Stabilization of the cardiac membrane
Calcium
Calcium directly antagonizes the toxic myocardial effects of
hyperkalemia by reducing the threshold potential of cardiac myocytes
leading to stabilization of the membrane potential, with or without
changing the serum potassium concentration. [22] It is indicated
when serum potassium concentration is > 6.5 mmol/L or when
it is > 6.0 mmol/L with EKG changes. [23] Calcium for
injection is available as the chloride or gluconate salt. Calcium
gluconate is the preferred agent due to the potential for extravasation
with calcium chloride. [24] The suggested dose of calcium gluconate
is 1,000 mg (10 mL of a 10 % solution) infused over 2 to 3 minutes,
with constant cardiac monitoring. The dose can be repeated in 5 to 10
minutes if EKG changes persist. The use of intravenous calcium to treat
arrhythmias in the setting of hyperkalemia is not based on robust
evidence. It was shown to be effective in animal experiments and case
reports. [25-27] However, administration of intravenous calcium is
believed to be an important and life-saving approach in hyperkalemia
with life-threatening EKG changes. [28 29] Peripheral vasodilation,
hypotension, bradycardia, and arrhythmias are noted adverse reactions
with intravenous calcium administration.[30]