Why this matters: Shock is a time-critical failure of circulation in which tissues do not receive or use enough oxygen. It may begin with normal blood pressure and subtle behaviour change, then progress to organ failure and cardiac arrest. EMTs must recognise compensated shock, identify the likely mechanism, start safe supportive care and communicate deterioration before hypotension appears.
Scope and safety: These are educational notes for emergency-medicine students. Use the Uganda Clinical Guidelines, local ambulance protocols and senior medical direction. Shock requires urgent transfer to a facility able to provide IV/IO access, blood, surgery, vasoactive support and critical care. Never delay ABCDE, haemorrhage control, oxygenation or emergency referral while completing a checklist.
Learning outcomes
- Define shock and explain how oxygen delivery, perfusion and cellular metabolism fail.
- Classify hypovolaemic, distributive, cardiogenic and obstructive shock and recognise mixed forms.
- Identify compensated, progressive and irreversible/decompensated stages.
- Perform initial contact, primary survey, focused history and repeated perfusion assessment.
- Interpret vital signs, urine output, lactate, ECG, ultrasound and other investigations in context.
- Describe first aid, pre-hospital, hospital and nursing priorities without treating blood pressure in isolation.
1. Definition and the oxygen-delivery problem
Shock is a life-threatening state of inadequate tissue perfusion and oxygen utilisation. Oxygen delivery (DO2) depends mainly on cardiac output and arterial oxygen content. Cardiac output depends on heart rate and stroke volume; stroke volume is influenced by preload, contractility and afterload. A patient can be in shock with a normal BP when vasoconstriction temporarily maintains pressure, or with a normal SpO2 when circulation cannot deliver oxygen to cells.
“FLOW”: Fill the tank (preload/volume); Let the pump work (heart/contractility); Open the pipes (vascular tone/obstruction); Watch the tissues (mental state, skin, urine, lactate and capillary refill).
2. Classification of shock
| Type | Core mechanism | Common causes | Typical bedside pattern |
|---|---|---|---|
| Hypovolaemic | Too little circulating volume → reduced venous return, preload and stroke volume. | External/internal bleeding, vomiting/diarrhoea, dehydration, burns, third spacing. | Cool clammy skin, tachycardia, narrow pulse pressure, low JVP, thirst, oliguria. |
| Distributive | Vasodilation and maldistribution; relative hypovolaemia, capillary leak or loss of sympathetic tone. | Sepsis, anaphylaxis, neurogenic shock, toxins and adrenal crisis. | Warm flushed skin early in sepsis, bounding pulse or low SVR; later cool mottled shock. |
| Cardiogenic | Primary pump failure → low cardiac output despite adequate volume. | MI/ACS, severe arrhythmia, myocarditis, cardiomyopathy, valve failure. | Chest pain, pulmonary oedema, raised JVP, cool skin, dysrhythmia, low urine. |
| Obstructive | Mechanical block to filling, ejection or pulmonary blood flow. | Tension pneumothorax, cardiac tamponade, massive PE, severe dynamic hyperinflation. | Sudden collapse, PEA, distended neck veins, unequal breath sounds or muffled heart sounds. |
| Mixed | More than one mechanism at once. | Trauma with bleeding and tension pneumothorax; septic cardiomyopathy; burns with infection. | Features overlap; response to one treatment is incomplete. |
3. The stages of shock
| Stage | Physiology | Signs | EMT implication |
|---|---|---|---|
| Compensated/early | Sympathetic activation maintains BP by tachycardia and vasoconstriction. | Anxiety, thirst, cool skin, delayed capillary refill, tachycardia, rising RR, normal BP. | Do not reassure; find and treat the cause before decompensation. |
| Progressive/decompensated | Compensation fails; hypotension and cellular anaerobic metabolism develop. | Confusion, weak pulse, hypotension, oliguria, pallor/mottling, rising lactate and acidosis. | Resuscitate, expedite transport, establish access and call critical-care/surgical help. |
| Irreversible/refractory | Prolonged hypoperfusion causes mitochondrial, renal, hepatic, cardiac and coagulation failure. | Coma, anuria, severe acidosis, refractory hypotension, dysrhythmia and arrest. | Advanced resuscitation, source control and critical care; prognosis is poor if treatment is delayed. |
4. Initial contact and scene approach
- Scene safety/PPE: identify traffic, violence, fire, chemicals, infection, electrical risk and ongoing bleeding.
- Mechanism and first impression: trauma, delivery, infection, bite/sting, chest pain, diarrhoea, poisoning or sudden collapse.
- Call for help early: request ALS, blood, surgical/obstetric team, security or evacuation according to the setting.
- Do not make the patient walk: keep them warm, flat when tolerated and in a position that supports breathing; avoid sudden standing.
- Use a team leader: allocate airway, circulation, monitoring, access, documentation and transport roles.
5. Primary assessment: ABCDE
| Step | Assessment | Immediate action in shock |
|---|---|---|
| A — Airway | Speech, obstruction, blood/vomit, swelling, facial trauma and airway protection. | Position, suction, airway adjunct, oxygen/ventilation and early advanced-airway help. |
| B — Breathing | RR, work, chest rise, breath sounds, SpO2, ETCO2, cyanosis and pneumothorax signs. | Oxygenate/ventilate; treat tension pneumothorax, bronchospasm or pulmonary oedema as indicated. |
| C — Circulation | Pulse rate/rhythm/quality, BP, capillary refill, skin, JVP, bleeding, ECG and temperature. | Control haemorrhage, IV/IO access, cautious fluids/blood, ECG and urgent cause-specific treatment. |
| D — Disability | AVPU/GCS, pupils, glucose, seizures, pain and mental-state change. | Correct glucose, protect airway, treat seizures and prevent secondary brain injury. |
| E — Exposure | Full skin/trauma/infection examination, abdomen, back, pregnancy, burns and environment. | Find hidden bleeding/rash/source; prevent hypothermia and preserve dignity. |
ABCDE principle: Assess and treat the immediate life threat before moving on, then repeat the assessment after every intervention. This approach is recommended for deteriorating or critically ill patients.
6. Perfusion assessment beyond blood pressure
- Mental state: anxiety, restlessness, confusion, drowsiness or coma may reflect cerebral hypoperfusion.
- Skin: colour, temperature, moisture, mottling, cyanosis and peripheral perfusion.
- Capillary refill: interpret with temperature, age and vasoconstrictors; trend it rather than using it alone.
- Pulse: rate, rhythm, central/peripheral strength and radio-femoral delay.
- Urine: oliguria or anuria suggests reduced renal perfusion, but obstruction and renal disease can mimic it.
- Respiratory pattern: tachypnoea or deep breathing may signal compensation for lactic/metabolic acidosis.
- Blood pressure: hypotension is late in some patients; compare with baseline and pulse pressure.
7. Focused history: SAMPLE + shock clues
| Question | What it reveals |
|---|---|
| What happened and when? | Bleeding, sepsis, allergy, trauma, toxin, chest pain or sudden obstruction. |
| Fluid/bleeding loss? | Vomiting, diarrhoea, urine, burns, childbirth, melena, haematemesis, vaginal bleeding or hidden trauma. |
| Heart/lung history? | MI, heart failure, arrhythmia, COPD/asthma, pulmonary hypertension or previous PE. |
| Medicines/substances? | Anticoagulants, antihypertensives, diuretics, insulin, steroids, beta-blockers, toxins or recreational drugs. |
| Allergy/pregnancy? | Anaphylaxis and obstetric causes require different immediate pathways. |
| Previous baseline? | Normal BP, mental state, renal function, mobility and urine output improve interpretation. |
8. Bedside and hospital investigations
| Investigation | What it helps answer | Important limitations |
|---|---|---|
| Glucose | Hypoglycaemia/hyperglycaemia causing or worsening altered state and shock. | Point-of-care errors occur with poor perfusion; confirm unexpected values. |
| ECG/monitor | MI, dysrhythmia, hyperkalaemia, right-heart strain or electrical cause. | A normal initial ECG does not exclude evolving MI/PE. |
| ABG/VBG + lactate | Acidosis, oxygenation, ventilation, lactate and response to resuscitation. | Lactate is a perfusion marker, not a diagnosis; interpret trend and causes. |
| Full blood count/group-crossmatch | Anaemia, infection, platelets and blood-product preparation. | Early haemorrhage may have a normal haemoglobin. |
| Electrolytes/renal/liver tests | AKI, potassium/sodium disturbance, toxin/metabolic disease. | Laboratory delay should not postpone life-saving treatment. |
| Coagulation/fibrinogen | Anticoagulation, DIC, trauma coagulopathy and bleeding planning. | Values can change rapidly during massive haemorrhage. |
| Bedside ultrasound | Cardiac contractility, pericardial fluid, lung sliding, IVC/volume clues, free fluid. | Operator-dependent; a negative scan does not exclude all pathology. |
| Imaging | Source of bleeding, PE, pneumothorax, infection or trauma. | Unstable patients need stabilisation and appropriate bedside alternatives. |
9. Recognising shock patterns
| Feature | Hypovolaemic | Cardiogenic | Distributive | Obstructive |
|---|---|---|---|---|
| Skin | Cool, pale, clammy | Cool, clammy, cyanotic | Warm/flushed early; cool late | Cool, clammy; cyanosis possible |
| JVP | Low/flat | Raised | Low/normal early | Raised in tamponade/PE/tension pneumothorax |
| Lungs | Usually clear unless aspiration | Crackles/pulmonary oedema | Variable; ARDS/sepsis possible | Absent one side or clear with tamponade/PE |
| Pulse | Fast, weak, narrow pulse pressure | Fast/irregular, weak | Bounding early or weak late | Fast, weak; PEA possible |
| Fluid response | Often improves if volume replaced and bleeding controlled | May worsen pulmonary oedema | Partial/temporary; vasodilation and leak persist | Minimal until obstruction relieved |
10. Shock severity and reassessment
Do not wait for one threshold. Record trends in RR, pulse, BP, mental state, SpO2/oxygen requirement, capillary refill, temperature, urine output, lactate, ECG and treatment response. A patient with persistent tachycardia, worsening confusion, decreasing urine and rising lactate is deteriorating even if systolic BP remains above a textbook cut-off.
Shock index: Heart rate divided by systolic BP can help flag occult shock when interpreted with age, pregnancy, beta-blocker use, fever and baseline physiology. It is a screening aid, not a diagnosis or replacement for clinical judgement.
11. Differential diagnoses that mimic shock
- Vasovagal syncope with rapid recovery when supine.
- Severe hypoglycaemia, seizure/post-ictal state or stroke.
- Sepsis without hypotension, adrenal crisis, thyroid storm or severe hypothermia.
- Medication effects: beta-blockers, calcium-channel blockers, opioids, sedatives, antihypertensives.
- Massive PE, tension pneumothorax, tamponade and dynamic hyperinflation.
- Psychological distress or panic—diagnosed only after medical threats are assessed.
12. Immediate first aid and pre-hospital priorities
- Call emergency help and keep the patient supine/positioned safely; prevent standing or walking.
- Open and maintain the airway; suction and use basic adjuncts when indicated.
- Give oxygen for hypoxaemia/respiratory distress and assist ventilation if breathing is inadequate.
- Control external bleeding with direct pressure, wound packing/tourniquet when trained, and pelvic/limb stabilisation where indicated.
- Keep the patient warm with blankets, remove wet clothing and avoid overheating during fever/hyperthermia.
- Do not give oral food, drink or medicine to a shocked, vomiting, confused or potentially surgical patient.
- Perform glucose, vital signs, ECG/monitoring and repeated perfusion checks; record times and trends.
- Expedite transport to the right facility and give a structured pre-alert with suspected mechanism and interventions.
13. Nursing priorities during assessment
- Apply continuous monitoring appropriate to severity; repeat ABCDE after every intervention.
- Establish and secure IV/IO access; collect blood samples without delaying resuscitation.
- Maintain accurate fluid balance, urine output and drain/bleeding measurements.
- Administer prescribed oxygen, fluids, blood, antibiotics, adrenaline/vasopressors and analgesia safely; check response and adverse effects.
- Prevent hypothermia, pressure injuries, aspiration, infection and medication errors.
- Provide calm explanations, preserve dignity, involve family appropriately and document consent/capacity.
- Escalate worsening vitals, mental state, perfusion, urine or lactate immediately—not at the next routine round.
14. Hospital diagnostic workflow
- Resuscitation bay: ABCDE, monitoring, oxygen/ventilation, access, blood sampling and team leader.
- Identify mechanism: bleeding/volume loss, pump failure, vasodilation, obstruction or mixed cause.
- Bedside tests: glucose, lactate/ABG, ECG, ultrasound and temperature.
- Targeted imaging: trauma, chest, abdomen, pelvis, PE, infection or cardiac pathology based on stability.
- Source control: surgery, endoscopy, drainage, catheterisation, reperfusion, antibiotics or antidote pathway.
- Disposition: theatre, ICU, high-dependency, blood bank, obstetric/paediatric/medical specialist team.
15. Prevention and early recognition
- Use early-warning charts and respond to abnormal trends.
- Prevent dehydration and recognise high-output vomiting, diarrhoea, burns, drains and poor intake.
- Screen for sepsis, anaphylaxis, bleeding risk, medication toxicity and falls/trauma.
- Review medicines that increase hypotension, bleeding or renal injury during acute illness.
- Educate patients and families to seek help for faintness, confusion, cold/clammy skin, severe breathlessness, low urine or worsening pain.
16. Clinical scenarios
Scenario 1 — Compensated haemorrhage: A road-crash patient is anxious, pale, tachycardic and thirsty but has a normal BP. Search for hidden bleeding, expose fully, control haemorrhage, keep warm, obtain access and pre-alert trauma surgery. Normal BP does not exclude shock.
Scenario 2 — Cardiogenic shock: An older adult with chest pain is clammy, hypotensive, dyspnoeic and has crackles/raised JVP. Treat as pump failure: oxygenation/ventilation, ECG, cautious fluids, urgent reperfusion/cardiology and avoid reflexive large-volume boluses.
Scenario 3 — Obstructive shock: A ventilated trauma patient suddenly becomes hypotensive with unilateral absent breath sounds and high airway pressure. Suspect tension pneumothorax; ventilate, call for immediate decompression by a trained provider and continue reassessment.
Scenario 4 — Distributive shock: A febrile patient is confused, warm, tachypnoeic and hypotensive with rising lactate. Suspect sepsis; obtain cultures where this does not delay treatment, start the sepsis pathway, give appropriate crystalloid with reassessment and escalate to vasoactive support if needed.
Scenario 5 — Anaphylaxis: Minutes after an injection, a patient develops wheeze, urticaria, dizziness and weak pulse. Give IM adrenaline promptly according to protocol, oxygenate, position safely, establish access/fluids and transfer for observation.
17. Shock handover checklist
- Time of onset, suspected mechanism, events, comorbidities, medicines and allergies.
- ABCDE findings and trends: HR/rhythm, BP/MAP, RR, SpO2/oxygen, GCS/glucose, temperature, capillary refill and urine.
- Bleeding/volume losses, examination findings, ECG/ABG/lactate/ultrasound and imaging.
- Interventions with exact time: haemorrhage control, oxygen/airway, IV/IO, fluids/blood, medicines and response.
- Concern, destination, specialist contacted, outstanding tests and next reassessment.
18. Revision questions
- Define shock in terms of tissue perfusion and oxygen delivery.
- Compare hypovolaemic, distributive, cardiogenic and obstructive shock.
- Why can a patient be in compensated shock with normal BP?
- List six signs of poor perfusion beyond hypotension.
- What is the purpose of ABCDE in shock?
- Which investigations help identify pump failure, bleeding, acidosis and obstruction?
- Why may a haemoglobin result be normal early in acute bleeding?
- What findings make large-volume fluid risky?
- What information belongs in a shock pre-alert?
- How can early recognition prevent irreversible shock?
19. Key take-home points
- Shock is inadequate tissue perfusion, not simply a low BP reading.
- Classify the mechanism while resuscitating: low volume, vasodilation, pump failure, obstruction or mixed.
- Use ABCDE, mental state, skin, urine, lactate, ECG and trends to diagnose severity.
- Control bleeding, support oxygenation, avoid harmful delays and transfer to definitive care.
- Repeated reassessment and a precise handover are essential to prevent progression to organ failure.
Selected authoritative resources
- Resuscitation Council UK ABCDE approach.
- WHO Emergency Care Toolkit.
- Surviving Sepsis Campaign adult guidelines.
- MSD Manual: shock classification and physiology.
For EMT practice: A patient who looks “almost okay” may be compensating. Trust trends, repeat ABCDE, search for the mechanism and act before blood pressure collapses.