Hemodilution:An Overview of Its Concept, Origin, Methods, Common Drugs, and Considerations

Hemodilution, a medical technique designed to reduce the concentration of red blood cells in the blood, has emerged as a significant strategy in managing various health conditions, particularly those related to cardiovascular health and surgical interventions. This practice, rooted in both ancient and modern medical philosophies, involves the dilution of blood to improve flow and oxygen delivery to tissues. Its origins can be traced back to the early understanding of blood’s role in health and disease, with contemporary applications honed by advancements in medical science and pharmacology.

Hemodilution: An Overview of Its Concept, Origin, Methods, Common Drugs, and Considerations
Hemodilution: An Overview of Its Concept, Origin, Methods, Common Drugs, and Considerations

Concept and Origin

Hemodilution therapy is commonly used to treat diseases such as acute ischemic cerebrovascular disease(stroke), acute myocardial infarction, myocardial ischemia, acute pulmonary embolism, primary or secondary polycythemia, etc.
The concept of hemodilution is predicated on the principle that by reducing the hematocrit (the proportion of blood volume occupied by red blood cells), blood viscosity decreases, thereby enhancing microcirculatory blood flow.

This improvement in blood flow is crucial in conditions where restricted blood supply can lead to tissue damage or exacerbate disease processes. The origins of hemodilution can be traced to ancient practices of bloodletting and leeching, albeit with a vastly different understanding and application. In its modern form, hemodilution was developed as a technique in the mid-20th century, with the advent of heart surgery necessitating blood conservation strategies and improved methods of managing blood viscosity during and after surgical procedures.


Hemodilution can be achieved through several methods, broadly categorized into normovolemic and hypervolemic. Normovolemic hemodilution involves the removal of a certain volume of blood from the patient, immediately replacing it with an equal volume of a crystalloid or colloid solution, thus maintaining normal blood volume while reducing red cell concentration. Hypervolemic hemodilution, on the other hand, adds volume to the patient’s circulatory system without the removal of blood, diluting the blood with additional fluids. This method is often used intraoperatively to manage blood viscosity and improve circulation.

Common Drugs and Manufacturers

The practice of hemodilution frequently involves the use of various pharmacological agents, primarily crystalloids and colloids, to replace the volume of blood removed from the patient. Crystalloids, such as saline or Ringer’s lactate, are widely used due to their availability and cost-effectiveness. Colloids, including hydroxyethyl starches (HES), gelatins, and dextrans, are preferred in specific contexts for their longer-lasting volume expansion effects. Prominent manufacturers of these solutions include Baxter International, Fresenius Kabi, and B. Braun Melsungen AG, among others. The choice of agent depends on the patient’s condition, the specific requirements of the procedure, and the potential for adverse reactions.

Effects and Indications

The primary effect of hemodilution is the improvement of blood flow and oxygen delivery to tissues, which is particularly beneficial in surgical settings where blood loss is anticipated. By preemptively diluting the blood, surgeons can minimize the need for transfusions, reducing the risks associated with blood products. Hemodilution is indicated in a wide range of surgical procedures, especially those involving cardiopulmonary bypass, where managing blood viscosity is critical. Additionally, it has applications in treating conditions like peripheral artery disease and stroke, where improved microcirculation can significantly affect outcomes.


While hemodilution offers considerable benefits, it requires careful consideration and monitoring. The potential for diluting clotting factors and causing electrolyte imbalances necessitates close observation of the patient’s volume status and blood composition. Furthermore, the choice between crystalloids and colloids must be made judiciously, considering the risks of edema with crystalloids and kidney injury with certain colloids. Patient selection is crucial, as those with compromised cardiac or renal function may not tolerate the fluid shifts associated with hemodilution.

In conclusion, hemodilution represents a vital technique in modern medicine, offering a means to improve patient outcomes through enhanced blood flow and oxygen delivery. Its application, rooted in a deep understanding of hemodynamics and pharmacology, requires a nuanced approach to ensure safety and efficacy. As research continues to refine the methods and substances used in hemodilution, its role in managing and treating a broad spectrum of conditions is likely to expand, underscoring its importance in the medical field.

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