Total Body Water and IV Fluids

Total Body Water (TBW)

• Males have approximately 60% TBW, while females have around 50% due to higher fat content
• Elderly individuals have less water and more fat, making them more prone to dehydration
• Extracellular fluid (ECF) constitutes 1/3 of TBW and includes plasma volume (1/4) and interstitial fluid (3/4)
• Intracellular fluid (ICF) makes up 2/3 of TBW

Isotonic Solutions

• Isotonic solutions have the same tonicity as blood, with 0.9% NaCl being a common example
• It primarily enters the extracellular fluid, with only 25% entering the intravascular space (vessels)
• The remaining 75% goes into the interstitial space

Hypotonic Solutions

• Solutions such as 0.45% NaCl are used to hydrate cells and treat cellular dehydration
• A larger portion (333ml) enters the extracellular space and 83ml goes into the intravascular space when administering 0.45% NaCl
• These solutions are useful for hydrating cells

Fluid Intake

• Typical sources of fluid intake include:
  • 1300 mL from ingested fluids
  • 1000 mL from water in foods
  • 300 mL from oxidation

Fluid Loss

• Sensible fluid loss refers to fluid loss that is visible, such as urine and feces
• Insensible fluid loss is not easily seen, including respirations and sweat
• Abnormal fluid loss can occur in various conditions

Causes of Abnormal Fluid Loss

• Fever or increased room temperature increases fluid loss through the lungs and skin
• Severe burns lead to increased fluid loss due to damaged skin
• Hemorrhage causes rapid decrease in vascular volume
• Rapid breathing increases fluid loss
• Emesis, fistulas, secretions, paracentesis, and thoracentesis contribute to fluid loss

Skin Injury

• Any skin injury, such as burns or wounds, can lead to rapid fluid loss, shifting fluid out of cells

Intravenous Fluids (Crystalloids)

• Isotonic fluids increase intravascular volume and blood pressure
• 0.9% Saline (normal saline) and Lactated Ringers are examples of isotonic fluids
• Lactated Ringers contain potassium, sodium, and other electrolytes
• Hypotonic fluids, like 0.45% Saline, increase intravascular volume and correct free water deficit- best IVF for dehydration if hemodynamically stable
• D5W is a hypotonic fluid where glucose is rapidly taken up by cells, which is best if replacing free water deficit or hypoglycemia
• Hypertonic fluids, like 3.0% Saline, is used only for severe symptomatic hyponatremia and cerebral edema

Osmotically Active Substances

• Plasma proteins, especially albumin, helps retain fluid in the vascular space
• In conditions like burns, malnutrition, or liver disease, inadequate albumin can cause fluid to leak into tissues and cause shock
• Glucose is osmotically active and draws water from the ICF into the ECF
• Hyperglycemia increases glucose particles compared to water in the vascular space causing particle-induced diuresis which leads to fluid electrolyte and particle imbalances

Kidneys Regulation of Glucose

• The kidneys filter excess glucose, leading to polyuria and fluid loss from the vascular space, potentially causing hypovolemia and shock

Hormones

• Electrolytes remain within normal range by hormones

Insulin

• Insulin promotes potassium movement from the blood into cells, thus decreasing serum potassium
• Potassium levels should always be checked before administering an insulin

Parathyroid Hormone (PTH)

• PTH increases calcium levels by extracting calcium from bone, reducing calcium excretion, and increasing phosphorus excretion in urine
• An increase phosphorus causes a decrease in calcium

Calcitonin

• Calcitonin is opposite of PTH, calcium says to bone to stop releasing calcium

Aldosterone

• Aldosterone increases sodium retention in the kidneys & decreases potassium
• Blocking aldosterone increases sodium loss and potassium retention

ADH

• ADH, an antidiuretic hormone, regulates water reabsorption in collecting tubules, increasing circulating volume and decreasing sodium concentration

Insulin Administration Considerations

• Serum potassium should be closely monitored when administering insulin, especially IV insulin, due to the risk of life-threatening arrhythmias
• Only regular insulin can be administered intravenously
• Phosphorus decreases when serum calcium levels increase, and vice versa

Sodium

• Total body sodium, not sodium concentration, is proportional to volume status
• Increased sodium leads to increased water retention and increased intravascular volume

Sodium Function & Levels

• Sodium serves as the primary electrolyte in the ECF and facilitates nerve impulse generation and transmission
• The kidneys excrete excess sodium
• Normal adult sodium levels range from 135 to 145 mEq/L

Hyponatremia

• Serum sodium levels less than 135 mEq/L
• Typically caused by excess free water or decreased total body sodium
• Evaluation includes measuring urine sodium, serum osmolality, and assessing clinical status
• Most common electrolyte abnormality

Isotonic Hyponatremia (Pseudohyponatremia)

• Lab artifact

Hypotonic Hyponatremia

• Serum osmo < 280mOsm/kg
• State of body water excess diluting all body fluids, which lead to clinical signs arising from water excess
• Hypovolemic w/urine Na+ < 10 mEq/L ( dehydration, diarrhea, vomiting)
• Hypovolemic w/ Urine Na+ > 20 mEq/L: Low volume and kidneys cant conserve Na (diuretics, most common causes)
• Hypervolemic, hypotonic hyponatremia: (excessive administration of D5W, psychogenic polydipsia, CHF, Liver disease, advanced renal failure, syndrome of inappropriate ADH)

Hypertonic Hyponatremia

• Serum osmolality > 290 mOsm/kg, low sodium high osmo
• Hyperglycemia

Signs and Symptoms of Hyponatremia

• Lethargy, confusion
• Excess free water in the ECF diffuses into the ICF which leads to cerebral edema
• Muscle weakness (Decreased excitability of cell membranes)
• Decreased deep tendon reflexes (DTRs) (Decreased excitability of cell membranes)
• Diarrhea (GI tract motility increases)
• Respiratory problems

Treatment of Hyponatremia

• Treatment depends on identifying whether the serum sodium is low due to low intake or excessive water in the vascular space
• Acute hyponatremia should be corrected rapidly (24-48 hours) but chronic hyponatremia should be corrected slowly
• Rapid correction may lead to Osmotic Demyelination Syndrome/brain injury

Solutions for Hyponatremia

• If excess free water, fluid restriction can be used
• if losing sodium, consider 0.9% or 3.0% Saline
• Neuro symptoms require aggressive treatment with 3% NaCal
• Goal is approxiamtely 5-8 millieoles per liter correction in 24 hours
• No more than 200 ml of urine output in 2 hours
• End stage renal disease receive fluid restriction and dialysis
• Cirrhosis patients receive synthetic albumin

Hypernatremia

• Serum sodium greater than 145 mEq/L
• Lack of free water
• Cause: Tachycardia, Dry mucus membranes, Altered mental status, Increased thirst, Muscle hyperactivity or hypoactivity, Profuse sweating without water replacement , Diarrhea and vomiting; NPO, Diabetes Insipidus & SIADH water dumps
• Treat with hypotonic fluids (0.45%) or free water or stop sodium products.

Electrolytes

• Think BRAIN first in patients with hypo- or hypernatremia
• Fatal complications can rise and rapid shifts in the serum sodium are dangerous

Potassium

• Skeletal and cardiac muscle must function correctly
• Chief electrolyte in ICF that plays vital role in transmission of electrical impulses
• Food Sources: peaches, strawberries, bananas, figs, dates, apricots, oranges, melons, raisins, prunes, broccoli, potatoes, and tomatoes
• Normal Potassium Level: 3.5 mEq/L to 5.3 mEq/L

Hypokalemia

• Serum potassium less than 3.5 mEq/L

Causes of Hypokalemia

• Diuretics- excreted through urine
• Steroids- retains sodium and water and excretes potassium
• GI suction- removes potassium from GI tract
• Vomiting- loss of potassium from GI tract
• Diarrhea- loss of potassium from GI tract
• NPO Status- not taking in enough potassium to replenish
• Cushing Syndrome- retains sodium and water and excretes potassium
• Alkalosis- Potassium moves into the cell dropping serum potassium

Signs and Symptoms of Hypokalemia

• Paralytic Ileus
• Muscle Cramps, muscle weakness
• EKG changes: PVCs, V tach, V fib, flattened T wave, ST depression, and a U-wave

Treatments of Hypokalemia

• High Potassium Diet
• IV or oral potassium chloride (increases serum K)- check for proper kidney function/good urine output when administering IV K
• Oral is preferred unless IV is required
• PO can cause GI upset- Give with food
• If Acidosis is present, correct first

Hyperkalemia

• Serum Potassium above 5.3 mEq/L
• Causes: Renal Insufficiency, IV KCl Overload, Burns or Crush injuries, Rhabdomyolysis, Tight Tourniquets, Hemolysis of CBC sample, Salt Substitutes, K+ Sparring diuretics, Blood Transfusions, ACE Inhibitor, Acidosis, Addison’s Disease (Adrenal Insufficiency)

Signs and Symptoms of Hyperkalemia

• Diarrhea/Hyper-contractility, heightened motility in gut muscles
• Muscle Twitching, tingling and burning
• Cardiac Arrhythmia

Potassium Imbalances

• Regarding potassium imbalances, the severity of the symptoms always depends on how fast the serum potassium is raising or falling
• Treatments:
• STAT EKG and Hold K+ retaining medications
• Remove Excess K+ with Kayexalate PO or Rectal- Veltassa binds the K and they urinate the K out
• STABILIZE the Cardiac membrane with Calcium Gluconate
• SHIFT THE K+ Intracellular with:
• IV insulin (10U) with D50
• Sodium Bicarbonate (Alkalosis)
• Albuterol
• Dialyze if refractory or severe

Calcium

• Actions: sedative on muscles
• Body: most abundant electrolyte
• Important relationships: inverse to phosphorus
• Needed for: nerve impulse transmission, blood clotting, muscle contraction, and relaxation
• Necessary to utilize: Vitamin D

Calcium Levels

• Normal calcium: 9.0 to 11.0 mg/dL
• Ionized calcium: 4.5-5.5mg/dL -doesn’t vary with albumin levels
• Hypocalcemia: more coming then hyper

Causes of Hypocalcemia

• Decreased Calcium, Renal Failure, Decreased/Lack of Vitamin D, Diarrhea, Pancreatitis, Hyperphosphatemia, Thyroidectomy, Low Albumin, Alkalosis,

Signs and Symptoms of Hypocalcemia

• Muscle Cramps, Tetany, Convulsions, Arrhythmias, Positive Chvostek’s
• Hyperactive DTRS, Cardiac Changes

Hypercalcemia

• Serum CA > 11 mg/dL
• Causes: hyperparathyroidism, immobilization, increased calcium intake, increased vitamin D intake, thiazide diuretics and malignancy

Signs and Symptoms of Hypercalcemia

• stones, bones, groans, moans and psychic overtones Treatment for Hypercalcemia
• IV, diuretics, phosphate, bisphosphonates

Phosphorus

• Promotes the function of muscle, red blood cells (RBCs), and the nervous system
• Regulated by the parathyroid hormone
• Has an inverse relationship with calcium
• Normal phosphorus is 2.5 to 4.5 mg/dL

Hypophosphatemia

Hyperphosphatemia

Magnesium Levels

• Normal magnesium: 1.5 to 2.5 mEq/L

Signs and Symptoms of Hypomagnesemia

• Increased neuromuscular irritability - seizure
• Hyperactive DTRs, Cardiac changes - arrhythmias
• Decreased magnesium levels increase nerve impulses
• Think: NOT SEDATED
• The majority of magnesium comes from our dietary intake

Management of Electrolyte Imbalances

• Treatment:
• Increased dietary magnesium
• Magnesium sulfate IV

Hypermagnesemia

• Serum Magnesium > 2.5 mEq/L

Signs and Symptoms of Hypermagnesemia

• Drowsiness to comatose state
• Decreased DTRs
• Generalized weakness
• Decreased respirations to respiratory arrest
• Cardiac changes: decreased pulse, prolonged PR, wide QRS, cardiac arrest

Causes of Hypermagnesemia

• Renal failure: kidneys lose the ability to regulate magnesium levels effectively
• Increased oral or IV intake: excessive intake through supplements or medications
• Antacids: antacids containing magnesium

Treatments

• Loop diuretics: to remove electrolytes and fluid
• 0.45% saline solution and/or IV calcium Gluconate: to help balance magnesium levels
• Hemodialysis: hemodialysis may be needed to help decrease the serum magnesium