A 74-year-old woman comes to the emergency department because of an episode of syncope. She has generalized weakness, fever, nausea, dysuria, and urinary frequency. She has a 3-day history of decreased oral intake. She lives alone at home. She does not use tobacco, alcohol, or drugs. Her medications include aspirin, lisinopril, and ibuprofen. Her blood pressure is 102/45 mm Hg and pulse is 48/min. Examination shows dry mucus membranes. The abdomen is mildly tender, soft, and non-distended. Cardiac and lung exam show no abnormalities. The lab studies show: An ECG shows a rate of 48/min, a regular rhythm, wide QRS complexes, and absent P waves. Which of the following is the most appropriate next step in management?

Question

A 74-year-old woman comes to the emergency department because of an episode of syncope.  She has generalized weakness, fever, nausea, dysuria, and urinary frequency.  She has a 3-day history of decreased oral intake.  She lives alone at home.  She does not use tobacco, alcohol, or drugs.  Her medications include aspirin, lisinopril, and ibuprofen.  Her blood pressure is 102/45 mm Hg and pulse is 48/min.  Examination shows dry mucus membranes.  The abdomen is mildly tender, soft, and non-distended.  Cardiac and lung exam show no abnormalities.  The lab studies show:  An ECG shows a rate of 48/min, a regular rhythm, wide QRS complexes, and absent P waves.  Which of the following is the most appropriate next step in management?

Quizplus · Accepted Answer

Explanation: This patient's symptoms of fever, dysuria, and increased urinary frequency as well as a positive leukocyte esterase and nitrites on urinalysis confirm the diagnosis of a urinary tract infection. This patient has had reduced oral intake, which has led to decreased circulating volume and subsequent acute renal failure. The labs show an anion gap acidosis that is secondary to renal failure. However, the most abnormal laboratory value present is the elevated serum potassium. Some of the most common manifestations of hyperkalemia, including weakness and abnormalities in cardiac conduction on ECG, are exhibited in this case. Several factors, including acute renal failure, NSAID use, and lisinopril use have likely contributed to this patient's elevated potassium level. On ECG, hyperkalemia initially manifests as peaked T waves and subsequently as prolongation of the PR interval and QRS complex, disappearance of the P waves, and eventually a sine wave. Various arrhythmias, including sinus bradycardia (as seen in this patient), are also seen with hyperkalemia. 11ec2b69_c095_19d3_8f63_c362a47b8ad9_MD0005_00 In this case, the most appropriate next step in management is intravenous calcium gluconate. Calcium rapidly stabilizes the cardiac membrane potential in patients who have severe ECG manifestations of hyperkalemia (e.g. prolonged PR interval, prolonged QRS interval, or disappearance of P waves). However, the effect of calcium gluconate is short lived, so other treatments are subsequently necessary to lower the serum potassium level. (Choice A) Amiodarone is an antiarrhythmic medication but is not used in the treatment of hyperkalemia-associated arrhythmia. (Choice C) Dobutamine can reduce serum potassium but is not generally used for treatment of hyperkalemia. (Choice D) There is good evidence that sodium bicarbonate is ineffective in treating hyperkalemia even in patients with renal failure and acidosis. A combination of glucose and insulin is more effective to drive potassium intracellularly. (Choice E) Placement of a transvenous pacemaker is impractical when compared to more rapid and less invasive alternatives such as calcium gluconate. Educational objective: Calcium gluconate or calcium chloride is the first line treatment for hyperkalemia if severe ECG manifestations (i.e. ECG changes more severe than peaked T waves) are present. Beta-agonists or a combination of glucose and insulin are then typically given to reduce serum potassium by driving potassium intracellularly. References: Therapeutic approach to hyperkalemia. (http://www.ncbi.nlm.nih.gov/pubmed/12401936) Combined effect of bicarbonate and insulin with glucose in acute therapy of hyperkalemia in end-stage renal disease patients. (http://www.ncbi.nlm.nih.gov/pubmed/8852501)

A 74-Year-Old Woman Comes to the Emergency Department Because of an Episode