The Annals of Thoracic Surgery, Vol 22, 44-49, Copyright © 1976 by The Society of Thoracic Surgeons
Urinary osmolal changes in renal dysfunction following open-heart operations
T Heimann, S Brau, H Sakurai and EC Peirce 2d
Forty consecutive patients who underwent open-heart procedures using a
hyperosmolar perfusion prime were studied to determine the significance of
free-water clearance and urinary osmolality early after bypass in
predicting the likelihood of postoperative renal dysfunction, defined as a
blood urea nitrogen (BUN) level over 50 mg/100 ml. Urinary osmolality
increased in all patients during the first 18 hours after bypass, but the
increase was substantially less for those who subsequently developed renal
dysfunction. Free-water clearance, which was significantly less negative in
the patients with renal dysfunction by 2 hours after bypass and remained so
throughout the 18 hours of this study, served as an early postoperative
indicator of impaired renal function in the patients who eventually
developed BUN elevation. Moreover, it was more sensitive as an index of
renal dysfunction than was osmolality alone. Early recognition of renal
impairment is important, as it may prevent dangerous fluid overloading and
allow for corrective measures to be undertaken before frank renal failure
develops.
