摘要目的:探讨入院时合并高碳酸血症对重症社区获得性肺炎（SCAP）患者临床预后的影响，并进一步探讨高碳酸血症与感染严重程度的关系。方法:回顾性分析2017年12月至2019年11月入住广东省人民医院急危重症医学部的219例SCAP患者的临床资料。根据入院1 d内动脉血二氧化碳分压（PaCO 2）将患者分为低碳酸血症组〔HO组，PaCO 2<35 mmHg（1 mmHg＝0.133 kPa）〕、正常血碳酸组（NC组，PaCO 2 35～45 mmHg）及高碳酸血症组（HC组，PaCO 2>45 mmHg）。收集患者的性别、年龄、基础疾病等基本信息，以及入院1 d内白细胞计数（WBC）、降钙素原（PCT）、C-反应蛋白（CRP）、白细胞介素-6（IL-6）、动脉血pH值和血乳酸（Lac）水平，计算氧合指数（PaO 2/FiO 2）、肺炎严重指数（PSI）评分和急性生理学与慢性健康状况评分Ⅱ（APACHEⅡ）；观察入院1、3、5 d各项临床指标的变化趋势；比较各组有创机械通气（IMV）比例、住院时间及28 d病死率的差异；采用Kaplan-Meier生存曲线分析各组患者28 d累积存活率；采用多因素Logistic回归分析筛选SCAP患者需要IMV和28 d死亡的危险因素。 结果:与HO组（68例）及NC组（72例）比较，HC组（79例）患者入院1 d即具有更高的慢性阻塞性肺疾病（COPD）基础疾病比例和PSI评分，以及更低的PCT、CRP、IL-6和pH值。与HO组及NC组相比，HC组患者入院3 d和5 d时WBC、PCT、CRP、IL-6、PaO 2/FiO 2及Lac水平较入院1 d的改善幅度更小，且HC组入院5 d时WBC、PCT、CRP、IL-6和Lac水平均明显高于同期HO组和NC组〔WBC（×10 9/L）：18.33±1.44比10.89±2.37、11.15±1.74，PCT（μg/L）：5.04±1.18比3.46±0.87、3.58±0.83，CRP（mg/L）：78.43±7.17比54.24±4.97、57.93±5.39，IL-6（ng/L）：75.35±11.92比60.11±10.27、57.88±12.34，Lac（mmol/L）：4.36±1.24比0.78±0.39、0.86±0.64，均 P<0.01〕，而PaO 2/FiO 2则明显低于同期HO组和NC组（mmHg：171.31±6.73比226.68±7.36、225.93±6.92，均 P<0.01）。与HO组及NC组比较，HC组患者具有更高的IMV比例（29.1%比22.1%、22.2%，均 P<0.01）及28 d病死率（26.6%比13.2%、13.9%，均 P<0.01）；即使各组排除COPD患者后，HC组IMV比例及28 d病死率仍明显高于HO组和NC组。Kaplan-Meier生存分析提示，与HO组和NC组比较，HC组患者具有更高的28 d累积存活率（Log-Rank检验：χ 12＝4.976， P1＝0.026；χ 22＝4.629， P2＝0.031）。多因素Logistic回归分析结果显示，入院1 d内IL-6、PSI评分、高碳酸血症和入院5 d时PCT为SCAP患者需要IMV及28 d死亡的独立危险因素〔优势比（ OR）分别为0.325、1.229、1.396、1.313，均 P<0.01〕；即使排除COPD患者后，以上结果并未改变。 结论:入院时合并高碳酸血症与SCAP患者IMV比例和28 d病死率增加相关，这可能与其早期抑制机体炎症反应导致感染增加有关。

abstractsObjective:To investigate the effect of hypercapnia at admission on the clinical prognosis and the severity of infection in patients with severe community-acquired pneumonia (SCAP).Methods:The clinical data of 219 SCAP patients admitted to the department of emergency & critical care medicine of Guangdong Provincial People's Hospital from December 2017 to November 2019 were retrospectively analyzed. Based on the partial pressure of arterial carbon dioxide (PaCO 2) within 1 day after admission, the patients were divided into hypocapnia group [HO group, PaCO 2 < 35 mmHg (1 mmHg = 0.133 kPa)], normal carbonation group (NC group, PaCO 2 35-45 mmHg) and hypercapnia group (HC group, PaCO 2 > 45 mmHg). The clinical parameters of patients, such as gender, age, underlying diseases, white blood cell (WBC), procalcitonin (PCT), C-reactive protein (CRP), interleukin-6 (IL-6), pH value and lactate (Lac) within 1 day after admission were reviewed. The oxygenation index (PaO 2/FiO 2), pneumonia severity index (PSI) score and acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) score were evaluated. The change tendencies of each index on day 1, day 3, and day 5 after admission were observed subsequently. Meanwhile, the rate of invasive mechanical ventilation (IMV), length of hospital stays and 28-day mortality among three groups were compared. Kaplan-Meier survival analysis was performed to assess the 28-day cumulative survival rate of patients with SCAP among three groups. Multivariate Logistic regression analysis was used to screen the risk factors of IMV and 28-day death in patients with SCAP. Results:Compared with the HO group ( n = 68) and NC group ( n = 72), the HC group ( n = 79) had higher proportion of preexisting comorbid chronic obstructive pulmonary disease (COPD) and PSI score, lower PCT, CRP, IL-6, and pH values. Compared with the HO group and NC group, there were smaller improvement trends on the levels of WBC, PCT, CRP, IL-6, PaO 2/FiO 2 and Lac at day 3 and day 5 as compared with day 1 in the HC group. On the 5th day after admission, the levels of WBC, PCT, CRP, IL-6, and Lac in the HC group were significantly higher than those in the HO group and NC group [WBC (×10 9/L): 18.33±1.44 vs. 10.89±2.37, 11.15±1.74; PCT (μg/L): 5.04±1.18 vs. 3.46±0.87, 3.58±0.83; CRP (mg/L): 78.43±7.17 vs. 54.24±4.97, 57.93±5.39; IL-6 (ng/L): 75.35±11.92 vs. 60.11±10.27, 57.88±12.34; Lac (mmol/L): 4.36±1.24 vs. 0.78±0.39, 0.86±0.64; all P < 0.01], and the lowest in PaO 2/FiO 2 was found in the HC group as compared with the HO and NC groups (mmHg: 171.31±6.73 vs. 226.68±7.36, 225.93±6.92, both P < 0.01). Compared with the HO group and NC group, the HC group had highest proportion of IMV (29.1% vs. 22.1%, 22.2%, both P < 0.01) and 28-day mortality (26.6% vs. 13.2%, 13.9%, both P < 0.01). Even when the patients with COPD were excluded from the analysis, the differences persisted among the groups. Kaplan-Meier survival analysis suggested that HC group had a higher 28-day cumulative survival rate as compared with the HO and NC groups (Log-Rank test: χ 12 = 4.976, P1 = 0.026; χ 22 = 4.629, P2 = 0.031). Multivariate Logistic regression analysis showed that IL-6, PSI score and hypercapnia within 1 day and PCT on the 5th day after admission were the independent risk factors of requiring IMV and 28-day death in patients with SCAP [odds ratio ( OR) were 0.325, 1.229, 1.396, 1.313, respectively, all P < 0.01]. Even when patients with COPD were excluded from the analysis, the above results had not been changed. Conclusion:Hypercapnia at admission was associated with higher proportion of IMV and 28-day mortality in patients with SCAP, which may be related to its early suppression of inflammation and then increment of infection.