Case 1: Methanol Intoxication
A 32-year-old male with no significant past history drank a bottle of windshield washer fluid as he was being arrested in an attempt to avoid going straight to jail. He was promptly brought to the emergency department where he was evaluated. His only symptom at the time was nausea without vomiting. He denied chest pain, dyspnea, headache, diaphoresis, and visual disturbances. His blood pressure (BP) was 146/86 mm Hg, temperature (T) 98.7°C, pulse (P) 106 and regular, and respiration (R) 14 rpm. Examination of the head, eyes (including fundi), neck, lungs, heart, chest, abdomen, nervous system, and extremities was entirely normal.
Laboratory data showed serum osmolality 390 mOsm/kg, Na 138 mEq/L, K 6.3 mEq/L, Cl 99 mEq/L, CO2 23 mEq/L, blood urea nitrogen (BUN) 11 mg/dL, creatinine 0.8 mg/dL, and glucose 96 mg/dL. Urinalysis was normal; the methanol level was 227 mg/dL.
The patient was begun promptly on intravenous ethanol and subsequently given fomepizole. The following day he had pH 7.376, Pco2 44.2, Po2 86.9, and HCO3 25.3. His ethanol level was 159.9 mg/dL. Hemodialysis was performed and the methanol level fell to 59 mg/dL. By the following day it had rebounded to 90 mg/dL and a second hemodialysis was performed on day 3, with the methanol level falling to 28 mg/dL. At no time during the hospitalization was the patient significantly acidotic, and his ophthalmologic examination remained normal. He was discharged asymptomatic to jail on the fifth hospital day. This case illustrates that prompt inhibition of alcohol dehydrogenase can entirely prevent both the life-threatening acidosis and the ocular complications. The use of fomepizole eliminates the need for continual monitoring of the patient's ethanol level, which was formerly necessary when ethanol was the only available alcohol dehydrogenase blocker; however, giving fomepizole does not obviate the use of hemodialysis. The course of hospitalization can be considerably shortened by dialyzing out the methanol, even if a second procedure is necessary. Furthermore, if acidosis has set in, dialysis quickly corrects it. In cases of severe methanol intoxication, as in this case, dialysis may avoid the need to give a second dose of fomepizole.
Case 2: Ethylene Glycol Poisoning
A previously healthy 28-year-old man was hospitalized 3 hours after drinking 280 mL of antifreeze containing 95% ethylene glycol. He was tremulous and agitated but not obviously intoxicated. His BP was 137/88 mm Hg, T 98.8°F, P 88 bpm, and R 24 rpm. His head, eyes, neck, lungs, heart, abdomen, neurologic system, and extremities were all normal.
Laboratory data showed serum osmolality 362 mOsm/kg, Na 146, K 4.5, Cl 110, and CO2 11. BUN was 10 mg/dL and creatinine 1.1 mg/dL. Arterial pH was 7.17, Pco2 26, and Po2 105. The serum ethylene glycol level was 303 mg/dL. The urine had no protein, glucose, or cells, but contained numerous envelope- and needle-shaped crystals. The patient was loaded with saline and ethanol and was subsequently hemodialyzed. At no time did the patient show any decrease in renal function. Timed collections of blood and urine for ethylene glycol were performed before and after hemodialysis. Endogenous renal clearance of ethylene glycol was 27.5 mL/minute, while hemodialysis clearance of ethylene glycol was 136.6 mL/minute. By 30 hours after ingestion the patient's ethylene glycol level was zero. The patient was discharged after 72 hours with no target organ damage from the ingestion. This case illustrates that prompt administration of an alcohol dehydrogenase blocker (ethanol or fomepizole) can prevent injury to the kidneys, heart, and brain; hemodialysis clearance of ethylene glycol is about five times greater than the endogenous clearance of the toxin; and because it is so much more efficient, hemodialysis is an important means of rapidly reducing the amount of ethylene glycol and its metabolites in the body and can substantially shorten the hospital stay.
Case 3: Aluminum Intoxication
A 75-year-old female was admitted from another hospital 8 days following irrigation of the bladder with a 1% alum solution (aluminum potassium sulfate) for intractable hemorrhagic cystitis. Her mental status had been impaired from postirrigation day 3 and a serum Al drawn on day 3 was reported 5 days later to be 423 μg/L. Six hours after a 500 mg infusion of deferoxamine she was dialyzed for 4 hours using a 2 M2 high-flux dialyzer for 4 hours. Because of past reports that charcoal hemoperfusion was superior to hemodialysis, she was treated on day 2 with a 4 hour hemoperfusion 6 hours after the same dose of deferoxamine. Total (chelated and nonchelated) Al extraction by the devices was calculated. Although starting at a lower extraction ratio than hemoperfusion (20% versus 38%), hemodialysis had an average extraction ratio of 24% versus an average of 16% because of saturation of the hemoperfusion device (extraction was only 5% at 2 and 4 hours). In addition, the patient had no changes in platelets during hemodialysis, but profound thrombocytopenia after hemoperfusion. The patient was subsequently treated with chelation and hemodialysis alone. This illustrates the need to reappraise older literature in light of improvements in dialysis.
Case 4: Salicylate Poisoning
A 22-year-old college student was found wandering in the residence hall. She was examined at the student health center where she was found to be irritable, confused, tachypneic, and mildly hypotensive. Her roommate called the student health center to report that the patient had just broken up with her boyfriend, and that she had found some pills lying on the bathroom floor and an empty aspirin container. This prompted transfer of the patient to a tertiary care center where she was found to be acidemic (pH 7.24) and hypokalemic, with a salicylate concentration of 75 mg/dL. Shortly after admission it was noticed that she was somnolent. This prompted admission to the medical intensive care unit where hemodialysis was performed via a femoral vein catheter. Within 2 hours her acidosis had improved (pH 7.34) and the salicylate concentration was 35 mg/dL and by 4 hours her pH was 7.4 and the salicylate concentration was 20 mg/dL. Dialysis was discontinued. This case illustrates that central nervous system (CNS) changes in the presence of acidemia reflect CNS trapping of salicylate and an urgency to correct the pH with bicarbonate dialysate and that salicylate is an ideally dialyzable drug (although protein binding is high, the bond is weak and the molecule traverses dialysis membranes easily).
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