Normal saline has long been the initial fluid choice for resuscitation in the emergency department and ICUs for many years. It is quick to access, easy to use, and doesn’t have the incompatibility profile of other fluids. Practice has only started to change drastically over the past decade as more data has been published regarding the multiple benefits of using balanced crystalloids (i.e. Lactated Ringers or Plasmalyte) as opposed to normal saline. Lactated Ringers (LR) comes with its own downsides and potential detrimental effects (i.e. incompatibility with blood transfusions because of the presence of calcium). Additionally, the compatibility of LR with various medications is a mysterious topic and will be reserved for a later post. In this post, we are going to review one of the most common misconceptions associated with LR, the data behind it, and how to address it in clinical practice.
Lactated Ringers in Hyperkalemia
I think most of us remember a time, maybe even recently, where we chose LR as our fluid for resuscitation only for that decision to be met by opposition because of hyperkalemia. “You can’t give LR to a patient with hyperkalemia!” they say, because you will theoretically raise their potassium. However, the physiologic basis and data surrounding LR and its overall effect on potassium levels seems to get lost in the argument.
To begin, let’s consider the amount of volume in the entire body. Most texts estimate a given human as being approximately 60% water, which in a 70kg human, gives 42 L of water. The total body water is then divided into intracellular space, an estimated 2/3rds giving 28 L, and extracellular space, an estimated 1/3rd giving 14 L. The extracellular space is further divided into interstitial fluid, an estimated 10.5 L, and plasma, an estimated 2.5 L.
The extracellular space is the important space for measurement of basic electrolytes like potassium and where the levels of certain electrolytes can have their detrimental effects (i.e. hyperkalemia and its effect on cardiac function). When fluids are given to a patient intravenously, the fluid doesn’t stay in the extracellular (read: intravascular) compartment. One look at any patient given excessive fluids or left on prolonged maintenance fluid rates demonstrates it: fluids dissipate across all of the compartments within the body. Therefore, it can be assumed that the volume of LR does not stay in the extracellular space either, which would theoretically cause all of the potassium to remain there and result in the suspected higher potassium concentration. Not only does it physiologically not make sense that LR would raise potassium levels because it doesn’t stay in one compartment, the data demonstrates that it doesn’t as well.
The fantastic minds over at PulmCrit have written about three studies (O’Malley et al, Khajavi et al, and Modi et al) that demonstrated LR is safe to give in hyperkalemia and is probably the better choice. Since 2014, more studies have further examined the effect of different fluids on potassium levels. In a more recent study, Weinberg et al concluded that patients given normal saline developed higher peak potassium levels and required treatment for hyperkalemia more often than those given Plasma-Lyte. What is the difference between Plasma-Lyte and LR? Plasma-Lyte has a higher concentration of potassium at 5 mEq. To top things off, the SMART Trial investigators conducted a secondary analysis specifically examining balanced fluids (LR) versus normal saline in critically ill patients with hyperkalemia or acute kidney injury. They concluded that the use of balanced fluids (LR) was not associated with increased incidence of severe hyperkalemia and may be associated with decreased incidence of new renal replacement therapy.
The clinical reasoning behind avoiding LR in hyperkalemia is flawed at best and the basic physiology explains why and now we have plenty of data to support it. So the next time someone questions your use of LR in a patient, citing hyperkalemia concerns, show them this article.
- LR is SAFE in hyperkalemia and likely preferred over Normal Saline because of the ensuing acidosis caused by large volume chloride infusion leading to worsening extracellular hyperkalemia.
- Furthermore, the potassium concentration in LR does not cause an extracellular rise in potassium levels and is more likely to cause a trend towards 4mEq (the same amount within LR).
- Tobias A, Ballard BD, Mohiuddin SS. Physiology, Water Balance. [Updated 2020 Oct 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK541059/
- O’Malley CMN et al. A Randomized, Double-Blind Comparison of Lactated Ringer’s Solution and 0.9% NaCl During Renal Transplantation. Anesth Analg. 2005;100:1518-1524.
- Weinberg L et al. Effects of intraoperative and early postoperative normal saline or Plasma-Lyte-148 on Hyperkalemia in deceased donor renal transplantation: a double-blind randomized trial. British Journal of Anaesthesia. 2017;119(4):606-615.
- Toporek AH, Semler MW, Self WH, Bernard GR, Wang L, Siew ED, Stollings JL, Wanderer JP, Rice TW, Casey JD; SMART Investigators and the Pragmatic Critical Care Research Group. Balanced Crystalloids versus Saline in Critically Ill Adults with Hyperkalemia or Acute Kidney Injury: Secondary Analysis of a Clinical Trial. Am J Respir Crit Care Med. 2021 May 15;203(10):1322-1325. doi: 10.1164/rccm.202011-4122LE. PMID: 33503391.
- Singh S, Kerndt CC, Davis D. Ringer’s Lactate. [Updated 2021 Apr 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK500033/
- Brinkman JE, Dorius B, Sharma S. Physiology, Body Fluids. [Updated 2020 May 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482447/
- Semler MW, Self WH, Wanderer JP, et al. Balanced Crystalloids versus Saline in Critically Ill Adults. The New England Journal of Medicine. 2018; 378(9):829-839. PMID: 29485925.
- Lewis SR, Pritchard MW, Evans DJ, et al. Colloids versus crystalloids for fluid resuscitation in critically ill people. Cochrane Database Syst Rev. 2018;8(8):CD000567. Published 2018 Aug 3. doi:10.1002/14651858. PMID: 30073665.
- Semler MW, Kellum JA. Balanced Crystalloid Solutions Am J Respir Crit Care Med. 2019; 199(8): 952–960. PMID: 30407838.
- Castera MR, Borhade MB. Fluid Management. [Updated 2020 Apr 2]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532305/
- Shrimanker I, Bhattarai S. Electrolytes. [Updated 2020 Sep 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK541123/
- Wallace HA, Regunath H. Fluid Resuscitation. [Updated 2020 Jun 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534791/