Raised plasma urea levels after myocardial infarction.

Plasma and urine urea and creatinine levels were measured in 50 consecutive patients admitted to a coronary care unit. Forty of the patients had had myocardial infarction; their average plasma urea level increased substantially by the third day after admission, when 50% of the patients had an "abnormally" high plasma urea level. There was no change in plasma urea levels in ten patients who had not had a myocardial infarction. Results indicate that a rise in plasma urea level is common if not universal after myocardial infarction and is caused by either a fall in the glomerular filtration rate or an increased urea production rather than a mixture of the two.