A more detailed knowledge of the substrate load of stored blood would enable potential metabolic disturbances to be accurately predicted when infants receive large blood transfusions. Furthermore, this information is essential for the interpretation of metabolic studies in critically ill infants.Although there is some information on the substrate content of stored blood,7 detailed quantitative data on the substrate load and the effects of storage are not available. This study was designed to measure the electrolyte, metabolite, and hormone content of stored blood in relation to duration of storage. MethodsAliquots of 10 ml were taken from each of 115 units of citrate phosphate dextrose stored blood being used for clinical transfusions. Samples were taken before the six hour expiry time at room temperature. Blood was available for transfusion from the second day after collection after the completion of virological screening for hepatitis antigens. Eighty one samples were taken from blood between two and eight days after collection, and the remainder of the samples were evenly distributed over the subsequent four weeks from collection. Glucose, lactate, pyruvate, alanine, glycerol, and 3-hydroxybutyrate concentrations were measured in perchloric acid extracts of 0*5 ml whole stored blood by the method described by Lloyd and colleagues.8 The remaining sample was centrifuged for five minutes and the separated plasma deep frozen for the subsequent batch analysis of electrolytes (routine laboratory autoanalyser (Astra or Chemispek)), total protein (Biuret method), and the hormones insulin,9 cortisol,10 and growth hormone

Combination therapy increased glucose production (compared with captopril alone), indicating hepatic insulin resistance. It cannot be assumed that combined preparations with angiotensin converting enzyme inhibitors will ameliorate adverse effects of high doses of thiazide diuretics on insulin action.

Captopril therapy in uncomplicated essential hypertension has no effect on peripheral or hepatic insulin sensitivity.

Insulin action was not related to insulin pulse frequency in essential hypertension, in contrast to the situation in normal man.

Differences in whole-body glucose uptake in hypertensive and control subjects are not likely to be related to differences in insulin-induced stimulation of muscle blood flow.