血流动力学监测和支持
# 血流动力学监测和支持
Hemodynamic Monitoring and Support
Vincent Jean-Louis MD PhD FCCM; Joosten, Alexandre MD, PhD; Saugel, Bernd MDVincent Jean-Louis MD 博士 FCCM; Joosten, Alexandre MD, PhD; Saugel, Bernd MD
Critical Care Medicine. 49: p 1638-1650, October 2021. 重症医学.49: p 1638-1650, October 2021.
doi: 10.1097/CCM.0000000000005213 doi: 10.1097/CCM.0000000000005213
Author Information 作者信息
1 Department of Intensive Care, Erasme Hospital, Université libre de Bruxelles, Brussels, Belgium. 1 比利时布鲁塞尔自由大学 Erasme 医院重症监护部。
2 Department of Anesthesiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium. 2 比利时布鲁塞尔自由大学 Erasme 医院麻醉学系。
3 Department of Anesthesiology and Intensive Care, Hôpitaux Universitaires Paris-Sud, Université Paris-Sud, Université Paris-Saclay, Paul Brousse Hospital, Assistance Publique Hôpitaux de Paris (APHP), Villejuif, France. 3 麻醉学和重症监护系，巴黎南大学，巴黎南大学，巴黎 - 萨克雷大学，保罗 - 布鲁斯医院，巴黎公共援助医院（APHP），法国维勒尤夫。
4 Department of Anesthesiology, Center of Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. 4 德国汉堡，汉堡大学医学中心麻醉学和重症监护医学中心麻醉学系。
Dr. Vincent drafted the article. Drs. Joosten and Saugel revised it for critical content. All authors read and approved the final version. 文森特博士起草了这篇文章。Joosten 和 Saugel 博士修改了文章的关键内容。所有作者都阅读并批准了最终版本。
Dr. Joosten’s institution received funding from Edwards Lifesciences. Dr. Saugel received funding from Edwards Lifesciences, Pulsion Medical Systems SE, CNSystems Medizintechnik GmbH, Retia Medical LLC, Philips Medizin Systeme Böblingen GmbH, and Tensys Medical. Dr. Vincent has disclosed that he does not have any potential conflicts of interest. Joosten 博士所在的机构接受了 Edwards Lifesciences 公司的资助。Saugel 博士从 Edwards Lifesciences、Pulsion Medical Systems SE、CNSystems Medizintechnik GmbH、Retia Medical LLC、Philips Medizin Systeme Böblingen GmbH 和 Tensys Medical 获得资助。文森特博士透露，他没有任何潜在的利益冲突。
For information regarding this article, E-mail: [jlvincent@intensive.org](mailto: jlvincent@intensive.org) 有关本文的信息，请发电子邮件：jlvincent@intensive.org
Critically ill patients are carefully and closely monitored to assess the nature and severity of their disease process and to assess the need for and impact of different therapies. All organs can be monitored, some more easily than others, with hemodynamic monitoring of the cardiovascular system being the most frequent. Hemodynamic monitoring techniques have progressed immensely since the very early days of intensive care and perhaps particularly over the past 50 years, moving from the very earliest, bulky sphygmographs to measure arterial pressure, to invasive catheters to assess cardiac output, to the more recent development of noninvasive, digital monitors providing continuous values of multiple hemodynamic variables. Concepts have also changed as we move from global macrohemodynamic monitoring toward a more regional, microcirculatory perfusion approach and from maximal monitoring for all, to a much more individualized approach. Here, we will briefly review these changes.
对危重病人进行严密的监测，以评估其疾病过程的性质和严重程度，并评估需要哪些治疗方法和疗效。所有器官都可监测，有的比其他器官更容易监测，其中心血管系统的血流动力学监测是最常见的。血流动力学监测技术从有重症监护开始就有了巨大的进步，也许在过去的 50 年里更是如此，从最早的测量动脉压的笨重血压计，到评估心输出量的有创导管，再到最近开发的的连续监测多种血流动力学参数的无创数字监测仪。随着我们从全身宏观血流动力学监测转向更多采用局部血流动力学监测、微循环灌注评估，以及从对所有人监测最大化转向评估更加个体化，观念也随之转变。此时，就这些变化进行简要回顾。
# SOME KEY STEPS IN THE HISTORY OF HEMODYNAMIC MONITORING 血流动力学监测史上的一些关键转变
# From Pressures to Blood Flow 从血压到血流
Monitoring of a patient’s hemodynamic status initially concentrated on measuring arterial pressure. The fundamental hemodynamic principle that pressure is determined by flow and vascular tone (or vascular resistance) soon became evident and had a major impact on the development of hemodynamic monitoring. As technology advanced, the ability to perform more advanced hemodynamic assessment enabled better description and characterization of the different types of shock (hypovolemic, cardiogenic, distributive, and obstructive) as proposed by Weil and Henning in 1979 (1 , 2 ). A clear separation was identified between shock with high systemic vascular resistance (SVR) (hypovolemic, cardiogenic, obstructive) and shock with low SVR (distributive), but it became apparent that the vascular resistance concept had major limitations. First, physiologically the line on a graph representing the relationship between intravascular pressure (on the y-axis) and flow (on the x-axis) does not start from the origin, as pressure is still positive in the absence of flow. Second, vasopressor therapy targeting an increase in SVR may result in an increase in arterial pressure but also a reduction in blood flow. Third, septic shock is not always associated with low SVR. These observations were the basis for the historical separation of septic shock into “cold” and “warm” types, possibly related to different types of organism—Gram+ve and Gram-ve—in particular ( 3 ), but, although still sometimes used in pediatric shock, these distinctions are not reliable. Patients with circulatory shock often present with a combination of several different types of shock; for example, in septic shock, cardiac output can be limited by hypovolemia and/or sepsis-related myocardial depression. In patients with acute respiratory failure, the effects of high airway pressures on right ventricular function can further complicate the hemodynamic pattern ( 4 ). Hence, the concept of characterizing shock according to vascular resistance lost popularity, and we have rather stayed focused on the primary variables of pressures and cardiac output.
对病人血流动力学状态的监测最初集中于测量动脉压。血流和血管张力（或血管阻力）决定压力的基本血流动力学原理很快被证实，并对血流动力学监测的发展产生了重大影响。随着技术的进步，具有了高级血流动力学评估能力，能够更好的描述和界定（1，2）不同类型的休克（低血容量、心源性、分布性和阻塞性），正如 Weil 和 Henning 在 1979 年所提出的。高外周血管阻力（SVR）（低血容量、心源性、阻塞性）和低 SVR 休克（分布性）被明确划分，但显然血管阻力的概念存在很大的局限性。首先，在生理上，代表血管内压力（Y 轴）和血流（X 轴）之间关系的示意图上的线条并不是从原点开始的，这是因为在没有血流的情况下，压力仍然可以是正的。第二，以增加 SVR 为目标的缩血管治疗可能会导致动脉压升高，但也会导致血流减少。第三，脓毒症休克的 SVR 并不总是低的。这些观察结果在历史上是将脓毒症休克分为 "冷" 和 "暖" 两种类型的依据，尤其是可能与革兰染色阳性和阴性微生物的不同类型有关（3），尽管有时也用于区分小儿休克，但是这些差别并不可靠。循环休克患者常常表现为几种不同类型的休克共存；例如，在脓毒症休克，心输出量可能因低血容量和 / 或脓毒症心肌抑制而下降。在急性呼吸衰竭患者中，高气道压力对右心室功能的影响可使血流动力学模式进一步复杂化（4）。因此，根据血管阻力来描述休克的概念已经不流行了，人们更关注压力和心输出量这两个直接参数。
# The Importance of Cardiac Output 心输出量的重要性
The first measurements of cardiac output, using indicator dilution techniques, were complicated and cumbersome ( 5 ) but helped us recognize the large variability in cardiac output that can exist in patients. The development of the balloon-tipped pulmonary artery catheter (PAC) by Swan et al ( 6 ) in 1970, just before the Society for Critical Care Medicine was founded in 1971, revolutionized our approach to the monitoring of cardiac output enabling the simpler pulmonary artery thermodilution technique ( 7 ). The PAC had the additional benefit of enabling multiple hemodynamic variables (pulmonary artery pressures, pulmonary artery occlusion pressure [PAOP], SVR and pulmonary vascular resistance, core body temperature, mixed venous oxygen saturation [Svo2]) to be measured and monitored simultaneously. 最早采用指示剂稀释技术的心输出量测量设备即复杂又笨重（5），但帮助我们认识到病人的心输出量可以存在很大的变异性。1970 年，在 1971 年重症医学会成立前，Swan 等人（6）发明了尖端带球囊的肺动脉导管（PAC），彻底改变了我们对心输出量的监测方法，简化了肺动脉热稀释技术（7）。PAC 的另一个好处是可以同时测量和监测多个血流动力学参数（肺动脉压、肺动脉阻塞压 [PAOP]、SVR 和肺血管阻力、核心体温、混合静脉血氧饱和度 [Svo2]）。
Measurement of the central venous pressure (CVP) had been introduced in the late 1960s, and already provided information on hemodynamic status, notably on right heart filling pressures and thus guidance for rapid fluid administration. However, the CVP does not correlate well with blood volume, as it reflects right ventricular function and venous compliance as well. Use of the PAC helped understand the differences between the CVP and the pulmonary artery wedge or occlusion pressure, which reflects left-sided filling pressures. Interpretation of the pressure waveforms was also promoted, enabling assessment of different conditions affecting the cardiac cycle. 中心静脉压（CVP）的测量在 20 世纪 60 年代末被引入，并且已经提供了关于血流动力学状态的信息，特别是关于右心充盈压，从而为快速输液提供指导。然而，CVP 与血容量的相关性并不好，因为它也反映了右心室功能和静脉顺应性。使用 PAC 有助于理解 CVP 与肺动脉楔压或肺动脉阻塞压之间的差别，后者反映了左侧的充盈压。它也促进了对压力波形的解释，能够评估影响心动周期的不同情况。
# The Concept of Oxygen Delivery/Oxygen Consumption Relationships and the Importance of Svo2 氧供 / 氧耗关系的概念和 Svo2 的重要性
Over the years, the emphasis in hemodynamic monitoring has moved progressively from the central to the peripheral circulation, getting closer to the cells. Tissue oxygen consumption (Vo2) varies with a patient’s clinical condition (inflammatory response, body temperature, mechanical ventilation, to name a few), and it is essential that sufficient oxygen can be delivered to meet differing cellular needs. Oxygen delivery (Do2) is determined by cardiac output and the arterial oxygen content. The concept of providing supranormal amounts of oxygen to avoid the so-called “oxygen debt” was promoted in the early 1990s by Shoemaker ( 8 , 9 ) to prevent complications in high-risk surgical patients. However, the excess treatments (e.g., fluids and inotropic therapy) necessary to achieve the marked increase in Do2 could be harmful in some patients. This was illustrated in a study by Hayes et al ( 10 ) in 1994 using massive doses of dobutamine to achieve the Do2 goal.
多年来，血流动力学监测的重点已经逐渐从中心循环转移到外周循环，越来越接近细胞。组织氧耗（Vo2）随病人的临床状况（炎症反应、体温、机械通气等）而变化，必须有足够的氧输送来满足不同的细胞需求。氧输送（Do2）是由心输出量和动脉血氧含量决定的。提供超常量的氧气以避免所谓的 "氧债" 的概念是由 Shoemaker（8,9）在 20 世纪 90 年代初提出的，以防止高危手术病人的并发症。然而，为实现 Do2 的明显增加而必须进行的过度治疗（如输液和正性肌力治疗）在一些病人中可能是有害的。1994 年 Hayes 等人（10）的一项研究说明了这一点，他们使用大量的多巴胺来达到 Do2 的目标。
The pendulum therefore shifted toward a more personalized approach, considering the needs of individual patients by using appropriate monitoring. A first strategy consisted of constructing individual Vo2/Do2 curves. Such an approach may make sense because physiologic studies have clearly shown the presence of a Vo2/Do2 dependency phenomenon in shock states ( 11 , 12 ). Furthermore, the fall in Do2 below a critical value (the so-called Do2crit) is associated with an abrupt increase in blood lactate levels (Fig. 1). The clinical application of the experimental data was nicely illustrated in the observation by Ronco et al ( 13 ) in 1993 that the same relationship can be documented in patients who die following withdrawal of life-support. However, the individual construction of Vo2/Do2 diagrams in patients has several difficulties. First, it could lead to spurious Vo2/Do2 relationships because of the presence of so-called “mathematical coupling of data,” in which cardiac output, hemoglobin concentration, and arterial oxygen saturation (Sao2) are present on both axes of the graph. To avoid this, it was suggested that Vo2 be determined by indirect calorimetry, but this does not really provide a “measured” Vo2 just a value estimated using another technique and is prone to other technical limitations ( 14 ). Second, the Vo2 can change quite rapidly with changes in patient condition or environmental factors.
因此，观念转向更具个体化的方法，通过恰如其分的监测来甄别患者的需要。第一个策略是构建个体化的 Vo2/Do2 曲线。这种方法可能是有意义的，因为生理学研究已经清楚地表明在休克状态存在 Vo2/Do2 依赖现象（11,12）。此外，Do2 下降到一定临界值以下（所谓的 Do2crit）与血乳酸水平的突然升高有关（图 1）。 Ronco 等人（13） 1993 年的观察研究中很好的验证了这一实验室研究结果在临床上的情况，在生命支持措施撤除后死亡的病人身上证明了存在有相同的关系。然而，在给每个病人绘制 Vo2/Do2 图表存在一些困难。首先，它可能导致虚假的 Vo2/Do2 关系，因为存在所谓的 "数据的数学耦合"，即心输出量、血红蛋白浓度和动脉血氧饱和度（Sao2）在图表的两个轴上都存在。为了避免这种情况，有人建议用间接热卡测量仪测定 Vo2，但这并不能真正 "测出" Vo2，只是换了一种技术的估计值，而且容易受到其他技术的限制（14）。其次，Vo2 可以随着病人状况或环境因素的变化而迅速变化。
![[Pasted image 20211001175844.png]]
The relationship between oxygen consumption (Vo2) and oxygen delivery (Do2). A, Blood lactate levels increase abruptly when Do2 falls below a critical value (Do2crit). Please note that Vo2 does not fall to the same extent as Do2 below Do2crit, indicating that oxygen extraction can still increase, although to a much lesser extent. B, The same concepts can be represented by a cardiac output/oxygen extraction diagram.
氧耗（Vo2）和氧输送（Do2）之间的关系。A，当 Do2 低于一定临界值（Do2crit）时，血乳酸水平就会突然增加。请注意，在 Do2crit 以下，Vo2 的下降程度与 Do2 的下降程度不一样，这表明氧的提取仍然可以增加，尽管程度要小得多。B, 同样的概念可以用心输出量 / 氧摄取关系图来表示。
The relationship between Vo2 and Do2 essentially represents oxygen extraction (the ratio of Vo2/Do2) or more simply the Svo2 when Sao2 is close to 100%. The use of the PAC enables easy collection of mixed venous blood from the tip of the catheter in the pulmonary artery. Reference Svo2 values in acutely ill patients may be a bit lower than the normal value of 75% in healthy humans, because the hemoglobin value in the critically ill is usually lower. Measurement of central venous oxygen saturation (Scvo2) through a central venous catheter has been proposed as a surrogate for Svo2, but is only an approximation, as venous saturations are not the same in the superior and the inferior parts of the body, and this relationship can be altered by the clinical situation ( 15 ). Hence, Scvo2 can only be considered as a gross approximation of Svo2. Nevertheless, Scvo2 can still provide valuable information to guide patient management.
Vo2 和 Do2 之间的关系基本上代表了氧摄取率（Vo2/Do2 之比），或者更简单地说，当 Sao2 接近 100% 时，代表了 Svo2。使用 PAC 可以方便地从肺动脉的导管尖端收集混合静脉血。急性病患者的 Svo2 参考值可能比健康人正常值 75% 要低一些，因为危重病人的血红蛋白通常较低。有人提出通过中心静脉导管测量中心静脉血氧饱和度（Scvo2）作为 Svo2 的替代值，但这只是一种近似值，因为身体上部和下部的静脉血氧饱和度不一样，而且这种关系会因临床情况而改变（15）。因此，Scvo2 只能被认为是 Svo2 的一个粗略的近似值。尽管如此，Scvo2 仍然可以提供有价值的信息来指导病人管理。
A suggested approach to interpreting S(c)vo2 is given in Figure 2. Svo2 can decrease in the presence of decreased arterial oxygen content (due to hypoxemia and/or anemia), an inadequate cardiac output or a significant increase in Vo2 (e.g., during exercise). It thus became evident that a cardiac output value cannot be correctly interpreted without a simultaneous Svo2 measurement and vice versa. Importantly, just as a low cardiac output does not need to be corrected in every case, a low Svo2 should not be corrected in every critically ill patient. This was documented in a large randomized controlled trial (RCT) by Gattinoni et al ( 16 ), in which bringing cardiac output and Svo2 to normal values did not influence mortality rates. 图 2 给出了解释 S (c) vo2 的建议。在动脉含氧量下降（由于低氧血症和 / 或贫血）、心输出量不足或 Vo2 明显增加（例如在运动中）的情况下，Svo2 会下降。因此很明显，如果没有同时测量 Svo2，就不能正确解释心输出量的值，反之亦然。重要的是，正如低心排不需要在每一种情况下都得到纠正一样，低 Svo2 也不应该是每一个危重病人都要纠正。Gattinoni 等人的一项大型随机对照试验（RCT）证实这一点（16），将心输出量和 Svo2 调整到正常值对死亡率并没有影响。
![[Pasted image 20211001182547.png]]
Interpretation of mixed (central) venous oxygen saturation (S(c)vo2). In ovals: things to do—in italic: treatment to consider. CO = cardiac output, PEEP = positive end-expiratory pressure, Sao2 = arterial oxygen saturation, Vo2 = oxygen consumption.
混合（中心）静脉血氧饱和度（S（c）vo2）的解释。椭圆形：要做的事；斜体：要考虑的治疗。CO = 心输出量，PEEP = 呼气末正压，Sao2= 动脉血氧饱和度，Vo2= 氧耗。
The observation that S(c)vo2 was low at the time of diagnosis of septic shock in many patients despite traditionally expected to be normal or high following initial resuscitation, led Rivers et al ( 17 ), in 2001, to propose to rapidly (in 6 hr) restore the Scvo2 to at least 70% in the early resuscitation of such patients. The so-called “early goal-directed therapy (EGDT)” was achieved by more aggressive fluid resuscitation and more than three times more patients receiving a blood transfusion compared with control patients. Applied in 130 patients versus 133 in the control group, EGDT was associated with substantially and significantly lower mortality, from 46.5% to 30.5%. This single-center study stimulated strong interest but also some criticism. Three large multicenter RCTs published in 2014 and 2015 ( 18–20 ) were unable to reproduce the results but were not true comparator studies of the original study by Rivers et al ( 17 ), notably including patients who were less severely ill and most of the patients in the EGDT group had normal S(c)vo2 values at the start of the EGDT strategy ( 21 ). Hence, application of this strategy cannot be considered as evidence-based, but it does not invalidate the importance of S(c)vo2 in interpreting hemodynamic status in patients who do not improve promptly ( 22 ).
观察到许多病人在诊断脓毒症休克时的 S (c) vo2 很低，尽管传统上预计在最初复苏后会正常或很高，这使得 Rivers 等人（17）在 2001 年提出在此类病人的早期复苏中迅速（6 小时内）将 Scvo2 恢复到至少 70%。通过更积极的液体复苏来达到所谓的 "早期目标导向治疗（EGDT）"，与对照组患者相比，接受输血的患者多了三倍。在 130 名患者中应用 EGDT，而对照组为 133 名，EGDT 大幅降低了死亡率，从 46.5% 降至 30.5%。这项单中心研究引起了极大兴趣，但也有一些批评。2014 年和 2015 年发表的三项大型多中心 RCT 研究（18-20）都无法重现改结果，但它们并不是 Rivers 等人（17）原始研究的真正的对比研究，特别是在纳入了病情不重的患者，而且 EGDT 组的大多数患者在 EGDT 策略开始时 S（c）vo2 的值是正常的（21）。因此，应用这一策略不能被认为是循证的，但这并不意味着就否定了对病情未迅速改善的患者用 S (c) vo2 来解释血流动力学状态的重要性 (22)。
The addition of the venoarterial Pco2 (VAPco2) gradient may be useful in the presence of persisting hemodynamic alterations when the Svo2 is normal or high. In these conditions, an increased VAPco2 gradient greater than 6 mm Hg may indicate that peripheral blood flow is still inadequate ( 23 ).
当 Svo2 正常或升高时，进一步查看静脉 - 动脉 Pco2（VAPco2）梯度可能对判断血流动力学改变持续存在是有用的。在这些情况下，VAPco2 梯度升高大于 6 毫米汞柱可能表明外周血流仍然不足（23）。
# Blood Lactate Concentrations 血乳酸浓度
In shock, falling tissue oxygen concentrations result in anaerobic metabolism with the increased formation of lactate, making blood lactate concentration a useful index of altered tissue perfusion ( 24 ). This recognition was an important step in the evolution of hemodynamic monitoring. Based on the fundamental studies of Huckabee on the relationship between pyruvate and lactate (25– 27 ), Broder and Weil ( 28 ) proposed in 1969 that excess lactate should be measured to assess the role of “oxygen debt” in prognostication of shock states. The concept of oxygen debt was challenged, however, as it is more relevant to the field of strenuous exercise, and the measurements of pyruvate are too complex and cumbersome to become routinely used in clinical practice. Numerous articles have focused on the pathophysiology of lactic acidosis in septic shock, emphasizing that hyperlactatemia is not due only to cellular hypoxia, but other cellular derangements can be involved ( 24 ). Nevertheless, blood lactate concentrations are well-established as an index of the severity of shock ( 29 ) and hyperlactatemia (> 1.5–2 mmol/L) as a marker of poor outcome.
休克时，组织氧浓度下降导致无氧代谢，乳酸生成增加，使血乳酸浓度成为组织灌注改变的有用指标（24）。这一认识是血流动力学监测发展中的重要一步。基于 Huckabee 对丙酮酸和乳酸关系的基本研究（25-27），Broder 和 Weil（28）在 1969 年提出应对过量的乳酸进行测量以评估 "氧债" 判断休克预后的作用。然而，氧债的概念存有质疑，因为它更多的是与剧烈运动方面有关，而丙酮酸的测量过于复杂和繁琐不能作为常规用于临床。专注于脓毒症休克乳酸酸中毒病理生理学方面的很多文献强调高乳酸血症不仅是由于细胞缺氧，还可能涉及其他细胞水平失调（24）。尽管如此，血乳酸浓度作为休克严重程度的指标（29）以及高乳酸血症（>1.5-2 mmol/L）作为预后不佳的指标已经得到公认。
The concept of measuring serial blood lactate concentrations over time to monitor patient response to treatment and evolution soon emerged. In early studies in the 1980s, blood lactate concentrations were shown to decrease by 10% over one hour in the most straightforward patients with circulatory shock who responded to fluid administration ( 30 ). Further studies confirmed that a rapid decrease in lactate concentration is associated with a better prognosis in various groups of critically ill patients ( 31 ). As lactate concentrations reflect the balance between production and clearance (primarily by the liver), the term “lactate clearance” is not appropriate to describe lactate kinetics ( 32 ). Development of rapid bedside analyzers has simplified measurement of lactate concentrations. Treatment based primarily on lactate kinetics ( 33 ) has been attempted but this approach is not entirely convincing, because the changes in lactate concentrations are slow ( 31 ). Hence, the assessment of serial blood lactate levels is considered as helpful to assess the response to therapy rather than to precisely guide it ( 24 ).
随时间连续多次测量血乳酸浓度来监测病人对治疗的反应和病情进展的概念很快出现了。在 20 世纪 80 年代的早期研究中，对明显补液有反应的循环性休克患者，显示血乳酸浓度一小时内下降了 10%（30）。进一步的研究证实，血乳酸浓度快速下降的各组危重患者其预后都更好（31）。由于乳酸浓度反映了乳酸的生成和清除（主要由肝脏清除）之间的平衡，"乳酸清除" 一词不适合描述乳酸动力学（32）。快速床旁分析仪的出现简化了乳酸水平的检测。尝试采用主要基于乳酸动力学的治疗后（33），发现该方法不尽如人意，因为乳酸浓度的变化很慢（31）。因此，连续评估血乳酸水平被认为有助于评估疗效，但不能精确指导治疗（24）。
# The Importance of Peripheral Perfusion 外周灌注的重要性
The attempt to selectively increase the regional blood flow to some organs has led to increased interest in monitoring regional blood flow, but this is difficult in the clinical setting. Measurements of blood flow in the hepatosplanchnic circulation are possible but quite invasive ( 34 ). Gastric tonometry became popular in the 1990s. This minimally invasive technique assesses gastric mucosal perfusion via a modified nasogastric tube equipped with a balloon including some saline or even Co2. Monitoring of critically ill patients using this technique was shown to decrease mortality in a study published in 1992 ( 35 ), but the existence of many artifacts leading to inconsistent results led to this approach being abandoned. More recently, measurements of urethral perfusion have also been proposed ( 36 ). Studying the peripheral blood flow to the extremities could be valuable. Joly and Weil ( 37 ) proposed already in 1969 to monitor the toe temperature, but this strategy is limited in the presence of peripheral arteriopathy. The assessment of skin perfusion has been pursued by different techniques, from the simple capillary refill time ( 38 ) to the more complex use of Doppler techniques ( 39 ). Assessment of peripheral perfusion has been, and will remain, an important component of the clinical evaluation of the critically ill.
想要选择性的增加一些器官局部血流的尝试让人对局部血流监测更感兴趣，但这在临床上是很困难的。测量肝脾循环的血流到是有可能，但侵入性较大（34）。20 世纪 90 年代，胃张力测量法开始流行。这种微创技术通过带有球囊的改良鼻胃管来评估胃粘膜灌注，球囊内含有一定量的生理盐水甚或 Co2 。1992 年发表的一项研究显示，使用这种技术监测危重病人可降低死亡率（35），但由于存在许多伪差导致结果不一致，因此这种方法被放弃了。最近，也有人提出了测量尿道灌注的方法（36）。研究流向四肢的外周血流可能是有价值的。Joly 和 Weil（37）在 1969 年已经提出监测脚趾温度，但这种方法在有外周动脉病变时价值有限。有多种方法评估皮肤灌注，从简单的毛细血管再充盈时间（38）到更复杂的多普勒超声技术的使用（39）。外周血流灌注的评估一直是并将继续是危重病人临床评估的一个重要组成部分。
# The Importance of the Microcirculation 微循环的重要性
Restoring and maintaining adequate tissue oxygenation is the ultimate goal of hemodynamic resuscitation and management. Estimation of Do2 includes the components cardiac output, hemoglobin, and Sao2, but this neglects not only the distribution of cardiac output to the various organs but also distribution within the organs. Several methods exist to explore the microcirculation ( 40 ), including laser Doppler that measures RBC speed in small tissues, intravital microvideo-surface microscopy applied directly on organs, microvideo-surface microscopy by orthogonal polarization spectral or sidestream darkfield imaging, and nail capillarovideoscopy. For clinical practice, one needs the devices to be reliable and reproducible, easy to use, and which provide data that are easy to interpret by most medical and paramedical staff ( 41 ).
恢复和维持足够的组织氧合是血流动力学复苏和管理的最终目标。对 Do2 的评估包括心输出量、血红蛋白和 Sao2 等组成部分，但这不仅未考虑心输出量在各器官的分布，也未考虑器官内的分布。有几种方法可以探究微循环（40），包括测量小块组织中 RBC 速度的激光多普勒，直接用于器官的活体微视频 - 表面显微镜（微视频 - 表面显微镜采用正交偏振光谱或侧流暗场成像技术），以及指甲毛细血管视频检查。对于临床实践，人们需要这些设备是可靠的、可重复的、易于使用的，而且提供的数据对大多数医务人员和准医务人员来说是容易解释的（41）。
Handheld vital microscopy assessing the sublingual microcirculation has been the most widely studied approach and has enabled persistent microcirculatory alterations to be depicted in critically ill patients with sepsis ( 42 ). The time course of these changes has been associated with organ dysfunction and mortality ( 43 ) and microvascular changes are frequently observed even after global variables have normalized ( 43 , 44 ). This approach has been used to assess the effects of various interventions on the microcirculation, including the titration of vasopressor support ( 45 ). Whether these measurements can be used to adjust treatment such that they have an impact on patient outcome remains to be proven.
评估舌下微循环的手持式生命显微镜是研究最广泛的方法，它能够展示脓毒症重症患者持续存在的微循环改变（42）。这些改变的时间过程与器官功能障碍和死亡率有关（43），即使在全局参数恢复正常后，也经常能观察到微血管有变化（43,44）。这种方法已被用于评估各种干预措施对微循环的影响，包括循环支持时滴定升压药物（45）。这些测量结果是否可以用来调整治疗，从而对病人的预后产生影响，还有待证明。
# The Move Toward Less Invasive Techniques 朝着微创技术发展
# Decreasing Use of the PAC. PAC 的使用在减少。
The use of the PAC has decreased worldwide over the last 2 decades. One argument to support this trend was that RCTs have not consistently shown a reduction in mortality associated with the use of PACs ( 46–48 ). However, a reduction in mortality has not been shown with other monitoring techniques (Table 1), such as the electrocardiogram or pulse oximetry ( 49 ), for example, but these are still widely used. Gastric tonometry was shown to influence mortality ( 35 ), and yet this technique has been abandoned. Furthermore, a monitoring technique can only improve outcomes if the data generated can be used to influence management in a way that can reduce mortality. Hence, the negative observations from the RCTs suggest that PAC-derived measurements cannot influence patient management and/or that the changes in management do not influence mortality. The reduced use of the PAC in recent years is likely explained more by the greater availability and use of echo-Doppler techniques and other newer, less invasive hemodynamic monitoring techniques. Although these newer devices have reduced the use of PAC-derived monitoring, PAC-derived variables remain of value in certain complex patients, particularly those with severe cardiorespiratory failure ( 60 ).
在过去的 20 年里，全世界 PAC 的使用已经减少了。支持这一趋势的一个论点是，RCTs 研究没有一致性显示出使用 PACs 能带来死亡率的下降（46-48）。然而，其他监测技术（表 1）也没有显示出死亡率的降低，例如心电图或脉搏血氧仪（49），但它们仍被广泛使用。胃张力测量法被证明会影响死亡率（35），然而这种技术已经被放弃了。此外，一种监测技术只有在其产生的数据以能够降低死亡率的方式来影响患者管理时才会改善预后。因此，RCTs 的阴性结果表明，PAC 衍生的测量结果不能影响病人的管理，和 / 或管理上的改变不能影响死亡率。近年来，PAC 的使用减少，可能更多的是由于超声多普勒技术和其他较新的、微创血流动力学监测技术的普及和使用。虽然这些更新的设备减少了 PAC 的使用，但 PAC 参数对某些复杂的病人，特别是那些严重心肺衰竭的病人仍有价值（60）。
| Strategy | References |
|---|---|
| In critically ill patients (in general) | |
| Higher vs lower mixed venous oxygen saturation targets in critically ill patients | Gattinoni et al (16) |
| Higher vs lower cardiac output in critically ill patients | Gattinoni et al (16) |
| Higher vs lower hemoglobin targets for blood transfusion | Hébert et al (50) |
| The pulmonary artery catheter | Sandham et al (48), Richard et al (51), Harvey et al (52) |
| Colloids vs crystalloids | Myburgh et al (53), Annane et al (54) |
| In septic patients (in particular) | |
| Vasopressin administration | Russell et al (55), Gordon et al (56) |
| Higher vs lower hemoglobin targets for blood transfusion | Holst et al (57) |
| Higher vs lower arterial pressure targets | Asfar et al (58) |
| Early goal-directed therapy | Yealy et al (18), Peake et al (19), Mouncey et al (20) |
| Levosimendan administration | Gordon et al (59) |
| 策略 | 参考文献 |
|---|---|
| 针对重症患者(总体) | |
| 重症患者混合静脉血氧饱和度高低目标对比 | Gattinoni et al (16) |
| 重症患者心输出量高低对比 | Gattinoni et al (16) |
| 输血时血红蛋白目标高低对比 | Hébert et al (50) |
| 肺动脉导管 | Sandham et al (48), Richard et al (51), Harvey et al (52) |
| 胶体液和晶体液比较 | Myburgh et al (53), Annane et al (54) |
| 针对脓毒症患者 (特定) | |
| 升压药物的使用 | Russell et al (55), Gordon et al (56) |
| 输血时血红蛋白目标高低对比 | Holst et al (57) |
| 动脉压目标高低对比 | Asfar et al (58) |
| 早期目标导向治疗（EGDT） | Yealy et al (18), Peake et al (19), Mouncey et al (20) |
| 左西孟旦的使用 | Gordon et al (59) |
Some Hemodynamic Strategies That Have Been Studied in Randomized Controlled Trials in Critically Ill Patients But Failed to Show a Reduction in Mortality
一些针对重症患者开展过随机对照试验的血流动力学策略，但结果未能降低死亡率。
# The Development of Echo-Doppler. 超声多普勒的发展。
It is beyond the scope of this review to discuss the echo-Doppler technique in detail. Echo-Doppler, first developed in the 1950s but only becoming more widely used clinically in the 1970s ( 61 ), was initially reserved for use in cardiology, but the development of simplified, more mobile devices and availability of training programs around the globe have enabled echo-Doppler to be used routinely in many ICUs. It is not necessary to be an expert in echo-Doppler to use it in the management of critically ill patients; knowledge and expertise can be relatively limited, covering just the necessary basics to perform a so-called focused cardiac ultrasound ( 62 ); cardiologists can still be called if more complex evaluations are needed. Echocardiography can differentiate between the different types of shock ( 2 ) and serial examination can be used to monitor response to treatment.
超声多普勒技术的详细讨论不在本文范围。超声多普勒最早是在 20 世纪 50 年代出现的，但在 20 世纪 70 年代才开始在临床上广泛使用（61），最初只用于心脏病，但随着设备更简单、便携以及全球各地培训项目的开展，使超声多普勒在许多 ICU 中得到了常规应用。在危重病人的管理中，不一定要成为超声多普勒的专家；相对有限的超声专业知识就行，只需掌握必要的基础知识就能进行所谓的重点心脏超声检查（62）；如果需要更复杂的评估，仍然可以请心脏科医生来。超声心动图可以对不同类型的休克进行鉴别诊断（2），连续超声检查可用于监测治疗的反应性。
# Availability of Less Invasive Methods for Cardiac Output Measurement. 测量心输出量的现有微创技术。
Other indicator dilution methods to measure cardiac output were developed to avoid the need for a PAC (Fig. 3), including transpulmonary thermodilution and lithium dilution ( 63–65 ). However, a (central) venous catheter is still required for indicator injection and an arterial catheter to detect changes in indicator temperature or concentration.
已发明的不用 PAC 的指示剂稀释法测量心输出量的其他方法包括经肺热稀释法和锂稀释法（图 3）（63-65）。然而，仍然需要一根（中心）静脉导管来注射指示剂，以及一根动脉导管来检测指示剂的温度或浓度的变化。
![[Pasted image 20211002055148.png|1000]]
Timeline showing the development of some techniques to measure or estimate cardiac output
一些测量或估测心输出量技术的研发时间线
Pulse wave analysis, which uses a mathematical analysis of the arterial blood pressure waveform to estimate cardiac output, has also been proposed ( 66 , 67 ). With pulse wave analysis, cardiac output is estimated continuously, with a rapid response time; it can therefore be used to assess fluid responsiveness during, for example, a fluid challenge maneuver or a passive leg raising test. However, estimation of cardiac output using pulse wave analysis relies on theoretical assumptions and measurement performance is limited in patients with rapid changes in vasomotor tone, either spontaneous or drug-induced. Different pulse wave analysis devices—invasive, minimally invasive, and noninvasive—are available for this purpose, and may use external, internal, or no calibration to calibrate the estimated cardiac output values ( 66 ). Each has benefits and limitations, but detailed discussion is beyond the scope of this article (Table 2).
脉搏波形分析，使用动脉血压波形的数学分析来估计心输出量，也已被提出（66,67）。通过脉搏波形分析，可以连续估计心输出量，反应时间快；因此，它可以用来评估液体反应性，例如在快速补液或被动抬腿试验中。然而，使用脉搏波形分析估计心输出量依赖于理论上的假设，在血管张力快速变化的病人中，无论是自发的还是药物引起的，测量性能都会受限。不同的脉搏波形分析设备 - 有创的、微创的和无创的 - 都可用于此目的，并可使用外部、内部校准装置或无需校准装置对估测的心输出量值进行校准（66）。每一种都有其好处和局限性，本文不做详细讨论（表 2）。
| Method | Advantages | Limitations |
|---|---|---|
| Pulmonary artery thermodilution | Clinical reference method | Invasiveness, catheter-related major complications |
| Additional variables: cardiac filling pressures and mixed venous oxygen saturation | Sources of error including the temperature and volume of the injectate, timing of indicator injection during respiratory cycle | |
| Measurement error in patients with intracardiac shunts and tricuspid valve abnormalities | ||
| Transpulmonary indicator dilution | ||
| Thermodilution | Good performance | Invasiveness, complications associated with central venous and (femoral) arterial catheters |
| Additional variables: volumetric preload variables, extravascular lung water and pulmonary vascular permeability index | ||
| Lithium dilution | Good performance | Invasiveness |
| Response time | ||
| Costs | ||
| Not available everywhere | ||
| Minimally invasive pulse wave analysis | No external calibration | Depends on impeccable blood pressure waveform quality |
| Beat-to-beat continuous monitoring | Stroke volume algorithms based on theoretical assumptions | |
| Operator independent | Marked alterations or rapid changes in systemic vascular resistance make cardiac output estimations unreliable (e.g., in patients with shock) | |
| Plug and play (easy to set up) | ||
| Additional variables: stroke volume variation/pulse pressure variation | ||
| Transesophageal Doppler | Beat-to-beat continuous cardiac output monitoring | Operator dependent |
| Probe not fixed: frequent need for repositioning | ||
| Sedation and mechanical ventilation required | ||
| Assumes constant distribution of arterial blood flow between the upper and lower parts of the body | ||
| Depends on the correct estimation of the diameter of the aorta | ||
| Finger cuff method (noninvasive pulse wave analysis) | No external calibration | Not reliable in presence of finger edema and poor peripheral perfusion |
| Beat-to-beat continuous cardiac output monitoring | Poor performance, especially in the presence of vasoconstriction | |
| Operator independent | ||
| Plug and play (easy to set up) | ||
| Additional variables: SVV/PPV | ||
| Pulse wave transit time | No need for calibration | Not reliable in the presence of arrhythmia |
| Operator independent | Not reliable if vasoconstriction | |
| Plug and play (easy to set up) | Does not provide SVV/PPV | |
| Thoracic bioimpedance and bioreactance | No calibration | Unreliable in many cases of arrhythmia, electrical interference, internal or external pacemakers, movement (motion artifacts), anatomic shunts, pleural and pericardial effusions, foreign bodies in the chest, pulmonary edema |
| Operator independent | Electrode positioning (interference with some surgical sites) | |
| Plug and play (easy to set up) | ||
| 方法 | 优点 | 缺点 |
|---|---|---|
| 肺动脉热稀释 | 临床参考方法 | 有创，导管相关的主要并发症 |
| 额外参数：心脏充盈压和混合静脉血氧饱和度 | 误差来源包括注射剂的温度和量，在呼吸周期中指示剂注射的时机 | |
| 心内分流和三尖瓣异常患者存在测量误差 | ||
| 经肺指示剂稀释 | ||
| 热稀释 | 表现优异 | 有创，中心静脉和（股）动脉导管相关并发症 |
| 额外参数：前负荷容量参数，血管外肺水以及肺血管通透指数 | ||
| 锂稀释 | 表现优异 | 有创 |
| 反应时间 | ||
| 费用 | ||
| 并非在哪儿都能用 | ||
| 微创脉搏波形分析 | 无需额外校准 | 取决于质量好的血压波形 |
| 持续检测每次心跳 | 根据理论假设计算每搏量 | |
| 无操作者依赖性 | 外周血管阻力显著或迅速变化导致心输出量的估计不可靠（如，休克患者） | |
| 即插即用 (易于建立) | ||
| 额外参数：每搏量变异（SVV）/脉搏压变异（PPV） | ||
| 经食道超声 | 逐次心搏心输出量检测 | 操作者依赖性 |
| 探头不固定：经常需要复位 | ||
| 需要镇静和机械通气 | ||
| 假设身体上下部分的动脉血流分布是不变的 | ||
| 取决于对主动脉直径估计值的校准 | ||
| 指套法（无创脉搏波形分析） | wuxu额外校准 | 手指水肿和外周灌注不良时不可靠 |
| 逐次心搏心连续输出量监测 | 表现不佳，尤其是有血管收缩时 | |
| 无操作者依赖性 | ||
| 即插即用(易于建立） | ||
| 额外参数：SVV/PPV | ||
| 脉搏波形传播时间 | 无需校准 | 心律失常时不可靠 |
| 无操作者依赖性 | 如果血管收缩则不可靠 | |
| 即插即用（易于建立） | 不能提供 SVV/PPV | |
| 经胸生物阻抗和生物电抗 | 无需校准 | 许多情况下不可靠，如心律失常、电气干扰、心内或胸外起搏、运动（运动伪差）、解剖分流、胸腔积液和心包积液、胸内异物、肺水肿 |
| 无操作者依赖性 | 点击位置（受到一些手术部位的影响） | |
| 即插即用（易于建立） | ||
Advantages and Limitations of Techniques for Cardiac Output Determination
心输出量测量技术的优缺点
Other less invasive methods for cardiac output monitoring, including noninvasive pulse wave analysis (e.g., finger cuff method), pulse wave transit time, Co2 rebreathing, thoracic bioimpedance and bioreactance, are not reliable enough for routine use in critically ill patients.
其他监测心输出量的微创技术，包括无创脉搏波形分析（如指套法）、脉搏波传输时间、Co2 重复吸入、胸腔生物阻抗和生物电抗等，在危重病人的常规使用上不够可靠。
# HEMODYNAMIC MONITORING DURING ADMINISTRATION OF KEY THERAPEUTIC INTERVENTIONS IN SHOCK 休克进行关键治疗干预时的血流动力学监测
As proposed by Weil and Shubin (68) many years ago, the patient with shock should be managed according to the Ventilate, Infuse, Pump approach. Each of these management components requires close and specific hemodynamic monitoring.
正如 Weil 和 Shubin (68) 多年前提出的，休克患者应按照通气、输液、泵（VIP）的方法进行管理。这些管理的每一个部分都需要严密和特定的血流动力学监测。
# Ventilate 通气
It may not seem intuitive that hemodynamic management requires an initial focus on ventilation, but an adequate oxygen supply is essential to restore an adequate Do2. The use of invasive mechanical ventilation can decrease the oxygen demand of the respiratory muscles, thus facilitating achievement of adequate tissue Do2. Optimal timing of endotracheal intubation is thus an important part of the resuscitation process.
血流动力学管理要求一开始就关注通气，这似乎有违直觉，但充足的氧气供应对于恢复足够的 Do2 是至关重要的。使用有创机械通气可以减少呼吸肌的需氧量，从而有利于实现足够的组织 Do2。因此，气管插管的最佳时机是复苏过程的一个非常重要的组成部分。
# Infuse 输液
Fluid administration remains an essential component of the management of all forms of shock. Initially reserved for hypovolemic states, and to some extent septic shock, fluid administration is also essential in cardiogenic shock, because the vasoconstrictive state results in extravasation of fluid into the interstitium. Hence, management of cardiogenic shock using prudent fluid administration has become a standard, even when cardiogenic lung edema is present ( 69 ).
输液仍然是所有休克管理中的一个重要组成部分。最初只用于低血容量状态，以及某些脓毒症休克，但在心源性休克，输液也是必不可少的，因为血管收缩状态会导致液体外渗到间质中。因此，即使存在心源性肺水肿，谨慎补液已经成为心源性休克管理的标准（69）。
How much fluid should be given has been a topic of intense discussion. Attempts to predetermine the amount of fluid required have been unsuccessful in all subsets of patients. Hence, the amount of fluid to be given should be guided by appropriate and adequate hemodynamic monitoring in individual patients. Monitoring arterial pressure alone may be sufficient when vascular tone is well preserved, but in septic shock the cardiac output may increase much more than the arterial pressure ( 70 ), so that a cardiac output measurement is desirable. Although a low CVP can increase confidence that fluid administration will be safe, a single CVP measurement is not a reliable indicator of fluid requirements ( 71 ). Changes in CVP during the administration of a fluid bolus provide more useful information about the tolerance to fluids. The benefit (increase in cardiac output) versus risk (of edema formation) of fluid is the basis for the fluid challenge technique, in which a relatively small amount of fluids (usually around 200 mL) is given over a relatively short period of time (usually around 10 min) while carefully monitoring safety limits ( 72 ).
应该给多少液体一直争论激烈。试图预先确定需要多少液体在所有的病人亚群中都未成功。因此，液体量的给予应该由对每个患者进行恰如其分的血流动力学监测来指导。当血管张力完好存在时，仅监测动脉血压可能就足够了，但是在脓毒症休克，心输出量的增加幅度可能远大于动脉压（70），因此，需要监测心输出量。虽然低 CVP 可以增加补液的可信度，但单纯 CVP 测量值并不是需要输液的可靠指标（71）。在快速输液过程中，CVP 的变化对液体耐受性提供了更有用的信息。液体的利（增加心输出量）与弊（水肿的形成）快速补液试验技术的基础，在相对较短的时间内（通常约 10 分钟）给予相对少量的液体（通常约 200 毫升），同时仔细监测安全界限（72）。
In patients treated with controlled mechanical ventilation, the effects of intermittent positive pressure ventilation on preload and stroke volume were proposed to detect fluid responsiveness. If mechanical ventilation induces respiratory variations in stroke volume (SVV) or in arterial pulse pressure (PPV), it is more likely that the patient is preload-dependent. During fluid administration, the decrease in PPV inversely correlates with the increase in cardiac output ( 73 ). However, first introduced in the late 1990s, these dynamic measures of fluid responsiveness based on cardiopulmonary interactions have their limitations. PPV is only reliable in mechanically ventilated patients who are profoundly sedated (no spontaneous breathing) receiving a relatively large tidal volume, with modestly altered lung compliance, and no right ventricular failure, intra-abdominal hypertension, or severe arrhythmias. Conditions for its use are usually met during surgical interventions, where goal-directed fluid management strategies based on such indices (PPV or SVV) have been shown to reduce postoperative complications ( 74 ); however, in the ICU, very few patients fulfill optimal conditions ( 75 , 76 ). Additional tests that rely on the dynamics of PPV have been proposed, including the positive end-expiratory pressure or the tidal volume challenge ( 77 ).
在接受控制性机械通气治疗的患者中，有人提出用间歇性正压通气对前负荷和每搏量的影响判断液体反应性。如果机械通气引起随呼吸的每搏量变异（SVV）或动脉脉搏压变异（PPV），那么病人很有可能存在前负荷依赖性的。在输液期间，PPV 的下降与心输出量的增加成反比（73）。然而，这些 20 世纪 90 年代末首次引入的基于心肺交互作用的液体反应性动态测量方法有其局限性。PPV 只在深度镇静（无自主呼吸），潮气量相对较大，肺顺应性改变适中，没有右心室衰竭、腹腔内高压或严重心律失常的机械通气的病人中才可靠。在外科手术中通常满足这些应用条件，基于此类指标（PPV 或 SVV）的目标导向液体管理策略已被证明可以减少术后并发症（74）；然而，在 ICU 中，很少有病人达到最佳条件（75,76）。已经提出了基于 PPV 动态变化的其他测试方法，包括呼气末正压或潮气量负荷试验（77）。
A passive leg raising test was proposed as an alternative method ( 78 ), avoiding, in principle, the fluid bolus of a fluid challenge. However, there are two key limitations: one is that the test may represent a stimulus in the unsedated patient, resulting in an adrenergic response regardless of the fluid status; the other is that if there is a positive response (i.e., indicating fluid responsiveness), the increase in stroke volume is very transient, and appropriate monitoring must be used to ensure any change is identified reliably.
作为替代有人提出被动抬腿试验（78），原则上避免了为了容量负荷试验需要快速补液。然而，有两点重要限制：一是该试验对非镇静的病人来说可能是一种刺激，导致肾上腺素能反应，而与液体状态无关；二是如果反应为阳性（即表明有液体反应性），此时每搏量的增加是非常短暂的，必须采用适当的监测确保每搏量的任何变化都能可靠分辨。
# Type of Fluid and Blood Transfusions. 输液和输血的种类。
A comprehensive discussion on the different effects of different colloids and crystalloids (albumin or hydroxyethyl starch, saline or balanced solutions) is beyond the scope of the present review, but fluid choices remain a highly controversial topic.
本文不对各种胶体和晶体液（白蛋白或羟乙基淀粉、生理盐水或平衡盐液）的各种效果进行全面讨论，但液体的选择仍然是一个极具争议的话题。
Transfusion strategies have also evolved with time. When a patient should be transfused remains a matter of debate. There is no doubt that the maintenance of hemoglobin levels greater than 10 g/dL resulted in excess transfusions, but the pendulum may have swung too far in the other direction following RCTs showing similar outcomes when transfusions are given only when hemoglobin falls less than 7 g/dL ( 57 ). A recent review of the available data indicated that blood transfusion may increase Vo2 in critically ill patients ( 79 ), and there is now broad consensus that the decision to transfuse should not be based on a hemoglobin level alone but also on other factors, including patient age, hemodynamic status, and cardiovascular comorbidity ( 80 ). A reasonable approach today would be that blood transfusion can be safely withheld when the hemoglobin is above 9 g/dL and should be given when hemoglobin is below 7 g/dL; decisions to transfuse should be individualized when the hemoglobin is between these two values.
输血策略同样随时间而演变。病人何时应该输血仍然是一个有争议的问题。毫无疑问，保持血红蛋白水平高于 10g/dL 会导致过量输血，但 RCT 研究显示血红蛋白低于 7g/dL 时才输血预后相似，导致矫枉过正（57）。对现有证据的最新综述显示，输血可能会增加危重病人的 Vo2（79），现在的广泛共识认为，决定是否输血不要仅看血红蛋白水平，还要考虑其他因素，包括病人年龄、血流动力学状态和心血管疾病（80）。目前合理的做法是，当血红蛋白高于 9g/dL 时可以安全地停止输血，当血红蛋白低于 7g/dL 时应输血；当血红蛋白在这两个数值之间时，应根据个体化决定是否输血。
# Pump 泵
Various vasopressor agents have been proposed, including norepinephrine, dopamine, phenylephrine, metaraminol, mephentermine, and others, but norepinephrine is now established as the initial vasopressor of choice ( 81 ). Importantly, administration of vasopressors can decrease blood flow to nonvital organs, in particular to the kidneys. The pharmacology of dopamine was particularly appealing for its use as a vasopressor, because dopaminergic receptors are more numerous in the splanchnic and renal circulations. However, the administration of low-dose dopamine, although initially promoted by MacCannell et al ( 82 ) in the 1960s, was later shown not to be associated with renal protective effects in patients with shock ( 83 ). The use of dopamine has been shown to be associated with higher mortality rates than norepinephrine in shock states ( 81 , 84 ) and use of dopamine as a vasopressor has been largely abandoned.
指定使用的各种升压药物，包括去甲肾上腺素、多巴胺、苯肾上腺素、间羟胺、美芬丁胺等，目前已确定去甲肾上腺素为初始首选升压药物（81）。重要的是，给与升压药物会减少非生命器官的血流量，特别是肾脏。多巴胺的药理作用特别适合把它用作升压药，因为脾肾循环中有大量多巴胺能受体。然而，尽管最初 MacCannell 等人 (82) 在 20 世纪 60 年代提倡使用小剂量多巴胺，但后来证明在休克病人中没有肾脏保护作用（83）。在休克状态下，使用多巴胺的死亡率高于去甲肾上腺素（81,84），因此严格来说已经放弃了把多巴胺用作升压药。
The place of other vasopressor agents remains undefined. The risk with these agents is a decrease in cardiac output. Vasopressin has been widely used without evidence of clinical benefit. Benefit may be found when vasopressin is administered early to prevent capillary leakage, but the risk is that it may decrease blood flow, especially in the hepatosplanchnic and the coronary circulations. Hence, close hemodynamic monitoring is required to ensure that cardiac output is well preserved ( 85 ). Similarly, administration of selepressin, a vasopressin derivative, was not found to be beneficial in a study where cardiac output was not monitored ( 86 ). Angiotensin II has been reintroduced as a vasopressor ( 87 ), but its indications are not well defined.
其他缩血管药物的地位仍未明确。这些药物的风险在于降低心输出量。血管加压素已被广泛使用，但没有证据表明其对临床有益。当早期使用血管加压素以防止毛细血管渗漏时，可能会有好处，但风险是它可能会减少血流，特别是对肝脾和冠状动脉循环。因此，需要密切监测血流动力学以确保心输出量维持得很好（85）。同样，在一项研究中，未监测心输出量，给予 selepressin （一种血管加压素衍生物）并未发现有益（86）。血管紧张素 II 已被重新用作升压药（87），但其适应症尚未明确界定。
Although in the past, vasopressor therapy was initiated only when it was considered that the patient was not responding to fluids, more recent studies have indicated that arterial hypotension should be avoided in all cases. Even transient hypotension can be associated with an increase in organ failure ( 88 ) or mortality ( 89 ) and early norepinephrine administration to restore arterial pressure seems to have beneficial effects on outcomes ( 90 ). The optimal arterial pressure target in shock states has been a topic of intense investigation ( 58 , 91 ), but no globally acceptable ideal value has been identified because arterial pressure targets should be personalized taking into account various factors, including, among others, history of chronic hypertension, current disease process, and hemodynamic status ( 92 ).
尽管在过去，只有在认为病人对液体没有反应时才开始使用缩血管治疗，但最近的研究表明，任何情况下都应避免低血压。即使是短暂的低血压也可能导致器官衰竭（88）或死亡率（89）增加，尽早给予去甲肾上腺素恢复血压似乎能改善预后（90）。休克状态下的最佳血压目标一直是一个深入研究的课题（58,91），但是都认可的理想值尚未确定，因为血压目标应该是个性化的，要考虑到各种因素，包括慢性高血压病史、当前疾病过程和血流动力学状态（92）。
Dobutamine has been considered as the inotropic agent of choice in case of myocardial failure. Initially considered as inappropriate for use in septic shock, it has found a place when response to fluids is limited. Since optimization of hemodynamic variables is usually considered as standard of care, conduct of a large RCT to evaluate the potential benefit or harm of dobutamine would be difficult.
多巴酚丁胺被认为是心肌衰竭时使用的正性肌力药物。最初被认为不适合用于脓毒症休克，但当对液体的反应有限时，多巴酚丁胺是可以使用的。由于血流动力学参数的优化通常被认为是标准治疗，因此进行大规模的 RCT 研究来评估多巴酚丁胺的潜在益处或危害是很困难的。
Although their long half-life is not particularly desirable, phosphodiesterase inhibitors (like milrinone) and levosimendan can find a place in the management of cardiogenic shock, but their vasodilating effects have limited their place in the management of septic shock. There is no place for routine administration of any inotropic agent in these patients, even levosimendan ( 93) .
尽管磷酸二酯酶抑制剂（如米力农）和左西孟旦的长半衰期不是特别理想，但在脓毒症休克管理中仍有一席之地，不过它们的血管扩张作用限制了其在脓毒症休克管理中的地位。任何正性肌力药物在这类患者都不作为常规使用，即使是左西孟旦（93）。
# The Future of Hemodynamic Monitoring 血流动力学监测的未来
Medical and scientific technology continues to advance at an extraordinary pace, and this will continue to impact the field of hemodynamic monitoring in shock. New tiny, flexible noninvasive sensors that can be attached to the skin or items of clothing are already available and can provide continuous monitoring of multiple variables ( 94 ). These values can be transmitted wirelessly to central computers or systems or to healthcare workers’ smartphones or smartwatches. Artificial intelligence will increasingly be used to interpret such signals and suggest or even start appropriate therapy. There is already renewed interest in clinical automation with automated closed-loop control systems ( 95 ). The integration of feedback control systems and artificial intelligence into medical device systems has the potential to improve adherence to prescribed treatment regimens and protocols, and enable rapid adaptation to new or changing therapeutic strategies. In the future, it is likely that personalized titration of drugs will be administered by automated systems using data previously gathered from patients with similar demographics and disease patterns. These systems would be able to more accurately predict the response of a given patient to specific drugs and use these predictive models within their treatment protocols, thus facilitating a personalized medicine approach. Echocardiography probes will also become even smaller and even more widely available and used. Although costs remain high at present, these will decrease as such tools become more widespread. However, further study needs to determine how best such innovations can be used in the critically ill to improve outcomes before they become a routine presence on our ICUs.
医学和科学技术继续以惊人的速度发展，这将继续影响休克的血流动力学监测领域。新的微小的、灵活的无创传感器可以附着在皮肤或衣服上，并且可以对多个参数进行连续监测（94）。这些数值可以无线传输到中央电脑或系统，或传输到医护人员的智能手机或智能手表。人工智能将越来越多地被用来解释这些信号，给出建议甚至自动开始进行适当的治疗。人们已经对临床自动化与自动化闭环控制系统重新又产生了兴趣（95）。将反馈控制系统和人工智能整合到医疗设备系统中，有可能改善对制定好的治疗方案和流程的依从性，并能快速适应新的治疗策略或治疗策略的改变。在未来，有可能由自动化系统利用先前从具有类似人口统计学和疾病模式的病人身上收集的数据来进行药物的个性化滴定。这些系统将能够更准确地预测特定病人对特定药物的反应，并在其治疗方案中使用这些预测模型，从而促进个性化医疗方法的实施。超声心动图探头也将变得更小，甚至普及更广泛而且应用范围更广。虽然目前的成本仍然很高，但随着这些工具的普及，成本会降低。然而，在这些工具成为重症监护室的常规工具之前，我们还需要进一步研究，以确定如何在重症患者中更好地使用这些创新工具，以改善治疗效果。
# CONCLUSIONS 结论
Hemodynamic monitoring and management have improved greatly in critical care and perioperative medicine over the past 50 years. Monitoring technology has evolved to enable very invasive devices to be replaced by much less invasive (and even totally noninvasive) equipment—even though we may lose some accuracy. Simultaneously, our whole approach to monitoring has shifted from using a few static, single measures to a functional, dynamic, and multivariable approach. Hemodynamic monitoring in the ICU needs to include more than simply blood pressure, heart rate, and urine output. Furthermore, any variable on its own provides relatively little information of a patient’s hemodynamic status, particularly in the complex critically ill patient with shock. Rather the results from monitoring of several different variables need to be considered together to provide a complete hemodynamic picture for that particular patient at that moment in time ( 15 ). The ability to monitor regional blood flow would be helpful but is not currently feasible clinically. We also have no ideal monitoring system for cell function, and monitoring of the microcirculation is still a work in progress. Yet, these areas could represent important targets for successful resuscitation in the future. Finally, we are moving from standard, protocolized hemodynamic strategies to a more personalized approach to ensure appropriate management of each patient according to his/her specific requirements during their disease trajectory ( 92 ).
过去 50 年，血流动力学监测和管理在重症医学和围术期医学领域突飞猛进。监测技术的发展使侵入性很强的设备被微创（甚至完全无创）设备所取代 - 尽管准确性稍有下降。同时，我们的整个监测方法已经从使用少数静态、单一的方法转变为功能性的、动态的和多参数的方法。ICU 血流动力学监测需要包括更多内容，而不仅仅是血压、心率和尿量。此外，任何参数本身提供的病人血流动力学状态的信息都相对较少，特别是对于复杂的休克重症病人。相反，需要将几种不同参数的监测结果一起考虑，以提供该特定病人在那一刻的完整血流动力学情况（15）。有能力监测局部血流会很有用，但目前在临床上还不可行。我们也没有理想的细胞功能监测系统，对微循环的监测仍处于研究当中。然而，这些领域可能是未来成功复苏的重要目标。最后，我们正在从标准的、流程化的血流动力学策略向更加个体化的方法转变，从而确保根据每个病人病程中的特定要求对其进行适当的管理（92）。