Module 1 | Lesson 3

Sickle Cell Triggers

From Biology to Clinical Practice

Understanding why crises happen and how professionals can reduce risk

Welcome to Lesson 1 of Module 1

Estimated time: 25-30 minutes
Main activity: Watch the video then complete the reflection activity and knowledge quiz

What You Will Learn In This Lesson

Pain crises rarely occur without reason. Many are associated with physiological and environmental factors that increase the likelihood of red blood cells sickling.

Watch the Video

Watch the video exploring common triggers. Understanding these triggers helps professionals recognise risk and support people without oversimplification.

Learning Outcomes

By the end of this lesson, you will be able to:

  • Explain how common triggers contribute to red blood cell sickling.
  • Recognise situations that increase the risk of vaso-occlusive crises.
  • Appreciate why triggers differ between individuals.
  • Use trigger awareness to support prevention rather than assign blame.
  • Apply trigger knowledge during assessment and patient education.

Reflection Question

Before starting the lesson, consider:

hen someone presents in severe pain, how often do you think about what may have triggered the crisis?

Play

Some of the slides are text heavy by design. Feel free to pause the video to allow for your own reading speed.

Mechanism: Dehydration makes the blood more concentrated and can increase blood viscosity, creating conditions that promote sickling and vaso-occlusion.
Clinical signs: Look for reduced fluid intake, increased fluid loss, dry mouth, dark urine or reduced urine output.
Assessment questions: Ask about recent fluid intake and any vomiting, diarrhoea, fever, fasting, exercise or heat exposure.
Preventative advice: Encourage regular hydration, with additional attention to fluid intake during illness, hot weather and physical activity.

Mechanism: Cold can cause vasoconstriction and reduce blood flow, while heat can increase fluid loss and dehydration. Both may increase the risk of a crisis.
Clinical signs: Consider whether symptoms followed exposure to extreme temperatures or sudden changes between hot and cold environments.
Assessment questions: Ask about recent weather exposure, changes in temperature, physical activity and whether the person was able to stay warm or adequately hydrated.
Preventative advice: Encourage appropriate clothing, good hydration and planning ahead for extreme weather, travel and outdoor activities.

Mechanism: Infection increases inflammation, metabolic demand and oxygen requirements. Fever, fluid loss and reduced intake can further create conditions that favour sickling.
Clinical signs: Look for fever, respiratory symptoms, unusual fatigue or other signs of infection, alongside any new or worsening sickle cell symptoms.
Assessment questions: Ask about fever, recent illness, respiratory or urinary symptoms, fluid intake and contact with people who have been unwell.
Preventative advice: Encourage recommended vaccinations and prompt assessment of suspected infection. Fever and respiratory symptoms in someone with sickle cell disease require appropriate clinical attention.

Mechanism: Prolonged fatigue and inadequate rest can place additional physiological stress on the body. Fatigue may also occur alongside other triggers such as illness, dehydration or overexertion.
Clinical signs: Look for unusual or persistent tiredness, reduced energy, poor sleep or difficulty managing usual daily activities.
Assessment questions: Ask about recent sleep, changes in energy levels, increased physical demands and whether the fatigue is new or significantly worse than usual.
Preventative advice: Encourage adequate rest, pacing and attention to sleep. New, severe or persistent fatigue should be assessed rather than automatically attributed to sickle cell disease.

Mechanism: Strenuous activity increases oxygen demand and may contribute to dehydration and fatigue, particularly when combined with heat or inadequate rest.
Clinical signs: Consider whether symptoms developed during or following prolonged or unusually intense physical activity.
Assessment questions: Ask about recent activity levels, duration and intensity of exercise, hydration, rest and environmental conditions.
Preventative advice: Encourage appropriate, individualised physical activity with adequate hydration, pacing and rest. Exercise should not be discouraged unnecessarily.

Mechanism: When oxygen levels fall, haemoglobin S is more likely to polymerise, causing red blood cells to become rigid and sickle.
Clinical signs: Look for breathlessness, chest pain, reduced oxygen saturation or increased work of breathing.
Assessment questions: Ask about respiratory symptoms, existing lung conditions, recent surgery or anaesthesia, and recent high-altitude travel.
Preventative advice: Support good management of respiratory conditions and prompt assessment of breathing difficulties. Consider individual risks before high-altitude travel or procedures.

Mechanism: Physical and emotional stress can increase physiological demands and may contribute to a crisis alongside factors such as fatigue, poor sleep or illness.
Clinical signs: Consider exhaustion, disrupted sleep, recent surgery, significant life events or pressures affecting the person’s ability to manage their health.
Assessment questions: Ask sensitively about sleep, physical demands, recent procedures and current emotional or social pressures.
Preventative advice: Encourage adequate rest and personalised strategies for managing stress and wellbeing. Avoid suggesting that emotional stress alone explains or invalidates a person’s pain.

Case Studies

Turn the learning from the video into practice with these three case studies. Click the buttons to expand each case study and work through them in order.

☀️ Hot weather

Several hours outdoors.

🚶 Physical exertion

Walking and standing throughout the day.

💧 Limited fluids

They drank very little water.

😴 Fatigue

They had a late night the previous evening.

Now, click on the interactive question and choose the factors you think contributed to this person’s crisis before revealing the answer.

Interactive Question

Which factors may have contributed to this person’s crisis?

Answer

All of the above. This case demonstrates how several relatively common factors can combine to increase physiological stress and the risk of sickling.

What additional questions would you ask during your assessment?

You might ask:

  • When did the pain start, and how has it changed?
  • How much fluid have you had today?
  • How long were you outdoors and physically active?
  • Did you have opportunities to rest during the day?
  • Have you taken your usual medication and any pain relief?
  • Are you experiencing any chest pain or difficulty breathing?

Remember: Identifying triggers is only one part of the assessment. Continue to assess the person and listen to their knowledge of their own sickle cell disease and usual crisis pattern.

Day One

Fever and fatigue

Day Two

Reduced appetite and fluid intake.

Day Three

Increasing pain, chest discomfort and breathlessness.

Now, click on the interactive question, thinking about what would concern you about how this person is presenting in your setting.

Interactive Question

What should concern you most about this presentation?

Answer

Correct answer: C. Infection can trigger a vaso-occlusive crisis, but new chest pain or discomfort and increasing breathlessness should raise concern about acute chest syndrome, a potentially life-threatening complication requiring urgent assessment.

Suggested Actions

You might ask:

  • Arrange urgent clinical assessment — chest symptoms and increasing breathlessness in someone with sickle cell disease require prompt investigation.
  • Assess vital signs and oxygen saturation — look for evidence of respiratory compromise, fever or clinical deterioration.
  • Escalate concerns promptly — consider the possibility of acute chest syndrome and follow the appropriate local clinical pathway.
  • Take the patient’s symptoms seriously — do not assume that chest discomfort is simply part of their usual pain crisis.
  • Assess for infection and other complications — consider how infection, vaso-occlusion and acute complications may be occurring together.
  • Listen to the patient’s knowledge of their condition — ask whether these symptoms are different from their usual crisis pattern.

Do not become so focused on identifying the trigger that you overlook a developing complication. New symptoms, breathlessness or clinical deterioration require prompt assessment and escalation.

🏠 Home environment

Is the home consistently warm? Are there problems with damp, draughts or inadequate heating?

💼 Work and Daily Routine

Does the person’s work or daily routine involve prolonged exposure to cold, outdoor working or environments where they cannot easily keep warm?

🚍 Travel and Cold Exposure

How does the person usually travel, and are they regularly exposed to cold while walking, waiting for transport or during long journeys?

💷 Ability to heat the home

Are financial pressures affecting the person’s ability to maintain a comfortable temperature?

Now, click on the interactive question, thinking about what would concern you about how this person is presenting in your setting.

Look Beyond the Trigger

Cold weather” may be the immediate trigger, but the underlying issue could involve poor housing, fuel poverty, working conditions or difficulty accessing suitable transport.

Reflection

How might your response differ if the patient cannot simply avoid the trigger?

Suggested Actions

You might ask:

  • Explore the barriers with the patient — ask what makes avoiding the trigger difficult rather than assuming they can simply change their circumstances.
  • Agree realistic risk-reduction strategies — consider what changes are achievable within the person’s home, work, travel and daily routine.
  • Consider workplace adjustments — where appropriate, discuss whether changes to duties, working environments, breaks or outdoor exposure could help.
  • Consider practical and financial support — housing problems or difficulty affording adequate heating may require signposting to appropriate local advice and support services.
  • Support planning for unavoidable exposure — explore warm clothing, travel planning, opportunities to warm up and strategies for reducing sudden temperature changes.
  • Work collaboratively — ask the person what has helped previously and what support they feel would make the greatest difference.

Preventative advice must be realistic and achievable. If a patient cannot avoid a trigger because of housing, employment, or other barriers, repeating generic advice may achieve very little.

Good Practice vs Common Pitfalls

Good Practice
Avoid

Explore possible triggers during assessment

Assuming there must always be a single trigger

Recognise multiple interacting factors

Suggesting the patient “caused” the crisis

Provide personalised prevention advice

Giving generic advice without context

Consider social and environmental factors

Ignoring housing, work or financial circumstances

Remember

Identifying possible triggers should improve future care.

It should never be used to question the legitimacy of pain or imply responsibility for a vaso-occlusive crisis.

Downloadable Resources

Clinical Trigger Assessment Guide
Trigger Assessment Questions
Trigger Prevention Advice Sheet

Knowledge Check

Complete the short knowledge check before moving to the next lesson.

START KNOWLEDGE CHECK

Key Takeaways

  • Multiple triggers often interact rather than acting alone.
  • Identifying triggers supports prevention and personalised care.
  • Assessment should explore environmental, physiological and social contributors.
  • Trigger awareness should inform compassionate care, not judgement.
  • Triggers increase physiological stress and promote sickling.

Continue Your Learning

You now have a good understanding of the triggers that contribute to sickle pain crises. It’s time to move onto Lesson 4 – Beyond Pain: Symptoms, Complications and Common Misconceptions

Back to Module 1 Review
Continue to Lesson 4 – Beyond Pain: Symptoms, Complications and Common Misconceptions