A 67-year-old woman comes to the emergency department because of severe weakness, fatigue, and non-bloody diarrhea. She has well-controlled diabetes mellitus type 2 and bronchial asthma. The patient used to smoke 1 pack of cigarettes daily for 25 years but quit 10 years ago. She does not use alcohol or illicit drugs. Her medications include glyburide, metformin, albuterol, and fluticasone metered dose inhalers. Her temperature is 37.8 C (100 F), blood pressure is 92/61 mm Hg, pulse is 106/min, and respirations are 32/min. Examination shows no pulmonary or cardiac abnormalities on auscultation. The patient's laboratory tests show the following: The patient's serum creatinine was 1.7 mg/dL 3 months ago. Which of the following is the most appropriate immediate next step?

Question

A 67-year-old woman comes to the emergency department because of severe weakness, fatigue, and non-bloody diarrhea.  She has well-controlled diabetes mellitus type 2 and bronchial asthma.  The patient used to smoke 1 pack of cigarettes daily for 25 years but quit 10 years ago.  She does not use alcohol or illicit drugs.  Her medications include glyburide, metformin, albuterol, and fluticasone metered dose inhalers.  Her temperature is 37.8 C (100 F), blood pressure is 92/61 mm Hg, pulse is 106/min, and respirations are 32/min.  Examination shows no pulmonary or cardiac abnormalities on auscultation.  The patient's laboratory tests show the following:  The patient's serum creatinine was 1.7 mg/dL 3 months ago.  Which of the following is the most appropriate immediate next step?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bed3_6ce3_8f63_03adb65a25d8_MD0005_00 This patient's laboratory studies show acute kidney injury (AKI) with a low bicarbonate level and an increased anion gap. The anion gap is helpful in the interpretation of metabolic acidosis and is obtained using the following formula: Anion gap = Serum sodium - (Serum chloride + Serum bicarbonate) This patient's anion gap can thus be calculated as 142 - (105 + 12), which gives a result of 25, compared to a normal anion gap of around 12. The major causes of high anion gap acidosis can be recalled using the "mud piles" mnemonic (Table). In addition to AKI and likely hypovolemia, this patient's presentation is concerning for metformin-related lactic acidosis. Although lactic acidosis is rare in patients with normal renal function, patients with impaired renal function are at increased risk. Other risk factors for metformin-related lactic acidosis include hypovolemia, severe liver disease, and heart failure. Diarrhea is a common side effect of metformin and may contribute to hypovolemia. In addition to aggressive intravenous (IV) fluid support, this patient should have clarification of acid-base status with an arterial blood gas (ABG) analysis and measurement of lactate and ketone levels. (Choice A) IV insulin and high-flow IV fluids are appropriate management for diabetic ketoacidosis (DKA), which may also cause an elevated anion gap. However, DKA is rare in type 2 diabetes and is typically associated with much higher glucose levels. Subcutaneous insulin would be a more appropriate treatment for this patient's mild hyperglycemia. (Choices C and E) This patient's increased respiratory rate is due to compensatory hyperventilation in response to the metabolic acidosis, and not due to bronchial asthma or pneumonia. In light of normal findings on cardiopulmonary examination, these interventions are not needed. (Choice D) Diarrhea is a common side effect of metformin and usually improves a few days after discontinuation of this medication. Stool evaluation may be indicated if symptoms do not improve promptly. Educational objective: Lactic acidosis is a rare but serious complication of metformin. The risk of metformin-induced lactic acidosis increases with hypovolemia, severe liver disease, renal dysfunction, or heart failure. References: Metformin-associated lactic acidosis requiring hospitalization. A national 10 year survey and a systematic literature review. (http://www.ncbi.nlm.nih.gov/pubmed/23436666)

A 67-Year-Old Woman Comes to the Emergency Department Because of Severe