Gene frequencies of the HPA-1 platelet antigen alleles in the Lebanese population.

The objective was to study the gene frequencies of HPA-1 in the Lebanese population for the first time. The aims of this study were to assess the prevalence of 1a and 1b HPA-1 alleles in healthy Lebanese individuals and compare with the international literature. Human platelet antigen (HPA) systems are involved in alloimmunization, organ transplantation rejection and the development of cardiovascular disease. Of several classified HPA systems, HPA-1 specifically has been considered to be the most important antigenic system implicated in the Caucasian population. This specific gene has never been investigated in our population. DNA was extracted from specimens collected from 205 healthy unrelated Lebanese individuals and tested, using a reverse hybridization polymerase chain reaction (PCR) assay, for the prevalence of 1a and 1b HPA-1 alleles. Genotypes 1a/1a, 1a/1b, and 1b/1b were assigned accordingly. We observed that the 1a/1a genotype was the most prevalent (65.85%) followed by 1a/1b (30.24%) and 1b/1b (3.91%) with allelic frequencies for 1a and 1b of 0.81 and 0.19, respectively. As compared with other ethnic groups, the Lebanese population was found to have a relatively high prevalence of the HPA-1b, which may predispose to a higher risk of alloimmunization. This report is the first to study the prevalence of the HPA-1 system in the Lebanese population and serves as a template for future clinical research involving platelet disorders and cardiovascular diseases.

An unusual case of hyperkalaemia-induced cardiac arrest in a paediatric patient during transfusion of a 'fresh' 6-day-old blood unit.

A well-recognized complication of the transfusion of red blood cells (RBCs) is hyperkalaemia. This occurs in paediatric or adult patients receiving massive transfusion and can lead to cardiac arrest. Hyperkalaemia may follow the transfusion of 'stored' RBCs and/or haemolysed units, and depends on the quantity and rate of transfusion. We report on an unusual case of hyperkalaemia-induced cardiac arrest during transfusion of a 'fresh' blood unit. A 62-day-old baby girl was scheduled for a construction of a Blalock-Taussig shunt, after the completion of anastomosis, and upon release of vascular control, there was bleeding at the anastomotic site that was controlled with a suture placement. To compensate for the blood loss, a stat order was given for a push of 120 mL of RBCs over 10 min through the inferior vena cava central line. The blood unit was 6 days old and had been gamma-irradiated 48 h earlier. Shortly after the transfusion, the patient's electrocardiogram showed changes typical of hyperkalaemia; she then went into cardiac asystole. The blood unit potassium concentration was 55.3 mmol L-1, which flushed the atrioventricular node during transfusion. This is the first report of a high potassium level found in a 'fresh', less than 7 days old, nonhaemolysed RBC blood unit. The high concentration of potassium in this unit seems to be due to accelerated alterations of the RBC sodium/potassium adenosine triphosphatase pump (Na+/K+ pump), resulting in the release of intracellular potassium. This early and severe alteration of the pump and the unusually high potassium level may be due to as yet unexplained causes, warranting awareness, future investigation and routine saline washing of 'fresh' RBCs for paediatric patients who are candidates for central line transfusion.

Thrombotic thrombocytopenic purpura in a case of scleroderma renal crisis treated with twice-daily therapeutic plasma exchange.

We report the rare complication of thrombotic thrombocytopenic purpura (TTP) in an elderly patient with the uncommon scleroderma renal crisis (SRC) at the advanced age of 85 years. Initially, she was treated by standard daily one and a half plasma volume therapeutic plasma exchange (TPE), in combination with steroid therapy. Due to an unsatisfactory clinical response, she was consequently, treated by an intensive twice-daily one and a half plasma volume TPE regimen. Although there was an increase in the platelet count, a 7-day course of the intensive regimen did not elicit further propitious laboratory test results or a clinical improvement and the patient expired secondary to the pulmonary and cardiac conditions related to SRC. Intensive TPE administration has been advocated in few specific patients who are refractory to standard daily treatment. The unfavorable outcome in this case may be attributed to the multiple complications associated with her primary disorder. In conclusion, we observed intensive twice-daily TPE to increase temporarily the platelet count, but not to be of benefit in a patient with SRC and multiple organ failure. The two TPE regimens and outcomes are compared and the pathogenesis of TTP and scleroderma are discussed.

Deterioration of gas exchange in patients with severe thrombotic thrombocytopenic purpura with respiratory failure during therapeutic plasma exchange.

Therapeutic plasma exchange (TPE) is a procedure performed on patients suffering from various disorders, including thrombotic thrombocytopenic purpura (TTP). As we noted a frequent transient deterioration in respiratory function when the procedure was performed on intensive care unit (ICU) patients, we studied retrospectively the incidence of respiratory deterioration during and shortly after TPE and looked for a probable correlation with a change in the white blood cell (WBC) counts. Over a period of 10 months six patients with TTP, five of whom had parenchymal lung disease due to different medical reasons, underwent TPE. The oxygen saturation was measured continuously before, during, and after TPE; additionally, the WBC and differential counts were measured pre- and post-TPE. The ratio of the oxygen saturation by pulse oxymetry (SpO2) to the fraction of inspired oxygen (FiO2) was calculated before, during and after TPE. In these five patients with lung disorders, there was a consistent trend of a decreasing SpO2/FiO2 quotient during and within 2 h post TPE compared to the pre-TPE value. The decrease in SpO2/FiO2 range was 0.20-0.89 with an average of 0.56. In the same 5 patients there was an increase in the WBC count in the range of 2.3-19.7 x 10(9)/L with an average increase of 9.3 x 10(9)/L. The percent neutrophils of the total WBC counts also increased following most of the sessions, this increase was in the range of 1-15 % with an average of 7%. The effect of TPE on the SpO2/FiO2 ratio and the correlation to the WBC count and to a possible neutrophil activation has not been previously reported. We postulate that TPE can accentuate respiratory deterioration in patients with TTP who already have acute lung injury. This may be due to the priming and activation of the leukocytes that could lead to the release of cytokines and inflammatory mediators during the procedure. Thus, it is important to be aware of the possible deterioration in respiratory function and gas exchange while administering TPE to patients with pre-existing parenchymal lung injury.

Lebanese population: prevalence of the erythrocyte phenotypes.

STUDY OBJECTIVES: This survey was designed to be a descriptive study of the erythrocyte phenotype prevalence in Lebanon. The general aim was to provide transfusion centers and blood banks with the occurrence of the nation's erythrocyte phenotypes in the population they are serving. The results were descriptively compared to Caucasians. SUBJECTS AND METHODS: 632 blood samples were collected from the Lebanese population in the 5 muhafazats (regions). Of which, 350 samples were extensively phenotyped for the blood group systems ABO, Kell, Kidd, Duffy, MNS, Lewis, Lutheran and P; and 282 samples were selectively phenotyped for Fy(a), Fy(b) and Kp(a). Additionally, 3064 random blood donors were studied for the ABO and D blood groups. MAIN RESULTS: With respect to the blood group phenotypes, the Lebanese are similar to the Caucasian population with the exception of rr, Le(b), Le (a-b-), Fy (a-b-), M+N+S-s+ and M-N-S-s+. CONCLUSION: It is of scientific cognizance and interest that the Lebanese erythrocyte phenotypes closely resemble that of the Caucasians: nevertheless, certain novel differences are present, and possibly, there exists a phenotype that attributes to admixture of the African gene in a Middle Eastern population.

Thrombotic thrombocytopenic purpura in a patient with rheumatoid arthritis treated by plasmapheresis.

Thrombotic thrombocytopenic purpura (TTP) is a multisystem disorder characterized by consumptive thrombocytopenia, microangiopathic hemolytic anemia, and neurologic symptoms. TTP is associated with many diseases and several therapeutic drugs. We report the rare case of a patient with rheumatoid arthritis who developed TTP that was not associated with drug therapy, 18 months after the onset of rheumatoid arthritis. She recovered from the TTP following daily sessions of therapeutic plasma exchange (TPE) with fresh frozen plasma replacement and glucocorticoid therapy. Recent pathogenic mechanisms are reviewed as they relate to von Willebrand factor. In this report of the rare association of TTP with rheumatoid arthritis, an immediate relationship is likely because both are of an immune nature. Awareness of the possible development of TTP in rheumatoid arthritis is important for early diagnosis and treatment.