Ringer's solution is the name given to a solution of several salts dissolved in water for the purpose of creating an isotonic solution relative to the bodily fluids of an animal. Ringer's solution typically contains sodium chloride, potassium chloride, calcium chloride and sodium bicarbonate, with the last used to balance the pH. Other additions can include chemical fuel sources for cells, including ATP and dextrose, as well as antibiotics and antifungals.
To produce a standard isotonic solution 6.5 g NaCl, 0.42 g KCl, 0.25 g CaCl2 and 1 mole of sodium bicarbonate is dissolved in one litre of distilled water.
Ringer's solution is frequently used in in vitro experiments on organs or tissues, such as in vitro muscle testing. The precise mix of ions can vary depending upon the taxon, with different recipes for birds, mammals, freshwater fish, marine fish, etc. It may also be used for therapeutic purposes, such as arthroscopic lavage in the case of septic arthritis.
Ringer's solution is named after Sydney Ringer, who in 1882–1885 determined that a solution perfusing a frog's heart must contain sodium, potassium and calcium salts in a definite proportion if the heart is to be kept beating for long. Ringer's solution is frequently used in human medicine in the form of lactated Ringer's solution.