Prostacyclin concentrations in haemolytic uraemic syndrome after acute shigellosis in children

The role of prostacyclin in the pathogenesis of haemolytic uraemic syndrome was evaluated in 11 children with acute shigellosis. Plasma concentrations of6-keto prostaglandin, Fla, a stable metabolite of prostacyclin, were measured by radioimmunoassay during acute illness, early convalescence, and after clinical recovery. Its concentration was low during acute illness in each patient, returning to normal concentrations or above at the time of the last sample. These results suggest that plasma prostacyclin may be involved in the development of the syndrome. Haemolytic uraemic syndrome (HUS) is one of the most important causes of acute renal failure in childhood in some regions of the world.' The association of severe shigellosis with HUS has been well established,2 3 but the pathogenesis of HUS remains unclear. Deficiency of prostacycin has been implicated in the pathogenesis of the syndrome.t1 Prostacyclin infusion has also been used in the treatment of HUS either with improvement" or equivocal results.'2 On the other hand, a recent study in five children with HUS showed that plasma 6-keto prostaglandin Fla (PGFIa), the sole stable degradation product ofprostacyclin (PGI2), was raised. 3 The present study was aimed at evaluating the concentrations of prostacyclin by measuring PGFIa after severe shigellosis in children during the acute and convalescent stages as well as after clinical recovery. International Centre for Diarrhoeal Disease Research, Bangladesh, GPO Box 128, Dhaka 1000, Bangladesh A N Alam N M Abdal W A Wahed B Rao M M Rahaman Institute of Postgraduate Medicine and Research, Dhaka, Bangladesh C A Kawser M Hoque Correspondence to: Dr Alam. Accepted 30 May 1991 Patients and methods SELECTION OF PATIENTS The study was designed to allow estimation of PGFia on each patient during the three different stages of the illness: on development of HUS (acute stage), during early convalescence (4-5 days after diagnosis of HUS), and on recovery (>15 days after diagnosis, or when serum creatinine concentrations return to normal). This was considered appropriate as each patient acted as his or her own control after recovery. To determine the normal value of prostacyclin, it was measured in 18 apparently healthy volunteers. One hundred children between 1 and 10 years of age (median age 6 years) with severe shigellosis (characterised by passage of frank blood in the stool with fever, abdominal pain, and signs of toxaemia) with a mean duration of nine days were screened between April 1985 and March 1986 for the development of HUS as indicated by a fall in packed cell volume, thrombocytopenia, and renal failure. Of these, 11 patients were studied prospectively when they developed leukaemoid reaction (white cell counts of >50x 109/1), clinical evidence of haemolysis, and oliguria (urinary output of less than 10 ml/kg/ day) despite adequate hydration. Development of microangiopathy was indicated by a sudden drop in the packed cell volume (>10% drop within the first week of hospitalisation and presence of more than 2% fragmented red blood cells on peripheral blood smears). Patients with septicaemia and other systemic illnesses were excluded from the study. The study had the approval of the ethics committee of the centre and an informed consent was obtained from the parent or legal guardian before any patient was included in the study. A finger prick blood sample for a complete blood count and peripheral smear was obtained on admission. Venous blood was collected without stasis for assaying prostacyclin by radioimmunoassay and for coagulation measurements, such as partial thromboplastin time, thrombin time, and prothrombin time using Boehringer coagulation assay kits (Boehringer Mannheim). Blood was also collected for culture, measurement of haptoglobin, and determination of serum protein, electrolyte, and creatinine concentrations. Rectal swab and stool were cultured on admission and the next day on MacConkey's agar and on salmonella-shigella agar for isolation of shigella. Blood was taken from patients during the acute stage of the illness after hydration, during convalescence, and on recovery. On each occasion 4 ml was collected using an ice cold syringe and was transferred into two tubes containing EDTA (0-7 mg/ml plasma). One tube was centrifuged at 1500 g for 15 minutes at 0°C to obtain platelet-poor plasma and the other tube was centrifuged at 150 g to collect platelet-rich plasma. Both samples were then stored at -20°C for subsequent determination of prostacyclin stimulating activity in the plasma samples. PGI2 production was measured by the method of Moncada et al.'4 This consisted of cutting fresh rabbit aorta into fine rings, kept in tris buffer (0-05M pH 7-5) on ice for not more than two hours. The rings were then incubated in tris buffer at 22°C for five minutes and washed in ice cold buffer. This step was repeated five times to remove the basal prostacyclin activity. Then, 75 p1 of plateletpoor plasma in 200 ml of buffer were incubated with 40 to 60 mg of the clear vascular tissue at 37°C for 15 minutes. At the end ofthe incubation, 1231 group.bmj.com on August 15, 2017 Published by http://adc.bmj.com/ Downloaded from