Fluid and Electrolyte Balance

Fluid and Electrolyte Balance

• Fluid, electrolyte, and acid-base balances are key for normal body function.
• Homeostasis is synonymous with equilibrium within the body.
• Balances are maintained by the renal, pulmonary, and buffer systems.
• Factors causing imbalances include altered intake, illness, and excessive losses.
• Imbalances impact physiological processes at cellular, tissue, and system levels.

Distribution of Body Fluids

• The body is composed of 60% water.
• Muscle has a higher percentage of water compared to fat.
• Intracellular fluid (ICF) refers to fluids within cells.
• The majority of fluid in body is ICF.
• Extracellular fluid (ECF) denotes fluid outside of cells.
• Interstitial fluid exists between cells in tissue.
• Intravascular fluid refers to blood plasma.
• Transcellular fluid is separated by epithelium.
• Examples of transcellular include cerebrospinal, pleural, peritoneal, synovial, and gastrointestinal (GI) fluids.

Body Fluid Calculations

• 1 liter of water is equivalent to 1 kilogram.
• Body weight changes are an excellent indicator of overall fluid volume loss or gain.
• Weighing patients helps reveal potential problems of fluid volume excess or deficiency.

Composition of Body Fluids

• Electrolytes separate into ions when dissolved in an aqueous solution and are able to carry an electrical current.
• Ions are charged particles.
• Cations are positively charged electrolytes, such as sodium, potassium, and calcium.
• Anions are negatively charged electrolytes, like chloride, bicarbonate, and sulphate.
• Electrolytes are crucial for body functions, should be regulated and kept within normal limits.
• Millimoles per liter (mmol/L) is used to measure the amount of specific electrolyte (solute) per fluid liter.

Movement of Water and Electrolytes

• Fluids and electrolytes constantly shift between compartments to facilitate body processes, including tissue oxygenation, acid-base balance, and urine formation.
• Osmosis, osmotic pressure, diffusion, active transport, filtration, and hydrostatic pressure facilitate this movement.

Fluid Homeostasis

• Renal regulation is primary for fluid and electrolyte balance.
• The kidneys adjust urine volume and concentration.
• Kidneys selectively reabsorb water and electrolytes.
• Renal tubules can be sites of action for ADH and aldosterone.
• Cardiac regulation involves Atrial natriuretic factor (ANF).
• Atrial natriuretic factor (ANF) is a hormone produced by cardiomyocytes in response to increased atrial pressure.
• ANF's main actions include vasodilation and increased urinary excretion of sodium and water, which ultimately decreases blood volume.
• Gastrointestinal regulation has oral intake which supplies most water.
• Only small amounts of water are eliminated via feces through the gastrointestinal (GI) tract.
• Diarrhea and vomiting may lead to significant fluid and electrolyte loss.

Fluid Homeostasis Regulation

• Body fluids are regulated via fluid intake, hormonal controls, and fluid output.
• Regulating hormones include antidiuretic hormone, angiotensin II, aldosterone, and natriuretic peptides.
• Fluid outputs can occur through the kidneys, skin, lungs, and the gastrointestinal tract.
• Obligatory water loss is 500 mL each day.
• Sensible water loss happens via urine and feces.
• Insensible water loss occurs via respiratory and skin.

Fluid Intake

• Fluid intake is regulated by the thirst mechanism.
• Osmoreceptors trigger thirst if there is an increase in plasma sodium.
• The renin-angiotensin-aldosterone system can trigger thirst.
• Hypovolemia and dehydration trigger thirst.
• The patient must be alert and independent for the thirst mechanism to work.
• The hormone regulation of fluid involves antidiuretic hormone (ADH), aldosterone, and natriuretic peptides.

Fluid and Electrolyte Imbalances

• They are common in patients with major illness or injury.
• Imbalances can be directly caused by illness/disease or therapeutic measures.
• Therapeutic measures that can cause imbalances include IV fluids, diuretics, parenteral nutrition etc.
• These imbalances can affect the very young and old as well as immobile or disoriented patients.
• Prolonged imbalances can lead to irreversible chronic health problems.
• Nurses assist in assessing, intervening, educating, monitoring and promoting quality hydration and homeostasis.

Hypovolemia

• ECF volume deficit (hypovolemia) is caused by factors like abnormal fluid loss, inadequate intake, or plasma-to-interstitial fluid shift. Examples include diarrhea and hemorrhage.
• Reduced fluid volume leads to inadequate cardiac output, which results in hypovolemic shock.
• Treatment includes balanced IV solutions. If the volume loss is caused by blood loss, transfusion will be needed.

Hypervolemia

• Fluid volume excess (hypervolemia) may be caused by excessive fluid intake, abnormal fluid retention, or interstitial-to-plasma fluid shift.
• An error in IV therapy or heart failure can lead to error.
• Excess fluid can result in edema, pulmonary edema, and ascites
• Treatment requires removing fluid whilst maintaining electrolyte composition and osmolality.

Sodium Imbalances

• Serum sodium level reflects the ratio of sodium to water.
• The serum sodium level may reflect a primary water imbalance, a primary sodium imbalance, or a combination of the two.
• Hypernatremia is elevated serum sodium, which occurs with water loss or sodium gain.
• Hyponatremia stems from loss of sodium-containing fluids or water excess.

Potassium Imbalances

• Hyperkalemia occurs with high serum potassium due to massive intake, impaired renal excretion, or shift from ICF to ECF and is most common in renal failure.
• Cardiac dysrhythmias is a potential complication.
• Hypokalemia is related to low serum potassium and occurs through abnormal potassium losses via the kidneys/ GI tract, magnesium deficiency, or metabolic alkalosis.
• Potential complication of hypokalemia includes Dysrhythmias.

Calcium Imbalances

• Calcium is obtained from ingested foods and is mostly combined with phosphorus and concentrated in the skeletal system.
• Calcium has an inverse relationship with phosphorus.
• Hypercalcemia is high serum calcium which occurs with hyperparathyroidism, malignancy, overdose of vitamin D, or prolonged immobilization.
• Cardiac dysrhythmias is a potential complication of hypercalcemia.
• Hypocalcemia (low serum calcium levels) is caused by decreased production of PTH, acute pancreatitis, multiple blood transfusions, and alkalosis.
• Fracture or respiratory arrest is one potential complication.

Phosphate Imbalances

• Maintenance requires adequate renal functioning.
• Phosphate is combined with calcium and shares an inverse relationship.
• Hyperphosphatemia is caused by acute or chronic renal failure, chemotherapy, and excessive ingestion of phosphate or vitamin D.
• Hypophosphatemia can be a result of malnourishment or malabsorption, alcohol withdrawal, or by being a side effect of parenteral nutrition with inadequate replacement.

Magnesium Imbalances

• 50 to 60% of magnesium is contained in bone.
• Both calcium and magnesium balance influences are related.
• Hypermagnesemia is too much magnesium. This is caused by a renal deficiency or failure.
• Hypomagnesemia is low magnesium. Contributing factors are prolonged fasting/starvation, chronic alcoholism, fluid loss, and diuretics.

Electrolyte Disorders: Clinical Manifestations

• Sodium Excess results in Hypernatremia, thirst, CNS deterioration, postural hypotension and weight loss.
• Sodium Deficit results in Hyponatremia, CNS deterioration, postural hypotension and rapid, thready pulse.
• Potassium Excess results in Hyperkalemia, irritability, anxiety, irregular pulse, and ECG with CNS changes.*
• Potassium Deficit results in Hypokalemia, fatigue, muscle weakness, weak irregular pulse, and ECG with CNS changes.
• Calcium Excess results in Hypercalcemia, thirst, CNS deterioration, increased interstitial fluid, and depressed reflexes.
• Calcium Deficit results in Hypocalcemia, tetany, Chvostek’s and Trousseau’s signs, hyperreflexia, muscle twitching, CNS and ECG changes.
• Magnesium Excess results in Hypermagnesemia, loss of DTRs, CNS and neuromuscular function depression.
• Magnesium Deficit results in Hypomagnesemia, hyperactive DTRs and CNS changes.

Nursing Implementation for Fluid Imbalance

• Strict monitoring of intake and output is key.
• Assess and monitor cardiovascular and respiratory changes.
• Check daily weights and skin.
• Undertake a neurological assessment, paying attention to level of consciousness, pupillary response, movement, reflexes and muscles.*

Interprofessional Care: Electrolyte Imbalance

• Primary goal is to treat the underlying cause of electrolyte imbalance.
• Treatments include replacing electrolytes, removing electrolytes, diet modifications, fluid restriction, monitoring serum levels, and accurate assessments.

Age-Related Considerations

• Structural changes to kidneys leads to decreased ability to conserve water.
• Hormonal changes lead to decrease in ADH and ANP.
• Loss of subcutaneous tissue leads to increased loss of moisture.
• Reduced thirst mechanism results in decreased fluid intake.
• Assessing and implementing treatment is key.

Regulation of Acid-Base Balance

• Acids are produced during normal body processes, which bases balance out.
• Normal blood pH is between 7.35 and 7.45, making blood slightly alkaline.
• A blood pH below 7.35 is acidosis.
• A blood pH above 7.45 results in alkalosis.
• Death occurs if pH drops below 6.8, or goes above 7.8.
• The body regulates acid-base balance through buffer, respiratory, and renal systems.

Buffer System

• It's the fastest-Acting and primary regulator of acid-base balances.
• Buffers chemically change strong acids to weak acids or bind acids to neutralize them.
• Examples are phosphate, protein, hemoglobin, carbonic acid and bicarbonate.
• Body buffers handle an acid load better than an excess in base.
• Buffers cannot maintain pH without adequate functioning of respiratory and renal system.

Respiratory System Regulation

• Lungs adapt to an acid-base imbalance in minutes to hours.
• They help maintain pH by excreting CO2 and water.
• Increased respirations = less CO2 in blood.
• Decreased respirations make more CO2 remains in blood.
• Respiratory problems cannot correct a pH alteration.

Kidney Regulation

• Kidneys can take few hours to days to regulate acid-base imbalances.
• They can generate or reabsorb bicarbonate as needed and eliminate excess acid as needed.
• Urine is acidic, roughly six on the pH scale. It can increase or decrease between 4 and 8.
• Renal failure loses it's ability to correct a pH alteration.

Types of Acid Base Imbalances

• The 2 different types of Acid-base Imbalances are respiratory and metabolic.
• Respiratory imbalances affects carbonic acid concentration.
• Metabolic imbalances affects the base bicarbonate.
• Respiratory acidosis stems from an increase in carbonic acid.
• Respiratory alkalosis happens when carbonic acid is decreased.
• Metabolic acidosis is caused by a decrease in bicarbonate.
• Metabolic alkalosis is due to an increase in bicarbonate.

More on Acid-Base Imbalances

• Respiratory acidosis occurs respirations are not effective when trying to excrete carbon dioxide.
• Increased PaCO2 and decreased pH is a sign of respiratory acidosis.
• COPD, sedative overdose, severe pneumonia, and respiratory muscle weakness are some examples of what causes respiratory acidosis.
• Respiratory alkalosis is associated with hyperventilation and increased CO2 excretion, which is decreased PaCO2 and increased pH.
• Examples include hyperventilation from hypoxia, anxiety, fear, pain, fever, pulmonary emboli; too much stimulation in respiratory centre of brain (brain injury, encephalitis etc.).
• Metabolic acidosis stems from a loss of base or inability to excrete acid which decreased pH, decreased HC03.
• Ex. Diabetic ketoacidosis (DKA), severe diarrhea, and renal failure cause this imbalance.
• Metabolic alkalosis has increased pH and increased HC03.
• This caused by a loss of acid from the body or through increase in levels of bicarbonate.
• Severe vomiting, diuretic therapy, and potassium deficit can also cause this.

Acid-Base Balance

• Arterial blood gas (ABG) analysis is the best way to evaluate and can indicate if an imbalance also exists there.
• Normal pH is 7.35–7.45.
• Partial Pressure determine acidos or alkalosis.
• HCO3 determines metabolic acidosis or alkalosis.
• Normal HCO3 determines that the patient is now well.
• Partial pressure of arterial oxygen (PaO2): check for presence of hypoxemia.
• Values also indicated if is compensating for acid-base imbalance or not.