Venous Pressure Measurement in Exchange Transfusion.

Exchange transfusion in small infants carries a mortality of 4-7 5% (Van Praagh, 1961; Boggs and Westphal, 1960). Many factors such as hypocalcaemia, circulatory overloading, hyperkalaemia, acidosis, citrate toxicity may be responsible, and the mode of death, whatever the aetiology, is usually thought to be acute cardiac failure (O'Neill and Gordon, 1959; Robinson and Barrie, 1963), and commonly the infant shows signs of cardiac failure at necropsy. When cardiac failure occurs the venous pressure, as measured through the exchange catheter, rises; however, central venous pressure will only be recorded if the catheter tip passes through the ductus venosus and into the inferior vena cava. Recently three observers (Rudolph, Drorbaugh, Auld, Rudolph, Nadas, Smith, and Hubbell, 1961; Burnard and James, 1963; Jegier, Blankenship, and Lind, 1963) have shown that the mean venous pressure in the normal newborn infant, whether it be measured in the right atrium or the inferior vena cava, is approximately 0 cm. H2O and similar to the central venous pressure in the adult; these pressures were measured with electrical manometers from catheters introduced through the umbilical vein and related to the sternal angle. Both Rudolph et al. and Jegier et al. noted that it was not always possible to pass a catheter through the ductus venosus and therefore, before any interpretation ofvenous pressure is made, it must be known with certainty that the catheter is in the inferior vena cava. The site of the catheter can be readily determined by watching for the pressure drop of 5-10 cm. H20 as the tip is advanced from between 8 to 12 cm. from the umbilicus; the respiratory pressure swings are also considerably larger in the thoracic inferior vena cava than in the portal sinus (Fig. 1). The data reported below confirm the findings just described and give some indication of the expectancy of passing an umbilical vein catheter through the ductus venosus during the first two days of life. Methods and Material