Isolyte S

Isolyte® S is a balanced crystalloid solution created by B. Braun Medical Inc. As a cardiothoracic anesthesiologist and intensivist, it’s the crystalloid I use the most in the perioperative and ICU settings. Compared to lactated Ringers, here are the constituents of the two fluids:

Isolyte SLactated Ringers
Sodium (mEq/L)141130
Potassium (mEq/L)54
Chloride (mEq/L)98109
Calcium (mEq/L)3
Magnesium (mEq/L)3
Lactate (mEq/L)28
Gluconate (mEq/L)23
Acetate (mEq/L)27
Osmolarity (mOsm/L)295273
Isolyte S

Although I prefer Isolyte S, I’ll take any balanced crystalloid solution over normal saline! 🙂

Drop me a comment below with questions!

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  1. Hi, I’m not a medical professional, so I really hope I’m not bothering you with my question.

    I’m a cat owner, doing subcutaneous fluids for a Chronic Kidney Disease cat. Can you tell me the difference between Normosol-R and Isolyte S?

    Normosol R
    Balanced electrolyte solution – Sterile, nonpyrogenic
    Balanced electrolyte solution for intravenous use; 100 mL contain:
    Sodium chloride: 0.526 g
    Sodium acetate anhydrous: 0.222 g
    Sodium gluconate: 0.502 g
    Potassium chloride: 0.037 g
    Magnesium chloride: 0.014 g
    Osmolarity (mOsm/L): 295


    Multi-Electrolyte Injection.
    Active Ingredients:

    Magnesium Chloride 30MG / 100ML
    Potassium Chloride 37MG / 100ML
    Potassium Phosphate Monobasic 820mcg / 100ML
    Sodium Acetate 370MG / 100ML
    Sodium Chloride 530MG / 100ML
    Sodium Gluconate 500MG / 100ML
    Sodium Phosphate Dibasic 12MG / 100ML

    pH approx.: 6.5
    Sodium: 140 mEq/L
    Potassium: 5 mEq/L
    Magnesium: 1.5 mEq/L
    Chloride: 98 mEq/L
    Acetate: 27 mEq/L
    Gluconate: 23 mEq/L

    • Admittedly I don’t know anything about veterinary medicine, but both are considered “balanced crystalloids”, basically water with different concentrations of electrolytes and organic compounds (like gluconate and acetate) administered as a means for hydration. I created a table comparing various fluids here.

  2. What is your reasoning for your preference for plasmalyte over LR? I’ve worked with attendings who feel strongly about this too but haven’t been able to find any study comparing the two, I’ve only seen studies comparing one or the other to NS. Thanks in advance!

    • I’m not aware of any studies comparing Isolyte/PlasmaLyte to LR head-to-head. I just feel Isolyte/PlasmaLyte is more physiologic (based on pH, osmolarity, etc.)


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