Preliminary trial of minidose heparin prophylaxis for painful sickle cell crises.

Four patients with well-documented severe recurrent painful sickle cell crises received 12-month courses of self-administered minidose heparin (5000-7500 units every 12 hours). Patients were evaluated weekly or bi-weekly for symptoms and signs of sickle crises. The observations were compared with identical observations during 12 months off heparin (control). Prior to starting heparin, baseline laboratory values were established, including hematocrits, platelet counts, and plasma coagulation factors. Bone density was evaluated by radiologic measurement of metacarpal cortical width and by forearm transmission osteodensitometry. Laboratory values were repeated at each visit; bone density was reevaluated every 6 months. At each visit clinical status for the preceding 1-2 weeks was classified as: no pain (I), minor pain controllable by non-prescription medications (II), pain requiring office or emergency room admissions for parenteral narcotics (III), hospitalized for about 3 days for pain crisis (IV). One patient completed a single 2-year cycle; one patient completed 2 cycles (followed 4 years), and 2 patients have undertaken 3 cycles (followed greater than or equal to 6 years). No treatment-related complications occurred requiring discontinuation of heparin. Thrombocytopenia was not observed. There was no evidence of progressive osteopenia. All patients improved while receiving heparin; 1 moderately, 3 markedly. Cumulative data (8.7 patient years on heparin, 12 control years) revealed a 73% reduction in days of hospitalization per year and 74% reduction in hours spent in emergency rooms per year during heparin administration. Pretreatment pain patterns recurred when heparin was discontinued.