To investigate the effect of long-term mild hypothermia therapy on immune function and its prognostic significance in patients with acute severe brain injury.

From January 2014 to August 2015, 58 patients with severe brain injury admitted to the Intensive Care Unit, the Second Affiliated Hospital of Wenzhou Medical University were collected. They were randomly divided into either a mild hypothermia group(n=32)or a normal temperature group(n=26). Serum immunoglobulin IgA, IgM, IgG content and T cell subsets CD3⁺ , CD4⁺ , CD8⁺ , and CD4⁺ /CD8⁺ levels of both groups were detected on admission at day 1, 3, 5, and 14 after procedure. At the same time, its complications and mortality rate at day 14 were observed.

Compared with before procedure, the postoperative IgA, IgM, and IgG levels were decreased in both groups of patients after procedure. The IgG level of the normal temperature group was decreased significantly at day 14 after procedure(P=0.032); the IgM and IgG levels of the mild hypothermia group were significantly higher than those of the normal temperature group over the same period(P=0.049, P=0.046). Compared with before procedure, CD3⁺ and CD4⁺ were decreased after procedure in both groups, CD3⁺ was decreased significantly at day 3 after procedure in the normal temperature group(P=0.010), and CD4⁺ was decreased significantly at day 5(P=0.037). Compared with before procedure, CD3⁺ and CD4⁺ of the mild hypothermia group were decreased at all time points, but there were no significant differences(all P>0.05). The level of CD8⁺ was increased slightly in both groups after procedure, but compared with before procedure, there was no significant difference(all P>0.05). At day 14 after procedure, the levels of CD4⁺ /CD8⁺ were decreased significantly in the normal temperature group(P=0.002). There was no significant difference in the incidence of common complications between the 2 groups(P>0.05), and the mortality of the normal temperature group at day 14 was significantly higher than that of the mild hypothermia group(P=0.045).

Long-term mild hypothermia therapy stabilized and improved the humoral and cellular immunity in patients with severe craniocerebral injury, reduced the mortality at day 14, and did not have any serious complications.

Craniocerebral trauma; Mild hypothermia; Immunomodulation; CD4-positive T-lymphocytes; CD4-CD8 ratio