Blood Alcohol Level Testing in the Emergency Department
To test blood alcohol level in the Emergency Department (ED), order a serum blood alcohol concentration (BAC) test, which is the most accurate method for determining alcohol levels in patients.
Testing Options for Blood Alcohol Concentration
Primary Method: Serum Blood Alcohol Test
- Serum blood alcohol concentration (BAC) is the gold standard for measuring alcohol levels in the ED
- Obtained through venous blood sampling
- Provides the most accurate measurement for clinical decision-making
- Results typically reported in mg/dL or g/L
Alternative Methods
Breath Alcohol Testing
- Can be used as a rapid screening tool using infrared breath analyzers 1
- Less invasive than blood testing
- Provides results within minutes
- Note: Breath alcohol concentration (BrAC) requires conversion to estimate BAC
- The conversion ratio between BAC and BrAC may need adjustment (average ratio ~2615) 1
- May underestimate actual blood levels in some cases 2
Point-of-Care Electrochemical Methods
- Rapid results (within 60 seconds)
- Strong correlation with traditional laboratory methods 3
- Useful when immediate results are needed
Clinical Considerations
When to Test
- Testing should be based on clinical suspicion of alcohol intoxication
- Indicated when alcohol may be contributing to:
- Altered mental status
- Trauma evaluation
- Psychiatric symptoms
- Unexplained metabolic abnormalities
Important Considerations
- Patient's cognitive abilities, rather than a specific blood alcohol level, should be the basis for clinical decision-making 4, 5
- No evidence supports delaying psychiatric evaluation to obtain a blood alcohol concentration if the patient is alert with appropriate cognition, normal vital signs, and a noncontributory history and physical examination 4
- Consider a period of observation to determine if psychiatric symptoms resolve as intoxication decreases 4
Sampling Considerations
- Venous blood samples are preferred over capillary samples
- Be aware that capillary BAC may exceed venous BAC during the absorption phase (first 60 minutes after drinking) 6
- In the post-absorption phase, venous BAC typically exceeds capillary BAC 6
Documentation Requirements
- Document the clinical indication for testing
- If a patient refuses testing, document:
- Assessment of the patient's capacity to refuse
- Information provided about the importance of testing
- Patient's understanding of implications of refusal 5
Pitfalls and Caveats
- Do not rely solely on BAC to determine a patient's clinical status or decision-making capacity
- A specific BAC threshold should not be used to determine when psychiatric evaluation can begin 4
- Routine testing without clinical indication is not recommended 4
- Be aware that timing of sample collection relative to alcohol consumption affects results 6
- Self-reported alcohol consumption may be more relevant for epidemiological studies than objective BAC measurements 7
Remember that the patient's clinical presentation and cognitive function should guide management decisions rather than relying exclusively on a specific blood alcohol concentration threshold.