Lactated Ringer’s (LR) is a balanced crystalloid solution created by Dr. Sydney Ringer in the 1880s using ex-vivo frog hearts. It contains sodium, chloride, lactate, potassium, and calcium to yield an osmolarity of 273 mOsm/L (human plasma is ~ 290 mOsm/L). In the OR and ICU, I preferentially use LR over saline in most cases as a resuscitation and maintenance fluid.
LR provides some degree of intravascular volume expansion to augment perfusion in addition to sodium lactate – a substrate the body can metabolize under stress (ie, ischemia related to hypoperfusion) that, when oxidized in a functional liver, will generate bicarbonate equivalents that can help mitigate metabolic acidosis. Keep in mind that ongoing resuscitation to promote adequate delivery, uptake, and utilization of oxygen is still necessary to clear endogenously produced lactate.
There is some controversy about using LR in patients with hyperkalemia (> 5.5 mEq/L); however, due to potassium’s volume of distribution being larger than the extracellular fluid compartment and equilibration between the intra/extracellular compartments, potassium levels will trend DOWN towards 4 mEq/L (the K+ concentration in LR). Also, these patients tend to be acidotic. A saline (chloride) load can potentially complicate matters with a superimposed non-anion gap, hyperchloremic metabolic acidosis.
Blood products containing citrate as an anticoagulant are almost exclusively run with saline since the calcium in LR can bind to the citrate causing coagulation within IV tubing. In my practice, if I am performing rapid transfusions (ie, “MTP”), I don’t care about the carrier crystalloid since the literature doesn’t conclusively show a difference between saline and LR.
Last, remember we’re NOT infusing lactic ACID. Sodium lactate can be used as a fuel by organs like the heart and produces bicarbonate equivalents (see aforementioned). However, LR CAN affect lactate lab values which I often assess in the OR and ICU (ie, sepsis).
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