Abstract
To estimate the flow volume in an arteriovenous dialysis shunt (A-V shunt) and its effect on cardiac function, we investigated the A-V shunts of 12 chronic dialysis patients (8 men, 4 women; mean age 51.8 years) by using an ultrasonic pulse doppler flowmeter. Also, cardiac output was estimated with an M mode ultrasonic cardioscope (Teicholtz method) and by the RI method (first pass method). The flow rate for each vessel was measured by calculating the product of the mean time velocity integral (which is half of the maximum time velocity integral) and the sectional area. The shunt flow rate was measured by calculating the difference between the right brachial artery flow rate and the left brachial artery flow rate.
The mean shunt flow rate was 521ml/min (maximum; 1, 096ml/min, minimum; 150ml/min), and the ratio of the shunt flow rate to cardiac output was 11.3% (maximum; 25.1%, minimum; 2.6%) by the Teicholtz method and 11.7% (maximum; 27.1%, minimum; 2.5%) by the first pass method.
All but one patient had an adequate A-V shunt flow rate (more than 200ml/min), and underwent dialysis with no problem. Therefore dialysis A-V shunt requires at least 200ml/min.
The color doppler method enabled us to estimate the type of flow. Surface vessels near the A-V shunt showed a mozaic pattern, which meant turbulent flow formation.
The measurement of shunt flow by the pulse doppler method is simple and easy. However there exist some problems: 1. The probe should be positioned as parallel to the vessels as possible. 2. The vessel should not be pressed by the probe. 3. This method should be used only for the vessels which have laminal flow, not turbulent flow. Therefore the precise shunt flow rate is not obtained by measuring the flow rate of a surface vessel near the A-V shunt whose flow is turbulent, but by the difference between the right brachial artery flow rate and the left brachial artery flow rate.
