An ED shift story | EM Mastery Academy
It’s a busy night in the ED.
A 55-year-old patient arrives confused, hypotensive, and poorly perfused. His BP is 75/40 mmHg.
The team struggles to obtain IV access. After failed attempts, you place an intraosseous (IO) line.
Good. Now you have access for emergency treatment.
Before flushing the line, the nurse manages to aspirate a small amount of bone marrow blood.
She asks:
“Doctor, can we send this for blood tests?”
A simple question. But would you trust all the results?
What should we remember?
IO aspirates can provide useful information, particularly for selected tests such as pH, chloride, urea, and creatinine.
But there are important limitations.
Which IO blood tests can we trust?
| Laboratory test | Reliability | Practical interpretation |
|---|---|---|
| Sodium, chloride, bicarbonate | Good correlation | Useful preliminary results |
| Urea, creatinine, bilirubin | Good correlation | Useful preliminary results |
| pH | Good correlation | May help assess acidosis |
| Hemoglobin | Generally correlates | Confirm if critical |
| Glucose | Variable | Confirm important values |
| Potassium | Unreliable | May be falsely elevated |
| WBC, platelets, hematocrit | Unreliable | Do not substitute for a peripheral CBC |
| PCO₂, PO₂ | Unreliable | Do not substitute for a blood gas |
| AST, ALT, ALP | Unreliable | Confirm with venous blood |
| Lactate | Insufficient evidence in shock | Avoid relying on isolated IO lactate |
| ABO/Rh typing | Potentially reliable | Requires blood-bank acceptance |
These findings primarily concern initial bone marrow aspirates before flushing or infusion. Correlation does not establish interchangeability in every critically ill patient or on every laboratory analyser.
And there is another problem: bone marrow particles may interfere with laboratory analysers. Not every laboratory accepts IO samples.
A practical habit for your next shift
If an IO sample is needed, collect the initial aspirate before flushing or administering medications, when feasible.
Check which tests your laboratory accepts, clearly label the sample as intraosseous, and confirm important results using venous or arterial blood as soon as possible.
Meanwhile, don’t delay resuscitation while waiting for laboratory confirmation.
The IO line is there to help you treat the patient. It does not guarantee that every laboratory result is reliable.
One question worth remembering:
Before trusting an unexpected laboratory result, do you know where the blood came from?
Recognize early. Act early. Reassess often.
References
- Tintinalli’s Emergency Medicine, 9th ed. Chapter 114, Table 114-2: IO Laboratory Findings Compared With Phlebotomy.
- Roberts and Hedges’ Clinical Procedures in Emergency Medicine and Acute Care, 7th ed. Chapter 25: Intraosseous Infusion.
- Infusion Nurses Society. Infusion Therapy Standards of Practice, 9th edition. 2024.
- Royal Children’s Hospital Melbourne. Intraosseous Access Clinical Practice Guideline. Updated December 2024.
- Jousi M, et al. Analysing blood from intraosseous access: a systematic review. European Journal of Emergency Medicine. 2019.
