Fluids and Electrolytes

Nursing Considerations: Hypotonic

*Monitor patients for manifestations of fluid volume deficit as fluid is "pulled back" into the cells and out of the vascular space. *In older adult patients, confusion may also be an indicator of a fluid volume deficit. Instruct patients to inform a nurse if they feel dizzy or just "don't feel right." *Never give hypotonic solutions to patients who are at risk for ↑d ICP because of a potential fluid shift to the brain tissue, which can cause or exacerbate cerebral edema. *In addition, don't use hypotonic solutions in patients with liver disease, trauma, or burns due to the potential for depletion of intravascular fluid volume.

Other Hypertonic Fluids

*When dextrose is added to isotonic or hypotonic solutions, the net result can be a slightly hypertonic solution due to the higher solute concentration. Thus, adding D5W to sodium chloride solutions (such as 5% dextrose and 0.45% sodium chloride, and 5% dextrose and 0.9% sodium chloride) or to LR solutions such as D5LR will provide the same electrolytes already discussed for each of those solutions, with the addition of calories. *Plain glucose solutions with a concentration higher than 5%, such as 10% dextrose in water (D10W), are also considered hypertonic. D10W provides free water and calories (340 per liter), but not electrolytes. Twenty percent dextrose in water (D20W) is an osmotic diuretic, meaning the fluid shift it causes between various compartments promotes diuresis. Fifty percent dextrose in water (D50W) is a highly concentrated sugar solution. It's administered rapidly via I.V. bolus to treat patients with severe hypoglycemia.

Isotonic Fluids: Uses

0.9% NaCl and LR are used to replace ECF losses: *GI losses: severe vomiting and/or diarrhea, heavy drainage from GI suctioning *Fistula or wound drainage *Fluid loss from trauma: hemorrhage *Conditions commonly treated with 0.9% sodium chloride include mild hyponatremia, metabolic acidosis (such as DKA), and hypercalcemia. *Patients requiring electrolyte replacement (such as burn patients) will benefit more from an infusion of LR. Either fluid may be used during resuscitation (shock).

Tonicity of IV Fluids

A solution is isotonic when the concentration of dissolved particles is similar or slightly higher to that of plasma. Isotonic solutions have an osmolality between 250 and 340 mOsm/L (usually around 290 to 300). Fluids with osmolalities less than 250 mOsm/L are hypotonic.....meaning too little solute (dissolved particles) for the amount of water (water excess). Fluids with osmolalities greater than 340 mOsm/L are hypertonic....meaning that the concentration of particles is too great or the water content is too little.

Isotonic Fluids: 0.9% NaCl

A solution of 0.9% sodium chloride is simply salt water, and contains only water, sodium (154 mEq/L), and chloride (154 mEq/L). Although the mEqs/L are different than plasma concentrations, it's often called "normal saline solution" because the tonicity is similar to plasma tonicity. Therefore....0.9% sodium chloride is used during resuscitation and the only solution that may be administered with blood products.

Hypokalemia: Manifestations

Alters the resting membrane potential of cells which causes reduced cellular excitability. Most serious problem is the effect on the heart......impairs repolarization which may lead to lethal ventricular dysrhythmias. EKG changes: Flattened or depressed ST-segment, low amplitude (depressed or shallow) T waves, and prominent U waves. May also see: *Bradycardia *PVCs—if frequent, may lead to ventricular dysrhythmias. Skeletal muscle weakness—often observed initially in the legs; paralysis may occur with loss of deep tendon reflexes.

Nursing Considerations: Hypotonic

Be aware of how the fluid shift will affect various body systems. The lower concentration of solute within the vascular space will shift the fluid into the cells and also into the interstitial spaces. Use caution when infusing hypotonic solutions; the ↓ in vascular volume can worsen existing hypovolemia and hypotension, thus causing cardiovascular compromise.

Nursing Considerations: Hypertonic .

Careful monitoring of the patient when administering hypertonic saline solutions because of their potential for causing intravascular fluid volume overload and pulmonary edema. Also, risk of hypernatremia thus careful neuro and v/s monitoring. Because hypertonic solutions can cause irritation, damage, and thrombosis of the blood vessel, some of these solutions should not be administered peripherally. Parenteral nutrition solutions containing final concentrations exceeding 10% dextrose should be administered through a central vascular access device.

Crystalloids vs. Colloids.

Colloids contain large molecules that do not pass through semipermeable membranes, such as capillary walls. When infused, they remain in the intravascular compartment and expand intravascular volume by drawing fluid from extravascular spaces via their higher oncotic pressure. Because they remain in the intravascular compartment, they're also known as volume expanders or plasma expanders. Examples include albumin, dextrans, and hydroxyethylstarches (hetastarch or hespan).

Tonicity of IV Fluids: Hypotonic

Compared with intracellular fluid (as well as compared with isotonic solutions), hypotonic solutions have a lower concentration, or tonicity, of solutes (electrolytes). Hypotonic I.V. solutions have an osmolality less than 250 mOsm/L.

Tonicity of IV Fluids: Hypertonic

Compared with intracellular fluid (as well as with isotonic solutions), hypertonic solutions have a higher tonicity or solute concentration, causing an unequal pressure gradient between the inside and outside of the cells....... contain a higher concentration of sodium and chloride than that normally contained in plasma. Hypertonic fluids have an osmolality of 340 mOsm/L or higher. Considered plasma expanders as they act to increase the circulatory volume....the osmotic pressure gradient draws water out of the intracellular and interstitial spaces, ↑ing intravascular fluid volume.

Crystalloids vs. Colloids

Crystalloids are solutes that are easily mixed and dissolved in a solution. The solutes may be electrolytes or nonelectrolytes, such as dextrose. Crystalloid solutions contain small molecules that flow easily across semipermeable membranes, allowing for transfer from the bloodstream into the cells and body tissues. This may ↑ fluid volume in both the interstitial and intravascular spaces. Crystalloid solutions are distinguished by their relative tonicity (before infusion) in relation to plasma. Tonicity refers to the concentration of dissolved molecules held within the solution.

D5W: isotonic in the bag, hypotonic in the body

D5W is unique in that it may be categorized as both an isotonic and a hypotonic solution. The amount of dextrose in this solution makes its initial tonicity similar to that of intravascular fluid, making it an isotonic solution. But dextrose (in this concentration) is rapidly metabolized by the body, leaving no osmotically active particles in the plasma. When the dextrose is quickly metabolized...the result is the administration of free water, making it a hypotonic solution. The free, unbound water molecules are small enough to pass through membrane pores to the intracellular and extracellular spaces......thus expanding both compartments simultaneously.

Nursing Considerations: Isotonic Fluids

Document baseline vital signs, edema status, lung sounds, and heart sounds before beginning the infusion. Frequently assess the patient's response to I.V. therapy during and after the infusion, monitoring for manifestations of hypervolemia, such as hypertension, bounding pulse, pulmonary crackles, dyspnea/shortness of breath, peripheral edema, jugular venous distention (JVD), and extra heart sounds, such as Sɜ.

Hyperkalemia: Management

Eliminate oral or parenteral K+ intake. ↑ elimination of K+: diuretics, hemodialysis, sodium polystyrene sulfonate (Kayexalate)—oral or rectal: it binds to K+ in exchange for Na+, and the resin is excreted in feces), ↑ fluid intake (enhances renal K+ elimination). Force K+ from ECF to the ICF—IV insulin and glucose (insulin carries K+ into cells while glucose prevents hypoglycemia secondary to insulin administration). Calcium gluconate (prevents cardiac irritability, but does not ↓ K+). Continuous cardiac monitoring and be prepared to manage life-threatening dysrhythmias.

Hypertonic Fluids

Examples include: 3% sodium chloride (3% NaCl), with 513 mEq/L of sodium and chloride. Osmolarity: 1026 mOsm/L. 5% sodium chloride (5% NaCl), with 855 mEq/L of sodium and chloride. Infusion of these hypertonic solutions increase plasma osmolality by raising the serum sodium level. Osmosis comes into play which causes the movement of intracellular and interstitial water into the intravascular space (increasing circulatory volume). These solutions are highly hypertonic and should be used only in critical situations to treat hyponatremia. Give them slowly and cautiously to avoid intravascular fluid volume overload and pulmonary edema.

Hypercalcemia: Manifestations

Excess calcium leads to reduced excitability of both muscles and nerves: -lethargy, weakness -depressed reflexes -confusion, disorientation -stupor, coma -bone pain, fractures -slow HR ventricular dysrhythmias

Calcium 8.6 - 10.2 mg/dl

Functions include: -transmission of nerve impulses -myocardial contractions -blood clotting -formation of teeth and bones -muscle contractions Balance is controlled by the parathyroid hormone, calcitonin (produced by the thyroid gland), and vitamin D.

Hypokalemia: Causes

GI losses: vomiting, diarrhea, NG suctioning. Renal losses: diuretics. Skin losses: diaphoresis. Lost with dialysis. Metabolic alkalosis—K+ shifts into cells in exchange for H+. Inadequate dietary intake (rarely).

Sodium 135 - 145 mEq/L

Highest concentration of the electrolytes. Affects water distribution between ECF and ICF— water follows sodium: -↑d serum Na+ results in water retention. -↓d serum Na+ results in water loss. -By controlling water volume, Na+ controls BP. -Has an important role in the generation and transmission of nerve impulses. -Works with K+ in cardiac depolarization. -Helps regulate acid-base balance.

Hypercalcemia: Causes

Hyperparathyroidism. Malignancy: breast cancer, lung cancer, multiple myeloma, metastatic bone cancer (hypercalcemia due to bone destruction). Thiazide diuretics. Dehydration. Prolonged immobility.

Hyponatremia: Management

Hyponatremia caused by H20 excess—fluid restriction. If symptoms are severe (seizures, etc.): slow IV infusion of hypertonic saline solution (3% NaCl) to restore serum Na+ level while the body is returning to a normal H20 balance.

Hypocalcemia: Causes

Hypoparathyroidism (may be due to surgical removal of a portion or injury to the parathyroid gland during thyroid or neck surgery). Acute pancreatitis—When the pancreas is damaged, diseased or inflamed, amylase and lipase are released into the circulation instead of the small intestine. ↑ serum lipase leads to an ↑ in circulating free fatty acids. These fatty acids combine with calcium ions, thus ↓ing serum calcium levels. Multiple blood transfusions—citrate used to anticoagulate blood binds with calcium. Alkalosis.

Hypotonic Fluids: Uses

Hypotonic fluids are used to treat patients with conditions causing intracellular dehydration, such as diabetic ketoacidosis, and hyperosmolar hyperglycemic state, when fluid needs to be shifted into the cell.

Hypocalcemia: Manifestations

Tetany: -Trousseau's sign -Chvostek's sign -laryngeal stridor. -dysphagia. -numbness/tingling around the mouth or in the extremities. EKG changes: prolonged QT interval that may develop into VT..... due to effects on cardiac contractility.

Hypernatremia: Management .

IV hypotonic solutions may be necessary: infuse slowly—serum Na+ must be reduced gradually to prevent rapid shift of H20 back into cells, which can cause cerebral edema. Goal is to dilute the patient's serum Na+ concentration with Na+ free IV fluids, such as 5% dextrose in H20, and to promote excretion of excess Na+ by administering diuretics. Dietary Na+ should also be restricted.

Hypokalemia: Management

If patients are taking digoxin, they are at risk for developing digoxin toxicity if their serum K+ level is low. K+ replacement, best absorbed orally. ↑ dietary intake, K+ supplements. Never given IV push....always given IV slowly mixed in IV solutions (no more than 20 mEq/50 ml) over one hour. When K+ is given IV, it causes pain in the area of the vein where it is entering. Best administered via central line.

Hypotonic Fluids

Infusing a hypotonic solution into the vascular system causes an unequal solute concentration among the fluid compartments. A hypotonic infusion lowers the serum osmolality within the vascular space, causing fluid to shift from the intravascular space to both the intracellular and interstitial spaces. These solutions will hydrate cells, although their use may deplete fluid within the circulatory system.

Nursing Considerations: Hypertonic..

Instruct patients to notify a nurse if they develop breathing difficulties or if they feel their heart is beating very fast. Hypertonic solutions should not be given to patients with cardiac or renal conditions who are dehydrated. These solutions affect renal filtration mechanisms and can cause hypervolemia. Patients with conditions causing cellular dehydration, such as diabetic ketoacidosis should not be given hypertonic solutions, because it will exacerbate the condition.

Isotonic Fluids: Uses

LR is metabolized in the liver, which converts the lactate to bicarbonate. As an alkalinizing solution, LR may also be administered to patients who have metabolic acidosis. Do not give LR to patients who can't metabolize lactate for some reason, such as those with liver disease or those experiencing lactic acidosis (high lactate levels are seen with sepsis). And....because a normal liver will convert it to bicarbonate, LR shouldn't be given to a patient whose pH is greater than 7.5. Because it contains some potassium, use caution in patients with renal failure.

Isotonic Fluids: LR (Hartmann solution)

Lactated Ringer's (LR), also known as Ringer's lactate or Hartmann solution, is the most physiologically adaptable fluid because its electrolyte content is closely related to the composition of the body's blood serum and plasma. Because of this, LR is another choice for first-line fluid resuscitation for certain patients, such as those with burn injuries. It contains sodium, potassium, calcium, and chloride—K+ replacement is limited.

Nursing Considerations: Isotonic Fluids.

Monitor intake and output, hematocrit, and hemoglobin. Elevate the head of bed at 35 to 45 degrees, unless contraindicated. If edema is present in the lower extremities, elevate the patient's legs. Also monitor for manifestations of continued hypovolemia, including urine output of less than 0.5 mL/kg/hour, poor skin turgor, tachycardia, weak, rapid pulse, and hypotension.

Hypernatremia: Causes

Most commonly caused by the loss of water via the skin, urine, or gastrointestinal (GI) tract—patient becomes dehydrated. Can be caused by excessive Na+ intake (rare)—this is often due to the administration of IV fluids: hypertonic NaCl, excessive isotonic NaCl (during resuscitation), IV sodium bicarbonate. Can also be caused by hypertonic tube feedings without providing H20 supplements. Certain disease states: diabetes insipidus—impaired ADH release from the pituitary or reduced ADH function at the level of the kidneys. May be due to a tumor. hyperaldosteronism—adrenal cortex adenoma that produces excess aldosterone

Hypernatremia: Manifestations

Neurological changes: restlessness, agitation, lethargy, twitching, seizures....can lead to coma. Due to dehydration of brain cells. Hypernatremia also has a direct effect on the excitability and conduction of neurons—more easily activated. Intense thirst, dry swollen tongue and dry mucous membranes. Low urine output.

Osmolality and Osmolarity

Osmolality, which is usually used to describe fluids inside the body, refers to the solute concentration in fluid by weight: the number of milliosmols (mOsm) in a kilogram (kg) of solution. Osmolarity refers to the solute concentration in fluid by number of mOsm per liter (L) of solution. Because 1 L of water weighs 1 kg, the normal ranges are the same and the terms are often used interchangeably. Changes in the level of solute concentration influence the movement of water between the fluid compartments. The normal osmolality for plasma and other body fluids varies from 275 to 295 mOsm/L (or kg).

Review.... Electrolytes and Cardiac Cell Properties

Potassium: controls automaticity and conduction of electrical impulses through the heart. Calcium: exerts a + inotropic affect on the heart. In other words, it causes the cardiac cells to shorten, causing cardiac muscle contraction in response to an electrical stimulus. Sodium: controls excitability; In other words, it allows the cardiac cells to be depolarized (stimulated)—this is necessary for an impulse to be transmitted from one cell to another.

Hyperkalemia: Causes

Renal failure—inability to eliminate K+—most common cause. Excessive K+ intake: salt substitute containing K+, rapid or excessive parenteral administration. Adrenal insufficiency with aldosterone deficiency—inability to eliminate K+. Medications: K+ sparing diuretics, ACE inhibitors. Tissue catabolism (massive cellular destruction)— high fever, burns, sepsis, major trauma. Metabolic acidosis.

Hyponatremia: Manifestations

Symptoms are related to cellular swelling and are first manifested in the CNS.....excess H20 lowers plasma osmolality thus shifting fluid into brain cells. This causes irritability, confusion, dizziness, personality changes, tremors, seizures, and can lead to coma. Generalized edema. Muscle cramps. Weakness.

Potassium 3.5 - 5 mEq/L

The most important cardiac electrolyte..... maintains normal cardiac rhythm by controlling automaticity and conduction of electrical impulses through the heart. Directly affects nerve and muscle function. Helps maintain H20 and electrolyte balance in the body. Has an important role in acid-base balance.

Tonicity and Osmolality

Tonicity describes the concentration of electrolytes (solutes) dissolved in the water, as compared with that of body plasma. Tonicity = osmolality/osmolarity. A fluid exerts predictable effects according to its tonicity: *Isotonic fluids stay in the vessels. *Hypotonic fluids flow into cells. *Hypertonic fluids pull fluid from the cells. Major solutes or determinants of plasma osmolality/osmolarity are Na+ and glucose.

Hypocalcemia: Management

Treat the underlying cause. Calcium replacement: oral (calcium carbonate or citrate) or IV calcium (gluconate). Diet high in calcium rich foods, along with vitamin D supplements.

Hypernatremia: Management

Treat the underlying cause: If hypovolemia is present: restore plasma volume with isotonic saline or colloids. This may be enough to correct the problem. Correction of the underlying cause of the water losses may include withdrawal of loop diuretics, treatment of diarrhea with anti-motility agents or antibiotics, provide of ADH to correct central diabetes insipidus, or use of pharmacologic agents to treat nephrogenic diabetes insipidus.

Hypercalcemia: Management

Treat underlying cause. Promote excretion calcium in urine by administering loop diuretics (furosemide). Hydration with NS. Administer synthetic calcitonin.

Hypotonic Fluids: Uses

Types of hypotonic fluids include: 0.45% sodium chloride (0.45% NaCl), 0.33% sodium chloride, 0.2% sodium chloride, and 2.5% dextrose in water. *Hypotonic solutions assist with maintaining daily body fluid requirements, but do not contain any electrolytes (except for sodium and chloride) or calories (except for D5W, which is also considered a hypotonic solution after metabolism). *Administering hypotonic saline solutions also helps the kidneys excrete excess fluids and electrolytes. All these solutions provide free water, sodium, and chloride, and replace natural fluid losses. In addition, the solution containing dextrose offers a low level of caloric intake.

Hyponatremia: Causes

Water excess from inappropriate use of Na+ free or hypotonic IV fluids—may occur in patients after surgery, major trauma, during administration of fluids to patients in renal failure. Compulsive H20 drinking. Certain disease states (HF) result in dilutional hyponatremia, caused by abnormal retention of H20. Excess Na+ loss from: -GI tract (vomiting, diarrhea, NG suctioning). -Renal losses (diuretics, adrenal insufficiency). -Skin losses (burns, wound drainage).

Hyperkalemia: Manifestations

With mild elevations: leg cramps, muscle weakness, paresthesias. Abdominal cramps and diarrhea occur from hyperactivity of smooth muscles. As K+ level rises: EKG changes...... -tall, peaked T-wave -widened QRS -flat P-wave As condition worsens: -lethal dysrhythmias: VF

Tonicity of IV Fluids: Isotonic

With osmotic pressure constant both inside and outside the cells, the fluid in each compartment remains within its compartment (no shift occurs) and cells neither shrink nor swell. Because isotonic solutions have the same tonicity as plasma, an infused isotonic solution doesn't move into cells. Rather, it remains within the extracellular fluid compartment and is distributed between the intravascular and interstitial spaces, thus ↑ing intravascular volume. Types of isotonic solutions include 0.9% sodium chloride (0.9% NaCl), lactated Ringer's solution (LR), and Ringer's solution.