Division of Nephrology, Department of Medicine, Loma Linda University Medical Center, Loma Linda, CA; University of Southern California, Los Angeles.
University of Southern California, Los Angeles.
Adv Chronic Kidney Dis. 2021 May;28(3):218-226. doi: 10.1053/j.ackd.2021.02.003.
Accurate assessment of relative intravascular volume is critical to guide volume management of patients with acute or chronic kidney disorders, particularly those with complex comorbidities requiring hospitalization or intensive care. Inferior vena cava (IVC) diameter variability with respiration measured by ultrasound provides a dynamic noninvasive point-of-care estimate of relative intravascular volume. We present details of image acquisition, interpretation, and clinical scenarios to which IVC ultrasound can be applied. The variation in IVC diameter over the respiratory or ventilatory cycle is greater in patients who are volume responsive than those who are not volume responsive. When 2 recent prospective studies of spontaneously breathing patients (n = 214) are added to a prior meta-analysis of 181 patients, for a total of 7 studies of 395 spontaneously breathing patients, IVC collapsibility index (CI) had a pooled sensitivity of 71% and specificity of 81% for predicting volume responsiveness, which is similar to a pooled sensitivity of 75% and specificity of 82% for 9 studies of 284 mechanically ventilated patients. IVC maximum diameter <2.1 cm, that collapses >50% with or without a sniff is inconsistent with intravascular volume overload and suggests normal right atrial pressure (0-5 mmHg). Inferior vena cava collapsibility (IVC CI) < 20% with no sniff suggests increased right atrial pressure and is inconsistent with overt hypovolemia in spontaneously breathing or ventilated patients. These IVC CI cutoffs do not appear to vary greatly depending on whether patients are breathing spontaneously or are mechanically ventilated. Patients with lower IVC CI are more likely to tolerate ultrafiltration with hemodialysis or improve cardiac output with ultrafiltration. Our goal for IVC CI generally ranges from 20% to 50%, respecting potential biases to interpretation and overriding clinical considerations. IVC ultrasound may be limited by factors that affect IVC diameter or collapsibility, clinical interpretation, or optimal visualization, and must be interpreted in the context of the entire clinical situation.
准确评估相对血管内容量对于指导急性或慢性肾脏疾病患者的容量管理至关重要，特别是对于需要住院或重症监护的复杂合并症患者。超声测量下腔静脉（IVC）直径随呼吸变化可提供相对血管内容量的动态、无创即时评估。我们介绍了 IVC 超声的图像采集、解读和临床应用细节。在对容量有反应的患者中，IVC 直径在呼吸或通气周期中的变化大于对容量无反应的患者。当将 2 项最近的自主呼吸患者前瞻性研究（n=214）加入到之前的 181 例患者的荟萃分析中，总共纳入 7 项共 395 例自主呼吸患者的研究，IVC 塌陷指数（CI）对预测容量反应性的敏感性为 71%，特异性为 81%，与 9 项共 284 例机械通气患者的研究相比，敏感性为 75%，特异性为 82%相似。IVC 最大直径<2.1cm，在有或无吸气努力时塌陷>50%与血管内容量超负荷不一致，提示右心房压正常（0-5mmHg）。无吸气努力时 IVC 最大直径<2.1cm 且 IVC 塌陷<20%提示右心房压升高，与自主呼吸或机械通气患者的明显血容量不足不一致。这些 IVC CI 截止值似乎不会因患者是否自主呼吸或机械通气而有很大差异。IVC CI 较低的患者更有可能耐受血液透析超滤或通过超滤增加心输出量。我们通常将 IVC CI 的目标范围设定为 20%至 50%，尊重对解释的潜在偏见并超越临床考虑因素。IVC 超声可能受到影响 IVC 直径或塌陷的因素、临床解释或最佳可视化的限制，必须结合整个临床情况进行解读。
