经皮微循环成像在早产儿

摘要

Microcirculatory imaging (MI) is used to monitor peripheral perfusion in critically ill or preterm neonates. This manuscript and video demonstrates the optimal approach for obtaining high-quality images.

摘要

Microcirculatory imaging (MI) is a relatively new research tool mainly used in the intensive care setting. MI provides a clear view of the smallest capillaries, arterioles and venules. The magnifying effect visualizes the flow pattern of erythrocytes through these vessels.

It's non-invasive character makes it suitable to apply in (preterm) neonates, even in cardiorespiratory unstable patients. In adults and children, MI is mainly performed sublingually, but this is not possible in preterm infants as these cannot cooperate and the size of the probe is problematic. In preterm infants, MI is therefore performed transcutaneously. Their thin skin makes it possible to obtain high quality images of peripheral microcirculation.

In this manuscript we will demonstrate the method of transcutaneous MI in preterm infants. We will focus on the different techniques and provide tips to optimize image quality. The highlights of software settings, safety and offline analysis are also addressed.

引言

Hemodynamic diagnostics in critically ill preterm neonates has always been difficult. Most diagnostic tools used in adults cannot be applied in these tiny preterm infants; and then there is a problem of the sensitivity of the outcome parameters. But most of all, these infants are so vulnerable, that the risks of diagnostic procedures do not outweigh the benefits. As a result, in the field of neonatology, hemodynamics has been neglected and therefore there is a lack of knowledge on this topic.

An interesting option for handling these problems might be visualizing the microcirculation. The introduction of handheld microscopes in the late 1990s made it possible to visualize the microcirculation in a non-invasive manner. Three generations of devices have been introduced: Orthogonal Polarization Spectral (OPS) imaging¹, Sidestream Dark Field (SDF) imaging², and Incident Dark Field (IDF) imaging³. They all use more or less the same technique in which green light with a specific wavelength (548nm) stroboscopic illuminates the microcirculation. The green light is absorbed by oxy- and deoxyhemoglobin and mostly reflected by the surrounding tissue. This property of green light therefore creates visible contrast. The reflected light passes a magnification lens and is projected on a camera sensor. Hereby it is possible to visualize the flowing red blood cells at a depth of approximately one millimeter of mucosal tissue or directly at solid organs.

Over the past 15 years, the microcirculation has been mainly studied in adults, especially in patients with septic shock^4-6. These observational studies found that persistent microcirculatory alterations were associated with organ failure and mortality. This observation cannot be extrapolated directly to (preterm) infants however, as in the adults the microcirculation was measured sublingually. High quality images of the sublingual microcirculation cannot be obtained in preterm infants because they are unable to cooperate. In term infants the buccal microcirculation has been the area of interest⁷. Fortunately, in preterm infants the thin skin allows transcutaneous microcirculatory imaging. This approach has been applied in neonatal studies focusing on blood transfusion⁸, therapeutic hypothermia⁹ and hypotension¹⁰.

In this manuscript we present our protocol for transcutaneous microcirculatory imaging using Incident Dark Field imaging in preterm neonates. We will focus on different strategies to acquire the highest quality images. Technical details and differences between the SDF and IDF devices can be found elsewhere¹¹.

研究方案

该协议遵循当地人类研究伦理委员会的指导方针。

1.准备

1. 安排微循环的测量，使得它不与其它方法如血液采样重合。在足月新生儿最好是喂后进行。这可以防止激动，并缓解测量。
2. 确保护士或家长出席支持，并在考试期间安慰新生儿，新生儿使用的个性化发展护理和评估方案¹²的原则。
   注:虽然测量可以由一个人来完成，这是强烈建议有第二个人协助。之一成立相机和聚焦在新生儿，而另一个工作的计算机和软件。根据我们的经验，这将导致更高质量的图像和过程的持续时间较短。
3. 如果满足新生儿允许临床情况中，放置新生儿取仰卧位。微循环成像可以在俯卧位进行，但这需要更多的技巧和耐心。
4. 确保早产儿的身体温度在适当的范围内（36.5 - 37.5摄氏度）。

2.程序

1. 安装沿培养箱的装置。确保孵化器是在合适的高度。
2. 把相机放在一次性帽子。
3. 适用的凝胶，油或盐水在探头的尖端;这将有助于平滑探头和皮肤之间的接触。
4. 将相机放在婴儿上臂的腹侧面。为防止焦点文物，确保探头垂直于皮肤。这可能需要婴儿臂的重新定位。
   注意:上臂的腹内侧边是测量皮肤微循环的主要位置。此位置有一点胎毛，因此不容易出现假象。这是最容易达到如果患者被定位在仰卧姿势。
5. 为了最大限度地减少程序的总长度，通过寻找焦点的最佳深度（图3），同时搜索具有最少伪影位置的赢得时间。
   注:聚焦深度主要取决于后天的年龄，而不是胎龄。聚焦在生命的第一个星期的平均深度是0 - 80微米。 200微米1之间- - 4个星期产后年龄的（图2）以后，由于成熟的皮肤，焦点深度迅速用80平均值增加。在长期新生儿出生重点的平均深度为80 ​​- 160微米的诞生。
6. 稳定的探头，以避免移动文物。要做到这一点，休息培养箱窗口上的弯头和新生儿旁边的手腕。另外，定位探头一起在枕头新生儿。
7. 通过让相机避免压力的文物只有与皮肤轻微的接触。压力文物可以是R在图像捕获期间ecognized如果在船后面的往复流动，或者如果大血管是非灌注而有小血管良好的流动。此外，如果流型是在整个屏幕相同，谨防压力假象。
8. 录制视频为5秒的最短时间。
9. 成功捕获后，将摄像机移动到上臂另一个地方。
   注:建议捕捉，共有5 - 3 10视频 - 5个不同的地点，因为有些文物的确认在离线分析，这意味着有问题的视频不进行分析使用。
10. 轻轻地用小纱布去除皮肤凝胶，油或盐。

3.离线分析

1. 作物的视频如果存在阻碍分析一个显著运动。进入"工具"部分，使用按钮"编辑"。选择帧间隔资格进行分析，然后点击"剪裁视频"Button。注:视频是可以接受的，如果运动是在半实地查看^13。
2. 选择裁剪视频和稳定的。转至"工具"部分，使用按钮"分析"。点击"稳定"按钮。
   注意:前自动分析可以进行所有的电影必须稳定。
3. 选择稳定的视频。转至节"分析"，然后单击"检测"按钮。确保选项"毛细血管"和"船"突出显示。
4. 检测（ 图4）后，点击"中央社"或"德靠山"按钮，一个完整的微循环的报告。该报告包括最常用的结果参数，如总血管密度（TVD），灌注血管密度（PVD）和血管灌注（PPV）的比例。
   注意:作为替代方案，视频可以导出脱机进行手动分析。此选项可以在一节"工具"中找到。硒择的选择"导出"，然后单击"AVA导出"按钮。

结果

图1和图2显示代表性的仍然是高品质的MI的视频图像。这些实施例说明在第1天（图1）和28天之间的相同婴儿皮肤厚度差产后年龄的（图2）。第1天，有一个明亮的照明，充足的专注于微血管和文物的最小的存在。在第28天是比较难以找到焦点上微容器和假象之间取得适当的平衡，由于较厚的皮肤。需要注意的是稳定，持续时间和压力假...

讨论

在这个手稿中，我们描述和展示早产新生儿经皮微循环成像的方法。这种可视化方法将有助于研究人员克服两个在研究中的最大的挑战:可重复性和时间学习新的技术劳动密集性质。这种技术可以在一种非侵入性的方式提供早产儿外围微循环的有用信息。连续测量可以帮助医生评估治疗干预的影响。微循环是其中氧运输链的最后步骤发生的区域。观察性研究已经表明微循环恶化随着时间的推移和细...

材料

Name	Company	Catalog Number	Comments
Cytocam	Braedius	http://www.braedius.com/magnoliaPublic/braedius/products.html	Other well known handheld microscopes to visualize the microcirculation are MicroScan (Microvision Medical) using SDF technique or the CytoScan (CytoMetrics) using OPS technique
Disposable Lens Cover	Glycocheck	http://www.glycocheck.com/lenscovers.php
CCTools	Braedius	http://www.braedius.com/magnoliaPublic/braedius/products.html	Another well known offline analysis programme is AVA (Microvision medical).