Umbilical artery catheterization in the newborn.

Satisfactory care of the sick premature newborn baby requires investigations of blood gas tensions (Dahlenburg et al., 1968) and of various biochemical parameters, such as blood sugar, often at frequent intervals during the first few hours of life. Blood samples for biochemistry can be obtained from heel pricks or by venepuncture. Heel pricks are painful, may become infected, and the number which can be carried out is limited. Repeated venepuncture in the newborn carries its own not inconsiderable hazards (McKay, 1966; Asnes and Arendar, 1966). Blood can be obtained from umbilical venous catheters, but here air embolus is a hazard, as is portal venous thrombosis, though this is rare with greater attention to sterile techniques (Tizard, 1962); unless the umbilical venous catheter passes through the ductus venosus into the inferior vena cava it tends to wedge in a branch of the portal sinus and needs periodic manipulation before blood can be withdrawn. To obtain specimens for blood gas analyses direct arterial puncture or arterialized capillary blood can be used. To obtain blood by the latter route for accurate and repeated estimations requires considerable skill, and with the peripheral vasoconstriction often found in ill babies, the results may be inaccurate. In both cases the child is traumatized, cries, and may therefore lower his PaCO2. A haematoma may form round an arterial puncture and equilibrate with a high oxygen tension present in the skin if the child is being nursed in a high oxygen concentration, and give a falsely high PaO2 if it is aspirated. This especially applies to temporal artery puncture. It is again not practicable to obtain repeated samples by these routes. For these reasons sampling of arterial blood through an umbilical artery catheter is preferable for both biochemical and blood gas determinations. Before arterial catheterization could be considered