Apoptotic lymphocytes induced by surgical trauma in dogs

An investigation was made of the population and function of lymphocytes in canine peripheral blood, in animals with or without laparotomy under inhalation anesthesia.

Fourteen healthy beagles were allocated to two experimental groups: laparotomy (group A) and without laparotomy (group B). Induction of anesthesia in both groups was carried out with an intravenous injection of thiopentone, and was maintained by isoflurane inhalation. Ten blood samples, consisting of 10 ml of venous blood withdrawn by venipuncture into syringes containing 200 units of preservative-free heparin, were taken, from before anesthesia to the 28th postoperative day. The blood samples were collected, and the number of lymphocytes, the lymphocyte subpopulations, the proportion of apoptotic lymphocytes, and plasma cortisol level were measured, and the blastoid transformation of lymphocytes was observed.

Lymphopenia was observed in both groups after anesthesia. Flow cytometry indicated a greater reduction in the proportion of T lymphocytes than of B lymphocytes. Blast transformation was also depressed in both groups. Progression of apoptosis after anesthesia was demonstrated in both groups, with a higher percentage of apoptotic cells being observed in group A at 12 h after anesthesia (28.5 +/- 3.2% by TUNEL assay). Plasma levels of cortisol were elevated to a greater extent in group A at the end of anesthesia (10.3 +/- 0.8 microg/dl) than in group B (7.8 +/- 1.9 microg/dl).

These results indicate that surgical trauma concomitant with anesthesia could impair immunocompetence by reducing the number and function of lymphocytes.