Clinical Correlations and Calculations

Suggestions for Dealing the  Physician’s Request for Quantitative Volatiles, Ethylene Glycol (EG) and Propylene Glycol (PG).

Is there a strong suspicion to believe ingestion has occurred WITHIN the last 12-24 hours? Remember, these subtances have relatively short elimination T½ (2-5 hrs, except MeOH, 2-24 hrs) and may not be detectable in blood after 24 hrs.

Serum electrolytes
Serum glucose
Serum EtOH
Serum/urine ketones
Serum ionized calcium
Serum creatinine
Serum urea (BUN)
Serum lactic acid
Serum osmolality
Urine drug screen

3. For MeOH poisoning: vomiting, coma, seizures, visual disturbances, motor restlessness, etc.

4. For EG or PG poisoning: altered mental “Stat”us, acidosis, seizures, coma. Appears drunk but no ETOH smell on breath. EG: Renal failure and decreased serum calcium, urinary calcium oxalate crystals (late phase). PG: especially toxic at low concentrations in adults with impaired renal function and in children.

5. Insist that calculated osmolality and anion gaps be done to help estimate toxicity.

Measured osmolality by freezing point depression.
Normal range: 280 – 300 mOsm/Kg

Calculated Osmolality:

2 [Na] + [BUN] + [Glu] + [EtOH]
                 2.8          18         4.6

Osmolal gap ( ∆ Osmolality) = (measured osmolality) – (calculated osmolality)
                                                                              0.93

Reference Range: < 10 mOsm/kg

Simple calculated anion gap: [Na+] – [(CI-) + (HCO3-)

Reference range: 8 – 17 mmol/L

(ref., Tietz Clinical Guide to Laboratory Tests, 3rd ed.)

6. Have the following information available to discuss potentially toxic ingestions:

For MeOH and the glycols:

Evidence of metabolic acidosis (HCO3-, blood pH)
Evidence of widened anion gap
Evidence of widened osmolal gap
Ketonuria
Oxalate crystals in urine with EG
Lactic acidosis with EG and PG

For EtOH poisoning

Evidence of widened osmolal gap
Evidence of widened anion gap
Evidence of ketosis

7. If still in doubt, consult with your chief resident or the attending on call.

8. Call in a technologist only when it is clear to you that the request is justified by clinical and laboratory data. The technologist may ask the CP resident whether the laboratory tests listed above have been done.

Copyright © 2005 Madory Consulting
Last modified: 03/05/06