American Journal of Critical Care. 2004;13: 85-86
A regular feature of the American Journal of Critical Care, the ECG Puzzler addresses ECG interpretation for clinical practice. We welcome letters to the Editors regarding this feature.
Electrolyte Imbalances
By
Mary G. Adams, RN, PhD and
Michele M. Pelter, RN, PhD.
From the School of Nursing at the State University of New York at Buffalo (MGA) and the Department of Physiological Nursing, University of California, San Francisco, Calif (MMP).
Scenario: A relatively healthy 82-year-old man presents with complaints of weakness, occasional confusion, and diarrhea. The only medication he reports taking is a "water pill" (spironolactone) for high blood pressure. However, he admits that although instructed to not eat bananas while taking his "water pill," he has recently returned from a Caribbean cruise where he could not resist eating a banana every day.
Interpretation: Normal sinus rhythm (65 beats per minute), first-degree atrioventricular (AV) block, prior anterior wall infarction, and ST-T contours suggesting hyperkalemia.
Rationale
The criteria for first-degree AV block has been met with a lengthened PR interval greater than .20 seconds (atrial depolarization delays are often seen in early phases of hyperkalemia). In addition, prior anterior wall infarction is evident in leads V2 and V3 because there are no R waves. The peaked T waves on this ECG waveform suggest hyperkalemia. Symmetrical peaking of T waves can be mistaken for hyperacute T waves caused by myocardial ischemia; in hyperkalemia, T-wave abnormalities are global rather than regional, as in ischemia. Characteristic ECG changes occur at various levels of hyperkalemia (serum K > 5.5 mEq/L). At serum potassium levels of 6 mEq/L, the ST segments disappear and the T waves become tall and peaked. At levels of 6.5 mEq/L, the P waves begin to flatten out and widen. Sinus arrest may occur when the serum potassium level reaches about 7.5 mEq/L, and cardiac standstill or ventricular fibrillation may occur when serum levels reach 10 to 12 mEq/L. Given that the patient failed to comply with his dietary restriction of no potassium (no bananas), it is prudent to evaluate the patient for hyperkalemia.
Nursing Actions
Initial management is aimed at normalizing the patient’s serum potassium level (3.5–5.5 mEq/L) either pharmacologically or with dialysis. Careful, continuous cardiac monitoring should be maintained to detect dangerous cardiac arrhythmias. After such measures, attention should be focused on removing potassium from the body and managing the condition that led to hyperkalemia. In this case, given the patient’s affinity for bananas, a non–potassium-sparing diuretic may be more appropriate for the management of his hypertension.
