Understanding Shock: A Systematic Approach

(warning: this article contains graphic images)

In emergency medicine, few words carry as much weight as "shock." While bystanders might use this term to describe emotional distress, medical shock represents a critical failure of the body's circulatory system to deliver adequate oxygen and nutrients to tissues.

Picture your body as a bustling city, with billions of cells all needing constant deliveries of oxygen and nutrients to function properly. When someone is in shock, it's like this city's delivery system has broken down – either there aren't enough delivery trucks (catastrophic blood loss), the distribution centres aren't working properly (heart failure), the roads are blocked (something is obstructing normal blood flow), or there is chaos in the supply chain (a problem distributing blood throughout the body).

 

Classifications of Shock

Modern emergency medicine recognises 4 categories of shock, each with its own characteristics and treatment priorities:

1. Hypovolaemic Shock

This most common form of shock occurs when there isn't enough blood volume circulating in the body. Key causes include:

  • Blood Loss (Haemorrhage): Whether visible or hidden, blood loss exceeding 20% of volume triggers the body's compensation mechanisms. Internal bleeding in the chest, abdomen, or thigh bones can be particularly challenging as significant volume can be lost before external signs appear.
  • Severe Burns: Beyond skin damage, burns trigger massive fluid shifts in the body. Proper fluid replacement is critical within the first 24 hours.
  • Severe Dehydration: Significant fluid losses from vomiting, diarrhoea, or excessive sweating can rapidly deplete intravascular volume. Children are particularly vulnerable due to their higher fluid turnover.
  • Environmental Exposure: Especially in hot environments, excessive fluid loss through sweating can lead to both volume depletion and electrolyte imbalances.

2. Cardiogenic Shock

When the heart fails as an effective pump, the whole body suffers. Common causes include:

  • Heart Attacks: Myocardial injury reducing contractility, often complicated by arrhythmias and mechanical complications.
  • Severe Dysrhythmias: Both brady- and tachyarrhythmias can critically reduce cardiac output. The threshold for intervention is lower in shocked patients.
  • Advanced Heart Failure: When the heart becomes very weak, it struggles to pump blood forward to the body (causing poor circulation) and also can't pump blood back from the lungs efficiently (causing fluid build up). This makes fluid management challenging - patients may be fluid overloaded in their lungs but still need fluids for their circulation.
  • Valvular Heart Disease: Acute valve dysfunction can precipitate rapid decompensation, particularly in aortic and mitral pathologies.
  • Cardiomyopathies: Various forms affect different aspects of cardiac function, requiring tailored management approaches.

3. Obstructive Shock

Sometimes the problem isn't the pump or the fluid, but something blocking normal blood flow:

  • Tension Pneumothorax: Air trapped in the chest cavity compresses the heart and major blood vessels. Requires immediate decompression in the shocked patient.
  • Cardiac Tamponade: As little as 150-200ml of pericardial fluid can critically impair cardiac filling.
  • Pulmonary Embolism: Can range from subtle to massive, with shock developing from right heart failure and hypoxemia.
  • Severe Bronchospasm: Creates a backup of pressure that affects heart function, potentially leading to cardiovascular collapse.

4. Distributive Shock

This type involves problems with how blood is distributed throughout the body:

  • Septic Shock: A severe infection causing widespread inflammation and vessel dilation. Early recognition and treatment bundle completion within one hour improves outcomes.
  • Anaphylactic Shock: Life-threatening allergic reactions affecting multiple body systems. Immediate adrenaline is crucial.
  • Neurogenic Shock: Usually from spinal cord injuries disrupting normal blood vessel control, and requires careful blood pressure management.
  • Endocrine Shock: Conditions like adrenal crisis require both hormone replacement and careful fluid management.

 

Clinical Assessment of Shock

Step 1. First Impression (The 15-Second Check)

 Look for these key signs when you first see your patient:

  • General appearance: Alert? Confused? Lethargic?
  • Breathing effort: Easy? Working hard? Using extra muscles?
  • Skin colour: Pale? Mottled? Blue?
  • Position: Comfortable? Distressed? Unable to lie flat?

Step 2. Vital Signs (The Hard Data)

Breathing

  • Rate should be 12-20 per minute in adults
  • Watch for:
    • Fast breathing (>20) suggests early shock
    • Very fast (>30) or slow/shallow (<10) indicates severe shock
    • Use of neck/chest muscles means working too hard
    • Listen for crackles (fluid in lungs) or wheezing (allergic reaction)

Heart Rate

The normal adult heart rate is 60-100 beats per minute. 

  • In early shock: The heart typically speeds up to over 100 beats per minute as the body tries to compensate for poor circulation
  • During severe shock: Can range from very fast (>120) to dangerously slow, especially if the heart is affected

Remember, while a fast heart rate is common in shock, some types of shock (like those caused by certain heart problems or spinal injuries) might show a normal or slow heart rate.

Circulation

Normal adult blood pressure is 120/80 mmHg (systolic/diastolic). Concerning signs of shock, include:

  • Systolic < 90 mmHg (e.g., 85/60)
  • A drop > 40 mmHg from patient's normal (e.g., from 150/90 to 110/70)
  • MAP < 65 mmHg (MAP = [systolic + 2×diastolic] ÷ 3)
  • Capillary refill >2 seconds suggests poor circulation

Remember: Blood pressure can stay normal until late in shock, so don't rely on this alone.

Skin Signs

Normal skin is warm to touch, even coloured, and mostly dry unless the patient was sweating or in water prior to the incident. Skin signs in shock, include:

  • Temperature:
    • In most shock: cool skin, especially hands/feet
    • In septic shock: warm skin early, becomes cool later
    • Check warmth up arms/legs (temperature gradient)
  • Colour:
    • Pale: poor circulation
    • Mottled: patchy purple/white pattern (very concerning)
    • Blue: severely reduced oxygen (critical sign)
  • Moisture:
    • In shock: clammy/sweaty
    • Check palms, forehead, chest
Remember: Assess skin across multiple body areas, not just one spot. Changes in skin signs often appear before vital signs worsen.

 

Brain Function

  • Level of Consciousness (AVPU):
    • Alert: Fully awake, oriented, responds normally
    • Voice: Only responds when you talk to them
    • Pain: Only responds to physical stimulus
    • Unresponsive: No response to voice or pain
  • Early Warning Signs:
    • Anxiety or restlessness - unexplained worry
    • Confusion - unsure of time/place, poor concentration
    • Irritability - can't get comfortable
  • Worsening Signs:
    • Drowsiness - spontaneously falling asleep, hard to wake up
    • Combative Behaviour - fighting against help
    • Severe deterioration - unable to protect airway, no response to voice/pain, seizures, or abnormal posturing

    Remember: Early brain function changes can signal shock, so compare to patient's normal state, consider rapid changes most concerning, account for substances that affect mental status, and always check blood sugar since hypoglycaemia can look similar.

    Step 3. Additional Checks

    • Urine Output
      • Normal = 0.5-1.0 mL/kg/hour
      • Less than this needs urgent attention
    • Blood Sugar
      • Normal range = 4-8 mmol/L (72-144mg/dL)
      • Test if patient shows any mental status changes
      • Low blood sugar can mimic shock symptoms
      • High blood sugar may indicate stress response
      • Diabetic patients need more frequent checks
    • Core Temperature
      • Normal body temperature = 36.5-37.5°C (97.7-99.5°F)
      • High: >38.5°C (101.3°F) = possible infection/sepsis
      • Low: <35°C (95°F) = hypothermia risk

    Step 4. Special Patient Groups

    Children

    • Poor feeding/weak cry, decreased wet nappies, sunken fontanelle, no tears, decreased activity
    • Can look stronger for longer, then suddenly crash. 
    • Parent concern crucial - they know normal behaviour
    • Vital signs like blood pressure can vary by age but heart rate is the most reliable for identifying shock 
    • Capillary refill check on sternum/forehead is also more reliable than BP (<2 seconds)

    Elderly

    • Elderly bodies don't adapt to shock as well as younger bodies:

      • Their heart rate doesn't increase as much when stressed,

      • They can't control their temperature effectively,

      • Their blood vessels are less flexible,

      • They don't feel thirsty even when they need fluids.

    • Some Medications can impact vital signs, including: Beta blockers (heart rate), ACE inhibitors (BP), diuretics (fluid), blood thinners (bleeding)
    • Decline happens faster 
    • Always check presentations against their normal values

    Pregnant Woman

    • Normal values differ in pregnant women:
      • Their heart rate and blood volume is increased
      • Lower Blood Pressure
      • Faster Breathing
    • Always lay them on their left side to prevent IVC compression
    • Two-patient assessment:
      • Mother: vital signs, pre-eclampsia, diabetes
      • Baby: heart rate, movement, contractions
    • Red flags: decreased foetal movement, bleeding, abdominal pain, headache with visual changes, swelling

    Modern Management Principles

    Modern shock management and prehospital treatment emphasises a systematic approach with continuous reassessment:

    • Initial Actions
      • Assess scene safety immediately to protect yourself and your patient
      • Placing shock patients in a supine position is generally recommended, as it may improve venous return,  however in certain situations (e.g., conscious patients with difficulty breathing), slightly elevating the head may be more appropriate.
      • While airway management is crucial, modern trauma management prioritizes circulation over airway (CAB approach)

    Remember, your specific response may vary depending on the exact nature of the emergency and situational nuances.

    • Cause-Specific Interventions
      • Haemorrhage control is first priority when patient has suffered a trauma that has resulted in uncontrolled bleeding
      • Early adrenaline administration is recommended for anaphylaxis
      • Tension pneumothorax requires immediate decompression in the shocked patient
    • Fluid Resuscitation
      • Modern approaches are more nuanced and individualised:
        • Non-traumatic shock may receive balanced crystalloid boluses with frequent reassessment
        • Traumatic shock management follows damage control resuscitation principles and ideally blood products
        • Physiological endpoints are preferred over fixed volume targets
        • Regular assessment of fluid responsiveness guides ongoing therapy
    • Monitoring and Reassessment
      • Vital signs should be tracked with clear documentation of trends
      • Response to interventions must be regularly evaluated
      • Early warning scores can help identify deterioration
      • Documentation should be thorough and contemporaneous

    TacMed Gear for the Recognition and Prehospital Treatment of Shock

     

    Understanding shock is crucial for all healthcare providers, and the key to successful management lies in early recognition, swift action, and an individualised approach to treatment. Remember that shock is a dynamic process where time is critical - the sooner you recognize and treat it, the better the outcome for your patient.

    Stay Safe,

    Team TacMed.

     

     

     

    References:

    Back to TacMed Learning Centre