136. Toxic Etoh Flashcards
What is methanol?
Clear, voltatile, colorless slightly sweet alc st room temp.
Aka wood alcohol
What things commonly have methanol?
Solvent or octane booster in gasoline
Windshield washer fluid
Antifreeze (brake line sp)
Embalming fluid
Camp stove fuel
How is methanol absorbed?
Gi
Average half life 5 mins, peak 30-60 mins
What is the toxic metabolite of methanol?
Formic acid then into formate and H ions
How is methanol metabolized?
Liver- ADH to formaldehyde
ThEN by ALDH to formic acid
Then THF to 10-formyl THF
to co2 and water
Ethanol metabolism to acetyl coa
By adh to acetylaldehyde
ALDH to
Acetate
Acetyl coa synthase to acetyl coa
Ethylene glycol 3 end products
Glycine
Oxalic acid
Alpha hydroxy beta keyoadipate
Ethylene glycol metabolism to 3 products
by adh to glycoaldehyde
ALDH to
Glycolic acid
A. Go and LDH to oxalic acid
B by pyridoxine to glycine
C by thiamine to alpha hydroxy beta ketoadipate
At toxic concentrations how long is half life of methanol?
24 h
With ADH inhibition by ethanol or fomepizole, half life of methanol extends to ?
Vs dialysis half life is ?
Upward of 50
Approx 3-4 hours
How does formic acid muck things up?
Binds iron to cause mitochondrial cyctochtome oxidase inhibition so interferes with oxidative metabolism (similar cn, co, hso4)
What concerning symptoms and diagnoses can methanol cause in the eye?
Optic disk of retina and retrolaminar optic nerve - inhibition of mitochondrial cytochrome oxidase —> myelin sheath damage and loss of vision
Basal ganglia and sub cortical white matter effected how by methanol?
inhibition of mitochondrial cytochrome oxidase —> myelin sheath damage
Major systems effected in methanol toxicity ?
Gi
Cns
Optic
Most characteristic vision change of methanol?
Spots with blurred vision/snowstorm vision
Altered visual fields
Blindness
Physical exam signs methanol toxicity
Reduced pupillary response to light
Hyperaemia optic disk
Edema retina
Loss of optic disk cupping
Central scotimata
Tachypnea
Shock
Rhabdo
Myoglobinuria
Death -cerebral edema and multi organ failure
Name 10 causes of an increased osmolar gap
Methanol
Ethylene glycol
Ethanol
Mannitol
Acetone
Fructose
Hyperlupidemia
Dka
Alcohol ketosis
Sickle cell
Multi organ failure
Septic shock
Uremia
Name 12 causes of anion gap elevation
Alcohol ketosis
Cyanide, co, colchicine
Acetaminophen
Toluene
Paraldehyde
Propylene glycol
Phenformin
Isoniazid, iron, ibuprofen
LA (sepsis, ischemia)
Ethylene glycol
Salicyclates
Methanol, metformin
Uremia
Dka
Name 7 causes of a double anion gap
Methanol
Ethylene glycol
Dka
Alc ketoacidossi
Uremia
Septic shock
Multi organ failure
Toxic etoh: vision loss?
Methanol
Toxic etoh hypocalcemia and calcium oxalare crystals
Ethylene glycol
Prognostic factors regarding methanol ingestion
Degree of acidosis (most important - high mortality at ph less than 7)
Time to presentation
Imitation of treatment
Why can methanol present with Parkinson’s like sx?
Effects on putamen and sub cortical white matter
Corrected AG equation for albumin
AG + (2.5 x (measured serum albumin)) when albumin is g/dL
Decreased albumin can falsely ? AG?
Elevate
How to calculate osmolarity
2Na + glucose + bun
Normal osmolarity gap?
Measured - calc = 10 (higher = concerning)
Management of methanol toxicity
- ABC
- Na bicarb if ph <7.3: 1-2 new/kg and infuse 150 new/L in 5% dextrose at 1.5-2x maintenance until ph I’d 7.35-7.45
- Fomepezole: load 15mg/kg iv then 10mg/kg q 12,) yo to 48 h thebc15mg/kg q12g
If Hd - same dose as above, start maintenance 6h after loading dose then every 4 hours