System and method for assessment of cardiac stroke volume and volume responsiveness
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.
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 . 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 . 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 . 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 . 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 . The method of claim 5 , wherein if the patient is in atrial fibrillation, the VTI measurement is averaged over five beats.
7 . The method of claim 1 , wherein the pre-bolus VTI is measured within thirty minutes prior to administering the fluid bolus.
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 . 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 . 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 . 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.