[Apoptosis of circulating lymphocyte in surgical critically ill patients associated with poor outcome]

To investigate the role and mechanism of lymphocyte apoptosis in post-operative critically ill patients and to determine the effects of lymphocyte apoptosis on the outcome of post-operative critically ill patients.

Thirty-nine consecutive post-operative patients admitted to the intensive care unit (ICU) were included in the prospective study. In addition, 30 healthy blood donors were involved for comparison. Early signs of apoptosis were investigated using flow cytometric measurement of Annexin-V binding to the cell surface of peripheral lymphocytes. In patients, absolute lymphocyte counts were measured on day 1, 3 and 5. The correlations of secondary infection and ICU stay duration with lymphocyte apoptosis and lymphocyte counts were determined.

Post-operative critically ill patients exhibited higher rate of lymphocyte apoptosis than controls [(10.82+/-3.32)% vs. (2.89+/-1.17)%, P<0.01]. Meanwhile, lymphocyte counts were decreased significantly in patients compared with healthy individuals [(1.41+/-1.26) x 10(9)/L vs. (2.58+/-0.62) x 10(9)/L, P<0.01]. In patients group, rate of lymphocyte apoptosis was significantly higher in patients with secondary infection compared with those without secondary infection [(12.67+/-3.11)% vs. (9.24+/-2.63)%, P<0.01], and lymphocyte counts had no difference on day 1, while on day 3 and day 5 were decreased significantly in patients with secondary infection compared with those without secondary infection [(0.68+/-0.35) x 10(9)/L vs. (1.30+/-1.33) x 10(9)/L, (0.72+/-0.40) x 10(9)/L vs. (1.34+/-1.11) x 10(9)/L, respectively, stay duration of post-operative patients was positively correlated with rate of lymphocyte apoptosis (r=0.412, P=0.009) and negatively correlated with day 1, 3 and 5 lymphocyte counts, significantly correlated with day 1 and day 5 (r(1)=-0.333, r(5)=-0.361, both P<0.05).

Lymphocyte apoptosis is enhanced in peripheral blood of post-operative critically ill patients and leads to a profound and persistent lymphopenia associated with poor outcome such as secondary infection and delay of ICU stay duration. Further studies are required to examine whether intervention to prevent lymphocyte apoptosis might alter the patients' outcome.