The value of capillary whole blood lactate for blood transfusion requirements in anaemia of prematurity

Objective: To evaluate the usefulness of blood lactate as an indication for blood transfusion in anaemia of prematurity by means of a study protocol which considers the site of blood sampling and the repeatability of lactate measurements. Design: Prospective clinical study. Setting: Multidisciplinary, neonatal-paediatric intensive care unit of a non-university, teaching children's hospital. Patients and methods: Comparison of pre- and 48-h post-transfusion capillary whole blood lactate in 18 anaemic premature babies. In 30 neonates the agreement between capillary and arterial lactate was analysed by using the Bland Altman plot. In 30 stable premature infants four capillary lactate measurements were carried out within 24 h and analysed with regard to variability (coefficient of variation (CV); association between SD and mean) and to establish normal values. Results: In the transfused infants, haematocrit increased from 23 (SD 3)% to 37 (SD 3)%. Mean lactate decreased from 2.5 (SD 1.0) to 1.7 (SD 0.5) mmol/l (p = 0.003). Pre-transfusion lactate did not correlate with pre-transfusion haematocrit, heart rate, respiratory rate, number of apnoeas/bradycardias and weight gain (multiple regression). The mean difference between capillary and arterial lactate was 0.17 (SD 0.24) mmol/l and the 95% confidence interval (CI) was -0.31 to 0.65 mmol/l. The CV of repetitive measurements was 19.8 (SD 9.8)% and SD correlated positively with mean lactate values (p = 0.001); the 95% CI (normal range for premature infants) was 1.56-1.90 mmol/l. Conclusions: Capillary whole blood lactate measurements in newborn babies agree excellently with arterial values. Lactate measurements add little information to the decision whether to transfuse or not, considering the variability of this parameter in stable premature infants and the lack of correlation with other possible clinical indicators of compromised oxygen delivery.