This experiment is thought to reflect the natural history of Y. enterocolitica contamination of blood, in which complement-resistant organisms in the donor blood encounter lower temperatures after donation. These observations suggest that the practice of plasma depletion may have contributed to the increased incidence of mortality due to Y. enterocolitica contamination of donated blood.

Objective To identify the reasons behind failures to prevent the development of Rhesus (D) haemolytic disease of the newborn. Design Retrospective analysis of the case records of all pregnancies that resulted in the birth of an infant with a positive direct antiglobulin test on the cord red cells born to Rh(D) negative women between 1 April 1985 and 31 March 1990. Setting Obstetric units in the South East Scotland region and the South East Scotland Regional Blood Transfusion Service Antenatal Laboratory. Main outcome measures The causes and clinical consequences of maternal immunisation to the Rhesus (D) antigen. Results Between 1985 and 1990, 80 pregnancies resulted in the birth of an infant sensitised with anti‐D on the cord red cells. There were no deaths due to haemolytic disease, but considerable resources were deployed in obstetric and neonatal care for these pregnancies. Sufficient data were available to categorise the cause of maternal immunisation in 70 pregnancies. Seven cases were due to immunisation by pregnancy before 1970. Sixty‐three cases could be attributed to failure of the Rhesus programme: 10 cases (16%) were due to failure to implement the programme adequately, the other 53 cases (84%) were due to failure of the current guidelines to provide adequate protection. Late immunisation in an uncomplicated pregnancy was the single commonest identifiable cause. Conclusions It is likely that substantial further reductions in Rhesus (D) immunisation and haemolytic disease of the newborn will require changes in the Rhesus prevention programme. In particular the role of antenatal prophylaxis requires detailed consideration.

Within a 24-month period, 5 patients in a large teaching hospital were mistakenly transfused with blood that had been crossmatched for different patients. Each of the incidents was due to failure by ward staff to adhere to established safely procedures. Three incidents were entirely due to failure to make the standard checks comparing the identity details on the blood pack label with the patient identification details. The fourth incident was due to a combination of inadequate checking and incomplete patient identification procedure. The fifth incident was due to a series of errors that consisted of inadequate checking, plus putting the wrong patient's blood into the sample tube, plus misspelling of the patient's name on both sample tube and request form. There was no serious morbidity. All of these incidents took place when an unusual coincidence or contributing error lead to unmasked inadequate checking of blood unit against patient's identity by ward staff. The incidence of inadequate checking technique may be much higher than the incidence of erroneous transfusion events. It may be difficult to test the ability of an 'improved' transfusion procedure to prevent disasters from erroneous unit-to-patient matching, since assessment will need to include actual 'worst case' situations, which should be rare.

Aims-To examine how delayed refrigeration of blood affects the growth of Pseudomonas fluorescens, one of the two most important causes of sepsis resulting from transfusion of contaminated blood. Methods-Two donations of whole blood were each divided into three aliquots and inoculated with 5-10 cfu/ml of a P fluorescens strain from a case of transfusion associated sepsis. From each donation, one aliquot was placed at 4°C, one was held at 20°C for six hours prior to refrigeration and the third was held at 20°C for 24 hours prior to refrigeration. Samples were aseptically withdrawn over 17 days and bacterial counts were determined using a pour plate technique. Results-The rate of growth of Pfluorescens in blood at 20°C was increased compared with blood at 4°C. At 24 hours the aliquots held at 20°C for six and 24 hours had, respectively, 174 and 29 000 cfu/ml compared with 15 cfu/ml in aliquots held at 4°C. There was no evidence ofincreased killing of Pfluorescens at the higher temperature. Conclusions-These results suggest that blood for transfusion should be refrigerated as soon as possible after collection. ( Clin Pathol 1995;48:717-718) Keywords: Pseudomonas fluorescens, blood, contamination, refrigeration. We set out to determine how a delay in refrigeration ofdonated blood might affect the growth of Pfluorescens, which probably derives from the donor's skin." Simple experiments involving inoculation of small numbers of organisms into freshly donated blood are therefore likely to accurately reflect real contamination events. MethodsPfluorescens strain 079 was isolated from a fatal transfusion reaction involving contaminated platelet depleted blood.'2 The organism was cultured in nutrient broth at 30°C overnight. Aliquots (02 ml) of the broth culture were added to 1 8 ml volumes of nutrient broth containing 10% glycerol and stored at -20°C. One vial was thawed, and a viable count performed to calculate the dilution required to inoculate blood samples.Donations of whole blood were split into aliquots of approximately 100 ml and weighed to give individual volumes. Each aliquot was fitted with a sampling site coupler. A vial of P fluorescens culture was thawed and diluted in saline, and inoculated into each aliquot ofblood to achieve a concentration of 5-10 cfu/ml. In the first series of experiments two aliquots from each of six donors were incubated at 4°C for 17 days; another two aliquots from each donation were first stored at 20°C for 24 hours and then placed at 4°C for the next 16 days. In second series of experiments separate aliquots from each of two donors were stored at 4°C after initial incubation at 20°C for zero, six and 24 hours, respectively.Samples were withdrawn for bacterial culture immediately after inoculation to determine the actual size ofinoculum, and subsequently at intervals up to 17 days. On each occasion a 3 ml sample was collected from each bag and mixed with 150 jld of 10% (w/v) saponin (Sigma, Poole, Dorset, UK) to lyse red cells. Triplicate pour plates were prepared by mixin...