Metabolic effects of i.v. propacetamol, metamizol or external cooling in critically ill febrile sedated patients.

We have measured the metabolic response to sequential administration of propacetamol, metamizol and/or external cooling in 20 febrile patients under sedation and analgesia and during mechanical ventilation. There was no change in temperature (T degree) after propacetamol therapy, whereas after metamizol only a small decrease was noted (from 38.9 (SEM 0.2) to 38.5 (0.3) degrees C; P = 0.02). External cooling produced a significant decrease in T degree (39.1 (0.2) to 37.1 (0.2) degrees C; P < 0.0001) accompanied by a decrease in energy expenditure (EE) (2034 (73) to 1791 (88) kcal day-1; P < 0.004). Heart rate and minute ventilation decreased significantly in parallel. There were no other changes in haemodynamics or pulmonary gas exchanges. We conclude that propacetamol and metamizol did not produce a clinically significant decrease in T degree in febrile ICU patients whereas external cooling decreased both T degree and EE. The parallel decrease in body temperature and EE seemed to be related to opioid administration or sedation, or both.