Albumin is the most abundant protein found in human blood plasma, synthesized exclusively by the liver, with a normal concentration ranging from about 3.5 to 5.0 grams per deciliter. While it serves multiple functions, including transporting various substances, its most significant role is regulating fluid movement between the blood vessels and the body’s tissues. This therapeutic agent, derived from donated human plasma, is administered intravenously to patients experiencing severely low blood pressure (hypotension), particularly when the cause is related to inadequate circulating blood volume. Its use is reserved for specific, complex medical situations where standard fluid treatments have been unsuccessful or are less appropriate.
The Role of Albumin in Maintaining Fluid Balance
Albumin’s function is maintaining the body’s fluid distribution. It generates colloid osmotic pressure, also known as oncotic pressure, inside the blood vessels. This pressure is the primary force that keeps fluid within the vascular system, preventing it from leaking out into the surrounding interstitial space. Albumin accounts for roughly 80% of the total oncotic pressure in the plasma.
The protein also acts as a carrier, transporting essential molecules that are not easily dissolved in water, including hormones, fatty acids, bilirubin, and many therapeutic drugs. The liver produces about 10 to 15 grams of albumin daily. When the body’s own albumin levels drop, this leads to a decrease in oncotic pressure, causing fluid to shift out of the blood vessels and accumulate in the tissues, resulting in edema.
How Albumin Counteracts Low Blood Pressure
When a patient experiences critically low blood pressure due to low circulating volume, therapeutic administration of human albumin solution rapidly corrects this imbalance. The infused albumin increases the concentration of protein within the blood vessels, intensifying the colloid osmotic pressure. This boosted oncotic force draws excess fluid from the interstitial space back into the bloodstream.
By pulling this fluid into the vascular system, the treatment expands the total circulating blood volume. This rapid volume increase improves the amount of blood returning to the heart (preload), allowing the heart to pump more blood with each beat, ultimately raising the patient’s blood pressure. Albumin solutions are available in 5% (iso-oncotic) and 25% (hyper-oncotic) concentrations. The 25% solution has an oncotic effect approximately five times greater than normal plasma, rapidly recruiting significant fluid into the circulation.
Clinical Scenarios Requiring Albumin
Albumin is not a first-line treatment for simple volume loss; it is reserved for complex clinical conditions where its unique oncotic properties are needed. One established use is in patients with advanced liver disease, specifically cirrhosis. When a large volume of fluid (more than five liters) is drained from the abdomen in large-volume paracentesis (LVP), albumin is administered to prevent a sudden drop in blood pressure and circulatory dysfunction.
In spontaneous bacterial peritonitis (SBP), a serious infection complication of cirrhosis, albumin infusion is recommended alongside antibiotics to prevent kidney impairment and improve patient survival. Albumin may also be considered in patients with septic shock, where the body’s response to infection causes dangerously low blood pressure. In these scenarios, albumin is added to the fluid resuscitation regimen when standard crystalloid fluids are insufficient to stabilize circulation.
For patients undergoing kidney replacement therapy, a concentrated 25% albumin solution may counteract episodes of hypotension during the dialysis process. This helps maintain hemodynamic stability and enhances the effectiveness of fluid removal. Its use in conditions like hypovolemic shock or severe burns is often a second-line option, used when initial resuscitation with crystalloid solutions has been ineffective.
Practical Considerations for Administration and Monitoring
Albumin is a plasma-derived blood product requiring careful handling and is always administered intravenously. The concentration and rate of infusion are tailored to the patient’s specific clinical needs. For instance, the hyper-oncotic 25% solution must be infused slowly, typically not exceeding 1 to 2 milliliters per minute, to prevent a rapid, overwhelming fluid shift.
Strict patient monitoring is required during and after administration to detect potential adverse effects. The most significant risk is fluid overload (hypervolemia), which can lead to complications like pulmonary edema, where fluid accumulates in the lungs. Healthcare providers closely track vital signs, including blood pressure and heart rate, and signs of respiratory distress to ensure fluid expansion remains within safe limits. Laboratory parameters like kidney function and electrolytes are often monitored, as concentrated solutions can affect their balance.