Effect of anesthesia and surgery on plasma cytokine levels

Abstract

Cytokines released in response to stress may have a profound impact on circulatory stability. There is no information on the effect of general anesthesia alone on plasma cytokine levels and little information on cytokine release following surgery. Plasma cytokine levels and hemodynamic parameters were measured during anesthesia and abdominal surgery under sterile and nonpyrogenic conditions in seven pigs anesthetized with ketamine and pentobarbital. Tumor necrosis factor (TNF) was measured by bioassay. Bioassays of low and high sensitivity were used to measure interleukin 6 (IL-6). Measurements were made sequentially during: (1) 4 hours observation with anesthesia alone; (2) 2 hours following laparotomy and traumatic intestinal manipulation (IM) sufficient to produce shock; and (3) after an intravenous bolus of 1 μg/kg endotoxin as a positive control. Arterial blood pressure decreased following IM from 91.5 ±- 5.8 to 48.6 ±- 3.2 mm Hg, (mean ±- SE, P < .05), with no further change following endotoxin. Heart rate was unchanged during the experiment, and central venous pressure decreased after endotoxin ( P < .05). There were no increases in TNF or IL-6 (using a low sensitivity assay) with anesthesia alone or following IM with shock, but both increased after endotoxin administration ( P < .05); using a high sensitivity assay, IL-6 did not change during anesthesia alone but did increase fivefold following IM with shock ( P < .05) and 50-fold following endotoxin administration ( P < .05). We conclude that in a porcine model under sterile and nonpyrogenic conditions, prolonged anesthesia does not increase plasma cytokine levels. Traumatic manipulation of the intestines sufficient to cause diffuse bowel injury and shock causes only small increases in plasma IL-6. Substantial increases in both TNF and IL-6 occur following a minimal endotoxin challenge showed an intact functional systemic response.