Bedside Ultrasound for Guiding Fluid Removal in Patients with Pulmonary Edema: The Reverse-FALLS Protocol

Summary

We describe an imaging protocol that enables the clinician to visualize, in real-time, the patient's intravascular and extravascular space volumes and set diuresis and fluid removal parameters accordingly for the safe and efficient treatment of pulmonary edema.

Abstract

Fluid retention is the most common risk factor for mortality and cardiovascular complications in patients with volume-overloaded disease states. The extent of diuresis or fluid removal is frequently determined by physical examination which is subject to inaccuracies.

Bedside ultrasound (US) is a portable tool that brings real-time diagnostic imaging to the patient's bedside. This versatile modality makes it possible for the clinician to investigate patients' extravascular and intravascular volume states. The extravascular volume, particularly in the case of pulmonary edema, can be quantitatively assessed by US of the anterior chest. Intravascular volume is estimated by visualizing the inferior vena cava (IVC) caliber. Taken together, the degree of extravascular lung water and the IVC caliber provide objective data that can guide the clinician to determine the level of diuresis needed to effectively yet safely treat pulmonary edema.

The objective of this article is threefold: 1) to summarize the findings of previous studies on the efficacy of portable US to guide fluid management, 2) to describe a proposed ultrasound protocol to help guide fluid management, and 3) to elucidate techniques that address the measurement of intravascular and extravascular volumes using portable US.

Introduction

Fluid retention is the most common modifiable risk factor for mortality and cardiovascular events in volume overloaded patients¹. Fluid retention leads to poorly controlled hypertension, cardiac dysfunction and pulmonary edema, and has been associated with excess mortality in this population. The clinical estimation of a patient's volume status by combining the patient's symptoms, blood pressure, and weight changes represent a clinical assessment that is prone to imprecision². This article proposes a protocol that utilizes bedside ultrasound (US) techniques to guide the effective management of pulmonary edema. Chest and ....

Protocol

1. Assess Extravascular Compartment Before Diuresis: Chest Ultrasound

1. Use a low-frequency, phased array probe.
2. Select the appropriate machine setting (abdomen or lung) with the screen marker operator-left.
3. Adjust the depth to 8-12 cm.
4. Place the patient in supine or semi-recumbent position and expose the anterior chest. Place the transducer at a 90° angle to the patient's anterior chest with the probe marker facing cephalad.
   1. Perform this protocol at the midclavicular line in two locations on each side of the chest for a total of four locations: in the 2^nd-3^rd or the 3^rd-4

Results

Lung ultrasound estimates the amount of fluid in the extravascular compartment by visualizing A-line or B-line artifacts, as illustrated in Figure 1. The quantity of B-lines on lung ultrasound helps determine the amount of fluid removal required as illustrated in Figure 2. A mixed A-line and B-line pattern, or an A-line predominant pattern suggests lung parenchyma that is relatively free from extra fluid. Mild diuresis may be nec.......

Discussion

Many studies have demonstrated that bedside US is a reliable diagnostic tool that can be used to guide the management of various disease states such as shock and dyspnea⁵. The correlation of B-lines with extravascular lung water has good sensitivity and specificity in evaluating for pulmonary edema, and studies have shown that lung US can reliably detect even modest variations in extravascular lung water^2,10. Similarly, studies have shown .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Portable Ultrasound machine	Shown in video: FUGIFILM/Sonosite	Shown in video:  M- Turbo	Any portable ultrasound machine with the following capabilities •  B- Mode •  M- Mode •  Caliper measurement tool
Transducer	Shown in video: FUGIFILM/Sonosite	Shown in video:  P21	Any ultrasound transducer probe with the following capabilities: •  Phased Array •  Low frequency (1-5MHz)