SUMMARYThe effect of acute hypoglycaemia on platelet function was examined in patients undergoing an insulin stress test. Enhanced platelet aggregation was observed in all cases but platelet count, platelet adenine nucleotides, and the plasma level of von Willebrand factor were unchanged overall.The onset of the hypoglycaemia-induced increase in platelet aggregation coincided with the lowest blood glucose levels recorded and with the clinical signs of adrenaline release. Increased platelet aggregation was maintained thereafter for the two-hour test period. There was no apparent correlation with changes in cortisol, growth hormone, and prolactin. No change in platelet function was observed after the administration of L-dopa.We suggest that the measurement of platelet aggregation during a standard insulin stress test may provide a means of evaluating platelet function in vivo and the influence of drugs thereon.

in these patients, and lower doses of dipyridamole had a proportionately lesser effect on the improvement of platelet survival. Aspirin appeared to have a potentiating effect on dipyridamole, however, in that 1 g, combined with 100 mg of dipyridamole daily in a single dose instead of 400 mg in divided doses, prevented valvular platelet consumption. We decided to assess this synergistic effect of the combined drug regimen on the in-vitro platelet reactions before and after general surgery (the results of which will be reported elsehwere) and on the incidence of postoperative DVT, which is initiated by the adhesion of platelets to damaged vascular endothelium, followed by platelet aggregation to form a platelet mass. This mass is then consolidated by the deposition of fibrin.The dipyridamole and aspirin regimen has several attractive features. Firstly, the drugs are simple to administer and even if the patient is on nasogastric suction the tablets can be crushed and dissolved and given through the tube, the suction being turned off for two hours. Repeated platelet function studies before and after administration of the drugs showed that, no matter which technique was used, a definite effect on the platelet functions was achieved. Secondly, the potentiation of the action of dipyridamole by aspirin meant that the dose of dipyridamole could be reduced to 100 mg, and yet a considerable effect on platelet function was still detected. This greatly reduced the hypotensive and other side effects of the drug, which caused a 25% rejection rate in Browse and Hall's trial. No patient in our series had side effects that could be attributed to dipyridamole and there were no complications that could be attributed to the use of the drug combination.The administration of low-dose subcutaneous heparin has been successful in preventing postoperative thromboembolism.2 6 27 But more recently Evarts and Alfidi28 reported that the administration of low-dose subcutaneous heparin did not afford protection for patients undergoing hip surgery.The regimen of antiplatelet drugs described (aspirin and dipyridamole) shows promise of being an effective and simple method of reducing the incidence of postoperative DVT. It is easy to administer and no complications have so far been noted.We thank Professor R C Bennett for his advice and helpful criticism,

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A case of acquired von Willebrand's syndrome (vWs) is described which appeared to be due to antibodies directed against factor VIII clotting activity (FVIIIC), factor VIII-related antigen (FVIIIRAg) and von Willebrand factor. The antibodies directed against FVIIIRAg was demonstrated by the inhibitory effect of a platelet eluate on Ristocetin-induced aggregation of normal platelets. This effect was not shown by the patient's platelet-poor plasma alone, nor could it be demonstrated in platelet eluates from 13 other patients who had antibodies to FVIIIC but in whom there was no evidence of an acquired vWs.

In a survey of 210 young haemophiliacs living in South-east England it was recently shown that, by modern standards, under 20% received adequate treatment (Dormandy et al., 1967 (Bennett and Dormandy, 1966). A total of 1,304 pints (in 500 ml. units) of blood were used. The 914 pints which were collected by the plastic-bag method and processed at the haemophilia centre yielded 2,019 blood components, which were used separately. Supernatant plasma left after the separation of cryoprecipitate was given to three patients with Christmas disease (factor IX deficiency) and to one patient with plasma thromboplastin antecedent (factor XI) deficiency. Specific assays for factor IX and factor XI activity were carried out on these preparations. Plasma PreparationsDonors were bled either at the hospital or at regular bloodtransfusion sessions. Of the hospital donors, 70 underwent single plasmapheresis-that is, the separated red cells from the pint (500 ml.) of blood donated were immediately returned to the donor (Kliman and Schwab, 1961). By means of this procedure donors could be bled at intervals of one to two weeks.Cryoprecipitate.-Donors were bled into Fenwal JD-2 double plastic bags, consisting of a primary blood pack connected to a satellite bag. 500 ml. of blood was collected in not more than 10 minutes. The blood was spun within two and a half hours of taking (often immediately) at 4,600 g for 20 minutes at 40 C. and the plasma separated. The satellite bag containing the plasma, which was not severed from the primary blood pack, was frozen in a C,-ice-alcohol mixture. minutes at 40 C., and the supernatant plasma was run back into the primary blood pack. Alternatively, the supernatant plasma was collected into a third bag, and the packed red cells in the primary blood pack were issued as such. (A triple-bag system allows this transfer to be carried out without opening the closed system.) In either case 10-15 ml. of plasma was left with the cryoprecipitate in the satellite bag, which was stored at -30°C. On use the thawed cryoprecipitate from up to five satellite bags could be collected into a single 50-ml. syringe for injection. Washing out the series of satellite bags with 10 ml. of saline permitted the collection of the residual cryoprecipitate (equivalent to the factor VIII activity of up to one extra bag of cryoprecipitate).Supernatant Plasma.-When this was not used for the reconstitution of the red-cell mass, the supernatant plasma separated from the cryoprecipitate was used in the treatment of coagulation defects in patients with a deficiency of either factor IX or factor XI.Fresh-frozen Plasma in Plastic Bags.-The first stages in the preparation of fresh-frozen plasma were as above, with the exception that the plasma in the satellite bag was severed from the primary blood pack. (1962). Assays, which were all done in the hospital laboratory, were carried out as follows: (1) on the plasma at the time of donationj; (2) on the plasma or cryoprecipitate at the time of thawing for therapeutic use ; (3) on the supern...