Symptoms and hazards of hyperkalemia

As the name suggests, hyperkalemia means that the potassium content in the blood exceeds the normal standard. It is usually caused by a sudden and large intake of excessive potassium-containing substances, or other reasons. There are usually no special symptoms, so it is often misdiagnosed or missed, delaying the best treatment time. It is often discovered through electrocardiogram. Once hyperkalemia occurs, you should pay more attention to not being too tired, not doing heavy physical labor, and pay attention to the combination of work and rest. What are the symptoms and dangers of hyperkalemia?

What are the dangers of hyperkalemia ?

1. Effect on cardiac excitability: Similar to the effect on skeletal muscle, in mild hyperkalemia, the [K+i/[K+e ratio decreases, the efflux of K+ from cells during resting period decreases, and the negative value of resting potential decreases, so the excitability of myocardium increases. The decrease in resting potential indicates that the cell membrane is in a partially depolarized state. Therefore, in phase 0 of the action potential, the rate of increase in the membrane potential is slower and the amplitude is smaller. This is because in the partially depolarized state, the fast sodium pore of the membrane is partially inactivated, so the rapid influx of sodium in phase 0 is reduced. When serum potassium rises significantly, myocardial excitability will decrease or even disappear due to the low resting potential, because most or all of the fast sodium pores are inactivated and the heartbeat may stop.

2. Impact on cardiac autonomy: In hyperkalemia, the potassium conductance on the membrane of fast-response autonomic cells in atrial conduction tissue and atrioventricular bundle-Purkinje fiber network increases. Therefore, after reaching the maximum repolarization potential, the outflow of potassium in the cell is faster than normal, while the inflow of sodium is relatively slower, thus slowing down automatic depolarization and reducing autonomy.

3. Effect on cardiac contractility: As mentioned above, the increase in extracellular K+ concentration in hyperkalemia inhibits the influx of Ca2+ during phase 2 of myocardial repolarization. Therefore, the Ca2+ concentration in myocardial cells decreases, the excitation-contraction coupling weakens, and the contractility decreases.

4. Impact on cardiac conductivity: As mentioned above, in hyperkalemia, the rate of rise of the membrane potential in phase 0 of the action potential slows down and the amplitude decreases, so the spread of excitement slows down and the conductivity decreases. Therefore, conduction delay or block may occur in the atrium, between the atrioventricular chambers or within the ventricles. The electrocardiogram shows that the P wave representing atrial depolarization is depressed, widened or disappeared, the PR interval representing atrioventricular conduction is prolonged, the R wave representing ventricular depolarization is reduced, and the QRS complex wave representing intraventricular conduction is widened.

What are the early symptoms of hyperkalemia?

1. Neuromuscular symptoms

In the early stages, there is often numbness in the limbs and around the mouth, extreme fatigue, muscle aches, pale, cold limbs. When the blood potassium concentration reaches 7mmol/L, the limbs become numb and limp, first the trunk, then the limbs, and finally the respiratory muscles are affected, causing suffocation. Central nervous system symptoms may include irritability or confusion.

2. Cardiovascular symptoms

High potassium suppresses the myocardium and reduces myocardial tension, resulting in bradycardia and cardiac enlargement, weakened heart sounds, and prone to arrhythmias, but not heart failure. There are characteristic changes in the electrocardiogram, which are related to the degree of increase in blood potassium.

3. Other symptoms

Hyperkalemia may cause nausea, vomiting, and abdominal pain due to increased release of acetylcholine. Due to the toxic effects of high potassium on muscles, it can cause quadriplegia and respiratory arrest. All hyperkalemias have varying degrees of azotemia and metabolic acidosis, the latter of which can aggravate hyperkalemia.