Jaundice in Severe Infections

Field: Medicine (Health Sciences)

Blood-pressure Differences-Pascarelli and Bertrand MDICAMLHJOURNAL 75Attempts have been made to explain Hill's sign on the basis of flow phenomena.Friedberg (1956) writes: " Since the femoral artery is in a direct line with the aortic stream, while the brachial issues from the aorta at a right angle, the femoral artery receives not only the pressure head but also the velocity head of the aortic stream . . . in aortic insufficiency the velocity head is considerable, there is a pronounced excess of pressure on the femoral as compared with the brachial artery."Sodeman (1961) offers essentially the same hypothesis to explain differences in arm and leg systolic and diastolic pressures thought to exist in normals.He states that leg systolic pressure is commonly 20-30 mm.Hg higher and leg diastolic pressure is 10 mm.Hg or more higher than arm pressure.Such arm-leg pressure differences cannot be confirmed by intra-arter al measurements ; therefore explanations of this sort must be viewed with scepticism.There is also reason to question seriously the validity of results derived from cuff measurements correlating arm and leg pressure differences to severity of aortic insufficiency (Frank et al., 1964), degree of cardiac decompensation in aortic insuffi- ency (Pont et al., 1953), or distinction of functional from organic aortic insufficiency (Loewenberg, 1940).Intra-arterial studies do not confirm any of these impressions, and suggest that virtually no differences in arm and leg blood-pressures exist in supine persons with aortic insufficiency or in normal controls.A clinical sign based upon indirect cuff blood-pressure measurements should withstand the comparison test of direct measurement.In this study such discrepancies between direct and indirect pressures were encountered that the leg cuff was finally abandoned.A cuff that fits poorly or is too narrow can give pressure readings that are too high.This is especially true when using the leg cuff, where variations in the consistency of the large fat-and-muscle mass create a need for variable amounts of pressure to compress a relatively deep artery of large calibre (Trout et al., 1956).Most available leg cuffs fit the conical shape of the thigh poorly, and contribute to artifact by actually compressing only a narrow band of tissue.In addition, auscultation or palpation of leg arteries is often difficult.All of the various factors mentioned probably con- tribute to the inaccuracy of indirect leg-pressure measurement.The problem of when to use a cuff on the lower limbs is a practical one.Existing leg cuffs are inaccurate.Perhaps their use should be abandoned until a better cuff is designed, in order to avoid being misled.Palpation of the femoral artery affords a quick and easy appraisal of the situation, and can give valuable clues to the existence of aortic coarctation or aorto-iliac stenosis.When doubt exists, direct arterial puncture can give accurate data safely and easily.If strain gauges and a multichannel recorder are not readily available for intra-arterial measurements, an inexpensive device such as that described by de Bono (1963) can be employed.Summary Disproportionate femoral systolic hypertension in aortic insufficiency (Hill's sign) is based upon values obtained by indirect cuff determinations made in the arms and legs.Direct arterial punctures, using strain gauges and a multichannel recorder, in 20 persons with aortic insufficiency compared with 50 controls failed to reveal the presence of this sign.As in the normal supine controls, blood-pressures in the arms and legs in aortic insufficiency were found to be virtually the same.Various explanations for Hill's sign were discussed and found to be inadequate.It is suggested that until a better leg cuff is devised diagnostic problems should be resolved by intra- arterial punctures of the femoral arteries.