Within the Simple Intensive Care Studies research structure, we use repeated physical examination and ultrasonography to assess hemodynamic function in the critically ill. The main advantages of this protocol is that it's noninvasive and fast, and it can be performed by trained novices. Although this research method can be used to get inside into tissue perfusion, the Simple Intensive Care research structure can be used to answer other research questions in other departments or other hospitals.
Generally, researchers new to this method may struggle. Obtaining the images requires practice, although imaging becomes easier with time and training. The demonstrator of this protocol will be PhD candidate Bart Hiemstra, who is also coordinator of SICS-I and the patient will be Hidde Pelsma, one of our Master's students and a junior researcher.
Before starting the examination, put on a plastic apron and non-sterile gloves after disinfecting the hands and wrists with 70%alcohol, according to standard hospital procedures. If the patient is conscious and adequate, make an introduction and ask the patient for permission to conduct the examination. After explaining what is to be performed, register all of the vital signs and the appropriate ventilator settings according to the protocol from the available bedside monitors.
To determine the subjective skin temperature, palpate the extremities with the hands to estimate whether the patient is cold or warm. To evaluate the peripheral circulation, assess the reperfusion of the knee and sternum by pressing on the skin for ten seconds and letting go and counting the number of seconds until full reperfusion and by measuring the peripheral temperature. For critical care ultrasonography of the heart and lungs, expose the chest and place new electrocardiogram, or ECG, stickers on the skin as necessary, before connecting the stickers to the ultrasound machine, and waiting for the signal to stabilize.
Next, place a sufficient volume of ultrasound gel on the cardiac ultrasound transducer and place the transducer on the lateral left of the sternum between the third and fifth intercostal spaces to obtain a parasternal lung access view in the 2D mode. Adjust the depth as necessary to record images for the left ventricular outflow tract measurements and save the image. To obtain the apical 4-chamber view, adjust the depth to 15 to 20 centimeters, place the transducer over the apex of the heart, caudal to the left areola with the probe light facing the left axillary.
Save the image and roll the trackball so that the cursor is on the boundary between the tricuspid valve and the right ventricle wall, to obtain the tricuspid annular plane systolic excursion. Press the M mode button to obtain the correct image and save the image when defined sinus waves are observed. Move the cursor over the tricuspid valve and decrease the width of the image to increase the number of frames per second.
Press the tissue velocity imaging button followed by the pulsed wave button to obtain the correct image for the right ventricular systolic excursion and save the image. From the apical 4-chamber view, tilt the transducer downward to obtain the apical 5-chamber view and locate the aortic valve and left ventricular outflow tract on the screen. Then save the image and place the cursor right above the aortic valve.
To obtain the left ventricular outflow tract pulse wave doppler image, place the cursor at exactly the same place where the left ventricular outflow tract diameter was measured, press the pulse wave button and save the image. For pulmonary ultrasound, change the settings of the phased array cardiac transducer to a frequency of 3.6 MHz and an image depth of 15 centimeters and use the light of the transducer at 12 o'clock for correct placement of the transducer at each position according to the blue protocol. Then count and register, if there are any, the number of vertical hyperechoic reverberation artefacts, or B-lines, that are observed.
For critical care ultrasonography of the inferior vena cava and the kidney, click the probe button and use the trackball to change the active probe to the convex curvilinear array abdominal transducer. Using the 2D mode with a depth of 10 to 20 centimeters and a frequency of 2.5 to 5 MHz, place the transducer just below the xiphoid process and displace the probe approximately two centimeters to the patient's right. The inferior vena cava should become visible, save the image.
Place the cursor just above the superior wall of the inferior vena cava and outside of the lomaen, and press the M mode button, then save the image. Using similar settings, place the transducer dorsal and caudal of the rib cage and locate the selected kidney central in the image and save it. Press the color button to get a color doppler image of the kidney, and determine the flow in the renal vasculature.
Place the cursor over any artery at the corticomedullary junction in the center of the kidney where doppler flow is clearly visible and adjust the cursor angle before pressing the pulsed wave button. Adjust the signal amplitude and the contrast in active mode if necessary and save the image. Then determine if there is also sufficient vena signal for later measurements and save the image.
When all of the imaging is complete, disconnect all of the cables, remove the excess gel and ECG stickers off of the patient and the transducer, then recover the patient. Then clean the ultrasound machine and used transducers with ultrasound approved disinfecting wipes. All images should comply with predefined criteria to ensure quality.
For the left ventricular outflow tract measurement, open the appropriate file in the ultrasound software and pause the image when the valves are fully open. Click measure and select cardiac dimension left ventricular outflow tract to start the measurement. When the cursor appears, select two points at the base of the aortic valve on each side of the lomaen from inner edge to inner edge, during early systole and save the image.
For the cardiac output measurement, select the pulse wave image from the apical 5-chamber view and adjust the horizontal sweep to 100 centimeters per second. Select three well-shaped hollow waves with clear borders that align with the electrocardiogram and click measure using the trackball to select cardiac aortic left ventricular output trace. Then trace the waveform line, starting and ending at the baseline.
The ultrasound machine will automatically calculate the cardiac output. For the tricuspid annular plane systolic excursion measurement, open the appropriate M mode file and place the cursor first on the lowest point of a well-defined sinus wave and then on the highest point. The difference between the two excursions should appear on the top left corner of the screen.
For the right ventricular systolic excursion measurement, click caliper and place the cursor on the highest peak of a well-defined curve. To determine the inferior vena cava diameter and collapsibility, select the abdominal transducer and open the appropriate 2D image. To measure the inferior vena cava expiratory and inspiratory diameters, open the appropriate M mode image and click caliper and measure the diameter during end and expiration before saving the image.
To measure the kidney length in centimeters, open the appropriate 2D image and click caliper to draw a line spanning from the caudal to the cranial ends of the renal cortex and register kidney length. To measure the renal resistance index, select the appropriate arterial doppler flow image and place the cursor first on the peak and then on the lowest point of the pulsidal flow wave in the positive half of the y-axis. If this signal is not visible in the previous image, open the other venous doppler flow image, then click caliper and place the cursor first over the peak at the maximum flow velocity, and then over the flow velocity at the nadir.
These measurements are used to calculate venous impedance index. When performing these methods repeatedly in critically ill patients, changes in hemodynamic function may be observed. These images were obtained from a middle-aged female patient using critical care ultrasonography.
They show an increase in cardiac output. Performing a structured physical examination and whole body ultrasound allows for a proper investigation of hemodynamic problems in critically ill patients. It's important to continuously inform the patient what you are doing, even if he or she is sedated, to monitor vital signs and to give access to caregivers if necessary.
Following this procedure, other methods, like liver or spleen ultrasonography, can be performed to answer additional questions about organ perfusion. Don't forget that in working with critically ill patients, isolation restrictions may be in place and therefore, the hygiene of the researcher and the ultrasound machine is very important. Using this method structurally, with a team of enthusiastic researchers, can help answer key questions considering hemodynamic instability and ultrasonography.
