High phlebotomy losses have been demonstrated to be an important variable contributing to transfusion requirements in preterm infants. Portable microanalysis systems have been proposed to diminish phlebotomy losses in critically ill neonates. Objective: to investigate phlebotomy loss and transfusion requirements before and after implementation of a microanalysis system (i-STAT, Princeton, NJ). Methods: 48 infants(<1000 gms) were compared Pre (N=24) and Post (N=24) implementation at a single level III NICU by Student's t-tests. All data are expressed as mean±SD. There were no differences in gest age (Pre 26.6 ±2.2 vs Post 26 ±1.6 wks, p=.26), Bwt (Pre 778.3 ±161.9 vs Post 743.5±139.6 gms, p=.43), length of hosp (Pre 92.4 ±20.9 vs Post 89.3±21.4 days, p=.65), duration of mechanical ventilation (Pre 33.6±25.7 vs Post 35.5 ±18.5 days, p=.79), admission Hct (Pre 41.9±6.7 vs Post 43.1 ±7.2%, p=.56) or Hct on day 7 (Pre 38.3±5.2 vs Post 39.4 ±7.2%, p=.57), amt of blood transfused in the 1st week (Pre 33.6 ±23.9 vs Post 36.1 ±27.4 cc/kg, p=.74) or during the entire stay (Pre 95.8 ±53.3 vs Post 118.2 ±65.7 cc/kg, p=.20), number of transfusions in the 1st week (Pre 2.8 ±2.1 vs Post 3.1 ±2.5, p=.66) or during the entire stay (Pre 8.2 ±4.6 vs 9.8 ±6.1, p=.29), number of donors in the 1st week (Pre 1.3 ±.9 vs Post 1.5 ±.8, p=.62) or during the entire stay (Pre 4.8 ±2.6 vs Post 5.7 ±2.6, p=.25), and phlebotomy losses/kg in the 1st week of life (Pre 46.4 ±24.8 vs Post 38.2 ±17.1 cc/kg, p=.19) between groups. Total phlebotomy losses in the 1st week approached significance (Pre 30.0±16.3 vs Post 23.6 ±7.6 cc, p=.08). Post hoc power analysis with an alpha of.05 showed a beta of.8 for phlebotomy losses. Conclusion: Although rapid determination of blood gases and electrolytes is important for management of critically ill neonates, microtechnology did not significantly decrease phlebotomy loss or reduce transfusion requirements in our population. We speculate that blood tests not available for microanalysis such as coagulation profiles, serum drug levels, bilirubin levels, blood cultures, and complete blood counts may partially account for the lack of difference between the two groups.