Accurate micromethod of neonatal blood sampling from peripheral arterial catheters

Blood sampling from peripheral arterial catheters is an important, but inadequately standardized, technique in neonatal intensive care. In this study two peripheral arterial sampling methods were evaluated in a neonatal animal model. One commonly used method (the drip technique) involves inserting a needle into the hub of the peripheral arterial catheter and discarding up to 10 drops of infusate fluid and blood before the sample is collected. This method was compared with a new micromethod where two needles are used (two-needle technique). Blood gas values in the peripheral samples were compared with control values drawn from a femoral artery catheter. Accuracy of peripheral arterial PCO2 and total blood loss constituted the final study variables. The results demonstrated that the two needle technique was more accurate, yielding peripheral arterial PCO2 values that were 98% of control values. Withdrawal of fewer than six drops of infusate fluid and blood with the drip technique resulted in spuriously low PCO2 values. The new technique also resulted in significantly less total blood loss per sample compared with the drip technique (189 +/- 3 microliters vs 398 +/- 3.8 microliters, mean +/- SEM, p < 0.01). We conclude that the two-needle micromethod is an accurate technique for blood sampling from peripheral arterial catheters and is particularly appropriate for low-birth-weight infants in whom minimization of blood loss is desirable.