Urine output following severe burns

A difference of opinion exists concerning the usefulness of hourly urine volume as an index of effective resuscitation following burns. An investigation is described in which the volume and osmolality of the hourly urine output of severely burned patients was measured. The determinants of urine output in normal and injured patients are described and it is emphasized that volume is only one parameter of urine output. A clear distinction is made between oliguria and antidiuresis, and the significance of free osmolal output as an index of renal performance is explained.It is pointed out that the nature of the infusion fluid, the methods of assessing effective resuscitation, and the nature of the urine output are closely interrelated in any one scheme of resuscitation. From this it follows that a urine volume judged to indicate adequate resuscitation in one scheme may have a different significance in another. The view is expressed that if effective resuscitation means adequate blood flow to all tissues, the kidney should not be made an exception. Adequate renal perfusion is proved only when the urine contains a free osmolal output sufficient to permit maintenance of normal body osmolal balance in the absence of gross changes in solute-free water intake. It is suggested that urine output (volume, osmolality and free osmolal output) is a useful index of the effectiveness of resuscitation since it provides a reliable indication of renal perfusion except when renal function itself is impaired.For patients resuscitated with plasma, the range in which an ‘adequate’ urine output can be expected to lie, is given, and the possible affects of other fluids on the urine output are discussed. It is stressed that when renal function is impaired, consideration of the urine output is a more useful prognostic aid than is a study of the blood urea levels.