ARTERIAL VS SERUM LACTIC ACID DISCREPANCY

Abstract

SESSION TITLE: Unusual Cases and Treatments in the ICU SESSION TYPE: Fellow Case Reports PRESENTED ON: 10/22/2019 3:45 PM - 4:45 PM INTRODUCTION: We are presenting a case where a significant difference was noticed between lactate levels measured by arterial blood gas (ABG) analyzer and serum chemistry analyzer; Lactate gap. Why does that happen? How does it help in supporting a diagnosis and monitoring a treatment? CASE PRESENTATION: A 46-year-old female was brought to the Emergency Department (ED) after her family called 911 for altered mental status and abnormal behavior. Emergency Medical Services personnel found the patient next to an empty bottle of Oxycodone/Acetaminophen and beer cans. In the ED, She was oriented only to person, unable to provide significant history regarding her medication/alcohol consumption. She denied homicidal or suicidal ideation. Few hours later, she progressively became more lethargic prompting intubation for airway protection. Physical exam was within normal limits except for the lethargy and tachypnea. Initial blood workup showed severe high anion gap metabolic acidosis, serum bicarbonate level of 5, anion gap of 24, calculated serum osmolality of 281, measured serum osmolality of 334, making an osmolal gap of 53. Serum lactate 1.2, Serum alcohol, acetone, salicylate and acetaminophen levels were undetectable. ABG, with lactate level, revealed a pH of 7.0, PaCO2 of 13, PaO2 of 151, bicarbonate of 3.2 and lactate of 20. Serial lactate discrepancies were noticed between measuring lactate by the ABG and the serum chemistry analyzers. Due to encephalopathy, high anion gap and osmolar gap, there was a high suspicion that she ingested methanol or ethylene glycol, so she was started on Sodium bicarbonate drip, fomepizole infusion and an emergent hemodialysis was initiated. After 1 session, her mental status improved and was extubated. Lactate gap, anion gap, osmolar gap and metabolic acidemia normalized. DISCUSSION: Ethylene glycol toxicity is known to cause a high anion gap and osmolal gap, especially early in presentation. The new thing to our knowledge, which was confirmed by published literature was that it may cause a lactate gap; a discrepancy between lactate levels measured by the ABG analyzer and the serum chemistry analyzer. This discrepancy is explained by the cross reactivity of the ABG analyzer with glycolate, a byproduct of ethylene glycol, resulting in high ABG lactate levels. This false positive result of lactate gap by the ABG analyzer can help to support the diagnosis of the ethylene glycol toxicity and monitor the treatment, that includes administration of Sodium bicarbonate to correct the severe academia, fomepizole to prevent conversion of ethylene glycol to the toxic metabolites and emergent dialysis to clear these metabolites before they cause acute tubular necrosis resulting in acute renal failure. CONCLUSIONS: Lactate gap noted through discrepancy between Lactate level on ABG and serum chemistry analyzers can be used to diagnose and monitor treatment for Ethylene Glycol toxicity. Reference #1: DOI:https://doi.org/10.1016/S0140-6736(01)06799-X DISCLOSURES: No relevant relationships by Moayyad Alziadat, source=Web Response No relevant relationships by Mohd Hazem Azzam, source=Web Response No relevant relationships by Anish Samuel, source=Web Response