Demonstration of a reduction in postoperative body protein breakdown using the Clinitron fluidized bed with an ambient temperature of 32°C

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Abstract
Patients managed at an elevated ambient temperature after major surgery have a less pronounced rise in postoperative urinary nitrogen excretion. To investigate the mechanism involved, body protein breakdown was assessed, using a tracer dose of labelled amino acid, in patients following aorto-bifemoral bypass surgery nursed on either a Clinitron fluidized bed at 32°C or a hospital bed at 22°C and correlated with urinary total nitrogen excretion. Results showed a small reduction in measured body protein breakdown on the second postoperative day in patients managed on the Clinitron fluidized bed at 32°C (2·92 ± 0·91 versus 3·23 ± 0·84 g protein kg−1 day−1; mean ± s.d.), which was equivalent to the mean protein sparing (0·29 g protein kg−1 day−1) demonstrated by the significant improvement in urinary total nitrogen excretion (9·20 ± 2·0 versus 12·48 ± 3·9 g N day−1; mean ± s.d.: P < 0·05). Urinary total nitrogen excretion (N) and body protein breakdown (B) showed a weak though significant positive correlation (B = 1·25 + 13·13N; r = + 0·55 : P = 0·05), whereas no correlation existed between urinary total nitrogen excretion and the derived rate of body protein synthesis. There was also a significant decrease in postoperative stress, measured during the isotope infusion, in patients managed on the Clinitron fluidized bed at 32°C (12·3 ± 2·2 versus 16·1 ± 3·2 per cent activity incorporated into plasma proteins; mean ± s.d.: P < 0·05). These results show the beneficial effect of managing postoperative patients on a Clinitron fluidized bed at 32°C in conserving body nitrogen through a reduction in body protein breakdown, probably as a consequence of decreased postoperative stress.