Bondarsky Eric, Rothman Adam, Ramesh Navitha, Love Angela, Kory Pierre, Lee Young I
Department of Medicine, NYU School of Medicine, New York, New York.
Department of Medicine, Mount Sinai Beth Israel Hospital, New York, New York.
J Clin Ultrasound. 2020 Jun;48(5):249-253. doi: 10.1002/jcu.22817. Epub 2020 Feb 4.
Inferior vena cava (IVC) diameter and variation are commonly measured in the supine position to estimate intravascular volume status of critically ill patients. Many scientific societies describe the measurement of IVC diameter in the supine position. However, critically ill patients are rarely placed supine due to concerns for aspiration risk, worsened respiratory mechanics, increases in intracranial pressure, and the time it takes to change patient position. We assessed the influence of head-of-bed (HOB) elevation on IVC measurements.
We conducted a prospective observational study of critically ill patients undergoing critical care ultrasound. With HOB at 0°, IVC maximum (IVCmax0°) and minimum (IVCmin0°) diameters were measured. Measurements were then repeated with HOB elevated to 30° and 45°. Collapsibility index (CI), defined as (IVCmax - IVCmin)/IVCmax, was calculated for each HOB elevation. Mean differences were then compared.
A convenience sample of 95 patients was studied, of whom 45% were on vasopressors and 44% were spontaneously breathing. The CI did not significantly differ between the three positions. We found a significant difference (P ≤ .0001) between IVCmax at 45° (2.09 cm) and 0° (1.96 cm), IVCmin at 45° (1.75 cm) and 0° (1.59 cm), IVCmax at 45° (2.09 cm) and 30° (1.97 cm), and IVCmin at 45° (1.75 cm) and 30° (1.61 cm).
In a population of critically ill patients undergoing goal-directed ultrasound examinations, elevating HOB to 30° did not significantly alter IVC measurements or CI. At 45°, however, IVCmax and IVCmin diameters increased significantly, albeit with no significant change in CI. Performing ultrasound measurements of the IVC with HOB elevated to 30° is unlikely to produce clinically meaningful changes.
下腔静脉（IVC）直径及变化通常在仰卧位测量，以评估危重症患者的血管内容量状态。许多科学学会都描述了仰卧位下IVC直径的测量方法。然而，由于担心误吸风险、呼吸力学恶化、颅内压升高以及改变患者体位所需的时间，危重症患者很少处于仰卧位。我们评估了床头抬高对IVC测量的影响。
我们对接受重症超声检查的危重症患者进行了一项前瞻性观察研究。床头角度为0°时，测量IVC最大直径（IVCmax0°）和最小直径（IVCmin0°）。然后将床头抬高至30°和45°，重复测量。计算每个床头抬高角度下的塌陷指数（CI），定义为（IVCmax - IVCmin）/IVCmax。然后比较平均差异。
研究了95例患者的便利样本，其中45%使用血管活性药物，44%自主呼吸。三个体位之间的CI无显著差异。我们发现45°时的IVCmax（2.09 cm）与0°时的IVCmax（1.96 cm）、45°时的IVCmin（1.75 cm）与0°时的IVCmin（1.59 cm）、45°时的IVCmax（2.09 cm）与30°时的IVCmax（1.97 cm）以及45°时的IVCmin（1.75 cm）与30°时的IVCmin（1.61 cm）之间存在显著差异（P≤0.0001）。
在接受目标导向超声检查的危重症患者群体中，将床头抬高至30°不会显著改变IVC测量值或CI。然而，在45°时，IVCmax和IVCmin直径显著增加，尽管CI无显著变化。将床头抬高至30°进行IVC超声测量不太可能产生具有临床意义的变化。
