Crystalloids versus Colloids

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Infusion Therapy is an awesome wonder when it comes to saving a patient’s life.  Is it really necessary to give a patient a Colloid versus a Crystalloid?

Trauma burns or surgery can cause people to lose large amounts of blood. Fluid replacement, giving fluids intravenously (into a vein) to replace lost blood, is used to try to maintain blood pressure and reduce the risk of dying. Blood products, non-blood products or combinations are used, including colloid or crystalloid solutions. Colloids are increasingly used but they are more expensive than crystalloids and there are many scientific studies that show no evidence colloids reduce the risk of dying compared with crystalloids.

 B A C K G R O U N D

Fluid resuscitation for hypovolemia and other medical issues is common practice in the medical management of critically ill patients, whether as a result of trauma, burns, major surgery, dehydration, or sepsis.  

Colloids have been widely used all over the country for quite some time and volume replacement with colloids is considerably more expensive than with crystalloids. 

In the early 1860's, it was the investigation by Thomas Graham’s that led him to classify substances as crystalloids or colloids based on their ability to diffuse through a parchment membrane. Crystalloids passed readily through the membrane, whereas colloids did not. Intravenous fluids are similarly classified based on their ability to pass through barriers separating body fluid compartments, particularly the one between intravascular and extravascular (interstitial) fluid compartments.

Crystalloids

According to the Tabers Medical Dictionary, a Crystalloid is a solution in which crystals can or may form; but is able to diffuse across cellular membranes. Crystalloids are the most common fluids used in the healthcare setting. The following are some examples of the most common solutions in the crystalloid category.

•  Normal Saline
• Lactate Ringers
• Dextrose 5%

Normal Saline

Normal Saline is composed of 154 milliequivalents (mEq/L) of Sodium and 154 milliequivalents of Chloride. The ph is 6.0 and the osmolarity is approximately 308. Normal saline is the main solution of choice when administering a blood product. (Raoof, George, Saleh, & Sung, 2008)

Lactate Ringers

Lactated Ringers is composed of 130 milliequivalents of Sodium, 4mEq of Potassium, 109 mEq’s of Chloride, and 28mEq’s of Lactate. The ph is approximately 5.1 and the osmolarity is approximately 273. (Raoof, George, Saleh, & Sung, 2008)

Dextrose 5%

Dextrose 5% is consists of 278 mmoL/L of dextrose. The pH is 4.0 and the osmolarity is around 272. D5W is considered an isotonic solution in the bag, but once administered the glucose is metabolized and the tonicity of the infused solution decreases in proportion to the osmolarity or tonicity of the non-dextrose components (electrolytes) within the water. 

Colloids

Again, according to Tabers Medical Dictionary a colloid is a “glue-like substance, such as a protein or starch… or a substance used as a plasma expander in place of blood.” (Wilbur, 2009) The following are some examples of colloid solutions.

•  Albumin
• Hetastarch
• Dextran

Albumin

Albumin is produced in a couple of varieties; typically 5% and 25%. Albumin “is made from pooled human plasma, which undergoes ethanol fractionation, ultra filtration, and pasteurization.” ²⁰

Albumin 5% contains no preservative and is a clear, slightly viscous liquid; it is almost colorless or slightly yellow tint. ⁷It is mainly used to expand the intravascular volume whereas Albumin 25% is typically used for hypoproteinemia. Albumin 5% is composed of 154 mEq’s of Sodium and 50 grams of Albumin and has a ph level of 6.6 as well as an osmolarity of 290.

Hetastarch (Hespan)

Hetastarch is another type of plasma expander and is similar in properties to Albumin. If given; it can sometimes cause an increase in the serum Amylase; which may throw healthcare professionals for a loop into thinking the patient may be suffering from pancreatitis. Hetastarch is composed of 154 mEq’s of Sodium with a ph level of 5.5 as well as an osmolarity of 310.

Dextran

Dextran is also a plasma expander; however, it is higher in molecular weight than Hespan. The amount of expansion it provides to the vascular system depends on the amount and rate of infusion. Just like with Albumin; Dextran is provided in a couple strengths; typically 40 or 70. Dextran 40 is composed of 154 mEq’s Sodium, a ph level of 6.7, as well as an osmolarity of 320. Whereas Dextran 70 is composed of 154 mEq’s Sodium, a ph level of 6.3, and an osmolarity of 310.

 

Crystalloids versus Colloids

So, what is the best choice for fluid resuscitation?  The problem is it takes a larger amount of crystalloids to resuscitate a patient fully; on the other hand it only takes a small amount of colloids. Colloids however are more expensive and can expand the intravascular space fairly rapidly. Depending on what the patient’s medical condition is and the end goal of the fluid resuscitation will depend on whether the healthcare provider administers a crystalloid or colloid. For example if a patient arrives to the emergency room or ICU and as in hypovolemic shock; the goal of fluid replacement would most likely be attained by administering a crystalloid. On the other hand if the patient is septic and has been diagnosed with septic shock the provider may give a colloid or crystalloid.

Final Thought

There is no evidence from randomized controlled trials that resuscitation with colloids reduces the risk of patient death, compared to the resuscitation with crystalloids, in patients with trauma, burns or following surgery. So this could help us conclude that the use of colloids may not only increase mortality; but they are also not associated with an improvement in survival and are considerably more expensive than crystalloids, it is hard to see how their continued use in clinical practice can be justified.