Fluid Balance Flashcards
What are the two pressures present in a capillary?
Hydrostatic pressure and oncotic/colloid osmotic pressure
Is hydrostatic pressure higher at the arteriole end or venule end of a capillary?
Higher at the arteriole end
Is oncotic/colloid osmotic pressure relatively greater or smaller than the hydrostatic pressure at the venule end of a capillary?
Relatively greater
Is oncotic/colloid osmotic pressure relatively greater or smaller than the hydrostatic pressure at the arteriole end of a capillary?
Relatively smaller
Does all fluid that leaves the capillary due to hydrostatic pressure return to the capillary?
No, only about 90% of it returns to the capillary
Where does the fluid that doesn’t return to the capillary go?
It drains into the lymph system which returns the fluid to the cardiovascular system
How is the thirst response activated?
Hypothalamic osmoreceptors detect increased blood osmolality, triggering the thirst centre in the hypothalamus to create the thirst response
What does Antidiuretic hormone (ADH) do in relation to fluid loss?
ADH keeps fluid within the body and decreases urine excretion, resulting in a more concentrated urine and decreased blood osmolality
What triggers the Renin-Angiotensin-Aldosterone System (RAAS) to activate?
Low blood volume (specifically decreased perfusion to the kidneys)
Where is Renin secreted from?
The juxtaglomerular cells in nephrons
In the Renin-Angiotensin-Aldosterone System (RAAS), Renin allows what conversion to happen?
Renin allows the conversion of Angiotensinogen into Angiotensin 1
Where is Angiotensinogen created?
In the liver
How is Angiotensin 1 converted into Angiotensin 2?
It’s converted by Angiotensin Converting Enzyme (ACE)
What is the effect of Angiotensin 2 on the Adrenal Glands?
It causes the adrenal glands to release aldosterone, stimulating sodium and water reabsorption in the kidneys
What is the effect of Angiotensin 2 on the Arterioles?
It causes vasoconstriction
What is the effect of Angiotensin 2 on the Hypothalamus?
It stimulates the hypothalamus to trigger the thirst response, causing the body to drink water and increase blood volume
What is the effect of Angiotensin 2 on the Posterior Pituitary gland?
It stimulates the Posterior Pituitary gland to release ADH, increasing water reabsorption in the kidneys
Overall, what is the effect of Angiotensin 2 on blood volume?
It increases blood volume
What triggers the release of Atrial Natriuretic Peptide (ANP)? Where is it secreted from?
High blood volume and pressure, leading to secretion from atrial muscle cells in the heart
What is the effect of Atrial Natriuretic Peptide (ANP) on the Renin-Angiotensin-Aldosterone System (RAAS)?
ANP inhibits the secretion of Renin, ADH and Aldosterone
What is the effect of Atrial Natriuretic Peptide (ANP) on water and sodium in the kidneys?
It increases water and sodium excretion, increasing urine output and decreasing blood volume
What may cause Hypervolemia (Fluid volume excess)?
Too much in:
Drinking too much (Polydipsia)
Excessive IV fluid administration
Too little out:
Renal impairment
Heart Failure (tricks kidneys into thinking there’s a low blood volume, triggers RAAS)
Liver Failure
What are some symptoms of Hypervolemia (Fluid Volume Excess)?
Increased Urination (Polyuria),
Headache and confusion,
Seizures and Coma,
Bulging (Distended) neck veins, increased blood volume and heart rate,
Oedema (Pulmonary oedema may include shortness of breath (dyspnoea) and coughing),
Weight gain
What are some treatments for Hypervolemia?
Restriction of fluid and sodium intake,
Diuretics,
Close fluid balance monitoring,
Dialysis
What may cause Hypovolemia?
Bleeding, vomiting, urinating, diarrhoea (among other things)
At what percentage of body water loss may Hypovolemia become fatal?
Around 20%
10% causes serious signs and symptoms
What are some symptoms of Hypovolemia?
Poor skin turgor (if you pinch the back of your hand and it doesn’t spring back),
Dry mucous membranes,
Thirst,
Lower urine ouput, heart rate and blood pressure,
Orthostatic hypotension (low blood pressure when standing up from sitting or lying down),
Confusion
What are some treatments for Hypovolemia?
Rehydration
IV Fluid replacement
Replacement of Blood
Electrolyte imbalance corrections
