Sashi B.Subhash

Intravenous fluids (IV Fluids), also known as intravenous solutions, are supplemental fluids used in intravenous therapy to restore or maintain normal fluid volume and electrolyte balance when the oral route is not possible. IV fluid therapy is an efficient and effective way of supplying fluids directly into the intravascular fluid compartment, in replacing electrolyte losses, and in administering medications and blood products.

There are different types of IV fluids and different ways on how to classify them.

The most common way to categorize IV fluids is based on their tonicity:

IV solutions can also be classified based on their purpose:

Crystalloid IV solutions contain small molecules that flow easily across semipermeable membranes. They are categorized according to their relative tonicity in relation to plasma. There are three types: isotonic, hypotonic, and hypertonic.

Most IV fluids are isotonic, meaning, they have the same concentration of solutes as blood plasma. When infused, isotonic solutions expand both the intracellular fluid and extracellular fluid spaces, equally. Such fluids do not alter the osmolality of the vascular compartment. Technically, electrolyte solutions are considered isotonic if the total electrolyte content is approximately 310 mEq/L. Isotonic IV fluids have a total osmolality close to that of the ECF and do not cause red blood cells to shrink or swell.

Normal saline solution (0.9% NaCl) or NSS, is a crystalloid isotonic IV fluid that contains water, sodium (154 mEq/L), and chloride (154 mEq/L). It has an osmolality of 308 mOsm/L and gives no calories. It is called normal saline solution because the percentage of sodium chloride dissolved in the solution is similar to the usual concentration of sodium and chloride in the intravascular space. Normal saline is the isotonic solution of choice for expanding the extracellular fluid (ECF) volume because it does not enter the intracellular fluid (ICF). It is administered to correct extracellular fluid volume deficit because it remains within the ECF.

Normal saline is the IV fluid used alongside the administration of blood products. It is also used to replace large sodium losses such as in burn injuries and trauma. It should not be used for heart failure, pulmonary edema, and renal impairment, or conditions that cause sodium retention as it may risk fluid volume overload.

D5W (dextrose 5% in water) is a crystalloid isotonic IV fluid with a serum osmolality of 252 mOsm/L. D5W is initially an isotonic solution and provides free water when dextrose is metabolized (making it a hypotonic solution), expanding the ECF and the ICF. It is administered to supply water and to correct an increase in serum osmolality. A liter of D5W provides fewer than 200 kcal and contains 50g of glucose. It should not be used for fluid resuscitation because hyperglycemia can result. It should also be avoided to be used in clients at risk for increased intracranial pressure as it can cause cerebral edema.

Lactated Ringer’s Solution (also known as Ringer’s Lactate or Hartmann solution) is a crystalloid isotonic IV fluid designed to be the near-physiological solution of balanced electrolytes. It contains 130 mEq/L of sodium, 4 mEq/L of potassium, 3 mEq/L of calcium, and 109 mEq/L of chloride. It also contains bicarbonate precursors to prevent acidosis. It does not provide calories or magnesium and has limited potassium replacement. It is the most physiologically adaptable fluid because its electrolyte content is most closely related to the composition of the body’s blood serum and plasma.

Lactated Ringer’s is used to correct dehydration, sodium depletion, and replace GI tract fluid losses. It can also be used in fluid losses due to burns, fistula drainage, and trauma. It is the choice for first-line fluid resuscitation for certain patients. It is often administered to patients with metabolic acidosis.

Lactated Ringer’s solution is metabolized in the liver, which converts the lactate to bicarbonate, therefore, it should not be given to patients who cannot metabolize lactate (e.g., liver disease, lactic acidosis). It should be used in caution for patients with heart failure and renal failure.

Ringer’s solution is another isotonic IV solution that has content similar to Lactated Ringer’s Solution but does not contain lactate. Indications are the same for Lactated Ringer’s but without the contraindications related to lactate.

The following are the general nursing interventions and considerations when administering isotonic solutions:

Hypotonic IV solutions have a lower osmolality and contain fewer solutes than plasma. They cause fluid shifts from the ECF into the ICF to achieve homeostasis, therefore, causing cells to swell and may even rupture. IV solutions are considered hypotonic if the total electrolyte content is less than 250 mEq/L. Hypotonic IV fluids are usually used to provide free water for excretion of body wastes, treat cellular dehydration, and replace the cellular fluid.

Sodium chloride 0.45% (1/2 NS), also known as half-strength normal saline, is a hypotonic IV solution used for replacing water in patients who have hypovolemia with hypernatremia. Excess use may lead to hyponatremia due to the dilution of sodium, especially in patients who are prone to water retention. It has an osmolality of 154 mOsm/L and contains 77 mEq/L sodium and chloride. Hypotonic sodium solutions are used to treat hypernatremia and other hyperosmolar conditions.

0.33% Sodium Chloride Solution is used to allow kidneys to retain the needed amounts of water and is typically administered with dextrose to increase tonicity. It should be used in caution for patients with heart failure and renal insufficiency.

0.225% Sodium Chloride Solution is often used as a maintenance fluid for pediatric patients as it is the most hypotonic IV fluid available at 77 mOsm/L. Used together with dextrose.

Another hypotonic IV solution commonly used is 2.5% dextrose in water (D2.5W). This solution is used to treat dehydration and decreased the levels of sodium and potassium. It should not be administered with blood products as it can cause hemolysis of red blood cells.

The following are the general nursing interventions and considerations when administering hypotonic IV solutions:

Hypertonic IV solutions have a greater concentration of solutes (375 mEq/L and greater) than plasma and cause fluids to move out of the cells and into the ECF in order to normalize the concentration of particles between two compartments. This effect causes cells to shrink and may disrupt their function. They are also known as volume expanders as they draw water out of the intracellular space, increasing extracellular fluid volume.

Hypertonic sodium chloride solutions contain a higher concentration of sodium and chloride than normally contained in plasma. Infusion of hypertonic sodium chloride solution shifts fluids from the intracellular space into the intravascular and interstitial spaces. Hypertonic sodium chloride IV solutions are available in the following forms and strengths:

Hypertonic sodium chloride solutions are used in the acute treatment of sodium deficiency (severe hyponatremia) and should be used only in critical situations to treat hyponatremia. They need to be infused at a very low rate to avoid the risk of overload and pulmonary edema. If administered in large quantities and rapidly, they may cause an extracellular volume excess and precipitate circulatory overload and dehydration. Therefore, they should be administered cautiously and usually only when the serum osmolality has decreased to critically low levels.  Some patients may need diuretic therapy to assist in fluid excretion. It is also used in patients with cerebral edema.

Isotonic solutions that contain 5% dextrose (e.g., D5NSS, D5LRS) are slightly hypertonic since they exceed the total osmolality of the ECF. However, dextrose is quickly metabolized and only the isotonic solution remains. Therefore, any effect on the ICF is temporary. Hypertonic dextrose solutions are used to provide kilocalories for the patient in the short term. Higher concentrations of dextrose (i.e., D50W) are strong hypertonic solutions and must be administered into central veins so that they can be diluted by rapid blood flow.

Dextrose 10% in Water (D10W) is an hypertonic IV solution used in the treatment of ketosis of starvation and provides calories (380 kcal/L), free water, and no electrolytes. It should be administered using a central line if possible and should not be infused using the same line as blood products as it can cause RBC hemolysis.

Dextrose 20% in Water (D20W) is hypertonic IV solution an osmotic diuretic that causes fluid shifts between various compartments to promote diuresis.

Another hypertonic IV solution used commonly is Dextrose 50% in Water (D50W) which is used to treat severe hypoglycemia and is administered rapidly via IV bolus.

The following are the general nursing interventions and considerations when administering hypertonic IV solutions:

Colloids contain large molecules that do not pass through semipermeable membranes. Colloids are IV fluids that contain solutes of high molecular weight, technically, they are hypertonic solutions, which when infused, exert an osmotic pull of fluids from interstitial and extracellular spaces. They are useful for expanding the intravascular volume and raising blood pressure. Colloids are indicated for patients in malnourished states and patients who cannot tolerate large infusions of fluid.

Human albumin is a solution derived from plasma. It has two strengths: 5% albumin and 25% albumin. 5% Albumin is a solution derived from plasma and is a commonly utilized colloid solution. It is used to increase the circulating volume and restore protein levels in conditions such as burns, pancreatitis, and plasma loss through trauma. 25% Albumin is used together with sodium and water restriction to reduce excessive edema. They are considered blood transfusion products and uses the same protocols and nursing precautions when administering albumin.

The use of albumin is contraindicated in patients with the following conditions: severe anemia, heart failure, or known sensitivity to albumin. Additionally, angiotensin-converting enzyme inhibitors should be withheld for at least 24 hours before administering albumin because of the risk of atypical reactions, such as hypotension and flushing.

Dextrans are polysaccharides that act as colloids. They are available in two types: low-molecular-weight dextrans (LMWD) and high-molecular-weight dextrans (HMWD). They are available in either saline or glucose solutions. Dextran interferes with blood crossmatching, so draw the patient’s blood before administering dextran, if crossmatching is anticipated.

LMWD contains polysaccharide molecules that behave like colloids with an average molecular weight of 40,000 (Dextran 40). LMWD is used to improve the microcirculation in patients with poor peripheral circulation. They contain no electrolytes and are used to treat shock related to vascular volume loss (e.g., burns, hemorrhage, trauma, or surgery). On certain surgical procedures, LMWDs are used to prevent venous thromboembolism. They are contraindicated in patients with thrombocytopenia, hypofibrinogenemia, and hypersensitivity to dextran.

HMWD contains polysaccharide molecules with an average molecular weight of 70,000 (Dextran 70) or 75,000 (Dextran 75). HMWD used for patients with hypovolemia and hypotension. They are contraindicated in patients with hemorrhagic shock.

These solutions are derived from starch and are used to increase intravascular fluid but can interfere with normal coagulation. Examples include EloHAES, HyperHAES, and Voluven.

Gelatins have lower molecular weight than dextrans and therefore remain in the circulation for a shorter period of time.

Plasma Protein Fraction is a solution that is also prepared from plasma, and like albumin, is heated before infusion. It is recommended to infuse slowly to increase circulating volume.

The following are the general nursing interventions and considerations when administering colloid IV solutions:

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The following are the references and sources for this IV fluid guide that you may find interesting or if you want to further your reading:

This theory state that a compound is said to be acid when it produces H+ ions on dissolving in an aqueous solution and forms H3O+ ions when combined with the water molecule.

Now have a look at HBr dissociation in an aqueous solution.

⇒ HBr → H+ + Br–

As on dissolving HBr in an aqueous solution, it dissociates into two ions H+ and Br–. Then, a proton ion(H+) combines with a water molecule and forms H3O+.

⇒ HBr(g) + H2O(l) → H3O+(aq) + Br−(aq)

Also, Arrhenius sate that an acid is a compound that increases the concentration of hydrogen ion(H+) in solution.

In the case of the HBr compound, when dissolved in an aqueous solution it liberates one H+ ion, hence increasing the concentration of hydrogen ion in the final solution.

So, the HBr compound definitely follows all conditions needs to meet for the Arrhenius acid compound. Hence, we can say the HBr is an Arrhenius acid compound.

Now we look for another most important acid-base theory that is the Bronsted-Lowry theory.

This theory states a compound is classified as an acid when it donates the proton to other species and itself forms a conjugate base. And a compound is classified as a base when it accepts the proton from other species and itself forms a conjugate acid.

In short as per Bronsted-Lowry theory–

Let’s check whether HBr fulfills the requirement for classifying as Bronsted-Lowry acid or not.

Consider the reaction of HBr reacting with NH3.

Here, HBr reacts with ammonia and donates the proton which is accepted by NH3 and itself forms Br– conjugate base.

Illustration of above reaction (HBr with NH3):-

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