Total Body Water and IV Fluids

Total Body Water (TBW)

• Males have approximately 60% TBW, while females have about 50% due to more fat
• Elderly individuals have less water due to decreased muscle mass and increased fat, making them more prone to dehydration
• Extracellular fluid (ECF) constitutes 1/3 of TBW, which is further divided into plasma volume (1/4) and interstitial fluid (3/4)
• Intracellular fluid (ICF) makes up 2/3 of TBW and accounts for the majority of total body water

Isotonic Fluids

• Isotonic fluids have the same tonicity as blood
• 0.9% NaCl is the most common isotonic solution
• When administered, isotonic fluids primarily go into the extracellular fluid, with only 25% entering the intravascular space (vessels)
• 75% of isotonic fluid goes into the interstitial space
• Isotonic fluids need to be administered to dehydrated patients to fill up vascular space, even though hypotonic will not help as it goes into extracellular space

Hypotonic Fluids

• Hypotonic fluids are given to get inside cells
• 0.45% NaCl is a hypotonic solution where 333ml goes into extracellular majority and 83ml enters the intravascular space
• Hypotonic fluids are used for cellular dehydration

Fluid Intake

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

Fluid Loss

• Sensible fluid loss is visible and includes urine and feces
• Insensible fluid loss is not visible, such as respirations and sweat
• Abnormal fluid loss can occur due to fever, burns, hemorrhage, rapid breathing, emesis, and fistulas

IV Fluids (Crystalloids)

• Isotonic fluids increase intravascular volume and blood pressure
  • Examples include 0.9% Saline (normal saline) and Lactated Ringers (containing K, Na, and other electrolytes)
• Hypotonic fluids increase intravascular volume and correct free water deficit
  • 0.45% Saline is the best IVF for dehydrated patients but is not used on hemodynamically unstable patients
  • D5W is best when replacing free water deficit or hypoglycemia as the glucose is rapidly taken up by cells, leaving only free water
• Hypertonic fluids such as 3.0% Saline are typically used for severe symptomatic hyponatremia and cerebral edema

Osmotically Active Substances

• Plasma proteins hold fluid in the vascular space, with albumin being the most abundant
• When the liver cannot make adequate amounts of albumin, fluid may leak out of the vessels into the tissues to cause shock
• Glucose is osmotically active and draws water out of the ICF into the ECF, leading to polyuria

Hormones and Electrolyte Balance

• Insulin moves potassium from the blood to the inside of the cell to decrease serum K
• Parathyroid hormone (PTH) increases calcium levels by promoting calcium release from bone, decreasing calcium excretion, and increasing phosphate excretion in urine
• Calcitonin decreases calcium levels by promoting calcium deposition in bone
• Aldosterone increases sodium retention in the kidneys, leading to decreased potassium levels and increased water retention
• ADH increases free water reabsorption in collecting tubules to lead to increased circulating volume and decreased sodium concentration
• It is important to watch serum potassium levels when administering insulin-especially IV insulin
• Regular insulin is the only kind of insulin that can be given IV
• Serum calcium and phosphorus levels have an inverse relationship

Electrolytes and Sodium

• Sodium levels are proportional to volume status
• Sodium is the chief electrolyte in ECF
• Sodium assists with generation and transmission of nerve impulses
• Excess sodium is excreted by kidneys
• Normal adult sodium level is 135 to 145 mEq/L

Causes of Hyponatremia

• Isotonic hyponatremia is a lab artifact
• Hypotonic hyponatremia causes State of body water excess diluting all body fluids
• Hypertonic hyponatremia is typically caused by hyperglycemia

Hypovolemic Hyponatremia

• Hypovolemic with urine Na+ < 10 mEq/L is often caused by dehydration, diarrhea, and vomiting
• Hypovolemic with urine Na+ > 20 mEq/L is often caused by diuretics and decreased aldosterone

Hypervolemic Hyponatremia

• Is caused by excessive administration of D5W, psychogenic polydipsia, CHF, liver disease, and advanced renal failure

Signs and Symptoms of Hyponatremia

• Causes lethargy, confusion, muscle weakness, decreased deep tendon reflexes, diarrhea, and respiratory problems
• Hyponatremia can cause excess free water in the ECF to diffuse into the ICF, leading to cerebral edema and possibly seizures, coma, and death

Treatment for Hyponatremia

• Mild cases are treated with IV saline solution
• Severe cases are treated with hypertonic saline

Hypernatremia

• Characterized by serum sodium greater than 145 mEq/L
• Signs and symptoms include tachycardia, dry mucus membranes, altered mental status, and increased thirst
• It can be caused by profuse sweating without water replacement, diarrhea and vomiting, NPO, diabetes insipidus, and SIADH

Treatment for Hypernatremia

• Is to treat with hypotonic fluids (0.45%) or free water

Potassium

• Is a chief electrolyte in ICF and makes skeletal and cardiac muscle work correctly
• Plays a vital role in the transmission of electrical impulses
• Food sources include peaches, strawberries, bananas, figs, dates, apricots, oranges, melons, raisins, prunes, broccoli, potatoes, and tomatoes
• Potassium is excreted by the kidneys

Hypokalemia: Serum Potassium Less than 3.5 mEq/L

• Caused by diuretics, steroids, GI suction, vomiting, diarrhea, NPO status/poor oral intake, age, cushing syndrome, and alkalosis
• Causes Paralytic ileus, muscle cramps and muscle weakness and EKG abnormalities

Treatments for Hypokalemia

• Includes a high potassium diet (to replace K) and IV or oral potassium chloride
• Oral is preferred and if IV is required, use max 10mEq/hour in peripheral and 20 mEq/hour in central line
• If acidosis is present, correct K first and expect increase 0.5 mil equivalent for every 100 meq of iv potassium infused

Hyperkalemia: Serum Potassium Above 5.3 mEq/L

• Causes diarrhea and muscle twitching
• EKG changes include: peaked T-wave→ flat or no P-wave →wide QRS complex→ ventricular tachycardia or ventricular fibrillation→ Asystole

Causes of Hyperkalemia

• Include renal Insufficiency, IV KCl Overload, burns or crush injuries and rhabdomyolysis
• May be caused by tight tourniquets, hemolysis of CBC sample, salt substitutes and K+ sparing diuretics
• May result from ACE Inhibitor, Acidosis and Addison’s Disease (Adrenal Insufficiency)

Treatments for Hyperkalemia

• Consists includes STAT EKG, K+ retaining medications and removing Excess K+
• Stabilize the Cardiac membrane with Calcium Gluconate or shift the K+ intracellular
• If refractory or severe, dialysis may be performed

Calcium

• Acts like a sedative on muscles with an inverse relationship to phosphorus
• Necessary for nerve impulse transmission, blood clotting, muscle contraction, and relaxation
• Promotes strong bones and teeth and must have vitamin D present to utilize calcium

Hypocalcemia: Serum Calcium Less than 9.0

• Caused by decreased calcium intake, renal failure, and decreased Vit D intake
• Diarrhea, pancreatitis, hyperphosphatemia, thyroidectomy, and low albumin can cause it
• May result from alkalosis and a low K and a low CA

Signs and Symptoms of Hypocalcemia

• Includes muscle cramps, tetany, convulsions and arrhythmias
• May be caused by positive Chvostek’s and Trousseau’s sign
• Cardiac Changes with hyperactive DTRs can occur

Treatments for Hypocalcemia

• Involves checking and correcting the Albumin level with IV calcium and vitamin D therapy
• Increasing dietary calcium can help treatment

Causes of Hypercalcemia: Serum Ca > 11 mg/ dL

• Results from Immobilization and increased calcium and vitamin D intake
• Is caused by Thiazide diuretics and Malignancy

Signs and Symptoms of Hypercalcemia

• Causes Excess which causes a sedative effect and decreases deep tendon reflexes
• Excess the nervous system which excess calcium causing sedation, muscle weakness, kidney stones with bones
• May lead to Stones, Bones, Groans, Moans and Psychic Overtones

Treatment for Hypercalcemia

• Includes IV Saline and loop diuretics with IV phosphate
• Bisphosphonates for Osteoporosis with consideration for calcium excess, consider think SEDATED

Phosphorus

• Promotes the function of muscle, red blood cells (RBCs), and the nervous system
• Calcium is the inverse Food sources: beef, pork, dried peas/beans, cheese, shellfish, fish, pumpkin seeds
• Regulated by the parathyroid hormone wwithnormal phosphorus levels is 2.5 to 4.5 mg/dL

Causes of Hypophosphatemia: Serum Phosphate < 2.5 mg/dL

• Results from a Malnourished state and is caused by hyperparathyroidism and disorders

Treatment for Hypophosphatemia

• Involves administering phosphate-binding gels aluminum hydroxide and restricting dietary phosphorus

Magnesium

• Present in heart, bone, nerves, and muscle tissues and helps maintain electrical activity in nerves and muscle
• Acts like a sedative on muscle andfood sources include vegetables, nuts, fish, whole grains, peas, beans
• Magnesium levels are controlled by the kidneys at normal levels is 1.5 to 2.5 mEq/L

Causes of Hypomagnesemia: Serum Magnesium < 1.5 mEq/L

• Results from diarrhea, diuretics, and decreased intake with chronic alcoholism

Causes of Hypermagnesemia

• Renal failureand causes Increased oral or IV intake due Antacids

Treatment for Hypermagnesemia

• Involves Loop diuretics and 0.45% saline solution or IV calcium Gluconate
• Hemodialysis with magnesium free dialysate