Mitochondrial perturbations and oxidant stress in lymphocytes from patients undergoing surgery and general anesthesia

Background: Previous studies have shown that a profound suppression of immu ne function transiently occurs in patients who undergo surgery under genera l anesthesia. The decline in the absolute counts of peripheral blood lympho cytes constitutes a major factor accounting for this immune defect, and rec ent evidence indicates that apoptosis plays a crucial role in determining p ostsurgical lymphocytopenia. Hypothesis: An altered oxidation-reduction status of mitochondria may contr ibute through apoptosis to the loss of lymphocytes following surgical traum a and general anesthesia. Design: We studied 16 patients with American Society of Anesthesiologists' physical status I or II who underwent elective surgery under general anesth esia. The data were collected prospectively. Setting: University hospital. Main Outcome Measures: Samples of peripheral blood were drawn on the day be fore surgery and at 24 and 96 hours after the operation. Following lymphocy te isolation, the mitochondrial transmembrane potential was assessed by flo w cytometry using 3,3'-dihexylocarbocyanine iodide, and stains with hydroet hidine and 2'7'-dichlorofluorescein diacetate were used to determine the ge neration of reactive oxygen species. The labeling of lymphocytes with monob romobimane was used to assess the presence of reduced glutathione. Results: At 24 hours after surgery, we detected a significantly elevated fr equency of peripheral blood lymphocytes (P=.002), which incorporated low le vels of 3,3'-dihexylocarbo-cyanine iodide, compared with the preoperative p eriod. At this same time point, the frequency of lymphocytes with the hydro ethidine- and 2'-7'-dichlorofluorescein diacetate-positive phenotype was el evated compared with baseline levels. Conversely, at 24 hours after surgery , the frequency of cells that stained positive for glutathione was strongly decreased compared with preoperative values. Overall measurements returned to the baseline levels at 96 hours after surgery. Conclusion: The strict association we observed between the overproduction o f reactive oxygen species and the disruption of the mitochondrial transmemb rane potential supports the view that alterations in mitochondrial energy m etabolism, paralleled by the presence of a pro-oxidant oxidation-reduction status, could be involved in the accelerated apoptotic loss of lymphocytes following surgical trauma and general anesthesia.