The cause of the raised plasma urea of acute heart failure.

The concentrations of urea, urate, phosphate and creatinine were measured in the plasma of 30 consecutive patients admitted acutely with heart failure. On admission, 20 had a raised plasma urea, 21 had a raised plasma urate, but only 6 had a raised plasma phosphate and only 6 had a raised plasma creatinine. A further 9 of the patients developed a raised plasma urea after admission. The increase in plasma urea present on admission was greater than expected for the fall in GFR (as indicated by the increase in plasma creatinine). The results for plasma and urine taken together suggest that a major cause of the raised plasma urea was an increased urea production rather than a reduced glomerular filtration rate. There was no obvious relationship between plasma urea and clinical features, or diuretic therapy.