Background
There are three primary fluids used for resuscitation, each contains varying amounts of potassium per liter (Table 1):
- 0.9% Sodium Chloride (normal saline)
- Lactated Ringer’s solution
- Plasma-Lyte A
Additionally, these fluids contain markedly different amounts of other electrolytes, some of which directly influence their pH (Table 1).
| Solution | Na* | Cl* | K* | Ca* | Lactate* | Acetate* | Osmolarity^ | pH |
|---|---|---|---|---|---|---|---|---|
| Sodium Chloride 0.9% (normal saline) | 154 | 154 | – | – | – | – | 308 | 5.5 |
| Lactated Ringer’s | 130 | 109 | 4 | 2.7 | 28 | – | 273 | 6.5 |
| Plasma-Lyte A | 140 | 98 | 5 | – | 27 | 294 | 7.4 | |
| Blood | 135-145 | 96-106 | 3.5-5 | 8.5-10.5 | 0-1 | NA | 275-295 | 7.35-7.45 |
Table 1: Characteristics of IV fluids vs blood [1-3] (* = mEq/L; ^ = mOsmol/L); note: this is not an exhaustive list of fluid contents
A common question is if the balanced fluids containing potassium (Lactated Ringer’s and Plasma-Lyte A) are safe to use in hyperkalemia patients. The answer is YES! Despite containing potassium, these fluids will still decrease the serum potassium level of a hyperkalemic patient. This is because the potassium concentration in these fluids is lower relative to the patient’s serum potassium level and dramatically lower than the patient’s intracellular potassium concentration.
Evidence
A secondary analysis of the SMART trial did not find a difference in severe hyperkalemia (K ≥7 mEq/L) in hyperkalemic patients that received a balanced fluid (8.5%) vs those that received normal saline (14%) (p=0.24) [4]. The authors concluded that:
Our results suggest that the acid-base effects of isotonic crystalloids are more important for potassium homeostasis than the relatively small amount of potassium in these fluids.
A breakdown of the SMART Trial secondary analysis by Journal Feed summarizes other major findings and concludes, “It’s reasonable to choose LR to treat hyperkalemia over NS.” Lastly, Dr. Josh Farkas provides a succinct summary of this topic in a 2014 EMCrit/Pulmcrit post which is helpful in understanding the interplay between fluid balance and the different replacement options. Additionally, he discusses the potential for normal saline to cause a non-anion gap metabolic acidosis thereby leading to increased serum potassium levels.
Bottom Line
Balanced fluids (Lactated Ringer’s and Plasma-Lyte A) containing potassium can safely be used in patients with hyperkalemia. Given their more neutral pH, they may be preferred over normal saline in some patients.
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References
- Sodium Chloride Injection. Package Insert. Baxter Healthcare Corporation; 2013.
- Lactated Ringers Injection. Package Insert. Baxter Healthcare Corporation; 2019.
- Plasma-Lyte A Injection. Package Insert. Baxter Healthcare Corporation; 2019.
- Toporek, A. H., Semler, M. W., Self, W. H., Bernard, G. R., Wang, L., Siew, E. D., Stollings, J. L., Wanderer, J. P., Rice, T. W., Casey, J. D., & SMART Investigators and the Pragmatic Critical Care Research Group. (2021). Balanced crystalloids versus saline in critically ill adults with hyperkalemia or acute kidney injury: Secondary analysis of a clinical trial. American Journal of Respiratory and Critical Care Medicine. doi: 10.1164/rccm.202011-4122LE. PMID: 33503391.
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