Reduction of Methylene Blue by the Blood of Young Infants

The blood of infants shows significant alterations in the first few months of life. Most pronounced, perhaps, is the drop in the number of red blood cells and in hemoglobin. Another hitherto unrecognized feature apparently characteristic of this period is the rapidity with which the blood decolorizes methylene-blue.

The method employed in this investigation was as follows: A stock solution was prepared by dissolving 200 mg. of methylene blue∗ in 40 cc. of 3% sodium citrate∗ in doubly distilled water at pH 7.4 to 8.1. After filtration 0.07 cc. of this solution was dissolved in 50 cc. of sodium citrate of the same strength, giving a final concentration of methylene blue of approximately 1:140,000. This solution was left at least 24 hours in the ice-box before use. For each test 4 samples of freshly drawn blood was added to 0.1 cc. of the methylene blue solution. The quantities of blood with youngest subjects were .02, .03, .04, and .05 cc. respectively, and a range of .03 to .06 cc. in the older ones. The contents were thoroughly admixed and kept at 15°C. for 1 hour. The tubes were then centrifuged for 2 minutes. The extent of reduction was 0 when the dilute blue color was unchanged, to 4 plus when the dye was completely reduced to that of water.

This study included the blood of 238 healthy individuals, 152 under one year of age, the remainder ranged to 40 years. The results are summarized in Table I.

The reduction of methylene blue proceeded most rapidly and completely in the large majority of observations during the first 4 months of life. After this period, the reducing power was markedly diminished and resembled the blood of the older child and adult.

Tests were also carried out periodically with the blood of 3 young rabbits. The results corresponded with the human infant except that the reducing power of the animals disappeared between 2 and 3 months of age.