Haemoglobin levels in premature infants.

Method of Investigation Two hundred blood samples were taken, 185 of these being from a scalp vein, 13 from other veins (external jugular, antecubital or femoral), and in two instances heel-prick specimens were used. About 0 5 ml. of blood was withdrawn into a well-fitting sterile 2 ml. all-glass syringe and placed at once in a tube containing a small quantity of dry heparin. After mixing 20 c.mm. of blood was pipetted into 4 ml. of 0 *04% ammonia solution. The haemoglobin percentage was then read off directly in an 'M.R.C. grey wedge photometer'. In this instrument a scale reading of 100%, is equivalent to 14 * 8 g. Hb/100 ml. All samples were taken and all readings made by the authors and the average of six readings was taken as the final result. The photometer itself was checked at frequent intervals against a grey screen of known density and on three occasions blood samples of known haemoglobin concentration supplied by the M.R.C. Haemoglobin Standards Scheme were tested. Readings made by each of us on these occasions did not vary by more than 0 5 g. Hb/ 100 ml. from the expected figure. During the first part of the study serial haemoglobin estimations were made on 22 healthy premature infants whose birth weights ranged between