Elevated Potassium levels (Hyperkalaemia)
What is Hyperkalemia and what causes it?
Kalemia, is a measure of potassium concentration in the plasma. This normally ranges from 3.6 to 5 mmol/liter. Kidney disease, and use of certain medications, can cause excessively high serum potassium level (above 5.0 mmol/liter). This is called hyperkalemia, a common electrolyte abnormality. Potassium is involved in nerve transmission, muscle contraction, and kidney function.
Hyperkalemia most often results from increased amounts of potassium intake combined with impaired kidney function. Disorders affecting the kidneys decrease kidney excretion and are the most frequent cause of hyperkalemia. Healthy kidneys have can maintaining normal potassium levels even with high intakes by excreting potassium. However, the ability of kidneys with reduced function to adapt to rapid changes in potassium load, is impaired. Such rapid changes can be caused by eating a lot of potassium rich food. Potassium-rich foods include oranges, bananas, cantaloupes, apricots, peaches, papaya, avocados, potatoes, nuts, beans and chocolate. Some salt substitutes contain potassium and can contribute to hyperkalemia.
Diuretics, which are routinely used by patients with heart failure, may lead to a loss of potassium by the normal kidney which may result low levels of potassium in the blood, termed hypokalemia. Some patients with heart failure receive potassium supplements that are often prescribed routinely along with diuretics. However, if kidney function is poor, an excess intake of potassium supplements may cause hyperkalemia.
Drugs are a very common cause of hyperkalemia through diverse mechanisms. These include drugs frequently used for heart failure and hypertension: e.g. angiotensin converting enzyme inhibitors, angiotensin receptor antagonists, neprilysin inhibitors, aldosterone blockers also called MRAs, β-blockers, digoxin, potassium sparing diuretics (triamterene), the blood thinning drug heparin, and the frequently used over the counter pain killer non-steroidal anti-inflammatory drugs (NSAIDS).
Hyperkalemia may develop intermittently in the presence of known predisposing factors such as chronic kidney disease and heart failure, especially when receiving some of the medications mentioned above. Therefore, patients with heart failure on treatment need to have their blood potassium checked on a regular basis. This is usually done together with kidney function checks, since worsening kidney function is one of the most common causes of hyperkalemia.
What are the consequences of hyperkalemia?
When it develops, mild to moderate hyperkalemia up to 6.5 mmol/liter may cause no symptoms and no immediate problems, but it is associated with a high risk of developing serious heart rhythm disturbances. Severe hyperkalemia (> 6.5 mmol/liter) is a life-threatening medical emergency, requiring immediate attention and medical management. The consequences of hyperkalemia are also affected by other factors such as the presence of heart disease or other blood electrolyte (calcium, magnesium) abnormalities that can increase the risk of heart arrhythmias.
Hyperkalemia can be prevented by frequent monitoring of blood levels, avoiding of potassium rich foods and appropriate dosing of drugs that may lead to hyperkalemia. Often this may mean the use of low doses or stopping certain medication or not stopping. Referral to a dietician may be beneficial in helping to adapt diet in the individual patient.
Hyperkalemia is manageable and reversible directly lowering serum potassium. The type of intervention is determined by the severity of hyperkalemia and associated complications. Acute management for severe hyperkalemia is implemented in the hospital to monitor for complications and includes intravenous therapy and interventions to quickly reduce potassium levels. Occasionally, the rapid removal of potassium from the blood through hemodialysis is required. This is usually only required in patients with severely reduced or absent kidney function.
Long-term interventions include taking way risk factors for hyperkalemia and the administration of therapies that facilitate the removal of potassium from the body. These include dietary potassium restriction and stopping potassium supplements. However, these interventions may not be effective enough to prevent hyperkalemia in patients with heart failure and poor kidney function.
Stopping hyperkalemia-inducing medications that are not essential, such as pain killers, is essential. Several heart failure drug classes may increase the risk of hyperkalemia. This is especially relevant for patients with heart failure and chronic kidney disease who are most prone to developing hyperkalemia.
It has recently been demonstrated that the use of oral, potassium-binding resins in patients with heart failure who develop hyperkalemia despite optimal use of their medications can reduce their potassium levels. The medication works by increasing the amount of potassium that leaves the body through faeces instead of being absorbed into the blood. These agents, taken as a powder with water, are well-tolerated and effective at maintaining long-term normal potassium in patients predisposed to hyperkalemia. Importantly, they enable continued optimal use of beneficial heart failure medications.
