Background

The safety of anaesthesia has improved as a result of better control of anaesthetic depth. However, conventional monitoring does not inform on the nature of nociceptive processes during unconsciousness. A means of inferring the quality of potentially painful experiences could derive from analysis of brain activity using neuroimaging. We have evaluated the dose effects of remifentanil on brain response to noxious stimuli during deep sedation and spontaneous breathing.

Methods

Optimal data were obtained in 26 healthy subjects. Pressure stimulation that proved to be moderately painful before the experiment was applied to the thumbnail. Functional MRI was acquired in 4-min periods at low (0.5 ng ml⁻¹), medium (1 ng ml⁻¹), and high (1.5 ng ml⁻¹) target plasma concentrations of remifentanil at a stable background infusion of propofol adjusted to induce a state of light unconsciousness.

Results

At low remifentanil doses, we observed partial activation in brain areas processing sensory-discriminative and emotional-affective aspects of pain. At medium doses, relevant changes were identified in structures highly sensitive to general brain arousal, including the brainstem, cerebellum, thalamus, auditory and visual cortices, and the frontal lobe. At high doses, no significant activation was observed.

Conclusions

The response to moderately intense focal pressure in pain-related brain networks is effectively eliminated with safe remifentanil doses. However, the safety margin in deep sedation-analgesia would be narrowed in minimising not only nociceptive responses, but also arousal-related biological stress.

中文翻译：

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异丙酚深度镇静期间瑞芬太尼对脑损伤性刺激反应的影响

背景

由于更好地控制麻醉深度，麻醉的安全性得到提高。然而，传统的监测并没有告知无意识期间伤害感受过程的性质。一种推断潜在痛苦经历的质量的方法可能来自使用神经影像学分析大脑活动。我们评估了瑞芬太尼在深度镇静和自主呼吸期间对大脑对伤害性刺激反应的剂量效应。

方法

在 26 名健康受试者中获得了最佳数据。在将实验应用于缩略图之前，压力刺激被证明是中度疼痛。在稳定的异丙酚输注背景下，在 4 分钟内获得瑞芬太尼低（0.5 ng ml ^-1）、中等（1 ng ml ^-1）和高（1.5 ng ml ^-1 ）目标血浆浓度的功能 MRI诱导光无意识状态。

结果

在低剂量瑞芬太尼时，我们观察到处理疼痛的感觉-辨别和情绪-情感方面的大脑区域的部分激活。在中等剂量下，在对一般大脑唤醒高度敏感的结构中发现了相关变化，包括脑干、小脑、丘脑、听觉和视觉皮质以及额叶。在高剂量下，没有观察到明显的激活。

结论

安全剂量的瑞芬太尼可有效消除与疼痛相关的大脑网络中对中​​等强度局灶性压力的反应。然而，深度镇静镇痛的安全范围会缩小，不仅要最小化伤害性反应，还要最小化与觉醒相关的生物应激。