01Core principlesThe concepts and mechanisms needed to understand the subject.
ABCDE is a method for allocating attention under time pressure. Airway obstruction can prevent all subsequent oxygen delivery, while profound hypoventilation may worsen cerebral function even when oxygen is being administered. The order therefore reflects interacting physiological threats, rather than a requirement to finish documenting one organ system before anyone else can act. Several team members can perform different tasks simultaneously while one person maintains an overview.
The initial objective is to reverse dangerous physiology sufficiently to permit diagnosis and definitive treatment. A complete history, formal scoring system or blood result may be valuable later but must not defer airway opening or assisted ventilation. A normal single observation is weak reassurance when the patient is deteriorating. Previous values, oxygen requirements and response to intervention often reveal the trajectory more clearly.
Key points
- Identify an airway or ventilation problem immediately; an oxygen saturation number cannot establish airway safety.
- Treat each life-threatening abnormality as it is found, then continue the assessment and return to reassess.
- Ask for experienced help early while assigning monitoring, vascular access, and documentation to other team members.
- Record respiratory rate and inspired oxygen together with saturation; supplemental oxygen can conceal deteriorating ventilation.
- Use blood pressure with capillary refill, skin temperature, mentation and urine output to judge perfusion.
- Check glucose during disability assessment and repeat ABC assessment after any new reduction in consciousness.
02Mechanisms and patternsImportant relationships and how to distinguish them.
Listen for snoring, gurgling or stridor and assess whether the patient can speak. Silence with respiratory effort can represent complete obstruction. Suction secretions, open the airway and obtain skilled assistance when simple manoeuvres fail.
Inspect respiratory effort, symmetry, rate and depth; listen for air entry and wheeze. A patient who becomes quieter after sustained distress may be exhausting rather than recovering, particularly if consciousness or tidal volume falls.
Combine pulse, blood pressure, peripheral perfusion and mental state. A young person may maintain blood pressure during significant volume loss, whereas chronic hypertension can make an apparently ordinary pressure inadequate for that individual.
Record conscious level, pupils and bedside glucose after addressing oxygenation and perfusion. Look for seizure activity, temperature disturbance, bleeding, rash and concealed injuries, while maintaining dignity and preventing unnecessary heat loss.
03Interpreting evidenceInformation, measurements and their limitations.
Consider the information, its meaning and its limitations before deciding what follows.
- 01
Continuous bedside monitoring - Why
- Establish the physiological trajectory during treatment and transfer.
- Interpretation and limitations
- Attach ECG, oximetry and repeated blood-pressure measurement early. Motion and poor perfusion can distort readings, so a displayed number must be checked against the actual patient.
- 02
Blood gas with glucose and lactate - Why
- Distinguish ventilation failure, metabolic disturbance and impaired perfusion.
- Interpretation and limitations
- An arterial sample is useful when oxygenation or carbon dioxide measurement will change support. A venous gas can identify substantial acidaemia but cannot substitute for arterial oxygen tension.
- 03
Focused ECG and laboratory sampling - Why
- Investigate likely reversible causes without interrupting immediate treatment.
- Interpretation and limitations
- A twelve-lead ECG may expose infarction or arrhythmia; electrolytes, haemoglobin and renal function refine treatment. Draw urgent samples alongside cannulation rather than delaying resuscitation to obtain a complete panel.
- 04
Targeted imaging after stabilisation - Why
- Answer a defined anatomical question that changes the next intervention.
- Interpretation and limitations
- Portable chest imaging or bedside ultrasound may help identify pulmonary oedema or pneumothorax. An unstable patient should not leave effective resuscitation merely to obtain a more comprehensive diagnostic picture.
04Applied reasoningWorked examples connecting principles to decisions.
01Worked caseDrowsiness after an opioid doseA postoperative adult is difficult to rouse, snores, breathes six times per minute, and has SpO2 95% while receiving oxygen.+
- 1Interpret snoring as partial upper-airway obstruction and the low respiratory rate as inadequate ventilation; the saturation does not rule out dangerous carbon dioxide retention.
- 2Summon urgent help, open and support the airway, and provide assisted bag-mask ventilation with oxygen if breathing remains inadequate while monitoring is attached.
- 3Check glucose, pupils and the medication record in parallel. Recent opioid exposure supports toxicity, but persistent asymmetry, seizure activity or shock requires another explanation.
- 4Use appropriately titrated opioid reversal with experienced support when indicated, then verify sustained spontaneous ventilation, airway patency and improved conscious level before reducing assistance.
- 5Continue close observation because the opioid may outlast reversal, and arrange an explicit analgesia and monitoring plan instead of simply returning the patient to routine observations.
02Circulatory branchSuspected volume loss with hypoperfusionThe patient has cool peripheries, delayed capillary refill, falling pressure and a history suggesting gastrointestinal fluid loss.+
- 1Obtain vascular access and assess for bleeding, cardiac congestion and other explanations before assuming that every hypotensive patient needs the same volume.
- 2Use a measured crystalloid challenge when indicated and reassess circulation and respiratory findings immediately afterwards; choose the disease-specific regimen when sepsis or haemorrhage is suspected.
- 3If perfusion does not improve or crackles and breathlessness appear, stop automatic repeated boluses and request senior assessment for alternative circulatory support.
03Handover and reassessmentMaintaining control after initial improvementThe initial airway or circulatory threat improves but the cause and required destination remain unresolved.+
- 1Repeat assessment from airway onward, recording which abnormalities improved and which persist rather than treating a single improved observation as recovery.
- 2Provide a structured handover containing the physiological trend, actual treatments and times, response, working diagnosis and the next required decision.
- 3Agree who will review the patient, how frequently observations are needed, and what specific change requires immediate re-escalation during transfer or ward care.
05Relevant medicines and safetySpecific regimens and precautions where medicines are relevant.
Oxygen
For immediate critical illness, give oxygen through a reservoir mask, usually at 15 L/min, then titrate to SpO2 94–98%, or 88–92% where hypercapnic respiratory failure risk applies once reliable assessment is available.Oxygen does not correct obstructed air entry or inadequate ventilation; obtain blood gases when hypercapnia is possible and reduce unnecessary excess once a reliable target can be maintained.
06Checking understandingVerify the reasoning, revisit uncertainties and apply feedback.
- After airway intervention, confirm unobstructed air movement and visible chest rise rather than assuming correct equipment position means adequate ventilation.
- Repeat respiratory rate, conscious level and oxygen requirement after analgesics, sedatives or any deterioration; saturation alone is an incomplete safety measure.
- Reassess perfusion after each circulatory intervention using the same clinical observations, noting both improvement and signs of fluid intolerance.
- Chart observation frequency and escalation responsibility explicitly; a changing pattern requires review even when an aggregate early warning score seems modest.
07Special situationsVariants, exceptions and circumstances that change the usual approach.
Pregnancy and positioning
Later pregnancy can impair venous return when supine. Seek obstetric support and relieve aortocaval compression while preserving access for effective resuscitation.
Parallel team actions
A named leader can direct an airway assistant, circulation clinician and recorder simultaneously, preventing repeated assessments from displacing necessary interventions.
Communication impairment
Aphasia, deafness or a language barrier can resemble failure to respond. Check baseline communication while still investigating a genuinely new physiological deterioration.
Treatment limitations
A documented decision concerning CPR does not by itself prohibit oxygen, analgesia, antibiotics or other active treatment. Clarify the agreed goals and specific escalation limits.
08Common pitfallsFrequent interpretation and management errors.
- 01
Do not complete a long history before correcting an obvious airway obstruction or failure of ventilation in a deteriorating person.
- 02
Do not mistake an improving oxygen saturation after oxygen administration for recovery of respiratory drive or clearance of carbon dioxide.
- 03
Do not treat the sequence as a reason to postpone parallel cannulation, emergency calls or preparation of urgently needed equipment.
- 04
Do not transfer responsibility with the phrase stable now; communicate the cause of concern, treatment response and unresolved physiological risks.