Intravenous Fluids: Composition and Indications

Crystalloids

Colloids

Dextrose in water (D5W)

(2.5 %, 5 %, 10 %)

Albumin

(5 %, 25 %)

Sodium chloride (NaCl)

(0.225 %, 0.33 %, 0.45 %, 0.9 %, 3 %, 5 %, 7.5 %)

Starches

(Hetastarch 5 %, Pentastarch 10 %)

Ringer’s lactate

Dextrans 40 and 70

Plasmalyte A

Blood products

(whole blood, packed red blood cells, fresh frozen plasma, cryoprecipitate, platelets, blood substitutes or artificial blood)

IV solutions can be isotonic, hypotonic, or hypertonic. In general, isotonic solutions are used to treat extracellular fluid (ECF) volume depletion, hypotonic solutions to replace ECF and intracellular fluid (ICF) water loss, and hypertonic solutions to correct symptomatic hyponatremia. Hypertonic saline is often used in trauma settings because it decreases the intracranial pressure in patients with head trauma and for patients following burns. It is important to know the composition of commonly used crystalloids and colloids before we understand their indications (Tables 4.2 and 4.3).

Table 4.2

Composition of commonly used crystalloid solutions

Solution	Osmolality (mOsm)	Na⁺	Cl⁻	K⁺	Ca²⁺	Lactate	Glucose (g/L)
Solution	Osmolality (mOsm)	(mEq/L)					Glucose (g/L)
Normal saline (0.9 %)	308^a	154	154	–	–	–	–
D5 normal saline (5 % dextrose in 0.9 % NaCl)	586	154	154	–	–	–	50
D5water (D5W)	278	–	–	–	–	–	50
D5 0.225 % NaCl	355	38	38	–	–	–	50
D5 0.45 % NaCl	432	77	77	–	–	–	50
0.45 % NaCl	154	77	77	–	–	–	–
3 % NaCl	1026	513	513	–	–	–	–
Ringer’s lactate	272	130	109	4	3	28	–
Plasma-Lyte A^b	294	140	98	5	–	8	–

^anot corrected for osmotic coefficient, which is calculated as the measured osmolality (using an osmometer) divided by the milliosmoles. For example, the measured osmolality of normal saline is 287 mOsm/kg H₂O. The osmotic coefficient, therefore, is: 287/308 = 0.93

^bcontains in addition Mg²⁺ 3 mEq/L, acetate 27 mEq/L, and gluconate 23 mEq/L

Table 4.3

Composition of commonly used colloid solutions other than blood products

Solution	Osmolality (mOsm)	Na⁺	Cl⁻	Albumin (g/L)	Dextran (g/L)	HES (g/L)	COP (mm Hg)
Solution	Osmolality (mOsm)	(mEq/L)		Albumin (g/L)	Dextran (g/L)	HES (g/L)	COP (mm Hg)
Albumin (5 %)	308	154	154	50	–	–	20
Albumin (25 %)	308	154	154	250	–	–	100
Dextran-40	310	154	154	–	100	–	68
Dextran-70	310	154	154	–	60	–	70
Hetastarch (HES) (6 %)	310	154	154	–	–	60	30

COP = colloid oncotic pressure

Crystalloids

Dextrose in Water

Dextrose in water is available as 2.5, 5, 10, and 50 % (containing 25, 50, 100, and 500 g dextrose in 1 L of water, respectively) solutions. The dextrose is metabolized to water and CO₂, and the water is distributed between ECF and ICF compartments. In clinical management, the most commonly used solution is 5 % dextrose in water, which is usually abbreviated as D5W. This solution provides 170 kcal/L. Pure water causes hemolysis, if given IV; therefore, D5W is given to provide pure water. Glucose is metabolized to CO_2. The indications for dextrose in water solutions are shown in Table 4.4.

Table 4.4

Indications for dextrose in water (D5W)

1.To replace deficits of total body water in treatment of hypernatremia

2. To provide energy and prevent starvation ketosis

3. To treat hypoglycemia

4. To mix with amino acid solution in total parenteral nutrition

5. Do Not give D5W to a patient with syndrome of inappropriate antidiuretic hormone because serum [Na⁺] may become dangerously low

6. Do Not give D5W alone to expand the ECF volume in a hypovolemic patient or to a patient with hypokalemia

Sodium Chloride (NaCl) Solutions

NaCl is available as 0.225, 0.45, 0.9, 3, and 5 % (containing 38.5, 77, 154, 513, and 1250 mEq of Na⁺ and an equal amount of Cl⁻ in 1 L) solutions. About 0.9 % NaCl solution is commonly referred to as normal or isotonic saline, whereas 0.225 and 0.45 % NaCl are called hypotonic fluids. For example, 1 L of 0.45 % saline contains 500 ml of isotonic solution and 500 ml of free water. Therefore, 0.45 % NaCl solution provides more free water than 0.9 % NaCl solution. Since insensible losses are low in electrolytes, hypotonic solutions are generally considered true maintenance fluids. In general, 3, 5, and 7.5 % NaCl are called hypertonic solutions. The indications for NaCl solutions are shown in Table 4.5.

Table 4.5

Indications for NaCl solutions

Isotonic (0.9 %) saline

1. To expand ECF volume in a hypovolemic patient

2. To treat hyponatremia in a hypovolemic patient

3. To treat saline-responsive metabolic alkalosis

4. To treat hypernatremia in a patient with hypotension

5. Preferred solution in a patient requiring contrast study

6. Preferred solution in critically ill patients with shock, ARDS, and at times burned patient

7. Use cautiously in patients with Na⁺ overload such as CHF and liver failure

Hypotonic (0.45 %) saline

1. To maintain basic requirements of Na⁺

2. To treat hypernatremia in a hypovolemic patient who has greater water than solute deficit

3. Do Not use in a patient with hypotonic hyponatremia

Hypertonic (3 %, 5 %, 7.5 %) saline

1. To treat symptomatic hyponatremia

2. To treat trauma patients with head injury

3. To treat hypotension and muscle cramps in hemodialysis patients

ARDS adult respiratory distress syndrome, CHF congestive heart failure

Dextrose in Saline

Dextrose in saline is available as D5 0.225, D5 0.45, and D5 0.9 % solutions. These fluids provide Na⁺, Cl⁻, free water, and 170 kcal/L. The indications are similar to those shown in Tables 4.4 and 4.5.

Balanced Electrolyte Solutions

There are a number of “balanced” electrolyte solutions such as Ringer’s lactate (also called Lactated Ringer), plasma-lyte 148, normosol R, and isolyte S available for use; however, Ringer’s lactate is the most frequently used solution in fluid therapy because of its consideration as physiologic saline . Lactate is converted into HC0₃ ⁻ in the liver. Since Ringer’s lactate contains less Na⁺ than normal saline, it is less effective as a volume expander compared to normal saline. Also, it is not a recommended solution in patients with renal failure because of K⁺. Table 4.6 shows indications for Ringer’s lactate.

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