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The ABCDE approach is used for performing an initial systematic assessment of any critically unwell or deteriorating patient, and intervening as necessary. Getting called to see unwell patients is part of the job of a junior doctor so it’s worth having a system in place! This method involves ordered examination, investigation and intervention, focusing on each major body system in turn. Any problems are addressed as they are identified with the patient being regularly re-assessed.

The aim of the ABCDE approach is to improve the clinical outlook of the unwell patient, with or without a definitive diagnosis.

The below guide is a general overview that can be used for any unwell patient in a simulation setting; it may seem intimidating at first but remember your patient is unlikely to need all of the investigations or interventions mentioned! More specific cases can be found in the emergency section of the site and are linked to throughout. This guide is written with final year medical students in mind– the assessments, investigations, and interventions included may generally be expected to be within the competencies of a junior doctor.

This guide has been created to assist students in preparing for emergency simulation sessions as part of their training, it is not intended to be relied upon for patient care.

Tips before you begin

  • Treat all problems as you find them
  • Re-assess regularly and after every intervention to see if your management is effective
  • Make use of the team around you to delegate tasks where appropriate – is another clinical member of staff available to help you?
  • All critically unwell patients should have continuous monitoring equipment attached for accurate observations and if necessary ECG readings – this will save you time! Communicate how often would you like these readings to be relayed to you
  • If you need senior input for your patient, call for help early using an appropriate SBARR handover structure (check out the guide here)
  • Review results (e.g. laboratory investigations) as they become available
  • Make use of medical school/hospital guidelines and algorithms in managing specific situations such as haematemesis
  • Any medications or fluids will need to be prescribed
  • Your assessment and management should be documented in the notes (however this should not delay initial clinical assessment and management)

Initial steps

You are likely to see this patient after a brief handover from another member of staff.


Introduce yourself to whoever has requested a review of the patient.



Perform a quick general inspection of the patient to get a sense of how unwell they are:

  • Check consciousness level using AVPU
  • How do they look? Are they pale?
  • How is their breathing?
  • Are there obvious signs of bleeding?
  • What is around the bedside? (look for IV lines, monitoring equipment etc).



  • Introduce yourself to the patient
  • Ask the patient how they are doing – in what way are they feeling unwell?
  • Are they in pain?



  • Make sure the patient notes, observation chart and prescription chart are on hand
  • Ask for another clinical member of staff to assist you if possible

If the patient is unconscious or unresponsive, start the basic life support (BLS) algorithm as per resuscitation guidelines.



Can the patient talk?


  • Airway is patent; move on to Breathing assessment



  • Look for signs of airway compromise (e.g. see-saw breathing, use of accessory muscles, diminished breath sounds, added sounds)
  • Is the patient cyanosed?
  • Open the mouth and inspect: is there anything obviously compromising the airway (e.g. secretions)?



Possible causes of airway compromise:

  • Inhaled foreign body (acute onset, may be unilateral, classically stridor)
  • Secretions, blood, vomit (often obvious, may have gurgling breath sounds)
  • Soft tissue swelling: anaphylaxis (rash, shock, angioedema); infection (e.g. quinsy)
  • Mass in the surrounding tissues (e.g. a tumour)
  • Laryngospasm
  • Depressed level of consciousness (e.g. opioid overdose, head injury)




In any case of airway obstruction, seek immediate expert help from an anaesthetist. You may need the crash team. In the meantime, you can perform some basic airway manoeuvres to help maintain the airway.


Maintain the airway whilst awaiting senior input

1. Perform head tilt, chin lift manoeuvre.

2. If noisy breathing persists try a jaw thrust.

3. If airway still appears compromised use an airway adjunct:

  • Insert an oropharyngeal airway (Guedel) only if unconscious (as otherwise may gag/aspirate)
  • Alternatively, use a nasopharyngeal airway (better tolerated if the patient is partially conscious)


Commence algorithm as per guidelines.

See anaphylaxis case

Re-assess after any intervention




Respiratory rate (12-20 breaths per minute)

  • Bradypnoea may be due to sedation, opioid toxicity, raised intracranial pressure (ICP), or exhaustion in airway obstruction (e.g. COPD)
    • n.b. respiratory acidosis
  • Tachypnoea may be due to airway obstruction, asthma, pneumonia, PE, pneumothorax, pulmonary oedema, heart failure, or anxiety
    • n.b. respiratory alkalosis


Oxygen saturation (88%-92% in COPD; 94%-98% otherwise)

  • Hypoxaemia may be seen in PE, aspiration, COPD, asthma, and pulmonary oedema



  • Check for central cyanosis: hypoxia can have CNS, respiratory, cardiac and haematological causes
  • Listen to the breath sounds- rattling suggests secretions
  • Expose chest



  • JVP (raised in eg acute severe asthma, heart failure, fluid overload)
  • Signs of respiratory distress (sweating, use of accessory muscles, abdominal breathing)
  • Deformity affecting breathing
  • Rhythm and depth of inspiration
    • Cheyne-Stokes respiration (cyclical apnoeas, then varying depth of inspiration/rate of breathing) may be due to stroke, raised ICP, pulmonary oedema, opioid toxicity, hyponatraemia, or carbon monoxide poisoning
    • Kussmaul’s respiration (deep, sighing) can be seen in metabolic acidosis (e.g. DKA)



  • Trachea – is there mediastinal shift due to (e.g. tension pneumothorax, fibrosis)?
  • Chest expansion – unequal (e.g. tension pneumothorax)



  • Hyper-resonance in pneumothorax, dullness in consolidation



  • Bronchial breathing  (e.g. pneumonia)
  • Reduced breath sounds with pneumothorax, pleural fluid, or consolidation
  • Unilateral crackles suggests consolidation
  • Bibasilar crackles may indicate pulmonary oedema or bronchitis




Take an ABG if indicated by any abnormal observations or examination findings.

See how to take an ABG and how to interpret results


Chest X-Ray

Order a portable chest X-ray if you suspect lung pathology.

See chest x-ray interpretation guide



Any patient who is short of breath should be sat up in the bed if possible to aid inspiration.



Give oxygen to all critically unwell patients: 15L via a non-rebreathe mask

In COPD, target saturations accordingly (88-92%). Consider using a Venturi mask: 24% (4L) or 28% (4L)

Consider non-invasive ventilation (NIV) in acute exacerbations of COPD after appropriate review

See oxygen prescribing guide (coming soon)


Acute severe asthma

Use guidelines to treat accordingly with nebulisers.

See acute management of asthma case


Acute exacerbation of COPD

Manage an acute exacerbation of COPD with oxygen, steroids, nebulisers (+/- antibiotics).

See acute exacerbation of COPD guide (coming soon)



Treat problems such as pneumonia, pneumothorax, PE as you identify them.

See other relevant cases: Pneumothorax, PE (coming soon)

Re-assess after any intervention




Temperature (36.0°c – 37.9°c)

  • Pyrexia most commonly suggests infection. Beware febrile neutropenia!
  • Septic patients may have high or low temperature
  • Consider warming (e.g. Bair Hugger™) in hypothermia – seek help

Heart rate (60-99 beats per minute)

  • Causes of tachycardia (HR>99) include hypovolaemia, arrhythmia, infection, hypoglycaemia, thyrotoxicosis, anxiety, pain, and iatrogenic causes (e.g. salbutamol).
  • Causes of bradycardia (HR<60) include acute coronary syndrome (ACS), ischaemic heart disease (IHD), electrolyte imbalance, and iatrogenic causes (e.g. beta-blockers).


Blood pressure

  • Target is patient’s normal BP or systolic >100mmHg
  • Check patient’s normal BP
  • Hypertension in women of childbearing age – consider pre-eclampsia
  • Hypertension may suggest fluid overload or endocrine abnormalities (e.g. Conn’s syndrome, Cushing’s syndrome)
  • Hypertensive emergency (systolic > 180 mmHg or diastolic > 100 mmHg): confusion, drowsiness, breathlessness, chest pain, visual disturbances (seek immediate senior help)
  • Causes of hypotension include hypovolaemia, sepsis, iatrogenic (e.g. opioids, antihypertensives, diuretics).


Extremes of heart rate or blood pressure with any worrying features such as shock, new heart failure, syncope or myocardial ischaemia suggest the patient may be peri-arrest. Seek immediate senior help and alert the crash team as appropriate.


Is the patient septic?

You have enough information to identify SIRS at this point. Perform the sepsis 6 immediately in suspected sepsis.

  1. Administer oxygen
  2. Take blood cultures
  3. Give IV antibiotics
  4. Give IV fluids
  5. Check serial lactates
  6. Measure urine output


Check peripheries: warm/cold/cyanosed

Measure central cap refill time: CRT>2 seconds may suggest shock or dehydration



  • JVP (if not already assessed): raised in fluid overload, sunken in dehydration



  • Central and peripheral pulse for rate, rhythm, volume, and quality
    • A bounding pulse suggests sepsis or fluid overload, a weak pulse suggests poor cardiac output
    • An irregular pulse may be due to atrial fibrillation (AF)
  • Check ankles/sacrum for oedema- is the patient in heart failure? Are they overloaded with fluid?



  • Does the patient have a new murmur suggestive of endocarditis?
  • Is there a pericardial rub or muffled heart sounds (pericarditis)?
  • A third heart sound may indicate heart failure



Fluid output

What is the patient’s fluid output?

  • Oligouria may suggest hypovolaemia, poor cardiac output, acute kidney injury (AKI) or dehydration. Suspect retention or obstruction if the patient is otherwise stable.
  • The output may be high in fluid overload.





Insert at least one wide-bore IV cannula (14G or 16G) and take bloods as below.

See cannulation guide


Bloods and blood cultures

Collect blood cultures and bloods as you cannulate. Request FBC, U&E, LFTs for all patients, and any other relevant bloods:

  • Sepsis: CRP, lactate, blood cultures
  • Haemorrhage or surgical emergency: Coagulation and cross-match
  • Acute coronary syndrome (ACS): Cardiac enzymes
  • Arrhythmia: Calcium, magnesium, phosphate, TFTs, coagulation
  • PE: D-dimer (depending on Well’s score)
  • Overdose: Toxicology screen
  • Electrolyte imbalance: Calcium, magnesium, phosphate
  • Ruptured ectopic: Coagulation, cross-match, ß-HCG levels
  • Anaphylaxis: Consider serial mast cell tryptase levels

See blood cultures guide 

See blood bottles guide



Record a 12-lead ECG if appropriate – if the patient has chest pain, arrhythmia, a murmur, or suspected electrolyte imbalance.

Consider continuous ECG monitoring.

See recording an ECG guide

See ECG interpretation guide


Bladder scan

Perform a bladder scan in suspected retention or obstruction.


Urine pregnancy test

Perform a urine pregnancy test in any fertile woman presenting with shock/abdominal pain/gynaecological symptoms.


Other cultures/swabs

Plan to collect and send any other appropriate cultures in suspected sepsis (e.g. sputum, urine, swabs from lines).


Fluid output/catheterisation

Commence fluid balance chart if not already in place.

Plan to catheterise if appropriate.

See catheterisation guide




Hypovolaemia: Fluid challenge

Hypovolaemic patients require fluid resuscitation:

  1. Lay patient supine and raise legs if appropriate
  2. Give 500ml bolus Hartmann’s solution/0.9% sodium chloride (warmed if available) over 15 mins
    • In heart failure: Give 250ml fluid as above; check the chest for crackles after each bolus as there is a risk of fluid overload and pulmonary oedema
  3. Repeat up to 4 times (2000ml/1000ml), monitoring response

Stop and seek help if the patient has a negative response (e.g. increased chest crackles).

Seek senior help if the patient isn’t responding adequately to repeated boluses.

See fluid prescribing guide for more details on resuscitation fluids.


Acute coronary syndrome (ACS)

In suspected ACS, manage with pain relief, nitrites, aspirin and oxygen as per guidelines. Seek senior input.

See ACS case (coming soon)



Perform sepsis 6 as per guidelines. Seek senior input.

See sepsis case (coming soon)



Restore intravascular volume with blood products and slow bleeding. Seek urgent senior input.

See post-operative bleed case (coming soon)

See upper GI bleed case


Fluid overload

Manage with diuretics. Seek senior input.

See fluid overload case (coming soon)


Atrial fibrillation (AF)

Manage AF with rate/rhythm control or cardioversion. Seek senior input.

See AF case (coming soon)

Re-assess after any intervention




  • Repeat AVPU
  • Assess pupils (size, symmetry, reaction to light)
    • Pinpoint pupils in opioid overdose
    • Dilated pupils may indicate TCA overdose or intracerebral pathology
  • Calculate Glasgow Coma Scale (GCS) if appropriate
  • Check drugs chart for opioids, sedatives, anxiolytics and antihypertensives

Causes of depressed consciousness

Acute deterioration in consciousness level may be due to a number of causes including:

  • Hypovolaemia
  • Hypoxia
  • Hypercapnia
  • Metabolic disturbance (hypoglycaemia)
  • Seizure
  • Raised intracranial pressure/other neurological insults
  • Drug overdose
  • Iatrogenic causes (e.g. administration of opiates for pain relief)


Alert a senior immediately if you have any concerns about the consciousness level of a patient. A GCS of 8 or below warrants urgent expert help from an anaesthetist. A crash team may be needed.

Re-assess and maintain the airway.


Blood glucose (4.0-11.0 mmols/L)

  • Measure capillary blood glucose to identify hypo/hyperglycaemia
  • Nb. A reliable arterial blood glucose may already be available as part of your ABG results


Is the patient diabetic?

  • Check for ketones if BM > 15mmols as patient may be in diabetic ketoacidosis (DKA)



Capillary blood glucose

Measure capillary blood glucose as above

See measuring blood glucose guide


Urine dip/ketostick

Check urine for ketones in suspected DKA

See urinalysis guide



Request a CT head in suspected intracranial pathology after discussion with senior.




Concerns about consciousness level always warrant senior input. Re-assess and maintain the airway.

Maintain the airway

Maintain the airway as above (Airway- Intervention) in any patient with depressed consciousness.


Opioid toxicity

In opioid overdose, use Naloxone as per local policy. Seek senior advice.

See opioid toxicity case (coming soon)



In hypoglycaemia, administer glucose as per guidelines. Seek senior advice.

See hypoglycaemia case (coming soon)


Diabetic ketoacidosis (DKA)

In DKA, manage with fluids and insulin according to local guidelines. Seek senior advice.

See DKA case (coming soon)

Re-assess after any intervention


It may be necessary to fully expose the patient for a full assessment.

Remember to prioritise patient dignity and conservation of body heat.



  • Ask again: Is the patient in any pain? This can help to guide your assessment.


  • Check skin for rashes (adverse drug reaction, meningococcal sepsis), other signs of infection, and bruising (coagulation disorders)
  • Calves: are they red, tender or swollen (DVT)?
  • Lines in: Are there any signs of phlebitis or infection? Replace and remove any concerning lines- consider line tip culture
  • Catheter output: Is there pus or blood suggestive of infection or injury?
  • Surgical wounds: Are there signs of bleeding or infection?
    • There could be concealed internal bleeding into (e.g. peritoneum, pelvis or thoracic cavity)
  • Drains: What is the output? Worrying signs include pus, blood, or high/low output


If you identify bleeding:

In any bleeding, estimate the total blood loss and the rate of blood loss. Is the patient in shock?

In cases of severe haemorrhage or shock, seek immediate expert help. Be aware of the major haemorrhage protocol in your local hospital.



Other cultures/swabs

Take and send swabs or samples of any potential infection source- don’t forget line tip cultures if appropriate!





Seek advice from the surgical registrar in any post-operative bleeding.

Severe bleeding should be managed as an emergency.

Manage a post-operative bleed with blood products as appropriate.

See post-operative bleed case (coming soon)

See upper GI bleed case

See blood transfusion guide



Screen any patient with suspected infection for sepsis. Manage sepsis as per guidelines using the sepsis 6.

Consult local guidelines and/or microbiology advice to guide appropriate antibiotic treatment of infection.

See sepsis case (coming soon)


Deep vein thrombosis (DVT)

In suspected DVT, calculate a Well’s score and manage appropriately. Seek senior advice.

See DVT case (coming soon)

Re-assess after any intervention

Re-assessment and seeking help

  • Re-assess the patient in the same systematic manner as above. Your aim is to improve the clinical outlook of the patient.
  • React to any changes and evaluate the effectiveness of your interventions.
  • Deterioration should be recognized quickly and acted upon immediately.
  • Seek help if the patient shows no signs of improvement or if you have any concerns.


Who can help?

  • You should have another member of the clinical team aiding you in your ABCDE assessment, such as the patient’s nurse, who can perform observations, take samples to the lab, catheterise if appropriate etc.
  • You may need further help or advice from a senior staff member. Do not delay seeking help if you have concerns about your patient. 
  • Use an effective SBARR handover for best practice. See SBAR handover guide.

Who to contact:

In any critical situation: Critical care team/anaesthetist on call/crash team as appropriate


  • Always contact the anaesthetist on call in anyone with airway concerns



  • Medical registrar on call
  • Critical care team to assess for NIV/invasive ventilation



  • Medical registrar on call and others as advised
  • Sepsis: Medical registrar on call and microbiologist on call
  • ACS/arrhythmia: Medical registrar on call, then cardiologist on call if advised
  • Poor urine output: Medical registrar on call, then renal team if advised
  • Haemorrhage: Surgical registrar on call, haematology, transfusion lab
  • Ruptured ectopic: Gynaecological registrar on call
  • Upper/lower GI bleed: Gastroenterologist/endoscopist on call
  • Patients who have had recent surgery: As above plus surgical registrar on call



  • Anaesthetist on call if airway is threatened 
  • Medical registrar on call
  • DKA: Medical registrar on call, then endocrinologist on call if advised



  • DVT: Medical registrar on call
  • Concerning rash: Medical registrar on call. Dermatologist on call, microbiologist on call if advised

Next steps

Well done! You’ve stabilised the patient and they’re doing much better. Just a few more things to do…

Take a history

Take a more detailed history of what has happened and how the patient has been. Involve staff or family members as appropriate.
Check out our history taking guides here


Review the patient’s notes, observations, fluid charts, and any investigation findings. Double check the medications you have just prescribed, and any routine medications the patient is taking.


Document your ABCDE assessment clearly, including examination, observations, investigations, interventions, and patient response/changing condition. Write down any pertinent details from your history-taking.

See documentation guide



If a senior doctor hasn’t already been involved, it is important to contact them and make them aware of the unwell patient. As a junior doctor, it would be appropriate to give an SBARR handover outlining your assessment and actions, and to discuss the following:

  • Are any further assessments or interventions required?
  • Does the patient need a referral to HDU/ICU?
  • Should they be referred for a review by a speciality doctor?
  • Should any changes be implemented to the management of any underlying conditions?


The next team of doctors on shift should be made aware of any patient in their department who has become acutely unwell.