Fluid and Electrolytes - Comprehensive Notes

Fluid and Electrolytes

Normal Structure and Function of Fluids and Electrolytes

• Composition of Body Fluids: Includes total body water (TBW), intracellular fluid, and extracellular fluid (interstitial, intravascular, or transcellular).
• Solutes: Consist of crystalloids and colloids, electrolytes and nonelectrolytes.

Fluid Movement

• Fluid Shifts: Fluids shift back and forth through cell walls and vessel walls to maintain homeostasis.
  • Osmosis: Movement of water from an area of lower solute concentration to an area of higher solute concentration.
  • Diffusion: Movement of solutes from an area of higher concentration to an area of lower concentration.

Types of Fluids

• Isotonic: Equal fluid to particles.
• Hypotonic: Fewer particles to fluid.
• Hypertonic: More particles than fluid.
• Hypervolemic: More fluid to particles.
• Hypovolemic: Less fluid to particles.

Movement of Body Fluids

• Osmosis: The movement of water across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.
• Osmotic Pressure: Force created when two solutions of different concentrations are separated by a selectively permeable membrane.
• Osmolality: Number of osmols per kilogram of solvent.
• Osmolarity: Number of osmols per liter of solvent.
• Tonicity: Level of osmotic pressure of a solution (isotonic, hypertonic, hypotonic).
• Osmotic Pressure (Oncotic Pressure): Osmotic pressure in the intravascular space is controlled by the concentration of plasma proteins, specifically albumin.
• Filtration: Fluid and solutes move together from an area of higher pressure to one of lower pressure due to hydrostatic pressure (force of fluid pushing).

Osmotic vs. Hydrostatic Pressure

• Osmotic Pressure: In blood vessels, plasma proteins like albumin create osmotic pressure that pulls water into the capillaries.
• Hydrostatic Pressure: In capillaries, blood pressure pushes fluid out into interstitial spaces.

Electrolyte Movement and Regulation

• Movement of Electrolytes:
  • Diffusion
  • Filtration
  • Active transport
• Regulation of Electrolytes:
  • Major Cations: Sodium (Na+), magnesium (Mg+), potassium (K+), calcium (Ca2+), and hydrogen (H+).
  • Major Anions: Chloride (Cl−), bicarbonate (HCO3 −), and phosphate (PO43−).

Renin-Angiotensin-Aldosterone System (RAAS)

• Triggers: Drop in blood pressure or fluid volume.
• Process:
  1. Renin release from the kidney.
  2. Renin acts on angiotensinogen (from the liver) to form angiotensin I.
  3. ACE (angiotensin-converting enzyme) release from the lungs.
  4. ACE acts on angiotensin I to form angiotensin II.
  5. Angiotensin II acts on the adrenal gland to stimulate the release of aldosterone.
  6. Aldosterone acts on the kidneys to stimulate reabsorption of salt (NaCl) and water (H2O), leading to water retention.
  7. Angiotensin II also acts directly on blood vessels, stimulating vasoconstriction (narrowing).
• Antidiuretic Hormone (ADH):
  • Prevents excessive urine production (anti-diuresis).
  • Also known as vasopressin.
  • Causes vasoconstriction, increasing blood pressure.

Angiotensin II Effects

• Causes arteries to constrict and increases cardiac output, increasing blood pressure and volume.
• Decreases glomerular filtration rate, resulting in water retention.
• Increases thirst.
• Aldosterone: Causes nephron distal tubules to reabsorb more Na+ and water, which increases blood volume.
• ADH: Mediates insertion of aquaporins into nephron collecting duct cells, resulting in more water reabsorbed into the blood.
  • Increases sodium reabsorption in the medulla of the kidney.

Atrial Natriuretic Peptide (ANP)

• ANP is a hormone antagonistic to the angiotensin pathway.
• ANP decreases blood volume and pressure by:
  • Increasing the glomerular filtration rate.
  • Decreasing reabsorption of Na+ by nephrons.
  • Inhibiting the release of renin, aldosterone, and ADH.

Fluid Imbalances

• Fluid Volume Deficit:
  • Isotonic
  • Hypertonic (Dehydration)
• Fluid Volume Excess:
  • Isotonic
  • Hypotonic (Overhydration)
• Simultaneous Fluid Volume Excess and Deficit:
  • Cirrhosis
  • Edema

Fluid Volume Deficit vs Fluid Volume Excess

• Fluid Volume Deficit: Lose water and sodium.
• Dehydration: Lose water only.
• Fluid Volume Excess: Too much water and sodium (assess lungs for crackles).
• Overhydration: Too much water only (Serum Sodium < 135).

Causes of Hypovolemia (Isotonic FVD)

• Excessive gastrointestinal (GI) loss: vomiting, nasogastric suctioning, diarrhea.
• Excessive skin loss: diaphoresis without water and sodium replacement.
• Excessive renal system losses: diuretic therapy, kidney disease.
• Third spacing: burns.
• Hemorrhage or plasma loss.
• Altered intake: anorexia, nausea, impaired swallowing, confusion, nothing by mouth (NPO) (decreased intake of water and sodium).
• Hyperventilation or excessive perspiration without water replacement.
• Prolonged fever.
• Insufficient water intake (enteral feeding without water administration, decreased thirst sensation, aphasia).
• Excessive intake of salt, salt tablets, or hypertonic IV fluids (causes of dehydration).

Expected Findings in Hypovolemia

• Vital Signs: Tachycardia, thready pulse, hypotension, orthostatic hypotension, decreased central venous pressure, tachypnea (increased respirations), hypoxia.
• Neuromusculoskeletal: Dizziness, syncope, confusion, weakness, fatigue; seizures (rapid/severe dehydration).
• GI: Thirst, dry mucous membranes, dry tongue, nausea, vomiting, anorexia, acute weight loss.
• Renal: Oliguria (decreased production of urine).
• Other Findings: Diminished capillary refill, cool clammy skin, diaphoresis, sunken eyeballs, flattened neck veins, absence of tears, decreased skin turgor.

Laboratory Tests for Hypovolemia

• HCT: Increased in both hypovolemia and dehydration unless the fluid volume deficit is due to hemorrhage.
• Blood Osmolarity: Increased hemoconcentration osmolarity (greater than 295 mOsm/kg).
• Urine Specific Gravity: Dehydration: increased concentration (urine specific gravity greater than 1.030).
• Blood Sodium: Dehydration: increased hemoconcentration (greater than 145 mEq/L).
• BUN: Increased (greater 25 mg/dL) due to hemoconcentration.

Nursing Care for Hypovolemia

• Monitor respiratory rate, effort, and oxygen saturation (SaO2).
• Check urinalysis, CBC, and electrolytes.
• Administer supplemental oxygen as prescribed.
• Measure the client’s weight daily at the same time of day using the same scale.
• Observe for nausea and vomiting.
• Assess postural blood pressure and pulse (check for hypotension and orthostatic hypotension).
• Check neurologic status to determine level of consciousness.
• Assess heart rhythm.
• Initiate and maintain IV access.
• Provide oral and IV rehydration therapy as prescribed.
• Monitor I&O. Encourage fluids as tolerated. Alert the provider to a urine output less than 30 mL/hr.
• Monitor level of consciousness and ensure client safety.
• Observe level of gait stability.
• Encourage the client to use the call light and ask for assistance.
• Encourage the client to change positions slowly (rolling from side to side or standing up).

Overhydration (Fluid Volume Excess)

• Too much fluid in the body, from excessive intake, or ineffective removal from the body.
• Fluid Overload: Excess of fluid or water (with water intoxication).
  • Includes hemodilution, which makes the amount of blood components (blood cells, electrolytes) seem lower.
• Hypervolemia = Fluid Volume Excess (FVE): Excess of water and electrolytes, so that the two are still in the right proportions. For example, excessive sodium intake causes the body to retain water, so that there is too much of both.
• Complications: Severe FVE can lead to pulmonary edema and heart failure.

Causes of Hypervolemia

• Chronic stimulus to the kidney to conserve sodium and water (heart failure, cirrhosis, increased glucocorticosteroids).
• Altered kidney function with reduced excretion of sodium and water (kidney failure).
• Interstitial to plasma fluid shifts (hypertonic fluids, burns).
• Age-related changes in cardiovascular and kidney function.
• Excessive sodium intake from IV fluids, diet, or medications (sodium bicarbonate antacids, hypertonic enema solutions).
• Water replacement without electrolyte replacement, excessive water intake.
• Syndrome of inappropriate antidiuretic hormone (SIADH), which is the excess secretion of ADH.
• Excessive administration of IV D5W; use of hypotonic solutions for irrigations, enemas (causes of overhydration).

Expected Findings in Hypervolemia

• Vital Signs: Tachycardia, bounding pulse, hypertension, tachypnea, increased central venous pressure.
• Neuromusculoskeletal: Confusion, muscle weakness, altered level of consciousness, paresthesias, visual changes; seizures (if severe, sudden hyponatremia/water excess).
• GI: Increased motility, ascites.
• Respiratory: Dyspnea, orthopnea, crackles.
• Other Findings: Pitting edema, distended neck veins, weight gain, skin pallor and cool to touch.

Laboratory Tests for Hypervolemia

• HCT:
  • Hypervolemia: Decreased HCT
  • Overhydration: Decreased HCT = Hemodilution
• Blood Osmolarity: Overhydration: Osmolarity less than 280 mOsm/kg.
• Blood Sodium: Overhydration: Sodium decreased.
• BUN: Decreased.
• Urine Specific Gravity: Less than 1.010 (if not due to SIADH).

Nursing Care for Hypervolemia

• Observe respiratory rate, symmetry, and effort.
• Auscultate breath sounds in all lung fields. Lung sounds can be diminished with crackles.
• Monitor for shortness of breath and dyspnea.
• Check ABGs, SaO2, CBC, and chest x-ray results.
• Position the client in semi-Fowler’s position.
• Monitor and document edema (pretibial, sacral, periorbital).
• Monitor I&O and weight client daily at the same time of day using the same scale.
• Implement prescribed restrictions for fluid and sodium intake.
• Administer supplemental oxygen as needed.
• Reduce IV flow rates.
• Administer diuretics (osmotic, loop) as prescribed.
• Monitor and document circulation to the extremities.
• Reposition the client at least every 2 hr.
• Support arms and legs to decrease dependent edema.

Intravenous Solutions

Isotonic Solutions

• Dextrose 5% in water (D5W):
  • Uses: Fluid loss, dehydration.
  • Special Considerations: Use cautiously in renal and cardiac patients. Can cause fluid overload.
• 0.9% sodium chloride (normal saline) NaCl:
  • Uses: Hypernatremia, shock, blood transfusions, resuscitation, fluid challenges.
  • Special Considerations: Can lead to overload. Use with caution in patients with heart failure or edema.
• Lactated Ringer's (LR):
  • Uses: Dehydration, burns, Lower GI Fluid loss, Acute blood loss, Hypovolemia due to third spacing.
  • Special Considerations: Contains potassium, don't use with renal failure patients. Don't use with liver disease, can't metabolize lactate.

Hypotonic Solutions

• 0.45% sodium chloride (½ normal saline):
  • Uses: Water replacement.
  • Special Considerations: Use with caution.

Hypertonic Solutions

• Dextrose 5% in ½ normal saline:
  • Uses: DKA, Gastric fluid loss from NG or vomiting.
  • Special Considerations: May cause cardiovascular collapse or increased intracranial pressure.
• Dextrose 5% in normal saline:
  • Uses: Later in DKA treatment, Temporary treatment for shock if plasma expanders aren't available, Addison's crisis, Water replacement.
  • Special Considerations: Don't use with liver disease, trauma, or burns.
• Dextrose 10% in water:
  • Uses: Conditions where some nutrition with glucose is required.
  • Special Considerations: Use only when blood sugar falls below 250 mg/dL. Don't use in cardiac or renal patients. Monitor blood sugar levels.

Electrolyte Imbalances

• Hyponatremia: Serum sodium level less than 135 mEq/L.
• Hypernatremia: Serum sodium level greater than 145 mEq/L.
• Hypokalemia: Serum potassium level below 3.5 mEq/L.
• Hyperkalemia: Serum potassium level greater than 5.0 mEq/L.
• Hypocalcemia: Serum calcium level below 9 mg/dL.
• Hypercalcemia: Serum calcium level greater than 10.5 mg/dL.
• Hypomagnesemia: Serum magnesium level below 1.5 mEq/L.
• Hypermagnesemia: Serum magnesium level greater than 2.5 mEq/L.

Hyponatremia (Sodium < 135 mEq/L)

• Signs and Symptoms: Confusion, lethargy, weakness, muscle cramping, seizures, anorexia, nausea, vomiting, serum osmolality <290 mOsm/kg
• Nursing Interventions: Administer IV fluids with Na, encourage foods with Na, monitor V/S’s, I&O, labs (Na and serum osmolality), administer hypertonic IV saline solutions as ordered
• Causes: Diuretics, GI fluid loss (vomiting, diarrhea), profuse diaphoresis, water intoxication, prolonged use of hypotonic IV solutions, SIADH
• Sources: Breads, cheeses, chips, processed meats (lunch meat, hot dogs, bacon, ham), commercially canned foods, table salt

Hypernatremia (Sodium > 145 mEq/L)

• Signs and Symptoms: Thirst, dry sticky mucous membranes, weakness, elevated temp, severe hypernatremia (confusion & irritability, decreased LOC, hallucination & seizures), serum osmolality >290 mOsm/kg
• Nursing Interventions: Monitor V/S’s, LOC, labs, increase water intake, Na restricted diets, administer hypotonic IV solutions as ordered
• Causes: Excess sodium due to excessive sodium intake, hypertonic IV solutions, hypertonic enteral feedings without adequate water. Excessive loss of water due to diarrhea, inadequate intake of water, insensible loss due to fever

Hypokalemia (Potassium < 3.5 mEq/L)

• Signs and Symptoms: Weak, irregular pulse, fatigue, lethargy, anorexia, nausea, vomiting, muscle weakness & cramping, decreased peristalsis, hypoactive bowel sounds, paresthesia, cardiac dysrhythmias
• Nursing Interventions: Monitor V/S’s, especially heart rate and rhythm, labs (K+), cardiac monitor, administer K+ supplements, IV fluids with K+ as ordered. Never IV bolus or IV push K+, encourage foods rich in K
• Causes: fish (not shellfish), whole grains, nuts, broccoli, cabbage, carrots, potatoes with skins, bananas, cantaloupe, oranges, nectarines

Hyperkalemia (Potassium > 5.0 mEq/L)

• Signs and Symptoms: Anxiety, irritability, confusion, muscle weakness, flaccid paralysis, paresthesia, GI hyperactivity, diarrhea, abdominal cramping, cardiac dysrhythmias, cardiac arrest
• Nursing Interventions: Monitor V/S’s, especially heart rate & rhythm, labs (K+), cardiac monitor, limit K+ foods, administer Kayexalate, administer as ordered: glucose & insulin (moves K+ back into cell), dialysis
• Causes: Renal failure, massive trauma, crushing injuries, burns, hemolysis, IV potassium, potassium-sparing diuretics, Acidosis, especially diabetic ketoacidosis

Hypocalcemia (Calcium < 9 mg/dL)

• Signs and Symptoms: Confusion, anxiety, hyperactive reflexes, cardiac dysrhythmias, muscle cramps that progress to tetany & seizures, numbness, tingling of extremities and around the mouth, positive Trousseau’s and Chvostek’s signs
• Nursing Interventions: Monitor heart rate & rhythm, cardiac monitor, implement fall and seizure precautions, administer calcium and vit D as ordered, encourage foods rich in Ca
• Sources: Dark green leafy vegetables, canned salmon, soy products and milk
• Causes: Hypoparathyroidism, Pancreatitis, Vitamin D deficiency, Inadequate intake of calcium-rich foods, Hyperphosphatemia, Chronic alcoholism
  • Calcium role: support bones, nerve signaling, muscle contractions, blood clotting

Hypercalcemia (Calcium > 10.5 mg/dL)

• Signs and Symptoms: Lethargy, stupor, coma, depressed deep muscle strength & tone, dysrhythmias, anorexia, nausea and vomiting, constipation, pathological fractures, kidney stones
• Nursing Interventions: Monitor heart rate & rhythm, cardiac monitor, encourage increased fluids, increase patient activity, including active ROM, restrict Ca foods
• Causes: Prolonged bed rest, Hyperparathyroidism, Bone malignancy, Paget disease, Osteoporosis

Hypomagnesemia (Magnesium < 1.5 mEq/L)

• Signs and Symptoms: Neuromuscular irritability with tremors, disorientation, vertigo and confusion, increased reflexes, tremors, convulsions, positive Trousseau’s and Chvostek’s signs, Tachycardia, elevated BP, Respiratory difficulties, anorexia and dysphagia
• Nursing Interventions: Assess V/S’s, especially heart rate & rhythm, cardiac monitor, assess mental status, change LOC, administer magnesium, assess swallowing before foods, fluids, meds, encourage foods rich in Mg, avoid alcohol, implement seizure precautions
• Sources: Cereal grains, nuts, dried fruit, legumes, green leafy vegetables, dairy, meat, fish and chocolate
• Causes: TPN without magnesium, Nasogastric suction, Prolonged diarrhea, Laxative abuse, Use of diuretics

Hypermagnesemia (Magnesium > 2.5 mEq/L)

• Signs and Symptoms: Warm, flushed appearance, peripheral vasodilation, N/V, drowsiness, lethargy, generalized weakness, decreased deep tendon reflexes, hypotension, dysrhythmias, especially bradycardia & heart block
• Nursing Interventions: Assess V/S’s, especially heart rate & rhythm, cardiac monitor, assess mental status, change LOC, assess neuromuscular status, encourage increased oral intake, increase IV fluids, dialysis, administer loop diuretic as ordered, provide respiratory support as needed, provide low magnesium diet
• Causes: Excessive intake of magnesium-containing antacids or cathartics, TPN with too much magnesium, Prolonged use of intravenous magnesium sulfate, Renal failure, Severe dehydration

Assessment

• Health History: Recent changes in fluid intake, diet, and other lifestyle habits.
• Vital Signs: Pay particular attention to prolonged fever, tachycardia, changes in respirations, and alterations in blood pressure.
• Intake and Output: Oral intake, all fluids and foods that become liquid at room temperature, output (body fluids and drainage that can be measured).
• 24-Hour Fluid Balances: Document intake and output each shift, daily the shift totals are added to obtain the 24-hour balances, note trends over subsequent days
• Weight: A change of 1 kg (2.2 lb) is equivalent to 1 L (1000 mL) of fluid.
• Edema: Pitting edema graded on a 4+ scale:
  • 1+ Slight indentation (2 mm); returns to normal fairly quickly.
  • 2+ Deeper indentation (4 mm); indentation lasts longer.
  • 3+ Obvious indentation (6 mm); lasts several seconds.
  • 4+ Deep indentation (8 mm); remains several minutes

Skin Turgor and Mucous Membranes

• Skin Turgor:
  • Normal fluid balance: Pinched skin returns to normal quickly.
  • Fluid volume deficit: Skin remains tented after release.
  • Less accurate in older adults with decreased skin elasticity.
• Mucous Membranes:
  • Normal: Moist and pink.
  • Severe fluid volume deficit: Dry and sticky, furrows in the tongue; dry, cracked lips

Factors Affecting Fluid, Electrolyte, and Acid–Base Balances

• Age: Infants and elderly more susceptible to fluid imbalances.
• Stress: Increased fluid retention and decreased renal excretion.
• Weight: Total body fluid disproportionate weight in people who are obese.
• Surgery: Preoperative NPO, blood loss, stress, fluid drainage, and postoperative vomiting.
• Medical Conditions: Cardiac, hepatic, renal, and respiratory disorders

Nursing Diagnosis Examples

• Fluid Imbalance: Nausea and vomiting, output greater than intake, dry mucous membranes, urine specific gravity 1.041, urine osmolarity 1080 mOsm/kg
• Fluid Retention: Pulse 116 and bounding, respirations 32 and labored, 3+ pitting edema in the feet, crackles in lungs, weight gain
• Dehydration: Fluid volume loss, weak pulse, tachycardia, thirst

Planning

• Goals are based on returning to or maintaining normal balance.
  • Patient’s mucous membranes will be moist by the end of the shift.
  • Patient will exhibit no pitting edema within 48 hours.
  • Patient will have normal pulse rate by discharge

Implementation and Evaluation

• Monitoring fluid balance and evaluating the impact of disease and effect of treatment on an ongoing basis.
• Vital signs, intake and output measurement, and daily weights provide valuable information about fluid and electrolyte status
• Blood tests are often ordered to monitor fluid, electrolyte, and acid-base balance and to assess the effectiveness of prescribed treatments

Maintaining Fluid and Electrolyte Balance

• Restricting Fluid Intake: Use 50% of the fluid amount during the day when the patient is most active and consumes two meals. The fluid amount is divided further into fluid with meals, between meals, and with medication administration. If fluids are running, subtract them from the fluid restriction.
• Restricting Electrolyte Intake: Sodium restrictions are classified as mild, moderate, or severe. Instruct the patient on the dietary restrictions and common foods to avoid. (canned foods and processed or cured meats)

Oral Replacement of Fluids and Electrolytes

• Fluid Replacement: Patient may need to increase fluid intake to offset losses. At least 50% of the fluid is taken during the day. Avoid caffeine; honor patient preferences when possible.
• Electrolyte Replacement: The two most commonly prescribed supplements are potassium and calcium. With potassium-wasting diuretics, the physician may prescribe a potassium supplement. Inadequate intake of milk, milk products, and vitamin D prompts the need for calcium supplements.

Intravenous Therapy

• IV fluids are considered a medication, therefore follow rights of medication administration.
• IV Route Advantages: Immediate access for fluid and electrolyte maintenance or replacement, faster medication onset and more predictable effect, provides access for supplemental or total nutrition replacement, allows transfusion of blood and blood products to increase oxygen-carrying capacity and reestablish normal oncotic pressure
• IV Site Assessment: Assess for S/S of infiltration

IV Infiltration

• Infusion of IV solution and/or nonvesicant medications into surrounding tissues caused by puncturing of the blood vessel through improper insertion or frequent manipulation of IV catheter.
• S/S: Swelling, tenderness, coolness, and firmness of extremity; blanching of skin, damp dressing, or slowed rate of infusion.
• Intervention: Avoid placing IV in areas of flexion or lower extremities. Assess for signs of infiltration at least Q 2 H and always check for line patency before medication administration. If infiltration is suspected, stop infusion immediately, remove catheter, and assess for extravasation. Apply thermal applications and elevate as appropriate. Outline the area of visible damage with a marker to assess changes. If leaking of tissues occurs, cover area with sterile dressing until leaking subsides. Report grade 3 or 4 infiltrations to PCP. Use opposite extremity when inserting new IV catheter.

Intravenous Solutions

• Crystalloids are divided according to tonicity into hypotonic, isotonic, and hypertonic.
• Choice of IV fluid is according to the purpose of the therapy. Example: Normal Saline Solution, Lactated Ringer Solution
• Colloids are solutions that contain protein or starch. The particles remain intact in the solution and are unable to pass through the capillary membrane and are used to re-establish circulating volume and oncotic pressure (colloid osmotic pressure)

Evaluation

• Continuous evaluation of goals and revision of the care plan are necessary for patients with fluid, electrolyte, and acid-base imbalances.
• Laboratory tests indicate the patient's response to therapy and determine whether changes are needed.
• Assessing measures of fluid balance allows the nurse to identify problems and intervene early to avoid severe or life-threatening complications.