Reports of aneurysmal dilatation involving Dacron aortic prostheses have raised questions concerning the incidence, degree and significance of postoperative alterations in graft size. Consequently, a study was undertaken to evaluate Dacron graft size by ultrasooud in 95 asymptomatic patients selected at random after aortic surgery. A Vidison Real Time ultrasound unit was used to determine the internal diameter of the aortic portion of the various grafts utilized: 41 Cooley knitted, 25 Vasculour-D; 13 U.S.C.I. ultralightweight; nine Wesolowski Weavenit; and seven DeBakey standard weight knitted. Patients were studied at from two weeks to 138 months postoperatively (average of 33 months). Hypertension was present in 64% of patients. In the total series, the degree of mean dilatation was 17.6%. Average dilatation in patients with normotension was 15% compared to 21% in hypertensive patients. Graphic analysis of the data collected indicated that dilatation of a significant degree occurs in the immediate postoperative period and slowly increases with time; the time regression period and slowly increases with time; the time regression lines for normotensive and hypertensive patients were almost parallel. Results of this clinical study appear to corroborate the results of in vitro quality control tests performed by two graft manufacturers (Meadox and U.S.C.I.).

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Triton WR-1339, while not bacteriostatic for virulent tubercle bacilli in vitro, has the ability to suppress tuberculosis in experimental animals (1-3).I n the course of studies in this laboratory on the effect of triton on guinea pig tissues it was noted that leucocytes exposed to the detergent either in vitro or in vi~o showed an increased resistance to disruption b y acetone and b y sonic vibration (4). Since surface-active agents chemically similar to triton are known to depress tuberculin sensitivity in guinea pigs (5) it seemed pertinent to determine whether it has any effect on the resistance of leucocytes to another form of trauma, namely in vitro eytolysis b y tuberculin (6).Materials and Methods 8urJace.-Aeti~e Agent.--Triton WR-1339 x was used throughout these studies. For injection of guinea pigs, a 12.5 per cent solution was prepared in 0.16 ~ sodium chloride and sterilized in the autoclave. Treated animals were given triton in a dose of 300 nag. per kg. of body weight. Control animals received an equal volume of saline. Injections were made subcutaneously in the groin.An/reals and D/eI.--An the guinea pigs used in this study were albino males weighing between 300 and 400 gin. They were fed daily with a stock diet of commercial pellets supplemented with fresh cabbage. The ~nlmals were sensitized by a single intramuscular injection of 1.0 cc. of sterile paraffin oil containing 5 rag. of heat-killed human type tubercle bacilli (I-I37Rv). Intradermal skin tests were done with 5 #g. of PPD (Sharp and Dolnne).Leucocyte Cytolysis Tests (7).--Heparinized blood samples were taken from adequately sensitized guinea pigs by cardiac puncture 48 hours after a tuberculin skin test. Aliquots (0.4 cc.) of blood were transferred to each of two siliconized serologic tubes. To one tube was added 0,1 co. of 0.16 u sodium chloride; to the other was added 0.1 cc. (5/~g.) of PPD dissolved in 0.16 J~ sodium chloride. The contents of the tubes were well mixed and total leucocyte counts were made using an AO Spencer hemacytometer. The tubes were then placed on a 37°C. water bath and mechanically shaken at a constant rate for 2 hours, after which a second leucocyte count was made. The PPD decrement was calculated as the per cent change in the tuberculin tube minus the per cent change in the saline control tube. In certain instances variations of this technique had to be employed, details of which will be described later.

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