US-12622668-B2 - System and method for assessment of cardiac stroke volume and volume responsiveness

Abstract

Disclosed are systems and methods using ultrasound to predict if a patient's cardiac stroke volume will increase with a fluid bolus. Ultrasound measures are taken before administering a fluid bolus, including measurement of the left ventricular outflow tract velocity time integral (LVOT VTI), and venous measurements of the internal jugular vein. Data collected from such ultrasound scan is then used to predict the patient's cardiac volume response in the event that a fluid bolus is administered to that patient.

Inventors

• Sarah B. Murthi

Assignees

• UNIVERSITY OF MARYLAND, BALTIMORE

Dates

Publication Date

20260512

Application Date

20221213

Claims (11)

1. 1 . A method for predicting cardiac stroke volume responsiveness in a patient, comprising: providing an ultrasound transducer; providing a computer processor in data communication with said ultrasound transducer; receiving at said processor signals from said ultrasound transducer; in response to receiving said signals from said ultrasound transducer, detecting at said computer processor a change in a patient's physiology corresponding to at least one of a change of inflow into a right ventricle of the patient and a change of outflow from a left ventricle of the patient; determining at said computer processor whether said detected change is within a predetermined positive fluid bolus responsiveness value range; and in response to determining that said change is within said predetermined positive fluid bolus responsiveness value range, producing at said computer processor a human-readable output indicating that said patient has a likelihood of positive cardiac stroke volume response to a fluid bolus; and administering a fluid bolus to the patient in response to determining that the detected change is within the predetermined positive fluid bolus responsiveness value range; wherein said detecting a change in a patient's physiology comprises: determining a pre-bolus velocity time integral (VTI) of the patient; and determining a respiratory variation of an internal jugular vein (rvIJ) of the patient; wherein the predetermined positive fluid bolus responsiveness value range is based on a combination of the pre-bolus VTI and the rvIJ; and wherein determining whether said detected change is within the predetermined positive fluid bolus responsiveness value range comprises: comparing the pre-bolus VTI to a first threshold value, wherein a pre-bolus VTI less than or equal to 18 centimeters per second indicates a likelihood of positive cardiac stroke volume response; and comparing the rvIJ to a second threshold value, wherein an rvIJ greater than or equal to 25 percent indicates a likelihood of positive cardiac stroke volume response.
2. 2 . The method of claim 1 , further comprising the steps of: providing a mobile computing device in data communication with said computer processor; and displaying at said mobile computing device said human-readable output.
3. 3 . The method of claim 1 , wherein determining the pre-bolus VTI comprises measuring the VTI through the left ventricular outflow tract (LVOT) using pulsed-wave Doppler ultrasound.
4. 4 . The method of claim 1 , wherein determining whether said detected change is within the predetermined positive fluid bolus responsiveness value range comprises: determining that the patient has a likelihood of positive cardiac stroke volume response only when both: the pre-bolus VTI is ≤18 centimeters per second; and the rvIJ is ≥25 percent.
5. 5 . The method of claim 1 , wherein determining the pre-bolus VTI comprises measuring the VTI through the left ventricular outflow tract (LVOT) from an apical window using pulsed-wave Doppler ultrasound.
6. 6 . The method of claim 5 , wherein if the patient is in atrial fibrillation, the VTI measurement is averaged over five beats.
7. 7 . The method of claim 1 , wherein the pre-bolus VTI is measured within thirty minutes prior to administering the fluid bolus.
8. 8 . The method of claim 1 , wherein determining the respiratory variation of an internal jugular vein comprises: measuring a maximum diameter of the internal jugular vein when the patient is in a supine position; measuring a minimum diameter of the internal jugular vein when the patient is in a supine position; measuring a maximum diameter of the internal jugular vein when the patient is in an upright position; and measuring a minimum diameter of the internal jugular vein when the patient is in an upright position.
9. 9 . The method of claim 1 , wherein the respiratory variation of the internal jugular vein is calculated according to the formula: rvIJ=((IJ max−IJ min)/IJ max)×100 wherein IJ max is the maximum diameter and IJ min is the minimum diameter of the internal jugular vein in the upright position.
10. 10 . The method of claim 1 , wherein determining whether said detected change is within the predetermined positive fluid bolus responsiveness value range comprises determining that the pre-bolus VTI is ≤18 centimeters per second.
11. 11 . The method of claim 1 , wherein determining whether said detected change is within the predetermined positive fluid bolus responsiveness value range comprises determining that the rvIJ is ≥25 percent.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation of U.S. patent application Ser. No. 16/919,469 entitled “SYSTEM AND METHOD FOR ASSESSMENT OF CARDIAC STROKE VOLUME AND VOLUME RESPONSIVENESS,” filed with the U.S. Patent and Trademark Office on Jul. 2, 2020 by the inventor herein, and now U.S. Pat. No. 11,523,796, which application is a divisional of U.S. patent application Ser. No. 15/407,380 entitled “SYSTEM AND METHOD FOR ASSESSMENT OF CARDIAC STROKE VOLUME AND VOLUME RESPONSIVENESS,” filed with the U.S. Patent and Trademark Office on Jan. 17, 2017 by the inventor herein, and now U.S. Pat. No. 10,736,604, which application is based upon and claims the benefit of U.S. Provisional Patent Application Ser. No. 62/278,717 entitled “Combination Assessment of Volume Status (CAVS),” filed with the U.S. Patent and Trademark Office on Jan. 14, 2016 by the inventor herein, and of U.S. Provisional Patent Application Ser. No. 62/443,276 entitled “Method for Estimation of Cardiac Stroke Volume (eSV) and Cardiac Output (eCO),” filed with the U.S. Patent and Trademark Office on Jan. 6, 2017, the specifications of which are incorporated herein by reference in their entireties. STATEMENT OF GOVERNMENT SUPPORT This invention was made with government support under Grant No. FA8650-13-2-6D10 awarded by the Air Force Office of Scientific Research. The Government has certain rights in the invention. FIELD OF THE INVENTION The present invention relates generally to clinical medical treatment of critically ill patients, and more particularly to systems and methods for assessing cardiac stroke volume in a patient, and to methods for predicting a patient's stroke volume response to a fluid bolus. BACKGROUND OF THE INVENTION Early and aggressive fluid resuscitation in patients suffering from shock is associated with improvement in outcome, including mortality. Multiple studies have supported this concept in a variety of clinical settings, from septic shock to high-risk surgical patients. However, a clear association also exists between cumulative fluid balance and mortality. It therefore becomes prudent to adopt a tailored approach to fluid resuscitation over empiric fluid loading. After all, a fluid bolus that does not lead to increased stroke volume is unlikely to benefit the patient, and carries all of the risk associated with volume overload. Multiple methods, invasive or otherwise, have been proposed to predict an increase in cardiac stroke volume (referred to herein at times as SV) with a fluid bolus, or which increase in stroke volume is referred to as volume responsiveness (referred to herein at times as VR). Stroke volume (measured in ml/beat) is the amount of blood pumped out of the heart with each beat (and more specifically a cone of blood that comes through the left ventricular outflow tract (LVOT)). Stroke volume is also an important determinant of fluid status, and thus can be helpful in directing the administration of fluid boluses. While central venous pressure (CVP) has traditionally been used to assess volume status, studies have not demonstrated a reliable relationship between CVP and volume responsiveness. Pulmonary artery catheters (PAC) have also fallen out of favor due to their invasiveness and potential for serious complications. Several studies have failed to show any improvement in outcome associated with PAC use. Given its non-invasive nature, portability, and ease of use as a point-of-care test, ultrasound (US) has emerged as an attractive option to assess volume status and predict fluid responsiveness. The most studied ultrasound measure is respiratory variation in the inferior vena cava (rvIVC). This measure is relatively easy to perform with any point-of-care ultrasound system. While multiple studies have demonstrated that rvIVC accurately predicts volume responsiveness in mechanically ventilated patients, there is conflicting evidence in spontaneously breathing patients. rvIVC measurement may be difficult or impossible to perform in many surgical patients, and particularly those presenting with abdominal distension, surgical wounds, morbid obesity, or bowel gas. Additionally, evidence suggests that in the setting of increased thoracic and abdominal pressures, IVC diameter and collapsibility indices may lose their reliability. Given the varied and limited successes of prior known methods, which generally assess only one metric, it would be advantageous to provide more easily implemented system that allows several ultrasound metrics to be included in the measurements and predictions. This would allow healthcare providers to administer fluid only to those patients most likely to have a positive response, who have a low stroke volume to begin with and limiting application to those least likely to have a positive response (and thereby reducing the risk of volume overload in such patients). It would also be advantageous to provide systems and methods of using noninvasive ultrasound