Circulation：PaCO2紊乱与心跳骤停后患者神经功能转归不佳独立相关

　　美国一项研究表明，心搏骤停后低碳酸血症和高碳酸血症均常见，并且与神经功能转归不佳独立相关。论文4月23日在线发表于《循环》（Circulation）。

　　此项研究以年龄≥18岁、非创伤性停搏并且自主循环恢复（ROSC）后昏迷的心跳骤停患者为受试者。在ROSC后0～24小时期间分析动脉血气数据，并确认患者是否暴露于低碳酸血症和/或高碳酸血症（分别以PaCO₂ ≤30mmHg和PaCO₂ ≥50mmHg定义）。主要转归为出院时神经功能不佳（以脑功能分类≥3定义）。

　　结果显示，在193例患者中，仅伴低碳酸血症、仅伴高碳酸血症以及二者均有的患者分别为52（27%）、63（33%）和18（9%）例，无PaCO₂异常者为60例（31%）；74%的患者伴有神经功能转归不佳。对已知转归不佳预测因素进行校正之后，多变量Logistic回归显示低碳酸血症和高碳酸血症均与神经功能不佳独立相关（比值比分别为2.43和2.20）。

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Association between Post-Resuscitation Partial Pressure of Arterial Carbon Dioxide and Neurological Outcome in Patients with Post-Cardiac Arrest Syndrome
BACKGROUND
Partial pressure of arterial CO2 (PaCO2) is a regulator of cerebral blood flow after brain injury. Recent guidelines for management of cardiac arrest recommend maintaining PaCO2 40-45mmHg after successful resuscitation; however, there is paucity of data on the prevalence of PaCO2 derangements during the post-cardiac arrest period, and association with outcome.
METHODS AND RESULTS
We analyzed a prospectively compiled and maintained cardiac arrest registry at a single academic medical center. Inclusion criteria: age ≥18, non-trauma arrest, and comatose after return of spontaneous circulation (ROSC). We analyzed arterial blood gas data during 0-24 hours after ROSC and determined whether patients had exposure to hypocapnia and/or hypercapnia (defined as PaCO2 ≤30mmHg and PaCO2 ≥50mmHg, respectively, based on previous literature). The primary outcome was poor neurological function at hospital discharge, defined as Cerebral Performance Category ≥3. We used multivariable logistic regression, with multiple sensitivity analyses, adjusted for factors known to predict poor outcome, to determine if post-ROSC hypocapnia and/or hypercapnia were independent predictors of poor neurological function. Of 193 patients, 52 (27%) had hypocapnia only, 63 (33%) had hypercapnia only, 18 (9%) had both hypocapnia and hypercapnia exposure, and 60 (31%) had no exposure; 74% of patients had poor neurological outcome. Hypocapnia and hypercapnia were independently associated with poor neurological function, odds ratio 2.43 (95% CI 1.04-5.65) and 2.20 (95% CI 1.03-4.71) respectively.
CONCLUSIONS
Hypocapnia and hypercapnia were common after cardiac arrest and independently associated with poor neurological outcome. These data suggest PaCO2 derangements could be potentially harmful for post-cardiac arrest patients.