Malhotra Ajai K, Riaz Omer J, Duane Therese M, Aboutanos Michel B, Goldberg Aaron E, Smalara Karen M, Borchers Christopher T, Martin Nancy R, Ivatury Rao R
Department of Surgery, Division of Trauma/Critical Care/Emergency General Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
J Trauma. 2008 Sep;65(3):580-8. doi: 10.1097/TA.0b013e3181825b9f.
Quantitative bronchoalveolar lavage (qBAL) is used for accurate diagnosis of ventilator-associated pneumonia (VAP). The current study aims at defining the incidence, outcomes and therapeutic implications of false-negative (FN) qBAL.
Ventilated trauma, surgery, and burn, patients suspected of VAP underwent bronchoscopic qBAL. VAP was defined as qBAL with >10(5) CFU/mL (threshold). To identify FN BALs, blood cultures drawn concomitant with BAL (+/-5 days of BAL) were analyzed. qBAL specimens growing <10(5) CFU/mL (subthreshold) with blood culture identifying the same organism, without any other source, were classified as FN.
Over 39 months, 246 patients underwent 365 qBALs. Ninety-one specimens had no growth and 274 specimens grew 433 organisms--100 at threshold and 333 at subthreshold strength. Sixteen percent of threshold and 11% of subthreshold organisms were associated with bacteremia. Rates of bacteremia were similar across strengths of growth. Bacteremia at all strengths of growth was more common with Staphylococcal species (methicillin sensitive and resistant) and for hospital-acquired gram-negatives. Rates of bacteremia at all strengths of growth were significantly higher after the first week of hospitalization. Bacteremia worsened outcomes in both threshold group (higher mortality, p < 0.05) and subthreshold group (longer lengths of stay, p < 0.05).
qBAL has 11% FN rate as measured by blood stream invasion. Propensity of blood stream invasion is related to species of organism (Staphylococcal species and hospital-acquired gram-negatives) and duration of hospitalization, but not to strength of growth. Isolation of these organisms in BAL, at any strength, after the first week should prompt strong consideration for antimicrobial therapy.
定量支气管肺泡灌洗（qBAL）用于准确诊断呼吸机相关性肺炎（VAP）。本研究旨在确定qBAL假阴性（FN）的发生率、结局及治疗意义。
对因创伤、手术和烧伤而接受机械通气且疑似VAP的患者进行支气管镜qBAL检查。VAP定义为qBAL培养结果>10⁵CFU/mL（阈值）。为识别FN BAL，对与BAL同时采集（BAL前后5天内）的血培养进行分析。qBAL标本培养结果<10⁵CFU/mL（低于阈值）且血培养鉴定出相同病原体且无其他感染源的情况被归类为FN。
在39个月期间，246例患者接受了365次qBAL检查。91份标本无细菌生长，274份标本培养出433种微生物——100种达到阈值，333种低于阈值。16%达到阈值的微生物和11%低于阈值的微生物与菌血症相关。不同生长强度的菌血症发生率相似。所有生长强度的菌血症在葡萄球菌属（甲氧西林敏感和耐药）及医院获得性革兰阴性菌中更常见。住院第一周后，所有生长强度的菌血症发生率均显著升高。菌血症使阈值组（死亡率更高，p<0.05）和低于阈值组（住院时间更长，p<0.05）的结局均恶化。
通过血流侵袭测量，qBAL的FN率为11%。血流侵袭倾向与病原体种类（葡萄球菌属和医院获得性革兰阴性菌）及住院时间有关，而与生长强度无关。第一周后，无论生长强度如何，在BAL中分离出这些病原体均应促使强烈考虑进行抗菌治疗。
