Ionized magnesium concentrations in critically ill children.
OBJECTIVE
To test the hypothesis that many critically ill children exhibit ionized hypomagnesemia despite having normal total magnesium (TMg) concentrations.


METHODS
A prospective, observational study with convenience sampling.


METHODS
Pediatric and cardiovascular intensive care units of a large children's hospital.


METHODS
Patients aged 1 day to 21 yrs admitted from January 1 to October 31, 1996. Patients with chronic renal failure or weight <3 kg were excluded. A group of healthy children involved in a school-based nutritional assessment study were also studied.


METHODS
None.


RESULTS
Sixty-seven patients (5.4+/-5.7 [SD] yrs) and 24 healthy children (10.84+/-0.93 yrs, p< .001) were studied. Plasma was assayed for ionized magnesium (IMg) using a blood analyzer. Forty (59%)/67 critically ill subjects had IMg concentrations <0.40 mmol/L, the lowest published normal value and the lowest value observed in our group of healthy children. Of these, 24 (60%)/40 had normal TMg concentrations. IMg was significantly (p=.00) lower in critically ill subjects than in the group of healthy children (0.37+/-0.10 mmol/L vs. 0.46+/-0.03 mmol/L). IMg did not correlate strongly with ionized calcium (r2=0.49), albumin (r2=0.09), or pH (r2=0.18).


CONCLUSIONS
Many critically ill children exhibit ionized hypomagnesemia with normal TMg concentrations. These children would not be recognized as magnesium-deficient based on routine TMg testing. Critically ill children exhibited significantly lower concentrations of IMg than a group of healthy children.
Fiser
R T
RT
Wilford Hall Medical Center, Lackland AFB, TX 78236, USA.
Torres
A
A
Butch
A W
AW
Valentine
J L
JL
D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D015984:Causality; D002648:Child; D002675:Child, Preschool; D016638:Critical Illness; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007477:Ions; D008274:Magnesium / Q000097:blood*; D008275:Magnesium Deficiency / Q000097:blood*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D012494:Sampling Studies
D007477:Ions; D008274:Magnesium