Dialyzer reactions can be classified into two types: “Type A” and “Type B”.Simplistically stated, one is serious and the other one isn’t. A good pneumonic I recently learned from Dr. Daniel Coyne of Washington University-St. Louis at a Boards Review course is that “Type A” (the serious one) can be remembered as “anaphylactic”, while “Type B” (the less serious one) can be remembered as “boring”.
Type A reactions occur very shortly after dialysis is initiated–typically within the first few minutes or so–and are thought to be due to pre-formed IgE antibodies causing mast cell degranulation and an aphylactic-type reaction. Symptoms include hypotension, chest pain, dyspnea, and (my favorite) a “sense of impending doom.” An outbreak of Type A reactions was previously associated with ethlyene oxide, once used in the dialyzer sterilization procedure, but can presumably be due to other leachable compounds within dialysis cartridges. Treatment of the Type A reaction involves immediately stopping the dialysis procedure (which ideally involves clamping off the dialysis tubing to prevent any more of the patient’s blood trapped in the extracorporeal circuit from re-entering the body), administering medications such as epinephrine, steroids, and antihistamines, and standard supportive care which may require pressors or bronchodilators.
Type B reactions in contrast tend to occur in a more delayed fashion–say, after 15-30 minutes into dialysis–and symptoms include chest/back pain, nausea/vomiting, and more mild hypotension. The mechanism here is thought to be complement-mediated. It was apparently more common with cellulose-based membranes and is less commonly a problem with the more modern synthetic membranes. Since symptoms are generally mild and can improve with time, the dialysis treatment can usually continue.
1. Prior to initiating hemodialysis, flush (prime) the entire extracorporeal circuit with about 500 cc of saline (including the arterial line).
2. Recirculate at a blood flow rate of 300 to 400 mL/min for several minutes.
3. Flush the entire extracorporeal circuit again with 500cc of saline.
That last step is one which is not followed all the time, resulting in infusing the recirculated saline prime (and all sorts of nasty stuff) into the patient.