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Department: upFront: I. V. ROUNDS

The role of albumin in fluid balance

Hankins, Judy RN, CRNI, BSN

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doi: 10.1097/01.NURSE.0000302527.26765.69
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In Brief

ALBUMIN PLAYS an important role in maintaining intravascular oncotic pressure. Very low levels of albumin can lead to lower-extremity edema, ascites, and pulmonary edema secondary to increased vascular permeability. Decreased albumin levels are common in hospitalized patients, in part because administering I.V. fluids can dilute body fluids. One study found that 76% of critically ill children with shock, metabolic acidosis, and hyperlactatemia also had hypoalbuminemia, increasing their risk of death.1 In this article, I'll review albumin's role in the body and discuss how to recognize hypoalbuminemia and manage the patient's care.

What is albumin?

The liver produces 9 to 12 grams/day of this complex substance; a molecule of serum albumin looks like a large bunch of grapes. About 60% of albumin is located in the extravascular space.

Because of its strong negative charge, albumin is water soluble. It has a circulating life span of 12 to 20 days and a turnover rate of about 15 grams/day. Reserve albumin isn't stored. Albumin doesn't appear to decrease related to starvation, but catabolism slows due to redistribution.

One of albumin's functions is to maintain colloid osmotic pressure, which keeps fluid moving throughout the body. Albumin also helps metabolize and detoxify substances (such as bilirubin, metals, ions, enzymes, amino acids, hormones, free fatty acids, drugs, and phospholipids) and is a free-radical scavenger.

Disease can increase or decrease a patient's plasma albumin level. Elevated levels are less common, but dehydration is one cause.

Decreased albumin levels can be caused by decreased synthesis, increased catabolism, or a combination of these. The most common cause of decreased albumin is inflammation, which leads to hemodilution, loss into the extravascular space, increased albumin consumption by local cells, and decreased albumin synthesis.

To recognize hypoalbuminemia and develop a treatment plan, perform a patient assessment that includes a patient history and physical, medication reconciliation, clinical status, and lab data. Most albumin levels are determined through the use of an automated chemistry analyzer. Remember that albumin values may be reduced in patients taking allopurinol, asparaginase, azathioprine, chlorpropamide, cisplatin, dapsone, dextran, estrogens, ibuprofen, isoniazid, nitrofurantoin, oral contraceptives, phenytoin, high-dose prednisone, or valproic acid. Also, albumin values naturally fall in pregnancy, especially in the third trimester, because of the increase in plasma volume.

Increasing albumin levels

To treat a low albumin level, clinicians may debate whether to use a colloid or crystalloid as a replacement fluid.

  • Colloids include albumin and hetastarch; dextran also may be considered. Colloids provide greater volume expansion in relation to the volume administered and remain in the intravascular space longer than crystalloids. Also, colloids are less likely to cause interstitial edema. However, the safety and morbidity rates associated with colloid use have raised controversy.2
  • Crystalloids include lactated Ringer's solution and sodium chloride solutions (usually 0.9% sodium chloride solution). These solutions are less expensive than colloids but require greater volume administration to achieve equal plasma volume expansion.

Remember, parenteral colloids or crystalloids aren't substitutes for blood or blood products if the patient's blood has reduced oxygen-carrying capacity or if he needs replenishment of clotting factors or platelets. Administering albumin in these cases can cause an interaction among fibrinogen, immunoglobulin, and albumin, causing red blood cell aggregation in plasma.3

Because of its cost, albumin generally isn't used routinely for fluid resuscitation in critically ill patients. Albumin may be used in patients in hemorrhagic shock who can't have nonprotein colloids. For patients in nonhemorrhagic shock with sepsis, nonprotein colloids and albumin should be used cautiously.

Administering albumin

Albumin may be given regardless of the patient's blood group. The dosage and administration rate depends on the patient's condition, including his blood pressure (BP), pulse, hemodynamic status, hemoglobin and hematocrit values, plasma protein content or oncotic pressure, and degree of venous and pulmonary congestion. The infusion is titrated to the patient's needs and response to treatment.

The concentration of albumin administered depends on the patient's fluid and protein needs. A solution containing 5% albumin usually is given to hypovolemic patients; a 25% concentration is used if fluid and sodium intake must be minimized, as in children or patients with cerebral edema. A total of 125 grams of albumin may be administered within 24 hours, and no more than 250 grams within 48 hours. A 25-gram dose of albumin is the osmotic equivalent of two units of fresh frozen plasma and provides as much plasma protein as 500 mL of plasma or two units of whole blood. An infusion of 100 mL of 25% albumin solution draws 350 mL into the intravascular space, increasing plasma volume by 450 mL over 30 to 60 minutes.

Albumin can be infused rapidly in the initial treatment of hypovolemic shock; the infusion should be decreased as plasma volume returns to normal to reduce the risk of circulatory overload and pulmonary edema. (Older adults are especially at risk for these complications.) During the infusion, monitor the patient's BP and lab values (including hemoglobin, hematocrit, electrolytes, and protein levels). Monitor carefully for increased bleeding as BP returns to the normal range. Assess him for circulatory overload, pulmonary edema, lack of diuresis, and allergic reactions. A dehydrated patient may need additional fluids. Notify the health care provider immediately if adverse reactions occur.

By understanding albumin's role in the body, you should be able to administer it appropriately and safely.

REFERENCES

1. Hatherill M, et al. Correction of the anion gap for albumin in order to detect occult tissue anions in shock. Archives of Disease in Childhood. 87(6):526–529, December 2002.
2. Finfer S, et al. SAFE (Saline versus Albumin Fluid Evaluation) Study Investigators. A comparison of albumin and saline for fluid resuscitation in the intensive care unit. The New England Journal of Medicine. 350(22):2247–2256, May 27, 2004.
3. Ben-Ami R, et al. A synergistic effect of albumin and fibrinogen on immunoglobulin-induced red blood cell aggregation. American Journal of Physiology. Heart and Circulatory Physiology. 285(6):H2663-H2669, December 2003.

Resource

Cochran Injuries Group Albumin Reviewers. Human albumin administration in critically ill patients: Systematic review of randomized controlled trials. British Medical Journal. 317(7153):235–240, July 25, 1998.
    © 2007 Lippincott Williams & Wilkins, Inc.