The use of hemoperfusion in children. Past, present, and future

Specific removal of paraquat by hemoperfusion through antiparaquat conjugated agarose-polyacrolein microsphere beads

A novel specific adsorbent for removal of paraquat from blood has been developed. Immobilized antiparaquat antibodies provide the specificity and high affinity of the adsorbent. The antibodies were raised in rabbits and goats immunized with an analogue of paraquat, conjugated to bovine serum albumin (BSA). Specific antiparaquat antibodies were isolated from the animals' sera by affinity chromatography. The antibodies were polyvalently bound to crosslinked agarose-polyacrolein microsphere beads (APAMB). Antiparaquat conjugated beads (APB) were used as packing material in a hemoperfusion column for detoxification of paraquat and were compared to activated charcoal. In vitro and in vivo experiments showed specific and enhanced rate of removal of paraquat from plasma and blood by using APB. Minimal alteration of the formed elements and plasma constituents of the blood was observed.

Specific hemoperfusion through agarose acrobeads

Agarose acrobeads were produced by encapsulating polyacrolein microspheres (acrobeads) of 0.2 micron average diameter within an agarose matrix. Crosslinked agarose acrobeads of diameters ranging from 0.5 to 0.8 mm were found to be optimal spheres for specific hemoperfusion purposes. Agarose provides the biocompatibility and mechanical strength of the agarose acrobeads. Acrobeads contain a high aldehyde-group content through which various amino ligands, i.e., proteins, antigens, antibodies, enzymes, and so on, can be covalently bound in a single step under physiological pH (or other pH). Thus, antibodies, antigens, or toxic materials may be directly removed from whole blood by hemoperfusion. During in vitro and in vivo hemoperfusion trials, the content of erythrocytes, leukocytes, and thrombocytes was essentially unaltered. Likewise, a battery of the soluble blood components (Cl-, K+, Na+, Ca2+, PO3/4-), total proteins, albumin, and C'4 component of the complement cascade, as well as the enzymes SGOT, LDH, and alkaline phosphatase, remained constant within narrow limits during the hemoperfusion procedure. The chemical and physical structure of the beads is stable; neither acrolein nor bead fragments were detected in hemoperfusion trials. Similarly, leakage of antibody bound to the agarose acrobeads into the blood is insignificant. Thus far, we have demonstrated the efficacy of the crosslinked agarose acrobeads for extracorporeal removal of "unwanted" substances from whole blood in the following systems: (a) removal of specific antigens (digoxin or paraquat removal with antidigoxin or antiparaquat antibodies bound to the acrobeads, respectively), (b) removal of specific antibody (antiBSA) removal with BSA bound to the beads), (c) removal of immune complexes (BSA-antiBSA complex removal with C1q bound to acrobeads), and (d) removal of specific metals (removal of iron with deferoxamine bound to the agarose acrobeads).

Therapy of digoxin intoxication in dogs by specific hemoperfusion through agarose polyacrolein microsphere beads-antidigoxin antibodies

The usefulness of a new biocompatible, specific immunosorbent, Agarose-Polyacrolein Microsphere Beads--Antidigoxin antibodies (APAMB-AD) for hemoperfusive removal of digoxin in digoxin intoxicated dogs is described. The sorbent contains antidigoxin antibodies covalently bound to polyacrolein microspheres, 0.2 micron in diameter. Thousands of microspheres are matrix-encapsulated in cross-linked agarose to form beads 500 to 800 micron in diameter. The sorbent removes digoxin specifically, leaving other components of the blood intact, in contrast to the nonspecific sorbents (charcoal and ion exchange resins) currently in use. Digoxin-intoxicated dogs looked ill, vomited, and their ECGs showed malignant arrhythmias which were reversed during the first hour of hemoperfusion. By 2 hours of hemoperfusion, the ECG tracings returned to the preintoxication state. Up to 27% of the total body digoxin burden was removed. The sorbent is biocompatible. Neither the formed elements nor a battery of the routinely assayed soluble components of the blood or complement (C'4) were altered significantly during the hemoperfusion trials. The dogs tolerated the hemoperfusion well and all survived the intoxication. Nonhemoperfused dogs or dogs whose blood was hemoperfused through beads lacking antidigoxin did not survive the digoxin intoxication.

Iron detoxification by haemoperfusion through deferoxamine-conjugated agarose-polyacrolein microsphere beads

The natural iron chelator deferoxamine was bonded to agarose-polyacrolein microsphere beads (APAMB). This novel deferoxamine-conjugated APAMB (DCA), when used as the sorbent in a plasma/haemoperfusion system, showed specific and rapid removal of iron from plasma and blood in vitro; in vivo experiments also showed specific iron removal. The advantages of this sorbent are minimal damage to biocompounds during haemoperfusion, high capacity and specificity to iron, and the possibility of reuse.

Hemoperfusion in a child who ingested diquat and died from pontine infarction and hemorrhage

A 2 1/2 year old boy accidentally ingested the herbicide diquat. Progressive neurologic dysfunction preceded his death 143 hours after poisoning. Brain stem infarction and purpura were noted at post mortem and closely resembled the brain stem pathology in 3 of 7 adults who died after diquat ingestion. Renal, gastrointestinal and pulmonary involvement in this child also resembled that seen in adults after ingestion of diquat. Hemoperfusion was performed six times in an effort to lower the body diquat burden. Cellulose-coated, activated charcoal was first employed 40 hours postingestion and removed diquat from serum with clearances of 104 and 39 ml/minute at the initiation of hemoperfusion and 6 hours later, respectively. Serum diquat concentrations decreased rapidly during charcoal hemoperfusion. However, marked rebound in serum diquat concentrations were noted between charcoal treatments, indicating extensive sequestration of diquat by tissues. Thrombocytopenia and hypocalcemia, the major complications of charcoal hemoperfusion, were easily treated. Unlike charcoal, Amberlite XAD-4 resin hemoperfusion did not remove diquat from serum. Charcoal hemoperfusion may temporarily reduce serum diquat concentrations. Whether the early institution and daily performance of charcoal hemoperfusion will minimize diquat-induced damage to brain and other organs is not clear from this case and will only be determined in future studies.