SICKLE CELL ANEMIA

Sickle cell disorders are the most common haemoglobinopathies (abnormal red blood cells) encountered in the United States. Sickle cell anemia (HbS) results from a mutation that changes the amino acid at position 6 on the beta chain from glutamic acid to valine. The homozygous state produces sickle cell anemia.

Sickle trait (HbAS) is the heterozygous (carrier) state; it can be affected by low oxygen levels. Sickle cell trait occurs in 8 percent of African Americans in the United States. Oddly enough, HbS confers a protective advantage against malaria infection. In general, however, sickle cell disorders have no advantages. Sickle cells are dehydrated, stiff and viscous: they flow poorly though small blood vessels, which can cause local hypoxia (low oxygen levels) and can lead to numerous complications.

Hypoxia, cold or dehydration can cause the red blood cells (RBC) to sickle. This may cause a sickle crisis, often manifested as pain. The sickle crisis may affect the bones, chest, abdomen and spleen. The pulmonary circulation is also particularly vulnerable to pulmonary vascular occlusion because it receives blood that has been deoxygenated, which allows sickling to happen. Chest symptoms may include pain and fever. Infections, such as pneumonia, meningitis and osteomyelitis are major problems. Effects on the central nervous system include stroke in about 8 percent of individuals with HbS.

Red blood cell count lifespan is shortened in all varieties of sickle cell disorders (normal RBC: 120 days; HbSS ( sickle cell trait): 17 days; HbSC (another form of HbS): 28 days). HbS patients commonly become severely anemic.

Fitness and Diving:
Recurrent sickle crises can impair an individual's ability to exercise. Pain associated with sickle cell disorder can confuse the diagnosis of DCI. Pulmonary function is also affected by HbS. Local hypoxia and the occlusion of vessels can affect nitrogen loading and unloading during dive decompression. Diving may make HbS worse, too. For persons with sickle cell disorder, diving is not advised.

Medication used in Treatment:
The treatment of sickle cell syndromes includes hydration, oxygenation and analgesics for the painful crises. Some new research projects include attempts to prevent RBCs from sickling and to reduce the effects of sickled red cells on blood flow.

Additional Information:
Georgia site-www.emory.edu:80/PEDS/SICKLE
Wellness Web-http://wellweb.com/INDEX/QSICKLE.HTM

(Guy De Lisle Dear MD, Alert Diver, Sept-Oct 1999.)