess carotid pulse for no more than 10 seconds. Upon confirmation, call the cardiac arrest team (2222 in UK hospitals) and commence high-quality cardiopulmonary resuscitation (CPR 30:2; depth 5–6 cm, rate 100–120 bpm, full chest recoil, minimal interruptions).
Shockable Rhythms: Ventricular Fibrillation (VF) and Pulseless VT (pVT)
- Deliver 1 unsynchronised DC shock (150–200 J biphasic or 360 J monophasic).
- Immediately resume CPR 30:2 for 2 minutes without pausing to check pulse or rhythm.
- After 2 minutes, reassess rhythm. If persistent VF/pVT, deliver Shock 2, immediately resume CPR for 2 minutes.
- If still in VF/pVT at the next rhythm check, deliver Shock 3, immediately resume CPR, and administer Adrenaline 1 mg IV/IO and Amiodarone 300 mg IV/IO.
- Administer further Adrenaline 1 mg every 3–5 minutes (alternate cycles). If VF/pVT persists after Shock 5, administer a second dose of Amiodarone 150 mg IV/IO.
Non-Shockable Rhythms: Pulseless Electrical Activity (PEA) & Asystole
- Confirm non-shockable rhythm; do not defibrillate.
- Administer Adrenaline 1 mg IV/IO immediately as soon as vascular access is established.
- Continue CPR 30:2 for 2-minute cycles; re-administer Adrenaline 1 mg every 3–5 minutes (alternate cycles).
- Search aggressively for reversible causes: the 4 Hs and 4 Ts.
Reversible Causes: The 4 Hs and 4 Ts
- Hypoxia: Ensure high-flow 100% O2, verify tube placement, check chest rise.
- Hypovolaemia: Rapid IV crystalloid or uncrossmatched O-negative blood; control bleeding.
- Hyperkalaemia / Hypokalaemia / Metabolic: Administer 10 mL 10% calcium chloride IV for hyperkalaemia; treat severe acidosis.
- Hypothermia: Active core rewarming; consider cardiopulmonary bypass if severe (<30°C).
- Tension pneumothorax: Immediate needle decompression followed by chest drain insertion.
- Tamponade (cardiac): Immediate ultrasound-guided pericardiocentesis or thoracotomy.
- Toxins: Administer specific antidotes (e.g., naloxone for opioids, DigiFab for digoxin).
- Thrombosis (coronary or pulmonary): Urgent primary PCI for MI; consider systemic thrombolysis (e.g., alteplase) for suspected massive PE. If thrombolysis is given during CPR, continue resuscitation for at least 60–90 minutes to allow drug efficacy.
Shock Classification & Hemodynamics
Shock is defined as acute systemic hypoperfusion resulting in inadequate cellular oxygen delivery and end-organ dysfunction. Clinical markers include hypotension (SBP <90 mmHg or MAP <65 mmHg), tachycardia, tachypnoea, oliguria (<0.5 mL/kg/h), altered mental status, and elevated arterial or venous lactate (>2.0 mmol/L).
| Shock Category | Primary Aetiologies | Preload (CVP / JVP) | Systemic Vascular Resistance (SVR) | Cardiac Output (CO) | Clinical Perfusion Examination |
|---|---|---|---|---|---|
| Hypovolaemic | Haemorrhage, severe burns, fluid loss (diarrhoea, vomiting, DKA) | Decreased (flat neck veins) | Increased (compensatory vasoconstriction) | Decreased | Cold, pale, clammy peripheries; prolonged capillary refill >2s |
| Cardiogenic | Massive acute MI, acute mitral regurgitation, severe decompensated heart failure | Increased (elevated JVP, pulmonary crackles) | Increased (compensatory vasoconstriction) | Severely Decreased | Cold, clammy, cyanotic peripheries; gallop rhythm (S3); pulmonary oedema |
| Obstructive | Tension pneumothorax, massive pulmonary embolism, cardiac tamponade | Increased (distended neck veins) | Increased (compensatory vasoconstriction) | Decreased | Distended neck veins; absent unilateral breath sounds (tension PTX) or pulsus paradoxus (tamponade) |
| Distributive | Sepsis, anaphylaxis, neurogenic shock, Addisonian crisis | Decreased or Normal | Severely Decreased (pathological vasodilation) | Increased (early/hyperdynamic) or Normal | Warm, flushed peripheries in early sepsis; bounding pulse; wide pulse pressure |
Note
Neurogenic Shock Clinical Hallmark: Occurs with high spinal cord injury (typically at or above T6). Interruption of descending sympathetic autonomic pathways causes uncontrolled peripheral vasodilation and loss of cardiac accelerator tone. Unlike all other forms of distributive shock, neurogenic shock characteristically presents with hypotension accompanied by bradycardia (or inappropriate normal heart rate) and warm, dry extremities.
A 62-year-old man in the coronary care unit suffers a monitored cardiac arrest. The monitor shows ventricular fibrillation. CPR is commenced, and a biphasic shock is delivered. CPR is resumed for 2 minutes. The rhythm remains ventricular fibrillation, and a second shock is delivered. Following another 2 minutes of CPR, the rhythm check confirms persistent ventricular fibrillation. A third shock is administered. What is the most appropriate immediate pharmacological therapy to administer following this third shock?
Atropine 3 mg IV and adrenaline 1 mg IV
Amiodarone 150 mg IV as a single agent
Adrenaline 1 mg IV and amiodarone 300 mg IV
Adrenaline 1 mg IV alone with delayed amiodarone until after the fourth shock
A 28-year-old unrestrained driver is brought to the resuscitation room following a high-speed collision. He is severely breathless, agitated, and diaphoretic. His blood pressure is 74/42 mmHg, heart rate is 138 bpm, and respiratory rate is 36 breaths/min. On physical examination, breath sounds are absent across the entire right hemithorax with marked hyper-resonance to percussion. The trachea is visibly deviated toward the left clavicle. What is the most appropriate immediate management?
Perform ultrasound-guided subxiphoid pericardiocentesis
Immediate needle decompression of the affected hemithorax
Perform emergency blind endotracheal intubation
Transfer immediately to radiology for an urgent erect chest X-ray
A 32-year-old motorcyclist sustains a traumatic spinal cord injury with acute complete motor and sensory transection at the T3 level. In the emergency department, his blood pressure is 76/40 mmHg, heart rate is 46 bpm, respiratory rate is 16 breaths/min, and core temperature is 36.6°C. His extremities are warm and well perfused, and his capillary refill time is 1.5 seconds. What is the primary underlying physiological mechanism responsible for this patient's shock state?
Loss of sympathetic autonomic vasomotor and cardiac accelerator tone causing neurogenic shock
Systemic inflammatory response syndrome causing early hyperdynamic septic shock
Occult intra-abdominal haemorrhage producing hypovolaemic shock
Severe myocardial contusion causing cardiogenic pump failure
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