When to use Plasmalyte (multiple electrolyte solution), its indications, contraindications, effect on plasma volume, and comparison to Ringer's lactate (RL) (lactated Ringer's solution) and normal saline (NS) (sodium chloride solution) in terms of plasma sodium levels?

Plasmalyte: Indications, Contraindications, and Comparison to RL and NS

Primary Indications

Plasmalyte is indicated as a source of water and electrolytes or as an alkalinizing agent, and should be used as a first-line balanced crystalloid for resuscitation in severe dehydration, shock, or when oral rehydration fails. 1

• For severe dehydration with shock or altered mental status: Isotonic intravenous fluids including lactated Ringer's and normal saline (and by extension, balanced crystalloids like Plasmalyte) should be administered when oral rehydration solution (ORS) therapy fails or in the presence of ileus 2
• As a balanced crystalloid alternative to normal saline: Plasmalyte is commonly used as an isotonic maintenance or resuscitation fluid 3
• For diabetic ketoacidosis (DKA): Balanced crystalloids (including Plasmalyte) result in faster DKA resolution compared to saline, with median time to resolution of 13.0 hours versus 16.9 hours with saline 4

Contraindications

The only absolute contraindication is known hypersensitivity to the product. 1

Relative Contraindications and Cautions:

• Severe head trauma or traumatic brain injury: While Plasmalyte is theoretically isotonic (294 mOsm/L), buffered isotonic solutions should be used cautiously in neurosurgical patients 2, 3. The 2024 perioperative guidelines note that buffered isotonic solutions like Plasmalyte might be better than saline as they avoid hyperchloremic acidosis, but recommend 0.9% saline as first-line for TBI 2
• Magnesium-sensitive conditions: Most Plasmalyte formulations contain magnesium (3 mEq/L), which may affect peripheral vascular resistance, heart rate, and potentially worsen organ ischemia 5, 3
• When dextrose is required: Plasmalyte contains 0 g/dL glucose; if both balanced electrolytes and dextrose are needed, separate dextrose administration or alternative solutions must be used 3

Effect on Plasma Volume

Plasmalyte expands plasma volume similarly to other isotonic crystalloids, with the same limitations of fluid overload, edema, and weight gain. 5

• As a crystalloid solution, Plasmalyte distributes throughout the extracellular space, with only approximately 25-30% remaining intravascular after equilibration
• Shares the same volume expansion characteristics as other crystalloids: potential for fluid overload, peripheral edema, pulmonary edema, and worsening intracranial pressure 5
• The osmolarity of 294 mOsm/L makes it near-isotonic, minimizing osmotic shifts 3

Effect on Plasma Sodium

Plasmalyte maintains plasma sodium more physiologically than normal saline, with sodium content of 140 mEq/L that closely mimics human plasma. 3

Comparison of Sodium Content:

• Plasmalyte: 140 mEq/L sodium, 98 mEq/L chloride 3
• Lactated Ringer's: 130 mEq/L sodium, 108 mEq/L chloride 6
• Normal Saline: 154 mEq/L sodium, 154 mEq/L chloride 6

Acid-Base Effects on Sodium Balance:

Plasmalyte prevents hyperchloremic metabolic acidosis that occurs with normal saline, which indirectly affects sodium handling. 7, 4

• In dehydrated ED patients receiving 2 hours of rapid infusion, Plasmalyte increased bicarbonate levels (23.4 to 24.4 mM/L) while normal saline decreased bicarbonate (23.1 to 21.5 mM/L) and lowered pH (7.40 to 7.36) 7
• The acetate buffer (27 mEq/L) in Plasmalyte is converted to bicarbonate, providing alkalinizing capacity without causing acidosis 5, 3
• All three solutions (NS, LR, Plasmalyte) maintained sodium levels without significant changes during acute resuscitation 7

Comparison: Plasmalyte vs Lactated Ringer's vs Normal Saline

Osmolarity and Tonicity:

• Plasmalyte: 294 mOsm/L (near-isotonic) 3
• Lactated Ringer's: 273-277 mOsm/L (slightly hypotonic) 6
• Normal Saline: 308 mOsm/L (isotonic) 6

Key Clinical Differences:

For traumatic brain injury: 0.9% saline is recommended as first-line over both Plasmalyte and lactated Ringer's, as lactated Ringer's is hypotonic when real osmolality is measured and should be avoided in severe head trauma 2, 6

For general resuscitation and critical illness: Balanced crystalloids (Plasmalyte or lactated Ringer's) are increasingly preferred over saline based on recent evidence 8

For diabetic ketoacidosis: Balanced crystalloids (including Plasmalyte) are superior to saline, resulting in faster DKA resolution and shorter insulin infusion duration 4

Electrolyte Composition Advantages:

Plasmalyte has the most physiologic electrolyte composition, most closely mimicking human plasma. 3, 5

• Plasmalyte uniquely contains: Potassium (5 mEq/L), magnesium (3 mEq/L), and acetate buffer (27 mEq/L) 3
• Lactated Ringer's contains: Potassium (4 mEq/L), calcium (0.9 mmol/L), and lactate buffer (27.6 mmol/L) 6
• Normal saline contains: Only sodium and chloride in supraphysiologic concentrations 6

Acid-Base Effects:

Both Plasmalyte and lactated Ringer's prevent the hyperchloremic metabolic acidosis caused by normal saline. 7, 8

• Normal saline causes hyperchloremic metabolic acidosis even with moderate volumes 7, 8
• Balanced crystalloids have fewer adverse effects on acid-base balance due to lower chloride content and buffer capacity 8
• The balanced Na+:Cl- ratio in Plasmalyte and lactated Ringer's more closely resembles plasma compared to normal saline 6

Clinical Outcomes Data:

Recent large randomized trials suggest balanced crystalloids may reduce mortality and acute kidney injury compared to saline in critically ill adults. 8

• Observational studies in critically ill adults have associated balanced crystalloids with lower rates of acute kidney injury and death 8
• However, one 2024 retrospective study in SICU trauma patients showed longer hospital and ICU length of stay with Plasmalyte versus lactated Ringer's, though patients receiving Plasmalyte were more critically ill (higher APACHE II scores, more mechanical ventilation) 9
• No mortality difference was found between Plasmalyte and lactated Ringer's in trauma patients 9

Clinical Algorithm for Fluid Selection

Use this approach to select the appropriate crystalloid:

1. Traumatic brain injury or severe head trauma: Use 0.9% saline as first-line 2, 6

2. Diabetic ketoacidosis: Use balanced crystalloids (Plasmalyte or lactated Ringer's) over saline 4

3. General resuscitation, severe dehydration, shock: Use balanced crystalloids (Plasmalyte or lactated Ringer's) as first-line 2, 8

4. When dextrose is required: Cannot use Plasmalyte alone; must add separate dextrose or use alternative solution like D5 lactated Ringer's 3

5. Magnesium-sensitive conditions: Consider lactated Ringer's over Plasmalyte to avoid magnesium content 5

6. Neurosurgery (non-trauma): Buffered isotonic solutions like Plasmalyte may be preferred over saline to avoid hyperchloremic acidosis and renal effects, though evidence is limited 2