Podcast
Questions and Answers
What is the predominant ion in the extracellular fluid (ECF)?
What is the predominant ion in the extracellular fluid (ECF)?
How is osmolality primarily measured?
How is osmolality primarily measured?
What is the osmolal gap (OG) when the osmolality is 290 mOsm/kg and the osmolarity is 275 mOsm/kg?
What is the osmolal gap (OG) when the osmolality is 290 mOsm/kg and the osmolarity is 275 mOsm/kg?
What percentage of the body's water is found in the intracellular fluid (ICF)?
What percentage of the body's water is found in the intracellular fluid (ICF)?
Signup and view all the answers
What minimum volume of urine is required for adequate waste excretion?
What minimum volume of urine is required for adequate waste excretion?
Signup and view all the answers
What primarily influences urinary potassium excretion?
What primarily influences urinary potassium excretion?
Signup and view all the answers
Which of the following can cause hypokalaemia through transcellular potassium movement?
Which of the following can cause hypokalaemia through transcellular potassium movement?
Signup and view all the answers
Which renal condition is associated with an increased potassium excretion that can lead to hypokalaemia?
Which renal condition is associated with an increased potassium excretion that can lead to hypokalaemia?
Signup and view all the answers
What is a common extra renal cause of hypokalaemia?
What is a common extra renal cause of hypokalaemia?
Signup and view all the answers
Which of the following is classified as a spurious cause of hyperkalaemia?
Which of the following is classified as a spurious cause of hyperkalaemia?
Signup and view all the answers
Which condition can lead to hyperkalaemia due to transcellular movement?
Which condition can lead to hyperkalaemia due to transcellular movement?
Signup and view all the answers
What role does sodium play in relation to potassium and water homeostasis?
What role does sodium play in relation to potassium and water homeostasis?
Signup and view all the answers
Which of the following is a consequence of not properly managing electrolyte disorders?
Which of the following is a consequence of not properly managing electrolyte disorders?
Signup and view all the answers
What is the minimum obligatory loss of urine output by the kidneys in 24 hours?
What is the minimum obligatory loss of urine output by the kidneys in 24 hours?
Signup and view all the answers
Which of the following conditions is characterized by a plasma sodium concentration below 135 mmol/L?
Which of the following conditions is characterized by a plasma sodium concentration below 135 mmol/L?
Signup and view all the answers
What can be a consequence of a rapid decline in sodium levels?
What can be a consequence of a rapid decline in sodium levels?
Signup and view all the answers
What are the first-line treatment options for a patient with hypervolaemia and hypernatraemia?
What are the first-line treatment options for a patient with hypervolaemia and hypernatraemia?
Signup and view all the answers
Which of the following is NOT a condition that may cause hyponatraemia?
Which of the following is NOT a condition that may cause hyponatraemia?
Signup and view all the answers
What physiological response do cells have to prevent an increase in intracellular volume during hyponatraemia?
What physiological response do cells have to prevent an increase in intracellular volume during hyponatraemia?
Signup and view all the answers
Which diagnostic criteria is essential to confirm the syndrome of inappropriate ADH (SIADH)?
Which diagnostic criteria is essential to confirm the syndrome of inappropriate ADH (SIADH)?
Signup and view all the answers
In hypernatraemia, what is often the first step in determining management?
In hypernatraemia, what is often the first step in determining management?
Signup and view all the answers
What is the primary renal process that affects potassium homeostasis?
What is the primary renal process that affects potassium homeostasis?
Signup and view all the answers
When hypernatraemia occurs due to water loss, when does ECF depletion typically appear?
When hypernatraemia occurs due to water loss, when does ECF depletion typically appear?
Signup and view all the answers
What happens during cerebral adaptation to hyponatraemia?
What happens during cerebral adaptation to hyponatraemia?
Signup and view all the answers
What is a possible outcome of aggressive treatment of chronic hyponatraemia?
What is a possible outcome of aggressive treatment of chronic hyponatraemia?
Signup and view all the answers
Which factor is typically NOT considered when addressing hyponatraemia?
Which factor is typically NOT considered when addressing hyponatraemia?
Signup and view all the answers
Study Notes
Fluid and Electrolytes
- Body water content is 60% of body weight in males and 55% in females.
- 66% of body water is intracellular fluid (ICF) and 33% is extracellular fluid (ECF).
- Only 8% of ECF is plasma.
- Water movement between compartments is determined by osmotic content.
- Water is obtained from food and metabolic processes.
- Water is lost through kidneys, intestines, lungs, and skin.
- Approximately 170 liters of water are filtered by the kidneys daily.
- Adequate urine output is 500mL/24hr.
- Intracellular fluid (ICF) has high potassium (K+) concentration while extracellular fluid (ECF) has high sodium (Na+) concentration.
- Na+/K+-ATPase maintains intracellular and extracellular ion concentrations.
Osmolality and Osmolarity
- Osmolality is measured using an osmometer which determines freezing point depression.
- Osmolarity is calculated by the formula 2[Na+] + [urea] + [glucose].
- Osmolal gap (OG) is calculated by subtracting osmolarity from osmolality (OG = osmolality - osmolarity).
- High osmolal gaps (typically above 10 or 15) often indicate an underlying medical condition like diabetic ketoacidosis or ethylene glycol poisoning.
Physiological Response to Water Loss
- Water loss increases ECF osmolality.
- This triggers vasopressin release and stimulates the thirst centre in the hypothalamus.
- The body redistributes water from ICF to ECF.
- The kidneys retain water.
- Increased water intake restores ECF osmolality.
Water and Sodium Homeostasis
- Water intake is variable and influenced by factors like availability, diet, habit, and social factors.
- Kidneys regulate urine volume and concentration.
- Obligatory urine output is approximately 500mL/24hr.
- Renin-angiotensin-aldosterone (RAA) system and Antidiuretic hormone (ADH) are key homeostatic mechanisms.
Regulation of Na⁺ and H₂O Balance
- ECF volume affects water balance and blood volume.
- Factors including blood loss, low cardiac output, and increased capillary permeability (e.g., sepsis) affect water balance.
- A complex system involving hormones, the kidneys, and changes in blood pressure restore balance and blood volume.
Hyponatremia
- Hyponatremia occurs when plasma sodium concentration is below the normal range (~135 mmol/L).
- Pseudo-hyponatremia can be caused by factors such as high blood lipids or proteins, which must be ruled out.
- Symptoms become apparent at lower concentrations, below 125 mmol/L.
- The rate of sodium decrease is important, as chronic hyponatremia can be asymptomatic but a rapid drop can be dangerous.
- Different approaches to treating hyponatremia depending on the volume of extracellular fluid.
Hyponatremia (Approach)
- Assessing extracellular fluid (ECF) volume helps differentiate between hypervolemia, euvolemia, and hypovolemia.
- Different treatment approaches are used for different fluid volumes (e.g., diuretics for hypervolemia, fluid restriction for euvolemia, saline rehydration for hypovolemia).
Syndrome of Inappropriate ADH (SIADH)
- SIADH is a diagnosis of exclusion.
- It's diagnosed when hyponatremia and low serum osmolality are present along with low urine osmolality (~100 mOsm/kg).
- Normal ECF volume and normal renal, adrenal, and thyroid function rule out other causes.
- Patient needs to be free of medications that cause hyponatremia.
Hypernatremia
- Hypernatremia occurs when the serum sodium concentration is above 145 mmol/L.
- Causes include inadequate water intake or excessive water loss (e.g., osmotic diuresis, diarrhea, sweating).
- Hypernatremia may not occur in a conscious individual with access to water.
- Different treatment approaches depending on volume status are required
Cerebral Adaptation
- The brain adapts over 2-3 days to sodium changes.
- In response to changes in intracellular/extracellular sodium concentrations, the brain changes its osmolarity.
- Rapid correction of electrolyte imbalance can lead to damaging neurological consequences.
Potassium Homeostasis
- Potassium is primarily reabsorbed in the proximal tubules in the kidney.
- Active secretion occurs in the distal tubules.
- Factors like aldosterone levels, sodium concentration, and the presence of hydrogen ions influence potassium excretion.
- Electrolyte imbalance is influenced by diet, fluid intake, and kidney function.
Summary/Conclusions
- Sodium, potassium, and water balance are interconnected.
- Electrolytes are actively transported, with water following passively.
- Hyponatremia and hypernatremia are vital electrolyte disturbances requiring thorough assessment and management.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on the essential concepts of fluid and electrolytes, including body water content, fluid compartments, and osmolality versus osmolarity. This quiz covers critical information about how water balance is maintained in the human body. Ideal for students in health sciences or related fields.
