A 59-year-old female with past medical history of hypertension, type 2 diabetes mellitus, end-stage renal disease (ESRD) on hemodialysis (HD) presented to the emergency department (ED) with a request for routine HD (note: Cook County Hospital has a cohort of patients who routinely receive their HD via the emergency department rather than through an outpatient clinic). Initial vital signs were notable for hypertension but were otherwise unremarkable. The patient denied any symptoms, but reported that her last HD session was more than a week ago. The Renal service was consulted for HD and recommended obtaining labs given her missed HD sessions. The potassium level returned at 8.7 (not hemolyzed).
An ECG was subsequently obtained (Figure 1). An ECG from three months prior was available for comparison (Figure 2).
Figure 2. Baseline ECG from three months prior.
Interpretation (Figure 1):
Rate: 67 bom; Rhythm: likely sinus rhythm; Axis: normal; Intervals: normal PR (120), widened QRS (163), normal QTc (491); P waves: difficult to visualize but present in I, III, aVL; QRS complex: wide; ST Segment/T waves: peaked T waves in precordial leads, inverted T waves with ST depression in leads I and aVL, isolated ST elevation lead III
Interpretation (Figure 2):
Rate: 61 bpm Rhythm: normal sinus rhythm; Axis: normal; Intervals: normal PR (175), normal QRS (89), normal QTc (421); P waves: present, upright in leads I and II, inverted in aVR; QRS complex: unremarkable; ST Segment/T waves: T wave inversions noted in I and aVL, isolated ST elevation lead III
Discussion:
While findings such as T wave inversions and ST depressions are often associated with ischemia, they can also be seen in acute hyperkalemia. In this case, the ECG changes - peaked T waves, a wide QRS complex, and P wave flattening - coupled with the clinical scenario of an ESRD patient who missed multiple HD sessions is highly concerning for hyperkalemia, which was confirmed on lab testing.
Hyperkalemia is a common finding in the ED. The most frequent causes include lab hemolysis (false hyperkalemia), renal failure, medication side effects (e.g. potassium-sparing diuretics, ACE inhibitors/ARBs), adrenal insufficiency, acidosis (e.g. diabetic ketoacidosis), rhabdomyolysis, tumor lysis syndrome, burns, and crush injuries. Symptoms of hyperkalemia range from asymptomatic to severe, up to and including cardiac arrest. Common symptoms include dyspnea, nausea, vomiting, weakness, paresthesias, and chest pain. It’s important to note that hyperkalemic patients may appear stable for a time before suddenly decompensating. As is the case in many medical conditions, the rate of potassium accumulation is often more important than the absolute level. Many ESRD patients live with chronic hyperkalemia that does not require acute treatment in the ED setting.
Hyperkalemia is often called “the great ECG mimicker” due to the variety of ECG changes it can produce. While peaked T waves are the classically taught finding, other ECG changes may include P wave flattening or widening, prolonged PR intervals, bradyarrhythmias (e.g. sinus bradycardia, high-grade AV block, junctional and ventricular escape rhythms, slow atrial fibrillation), new bundle branch blocks or fascicular blocks, QRS widening, or "bizarre" QRS morphology. As Dr. Amal Mattu advises, if you look at an ECG and think, "That looks weird," hyperkalemia should be on your differential. If not promptly treated, patients may progress to the classic "sine wave" appearance, followed by ventricular fibrillation, PEA, or asystole.
The treatment of hyperkalemia centers around three principles: cardiac membrane stabilization, potassium-shifting, and potassium removal. Calcium gluconate is used for cardiac membrane stabilization and is typically administered only when there are associated ECG changes. Potassium-shifting agents help move potassium intracellularly, temporarily lowering blood potassium levels to stabilize the patient until more definitive treatments can take effect. Common potassium-shifting agents include albuterol (10-20 mg nebulized over 30 minutes) and regular insulin (5-10 units IV). Sodium bicarbonate can also shift potassium intracellularly but is primarily used for severe acidosis (pH <6.9) or during cardiac arrest. Potassium removal agents work by diluting or decreasing extracellular potassium levels. These include furosemide (though it is not useful in ESRD patients who no longer produce urine), fluid boluses (to be used with caution in ESRD or fluid-overloaded patients), and sodium zirconium cyclosilicate (Lokelma) or sodium polystyrene sulfonate (Kayexalate), which bind potassium in the GI system. HD remains the definitive treatment for hyperkalemia.
This patient was medically treated for her hyperkalemia with calcium gluconate, insulin, dextrose, and albuterol. A repeat ECG was obtained after medical management, showing significant improvement compared to the initial ECG changes (Figure 3).
Figure 3. ECG after medical management of hyperkalemia.
Interpretation (Figure 3):
Rate: 108; Rhythm: sinus tachycardia; Axis: normal; Intervals: normal PR (157); mild widening of QRS (118); normal QTc (418); P waves: present, upright in leads I and II, inverted in aVR; QRS complex: wide but improved from prior; ST Segment/T waves: T wave inversions in I and aVL with ST depression; Comparison: compared to initial ECG, widened QRS is improving, rhythm now normal sinus rhythm, ST depressions and T wave inversions still present but improving.
The patient underwent urgent same-day HD and was admitted to the hospital for additional HD sessions. The patient did well and was ultimately discharged home with a plan to resume her regularly scheduled HD sessions.
Take Home Points:
Hyperkalemia has a broad spectrum of clinical presentations and should always be considered in HD patients, even if the patient is asymptomatic and especially if there is a history of missed HD sessions.
If there is any concern for ECG changes associated with hyperkalemia, calcium gluconate or calcium chloride should be given immediately.
While peaked T waves progressing to a sine wave is the classically taught ECG finding for hyperkalemia, there is a wide spectrum of ECG findings that can be seen, including peaked T waves, bradyarrhythmias, abnormal QRS complexes, new conduction blocks, and terminal rhythms such as ventricular fibrillation, PEA, and asystole.
Authored by Alexandra Atkins, MD and Ari Edelheit, MD.
References:
Lasure B, Shaver E. Hyperkalemia. In: Johnson W, Nordt S, Mattu A and Swadron S, eds. CorePendium. Burbank, CA: CorePendium, LLC. https://www.emrap.org/corependium/chapter/recEcOnShorJunqD5/Hyperkalemia#h.1m5of1nbx01j. Updated July 6, 2021. Accessed December 18, 2024.
Lindner G, Burdmann EA, Clase CM, Hemmelgarn BR, Herzog CA, Małyszko J, Nagahama M, Pecoits-Filho R, Rafique Z, Rossignol P, Singer AJ. Acute hyperkalemia in the emergency department: a summary from a Kidney Disease: Improving Global Outcomes conference. Eur J Emerg Med. 2020 Oct;27(5):329-337. doi: 10.1097/MEJ.0000000000000691. PMID: 32852924; PMCID: PMC7448835.
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