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Dr Keli Med III lectures 2013

ETHYLENE GLYCOL

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ETHYLENE GLYCOL Has many commercial uses as a coolant(antifreeze), preservative, andglycerine substitute; it has also beenused in lacquers, cosmetics, polishes,and detergents.

It may be ingested as an alcoholsubstitute by alcoholics, in suicideattempts, and accidentally by children.

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Ethylene Glycol

Methanol

Ethylene Glycol / Methanol

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ETHYLENE GLYCOL Ethylene glycol's toxicity is theresult of the formation of two

toxic metabolites, formaldehydeand formic acid. As with methanol, therapeutic

strategies are based on preventionof formation of these metabolitesor their removal from the body.

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Pathophysiology Ethylene glycol is a colorless, odorless,sweet-tasting substance.

It is highly water-soluble and rapidlyabsorbed when ingested orally, but notwhen exposure is via the lungs or skin.

Peak blood levels occur within 1 to 4 hof an ingestion. The plasmahalf-life is3 to 5 h.

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Pathophysiology Ethylene glycol is metabolized in the liver and

kidneys to toxic metabolitesaldehydes,glycolate, oxalate, and lactatewhich in turn

cause toxicity to the lungs, heart, and kidneys. These metabolites also cause the metabolic

acidosis associated with ethylene glycol poisoning.

The potentially lethal dose in adults is 2 mL/kg,although survival has been reported afteringestions ranging from 240 to 2000 mL.

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Methanol Ethylene Glycol

Alcoholdehydrogenase

FormaldehydeAldehyde

dehydrogenase

Formic acidLactic

DehydrogenaseOr

Glycolic acidOxidase

Glyoxylic acid

&Oxalic acid

A-OH-Bketoadipic acid

Glycine andbenzoic acid

Ethylene Glycol / Methanol

Glycoaldehyde

Glycolic acid

Th

B6

CO2& H2O

Folate

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Clinical Features Ethylene glycol poisoning often exhibits

three distinct clinical phases, the severityand progression of which depends on the

amount ingested:1)The initial phase(CNS depression) 1 to12 h after ingestion.2)The second phase(cardiopulmonary

phase) develops 12 to 24 h afteringestion.3)The third phase (nephrotoxicity) occurs24 to 72 h after ingestion.

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The initial phase Patients may appear inebriated, with slurred

speech and ataxia but without the odor ofethanol on their breath.

Hallucinations, coma, seizures, and deathmay also occur during this initial phase.

The optic fundus is usuallynormal,differentiating the syndrome frommethanol poisoning, although nystagmus and

ophthalmoplegia may be observed. Lumbar puncture may demonstrate elevated

CSF pressure and protein and a fewpolymorphonuclear cells.

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The second phase

The second, cardiopulmonary phase develops12 to 24 h after ingestion. Tachycardia, mild

hypertension, and tachypnea are the mostcommon symptoms;

Congestive heart failure, acute respiratorydistress syndrome, cardiomegaly, and

circulatory collapse are also observed. Myositis has also been reported less

commonly during this phase.

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The third phase Early symptoms consist of flank pain and

costovertebral angle tenderness. Oliguricrenal failure and acute tubular necrosisensue.

Complete anuria may occur, but most patientsrecover without renal damage if they receiveappropriate therapy.

Nephrotoxicity is caused by aldehyde

metabolites and oxalic acid. Two forms ofurinary calcium oxalate crystals may beidentified on microscopic evaluation of theurine.

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Clinical Features Hypocalcemia may develop secondary to

precipitation of calcium as calcium oxalate andmay be severe enough to cause tetany and

prolongation of the QT interval. Elevated serum creatine phosphokinase levels

may accompany and explain the generalizedmyalgias experienced by some patients.

Leukocytosis is common and should not beconsidered a manifestation of infection unlessclinical signs are present.

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Clinical Features Tentative diagnosis and initiation of treatment

should be based on history and characteristicclinical presentation.

As with methanol poisoning, confirmation of atentative diagnosis depends on identification ofthe substance in the bloodstream, but

treatment should be initiated based oncompatible clinical presentation to avoidmorbidity resulting from delay.

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Clinical Features Serum levels greater than 20 mg/dLare likely to result in toxicity. Survival

has been reported with levels up to650 mg/dL, while fatality has beenassociated with levels >98 mg/dL.

Serious intoxication has been reportedin the absence of an osmolar gap orcalcium oxalate crystalluria.

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Treatment The management of ethylene glycolpoisoning is similar to that ofmethanol poisoning.

Indications for gastric emptying

and guidelines for administration ofsodium bicarbonate are the same asthose given for methanol.

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Treatment If the patient is hypocalcemic, 10 mL of

calcium gluconate 10 percent should be givenIV.

Pyridoxine 100 mg and thiamine 100 mg IMor IV should be administered daily tofacilitate metabolism of ethylene glycol bynontoxic pathways.

Magnesium has also been shown to be acofactor in the metabolism of toxicmetabolites and should be given if patientsare hypomagnesemic, as is often the casewith alcoholics.

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Treatment Laboratory tests that may be useful in

evaluating patients suspected of ethyleneglycol ingestion include complete blood count;

serum electrolytes; acetone; alcoholtoxicology panel with ethanol, isopropanol, andmethanol determinations; electrolytes; bloodurea nitrogen; creatinine; salicylate level;arterial blood gases; urinalysis; serum

ethylene glycol level; calcium; creatinephosphokinase (CPK); and magnesium levels. Lactate levels should also be determined if

the reason for the severe acidosis is unclear.

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Treatment Competitive inhibition of alcohol

dehydrogenase's breakdown of ethylene glycolwith fomepizole or ethanol should be initiatedin the ED when overdose is suspected orconfirmed.

Fomepizole has supplanted ethanol as theinitial treatment of choice. Dosing is thesame for ethylene glycol as for methanol.

Ethanol's affinity for alcohol dehydrogenaseis 100 times that of ethylene glycol, resultingin a prolongation of the half-life of ethyleneglycol to 17 h.

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Treatment Oral and intravenous dosing guidelines

for ethanol are identical to thoseoutlined for methanol, above. Due toease of administration, greateraffinity for alcohol dehydrogenase,and a superior side-effect profile,

fomepizole is the drug of choice unlessit is not readily available or there is ahistory of allergy to fomepizole.

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As for methanol,fomepizole or ethanoladministration and dialysisshould be continued untilserum blood levels ofwhichever substance hasbeen ingested are zero

and acidosis has resolved.

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Indications for Dialysis withEthylene Glycol Poisoning

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Disposition

Any patient with the serious signs andsymptoms associated with ethylene glycol ormethanol intoxication, or a history of

significant ingestion even in absence ofsymptoms, should be admitted to an intensivecare setting.

Because the symptoms of ethylene glycol andmethanol intoxication may be delayed,

patients who have ingested these substancesshould be admitted to the hospital forobservation and laboratory testing even ifthey are initially asymptomatic.

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