With the recent publication of the SMART and SALT-ED trials, the chloride rich vs poor (balanced/buffered) crystalloid debate is back in the spotlight after a break post the orginal Yunos JAMA 2012 and SPLIT JAMA 2015. Something I commonly hear from internal medicine residents however is that LR and plasma-lyte should DEFINITELY be avoided in the setting of hyperkalemia, since they contain 4 and 5 meq/L of potassium respectively.
It turns out however that normal saline ( strong ion difference of 0, pH of ~ 5.5) increases potassium more than either of the chloride poor solutions do.
1) Serum potassium level should not be able to exceed 4meq/L (LR) or 5meq/L(PL) since that is the concentration of K in the solution. If a patient’s K is greater than 5, PL will actually lower potassium

2) given how acidic NS is (above), the increased hydrogen ion concentration exchanges with intracellular potassium, actually worsening hyperkalemia despite not having any K in the solution

3) several trials in the peri-op setting have demonstrated increased potassium with NS compared to LR or PL
Image may contain: text
No automatic alt text available.

Jerry Altshuler, Pharm.D., BCPS, BCCCP
Critical Care Pharmacy Coordinator
Director, PGY-2 Critical Care Pharmacy Residency Program 
The Mount Sinai Hospital
1 Gustave L. Levy Place
New York, New York 10029
@hockeypharmd