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Case
The patient is illustrative. Mr. O., 24, has sickle cell anemia (HbSS). He arrives at the emergency department with severe pain in his lower back and both legs that began 8 hours ago, after a week of a cold and poor fluid intake. He rates the pain 9 out of 10. Temperature 37.9 °C, heart rate 112, respiratory rate 20, SpO₂ 95% on room air. His hemoglobin is 7.4 g/dL (his baseline is about 8), reticulocyte count is raised and bilirubin is mildly high. He has had four similar crises in the past 12 months and takes no disease-modifying therapy.
Pathophysiology
The genetic change. Sickle cell disease is a group of inherited disorders caused by mutations in HBB, the gene for the β subunit of hemoglobin (Kato et al., 2018). In sickle cell anemia, both copies carry the sickle mutation, so red blood cells contain mostly hemoglobin S.
Polymerization and sickling. When hemoglobin S gives up its oxygen, the molecules can polymerize into long, stiff fibers. Red cells filled with these polymers become rigid and sickle-shaped (Kato et al., 2018). Dehydration makes this worse by concentrating hemoglobin inside the cell, and infection and fever add inflammatory stress, both of which fit Mr. O.'s week of illness.
Hemolysis. Sickled cells are fragile and break down early, causing chronic hemolytic anemia. That explains his low hemoglobin, high reticulocyte count and raised bilirubin.
Vaso-occlusion. Rigid cells, together with activated endothelium, white cells and platelets, stick together and block small vessels. Downstream tissue becomes ischemic, which causes the severe pain of a vaso-occlusive crisis and, over time, damages organs throughout the body (Kato et al., 2018).
Complications to watch for
- Acute chest syndrome: a new lung infiltrate with fever or respiratory symptoms, a leading cause of death in sickle cell disease. Pain and opioids can reduce deep breathing and raise the risk.
- Stroke: sudden neurological signs need emergency evaluation.
- Infection: loss of normal spleen function makes him vulnerable to severe bacterial infection, so fever must be taken seriously.
Management and how it fits the pathophysiology
The National Heart, Lung, and Blood Institute expert panel's evidence-based report (Yawn et al., 2014) makes strong recommendations that apply to Mr. O.:
| Recommendation | Link to pathophysiology |
|---|---|
| Rapid initiation of opioids for severe pain in a vaso-occlusive crisis | Ischemic pain is severe and undertreatment is common |
| Incentive spirometry while hospitalized for a crisis | Encourages deep breathing to prevent atelectasis and acute chest syndrome |
| Hydroxyurea for adults with 3 or more severe vaso-occlusive crises in 12 months, or with pain or anemia that interferes with daily life | Hydroxyurea raises fetal hemoglobin, which interferes with hemoglobin S polymerization |
Supportive care includes fluids for his dehydration, without overloading him, and a careful search for infection.
Advanced practice considerations
Mr. O. meets the criteria for hydroxyurea, which he isn't taking. Before discharge, the advanced practice nurse should start a conversation about disease-modifying therapy, arrange follow-up with a sickle cell center, review his vaccinations, and make an individualized pain plan for future crises. Patients with sickle cell disease often report being treated as drug-seeking in emergency departments, so prompt, respectful pain management is also a matter of equity.
References
Kato, G. J., Piel, F. B., Reid, C. D., Gaston, M. H., Ohene-Frempong, K., Krishnamurti, L., Smith, W. R., Panepinto, J. A., Weatherall, D. J., Costa, F. F., & Vichinsky, E. P. (2018). Sickle cell disease. Nature Reviews Disease Primers, 4, Article 18010. https://doi.org/10.1038/nrdp.2018.10
Yawn, B. P., Buchanan, G. R., Afenyi-Annan, A. N., Ballas, S. K., Hassell, K. L., James, A. H., Jordan, L., Lanzkron, S. M., Lottenberg, R., Savage, W. J., Tanabe, P. J., Ware, R. E., Murad, M. H., Goldsmith, J. C., Ortiz, E., Fulwood, R., Horton, A., & John-Sowah, J. (2014). Management of sickle cell disease: Summary of the 2014 evidence-based report by expert panel members. JAMA, 312(10), 1033–1048. https://doi.org/10.1001/jama.2014.10517
