Setting: ED
CC: “I feel drunk.”
VS: BP: 110/70 mm Hg; P: 84 beats/minute; T: 100.2°F; R: 24 breaths/minute
HPI: A 28-year-old man is brought to the ED by his friends because he tried to kill himself with something he drank in the garage. The patient is clearly drunk and unable to provide a clear history. It is not clear how much vodka he may have drunk as well.
PMHX:
Depression
Medications:
Alprazolam
Paroxetine
Orders:
Naloxone, thiamine, dextrose
PE:
General: disoriented, visibly intoxicated
HEENT: red eyes, hard to visualize retinas
Neurologic: unable to complete the examination because of inability to cooperate
Abdomen: soft, nontender
Interval History: “No response to naloxone/dextrose. Patient remains disoriented with mental status changes.”
Initial Orders:
CHEM-7
UA
Complete blood count (CBC)
Urine toxicology screen
Serum osmolarity
Delirium Etiology
• Sodium level up/down
• Glucose level down
• Calcium level up
• Osmolar changes
• Liver or renal failure
• Hypoxia
Altered mental status is one of those symptoms for which treatment is started before getting tests.
The worst form of confusion is a seizure.
On CCS, do not get a neurology consultation until after these simple tests have been done. You are not supposed to need a neurology consultation to know to check the levels of calcium, glucose, oxygen, sodium, and to test for liver or renal failure.
Move the clock forward only far enough to get the test results. You will not know what type of hospital admission you need for this patient until you know the severity of his illness.
Reports:
CHEM-7:
Sodium 140 mEq/L
Glucose 90 mg/dL
Chloride 100 mEq/L
BUN 9 g/dL
Bicarbonate: 16 mEq/L (normal 22–26 mEq/L)
UA: No white blood cells (WBCs), “envelope-shaped” crystals present
CBC: WBCs 14,200/μL; 78% neutrophils
Urine toxicology screen: no cocaine, opiate, marijuana, benzodiazepines
Serum osmolarity 360 mOsm/kg
Serum Osmolarity = 2 × Sodium + Glucose/18 + BUN/2.8
Which laboratory test result tells you that there must have been a toxic ingestion?
a. WBC count elevation
b. Osmolar gap
c. Metabolic acidosis
d. Decreased anion gap
Answer b. Osmolar gap
The measured osmolarity is 360 mOsm/kg.
The calculated osmolarity is 287 mOsm/kg.
The difference between the osmolarity you measure and the osmolarity you calculate means that there must be an additional toxic substance in the bloodstream. A mild elevation in WBC could mean very little. Any form of “stress” for the body can lead to a mild elevation in WBC count. Fifty percent of WBCs are in circulation and 50% are on the “margins” or edges of the blood vessels. It is easy to double the WBC count just from “stress.” Also, this patient has an increased anion gap of 24 mmol/L, not a decreased anion gap. The normal gap is 6 to 12 mmol/L. Ethylene glycol leads to the increase in osmolar gap.
Envelope crystals are calcium oxalate.
Stress Leukocytosis
• Epinephrine
• Cortisol
Both pull WBCs off the endothelial lining.
Which of these would not be a cause of this metabolic acidosis?
a. Diarrhea
b. Sepsis
c. Hypotension
d. Methanol
e. Ethylene glycol
Answer a. Diarrhea
Diarrhea causes a GI tract loss of bicarbonate with an increased serum chloride. This is why diarrhea and renal tubular acidosis (RTA) have normal anion gaps. An increased anion gap in metabolic acidosis results from the insertion, or addition, of a new substance into the body. This decreases the bicarbonate and does not allow the chloride to rise.
Any form of hypoperfusion or hypotension increases lactate production. Methanol increases formic acid and is the insertion of a new anion.
Methanol Poisoning
• Increased anion gap
• Toxic to the eye and retina
• “Blind drunk”
• Fomepizole for drug therapy
• Dialysis to remove
Isopropyl alcohol: normal anion gap acidosis
Alcohol dehydrogenase metabolizes methanol to formic acid (Figure 11-2). Formic acid burns the eye.
Figure 11-2. A. Metabolism of methanol. B. Metabolism of ethylene glycol. NAD+, oxidized form of nicotinamide adenine dinucleotide; NADH, reduced form of nicotinamide adenine dinucleotide. (Reproduced with permission from Tintinalli JE, et al. Tintinalli’s Emergency Medicine, A Comprehensive Study Guide, 7th ed. New York: McGraw-Hill; 2011.)
Metabolic Acidosis + Elevated Gap + Envelope Crystals = Ethylene Glycol
All patients who have metabolic acidosis need an ABG assay to determine the severity of decrease in pH. You should wait for the ABG results and ethylene glycol level to start treatment.
Orders:
ABG
Ethylene glycol level
Calcium levels
Repeat CHEM-7
Why is ethylene glycol toxic to renal function?
a. Hydrogen ions damage the glomerulus.
b. Ethylene glycol causes sloughing of the proximal tubule cells.
c. Oxalic acid and glycolic acid have direct cytotoxic effects.
d. Ethylene glycol lowers calcium levels.
e. The mechanism is unknown.
Answer c. Oxalic acid and glycolic acid have direct cytotoxic effects.
The entire point of the basic science correlate of this case is knowing that it is the metabolite of ethylene glycol and methanol that causes their toxic effects. Ethylene glycol is not directly toxic to the kidney. Ethylene glycol is metabolized to glycolic acid and oxalic acid. It is the metabolites that are dangerous to the kidney tubules by their direct cytotoxic effects.
Gastric lavage is never the correct treatment for toxic alcohols.
The patient remains intoxicated and difficult to interview.
Reports:
ABG: pH 7.34; PCO2 24 mm Hg; PO2 90 mm Hg
Ethylene glycol level: elevated
Calcium levels: 6.5 mg/dL (decreased)
Repeat chemistry: serum bicarbonate 18 mEq/L; creatinine 1.7 mg/dL
Renal toxicity takes 1 to 2 days after the ingestion of ethylene glycol.
Calcium complexes with oxalic acid
• Lowers blood calcium levels
• Precipitates in the kidneys
Orders:
Fomepizole
Bicarbonate drip if pH < 7.2
Transfer to ICU
Fomepizole
• Blocks alcohol dehydrogenase
• Prevents production of oxalic acid from ethylene glycol
• Prevents formic acid production from methanol
The patient is moved to the ICU if there is severe metabolic acidosis (pH < 7.2) or an overdose bad enough to need:
Bicarbonate drip
Fomepizole
Dialysis
• Fomepizole inhibits alcohol dehydrogenase.
• Alcohol dehydrogenase makes toxic metabolites.
• Only dialysis removes toxic alcohol from the blood.