Choosing the right fluid to counter hypovolemic shock

Nursing, Mar 2004 by Diehl-Oplinger, Louise, Kaminski, Mary Fran

Hypertonic fluids have a greater tonicity than fluid in the extracellular compartment, so they exert more osmotic pressure. These solutions draw fluid from the intracellular to the extracellular compartment, causing cells to shrink and relieving cellular edema. But hypertonic solutions (such as 3% or 5% sodium chloride solution) raise the risk of volume overload, especially in a patient with heart failure, so assess his response to treatment frequently.

Another hypertonic solution, concentrated dextrose in water (20%, 40%, 50%, 60%, or 70%) is often added to amino acid solutions administered via central vascular access devices to correct hypoglycemia and provide calories. Monitor the patient's blood glucose levels for hyperglycemia and urine output and urine specific gravity for osmotic diuresis. Also monitor the patient's serum electrolytes.

Colloids

Colloids contain undissolved particles, such as protein, sugar, and starch molecules, which are too big to pass through capillary walls. A colloid solution draws fluid from the interstitial and intracellular spaces, increasing intravascular volume. The degree of osmotic pull that a colloid exerts depends on its particle concentration.

Colloid solutions have the same effect as hypertonic solutions and are given in smaller volumes. They also have a longer duration of action because the larger molecules stay in the intravascular compartment longer.

Albumin is the most frequently used colloid solution. A commercially prepared solution, albumin is extracted from human plasma and heated to kill pathogens. It's available in 5% or 25% concentrations (the 5% solution is isotonic) and contains no clotting components. Use albumin for volume expansion when crystalloid solutions are inadequate, as a plasma substitute when treating patients with hypovolemic shock and massive hemorrhage, and to treat patients exhibiting third-spacing of fluid into the interstitial spaces.

A patient who's lost fluid during thoracic surgery would benefit from albumin used as the primary fluid in resuscitation because it enhances blood volume, improves hemodynamics, and reduces the need for blood transfusions.

Blood and blood products

Whole blood contains red blood cells (RBCs), white blood cells, platelets, and plasma. Because storage degrades blood quality fairly quickly, units of whole blood are typically broken down into separate units of RBCs, platelets, and fresh frozen plasma. White blood cells may be removed from the plasma during processing of the blood product. Blood loss can often be managed with blood components and crystalloid and colloid solutions. Whole blood is rarely used unless it's less than 24 hours old and the patient is exsanguinating.

Packed RBCs have the same cell mass as whole blood, making them a good choice for patients who need increased RBC mass and oxygen-carrying capacity without volume overload or for patients with symptomatic anemia, hypovolemic shock, or symptomatic acute or chronic blood loss. Each unit of packed RBCs is typically infused over 1 to 2 hours, but always within 4 hours. Monitor a patient with a poor ejection fraction or a history of heart failure closely. He may require infusions of packed RBCs (smaller-volume infusions than whole blood), perhaps alternating with doses of a diuretic.