[Early hypophosphataemia in at risk newborns. Frequency and magnitude].

OBJECTIVE To determine the frequency and magnitude of neonatal hypophosphataemia (<4mg/dL) in a neonatal Intensive Care Unit and to describe risk groups. PATIENTS AND METHODS Retrospective study of hospitalised newborns over a 44 month period (phase 1). Retrospective study of <1,500g/<32 weeks of gestation newborns over a 6 month period (phase 2). Prospective study of <1,500g or 1,550-2,000g, and intrauterine growth restriction (IUGR) newborns. Measurements were made on the 1st, 3rd, 7th, and 14th days of life (phase 3). RESULTS Phase 1: 34 (2.4%) of 1,394 patients had a diagnosis of hypophosphataemia, 76% of them ≤32 weeks of gestation and <1500 grams, and 24% >32 weeks with weight<P10. Phase 2: 12 (16.4%) of 73 patients had a diagnosis of hypophosphataemia, with <2mg/dL in 5 (6.8%). Eight (75%) of those with hypophosphataemia had IUGR, and 4 (25%) weighed <1,000g. Five cases had associated hypokalaemia, and three hypercalcaemia. Phase 3: 9 (45%) of 20 patients had hypophosphataemia, all of them <1,000g or<1,200g and weight percentile <10. Thirty-three percent of samples on days 1, 3, and 7 showed hypophosphataemia, four of them <2mg/dL. There was mild hypokalaemia in 5 (55%), and mild hypercalcaemia in 2 (22%) cases. Hypophosphataemia was associated with lower enteral nutrition and higher parenteral amino acid intake in the early days of life. CONCLUSIONS Hypophosphataemia is common, and can be severe, in the first week of life in premature infants <1,000 grams, and newborns<1,200g with foetal malnutrition and receiving amino acids in early parenteral nutrition.