Question | Answer |
Hyponatremia | Too much water relative to Na
:
Na <135 mmole/L |
Hypernatremia | Too little water relative to Na
:
Na >144 mmole/L |
Osmolality | Concentration of ALL solutes |
Tonicity | Concentration of solutes that will cause a water shift
:
E.g. Na & Cl, not Urea |
True (absolute) Hypovolemia | Hemorrhage, GI fluid loss, Diuretics, Burns |
Relative Hypovolemia | Increased capacitance of the compartment : either from vasodilation (drugs, sepsis, NO) or decreased effective arterial blood flow (edema and third spacing) |
Primary Renal Hypervolemia | Na/water rentention from renal disease |
Secondary Renal Hypervolemia | Na/water retention from systemic diseases such as cardiac failure and cirrhosis |
Name the 5 hormonal regulators of Na | (1) Aldosterone (2) ADH (3) ANP (4) Sympathetic Nervous System (5) Angiotensin II |
Effects of Angiotensin II and NE in the proximal tubule | Tweek (1) the Na/H exchanger on the lumenal side and (2) the Na/K pump on the interstitial side |
Effects of Aldosterone in the Cortical Collecting Duct Principal Cells | Increases activity of (1) ENaC and (2) Aquaporin channels on the lumenal side and (3) Na/K pump on the interstitial side. |
Where does ADH work to increase Na reabsorption? | The thick ascending limb and CCD |
How does ADH effect Urea | It increases Urea transport in the intermedullary collecting duct |
How does ADH increase water reabsorption? | With the insertion of acquaporin channels in the collecting duct |
What is the equation associated with Na excretion | Filtered load of Na (GFR X plasma [Na]) - tubular reabsorption of Na |
What does ANP do (generally) | Increases the excretion of Na and water |
Name the three controllers of water balance. | Osmolality, Volume, Angiotensin |
In the presence of competing volume and osmolality signals, which one wins? | Volume always wins |
Increase/decrease of which factors will increase ADH? | Increase in osmolality, decrease in volume, increase in angiotensis |
Increase/decrease of which factors will increase thirst? | Increase in osmolality, decrease in volume, increase in angiotensis |
What do you expect to see with Hypervolemic Hyponatremia in regards to plasma Na, water/Na, osmolality, Una and Uosm? | Plasma Na <136 mm/L : big increase in water, small increase in Na : decrease in plasma osmolality : Una <20 mm/L : Uosm high to isosmotic |
Name some examples of Hypervolemic Hyponatremia. | CHF, decompensated cirrhosis with ascites, advanced renal failure, nephrotic syndrome (least common) |
What changes to the Starling forces would cause edema? | increase cap. hydraulic pressure
: decrease cap. oncotic pressure
: increase cap. permeability
: Lymph obstruction |
Increase in capillary hydraulic pressure can be caused by what? | Increased blood volume or venous obstruction |
What is the common denominator seen in Hyper. hypo situations? | Decreased EABV |
What two physiologic responses will increase water retention? | Increased thirst and ADH |
what two physiologic responses will increase Na retention? | Increased SNS and RAAS |
Hypovolemic Hyponatremia indicates what? | There is a past or on going Na loss event |
What do you expect to see with Hypovolemic Hyponatremia in regards to plasma Na, water/Na, osmolality, Una and Uosm? | Plasma Na <136 mm/L
: decreased water with big decrease in Na
: decreased plasma osmolality
: Una depends
: Uosm ranging from low to high |
Name some examples of Hypovolemic Hyponatremia. | GI loss, bleeding, urine, skin (major sweating or burns) |
How do you distinguish between Extrarenal and renal hypo hypo? | Extrarenal the Una <20 mm/L
Renal the Una >20 mm/L |
Examples of Extrarenal causes of hypo hypo. | GI Loss, Excessive sweating, burns, third spacing of fluids |
Examples of Renal causes of hypo hypo. | Diuretics, salt-wasting neuropathy, mineralocorticoid deficiency, ketonuria, bicarburia |
What type of urine would you expect to see in a pt with a Renal cause of hypo hypo? | Isosmotic or concentrated urine (high Uosm) |
What is the "key" with Euvolemic Hyponatremia? | There is neither a volume or osmolar signal to increase ADH. |
What do you expect to see with Euvolemic Hyponatremia in regards to plasma Na, water/Na, osmolality, Una and Uosm? | Decreased plasma osmolality
: decreased Pna
: very high Una (>40 mm/L)
: Uosm is high |
What maybe the cause of the really high Una? | SIADH: either lots of ADH or increase renal responce to ADH |
What kind of conditions can cause SIADH? | Tumor, CNS disorder, thorasic dz, chest wall dz |
What conditions mimic SIADH | Hypothyroidism and adrenal glucocorticoid deficiency |
Name 3 examples of euvol. hypo with low Uosm. | Primary polydipsia, beer potomania, and tea and toast diet |
What can cause Hypernatremia? | Primary Na gain or a primary water deficit |
What would you expect to see in hypernatremia in respect to Pna and Posm? | Pna > 144 mm/L
: Posm would be high |
What is the normal response to hypernatremia? | Increase water intake and excrete a maximally concentrated, minimum volume urine |
What can cause Hypervolemic Hypernatremia? | Over zealous administration of hospital IV fluids |
What would you expect to see in regards to water, Na, plasma osmolality and Uosm? | Increase in water
: big increase in Na
: high plasma osmolality
: Uosm will depend on the competing signals for ADH |
What patient populations do you tend to see Euvolemic Hypernatremia in? | Elderly, those in nursing homes, people with no access to water, those with dibetes insipidus, and febrile patients |
What would you see in regards to water, Na, plasma osmolality, and Uosm? | Decrease in water
: no change in Na
: high plasma osmolality
: Uosm would be very low |
What is the hallmark seen in euvolemic hypernatremia? | A pure net loss of water with no change in Na |
What would you expect to see in hypovolemic hypernatremia in respect to water, Na, plasma osmolality and Uosm? | Big decrese in water
: decrease in Na
: increase in plasma osmolality
: Uosm would be high |
Name some Extrarenal causes of hypo hyper. | GI loss, excessive sweating and burns |
Nam some Renal causes of hypo hyper. | Loop diuretics and osmotic diuretics (not drugs: urea, glucose, mannitol, glycol) |