Abstract
A pre-term one-mo-old neonate developed laryngospasm and overt tetany during 10% Intralipid-heparin infusion. Serum total Ca was 5.0-6.0 mg%. This observation led to the hypothesis that Ca might be complexed by elevations of free fatty acids (FFA), lowering serum iCa and possibly serum total Ca. Ca and Mg form soaps with FFA that are generally water insoluble. Hydrolysis of intralipid produces FFA's, predominantly C 18: linoleic, linolenic and oleic acid; marked elevations (2.0-7.0 mM) are reported during intravenous fat infusions, especially in SGA and pre-term infants. FFA effects on serum iCa were examined in vitro from umbilical cord(6), infant(1) and adult(3) blood samples. To aliquots of serum increasing concentrations of palmitic (C16), oleic (C18) or butyric acids (C4), from 0-10 mM were added. Sample pH was unchanged; iCa determinations (Orion SS-20) were made under 5% CO2 and in room air. The slope of the change in iCa/mM FFA by regression analysis for oleic acid was 0.166± .018 (X̄±SEM), palmitic acid was 0.11±.006 and no change for butyric acid. Oleic acid reduced iCa significantly greater than palmitic acid (t test p<.02). These findings represent a 60% drop in serum iCa when FFA are increased by 10 mM oleic acid. Precipitates are seen when FFA exceeds 5 mM. Presumably iCa is complexed by FFA's and forms insoluble Ca soaps at higher concentrations. Since many infants in intensive care nurseries are simultaneously at risk for both high FFA and low iCa the use of intralipid may expose them to an added risk for tetany.
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Whitsett, J., Tsang, R. TETANY INDUCED DURING INTRALIPID INFUSION-ELEVATED FREE FATTY ACID EFFECTS ON SERUM IONIZED Ca (iCa) IN VITRO. Pediatr Res 11, 451 (1977). https://doi.org/10.1203/00006450-197704000-00489
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DOI: https://doi.org/10.1203/00006450-197704000-00489