Ethylene glycol toxicity

Background

• Component of antifreeze
• Lethal dose = 1g/kg of ethylene glycol
  • Volume depends on percentage of ethylene glycol in solution, typically 0.6 g/mL
  • 60 kg patient lethal dose ~ 100 mL
• Sweet taste
• Fluoresces yellow/green under Wood's lamp

Pathophysiology

• Ethylene glycol + alcohol/aldehyde dehydrogenase > oxalate + glycolic acid

Work-Up

1. Chemistry
   1. Anion gap acidosis
   2. Renal failure
   3. Osm gap
      1. Calculated serum osm = 2Na + BUN/2.8 + glucose/18 + ethanol/4.2)
   4. Serum Osm
2. Glucose
3. Ethanol level
4. UA
   1. Hematuria, proteinuria, pyuria
   2. Calcium oxalate crystals (late finding, only seen in 50%)
   3. Urinary fluorescence (may be seen 6 hours after ingestion)
5. Total CK
6. VBG
7. ECG
   1. QT prolongation ~ hypocalcemia

Note:

• Cannot rule out toxic ingestion with a "normal" osmol gap
  • Only parent alcohol is osmotically active
    • Delayed presentation may mean that much of it is already metabolized

Clinical Manifestations

• Patients may die in any stage!

• Stage 1 - CNS
  • 30min to 12h
  • Pt appears intoxicated (slurred speech, ataxia, stupor, sz, coma)

• Stage 2 - Cardiopulmonary
  • 12- 24h
  • Hypertension, tachycardia, CHF
  • ARDS, pulmonary infiltrates
  • Hypocalcemia (chelation by oxalate)
  • Myositis & CK elevation

• Stage 3 - Renal
  • 24- 72h
  • Flank pain, CVAT
  • Hematuria, proteinuria, calcium oxalate crystals (50%)

• Stage 4 - Delayed CNS
  • 6-12days
  • Cranial neuropathy

Treatment

1. Correction of metabolic acidosis with bicarbonate
   1. Bicarbonate 1-2mEq/kg IV bolus to attain pH = 7.45-7.50
      1. Follow by infusion of 150mEq/L in D5 @ 1.5-2 times maintenance fluid rate
   2. Monitor for worsening hypocalcemia
2. ADH enzyme blockade
   1. Fomepizole (4-MP)
      1. 15mg/kg followed by 10mg/kg q12hr x 4 doses
   2. Ethyl alcohol
      1. BAL of 100-150 completely saturates alcohol dehydrogenase
3. Removal of parent alcohol and metabolites via dialysis
   1. Indications (controversial):
      1. Severe acidosis (pH <7.30)
      2. Renal compromise
      3. Electrolyte imbalances unreponsive to conventional therapy
      4. Anion gap > 20
4. Other
   1. Thiamine 100mg IV q6hr and Pyridoxine 50mg q6hr
      1. Theoretically decreases oxalate production
   2. Replace Magnesium
   3. Hypercalcemia
      1. Symptomatic - treat cautiously (avoid further precipitation)
      2. Asymptomatic - do not treat

Source

Rosen's