Hs & Ts – Spotlighting Hypovolemia

Hypovolemia

Hypovolemia is when there is a decrease in the volume of blood in the body. Hypovolemia can occur due to fluid loss (dehydration) or bleeding.

Hypovolemia Through Fluid Loss

Fluid loss can occur due to vomiting, diarrhea, sweating, and fever. 

To understand fluid loss, you need to think about the body’s compensatory mechanism. What’s going to happen in the body during fluid loss? The heart rate is going to increase in an attempt to maintain our cardiac output. Therefore, your patient might be very tachycardic. Additionally, the other mechanism to raise blood pressure is peripheral vasoconstriction. It might be very difficult to get an IV in your patient. You may need to take the intraosseous (IO) route. In general, after two attempts at the IV or 90 seconds, you go IO.

If intravenous (IV) route fails, then you will proceed to intraosseous (IO).

Providers use the MAP in other formulas to calculate other pressures throughout the body. It is also used as a guideline in certain treatment algorithms, such as the sepsis algorithm.

Read: ACLS Hs & Ts – Cardiac Tamponade

Hypovolemia Through Blood Loss

Another type of volume loss is blood loss. With blood loss, a confounding factor that oxygen carrying capacity is also lost due to less hemoglobin.

The reason hypovolemia made its way to the Hss and Ts list is because hypovolemia is often associated with pulseless electrical activity (PEA).

Related Video – What is PEA?

Take a look at this image of a patient below. Look at her skin. It is very pale. The textbook and the literature say to look for occult bleeding. Occult bleeding is bleeding that you can’t see because it’s occurring on the inside. For this patient, you can see there is bright red blood coming out from around the endotracheal tube. So the providers are debating whether this was maybe esophageal varices or a gastric ulcer that let go. No matter the source, there was profound blood loss. And in fact, this patient did develop PEA. The patient was very tachycardic and shortly after that, she arrested.

This patient is experiencing hypovolemia and PEA.

Remember that PEA is pulseless electrical activity. That does not mean the heart is not working. In fact, the heart may be working well and is still contracting. The heart can still be moving blood forward, but the cardiac output is so low that it will not produce a peripheral pulse.

Related Video – Treating Reversible Causes of PEA and Asystole

So how do you know if the heart is even working? If the valves are opening and closing, you’ll have heart tones. If you can’t feel it, you might be able to hear it. You could pull out a Doppler and try to find pulses. You can also perform a bedside echo. Look at the contractions to see if the heart is physically moving or not.

Use a doppler to find any heart tones.

Treatment of Hypovolemia

If the condition is due to fluid loss, replace it with crystalloid fluid. 0.9% normal saline and follow your local protocols. Some protocols call for 200 mL, 500 mL, or rapid administration of a liter of fluid. Again, any time you’re rapidly putting fluid into a patient, you want to monitor their lungs for fluid overload. To treat hypovolemia through blood loss, replace the lost blood.

Summary

How you treat hypovolemia depends on its cause. For fluid loss, replace with normal saline. For blood loss, replace it with blood. Remember, hypovolemia often causes PEA. For that reason, it is one of the Hs and Ts.