Pathophyis of fluid loss Flashcards
(18 cards)
What is hypovolaemia?
Deficit of fluid from the intravascular space
Interstitial and intracellular fluid volumes may initially be unchanged.
What are the causes of hypovolaemia?
- Haemorrhage
- Third spacing
- Severe dehydration
How does dehydration initially affect intravascular volume?
Intravascular volume is protected until dehydration becomes moderate to severe
Severe dehydration can lead to hypovolaemia.
What is relative hypovolaemia?
Abnormal vasodilation with unchanged total intravascular volume
What happens to the central circulation during relative hypovolaemia?
Blood pools in dilated capillaries, depleting the central circulation
What disease processes can lead to relative hypovolaemia?
- Sepsis
- Anaphylaxis
What is dehydration?
Deficit of fluid within the interstitial and intracellular spaces
What causes dehydration?
- Lack of fluid intake
- Fluid loss (diarrhoea, vomiting, polyuria, excessive panting, high body temperature)
What is the immediate homeostatic response to fluid loss?
Maintaining delivery of oxygen to tissues when intravascular volume drops
What do baroreceptors detect during hypovolaemia?
Decreased stretch of the arterial wall
What is the result of baroreceptor stimulation?
- Increased heart rate
- Increased contractility
- Peripheral vasoconstriction
What does the transcapillary refill process do?
Causes net fluid flux into vessels, borrowing fluid from the interstitium
What activates the renin-angiotensin-aldosterone system (RAAS)?
Decreased circulating fluid volume
What role does angiotensin II play in fluid retention?
Increases sodium and water reabsorption in the proximal tubule
What stimulates the release of antidiuretic hormone (ADH)?
- Increased osmolality
- Circulating angiotensin II
What effects does ADH have on the kidneys?
Increases renal retention of water by increasing permeability of renal collecting ducts
