Is there a relationship between SpO2 or BP and hemoglobin?

Lev, MSN, RN, NP · Jan 4, 2018

I would think the opposite. If a patient is bleeding excessively and has a low hemoglobin because of that you can see hypotension.

Lev, MSN, RN, NP · Jan 4, 2018

There really isn't such thing as high SpO2. There is only abnormal which is below 90-95%.

oops I bradyed again · Jan 4, 2018

You cannot assume a patient's hemoglobin levels based on their SpO2 reading. SpO2 is specifically measuring how much oxygen hemoglobin are currently carrying. Because hemoglobin can only carry so much oxygen (4 molecules of O2 per hemoglobin) you cannot really have a "high" SpO2. Once you're at 100% you have maxed out your O2 carrying capacity.

The most accurate way to determine a person's hemoglobin level is to draw a Complete Blood Count (CBC). This blood panel will include the amount of hemoglobin in the blood expressed as grams per dL. Normal hemoglobin (Hgb) levels are about 12-16 g/dL, depending on if the person is male or female. Let's say you have a patient with a low Hgb at 9, but all of their hemoglobin are carrying 4 molecules of O2. This means you will have an SpO2 of 100%, despite the patient having low Hgb levels. You can see why SpO2 is not an accurate indicator of Hgb levels.

Low levels of O2 due to poor heart function can cause elevated Hgb levels, but hypertension does not always lead to high Hgb levels. In fact, decreased Hgb levels are more common than elevated Hgb. Hope this helps!

jodispamodi · Jan 4, 2018

BP is r/t the contractility of arteries and has no bearing on hgb, anemia, hypovolemia will cause low bp by less fluid volume in the vessels, spO2 does not really measure hgb, ie, it doesnt count blood cells. The only way to have a reliable hgb measurement is through CBC.

Mintke · Jan 4, 2018

Don't forget that sat probes only recognize that something is bound to the hemoglobin molecules, not necessarily oxygen. The only definitive test for blood oxygenation is a blood gas