Volume expanders and blood loss

Much research is being conducted into the safe alternatives to blood transfusions. This article will present some of the alternatives being used now as volume expanders and fluid replacements. Substitute blood and others are being studied that hold much promise for the future.

Volume expanders

Volume expanders may be used in acute traumatic blood loss. The greatest need at this time is to stop bleeding and replace volume to prevent circulatory collapse and shock. By providing volume expanders, the remaining red blood cells in the body can still carry oxygen to the tissue of the body. In this process, amazing circulatory compensatory mechanisms take place: the heart pumps a larger quantity of blood with each beat thus delivering oxygen to tissue and organs of the body. With these compensations taking place, a patient can survive with a hemoglobin level one-third that of a healthy person. (“Alternatives to blood transfusions” http://www.wikipedia.com/).


Below is a list of volume expanders that may be used as fluid replacements and may avoid blood transfusions. The first group that will be looked at is crystalloids.

A. Crystalloids -

0.9 Normal sodium (NaCl)  is equivalent to the sodium content in body fluids. This fluid increase the oncotic pressure in the intravascular space - water moves into the intravascular space to increase blood volume.

Lactated Ringer’s is a fluid and electrolyte replenisher that similarly increases the oncotic pressure in the intravascular space - again,  fluid is drawn into the vascular space.

B. Colloids -

Haemaccel is used as a plasma volume substitute in the initial treatment of hypovolemic shock due to hemorrhage or crush injuries.
Produces a significant increase in blood volume, heart output, urine output and oxygen transport.

Gelofusin - Contains modified fluid gelatin which behaves in a similar way to natural plasma albumin.

It is used for shock caused by a reduction in the volume of blood due to excessive blood loss. (“What are non-blood volume expanders?” bloodlessmedicine.org).

Dextran


Large molecules composed of chains of sugar molecules. These are formed as a means of storing food by bacteria and yeast. In purified form, certain dextrans can be used IV to expand a patient’s blood voume in medical emergencies where blood pressure drops to dangerously low levels. (“What are non-blood volume expanders?” bloodless medicine.org).




Hetastarch and Pentastarch

Are solutions of large molecules composed of many smaller molecules. They act by holding blood within the blood vessel thereby expanding blood volume and help maintain blood pressure. These substances also, do not contribute to the blood’s oxygen carrying capacity.

The drawback of volume expanders such as normal saline and lactated ringer’s is that they do nothing to assist in the oxygen carrying capacity of blood. Also, these substances flow in and out of the blood vessels they may initially provide volume expansion, the fluids eventually move out of the blood vessels. (“The right plasma volume expanders” nursing times.com)



Vocabulary

Colloid - is a substance that is microscopically dispersed throughout another one.

Crystalloid - is a substance that in solution can pass through a semi-permeable membrane.

hypovolemia - loss of blood volume.
Intravascular blood - blood volume inside the blood vessels.

Oncotic pressure - Pressure exerted by proteins in blood plasma that tends to pull water into the circulatory system.

Volume expanders - Expands the amount of circulating in the blood volume. Without adequate volume shock and circulatory collapse could occur.

(definitions: med-dictionary.com)