How to Pass the NBRC RRT Exam Information Gathering Section: When to order and how to interpret the CBC

Image of red blood cells

The complete blood count (CBC) is a frequent option on the NBRC Clinical Simulation Exam. When appropriate to order, the CBC will often be worth +1 point as part of the Information Gathering section. 

The CBC is also frequently encountered on the NBRC TMC Exam. On the TMC exam there may be a few questions where you are expected to know the normal values of all 3 parameters as well as how to treat the abnormal values.

A CBC test includes three main components:

  1. Red blood cells
  2. White blood cells
  3. Hemoglobin

Red Blood Cells (RBC)

The main role of RBC’s from a Respiratory perspective is to carry Oxygen to the organs, tissues, and cells throughout the body. So a loss of red blood cells can cause serious effects if untreated.

If the RBC count is low (anemia), you have two options:

  1. You can give the patient packed RBC’s (highly concentrated red blood cells with no other fluids present).
  2. You can give the patient whole blood (which is not concentrated RBC’s but also contains serous fluids like plasma and electrolytes)

If the RBC count is high (polycythemia), it may indicate 1 of 2 things.

  1. The patient either lives at a high elevation where oxygen concentrations are low therefore their body creates extra red blood cells to compensate (this is never treated).
  2. Or the patient has chronic hypoxemia. If hypoxemia is also present, look for other signs like digital clubbing which will clue you in to the fact that the patient has a severe pulmonary condition that is chronic. From there, treat as is appropriate for the situation.

White Blood Cells (WBC)

The main role of WBC’s is to attack and kill any foreign organism such as a bacterium like e-coli, or streptococcus. An elevated white count is a sure sign that your patient has a serious infection and treatment should include antibiotic therapy to help aid in killing the bacteria.  Low levels of WBC’s are also a problem and can clue you in to the fact that the patient is prone to infections and may not be able to fight them well on their own. Low white counts are common in patients who are receiving chemotherapy or radiation, or who have an autoimmune disease like HIV or AIDS.

Regardless of the cause, these patients should be protected from others who may have infections by being placed in extreme airborne precaution rooms (referred to as neutropenic precautions) and given antibiotics any time an infection is suspected.

Hemoglobin (Hgb)

Hemoglobin are the protein portions of the RBC that contain iron giving blood cells their red appearance. Each hemoglobin unit has four sub-units that Oxygen affixes itself to in order to be carried throughout the body to all organs, cells, and tissues. As with a low RBC, if the patient’s hemoglobin is low, you should look for any signs of trauma which leads to bleeding and a reduction of both values. Treat low Hgb as you would treat low RBC’s (see above).

During your 20 clinical simulations, if you are presented with a non-emergent situation and have a CBC, serum electrolytes, and an ABG available as options, select all 3. Think about it…

There is no emergency, each of them are fairly non-invasive but provide you with a ton of information about your patient’s condition and ability to oxygenate and ventilate. Each of them will be worth +1 point, and can help give you that extra bump that you need to receive a passing score

About Damon Wiseley, RRT-CPFT, B.H.S.c 9 Articles
Lead writer at Respiratory Cram RRT-CPFT B.H.S.c. Nova Southeastern University