Nitrogen balance after injuries.

An increased excretion of nitrogen after injuries in experimental animals and in man was described by Cuthbertson (1930). In a series of papers he and his colleagues discussed and explored almost all the facets of this phenomenon which have since been studied (see, e.g., Cuthbertson, 1929, 1930, 1936, 1942; Cuthbertson & Tompsett, 1935 ; Cuthbertson, McGirr & Robertson, 1939). He investigated the timing and extent of the nitrogen loss, its relation to different severities of injury, to immobilization, fever and nutrition, the associated changes of plasma proteins and of potassium, sulphur and phosphate metabolism, the source of nitrogen in the body, its partition in the urine and the possible role of breakdown products, hormones or nervous action in initiating and sustaining the response. Such disturbances in recent clinical injuries are intrinsically more complex than those of standardized experimental trauma, and are more difficult to study in an adequately controlled way. There is no possibility of an initial stabilizing period, and the previous nutritional status cannot be known with precision. In the more severe injuries, therapy must necessarily be varied to meet individual requirements ; nutrition is only one of these, and must be changed to permit other procedures. Nevertheless, some observations are possible in these cases, commonly on a 'natural history' rather than an experimental basis. Helpful parallels are also available from 'cold' operation cases, where the deliberate trauma of surgery is substituted for accidental injury. But the circumstances, nature and timing of injury and corrective procedures are sufficiently different to make one cautious in accepting operation as a very close analogy to accidental trauma.