日本新生児成育医学会雑誌　第29巻　第1号　85～90頁（2017年）

日本新生児成育医学会雑誌　29(1)：85-90；2017　

受付日：平成26．10．29

受理日：平成28．07．22

早産児・新生児における生後1週間の全血イオン化マグネシウムの経時的変化

Changes in Whole Blood Ionized Magnesium Levels During the First Week of Life in Preterm and Term Infants

＊1聖マリアンナ医科大学　新生児科, ＊2現阪南中央病院　小児科

＊1Department of Pediatrics, St. Marianna University School of Medicine, ＊2Department of Pediatrics, Hannan Chuo Hospital

吉馴亮子＊1＊2・堀内　勁＊1・正木　宏＊1・伊東祐順＊1・攪上詩織＊ 1・山本　仁＊1

Ryoko YOSHINARE＊1＊2，Takeshi HORIUCHI＊1，Hiroshi MASAKI＊1，Yujun ITO＊1，Shiori KAKUAGE＊1，Hitoshi YAMAMOTO＊1

Key Words：ionized magnesium，preterm infant，term infant，the first week of life，magnesium level

　イオン化マグネシウム（iMg）はさまざまな生理活性を有する重要な陽イオンであるが，新生児期のiMg動態に関する報告は少ない。今回，生後早期のiMgの推移を明らかにする目的で検討を行った。対象は2009年4月～2012年12月の間に当院NICUおよび新生児室に入院し，分娩前に硫酸マグネシウム投与を受けていない母体から出生した早産児および正期産児130例。対象の在胎週数は中央値36.6週（25.4～ 41.4），出生体重2,318g（582～ 4,158）。生後1週間の平均iMg 値は0.56±0.08（Mean±SD）mmol/Lであった。経時的なiMg値は生後2 時間以内で0.54±0.07mmol/L，日齢1に0.51±0.07mmol/L，以後漸増し，日齢7に0.64±0.07mmol/Lとなった。在胎週数別の生後1週間での平均iMg値は在胎24～27週で0.63±0.12mmol/L，在胎28～33週で0.59±0.08mmol/L，在胎34～36週で0.57±0.06 mmol/L，在胎37週以上で0.52±0.08mmol/Lであった。生後1週間のiMg 値の変化はどの在胎週数でも日齢1に最低となり以後緩やかに上昇したが，早産児においてはその変動幅が有意に大きかった。このような新生児期におけるiMgの経時的変化を知ることは，新生児医療において有用である。

　Ionized magnesium（ iMg） is an important cation that functions as an activator of numerous enzymatic reactions. However, magnesium （Mg） homeostasis in preterm and term infants remains unclear. The aim of this study was to observe changes in iMg levels during the first week of life in preterm and term infants. One hundred and thirty infants whose mothers had not received antenatal magnesium sulfate were enrolled in this study between April, 2009 and December, 2012. iMg levels were determined using routine blood gas analysis during the first week of life. The median gestational age and birth weight were 36.6 weeks（ range, 25.4 - 41.4） and 2,318g（ range, 582 - 4,158）, respectively. The mean level of iMg was 0.56±0.08 mmol/L during the first week of life. Within 2 hours after birth the mean level of iMg reached 0.54± 0.07mmol/L. On the first day of life, the lowest mean level of iMg was observed. iMg levels increased gradually between the second and seventh day of life, reaching 0.64±0.07mmol/L on the seventh day. The mean levels of iMg for infants born at 24-27, 28-33, 34-36, and ≧37 gestational weeks were 0.63±0.12, 0.59±0.08, 0.57±0.06, and 0.52±0.08mmol/L, respectively. iMg levels in all groups of infants were at the lowest on the first day of life and gradually increased thereafter. Changes in iMg levels were greater in preterm infants than in term infants, and physicians should be aware of these changes in iMg levels during the neonatal period for neonatal care.