Early and accurate detection of fluid overload are critically important in acute illness, as the impact of therapeutic intervention can result in decrease or increase mortality rates. The bioelectrical impedance vector analysis is an alternative impedance approach and a method used to estimate fluid status, independent of multiple regression prediction equations generated in limited and specific samples. The determination of fluid volume status is necessary to help clinicians in controlling body fluids, management intravenous fluid administration, and maintaining hemodynamic stability, thus allowing patients to receive early treatment.
This method applies to all chronic patients with fluid overload, such as heart, renal, or hepatic failure. Demonstrating the procedure will be Yunuen Reyes Paz, a postgraduate student from my laboratory. To begin, clean the equipment using a chlorhexidine wipe, and then wash your hands.
If the screen of the equipment shows the legend change the battery, then replace the battery. If the patient is conscious, explain the procedure to them. Obtain the age and accurate measurement of the patient's height in centimeters and introduce these data into the equipment.
Remove the shoe and sock from the right foot, as well as any metal objects such as watch or bracelets worn by the patient. Place the patient in a supine position for five minutes with legs and arms spread out at a 45 degree angle before taking the measurements, verifying they're not in contact with any other part of their body. Clean the surfaces where the electrodes will be placed with a 70%alcohol pad twice.
Draw an imaginary line, straight between the protruding bones on the wrist, and place two electrodes on the right hand dorsally, with each electrode in the center of that line. Place two electrodes on the right foot, one behind the third metatarsal phalangeal joint and the tarsal joint on the ankle, between the medial and lateral malleoli. To place the electrodes, follow the bones underneath.
Connect the lead wires to the equipment with the red alligator clip nearest to the nails and the black clip nearest to the ankle or wrist. Ensure that the wires do not cross between them. Ensure that the patient is not talking or moving during the measurements, as this will affect the results.
The patient's ID will come up on the screen. Scroll through and change the patient's parameters as described in the text manuscript. Ensure that the electrodes are stuck down correctly and press Enter.
The window will indicate measuring on the screen. It takes about six to 10 seconds to measure and a beep will then sound when the measurement is complete. The equipment will display the raw impedance value at four different frequencies.
Five, 50, 100 and 200 kilohertz, as well as the resistance and reactance at 50 kilohertz which are the values needed to classify a patient with fluid overload. Download the software named BIVA Tolerance RXc Graph and open it. Observe that the software is in a workbook in a spreadsheet program with seven worksheets.
Guide, Reference populations, Point graph, Path, Subjects, Z-score, and Z-graph. Right-click on the Reference population sheet. Choose the line of the selected reference population and copy-paste it into the second row.
Right-click on the Subjects sheet, and in the second row, insert the subject ID assigned to the patient. In the second column named Seq, always put the number one, and optionally fill out the surname and name columns. In the sex column, enter F for female and M for male patients.
In the next two columns, input resistance and reactance at 50 kilohertz each. In the next two columns, insert the height in centimeters and weight in kilograms. In the population code column, insert the number that appears in the first column of the Reference population sheet.
In group code, randomly choose a number between one and 10 and insert the patient's age in the next column. In the spreadsheet program menu, go to the complements tab, and right-click on the calculate option to obtain the values of resistance and reactance adjusted by height and phase angle. Right-click on the Point graph sheet and observe that 50, 75 and 95%tolerance ellipses are drawn for the selected reference population.
In the dialogue box, select groups. Right-click on the number placed in the group code located on the subject's sheet, and right-click on OK.Next, the BIVA graph will appear and the subject vector as a geometric figure. Patients with vectors that fall outside the lower pole of the 75%tolerance ellipse will be classified as fluid overload.
Divide Z at 200 kilohertz by Z at five kilohertz, which reflects the total body water and extracellular water compartment, respectively. To obtain the impedance ratio, a value equal to or greater than 0.85 indicates fluid overload. The plot indicated with a triangle symbol denotes a 77 year old female with normal fluid status.
The bioimpedance results showed a resistance of 586.7 and reactance of 62.1. Meanwhile, the square symbol denotes a 62 year old female with fluid overload. The bioimpedance results showed resistance of 332.6 and reactance of 33.6.
The patient must be in a supine position without any metallic contact. The extremity should be abducted to a body skin contact and surfaces where the electrodes are placed, with an alcohol pad should be thoroughly cleaned. The bioelectrical vector analysis and impedance ratio have proved to be useful tools in detecting the presence of fluid overload and have also shown to predict mortality risk.
