Nitrogen sparing and the catabolic hormones in patients nursed at an elevated ambient temperature following major surgery.

Fasted patients managed at an elevated ambient temperature following major surgery have reduced nitrogen excretion and body protein catabolism. To investigate the mechanism behind this three 24 h urine collections were made in 16 patients nursed for 48 h following aortobifemoral surgery on a Clinitron fluidized bed at 32 degrees C and analysed for total urinary nitrogen, cortisol and catecholamine excretion. Results were compared with a similar group of patients nursed throughout on a standard ITU bed at 22 degrees C. Patients managed at the elevated ambient temperature showed a significant reduction in the cumulative total urinary nitrogen (20.73 g +/- 6.42 v 28.95 g +/- 6.44; mean +/- S.D.; p less than 0.002) and cortisol excretion (1238 microg +/- 436 v 2197 microg +/- 844; mean +/- S.D.; p less than 0.001). Catecholamine excretion was also reduced but failed to achieve significance. There were significant correlations between cumulative total nitrogen excretion and both cortisol (r = +0.414; p = 0.02; n = 32) and noradrenaline (r = +0.369; p = 0.05; n = 32). These results confirm that the beneficial effect of an elevated ambient temperature on postoperative protein metabolism is brought about through a reduction in metabolic stress.