In the eye of the beholder: how gastric pH measured by pH sensitive litmus paper/stick compares with the gold standard.

Critically ill babies, especially if preterm and requiring neonatal intensive care, are at risk of oesophageal and gastric lesions which may result in acute gastric bleeding. The pathophysiology of these stress-induced lesions is not always clear, but one of the influencing factors is a low gastric pH. Maintaining the gastric pH above 4 is recommended to minimise morbidity from such lesions. The aim of this study was to compare pH sensitive litmus paper/stick measurements in this population against the gold standard, intragastric pH readings. Gastric juice was collected four hourly and tested with Panpeha(R) multicolour sensitive litmus paper. This result was compared with simultaneous pH probe/meter measurements.The study comprised of 62 babies, ranging in gestation from 24 to 41 weeks (median=30; mean=31; SD=4.331) and a birth weight range from 540-3655 grams (median=1391; mean=1641; SD=806); 261 paired readings were analysed. The measurements of gastric pH obtained by pH sensitive litmus paper were consistently 0.5pH units below the measurements obtained by the 'gold standard', an intragastric probe. If a gastric pH<4 was to be taken as a treatment criterion, 25% of the infants would have received inappropriate treatment based on the results of pH sensitive litmus paper readings. In conclusion, this technique for cotside estimation of gastric pH is poor. This has implications when using measurements from pH sensitive indicator strips to initiate or monitor treatments aimed at preventing the development of neonatal stress-induced gastric ulcers or to assess that feeding tubes are correctly positioned in the stomach. [ABSTRACT FROM AUTHOR]