Hypokalemia, Hyperkalemia and Echocardiography

(This is really an adult echocardiographer post but it is a subject that I am interested in)

Every echo tech has picked up a requisition with this diagnosis, but what is it and what does it mean when one does an echo?

Hyper, hypo meaning too much or too little respectively, K for potassium and alemia referring to blood concentration. Hyperkalemia is too much extracellular potassium, and conversely hypokalemia is too little extracellular potassium. For an average human, 50 mEq per kg of body weight or 3500mEq (or 3.5-5.5 mEq/L) is considered normal. Hyperkalemia would be levels higher than 5.5mEq/L.

Intracellular potassium levels are significantly higher than extracellular potassium levels and this gradient is created by the sodium/potassium/ATP pump and regulated by renin, aldosterone and angiotensin levels produced by the kidneys, adrenal gland and liver. This gradient or action potential across the cell membrane is responsible for the excitability and signaling of skeletal, smooth and cardiac muscle. The kidneys are primarily responsible for the excretion of excess potassium and the maintenance of potassium homeostasis.

Even small imbalances of serum potassium can have a significant effect on muscle integrity, leading to such symptoms as arrhythmias, muscle pain, weakness, malaise and numbness, and can lead to cardiac arrest.

Renal failure and injuries to the kidneys are the most common cause of potassium imbalances. Kidney failure and heart failure go hand in hand. Congestive heart failure leads to congestion in the kidneys, and decreased renal blood supply leads to a cascade of events that eventually leads to renal failure.

Vise versa, renal failure causes the hormones, which drive blood pressure to go into overdrive, causing the heart to work much harder to pump and adequate supply of blood to the kidneys. This eventually contributes to congestive heart failure.

For the echocardiographer, look for impaired ejection fraction, wall motion defects (heart attack), left ventricular hypertrophy, arrhythmias, diastolic dysfunction and pericardial fluid.