心脏骤停ROSC后昏迷者的氧疗：别太高

本期关键词：conservative oxygenation（保守性氧疗）

心脏骤停ROSC后昏迷者的氧疗目标值很重要，高氧对CA患者是不利的。2008年指南（Nolan JP, Neumar RW, Adrie C, et al. Post-cardiac arrest syndrome: epidemiology, pathophysiology, treatment, and prognostication: a scientific statement　from the International liaison Committee on ResuscitationResuscitation 2008;79:350–79）建议脑复苏期间维持SPO2在94~96%的水平，以减少神经的氧化应激损伤。

相关资料：一项基于36,307例ICU患者的回顾性研究发现，ICU住院24h内PaO2水平与院内死率亡成U型关系：PaO2维持在110~150mmHg时患者死亡率最低，当PaO2<67mmHg或>225mmHg时患者死亡率显著升高。一项纳入252例缺血性脑损伤患者的前瞻性观察研究发现，PaO2>173mmHg与颅内迟发性缺血及神经功能预后不良有关。

对于CA的脑复苏治疗，SPO2维持更低水平是否也行？澳大利亚奥斯汀医院重症科Eastwood等做了一项回顾性巢式队列研究，比较保守性氧疗（使用尽可能低的FiO2维持SpO2目标值为88-92%）与常规氧疗两组ICU住院时间及预后。结果显示虽然存活出院伴良好神经功能患者比例相似，但保守性氧疗组患者ICU住院时间显著短于常规氧疗组。

那么PaO2是如何对应的？见下图（两组各50例）

入院24h内保守性氧疗组所有血气分析的PaO2平均维持在105mmHg。常规氧疗组PaO2平均130mmHg。但表格中数据显示两组PaO2跨度是有重叠的。如果更加精确的控制PaO2是否有更好的结果呢？期待有单位开展此研究。

下表数据显示住院期间高氧事件的比例及人数在常规氧疗组明显多于保守性氧疗组

看到下面的这张线图，想到的问题是降，降，降，能不能再降一点？准，准，准，能不能再准一点？

原文网址：http://www.resuscitationjournal.com/article/S0300-9572(15)00901-6/abstract

学者评论：机械通气患者的conservative oxygenation

J Physiother. 2015 Dec 1. pii: S1836-9553(15)00125-3. doi: 10.1016/j.jphys.2015.10.005. [Epub ahead of print]

A conservative oxygenation strategy is feasible and appears to be safe compared with liberal oxygenation in mechanically ventilated patients

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Within critical care, during the first week of mechanical ventilation, the liberal use of oxygen therapy often leads to PaO₂ and SpO₂ values > 80 mmHg and 96%, respectively.1 However, liberal use of oxygen therapy following cardiac arrest is associated with increased patient harm (mortality and worse neurological outcome).2 The study by Panwar et al is an important preliminary pilot, randomised, controlled trial that demonstrates that a conservative regimen of oxygen therapy aiming for a range of SpO₂ values from 90 to 92% is both feasible and safe in predominantly medical mechanically ventilated patients. Of note, there was a two-fold increase in arterial blood gas sampling in the conservative oxygen therapy group, potentially expressing clinician concerns about the oxygenation levels. A secondary analysis of the same cohort also reported significantly reduced rates of chest radiograph-diagnosed atelectasis, and earlier weaning to spontaneous ventilation modes and first spontaneous breathing trials in the conservative oxygenation therapy group.3 Clinician bias may explain the earlier transition in ventilation mode and spontaneous breathing trials in this group.3 The optimal oxygen therapy strategy across the spectrum of critical illness requires further exploration, rather than a ‘pendulous swing’ to conservative oxygen therapy targets for all critically ill patients, with preliminary evidence of beneficial impacts of moderate levels of hyperoxia on patient outcome.4

Conservative oxygenation的相关文献

Am J Respir Crit Care Med. 2015 Sep 3. [Epub ahead of print]

Conservative Versus Liberal Oxygenation Targets for Mechanically Ventilated Patients - a Pilot Multicenter Randomized Controlled Trial.

Our study supports the feasibility of a conservative oxygenation strategy （SPO28=8~92%）in patients receiving invasive mechanical ventilation.

Higher exposure to inhaled oxygen in the first 24 hours after cardiac arrest was not associated with deterioration in gas exchange or pulmonary compliance after cardiac arrest, but was associated with decreased survival and worse neurological outcomes.

Critical Care201519:105

Published: 10 March 2015