What is Plasmalyte?
Plasmalyte is an isotonic, buffered (balanced) crystalloid intravenous fluid solution with an electrolyte composition that closely mimics human plasma, designed to provide volume resuscitation and maintenance fluid therapy while minimizing acid-base disturbances. 1
Composition and Physiochemical Properties
Plasmalyte contains the following electrolyte composition 1:
- Sodium: 140 mEq/L
- Potassium: 5 mEq/L
- Chloride: 98 mEq/L (significantly lower than normal saline's 154 mEq/L)
- Magnesium: 3 mEq/L
- Acetate: 27 mEq/L (serves as a buffer)
- Gluconate: 23 mEq/L (serves as a buffer)
- Osmolarity: 294-295 mOsm/L (isotonic, similar to plasma's 285 mOsm/L)
- pH: 6.5-7.5
The solution is classified as a balanced crystalloid because its chloride content and ionic composition more closely approximate normal plasma concentrations compared to 0.9% sodium chloride (normal saline). 1 The acetate and gluconate anions are metabolized to bicarbonate, providing additional buffer capacity to address acidosis. 2, 3
Clinical Classification and Use
Plasmalyte is categorized as an isotonic balanced crystalloid solution recommended as first-line fluid therapy for critically ill patients, surgical patients, and those requiring volume resuscitation. 1, 4, 5
Current guidelines from the French Society of Anesthesia and Intensive Care (SFAR) specifically list Plasmalyte alongside 0.9% NaCl and Isofundine as isotonic fluids suitable for vascular filling, with osmolarity ranging from 280-310 mOsm/L. 1 The European Society of Intensive Care Medicine and multiple international guidelines recommend balanced crystalloids like Plasmalyte over normal saline to reduce complications including hyperchloremic metabolic acidosis and acute kidney injury. 4, 5
Advantages Over Normal Saline
Balanced crystalloids like Plasmalyte are preferred over 0.9% saline because they reduce the risk of hyperchloremic metabolic acidosis, acute kidney injury, and may improve mortality outcomes when large volumes are administered. 4, 5
The key advantages include 1, 3:
- Lower chloride load: 98 mEq/L vs 154 mEq/L in normal saline, preventing hyperchloremia
- Buffering capacity: Acetate and gluconate provide bicarbonate precursors to address acidosis
- Physiologic pH: More closely matches plasma pH compared to saline's acidic pH of 5.5
- Electrolyte balance: Contains potassium and magnesium, which are absent in normal saline
Clinical Applications
Plasmalyte is indicated for 1, 4, 5:
- Volume resuscitation in critically ill patients requiring fluid therapy
- Maintenance intravenous fluid therapy in hospitalized patients
- Perioperative fluid management during surgery
- Sepsis and septic shock as part of initial 30 mL/kg crystalloid resuscitation
- Diabetic ketoacidosis as isotonic fluid for initial resuscitation
Important Caveats and Limitations
A potential concern with Plasmalyte is the presence of potassium (5 mEq/L) in patients with hyperkalemia, though evidence suggests this does not cause clinically significant potassium elevation even in at-risk patients. 1 Studies in renal transplant recipients showed that plasma potassium concentrations were comparable between patients receiving balanced fluids and those receiving normal saline. 1
The magnesium content (3 mEq/L) may theoretically affect peripheral vascular resistance and heart rate, though clinical significance remains unclear. 2 This warrants monitoring in patients with severe organ ischemia or hemodynamic instability.
Plasmalyte shares common crystalloid limitations including risk of fluid overload, peripheral edema, pulmonary edema, and potential worsening of intracranial pressure when administered in excessive volumes. 2
Compatibility Considerations
Plasmalyte demonstrates chemical and physical compatibility with most commonly used critical care medications including adrenaline, dobutamine, dopamine, furosemide, morphine, and milrinone. 6 However, midazolam is physically incompatible with Plasmalyte and should not be mixed directly. 6 Furosemide shows reduced chemical stability when mixed with Plasmalyte containing 5% glucose at 24 hours. 6
Evidence Quality and Current Research
Multiple formulations of Plasmalyte exist worldwide (Plasmalyte 148, Plasmalyte A, etc.) with slight variations in composition according to regional preferences. 2, 3 While emerging evidence supports balanced crystalloids over saline for physiochemical outcomes, large randomized controlled trials specifically comparing Plasmalyte to other crystalloids for clinically important outcomes like mortality are ongoing or recently completed. 3, 7 The PLUS study (Plasma-Lyte 148 vs Saline) enrolled 8,800 ICU patients to assess 90-day mortality differences. 7