Fluids and Electrolytes

FLUID BALANCE, ELECTROLYTE IMBALANCES AND REPLACEMENT

Introduction

  • Presented by Dr. Kaitlin Voigts

  • Special thanks to Dr. Jessica Harman Thompson

Fluid Overview

What Does Body Fluid Do?

  • Transportation
      - Transports nutrients and waste to and from cells.

  • Solvent Functions
      - Acts as a solvent for electrolytes and non-electrolytes.

  • Physiological Roles
      - Maintains body temperature.
      - Aids in digestion and elimination.
      - Contributes to acid-base balance.
      - Provides lubrication for joints and body tissues.

Definition of Body Fluid

  • Body Fluid:
      - Fluid is defined as water that contains dissolved or suspended substances such as glucose, electrolytes, and proteins.

  • Composition:
      - Approximately 50-60% of adult body weight is water.

Types of Fluid Compartments

  • Intracellular Fluid (ICF):
      - Comprises 70% of body fluid, found inside the cells.

  • Extracellular Fluid (ECF):
      - Makes up 30% of body fluid, located outside of cells, and further divided into:
        - Interstitial Fluid: Fluid between the cells.
        - Intravascular Fluid: Plasma, the liquid portion of the blood.

Movement of Fluid & Electrolytes

  • Four Processes:
      - Diffusion
      - Facilitated Diffusion
      - Active Transport
      - Osmosis

Osmosis

  • Defined as the movement of water down a concentration gradient.

  • Water moves from a region of low solute concentration to one of high solute concentration across a semipermeable membrane.

  • Stops when concentration differences equalize or hydrostatic pressure builds and opposes further movement.

Diffusion

  • The movement of molecules from an area of high concentration to an area of low concentration.

  • Movement halts when concentrations are equal in both areas.

The Shifting of Water and Body Fluids

Fluid and Electrolyte Balance

  • Water follows electrolytes: Sodium and chloride predominantly reside outside the cells, while potassium, magnesium, phosphate, and sulfur are located within.

  • Osmosis: Movement of water towards more concentrated solute areas, driven by osmotic pressure, which is the pressure needed to prevent water movement across a cell membrane.

Colloids

  • Definition: Substances that increase colloid osmotic pressure (oncotic pressure).

  • Colloids help move fluid from interstitial compartments to plasma (blood) compartments.

  • Primary Colloids: Albumin, globulin, and fibrinogen.

  • Clinical Relevance:
      - Colloid oncotic pressure can decrease with age and malnutrition.
      - Can be replaced with colloid replacements in clinical settings.

Pressures

Hydrostatic Pressure

  • Defined as the force of fluid in a compartment pushing against a cell membrane or vessel wall.

  • Generated by blood pressure, and at the capillary level, it is the major force that pushes water out of the vascular system into the interstitial space.

Oncotic Pressure

  • Also called colloid osmotic pressure, caused by plasma colloids (large molecules) in solution.

  • Major colloids in the vascular system include albumin.

  • Plasma has a high concentration of colloids while interstitial space has a low concentration.

  • Mechanism: Plasma proteins attract water, pulling fluid from tissue space into vascular space.

Key Differences Between Hydrostatic and Oncotic Pressure

  • Hydrostatic pressure pushes fluid out of the capillary while oncotic pressure pulls fluid into the capillary.

  • Pressure values: 30 mmHg for hydrostatic pressure and 20 mmHg for oncotic pressure.

  • Hydrostatic pressure occurs at the arterial end of blood capillaries, while oncotic pressure occurs at the venular end.

Electrolytes

Importance of Electrolyte Balance

  • Electrolytes influence fluid balance, acid-base balance, nerve impulses, muscle contraction, heart rhythm, and various other cell functions.

  • Changes in one electrolyte can affect the balance of others due to their collaborative functions.

Definition of Electrolytes

  • Substances that are electrically charged when dissolved in solution.

  • Example: Potassium ion (K+).

Factors Determining Electrolyte Concentrations

  • Potassium, Calcium, Magnesium, Chloride, Sodium, Manganese concentrations depend on:
      - Electrolyte intake.
      - Absorption.
      - Distribution.
      - Excretion.

Locations of Electrolytes

  • Intracellular Electrolytes: High concentrations of potassium and magnesium.

  • Extracellular Electrolytes: High concentrations of sodium and chloride.

  • If an electrolyte imbalance occurs, replacement should be similar to what was lost.

Normal Lab Values of Key Electrolytes

  • Sodium: 136 – 145 mEq/L

  • Potassium: 3.5 - 5.0 mEq/L

  • Magnesium: 1.3 - 2.1 mEq/L

  • Calcium: 9.0 - 10.5 mg/dL

  • Phosphate: 3 - 4.5 mg/dL

  • Note: Each value may vary based on laboratory equipment.

Sodium Imbalances

Sodium Imbalance Definitions

  • Hyponatremia: Sodium level below 136 mEq/L

  • Hypernatremia: Sodium level above 145 mEq/L

Importance of Sodium

  • Sodium (Na+):
      - Main cation in extracellular fluid.
      - Governs osmolality and influences water distribution, acid-base balance, and is vital for activating muscle and nerve cells.

Causes of Hyponatremia

  • Less than 136 mEq/L
      - Gastrointestinal losses: Diarrhea, vomiting.
      - Renal losses: Diuretics, adrenal insufficiency.
      - Skin losses: Burns, wound damage.
      - Factors including fasting diets and polydipsia (excessive water intake).
      - Excess hypotonic fluid.

Signs and Symptoms of Hyponatremia

  • Confusion or altered level of consciousness (LOC).

  • Anorexia and muscle weakness.

  • Potential progression to seizures and coma.

  • Distinction:
      - Dilutional Hyponatremia (hypervolemic): Increased blood pressure, weight gain, and bounding rapid pulse with increased urine specific gravity.
      - Depletional Hyponatremia (hypovolemic): High heart rate and low blood pressure, dry skin, weight loss, and higher urine specific gravity.

Treatment of Hyponatremia

  • Sodium replacement (SLOWLY) via oral or intravenous methods.

  • Possibly include diuretics.

  • Utilize IV Normal Saline (0.9%).

  • Fluid restriction and treatment of underlying problems.

Sodium Bicarbonate (Key Information)

  • Mechanism of Action: Dissociates to provide bicarbonate ions, neutralizing ion concentration and raising blood and urinary pH. Also increases sodium concentration in plasma.

  • Indications: Metabolic acidosis.

  • Administration: Oral (PO) or with caution as IV (not advised for hyponatremia).

  • Adverse Effects: Include edema, cerebral hemorrhage, hypernatremia, electrolyte abnormalities, flatulence when oral, and potential for tetany or pulmonary edema. Monitor cardiac function and electrolytes.

Hypernatremia Causes

  • Sodium level greater than 145 mEq/L.

  • Caused by:
      - Excess sodium intake from IV fluids or tube feeds.
      - Insufficient water intake or excessive water loss (e.g., in cases of cognitive impairment, diarrhea, high fever, heat stroke).
      - Profound diuresis.

Signs and Symptoms of Hypernatremia

  • Altered LOC or confusion, potentially seizures or coma.

  • Extreme thirst due to hyperosmolality.

  • Dry, sticky mucous membranes, muscle cramps.

Treatment of Hypernatremia

  • If due to water loss, add water.

  • If excess sodium, gradually remove sodium, achieving normal levels over 48 hours to prevent cerebral edema. Rapid correction is potentially lethal.

  • Example: Infuse Normal Saline Solution (NSS) at increasing rates as ordered.

Potassium Imbalances

Potassium Imbalance Definitions

  • Hypokalemia: Potassium levels below 3.5 mEq/L.

  • Hyperkalemia: Potassium levels above 5.0 mEq/L.

Importance of Potassium

  • Potassium (K+) is the main intracellular cation, critical for:
      - Regulation of cell excitability and electrical status.
      - Control of intracellular osmolality.
      - Main dietary source and renal clearance.

Causes of Hypokalemia

  • Less than 3.5 mEq/L
      - Renal or gastrointestinal losses.
      - Diuresis.
      - Acid-base disorders causing potassium to move into cells.

Signs and Symptoms of Hypokalemia

  • Cardiac rhythm disturbances which may be lethal.

  • Muscle weakness, leg cramps, and decreased bowel motility (leading to constipation and nausea).

Treatment of Hypokalemia

  • Pharmacological Treatment:
      - Potassium chloride (KCl) used to treat or prevent depletions.
      - Oral considerations: Dilute with water/juice to minimize GI distress.
      - IV considerations: Must be diluted, never IV push. Patient must have documented urine output; watch for potential complications like phlebitis or GI ulcers.

Key Points of Hypokalemia Treatment

  • IV potassium must be diluted; administration should be slow (rate not exceeding 10-20 mEq/hr) and monitored for adverse effects.

  • Caution in renal failure patients due to potential for existing high potassium levels.

Hyperkalemia Causes

  • Greater than 5.0 mEq/L
      - Decreased potassium output (e.g., renal failure).
      - Conditions involving massive cell injury (burns, crush injuries, sepsis).
      - Certain medications such as potassium-sparing diuretics, ACE inhibitors, ARBs, and NSAIDs.

Signs and Symptoms of Hyperkalemia

  • Cardiac rhythm disturbances.

  • Muscle weakness and cramps.

  • Abdominal cramping, diarrhea, and vomiting.

Treatment of Hyperkalemia

  • ECG Evaluations: Identify abnormalities such as peaked T waves, prolonged PR segments, loss of P waves, and progressive widening of QRS complexes, potentially leading to asystole.

  • Management Guidelines:
      - Sequential dietary intake adjustments.
      - Intensification of serum potassium controls.
      - Corrections for acidosis if present.
      - Use potassium binders when indicated.
      - Possible need for dialysis in severe cases.

Pharmacotherapy with Kayexalate (Sodium Polystyrene Sulfonate)

  • Available as oral or rectal formulations, used to treat hyperkalemia.

  • Mechanism of Action (MOA): Binds potassium in the digestive tract, replacing potassium ions for sodium ions, with a potential drop of potassium by 0.5-1.0 mEq/L in 4-6 hours.

  • Adverse Reactions: Include constipation, diarrhea, and significant risks such as intestinal obstruction.

D50/Insulin for Hyperkalemia

  • Intravenous combination temporarily shifts potassium intracellularly.

  • Typically administered as 10 units of regular insulin with 1 ampule of D50 (50% dextrose).

Magnesium Imbalances

Magnesium Overview

  • Magnesium stabilizes cardiac muscle cells, blocks potassium movement from cardiac cells, and stabilizes smooth muscle function.

Hyper and Hypomagnesemia Values

  • Hypomagnesemia: Less than 1.3 mEq/L

  • Hypermagnesemia: Greater than 2.1 mEq/L

Causes of Hypomagnesemia

  • Diuresis, gastrointestinal or renal losses, limited intake, alcohol abuse, and pancreatitis.

Signs and Symptoms of Hypomagnesemia

  • Hyperactive reflexes, confusion, muscle cramps, and tremors or seizures.

Treatment of Hypomagnesemia

  • Replacement: Oral (e.g., Mylanta) or IV magnesium sulfate, replace over several days unless emergencies dictate IV push.

Treatment with Magnesium Sulfate

  • Administration Forms: IV for severe hypomagnesemia, PO for gastrointestinal issues.

  • Indications: Prevent or treat seizures in pre-eclampsia, manage cardiac rhythm disturbances.

  • Adverse Effects: Potential lethargy, nausea, abnormal heart rhythms, can burn when administered IV.

Hypermagnesemia Causes and Treatment

  • Causes include renal failure or excessive intake of magnesium.

  • Symptoms involve lethargy and decreased cardiac reflexes; treatment involves stopping magnesium replacement and may require dialysis.

Calcium Imbalances

Calcium Overview

  • Calcium is primarily regulated by the thyroid and parathyroid glands and exists mainly in bones.

  • Contributes to the stability and strength of bones, with small amounts in cells and ionized in extracellular space.

  • Functions: Impacts enzyme reactions, muscle contractions, hormone releases, and blood clotting.

Hypo and Hypercalcemia Values

  • Hypocalcemia: Less than 9.0 mg/dL

  • Hypercalcemia: Greater than 10.5 mg/dL.

Causes of Hypocalcemia

  • Inability to mobilize calcium from bones, hypoparathyroidism, increased binding, renal losses, and inadequate intake.

Signs and Symptoms of Hypocalcemia

  • Increased neuromuscular excitability, paresthesias, muscle cramps, tetany, and signs like:
      - Positive Chvostek's Sign: Facial muscle twitching in response to tapping.
      - Positive Trousseau’s Sign: Carpal spasm on blood pressure cuff inflation.

Treatment of Hypocalcemia

  • Administer IV calcium (e.g., Calcium Chloride) through central lines, or Calcium Gluconate preferably.

  • Oral calcium options available (e.g., calcium carbonate). Potential need for Vitamin D supplementation.

Hypercalcemia Causes

  • Often results from hyperparathyroidism or cancers. Signs include lethargy, confusion, and kidney stones.

Treatment of Hypercalcemia

  • Adequate hydration and diuretics to increase urine output and facilitate calcium elimination; possible dialysis in renal failure cases.

Phosphorus Imbalances

Phosphorus Overview

  • Found predominantly in bones (85%) and cells (14%), lesser amounts circulate in plasma.

  • Essential for ATP formation and enzymes involved in metabolism.

Phosphorus Imbalances Values

  • Hypophosphatemia: Less than 3.0 mg/dL.

  • Hyperphosphatemia: Greater than 4.5 mg/dL.

Causes of Hypophosphatemia

  • Decreased absorption, antacid overdose, severe diarrhea, and malnutrition.

Clinical Manifestations of Hypophosphatemia

  • Vary from mild malaise to severe symptoms like tremors, seizures, and muscle weakness.

Causes of Hyperphosphatemia

  • Kidney failure, excessive phosphorus intake via laxatives/enemas, and often asymptomatic except for signs of hypocalcemia.

Treatment Comparison: Hypophosphatemia vs Hyperphosphatemia

  • Hypophosphatemia Treatment: IV or oral replacements, monitoring renal function.

  • Hyperphosphatemia Treatment: Address underlying causes; calcium-based phosphate binders and possible hemodialysis for renal failure patients.