13.23: Extracorporeal Removal of Drugs: Hemoperfusion and Hemofiltration

Hemoperfusion and hemofiltration are critical techniques in medical treatments to eliminate accumulated drugs, metabolites, and electrolytes from the bloodstream. These methods are particularly vital in cases of accidental poisoning and drug overdose.

Hemoperfusion involves passing blood through an adsorbent material to remove unwanted substances. The main adsorbents used in hemoperfusion include activated charcoal and Amberlite resins. Activated charcoal can adsorb both polar and nonpolar drugs, making it a versatile adsorbent. In contrast, Amberlite resins have a high affinity specifically for nonpolar organic molecules. The effectiveness of drug removal via hemoperfusion is influenced by several factors, including the drug–adsorbent affinity, the surface area of the adsorbent, its absorptive capacity, the blood flow rate through the device, and the equilibration rate between the blood and the adsorbent. These factors collectively determine how efficiently drugs can be removed from the bloodstream.

Hemofiltration, on the other hand, offers an alternative approach to dialysis and hemoperfusion. This technique uses a low-pressure blood flow through semi-permeable membranes to filter out fluids, electrolytes, and small-molecular-weight substances. During hemofiltration, replacement fluid is added to the blood before it is returned to the patient, ensuring the maintenance of fluid and electrolyte balance. However, hemofiltration has limited utility in removing widely distributed drugs due to its lower clearance rates. One of the major challenges associated with hemofiltration is the formation of blood clots within the filter fibers, which can obstruct the filtration process and compromise treatment efficacy.

Both hemoperfusion and hemofiltration are valuable tools in the management of drug overdoses and poisonings. Hemoperfusion is particularly effective in rapidly adsorbing a wide range of drugs, while hemofiltration is beneficial for its ability to remove excess fluids and small molecules continuously. Understanding the mechanisms and limitations of these techniques is crucial for optimizing their use in clinical settings.

Hemoperfusion and hemofiltration help eliminate accumulated drugs, metabolites, and electrolytes.

In hemoperfusion, blood passes through an adsorbent material to remove drugs.

Adsorbents usually used include activated charcoal and Amberlite resins. Activated charcoal adsorbs both polar and nonpolar drugs, while resins have a high affinity for nonpolar organic molecules.

Various factors can affect drug removal, including drug–adsorbent affinity, surface area, absorptive capacity, blood flow rate, and equilibration rate.

This method is effective in accidental poisoning and drug overdose.

On the other hand, hemofiltration offers an alternative to hemodialysis and hemoperfusion.

It is a slow and continuous process that uses low-pressure flow through membranes to filter nonprotein-bound small molecules.

Replacement fluid is added to the blood before it is returned to the patient.

Due to its lower clearance rates, hemofiltration has limited utility for widely distributed drugs. It is also prone to blood clot formation within filter fibers, posing a major challenge.