POTD: ABG vs VBG

Alexander Selby · June 30, 2021 ·

Today we look at the difference between ABG and VBG in the ED clinical setting: When should you order an ABG and when does a VBG suffice?

pH

- Correlates closely

- VBG typically 0.03-0.04 lower than ABG

pCO2

- VBG can be used as a screen for hypercarbia (100% sensitive) for values < 45 mmHg

- ABG should be used to assess pCO2 for patients in shock states and when value is > 45 mmHg

- Mean difference is PvCO2 = PaCO2 + 5.7 mmHg

PO2

- Does not correlate

- ABG should be collected depending on clinical circumstance, ie. ARDS, severe hypoxemia, severe acidosis, poor peripheral perfusion, pulse ox not accurate, etc.

HCO3

- Correlates closely

- Is a calculated value - get a BMP for more accurate result

Lactate

- Correlates closely

- Mean difference is 0.02-0.08

Base Deficit / Base Excess

- Correlates closely

- Difference is not clinically significant

Remember:

- ABGs are not without risk!

- Disadvantages include risk of bleeding/hematoma, pain, nerve injury, digital ischemia, delays in care, risk of pseudoaneurysm and AV fistula, etc.

Takeaways:

- Get an ABG in patients with severe shock, hypoxemia, or when PaO2 is clinically relevant.

- A VBG is sufficient to trend pH, lactate, pCO2 when not hypercarbic, and base deficit.

- If you’re really concerned about HCO3, check a BMP.

- As always, any test you order should be clinically relevant and benefits outweigh the risks.

EMS Protocol of the Week - Abdominal Injuries and Chest Injuries (Adult and Pediatric)

David Eng · June 29, 2021 · EMS

Last week, we talked about what EMS does for someone whose belly hurts. This week, we get to talk about what EMS does for someone whose belly hurts because they got stabbed!

Once again we find ourselves discussing trauma protocols, which comes with the requisite reminder that the majority of prehospital trauma care comes at the BLS level, since the name of the game is generally rapid transport to the hospital. For abdominal injuries, after addressing ABCs there’s little more involved aside from special considerations for evisceration injuries (tldr – don’t shove bowel back inside, just cover it with moist gauze). For chest injuries, the protocol addresses dressing (and, if needed, “burping” the dressing for) sucking chest wounds. There is also reference to Appendix O, which describes how to perform a needle decompression in cases of tension pneumothorax.

Not a lot of OLMC-specific stuff in either of these protocols, but now you have something to refer to the next time an EMT calls the phone asking for help! www.nycremsco.org or the protocol binder if you want to brush up even more.

Dave

EMS Protocol of the Week - Abdominal Pain / Severe Nausea / Vomiting (Adult and Pediatric)

David Eng · June 15, 2021 · EMS

The big take-home of the EMS protocol for abdominal pain/nausea/vomiting is a reiteration to be mindful of prehospital therapies administered before you receive the patient in the ED. After appropriately addressing any trauma, sepsis, or other potential emergent issues masquerading as abdominal pain, paramedics operating under this protocol can give up to two doses of (weight-based) ondansetron by Standing Order, up to 8mg total. For patients receiving ondansetron, paramedics are reminded to consider the QT-prolonging effects of the med and act accordingly. If you have the chance to chat with the medics when they arrive to the ED, remember to check for this before you add additional meds and throw the patient into Torsades!

Be aware that you may also receive an OLMC call requesting pain medications for these patients. Note that analgesics are not currently described in this protocol as either Standing Order or Medical Control Option, so any med requested (likely either morphine or fentanyl) would have you be approved as a Discretionary Order. Use your judgment for these requests, don’t forget to check the vitals, and remember that controlled substances require a tracking number (MMC-####).

That’s all for now! www.nycremsco.org or the protocols binder to keep you going until next week!

Dave