Common dialyzable drugs & questions 1-2

This table lists the drugs that are commonly considered dialyzable. And therefore we will supplement an appropriate dose after dialysis after several sessions, for example three to four dialysis sessions. In the following few slides, I would like to work with you on the problem relating to dialysis clearance and the dialyzability step-by-step. So that it would gain an understanding of the calculation. And perhaps more importantly to know how the experiment is designed in order to obtain the information. So here is the problem. According to the manufacturers, Braun’s dialysis machine has an extraction ratio of 0.2 for phenobarbital. So what would be the dialysis for phenobarbital? If the pump speed was 300 milliliters per minutes.

And the following I have three or four questions there, so I’m moving on to the next slide and then we are gonna work on each problem step by step. So calculation number one. Repeating the question again. According to the manufacturer, Braun’s dialysis machine as an extraction ratio of 0.2. What will be the dialysis for phenobarbital? And here is the equation that you use. That defines dialysis clearance as Q, which is the blood flow, times CA minus CV divided by CA. The arterial concentration minus the venous concentration divided by the arterial concentration. Since the blood flow is 300 milliliters per minutes and the CA minus CV divided by the CA is the so called extraction ratio.

So 300 milliliters per minutes times the extraction ratio which is point two. And that gives you 60 milliliters per minute. So that is that the dialysis clearance. Calculation number two. If an instantaneous dialysate was collected at a corresponding arterial blood level of 30 microgram per milliliter, then what would be the phenobarbital concentration in that instantaneous dialysate. If the dialysate flow was five hundred milliliters per minute. And again let’s look at the formula. Dialysis clearance is equal to dialysate flow times dialysate concentration divided by the corresponding arterial concentration. Now, the dialysis clearance calculated based on the A-V difference is 60 milliliters per minute. The dialysis flow is 500 and the arterial concentration is 30.

So here we resolve for the dialysate concentration which turned out to be three point six microgram per mililiter.