Blood sampling through umbilical catheters.

An in vitro study testing the reliability of chemical determinations on blood samples withdrawn through an umbilical catheter is described. Blood samples were withdrawn through three different sizes of umbilical catheters containing a solution of dextrose, sodium bicarbonate, and potassium. Using either a 5 French or a 3 1/2 French catheter, accurate results were obtained for pH, sodium, potassium, and glucose when measurements were made after an initial 4-ml blood sample was discarded. With an 8 French catheter, accurate results were obtained for pH, sodium, and potassium but plasma glucose determinations remained inaccurate after 6 ml of blood was discarded.