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Lactated Ringer's solution is a solution that is isotonic with blood and intended for intravenous administration. Veterinary administration may also be subcutaneous.

Lactated Ringer's solution is abbreviated as "LR" or "RL". 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 (Compound Sodium Lactate) Solution, the ionic concentrations of which differ.

One liter 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 .

Generally, the sodium, chloride, potassium and lactate come from NaCl (sodium chloride), NaC₃H₅O₃ (sodium lactate), CaCl₂ (calcium chloride), and KCl (potassium chloride).

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.^[1]

Ringer's saline solution was invented by Sydney Ringer^[2], a British physiologist. The solution was further modified by Alexis Hartmann for the purpose of treating acidosis in children. Hartmann modified the solution by adding lactate which mitigates changes in pH by acting as a buffer for acid. Thus the solution became known as 'Lactated Ringer's Solution' and later, 'Hartmann's solution' ^[3]

Lactated Ringer's Solution is often used for fluid resuscitation after a blood loss due to trauma, surgery, or a burn injury. It is also used to induce urination in patients with renal failure.

Lactated Ringer's Solution is used because the byproducts of lactate metabolism in the liver counteract acidosis, which is a chemical imbalance that occurs with acute fluid loss or renal failure.^[4]

The intravenous 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 high, particularly for children, whereas the potassium content (4 mEq/L) is too low, in view of electrolyte daily requirement.

The presumed fluid volume in a human body is greatest in infants and declines with age. Fluid volumes are smaller in females than males due to differences in average body fat. Total fluid accounts for 60% of male body weight (50% in female); 2/3 of that fluid (40% of the body weight) is in the cells and 1/3 (20% of the body weight) is outside the cells. 5% of the body weight is made up of extracellular fluid inside the blood stream and 15% outside. As muscle holds much more water than fat tissue, total fluid volumes would be greater in an athletic individual than in an obese person of similar weight.

Other commonly used intravenous solutions include normal saline and hespan (used in hypovolemic shock).

Lactated Ringer's is also used as a conduit for the delievery of drugs.

Lactated Ringer's is usually given intravenously, but if a suitable vein is not found, it can be taken orally. The solution is effective when drunk, but has an unpleasant taste.^{[citation needed]}

• Intravenous therapy
• Oral rehydration therapy
• Saline (medicine)
• Phosphate buffered saline (Cell culture)