Correlation between capillary and arterial serum gentamicin concentrations in neonates

Critically ill neonates in newborn intensive care units require frequent monitoring of bodily functions. This monitoring includes sampling of blood for laboratory analysis. Blood samples are commonly obtained through and umbilical artery catheter. However, if an umbilical artery catheter is not in place, blood samples are frequently obtained by heel stick due to difficulties inherent in venous sampling in this age group. These difficultiesinclude the inability to find a suitable site for venipuncture, the fragility of the veins at this age, and the trauma associated with repeated sampling. Sirinavin, et al recommended that the method of heel stick sampling be used for the assay of antibiotics, such as gentamicin and kanamycin, when the only access is the same line through which the drug has been administered. This recommendation is based on the finding that obtaining blood specimens for antibiotic assay through the same intravenous line used for antibiotic administration may result in falsely elevated drug concentrations due to drug adhesion to the plastic tubing, or incomplete flushing of the line after drug administration. The object of this study was to determine the relation between gentamicin serum concentrations determined from arterial and heel stick capillary blood with and without manipulation of the foot.