Platelet deficiency a factor in diminished coagulability of the blood in anaphylaxis.

Delay or loss of coagulability of the blood in anaphylaxis has long been recognized. It is generally attributed to excess of antithrombin or to diminished thromboplastin. While making a study of the blood fibrin in canine anaphylaxis by the method of Foster and Whipple 1 observations were made which we believe throw further light on the phenomenon. In making the blood fibrin studies, approximately 9 cc. of blood, obtained by cardiac puncture, are discharged into a centrifuge tube containing 1 cc. of a 1.5 per cent sodium oxalate solution. The samples are then centrifuged at moderate speed for thirty minutes. Exactly 2 cc. of the oxalated plasma is discharged into 40 cc. of clotting solution. This consists of 0.125 per cent calcium chloride in physiologic salt solution. Normal oxalated plasma usually forms a jelly-like coagulum within one hour, whereas the plasma in fatal anaphylaxis may remain uncoagulated for days. Occasionally a feeble coagulum forms after several days. During the course of the work several thromboplastic agents were employed, but it was found that a small quantity of platelets obtained from normal plasma gave us the most trustworthy results. They are obtained as follows: Several hundred cubic centimeters of normal oxalated blood obtained by cardiac puncture from a fasting dog is centrifuged at a slow speed until the red cells have been well sedimented and a more or less turbid plasma remains. The plasma is then pipetted off into 15 cc. centrifuge tubes, and centrifuged at high speed (2700 r.p.m.) for about one hour. At the end of this time several millimeters of a pearly white sediment will be found in the tips of the tubes. This sediment on microscopic examination proves to be composed chiefly of platelets.