Identifying Frailty Using Point-of-Care Ultrasonography: Image Acquisition and Assessment

Summary

Here, we present a protocol to assess frailty in the perioperative setting using point-of-care ultrasound to measure quadriceps thickness. This method offers a practical, non-invasive alternative to traditional assessment methods, potentially enhancing perioperative care by quickly identifying frail patients.

Abstract

Frailty is a significant predictor of a range of adverse outcomes in surgical patients, including increased mechanical ventilation time, longer hospital stays, unplanned readmissions, stroke, delirium, and death. However, accessible tools for screening in clinical settings are limited. Computed tomography of the psoas muscle is the current standard imaging device for measuring frailty, but it is expensive, time-consuming, and exposes the patient to ionizing radiation. Recently, the use of point-of-care ultrasound (POCUS) has emerged as a potential tool to determine the presence of frailty and has been shown to accurately predict frailty and postoperative outcomes. In this article, we will describe the image acquisition of the quadriceps muscles and explain how they can be used to determine frailty and predict postoperative adverse events. We will present information on probe selection, patient positioning, and troubleshooting. Images from a demonstration will be used to present the POCUS technique and example results. The article will culminate in a discussion of the use of these images in medical decision-making and potential limitations.

Introduction

As the average life expectancy rises globally, an increasing number of surgeries are performed on patients over the age of 65¹. Frailty is more common in these patients compared with their younger counterparts and represents a state of physiological vulnerability to stressors, including surgery^2,3,4. Frailty in the preoperative setting has been linked with a higher risk for postoperative adverse events across many surgical subspecialties^{5,6,7,8,9,10,11,12,13}, including longer hospital length of stay^10,14, loss of independence^15,16, readmission rates^17,18, increased costs¹⁴, and mortality^10,18,19,20. Therefore, it is of utmost importance for the perioperative healthcare team to consider a patient's frailty during preoperative decision-making.

The most commonly used method to diagnose frailty includes the Fried frailty phenotype, which comprises five factors including exhaustion, weakness (measured by grip strength), slow walking pace, weight loss, and low physical activity levels²¹. However, this scale was designed primarily for outpatient services and may be too time-consuming in the perioperative setting. In addition, it requires patient cooperation and is impractical in a patient with altered mental status. Moreover, CT scans are used to assess muscle mass for sarcopenia diagnosis, which can aid in frailty assessment. However, while effective, CT scans present practical challenges in resource allocation and expose patients to ionizing radiation, especially in the perioperative period.²² Therefore, there is a need for bedside test that can quickly and accurately identify preoperative patients with diminished muscle mass, thus flagging those at higher surgical risk.

Recently, Canales et al. reported on a method for screening for frailty in the preoperative setting using point-of-care ultrasound²³. They found that quadriceps muscle thickness accurately predicted frailty and was an independent predictor of postoperative discharge to a skilled nursing facility and delirium. The quadriceps muscle is located on the anterior thigh and is composed of four muscle bellies: the rectus femoris, the vastus medialis, vastus lateralis, and the vastus intermedius²⁴. Using point-of-care ultrasound for frailty screening in the preoperative setting offers advantages over the Fried frailty assessment and CT imaging. Point-of-care ultrasound provides objective measures of physiologic parameters, such as muscle mass and quality, in real-time, allowing for immediate and non-invasive evaluation. This approach is more practical, efficient, and adaptable to patients who may not be able to undergo traditional assessment, enhancing perioperative risk stratification and improving outcomes²³.

This paper will detail how to obtain the point-of-care ultrasound measurements of the quadriceps (including probe selection, patient positioning, and troubleshooting) and discuss the implications of this measurement in the perioperative setting.

Protocol

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

NOTE: The exams can be performed with either a low frequency curvilinear (2-5 MHz) or medium to high frequency linear probe (6-12 MHz) depending on patient body habitus, probe availability, and provider preference. For the figures and scans, a curvilinear probe (C35xp, SonoSite M-Turbo) was utilized.

1. Technique for quadriceps scanning

1. Quadriceps depth measurement
   1. Patient positioning: Place the patient in a supine position (head of the bed elevated to 30^o) with their legs extended.
   2. Probe selection: Select a low-frequency curvilinear or medium to high-frequency linear probe.
   3. Mode selection: Set the preset (i.e., exam type) on the scanner to musculoskeletal (MSK) setting.
   4. Probe placement:
      1. Place the probe transversely on the anterior thigh at approximately 60% the length from the anterior superior iliac spine (ASIS) to the superior border of the patella (Figure 1).
      2. With the probe perpendicular to the long axis of the muscles, the quadriceps will appear deep to the subcutaneous tissue and superficial to the femur.
      3. Use extra contact gel to minimize underlying soft tissue distortion.
   5. Image optimization:
      1. To prevent the overestimation of the muscle thickness due to superficial edema, apply firm pressure to the ultrasound probe without inflicting pain²⁵.
      2. If any difficulty identifying the rectus femoris is encountered, ask the patient to contract their thigh muscles or extend their knee. The rectus femoris, being superficial and crossing the hip joint, will show a different movement pattern compared to the deeper vastus muscles (Supplementary Video 1).
   6. Measurement of quadriceps muscle thickness
      1. Activate the Caliper function of the ultrasound machine by pressing Measure on the ultrasound machine.
      2. Use the cursor to measure the anterior-to-posterior distance between (1) the deep border of the vastus intermedius (just superficial to the cortex of the femur) and (2) the most superficial fascia of the rectus femoris (Figure 2).
         NOTE: If there is any difficulty identifying the structures mentioned in 1.1.6.2, the steps mentioned in the Video 1 supplement can be repeated before activating the caliper function. The quadriceps muscle thickness is the sum of the muscle thickness of the rectus femoris and vastus intermedius (Figure 3).
   7. Image acquisition: click on Acquire to save a video clip of this sonographic view.
   8. Repeat measurement (steps 1.1.6-1.1.7) three times and average values to minimize variability.

2. Technique for rectus femoris scanning

1. Rectus femoris cross-sectional area (CSA) measurement
   1. Patient positioning: follow step 1.1.1.
   2. Probe selection: follow step 1.1.2.
   3. Mode selection: follow step 1.1.3.
   4. Probe placement: follow step 1.1.4.
   5. Image optimization:
      1. Adjust the depth using the vertical ruler on the right side of the displayed scan. Adjust the gain using the horizontal slide bar at the bottom of the touch control panel so that the rectus femoris muscle is centered in the ultrasound frame with clear visualization of its boundaries and the underlying femur.
      2. Identify the rectus femoris muscle as a hypoechoic structure within the anterior thigh compartment, with a central echogenic line representing the intramuscular tendon.
      3. Activate the caliper function on the ultrasound machine and trace around the periphery of the rectus femoris muscle carefully to define its cross-sectional area. The ultrasound machine will calculate and display the CSA based on the tracing.
   6. Image acquisition: follow step 1.1.6.
   7. Repeat measurement three times and average values to minimize variability.
2. Rectus Femoris Circumference Measurement
   1. Patient positioning: follow step 1.1.1.
   2. Probe selection: follow step 1.1.2.
   3. Mode selection: follow step 1.1.3.
   4. Probe placement: follow step 1.1.4
   5. Image optimization:
      1. Adjust the depth using the vertical ruler on the right side of the displayed scan. Adjust the gain using the horizontal slide bar at the bottom of the touch control panel so that the rectus femoris muscle is centered in the ultrasound frame with clear visualization of its boundaries and the underlying femur.
      2. Identify the rectus femoris muscle as a hypoechoic structure within the anterior thigh compartment, with a central echogenic line representing the intramuscular tendon.
      3. Activate the caliper function on the ultrasound machine and trace around the periphery of the rectus femoris muscle carefully to define its cross-sectional area. The ultrasound machine will calculate and display the circumference based on the tracing (Figure 4).
   6. Image acquisition: follow step 1.1.6.
   7. Repeat measurement three times and average values to minimize variability.

Results

By implementing this protocol for measuring quadriceps muscle thickness using real-time ultrasound, it is possible to accurately assess frailty indicators. Following the steps outlined in this protocol, we positioned the patient and selected the appropriate ultrasound probe for optimal visualization of the quadriceps muscles.

The key to success in this technique is the precise placement of the probe on the anterior thigh at approximately 60% the length from the ASIS to the superior border of t...

Discussion

Previous studies have indicated that POCUS can be used to estimate muscle thickness, including the quadriceps muscle, with accuracy comparable to CT scans^26,27,28. Sonographic measurement of quadriceps muscle thickness has been correlated with frailty and can be used to predict certain postoperative outcomes²³. In addition, this method is helpful in situations where other methods of diagnosing frailty may...

Materials

Name	Company	Catalog Number	Comments
High Frequency Ultrasound Probe (HFL38xp)	SonoSite (FujiFilm)	P16038
Low Frequency Ultrasound Probe (C35xp)	SonoSite (FujiFilm)	P19617
SonoSite X-porte Ultrasound	SonoSite (FujiFilm)	P19220
Ultrasound Gel	AquaSonic	PLI 01-08