Albumin is a protein found in the blood, playing an important role in maintaining the body’s fluid balance and blood pressure. It circulates throughout the bloodstream, helping to regulate the distribution of water between blood vessels and surrounding tissues. When blood pressure drops to dangerously low levels, medical professionals sometimes use albumin to help restore it. This article details how albumin is used to address low blood pressure, including its functions, mechanisms, and clinical considerations.
Understanding Albumin
Albumin is the most abundant protein in human blood plasma, making up approximately 50% to 60% of the total protein content. It is primarily synthesized in the liver and is rapidly released into the bloodstream, with about 10 to 15 grams produced daily in healthy individuals. Very little albumin is stored in the liver; most of it circulates freely.
A main function of albumin is maintaining oncotic pressure, also known as colloid osmotic pressure, within blood vessels. Oncotic pressure is the “pulling” force exerted by proteins, mainly albumin, that draws water into the circulatory system and helps keep it there. This force counteracts hydrostatic pressure, which pushes fluid out of the vessels into tissues. Albumin’s large molecular weight and negative charge allow it to attract positively charged molecules and water, effectively maintaining fluid within the intravascular compartment.
Albumin also serves as a transporter for a wide array of substances in the blood, including hormones, fatty acids, bilirubin, metal ions, and many medications. Beyond its role in fluid balance and transport, albumin contributes to the body’s health by acting as a buffer and a free-radical scavenger.
Albumin’s Role in Low Blood Pressure
When administered intravenously, albumin helps to raise low blood pressure by increasing the oncotic pressure within the blood vessels. This increased “pulling” force draws fluid from the interstitial space, the area between cells and outside of blood vessels, back into the bloodstream. This action increases the volume of fluid within the vessels, thereby increasing pressure.
Specifically, a 25% albumin solution is approximately five times more osmotically active than human plasma. This hyper-oncotic effect means it can attract a significant amount of water into the circulation. For example, 100 mL of 25% albumin can theoretically expand intravascular volume to about 450 mL within 20 minutes in a well-hydrated patient. This increase in circulating blood volume directly contributes to an elevation in blood pressure.
The expanded blood volume helps maintain cardiac output, particularly in states of shock. While albumin increases intravascular oncotic pressure, its effectiveness as a volume expander compared to other fluids like crystalloids is a subject of ongoing discussion in medical research.
When Albumin is Administered
Albumin is not a first-line treatment for all types of low blood pressure, but it is considered in specific medical scenarios where its properties are beneficial. One primary indication is in cases of hypovolemic shock, which results from severe fluid loss, such as from significant bleeding or severe burns. In these situations, albumin helps restore circulating blood volume by drawing fluid into the vessels. For example, in severe burns, albumin can be used to replace protein loss and correct low osmotic pressure.
It is also administered in certain liver conditions, particularly in patients with cirrhosis and ascites, where a large volume of fluid is drained from the abdomen (paracentesis). Administering albumin during large-volume paracentesis can help prevent a significant drop in blood pressure and circulatory dysfunction that can occur after fluid removal. Additionally, albumin may be considered for intradialytic hypotension in patients undergoing kidney replacement therapy, especially those with low albumin levels (hypoalbuminemia). In these instances, 25% albumin solutions can improve blood pressure and ultrafiltration rates.
Albumin is also used in conjunction with vasoconstrictors for hepatorenal syndrome, a severe complication of liver disease, to help manage hypotension. In patients with severe injuries, infections, or pancreatitis leading to hypoalbuminemia, albumin may be used when other treatments are ineffective.
Important Considerations for Albumin Use
Albumin is always administered intravenously by healthcare professionals, with the rate of infusion carefully controlled to prevent complications. For a 25% solution, the infusion rate should not exceed 2 mL per minute to avoid overloading the circulatory system. Patients receiving albumin require close monitoring for fluid balance, electrolyte levels, and kidney function, as well as their overall hemodynamic response.
Despite its benefits, albumin administration carries potential side effects. Patients may experience mild reactions such as nausea, vomiting, fever, chills, or a mild rash. More serious reactions include severe shortness of breath, wheezing, chest pain, a fast or uneven heart rate, and allergic reactions, including anaphylaxis, which is a severe, life-threatening allergic response.
There are specific situations where albumin might not be appropriate or should be used with caution. It is contraindicated in patients with a history of allergic reactions to albumin. Caution is advised in individuals with conditions that could be worsened by increased fluid volume, such as severe heart failure, severe anemia, or kidney failure with fluid overload. In patients with pulmonary edema, using albumin could exacerbate fluid accumulation in the lungs.
While albumin is derived from human plasma and undergoes processes to reduce viral transmission risk, a theoretical risk remains. The decision to administer albumin is a complex medical judgment, tailored to the individual patient’s specific condition.