What are the symptoms of low potassium levels?

Low blood potassium can easily lead to hypokalemia, and the indicator for judgment is serum potassium less than 3.5mmol/L. The general cause of this situation is insufficient potassium intake in the food or too much potassium excreted from the body. In some poisonings, such as barium poisoning, low blood potassium can also be caused. We need to know the symptoms of low blood potassium and seek timely treatment when we discover it. So, what are the symptoms of low blood potassium? Let’s take a look below.

The severity of clinical manifestations depends on the degree of potassium deficiency inside and outside the cells and the speed at which potassium deficiency occurs. The symptoms of acute hypokalemia are more severe than those of chronic hypokalemia with the same level of potassium deficiency.

1. Neuromuscular system

Common symptoms are muscle weakness and paroxysmal flaccid paralysis. The latter may precede muscle weakness. Although the attack is related to the absolute level of plasma K+, it is more closely related to the K+ gradient inside and outside the cells. The larger the gradient, the greater the difference between the resting potential and the threshold potential, resulting in reduced muscle excitability. Paralysis may also occur when plasma K+ rises. The attacks are more common at night and after fatigue. The most common muscles affected are the limbs. The muscles of the head and neck are generally not affected, but the respiratory muscles may be affected and breathing difficulties may occur. There may be numbness of the limbs before the attack, followed by fatigue, and finally complete disappearance of autonomous activity. Generally, the symptoms of proximal muscles are slightly milder than those of distal muscles. Patients cannot stand, walk, sit or squat and cannot stand up. Those with milder symptoms can barely stand up by holding on to a support with their hands, but cannot turn over on their own. Painful cramps or hand and foot cramps may also occur. The central nervous system is mostly normal and the patient is conscious. There may be mental symptoms such as apathy, depression, drowsiness, memory and orientation impairment or loss. Cranial nerves are rarely affected, and superficial nerve reflexes are weakened or completely disappeared, but deep tendon reflexes and abdominal wall reflexes are less affected.

2. Cardiovascular system

Low potassium can reduce myocardial excitability and cause various arrhythmias and conduction blocks. Mild cases include sinus tachycardia, premature atrial or ventricular contractions, and atrioventricular conduction block. Severe cases include paroxysmal atrial or ventricular tachycardia, and even ventricular fibrillation. Potassium deficiency can aggravate digitalis and antimony poisoning, and may lead to death. Peripheral peripheral vasodilation and blood pressure may drop. Reduced myocardial tension can cause cardiac enlargement. In severe cases, heart failure occurs and U waves appear on the electrocardiogram, often indicating that the body has lost at least 500mmol/L of potassium.

3. Urinary system

Long-term hypokalemia can damage the renal tubules and cause potassium-deficient nephropathy. The renal tubular concentration, ammonia synthesis, hydrogen secretion and chloride ion reabsorption functions can all be reduced or enhanced. The sodium excretion function or sodium reabsorption function can also be reduced, resulting in metabolic hypokalemia and hypochlorite alkali poisoning.

4. Endocrine and metabolic system

Hypokalemia may cause impaired glucose tolerance. Children with long-term potassium deficiency will have delayed growth and development. In patients with hypokalemia, urinary potassium excretion is reduced (24 hours), but in those caused by renal tubular acidosis and acute renal failure, urinary potassium excretion increases (>40mmol/24 hours).

5. Digestive system

Potassium deficiency can slow down intestinal motility. People with mild potassium deficiency only experience loss of appetite, abdominal distension, nausea and constipation; severe potassium deficiency can cause paralytic ileus.