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Questions and Answers
What role does ADH play in fluid balance?
What role does ADH play in fluid balance?
Which of the following conditions is most likely associated with hypoproteinaemia?
Which of the following conditions is most likely associated with hypoproteinaemia?
What percentage of total body potassium (K) is found within the cells?
What percentage of total body potassium (K) is found within the cells?
Which mechanism operates primarily to reduce plasma oncotic pressure in cases of hypoproteinaemia?
Which mechanism operates primarily to reduce plasma oncotic pressure in cases of hypoproteinaemia?
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In the context of postoperative management, which parameter should be assessed as part of baseline values?
In the context of postoperative management, which parameter should be assessed as part of baseline values?
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What characterizes hyponatraemia in the context of fluid balance?
What characterizes hyponatraemia in the context of fluid balance?
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Which body fluid loss is most commonly combined with sodium loss?
Which body fluid loss is most commonly combined with sodium loss?
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What is a normal concentration of potassium in the intracellular fluid (ICF)?
What is a normal concentration of potassium in the intracellular fluid (ICF)?
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Which of the following is least likely to cause severe dehydration in infants?
Which of the following is least likely to cause severe dehydration in infants?
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Which factor primarily leads to oedema in patients with increased sodium in the blood?
Which factor primarily leads to oedema in patients with increased sodium in the blood?
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What is the primary compartment where sodium is predominantly found in the human body?
What is the primary compartment where sodium is predominantly found in the human body?
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Which factor significantly influences the distribution of fluid between intracellular and extracellular compartments?
Which factor significantly influences the distribution of fluid between intracellular and extracellular compartments?
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What effect does arginine vasopressin (AVP) have on water balance in the body?
What effect does arginine vasopressin (AVP) have on water balance in the body?
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What physiological response occurs when plasma osmolality increases?
What physiological response occurs when plasma osmolality increases?
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In cases of vomiting, which electrolyte is lost significantly while sodium levels tend to remain high?
In cases of vomiting, which electrolyte is lost significantly while sodium levels tend to remain high?
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Which ratio indicates renal tubular deficiency after fluid restriction?
Which ratio indicates renal tubular deficiency after fluid restriction?
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What is the calculated formula for osmolality?
What is the calculated formula for osmolality?
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What is the role of thirst in external fluid balance?
What is the role of thirst in external fluid balance?
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What daily fluid loss occurs in severe illness due to large secretions into the gut?
What daily fluid loss occurs in severe illness due to large secretions into the gut?
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Which component primarily regulates sodium excretion in the kidneys?
Which component primarily regulates sodium excretion in the kidneys?
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What is the recommended volume of isotonic saline to replace for sweating if the patient shows clear symptoms?
What is the recommended volume of isotonic saline to replace for sweating if the patient shows clear symptoms?
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What is the concentration of NaCl in isotonic saline solution expressed in mmol?
What is the concentration of NaCl in isotonic saline solution expressed in mmol?
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Which solution should be used for additional water and dextrose in a patient with water depletion?
Which solution should be used for additional water and dextrose in a patient with water depletion?
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What is the maximum serum potassium concentration that can be fatal if exceeded?
What is the maximum serum potassium concentration that can be fatal if exceeded?
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In a case of low urine output, what should be done to the fluid flow rate?
In a case of low urine output, what should be done to the fluid flow rate?
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What is the essential requirement of potassium to be covered in mmol/l?
What is the essential requirement of potassium to be covered in mmol/l?
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When should a diuretic be considered during fluid management?
When should a diuretic be considered during fluid management?
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What solution contains potassium chloride for correcting gastrointestinal disturbances?
What solution contains potassium chloride for correcting gastrointestinal disturbances?
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Which electrolyte has a normal plasma concentration range of 3.5-5.5 mmol/l?
Which electrolyte has a normal plasma concentration range of 3.5-5.5 mmol/l?
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What is the molarity of NaCl in an isotonic saline solution expressed as mol/l?
What is the molarity of NaCl in an isotonic saline solution expressed as mol/l?
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Study Notes
Water & Electrolyte Balance Disturbances
- Disturbances can be external or internal.
- External disturbances: Input and output balance maintains constant amounts of Na, K, and water in the body.
Daily Water Intake and Output (Healthy Adult)
-
Intake:
- Water drunk: 1500 mL
- Water in food: 750 mL
- Water from metabolism: 250 mL
- Total intake: 2500 mL
-
Output:
- Urine volume: 1600 mL
- Faecal water content: 50 mL
- Loss in expired air: 850 mL
- Insensible perspiration: ? mL
- Total output: 2500 mL
Daily Intake and Output of Electrolytes (Na, K, Cl)
- All values in mmol/24 h
- Ion | Intake | Urine | Faeces | Skin
- Na | 100-200 | 100-200 | <5 | <5
- K | 20-100 | 20-100 | <5 | Trace
- Cl | 100-200 | 100-200 | <5 | <5
Distribution of Water in Adults and Infants
- Adult (70 kg) | Percentage of body weight | Infant (3.0 kg)
- Extracellular fluid | 20 | 70
- Plasma | - | 40
- Interstitial fluid| - | 30
- Intracellular fluid | 40 | ?
- Total body water | 60 | 70
Water in the Digestive Tract
- Secretions are reabsorbed into the body.
- Severe illness results in the loss of water and electrolytes because the volumes of these fluids secreted daily are high.
- Examples:
- Vomiting: High Cl loss & high Na
- Diarrhea: Relative loss of various electrolytes(relative to each other)
Water & Sodium Balance
- Total body Na is approximately 4200 mmol, 50% in extracellular fluid (ECF), 40% in bone, and 10% in intracellular fluid (ICF).
Internal Balance
- Distribution of fluid between intracellular fluid (ICF), intravascular fluid, and extravascular fluid is influenced by:
- Osmolality (285-295 mmol/kg): Affects water movement across membranes.
- Colloid osmotic pressure: Affects movement within the extracellular fluid compartments.
Osmolality
- Measured by osmometer (freezing point depression).
- Calculated Osmolality: 2[Na] + 2[K] + Glucose/18 + Blood Urea/6
- Normal urine osmolality/serum osmolality ratio is 1-3.
External Balance (Water)
- Thirst triggers increased water intake.
- Arginine vasopressin (AVP, or ADH) promotes water retention by the kidneys.
- Increased plasma osmolality enhances thirst sensation.
- Decreaesed ECF volume by 10% stimulates thirst.
Sodium Excretion
- Key regulators:
- Glomerular filtration rate (GFR)
- Renin-angiotensin-aldosterone system
- Atrial natriuretic peptides (ANP)
- Dopamine release in the kidney
Antidiuretic Hormone (ADH)
- ADH leads to water retention in the extracellular fluid volume.
- Mediated by osmoreceptors in the hypothalamus.
Depletion & Excess of Water
- Usual case concerns NA+ water loss.
- Examples of causes: Inadequate intake, abnormal losses (skin, renal, gastro-intestinal.)
- Excesses include excessive intake.
Na Depletion & Excess
- Increase in Na in the blood increases water retention due to hypoproteinemia and hydrostatic factors.
- Hypoproteinemia reduces plasma oncotic pressure, decreasing fluid reabsorption.
- Increased venous pressure due to hydrostatic factors can contribute to fluid retention.
Hypernatremia
- Elevated sodium levels in the blood.
- Often caused by water loss and/or increased sodium intake.
Hyponatremia
- Low sodium levels in the blood
- Caused by excessive water intake, inappropriate ADH secretion, or renal dysfunction
Potassium Balance
- Potassium is the main intracellular cation (98%).
- Remaining 2% is in the extracellular fluid (ECF), 150 mmol/l ICF, 4 mmol/l ECF).
- Hemolysed blood specimen potassium analysis yields a falsely high result.
Fluid Balance (Post-Operative Management)
- Patients post-surgery may experience fluid and electrolyte imbalances.
- Preoperative assessment to establish baseline values (NA, K, Cl, blood urea, creatinine, liver function).
- Assess severity and implement corrective measures
- Corrective fluid requirements:
- Insensible loss replacement (600ml).
- Previous daily urine volume.
Intravenous Preparations in Fluid Balance
- Normal saline: 0.9% NaCl.
- Dextrose solutions: vary depending on patient need (e.g., 5% for adults, 0.3% for infants).
- Ringer's solution: contains Na, K, Cl, and other electrolytes.
Calculation of Normal Saline Solution Concentration
- 0.9% normal saline corresponds to 0.154 mol NaCl/L.
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Description
Explore the crucial aspects of water and electrolyte balance in the human body. This quiz covers external and internal disturbances, daily intake and output of water and electrolytes, and the distribution of water in adults and infants. Test your knowledge on maintaining homeostasis through proper hydration and electrolyte management.
