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Renal 02 Elec. Dis.
Hamra: Electrolyte Disorders
| 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) |
Created by:
bcriss
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