RESUMEN
Although heparin solution is widely used as an anticoagulant in blood gas analysis, alterations in blood gas measurements may occur when small sample volumes are diluted by heparin. Cook pressure tubing for infants and children and Gould pressure line for adults were applied to each of 10 adult patients whose cardiovascular fuction was normal. Arterial blood gases were measured serially after withdrawing 2,4,6,8,10 and 12 ml of flus-blood solutions from the Gould pressure connecting tubing, and 1,2,3,4,5 and 6 ml from the Cook pressure line, which were connected to a transducer through a 3way stopcock. In the Gould pressure tubing, the pH was unchanged from sample 2 and PaCO2, HCO3- and base excess were unchanged from sample 3. PaO2 did not change between the samples. In the Cook pressure line, the pH and base excess were unchanged from sample 2 and PaCO2, HCO3- and PaO2 from sample 3. We conclude that arterial blood should be withdrawn in volumes of at least 4ml by the Gould pressure connecting tubing and 3ml by the Cook pressure line to obtaine accurate results in blood gas analysis.