Summary.Red cell exchange is important in the care of acutely ill sickle-cell patients, and may be life-saving. An automated red cell exchange technique has been developed using a Baxter blood cell separator, enabling an isovolaemic exchange to be performed within 2·5 h. A total of 20 procedures have been performed in 15 patients, including one woman in the third trimester of pregnancy, with a mean decrease of 72% in the circulating sickle haemoglobin (HbS) level. This method enables almost all adult patients with sickle cell anaemia to have their HbS reduced to safe levels by only one procedure. The procedure was well tolerated by all patients, including those who were acutely ill. This technique provides an effective procedure for reducing the percentage of circulating HbS rapidly in acutely ill patients with complications of sickle cell anaemia.
In severe falciparum malaria with high parasitaemia, removal of parasitized erythrocytes is generally considered to be of value as adjunctive therapy in addition to standard chemotherapy. Such removal is commonly achieved by exchange transfusion but this procedure is time-consuming and may be associated with haemodynamic disturbance. Current-generation automated cell-separator hardware and software allows prompt red cell exchange, erythrocytapheresis, in a single continuous-flow isovolaemic procedure. We describe the application of this procedure to 5 cases of severe falciparum malaria in travellers returning to the UK from the tropics. All patients also received quinine and conventional supportive therapy. In all cases, dramatic reduction in parasitaemia was achieved within 2 h with subsequent complete clinical recovery. Erythrocytapheresis has significant advantages over exchange transfusion in terms of speed, efficiency, haemodynamic stability and retention of plasma components such as clotting factors and may thus represent an improvement in adjunctive therapy for severe malaria.
Introduction Effective therapies for Sickle Cell Anaemia (Hb SS) reduce blood concentration of HbS by transplanting erythroid stem cells or altering globin gene expression with hydroxyurea. A relatively stable reduction in HbS concentration intermediate between these approaches (10–45% HbS) can also be achieved by regular automated red cell exchange transfusion (RBCex), but concerns about cost-effectiveness, alloimmunisation, iron load, pathogen exposure and vascular trauma have limited the use of this treatment modality. Methodology A retrospective study of sixteen fully counselled HbSS individuals with serious complications undergoing regular RBCex with partially phenotype-selected, leucodepleted red cells for a median of 36 (range 11–65) months, for whom accurate pre- and post- RBCex admission data was available. The number of episodes of sickle-related hospitalisation and total inpatient days sustained per year by the group before enrolment in RBCex was compared to the number on RBCex. Excluded from analysis were patients having single RBCex for surgery, pregnancy, or non-recurrent acute complications, having manual exchange transfusions or unable to comply with regular RBCex. Four patients from other units were excluded because complete data on previous admissions was lacking. Target post-procedure haemoglobin was 10–11gm/dL (PCV = 0.31–33) and HbS% <15. Results Between September 1995 and July 2003, 547 RBCex procedures were performed on 56 patients (age: range 16–52 yrs, median 31.5 yrs, mean 29.7 years). Forty patients were excluded from analysis for reasons above. Analysed patients underwent a mean of 7.71 RBCex procedures per year (range 5.12–9.89, median 7.49). A mean of 7.8 (range 4.25–10, median 8) donor red cell units were transfused per procedure. RBCex was performed at a mean of 6.97-week intervals (range 5.26–10.16, median 6.91). Eleven patients (62.5%) required ‘in-out’ femoral vein Vascath insertion. Apheresis nurses placed all catheters in a day-care setting. In the five years before entering the program the patients experienced a mean of 2.03 inpatient episodes per year (range 0.4–5.2, median 1.6): on RBCex this fell to 1.02 per year [range 0–5.3, median 0.33 (p = 0.004)]. Inpatient days fell from a mean of 16.56 per year (range 2–40.6, median 11) to 8.27 [range 0–56.33, median 1.33 (p=0.007)] saving 208.87 in-patient bed days per year. The number of donor red cell units patients received increased from a mean of 15.15 per year (range 0.8–41.1, median 14.1) to 57.9 units per year [range 24–89.7, median 58.0 (p=0.004)]. No patient received any form of iron chelation. No increase in serum ferritin (p=0.796), or loss of vascular access sites, was identified. Two patients acquired new red cell alloantibodies (1-anti Kpa + anti-E; 1- non specific) during RBCex. Three already had alloantibodies (1 anti-e; 1 anti-Kpa + anti-C; 1 non-specific), but did not acquire any more while on RBCex. The presence of antibodies did not preclude continuing RBCex. No transfusion-related infections occurred. One patient died from unrelated causes at home. One novel phenomenon was identified: while on RBCex, ‘rebound’ crises tend to occur when HbS crosses the 45% threshold, emphasising the need for consistency using this therapy. Conclusion We contend that regular RBCex is effective therapy for carefully (self)-selected patients who severely symptomatic. It should be considered in those unresponsive to, or unwilling to take, hydroxyurea. Multidisciplinary support by a skilled team is essential.
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