Lactated Ringer's solution
Lactated Ringer's solution is a solution that is isotonic with blood and intended for intravenous administration. It may also be given subcutaneously. Lactated Ringer's solution is grouped with intravenous fluids known as "crystalloids" – which include saline and dextrose solutions (compared to the "colloids" which contain larger molecules such as starch or gelatine).
Lactated Ringer's solution is abbreviated as "LR", "RL" or "LRS". It is also known as Ringer's lactate solution (although Ringer's solution technically refers only to the saline component, without lactate). It is very similar, though not identical to, Hartmann's solution, which is more commonly found in British and Irish hospitals and has slightly different ionic concentrations.
Lactated Ringer's solution is often used for fluid resuscitation after a blood loss due to trauma, surgery, or a burn injury. It has been used to induce urine output in patients with renal failure.
The IV dose of lactated Ringer's solution is usually calculated by estimated fluid loss and presumed fluid deficit. For fluid resuscitation the usual rate of administration is 20 to 30 ml/kg body weight/hour. Lactated Ringer's solution is not suitable for maintenance therapy because the sodium content (130 mEq/L) is considered too low, particularly for children, and the potassium content (4 mEq/L) is too low, in view of electrolyte daily requirement.
Other commonly used intravenous fluids include normal saline and Hydroxyethyl starch solutions (used in hypovolemic shock). Lactated Ringer's and other crystalloids are also used as vehicles for the IV delivery of drugs. Lactated Ringer's is usually given intravenously.
In a large-volume resuscitation over several hours, LRS maintains a more stable blood pH as compared to isotonic saline.
Physical and chemical properties
One litre of lactated Ringer's solution contains:
- 130 mEq of sodium ion = 130 mmol/L
- 109 mEq of chloride ion = 109 mmol/L
- 28 mEq of lactate = 28 mmol/L
- 4 mEq of potassium ion = 4 mmol/L
- 3 mEq of calcium ion = 1.5 mmol/L
Lactated Ringer's has an osmolarity of 273 mOsm/L. The lactate is metabolized into bicarbonate by the liver, which can help correct metabolic acidosis. Though lactate itself contributes a strong anion and generates protons, lactated Ringer's solution alkalinizes via the sodium cations it leaves behind. They increase the strong ion difference in solution, leading to proton consumption and an overall alkalinizing effect. 
The solution is formulated to have concentrations of potassium and calcium that are similar to the ionized concentrations found in normal blood plasma. To maintain electrical neutrality, the solution has a lower level of sodium than that found in isotonic saline or plasma.
There are slight variations for the composition for Ringer's as supplied by different manufacturers. As such, the term Ringer's lactate should not be equated with one precise formulation.
Although its pH is 6.5, it is an alkalizing solution.
Ringer's saline solution was invented in the early 1880s by Sydney Ringer, a British physician and physiologist. Ringer was studying the beating of an isolated frog heart outside of the body. He hoped to identify the substances in blood that would allow the isolated heart to beat normally for a time. The use of Ringer's original solution of inorganic salts slowly became more popular. In the 1930s, the original solution was further modified by American pediatrician Alexis Hartmann for the purpose of treating acidosis. Hartmann added lactate, which mitigates changes in pH by acting as a buffer for acid. Thus the solution became known as "lactated Ringer's solution" or "Hartmann's solution".
It is used for the treatment or palliative care of chronic renal failure in small animals. The solution can be administered both by IV and subcutaneously. Administering the fluids subcutaneously allows the solution to be readily given to the animal by a trained layperson, as it is not required that a vein be located. The solution is slowly absorbed from beneath the skin into the bloodstream of the animal.
- Intravenous therapy
- Oral rehydration therapy
- Saline (medicine)
- Hartmann's solution
- Tyrode's solution
- Phosphate buffered saline (cell culture)
- Lactated Ringers Package Insert information, side effects and uses
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- Giving Subcutaneous Fluids to a Cat