Elsevier

Journal of Critical Care

Volume 31, Issue 1, February 2016, Pages 96-100
Journal of Critical Care

Cardiovascular/Thoracic
Development of a fluid resuscitation protocol using inferior vena cava and lung ultrasound,☆☆

https://doi.org/10.1016/j.jcrc.2015.09.016Get rights and content

Abstract

Appropriate fluid resuscitation has been a major focus of critical care medicine since its inception. Currently, the most accurate method to guide fluid administration decisions uses “dynamic” measures that estimate the change in cardiac output that would occur in response to a fluid bolus. Unfortunately, their use remains limited due to required technical expertise, costly equipment, or applicability in only a subset of patients. Alternatively, point-of-care ultrasound (POCUS) has become widely used as a tool to help clinicians prescribe fluid therapy. Common POCUS applications that serve as guides to fluid administration rely on assessments of the inferior vena cava to estimate preload and lung ultrasound to identify the early presence of extravascular lung water and avoid fluid overresuscitation. Although application of these POCUS measures has multiple limitations that are commonly misunderstood, current evidence suggests that they can be used in combination to sort patients among 3 fluid management categories: (1) fluid resuscitate, (2) fluid test, and (3) fluid restrict. This article reviews the pertinent literature describing the use of inferior vena cava and lung ultrasound for fluid responsiveness and presents an evidence-informed algorithm using these measures to guide fluid resuscitation decisions in the critically ill.

Introduction

Appropriate fluid administration is a cornerstone in the management of acutely ill patients with shock. Inadequate fluid resuscitation results in tissue hypoperfusion and worsening end-organ dysfunction [1], [2], and resuscitation strategies that avoid underresuscitation have a proven mortality benefit [3], [4]. Yet, overresuscitation leading to a positive fluid balance has been associated with worsened mortality [5], [6]. Establishing measures of adequate fluid resuscitation in critically ill patients with shock has been a major focus of critical care since its inception, with multiple strategies and devices having been adopted and abandoned over time [3], [7], [8], [9], [10]. In the past 2 decades, a growing body of research has established the use of dynamic measures to determine fluid responsiveness (FR) when making fluid administration decisions [11], [12], [13]. A “fluid responder” has been defined as a patient whose cardiac output (CO) increases by 15% in response to a fluid bolus, whereas nonresponders either show decreased CO or minimal increases. Pulse pressure variation, stroke volume variation, and systolic pressure variation are established dynamic measures that estimate changes in CO before and after induced fluid shifts into the heart, by the cyclic changes caused by a mechanical ventilator, passive leg raises, or rapid infusions of small fluid volumes. Using dynamic measures to determine FR is now considered the optimal approach to guide fluid decisions given their superior predictive characteristics, with areas under the receiver operating characteristic curves of 0.84 to 0.94 [14]. However, the dynamic measures are almost all limited by the need for either expert echocardiographers, costly equipment, or physiologic applicability in only a small subset of patients [15]. As a result, point-of-care ultrasound (POCUS) has garnered attention as a viable tool to help clinicians prescribe fluid therapy given its rapid, repeatable, and noninvasive nature [16], [17], [18], [19], [20], [21]. The use of POCUS assessments included within basic critical care echocardiography and general critical care ultrasound to improve assessment of FR is in line with current trends, where whole-body ultrasound for shock or respiratory failure is growing more common [22], [23], [24], [25]. An example of this practice is the adoption of POCUS measured inferior vena cava (IVC) parameters within widely disseminated sepsis resuscitation protocols [26]. Others have promoted the use of lung ultrasound (LUS) to identify the presence of extravascular lung water as a method for avoiding fluid overresuscitation in shock patients [22], [23], [25]. These IVC and LUS assessment skills are being taught and have been integrated into practice by both nonexpert and expert POCUS practitioners [27]. In the following, we (1) explore the physiologic rationale and current literature supporting the use of IVC and LUS in helping to identify the boundaries of fluid underresuscitation and overresuscitation and (2) provide a decision support tool that integrates this literature to provide clinicians with an evidence-informed algorithm to qualitatively guide fluid administration decisions.

Section snippets

Fluid responsiveness and IVC parameters

Considering the complex nature of critically ill patients and the multiple variables that influence FR, insufficient evidence is available to support the use of IVC ultrasound to definitively determine FR in most clinical scenarios; however, several IVC parameters may serve as a guide to fluid administration decisions as described in the following paragraphs.

Lung ultrasound–guided fluid resuscitation

Given that the information available from respirophasic and static IVC measurements in many patients will not always be predictive, supplementary data should be acquired to further guide management. A number of studies have shown a correlation between extravascular lung water and mortality in the critically ill [34], [35]. As such, LUS has been suggested as an additional tool that can rapidly and accurately identify the early pulmonary edema that develops when patients are overresuscitated,

Fluid resuscitation guide

Although the ideal methods to identify FR in critically ill patients with shock are to rely upon dynamic measures, such options are often either not available or applicable in a majority of clinical situations and environments [15]. Even when appropriate, busy clinical teams within emergency departments and intensive care units are not always able to perform repeated dynamic testing in a timely fashion during resuscitation of patients. Thus, use of more widely practiced and readily acquired

Limitations

The included ultrasonographic assessments serve as evidence-based tools to guide fluid management decisions, yet some limitations exist in using such categorical discriminators. The predictive power of some categories will vary depending on the pathophysiologic cause of shock, a limitation most relevant in the “underfilled IVC” category. Inferior vena cava measurements in patients with conditions resulting in absolute hypovolemic states, for example, trauma, diarrhea, gastrointestinal bleeding,

Conclusions

Fluid resuscitation in the critically ill can be categorized in 3 broad management categories when using IVC and LUS measures: fluid resuscitate, fluid test, and fluid restrict. Combining both lung and IVC POCUS is easy to accomplish and provides valuable information for determination of FR. Although not capable of matching the predictive power of more sophisticated dynamic tests of FR, this manuscript and accompanied fluid administration guide present an interim synthesis of existing

Acknowledgments

CWCL, PDK, and RTA each contributed substantially to review of pertinent literature, design of the graphical protocol, and writing of the manuscript.

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      Citation Excerpt :

      In addition, POCUS has utility in the evaluation of fluid responsiveness and to help guide appropriate fluid resuscitation. When combined with LUS, echocardiography (specifically IVC imaging) can aid in fluid resuscitation management in the critically ill, as demonstrated by Lee et al.101 By combining current literature on lung and IVC ultrasound with expert opinion on the ability of transthoracic ultrasound to predict fluid responsiveness, investigators were able to develop a qualitative fluid resuscitation guide that categorized critically ill patients into one of three broad groups: fluid resuscitate, fluid test, and fluid restrict. Validation of this resuscitation guide to help clinicians prescribe fluid therapy still is pending.

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    Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the manuscript.

    ☆☆

    Prior abstract publication/presentation: N/A.

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