Baldesi Olivier, Michel Fabrice, Guervilly Christophe, Embriaco Nathalie, Granfond Aliocha, La Scola Bernard, Portugal Henri, Papazian Laurent
Medical Intensive Care Unit of the Hôpital Sainte-Marguerite, 13009 Marseille, France.
Intensive Care Med. 2009 Jul;35(7):1210-5. doi: 10.1007/s00134-009-1417-4. Epub 2009 Feb 3.
This study was designed to determine if bronchoalveolar lavage (BAL) quantitative culture results can be used confidently for the diagnosis of bacterial ventilator-associated pneumonia (VAP) without taking dilution into account.
Prospective observational cohort study.
A 12-bed medical ICU in a teaching hospital.
A total of 241 BAL (three 50-mL aliquots) were performed in 127 patients presenting a suspicion of VAP.
All consecutive adults who were ventilated more than 48 h were included if VAP was clinically suspected. A dilution factor, k, was developed according to the formula: dilution factor k = concentration of urea in plasma/concentration of urea in lavage fluid recovered. Using this dilution factor, the quantitative bacterial counts were interpreted accordingly with a corrected positive threshold at 10(5) colony forming unit (CFU) mL(-1).
Eighty-nine BAL with at least one micro-organism > or = 10(4) CFU mL(-1) were identified (37%). In 176 BAL (73%), k ranged from 10 to 100. Median k was 24.4 (9.7-40.2) in VAP group and 24.6 (13.1-57.8) in patients without pneumonia (NS). Among the 25 BAL with micro-organism counts of 10(4) CFU mL(-1), 3 had a dilution factor lower than 10, resulting in corrected counts below the threshold of 10(5) CFU mL(-1). Two out of 15 patients with micro-organism counts of 10(3) CFU mL(-1) had corrected micro-organism counts of 10(5) CFU mL(-1). Finally, only five BAL (2.1%) were misclassified when the dilution correction factor was applied.
Using urea as dilution factor, we showed that BAL dilution variations did not alter the interpretation of BAL quantitative bacterial culture when administrating three aliquots of 50 mL of saline.
本研究旨在确定支气管肺泡灌洗（BAL）定量培养结果能否在不考虑稀释因素的情况下可靠地用于诊断细菌性呼吸机相关性肺炎（VAP）。
前瞻性观察性队列研究。
一家教学医院的12张床位的内科重症监护病房。
对127例疑似VAP的患者共进行了241次BAL（三份50 mL等分试样）。
如果临床怀疑有VAP，则纳入所有连续机械通气超过48小时的成年人。根据公式计算稀释因子k：稀释因子k = 血浆中尿素浓度/回收的灌洗液中尿素浓度。使用该稀释因子，将定量细菌计数相应地解释为校正后的阳性阈值为10⁵菌落形成单位（CFU）mL⁻¹。
确定了89次BAL中至少有一种微生物≥10⁴CFU mL⁻¹（37%）。在176次BAL（73%）中，k范围为10至100。VAP组的k中位数为24.4（9.7 - 40.2），无肺炎患者的k中位数为24.6（13.1 - 57.8）（无显著性差异）。在25次微生物计数为10⁴CFU mL⁻¹的BAL中，3次的稀释因子低于10，导致校正后的计数低于10⁵CFU mL⁻¹的阈值。15例微生物计数为10³CFU mL⁻¹的患者中有2例校正后的微生物计数为10⁵CFU mL⁻¹。最后，应用稀释校正因子时，只有5次BAL（2.1%）被错误分类。
以尿素作为稀释因子，我们发现当给予三份50 mL盐水进行灌洗时，BAL稀释变化不会改变BAL定量细菌培养的解读。
