[The clinical relevance of subcutaneous-thoracic ratio in preterm newborns as a possibility for quantification of capillary leak syndrome].

BACKGROUND: Capillary leak syndrome (CLS) is associated with increased morbidity and mortality in preterm newborns (PN) with sepsis or necrotizing enterocolitis.

PATIENTS AND METHODS: In order to provide improved standards for measuring edema and for the definition of CLS, subcutaneous-thoracic ratios (S/T) were calculated from 821 anteroposterior supine chest radiographs of 119 PN with a birth weight below 1500 g. The S/T was computed by 100 % minus ratio of dividing the outer margins of the eighth rib by the total diameter of the thorax at the same position. Birth weight, gestational age, need for assisted ventilation and the position of the diaphragm did not significantly affect S/T. The S/T drifted downwards slightly with postnatal age.

RESULTS: To provide normal standards of S/T in PN, the ratio was calculated in percentiles and the higher percentiles correlated with diseases. 771 S/T were lower than 10.1 % (95th percentile), 21 were 10.1 - 12.6 % (97.5th percentile) and 20 were even higher. 3 of the 100 PN (84 %) with an S/T < 10.1 % died because of extreme immaturity. Eight patients (6.7 %) had an S/T between the 95th and the 97.5th percentile in at least one of their radiographs. Four of them had a respiratory distress syndrome and one died. Eleven PN had an S/T > 12.6 %. All of them showed a multiple organ failure and four died. When the SIT was > 15 % the edema became visible. A CLS was diagnosed in two PN with an S/T > 20 %.

CONCLUSIONS: The threshold for the capillary leak syndrome was found to be 12.6 % also in reference to the course of diseases. The S/T is a useful tool because it is simple to measure and calculate, and is available from a single frontal film. The ratio can measure objectively the edema and the CLS in PN.