2P07 Class 4

What proportion of adult body weight is comprised of total body water (TBW)?

Approximately 60% of total adult body weight (measured in kilograms).

What is the equivalent weight conversion ratio for pure body water?

1 L of water weighs 1 kg.

Intracellular fluid (ICF) accounts for approximately what fraction of total body water (TBW)?

Two-thirds (2/3)

What fraction of total body water (TBW) is located in the extracellular fluid (ECF) compartment?

Approximately one-third (1/3) of TBW.

What two primary sub-compartments constitute the Extracellular Fluid (ECF)?

1. Interstitial fluid (space between cells and outside blood vessels)

2. Intravascular fluid (blood plasma)

What are the standard fluid volumes in liters for Plasma, Interstitial Fluid (IF), and Intracellular Fluid (ICF) in an adult?

• Plasma: 3 L

• Interstitial fluid (IF): 10 L

• Intracellular fluid (ICF): 28 L

What defines an isotonic solution in relation to body cells?

A solution that has the same osmolality as the interior of the cell.

What defines a hypotonic (hypo-osmolar) solution?

A solution in which solutes are less concentrated than they are inside the cell.

What defines a hypertonic (hyperosmolar) solution?

A solution in which solutes are more concentrated than they are inside the cell.

What morphological changes occur in red blood cells when placed in Hypotonic (A), Isotonic (B), and Hypertonic (C) solutions?

• A (Hypotonic): Water flows in, causing cell swelling and lysis.

• B (Isotonic): Equal water flux, preserving normal shape.

• C (Hypertonic): Water exits, causing crenation (shrinkage).

What is the primary extracellular cation in the human body? What % does it account for?

Sodium (Na+), which accounts for 90% of all ECF cations.

What is the normal extracellular concentration of sodium (Na+) compared to its intracellular concentration?

• ECF Sodium: 142 mmol/L

• ICF Sodium: 12 mmol/L

What is the primary intracellular cation in the human body? Values?

Potassium (K+), with an extra cellular concentration of 4.2 mmol/L compared to 150 mmol/L in intracellular concentration

What is the dominant anion in the extracellular fluid (ECF)? What are the values

Chloride (Cl-), at 103 mmol/L in ECF versus 4 mmol/L in ICF.

What is the primary anion present in the intracellular fluid (ICF)? Values?

Phosphate, at 2 mmol/L in ECF versus 100 mmol/L in ICF.

List three physiological functions of Sodium (Na+) in the body.

1. Maintenance of neuromuscular irritability

2. Regulation of acid-base balance

3. Cellular chemical reactions and membrane transport

What cellular fluid shift occurs in hypernatremia, and what is its primary outcome?

Water shifts out of the ICF into the hypertonic ECF, resulting in cellular dehydration.

How does anti-diuretic hormone (ADH) dysfunction cause hypernatremia?

A deficiency in ADH synthesis/release or renal unresponsiveness leads to massive diuresis (kidney filters excess fluid and sodium, increased urine production and frequency) and water loss.

Why does hyperglycemia in uncontrolled diabetes mellitus lead to hypernatremia?

High blood glucose creates osmotic diuresis, causing excessive water loss in excess of sodium loss.

List the clinical manifestations associated with hypernatremia.

Intense thirst, lethargy, agitation, seizures, and coma.

What pathophysiology causes cellular edema in hyponatremia?

Low ECF osmolality causes fluid to shift out of the hypotonic ECF into the cells.

List three common causes of hyponatremia.

1. Inappropriate sodium-free/hypotonic IV fluids

2. Psychogenic polydipsia

3. Syndrome of Inappropriate Antidiuretic Hormone (SIADH)

Differentiate between mild and severe clinical manifestations of hyponatremia.

• Mild: Headache, irritability, concentration difficulty.

• Severe: Confusion, vomiting, seizures, coma.

What cardiovascular parameters should nurses monitor during fluid balance assessment?

Changes in blood pressure, pulse force, and jugular venous distension/visibility.

Which respiratory assessment findings in terms of lung sounds indicate fluid volume excess?

Shortness of breath, irritative cough, and moist crackles upon lung auscultation.

What skin parameters should be evaluated during a nursing assessment for fluid status?

Skin turgor, elasticity, and presence/degree of edema.

How does metabolic acidosis cause hyperkalemia?

Hydrogen ions (H+) enter cells to be buffered, forcing potassium ions (K+) out of the ICF into the ECF.

List three common clinical causes of hyperkalemia resulting from cell destruction or metabolic shifts.

1. Massive cell destruction (burns, crush injuries, tumor lysis)

2. Rapid transfusion of aged stored blood

3. Severe catabolic states

What effect does hyperkalemia have on cell membrane potential and muscle function?

It causes membrane depolarization, altering cell excitability and leading to skeletal muscle weakness or paralysis.

What is often the earliest physical symptom of hyperkalemia?

Leg cramping.

What distinct ECG abnormalities occur during hyperkalemia?

Tall peaked T waves, widened QRS complexes, prolonged P-R intervals, and depressed ST segments.

List 1 key nursing management strategies for treating hyperkalemia. (number 4)

1. Eliminate oral/parenteral potassium

2. Increase potassium elimination

3. Shift potassium from ECF to ICF

4. Administer IV Calcium Gluconate

How does hypomagnesemia contribute to hypokalemia?

Low plasma magnesium stimulates renin release, increasing aldosterone secretion and renal potassium excretion.

How does metabolic alkalosis promote hypokalemia?

Extracellular H+ shifts out of cells to compensate, forcing K+ into cells in exchange, lowering ECF potassium.

What cellular membrane potential change occurs in hypokalemia?

Hyperpolarization (increased negative charge inside cells), impacting cardiac, respiratory, and muscle function.

What distinct ECG changes characterize hypokalemia?

Flattened/shallow T waves, prominent U waves, and ST depression.

What key nursing safety interventions are required when administering intravenous potassium chloride (KCl)?

1. Continuous cardiac monitoring

2. Monitoring for infusion site pain/phlebitis

What is the defining feature of edema?

Excessive accumulation of fluid in the interstitial spaces.

List the four main pathophysiological mechanisms that cause edema.

1. Increased capillary hydrostatic pressure

2. Decreased plasma oncotic pressure

3. Increased capillary membrane permeability

4. Lymphatic channel obstruction

What two mechanisms lead to an increase in capillary hydrostatic pressure?

1. Venous obstruction

2. Sodium and water retention

Name three systemic clinical conditions frequently associated with elevated capillary hydrostatic pressure edema.

1. Heart failure

2. Renal failure

3. Cirrhosis of the liver

How does albumin deficiency result in generalized edema?

Reduced albumin decreases plasma oncotic pressure, reducing water retention within the vascular space.

How do burns and crushing injuries cause edema?

They trigger inflammatory responses that increase capillary membrane permeability, leaking plasma proteins into the interstitium.

What clinical sign of edema is demonstrated by indentations remaining in the tissue after pressure is applied?

Pitting edema.

What mechanism causes lymphedema following surgical carcinoma resection?

Obstruction or surgical removal of lymphatic channels blocking normal drainage and causing fluid accumulation.

What is the normal physiologic target range for arterial blood pH in human body fluids?

7.35 to 7.45

What is the mathematical relationship between hydrogen ion concentration ([H+]) and blood pH?

Inverse relationship: increased [H+] decreases pH (acidosis); decreased [H+] increases pH (alkalosis).

List the three main body organs involved in regulating acid-base balance.

Lungs, kidneys, and bones.

At what lower and upper arterial pH limits does death typically occur?

Lower limit: pH 6.80; Upper limit: pH 7.80.

To maintain a normal blood pH, what ratio must be maintained between carbonic acid and bicarbonate?

1 part carbonic acid to 20 parts bicarbonate.

What is a volatile acid in human physiology, and how is it eliminated?

Carbonic acid (H2CO3), which converts into CO2 and H2O and is eliminated by the lungs.

What are nonvolatile acids, and how are they excreted from the body?

Strong metabolic organic acids excreted by the renal tubules into the urine.

What constitutes a chemical buffer system in human physiology?

A weakly ionized acid or base and its salt to minimize blood pH changes.

What is the primary extracellular buffer system in the body?

The carbonic acid-bicarbonate buffer system (H2CO3 / HCO3-).

Write the chemical equation illustrating how sodium bicarbonate buffers hydrochloric acid.

HCl + NaHCO3 → NaCl + H2CO3

Note - the purpose of the buffer is to weaken the acid. Even though you still end up with an acid after the equation, it is a weaker acid which the body is able to break down.

How do the lungs and brainstem respond to decreased blood pH?

Low pH stimulates the brainstem respiratory center, increasing respiration rate and depth to blow off CO2.

What is the kidney's direct compensatory action when blood pH drops?

Renal tubules increase the rate of hydrogen ion (H+) secretion into urine.

What respiratory abnormality leads directly to carbonic acid excess (respiratory acidosis)?

Hypoventilation, leading to CO2 buildup (hypercapnia).

List four underlying causes of respiratory center depression leading to respiratory acidosis.

1. Depressant medications

2. Head injury

3. Respiratory muscle paralysis

4. Chest wall or lung parenchyma disorders

How do the kidneys compensate during chronic respiratory acidosis?

The kidneys conserve bicarbonate (HCO3-) ions and secrete increased hydrogen (H+) into urine.

What is the primary mechanism of respiratory alkalosis?

Hyperventilation causing excessive CO2 exhaling, leading to carbonic acid deficit and increased pH.

How do systemic illnesses like severe COPD or kidney disease alter acid-base balance?

COPD impairs CO2 excretion causing respiratory acidosis; kidney disease impairs H+ excretion and HCO3- reabsorption causing metabolic acidosis.

Why are older adults at heightened risk for fluid and acid-base imbalances?

Decreased renal function, reduced thirst sensation, lower total body water percentage, and diminished reserve.

What enzyme catalyzes the conversion of carbon dioxide and water into carbonic acid in red blood cells?

Carbonic Anhydrase

How is carbon dioxide (CO2) primarily transported in human blood plasma and erythrocytes?

1. As bicarbonate ions (~70%)

2. Bound to hemoglobin (~23%)

3. Dissolved CO2 gas (~7%)

What clinical condition results from a loss of acid through severe vomiting or gastric suction?

Metabolic Alkalosis

Severe prolonged diarrhea causes loss of bicarbonate-rich fluids, leading to what condition?

Metabolic Acidosis

What is the effect of elevated serum aldosterone levels on sodium and potassium renal handling?

Stimulates renal reabsorption of sodium (Na+) and increases urinary excretion of potassium (K+).

Why is daily weight measurement the most accurate indicator of acute fluid gain or loss?

Because 1 L of fluid equals exactly 1 kg of body mass, reflecting rapid volume shifts.

What neurological assessments are critical for monitoring patients with acute sodium imbalances?

Level of Consciousness (LOC), pupillary response, and voluntary motor movement/strength.

What is the primary rationale for administering Calcium Gluconate IV in acute severe hyperkalemia?

To stabilize cardiac cell membrane potential and counteract myocardial toxicity without lowering blood K+.

How does insulin administration help lower extracellular hyperkalemia?

Insulin stimulates the Na+/K+ ATPase pump, forcing potassium from ECF back into the ICF.

What distinguishes volatile acids from nonvolatile acids regarding their production end-products?

Volatile acids originate from gaseous CO2 metabolism; nonvolatile acids originate from cellular breakdown of proteins, carbs, and fats.

What buffer exchange occurs between ICF and ECF during severe extracellular hydrogen ion overload?

Excess ECF hydrogen ions (H+) move into cells in exchange for potassium (K+) moving out into ECF.

How does kyphoscoliosis cause chronic respiratory acidosis?

It restricts mechanical lung expansion, leading to chronic alveolar hypoventilation and CO2 retention.

What osmotic force promotes fluid movement out of the arterial end of capillaries into tissue interstitial space?

Capillary Hydrostatic Pressure

What vascular force holds water inside the capillary bed preventing tissue edema?

Plasma Oncotic Pressure

Why does liver cirrhosis cause both ascites (abnormal buildup of excess fluid inside the peritoneal cavity) and generalized tissue edema?

Reduced albumin synthesis decreases oncotic pressure, while portal hypertension increases hydrostatic pressure.