脊椎インストゥルメンテーション手術後創感染早期診断に白血球分画が有用である

Usefulness of White Blood Cell Differential for Early Diagnosis of Surgical Wound Infection after Spinal Instrumentation Surgery

　抄録：白血球分画が術後創感染早期発見に有用であるかを検討した．脊椎インストゥルメンテーション手術後2週以内に創感染を起こした群（以下INF群）6例と，INF群と年齢，性別，術式をマッチさせた群（以下CTRL群）24例を対象にした．術前，術後の白血球数（以下WBC），白血球分画を測定した．WBC，好中球％，好中球数はINF群では4日目までCTRL群と同様な推移を示した後，術後7日目より再上昇した．リンパ球％・リンパ球数は，両群とも術後1日目には10％・1,000/μl以下に下がる．術後4日目からCTRL群は徐々に正常化し3週で術前と同レベルに戻るがINF群では術後11日目まで10％・1,000/μl以下を持続した．感染例で術後4日目の早期にリンパ球％とリンパ球数が有意に低下していた．これは，免疫抑制状態を示し，易感染性を呈し，術後感染を誘発する．この，リンパ球低下の時期を早期に診断できれば，術後創感染をインストゥルメントの抜去をすることなしに早期に治療できると考える．

　We investigated the usefulness of white blood cell (WBC) differential counts for the early diagnosis of deep wound infection after spinal instrumentation surgery. Two groups of patients were examined in this study：a group of such patients with early wound infection (infection group；n=6) and a group of such patients without infection (control group；n=24). The WBC counts and WBC differential counts were recorded 1 day before surgery and on postoperative days 1, 4, 7, 11, 14, and 21. The WBC count, percent neutrophils, and neutrophil count in the infection group decreased from their peak values until day 4, but increased again on day 7. The lymphocyte count and percent lymphocytes in both groups decreased from their peak values of no more than 1,000/μl and 10％, respectively, on day 1, in the control group returned to their normal levels in postoperative week 3. In the infection group, however, they persisted at no more than 1,000/μl and 10％ until 11 days postoperatively. The mean lymphocyte count and percent lymphocytes in the infected group were significantly lower than in the control group on day 4. The lymphopenia signified immunoparalysis and could mean in an increased susceptibility to infection. If lymphopenia can be diagnosed early, wound infection can be we can treated without the need to remove spinal implants.