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psc2019 > lecture 4 (renal) > Flashcards

lecture 4 (renal) Flashcards

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1
Q

how much of the body is water?

A
  • 60%
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2
Q

what is total body water affected by?

A
  • fat
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3
Q

where is the total body water found?

A
  • distributed between intracellular and extracellular compartments (interstitial and plasma)
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4
Q

how much is found in the intracellular compartment?

A
  • 2/3
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5
Q

how much is found in the extracellular compartment?

A
  • 1/3
  • 3/4 interstitial compartment
  • 1/4 plasma compartment
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6
Q

what is the intravascular compartment?

A
  • compartment that contains blood
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7
Q

what does the intravascular compartment contain?

A
  • blood consisting of cells and plasma
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8
Q

what is plasma?

A
  • noncellular portion of blood
  • consists of water and solutes
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9
Q

what is hematocrit?

A
  • percentage of blood volume that is red blood cells
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10
Q

what does hematocrit depend on?

A
  • number of RBCs
  • plasma volume
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11
Q

what is the concentration of a solute?

A
  • amount of solute dissolved in set volume of water
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12
Q

what is millimoles per litre?

A
  • number of particles of a solute contained in a litre of water
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13
Q

what does the anion gap identify?

A
  • abnormal increase in plasma anions
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13
Q

what is the anion gap based on?

A
  • tool based on principle of electroneutrality which is used to detect an abnormal increase in plasma anions
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14
Q

what represents the plasma cations?

A

sodium

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15
Q

what represents the plasma anions?

A
  • chloride and bicarbonate
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16
Q

what is the amount of water in each compartment dependent on?

A
  • osmotic pressure
  • hydrostatic pressure
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17
Q

what is osmotic pressure?

A
  • force exerted by solutes
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18
Q

what is hydrostatic pressure?

A
  • force exerted by water
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19
Q

what movement does osmotic pressure cause?

A
  • area of low to high concentration
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20
Q

when does osmotic pressure develop?

A
  • when a membrane is impermeable to a solute
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21
Q

what are the interstitial and plasma compartments separated by?

A
  • capillary membrane
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22
Q

what are the 4 types of intravenous fluids?

A
  • dextrose
  • saline
  • lactated Ringers
  • plasma expander
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23
Q

what does dextrose IVF contain?

A
  • dextrose
  • water
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24
what does saline IVF contain?
- Na+ - Cl- - water
25
what does lactated ringers contain?
- Na+ - Cl- - K+ - Ca2+ - lactate - water
26
what does plasma expander contain?
- solute which is restricted to the plasma compartment
27
what does isotonic concentration mean?
- osmolality similar to plasma
28
what does hypotonic concentration mean?
- osmolality less than plasma
29
what does hypertonic concentration mean?
- osmolality greater than plasma
30
what does IVF distribution depend on?
- its composition
31
where do the different IVFs distribute?
- dextrose = across all 3 compartments - saline = in extracellular compartment - lactated ringers = extracellular compartment - plasma expanders = remain within plasma compartment
32
what is dextrose?
- small uncharged molecule - able to cross capillaries and cell membranes
33
what is the purpose of dextrose solutions?
- to deliver water to the body
34
what is the most commonly used dextrose solution?
- D5W
35
what occurs after administration of D5W?
- metabolised to Co2 and H2O - used instead of pure water as isotonic to plasma
36
what is D5W used to treat?
- hypernatremia (too much sodium in blood)
37
what does isotonic saline do?
- delivers NaCl and water to plasma and interstitial compartments
38
when is isotonic saline used?
- to treat dehydration - in hypovolemia (low extracellular fluid volume)
39
what does hypotonic saline deliver?
- water to all three body compartments - NaCl to extracellular compartment
40
what is the equation for effective circulating volume?
volume = plasma volume and blood pressure
41
how is plasma volume increased?
- through reabsorption of sodium and water
42
what occurs in sodium resorption?
- mechanism to increase plasma volume - causes the reabsorption of water in proximal tubule - renal absorption of sodium occurs first
43
what occurs in water resorption?
- resorption of water alone occurs in collecting tubules of distal nephron - not as effective at increasing the plasma volume - only occurs when volume is very low
44
how is blood pressure calculated?
blood pressure = cardiac output x peripheral vascular resistance
45
what are the 3 steps of volume regulation?
- monitoring - signalling - action at targets
46
what signals act to increase plasma volume and blood pressure?
- renin-angiotensin II aldosterone - sympathetic stimulation - ADH
47
how is renin produced?
- by macula densa cells in the kidney
48
what does renin allow?
- conversion of angiotensinogen to angiotensin I
49
what does angiotensin I do?
- absorb more salt - vessels to constrict more - adrenal gland to make aldosterone
50
what occurs in pathway to release aldosterone?
- angiotensin released by liver - renin stimulates angiotensinogen to angiotensin I - causes salt uptake, vessel constriction - ace form lungs allows conversion of angiotensin I to II - aldosterone production from adrenal glands
51
where does angiotensin II act?
- at kidney to increase Na+ reabsorption - adrenal gland to increase aldosterone production/release - vasculature to constrict arteries and increase vascular resistance
52
where does ADH act?
- at kidney - causes resorption of water
53
what is atrial natriuretic peptide?
- volume regulatory hormone - decreases effective volume
54
what is osmoregulation?
- maintenance of consistent plasma osmolality
55
what do changes in plasma osmolality cause?
- change in cell volume - disruption of cell function
56
what detects changes in osmolality?
- hypothallamus
57
how can the osmolality of a solution be changed?
- change amount of water - change amount of solute
58
what does addition of water cause?
- decrease in osmolality
59
what does loss of solute cause?
- decrease in osmolality
60
how does the body change osmolality?
- by changing/adjusting water volume - through thirst and ADH
61
what does suppression of ADH cause?
- locking of collecting tubule - allows production of dilute urine
62
what does ADH (anti-diuretic hormone) do?
- decreases urine output
63
what is essential for ADH function?
- maintaining the concentrated medullary interstitium
64
what is hyponatremia (low sodium plasma levels) associated with?
- hypo-osmolality
65
what is true hyponatremia?
- associated with low plasma osmolality
66
what is pseudohyponatremia?
- hyponatremia associated with a normal or high plasma osmolality
67
what is hyponatremia with normal plasma osmolality due to?
- lab artifact from hyperlipidemia or hyperproteinemia
68
what is hyponatremia with high plasma osmolality due to?
- increased consternation of osmotically active particles eg. glucose, mannitol
69
what is true hyponatremia due to?
- relative excess of water
70
what is all forms of hyponatremia due to?
- ingestion of water in excess of amount the kidney can excrete
71
what is psychogenic polydipsia?
- disorder of compulsive water drinking - ingest large quantities of water so exceeds maximum daily urine volume
72
how does psychogenic polydipsia cause hyponatremia?
- by overwhelming normal kidneys with excessive water consumption
73
when does renal failure occur?
- when kidney is unable to excrete the daily solute load - metabolic waste accumulates in plasma - associated with diminished number of working nephrons
74
what does normal water consumption in patients with high ADH activity cause?
- hyponatremia
75
what is SIADH?
- syndrome of inappropriate ADH secretion - body makes too much ADH
76
what 4 characteristics is SIADH recognised by?
- hypotonic hyponatremia (low plasma osmolality and low plasma sodium conc) - euvolemia (normal volume) - high urine sodium concentration - high urine osmolality
77
why is both hyponatremia and hypoosmolaility present in SIADH?
- due to inability of kidney to excrete excess ingested water
78
what are the causes of SIADH?
- CNS diseases - ectopic production of ADH by tumours - HIV infection - medication - pulmonary diseases - stress, pain, nausea, emotions
79
what are hypernatremic patients always?
- hyperosmolar
80
what is hypernatremia?
- plasma sodium concentration greater then 145mEq/L - primary defence being thirst and ADH release
81
how is hypernatremia developed?
1. generation - gain of sodium/loss of water 2. maintenance - failure to sense thirst/unable to ingest water
82
what conditions predispose to hypernatremia?
- osmotic diuresis - diabetes insipidus (both cause increased urinary fluid loss)
83
what conditions does osmotic diuresis occur under?
- post obstruction diuresis - administration of mannitol - hyperglycaemia - uremia
84
what are the two categories of diabetes insipidus?
- central - nephrogenic
85
what is central diabetes insipidus characterised by?
- inability of brain to release ADH
86
what is nephrogenic diabetes insipidus characterised by?
- inability of kidney to respond to ADH
87
what is diabetes insipidus?
- characterised by inability to produce concentrated urine due to decreased ADH activity - patients produce large volume of dilute urine

psc2019 (19 decks)

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