Therapeutic plasma exchange in poisoned patients

November 7, 2015, 7:08 pm

★☆☆☆☆

Therapeutic plasma exchange in poisoning: 8 years’ experience of a university hospital. Disel NR et al. Am J Emerg Med 2015 Oct;33:1391-1395.

Abstract

In therapeutic plasma exchange (TPE), blood is removed from the body, and plasma is separated from components such as RBCs, WBCs, and platelets. Those components are re-infused along with a replacement fluid such as fresh-frozen plasma or albumin. This procedure is usually used to removed pathological immunoglobulins in various conditions such as thrombotic thrombocytopenic purpura.

There have been some case reports and small case series on the use of TPE in poisoned patients, but nothing that even comes close to demonstrating that it may be beneficial. Unfortunately, this paper from Çukurova University in Turkey adds nothing to the discussion. The authors retrospectively reviewed 36 adult toxicology cases (from January 2007 to May 2015) in which TPE was used, and claim this is the largest such case series in the literature. I have not reason to doubt them. But we have no idea why TPE was chosen in these cases, or how the patients would have done without the intervention. Poisons involved included organophosphates (25 cases,) carbamazepine, baclofen, acetaminophen, seroquel, and paraquat.There were 12 deaths, including 10 patients exposed to an organophosphate.

As the authors point out, plasma exchange can remove large, highly protein-bound molecules that would not be amenable to hemodialysis. They suggest that it would be effective eliminating substances with protein-binding capacity > 80% and a low volume of distribution (< 0.2 L/kg.)  Yet many of the toxicants in these patients did not at all meet these criteria — for example, carbamazepine has a volume of distribution of 2-3 L/kg.

The authors conclude:

When applicable, TPE may be a promising extracorporeal elimination and treatment technique in poisoned patients when performed in selected cases.

Well, almost anything may be true, and the paper gives no real clue about how to selected appropriate cases. TPE is expensive and comes with risk of infection. I am not at all enthusiastic that this is a promising technique in toxicology cases. The only possible exception might be in neonates and small infants where hemodialysis may be technically difficult.

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