1歳時にmajor handicapを認めなかった症例（major handicap（－）症例：31例）では，日齢0→1・1→2と有意差をもって低下し，日齢2以降はほぼ安定して推移していたのに対し，major handicapを認めた症例（major handicap（＋）症例：10例）では，前日値と有意差なく日齢9頃まで徐々に低下した後，安定して推移していた。
以上より，発達予後の良好なmajor handicap（－）症例の，急性期以降（日齢2～50）の1,075検体を対象とするのが望ましいと考え検討したところ，基準値は2.14±1.32mmol/Lという結果を得た。また，カットオフ値は，血清乳酸値≧4mmol/Lが24時間以上遷延した症例では，major handicap合併症例が有意に多かったことより，＜4mmol/Lと判断した。
これらの値は，神経学的予後予測などに有用な指標の1つになり得るものと考えられた。
Study cohort comprised 41 consequtive extremely low birth weight infants born between April 2003 and May 2004 who survived the first hospitalization. In 31 patients who did not exhibit major handicap at age 1 year, neonatal serum lactate level significantly decreased from age 1 day to age 2 days, and from age 2 days to age 3 days. The lactate level remained stable thereafter. In 10 patients with major handicap at age 1 year, neonatal serum lactate level decreased gradually, reached nadir at age 10 days, and remained stable thereafter.
Serum lactate level from 1,075 samples taken between age 3 days and 51 days of 31 patients without later major handicap measured 2.14 ± 1.32 mmol/L. We assume the value represents standard serum lactate level in extremely low birth weight infants. Prevalence of major handicap at age 1 year was significantly higher in patients whose lactate level exceeded 4.0 mmol/L for 24 hours than in the other patients. We therefore set the predictive cut-off lactate level for developmental prognosis at 4.0 mmol/L.
These values will be useful tools for neurological developmental prediction of extremely low birth weight infants.
