Ethylene glycol toxicity

Background

• Characteristics
  • Component of antifreeze, automobile coolants, de-icing agents, industrial solvents and hydraulic brake fluid.
    • Fluoresces yellow/green under Wood's lamp (neither Sn nor Sp)
  • Sweet taste
  • Lethal dose = 1g/kg
    • Volume depends on percentage of ethylene glycol in solution, typically 0.6 g/mL
    • 60 kg patient lethal dose ~ 100 mL
• Parent compound causes inebriation; metabolite (glycolic acid) causes toxicity

Clinical Features

Stage 1 - CNS

• 30min-12hr after ingestion
• Appears intoxicated (slurred speech, ataxia, stupor, seizure, coma)

Stage 2 - Cardiopulmonary

• 12-24hr after ingestion
• Most deaths occur during this stage
  • Hypertension, tachycardia, CHF
  • ARDS, pulmonary infiltrates
  • Hypocalcemia (chelation by oxalate)
  • Myositis & CK elevation

Stage 3 - Renal

• 24-72hr after ingestion
  • Flank pain, CVA tenderness
  • Hematuria, proteinuria, calcium oxalate crystals (50%)

Differential Diagnosis

Sedative/hypnotic toxicity

• Absinthe
• Barbiturates
• Benzodiazepines
  • Flunitrazepam (Rohypnol)
• Chloral hydrate
• Gamma hydroxybutyrate (GHB)
• Baclofen toxicity
• Opioids
  • Lomotil toxicity
  • Loperamide toxicity
• Toxic alcohols
  • Ethanol
  • Ethylene glycol
  • Isopropyl alcohol
  • Methanol
• Xylazine toxicity

Diagnosis

• Chemistry
  • Anion gap acidosis
    • Will not be present immediately after exposure (only metabolite causes acidosis)
  • Renal failure
• Serum Osm
  • Osm gap
    • Calculated serum osm - measured serum osm
      • Calculated serum osm = 2Na + BUN/2.8 + glucose/18 + ethanol/4.2)
    • Normal < 10
    • >50 highly suggestive of toxic alcohol poisoning)
    • 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
• Glucose
• Alcohol levels
• UA
  • Hematuria, proteinuria, pyuria
  • Calcium oxalate crystals (late finding; only seen in 50%)
  • Urinary fluorescence (may be seen 6 hours after ingestion)
• Total CK
• VBG
• ECG
  • QT prolongation ~ hypocalcemia
• APAP/ASA levels

Treatment

ADH enzyme blockade

Fomepizole:

• Indications:
  • Ethylene glycol level >20mg/dL
  • Suspected significant ethylene glycol ingestion w/ ETOH level <100mg/dL
  • Coma or AMS in pt with unclear history and osm gap >10
  • Coma or AMS in pt with unclear history and unexplained met acidosis and ETOH level <100
• Dosing
  • 15mg/kg IV over 30min; follow by 10mg/kg q12hr until level <20 or acidosis resolves

Ethanol:

• Ethanol drips are rarely used
• BAL of 100-150 completely saturates alcohol dehydrogenase
• Dosing:
  • IV: load 800mg/kg; then give 100mg/kg/hr
  • Oral: 3-4 1-oz "shots" of 80-proof liquor); then give 1-2 "shots" per hour

Correction of metabolic acidosis

Bicarbonate infusion is an option however the patient will need to compensate with an increased respiratory rate otherwise a concomitant respiratory acidosis will ensure.

• Bicarbonate 1-2mEq/kg IV bolus to attain pH = 7.45-7.50
  • Follow by infusion of 150mEq/L in D5 @ 1.5-2 times maintenance fluid rate
• Monitor for worsening hypocalcemia

Dialysis

• Indications:
  • Refractory metabolic acidosis (pH <7.25) w/ AG >30
  • Renal insufficiency
  • Deteriorating vital signs despite aggressive supportive care
  • Electrolyte abnormalities refractory to conventional therapy
  • Ethylene glycol level >50mg/dL (controversial)
  • Glycolic acid level > 8 mmol/L (glycolic acid is metabolite that causes anion gap acidosis)

Decrease oxalate production

• Thiamine 100mg IV q6hr x2d
• Pyridoxine 50mg q6hr x2d
• Magnesium 2gm IV x1

See Also

• Sedative/hypnotic toxicity