Fluids and Electrolytes: AGACNP Review

• Vital information regarding fluid and electrolytes for AGACNP students.

Water

• Total body water (TBW) percentages:
  • Males: Approximately 60%
  • Females: Approximately 50% (due to higher fat content)
  • Elderly individuals have less water due to decreased muscle mass and increased fat, predisposing them to dehydration.
• Extracellular fluid (ECF) comprises 1/3 of TBW.
  • Plasma volume accounts for 1/4 of ECF.
  • Interstitial fluid makes up 3/4 of ECF.
• Intracellular fluid (ICF) constitutes 2/3 of TBW and is the majority of body water.
• Isotonic solutions share the same tonicity as blood, with 0.9% NaCl being the most common
  • Administering isotonic fluids results in distribution into the extracellular fluid, with only 25% (250ml) entering the intravascular space (vessels).
  • The remaining 75% (750ml) distributes into the interstitial space, leading to fluid overload without necessarily expanding plasma volume.
  • Isotonic solutions may be needed if the patient has low BP
• Hypotonic fluid (ICF) is for cellular dehydration
  • 0.45% NaCl: 333ml goes into extracellular majority goes ECF not into veins, only 83ml intravascular space
• Fluid intake consists of:
  • Ingested fluids: 1300 mL
  • Water in foods: 1000 mL
  • Oxidation: 300 mL
• Fluid loss is categorized into:
  • Sensible fluid loss: Visible loss through urine and feces.
  • Insensible fluid loss: Not directly visible, such as through respirations and sweat.
  • Abnormal fluid loss

Fluid Volume Deficit

• Fever or increased room temperature escalates fluid loss via the lungs and skin.
• Severe burns increase fluid loss due to compromised skin integrity.
• Hemorrhage leads to rapid decrease in vascular volume.
• Rapid breathing increases fluid loss.
• Emesis, fistulas, secretions, paracentesis, and thoracentesis also contribute to fluid loss.
• Skin interference from burns or wounds results in rapid fluid loss.

IV Fluids (Crystalloids)

• Isotonic fluids increase intravascular volume, Goal is ↑BP
  • Examples include 0.9% Saline (normal saline).
  • Lactated Ringers with K, Na, and other electrolytes.
• Hypotonic fluids increases intravascular volume & correct free water deficit, by going into the cells
  • 0.45% Saline and D5W replaces free water deficit or hypoglycemia
• Hypertonic Fluid: Used only for severe symptomatic hyponatremia & cerebral edema
  • 3.0% Saline

Osmotically Active Substances

• Plasma protein (albumin) holds fluid in the vascular space, but a patient is burned or has liver disease, problems can occur and adequate albumin cant hold fluid in the vessels
• Glucose is osmotically active, drawing water from ICF to ECF.

Hormones

• Hormones maintain electrolyte balance.
• Insulin moves potassium from blood to inside cells, reducing K levels.
  • Always check potassium levels before insulin administration.
  • Hyperkalemic patients receiving insulin and dextrose experience a pull of dextrose and K into cells.
• Parathyroid hormone (PTH) increases calcium levels, decreases calcium excretion, and increases phosphorus excretion.
• Calcitonin decreases calcium levels, opposite PTH
• Aldosterone promotes sodium retention (think: retain sodium)
  • Aldosterone increases sodium retention thus increasing BP, kidneys hold onto sodium with the side effect of retaining water..
• ADH relates to water
  • Increases free water reabsorption results in increasing circulating volume and decreasing sodium concentration.

Electrolytes

• Sodium as chief electrolyte in extracellular fluid has total body sodium proportional to volume status.
  • Assists with nerve impulse generation and transmission.
  • Excess sodium is excreted by kidneys.
  • Normal adult sodium level: 135-145 mEq/L.
• Hyponatremia: serum sodium less than 135 mEq/L. Consider Urine sodium, serum osmolality, and clinical status.
  • Most commonly caused by excess free water or decreased total body sodium.
  • Can be due to low sodium or excess of water.

Causes of Hyponatremia

• Isotonic Hyponatremia (pseudohyponatremia)
  • Lab artifact
• Hypotonic Hyponatremia (serum osmo < 280mOsm/kg):
  • Hyponatremia and hypotonicity and low osmolality. A) Hypovolemic w/urine Na+ < 10 mEq/L: dehydration, diarrhea, & vomiting B) Hypovolemic w/ Urine Na+ > 20 mEq/L: kidneys cant conserve Na -Diuretics* is the most common cause - decreased aldosterone C) Hypervolemic, hypotonic hyponatremia: - excessive administration of D5W - psychogenic polydipsia - CHF, liver disease, & advanced renal failure - syndrome of inappropriate ADH and free water causing sodium concentration
• Hypertonic Hyponatremia (serum osmolality > 290 mOsm/kg. Low sodium high osmo, usually hyperglycemic
  • Hyperglycemia

Signs and Symptoms of Hyponatremia

• Brain doesnt function well with low levels of sodium, causing lethargy and confusion
  • Excess free water in the ECF diffuses into the ICF leading to cerebral edema
• Muscle weakness happens since decreased excitability of cell membranes
• Decreased deep tendon reflexes (DTRs)
• Respiratory problems: Late symptoms= respiratory muscles become weak and can't function properly

Treatment for Hyponatremia

• Treat the cause whether there is low intake or extreme loss.
  • if the serum sodium is low due to low intake or extreme loss of sodium alone OR is the hyponatremia due to excessive WATER in the vascular space
• Acute hyponatremia should be corrected acutely (24-48 hours). Chronic hyponatremia should be corrected slowly.
• Overly rapid correction can lead to osmotic demyelination syndrome
  • Fluid restriction if cause is excess free water
  • If cause is Na Wasting then consider 0.9% or 3.0% Saline.
    • Any neuro symptoms, resp arrest require aggressive treatment with 3% NaCal -- give 25MeQ/hr for 4 hours less than NA 120 severe
• Avoid rapid correction of NA, by increasing 5-8 millieoles per liter correction in 24 hours
  • no more than 200 ml of urine output in 2 hours
• End stage renal disease will get fluid restriction and dialysis
• Cirrhosis will get albumin because liver makes albumin

Hypernatremia

• Serum sodium greater than 145 mEq/L
• The issue is usually a lack of free water, can be due to excess Na intake. Signs and symptoms:
  • Tachycardia, Dry mucus membranes, Altered mental status, Increased thirst,
  • Muscle hyperactivity or hypoactivity; Can lead to seizures, coma, death
• Causes:
  • Profuse sweating without water replacement (heat stroke, lost desert)
  • Diarrhea and vomiting; NPO
  • Diabetes Insipidus & SIADH water dumps
• Treatment:
  • If lack of free water is the reason, treat with hypotonic fluids (0.45%) or free water. If the cause is excess sodium then stop giving Na products.
• Sodium imbalances result in potentially deadly consequences.

Potassium

• Makes skeletal and cardiac muscle work correctly
• Chief electrolyte in ICF. Intracellular fluid
• Plays a vital role in the transmission of electrical impulses

Hypokalemia

• Serum Potassium less than 3.5 mEq/L
• CAUSES:
  • Diuretics, Steroids, GI Suction, Vomiting, Diarrhea, kidneys lose potassium with age ( elderly ), cushing syndrome, alkalosis
• S&S: Paralytic ileus, muscle cramps, muscle weakness

Treatments of Hypokalemia

• High potassium diet
• IV or oral potassium chloride increases serum K
  • when administering Potassium make sure patient has proper kidney function and good urine output
  • oral is preferred, can cause GI upset give with food if possible
  • if IV is required max 10mEq/hour in peripheral and 20 mEq/hour in the central line, IV can cause severe burning, give with food if possible

Hyperkalemia

• Serum Potassium above 5.3 mEq/L
• High serum of postassium causes Diarrhea, muscle twitching, tinging and burning, and cardiac arrhythmia

Treatment of Hyperkalemia

• STAT EKG and Hold K+
• Remove Excess K+ with Kayexalate PO or Rectal
• STABILIZE the Cardiac membrane with Calcium Gluconate
• SHIFT THE K+ Intracellular w/ IV insulin (10U) with D50, Sodium Bicarbonate (Alkalosis)will correct acidosis, Albuterol
• Dialyze if refractory or severe

Calcium

• Most abundant electrolyte in the body, acts like a sedative on muscles, high calcium on muscles is like a sedative that sedates
• Has an inverse relationship to phosphorus : (low calcium high phos, high calcium low phos)
• Necessary for nerve impulse transmission, blood clotting, muscle contraction, & relaxation.
• Promotes strong bones and teeth, so children, pregnant, & lactating women need extra calcium

Hypocalcemia

• Serum Calcium < 9.0
• Causes: decreased calcium intake, renal failure, diarrhea, pancreatitis, hyperphosphatemia, & thyroidectomy. hypoparathyroidism
• Leads to falsely lowered calcium because Albumin binds approximately 50% of blood Ca. The ionized Ca is still normal
• the S&S: Muscle Cramps Tetany, Convulsions, Arrhythmias hyperactive DTRS & Carpal pedal spasm
• Tx: FIRST CHECK ALBUMIN and correct

Hypercalcemia

• Serum Ca > 11 mg/dL
• Excessive PTH that causes the serum calcium to increase
• Stones, Bones, Groans, Moans, and Psychic Overtones is what you get
• TX: Normal Saline IV, loop diuretics, iv prostate and Biphosphonates for Osteoporosis

Phosphorus

• Promotes the function of muscle, red blood cells (RBCs), and the nervous system
• Has an inverse relationship with calcium
• regulated by the parathyroid hormone

Hypophosphatemia

• Less than 2.5 mg/dL
• Caused by malnourished states, hyperparathyroidism and disorders that cause hypercalcemia
• S & S: Weakness, numbness, tingling Pathological fractures Nausea, vomiting anorexia
• Tx: Phosphate-binding gels, restrict phosphorus and dialysis

Hyperphosphatemia

• Less common and predominantly associated with acute renal failure
• hyperthyroidism
• Tx: phosphate-binding gels and restriction of dietary phosphorus

Magnesium

• Present in heart, bone, nerves, and muscle tissues, also acts like a sedative on muscles
• Levels are controlled by the kidneys
• Normal magnesium: 1.5 to 2.5 mEq/L

Hypomagnesemia

• Serum Magnesium < 1.5 mEq/L
• caused by diarrhea, diuretics, diet lack and chronic alcoholism
• S&S: Hyperactive DTRS, think NOT SEDATED.

Hypermagnesemia

• Serum Magnesium > 2.5 mEq/L
• causes dizziness and decreased pulse
• Caused by Renal failure, Increased oral or IV intake Antacids (Many antacids contain a large amount of magnesium)
• S&S
• Drowsiness to comatose state, Decreased DTRS, Generalized weakness Decreased respirations to respiratory arrest