Change in plasma endotoxin titres and endotoxin neutralizing activity in the perioperative period

To elucidate whether endotoxaemia detected during major surgery was a specific or non-specific reaction.

Prospective clinical study in the operating theatre and multidisciplinary intensive care unit in a university hospital. A series of plasma samples was obtained from 21 patients, including eight after cardiopulmonary bypass (CPB), until 48 hr after surgery. The endotoxin titres in these samples were compared by the two chromogenic limulus amebocyte lysate (LAL) assays; one is factor G containing and the other factor G-free, endotoxin-specific test. The endotoxin neutralizing activity of the plasma was determined by adding the endotoxin to the plasma (1,000 pg.ml-1), and by assaying how much the potency of the endotoxin to activate LAL was lost during incubation for 120 min at 37 degrees C.

Although endotoxin titres measured using the test including factor G showed a marked elevation during and after surgery, which were 3 +/- 5 (4 +/- 10), 14 +/- 13 (20 +/- 17**), 133 +/- 13* (46 +/- 29*), 89 +/- 72* (48 +/- 35*), 62 +/- 40** (37 +/- 29*), 50 +/- 54 (39 +/- 36) pg.ml-1 in patients with CPB (without CPB), mean +/- SD, at 0, 3, 6, 9, 24, and 48 hr after start of surgery (*P < 0.01, **P < 0.05 compared with 0 hr), those measured by the endotoxin-specific test did not show any changes. Plasma neutralized 95% of endotoxin potency after five minutes incubation at 37 degrees C.

Using an endotoxin-specific assay, endotoxin could not be detected in the blood stream during or after major surgery.