脑脊液乳酸对颅脑手术后血性脑脊液患者细菌性脑膜炎的诊断价值

Predictive value of cerebrospinal fluid lactate for the diagnosis of bacterial meningitis in patients post- neurosurgical operation with blood-contaminated cerebrospinal fluid

目的探讨脑脊液乳酸对颅脑手术后血性脑脊液患者细菌性脑膜炎的诊断价值。方法采用前瞻性观察性研究方法，选择2015年10月至2016年12月中山大学附属第一医院神经外科重症加强治疗病房（NSICU）收治的101例颅脑手术后怀疑存在神经外科术后细菌性脑膜炎（PNBM）的患者。根据脑脊液红细胞定性结果分为血性脑脊液和非血性脑脊液两组；按照2008年美国疾病控制预防中心／国家健康照护安全网络（CDC／NHSN）的PNBM诊断标准分为PNBM组和非PNBM组。比较各组患者脑脊液生化指标的差异，绘制受试者工作特征曲线（ROC），明确脑脊液乳酸水平对颅脑手术后血性脑脊液患者细菌性脑膜炎的诊断效力。结果101例怀疑PNBM患者最终均纳入分析；77例为血性脑脊液，其中39例诊断为PNBM（占50．6％）；24例为非血性脑脊液，12例诊断为PNBM（占50．0％）。①在非PNBM组，血性脑脊液乳酸水平较非血性脑脊液明显升高（mmol／L：3．5±1．3比2．3±1．1，P〈0．01）；在PNBM组，血性与非血性脑脊液乳酸水平差异无统计学意义（mmol／L：6．8±2．1比6．9±2．5，P〉0．05）。②PNBM组血性和非血性脑脊液白细胞计数（WBC）、蛋白、乳酸水平均较非PNBM组明显升高[WBC（×10^6／L）：血性脑脊液为660．0（67．5，1105．0）比41．0（15．0，142．5），非血性脑脊液为168．0（86．5，269．5）比34．5（7．0，83．5）；蛋白（mg／L）：血性脑脊液为4757．8（2995．2，10219．8）比1292．8（924．2，1936．2），非血性脑脊液为39247．3（14900．6，62552．2）比1441．6（977．3，2963．9）；乳酸（mmol/L）：血性脑脊液为6．8±2．1比3．5±1．3，非血性脑脊液为6．9±2．5比2．3±1．1，均P〈0．05]，而糖含量、脑脊液糖／血糖比值均较非PNBM组明显下降[糖（mmol／L）：血性脑脊液为2．5±1．2比4．4±1．6，非血性脑脊液为1．9±1．4比3．4±0．9；脑脊液糖／血糖比值：血性脑脊液为0．28±0．15比0．46±0．16，非血性脑脊液为0．24±0．16比0．45±0．11，均P〈0．01]。③ROC曲线分析结果显示：无论脑脊液是血性还是非血性，脑脊液中乳酸水平对PNBM均具有良好的诊断效力，ROC曲线下面积（AUC）分别为0．91和0．97。当非血性脑脊液乳酸诊断阈值为3．35mmol／L时，敏感度为100％，特异度为91．7％。当血性脑脊液乳酸诊断阈值为4．15mmol／L时，敏感度为92．3％，特异度为71．1％；联合脑脊液糖含量可进一步提高诊断特异性（AUC=0．96，敏感度为97．4％，特异度为84．2％）。结论有血性脑脊液的PNBM患者，其脑脊液中乳酸水平较非血性脑脊液患者明显升高；血性脑脊液乳酸水平对PNBM仍具有良好的诊断效力．联合脑脊液糖含量可进一步提高诊断特异性。

Objective To evaluate the diagnostic value of cerebrospinal lactate for the diagnosis of bacterial meningitis in patients post-neurosurgical operation （PNBM） with blood-contaminated cerebrospinal fluid （CSF）. Methods A prospective observational study was conducted. 101 patients underwent neurosurgical operation and clinically suspected PNBM admitted to neurosurgical intensive care unit （NSICU） of the First Affiliated Hospital of Sun Yat-sen University from October 2015 to December 2016 were enrolled. Based on red blood cell quantitative test in CSF, the patients were divided into blood-contaminated and non blood-contaminated CSF groups. According to the PNBM diagnostic criteria of 2008 Centers for Disease Control and Prevention/National Heahhcare Safety Network （CDC/NHSN）, all patients were divided into PNBM group and non-PNBM group. The biochemical indexes levels in CSF were compared among the groups. Receiver operating characteristic （ROC） curve analysis was used to evaluate the diagnostic power of CSF lactate for PNBM in blood-contaminated patients. Results A total of 101 suspected PNBM patients were enrolled. In 77 blood-contaminated CSF patients, 39 patients were diagnosed as PNBM （account for 50.6%）; in 24 non-blood-contaminated patients, 12 patients were diagnosed as PNBM （account for 50.0%）. （1） In non-PNBM patients, the lactate level in blood-contaminated CSF was significantly higher than that of non-blood-contaminated CSF （mmol/L： 3.5 ± 1.3 vs. 2.3 ± 1.1, P 〈 0.01）. In PNBM patients, there was no significant difference in lactate level between blood-contaminated CSF and non blood-contaminated CSF （mmol/L： 6.8±2.1 vs. 6.9 ± 2.5, P 〉 0.05）. （2） In both blood-contaminated and non blood-contaminated CSF, white blood cell （WBC）, protein and lactate levels in PNBM group were significantly higher than those in non-PNBM group [WBC （ × 10^6/L）： 660.0 （67.5, 1 105.0） vs. 41.0 （15.0, 142.5） in blood-contaminated CSF, 168.0 （86.5, 269.5） vs. 34.5 （7.0, 83.5） in non-blood-contaminated CSF; protein （rag/L）： 4757.8 （2995.2, 10219.8） vs. 1292.8 （924.2, 1936.2） in blood-contaminated CSF, 39 247.3 （14900.6, 62552.2） vs. 1 441.6 （977.3, 2963.9） in non blood-contaminated CSF; lactate （mmol/L）： 6.8 ± 2.1 vs. 3.5 ± 1.3 in blood-contaminated CSF, 6.9 ± 2.5 vs. 2.3 ± 1.1 in non blood-contaminated CSF, all P 〈 0.05], and glucose and CSF glucose/blood glucose ratio in PNBM group were significantly lower than those in non-PNBM group [glucose （mmol/L）： 2.5 ± 1.2 vs. 4.4 ± 1.6 in blood-contaminated CSF, 1.9 ± 1.4 vs. 3.4 ± 0.9 in non blood-contaminated CSF; CSF glucose/blood glucose ratio： 0.28 ± 0.15 vs. 0.46 ± 0.16 in blood-contaminated CSF, 0.24 ± 0. 16 vs. 0.45 ± 0.11 in non blood-contaminated CSF, all P 〈 0.01]. （3） It was shown by ROC curve analysis that CSF lactate level was a good diagnostic parameter for PNBM both in blood-contaminated and non blood-contaminated CSF, and the area lander ROC curve （AUC） was 0.91 and 0.97, respectively. When the cutoff value of lactate in non blood-contaminated CSF was 3.35 mmol/L, the sensitivity was 100%, and the specificity was 91.7%. When the cutoff value of lactate in blood-contaminated CSF was 4.15 mmol/L, the sensitivity was 92.3%, and the specificity was 71.1%, and the combination of CSF lactate and glucose achieved better diagnostic specificity （AUC = 0.96, sensitivity was 97.4%, specificity was 84.2%）. Conclusions Blood in CSF led to the elevation of CSF lactate as compared with that in non-blood-contaminated CSF of patients with PNBM. CSF lactate was still a good diagnostic parameter for PNBM both in blood-contaminated patients, and the combination of CSF lactate and glucose achieved better diagnostic specificity.