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Renal 04 Na/H2O bal

Thomas: Disorders of Na and water balance

What controls total body water and Na? TBW - ADH : Na - Aldosterone
What lab values do you need when assessing a pt for Na disorders? Serum chemistry, Uosm, Sosm, Una, Ucr
What Na level defines hyponatremia? Na <135
What is one area of concern with hyponatremia? The potential of edema in the skull, as there is limited room for expansion.
Name symptoms associated with acute hyponatremia. Nausea, vomiting, lethargy, confusion, seizures, coma
Why is it that typically, only people with acute hypo/hypernatremia have neurological symptoms? The brain doesn't have a chance to shoot out ions to pull water out.
What does an acute increase in ADH do to ECF? It causes an acute decrease in ECF osmolality leading to the movement of water into the brain cells
Why isn't the increase in brain water as high as expected? There is a prompt loss of electrolytes and organic osmolytes.
What is pseudohyponatremia? Where calculated Na on lab work is low when Sosm is hypertonic (>280) due to other effective osmoles
Name some of the osmoles/ conditions leading to pseudohypo. Mannitol, post transurethral resection of the prostate, and hyperglycemia
How does hyperglycemia cause pseudohypo? If blood glucose is >400, the higher Sosm will pull water out of the cells with no increase in Sna.
For every 100 mg/dL in glucose above 100, how much with the serum Na appear to decrease? 1.6 meq lower that the actual value.
What is the formula for corrected Na? =1.6[(Pt glucose-100)/100]+pt Na
What is the normal response to hypovolemia? Increase ADH release and increase thirst
What does the proportion of water to Na uptake look like? Water reuptake > Na reuptake
Why do we use the Fractional Excretion of Sodium (FeNa)? To determine the amount of Na lost in the urine and determine the likely source.
What is the formula? FeNa(%)= (Una*Pcr)/(Ucr*Pna) *100
What are the two subtypes of hypo hypo? Extrarenal and Renal
List some Extrarenal causes of hypo hypo. GI losses (vomiting, diarrhea, NG suction, high output ostomy) : Skin (burns)
What lab values would you expect to see with extrarenal hypo hypo? Una <=20, FeNa <=1%, FeUr <=35%
List some Renal causes of hypo hypo. Diuretics, salt-wasting nephropathy, Mineralocorticoid deficiency.
What lab values would you expect to see with renal hypo hypo? Una >=20, FeNa >=2%, FeUr >=50%
What's the mechanism of hyponatremia in mineralocorticoid deficiency? Decreased volume -> insufficient Aldosterone release -> Insufficient Na and water reuptake -> insufficient volume expansion
How and where does aldosterone work? Increases reabsorption of Na and water while increasing the secretion of K in the DCT and CD
What is the Tx for hypo hypo? Volume resusciation and treat offending cause if possible.
How do you calculate a pts Na deficit? Na deficit = TBW (kg)*(desired Na-pt Na) : TBW = 0.6 male or 0.5 female/elderly
What is the maximum amount you correct a pts Na in a 24 hour period? No more than 10 meq/L
What occurs in Central Pontine Myelinlysis? Relative glial dehydration and myelin degradation and/or oligodendroglial apoptosis
What clinical syndrome can result from CPM? "Locked in" syndrome, quadriparesis and/or speech disturbances
True/False: for every 100mg/dL in glucose above 100, serum Na will appear 1.6 meq higher than the actual value. False, it will appear 1.6 meq LOWER.
What body response is seen with Hypervolemic hyponatremia? ADH release to increase thirst as well as activating RAAS, but ADH effect >> aldosterone effect
Una <20, FeNa <1% : water reuptake >>Na reuptake
What diseases is this seen associated with? CHF, Liver failure, nephrotic syndrome
What is the Tx for hyper hypo? Fluid restriction, Na restriction, loop diuretics : body wants to increase water and Na, we want to decrease water and Na
a 66 y/o male presents with CHF. What ADH action will help to increase blood volume and maintain blood pressure? Increase in ADH
How is the excess ADH affecting the water in his ECF compartment and ICF compartment? Increase wating in ECF and it shifts from ECF to ICF
Would you expect this patient to be symptomatic from his hyponatremia? No
In this pt, how fast will the hyponatremia develop? Over weeks to months
True/False: Pts with hypervolemic hyponatremia are volume overloaded in both intravascular and extravascular spaces. False
How is the diagnosis of euvolemic hyponatremia made? It's a Dx of exclusion
What will the pts Uosm look like? It depends on the cause of the euvolemic hypo.
Name some situations where euvolemic hypo presents with a Uosm <100 Primary polydipsia, beer potomania, tea and toast diet.
Name some situations where euvolemic hypo presents with a Uosm >100 SIADH, hypothyroidism, glucocorticoid deficiency
Under what conditions can primary polydipsia be seen? Psychiatric disorder, pts drink massive amount of fluid (>12L/day), max urine is about 12L/day, so excess water is retained.
Describe what's going on with beer potomania / tea toast diet. Relatively large volume ingested in face of low solute load.
What is the underlying mechanism in euvolemic hyponatremic disorders with Usom >100? ADH
What happens with hypothyroidism Decreased CO= decreased BP = increased ADH : If suspected, check TSH
What about in glucocorticoid deficiency? CRH crossreacts and activated ADH. : Associated NV = decreased BP = increased ADH : If suspected, check random cortisol
And in SIADH? Uosm > Sosm
What can cause SIADH? Head injuries, post surgery, small cell lung cancers
Define hypernatremia. Serum Na >145
What kind of patients do you see hypernatremia in? Pts that lack access to water or whose water losses exceed the ability of pt to keep up
What are the 4 categories of hypernatrmia? GI losses, renal losses, central causes, lack of access to water
What happens with GI Losses? Water loss exceeds electrolyte loss (diarrhea, malabsorption)
What situations are seen with Renal Losses? Nephrogenic Diabetes Insipidus (ADH ineffective at V2 receptors), Osmotic diuretics (hyperglycemia)
What situations are seen with Central causes? Central Diabetes insipidus, Tumor invasion of thirst center, stroke in thirst center
What situations are seen with lack of access to water? Elderly in NH, demented, physically impaired, intubated pts, excessive exercise, burns (depending on mechanism)
What is the Tx for hypernatremia? address underlying causees (desmo for CDI, Thiazides for NDI, stop iatrogenic causes) : calculate free water deficit and replace as appropriate
How do you calculate the free water deficit? Free water= TBW(kg)*[(pt Na/desired Na)-1] :TBW = 0.6 males and 0.5 females/elderly
What is the max you can correct in a day? Do not correct Na more than 10-12 meq in 24 hours
True/False: Hypernatremia is always corrected by calculating the free water deficit and replacing it. False. You need to first address the underlying cause.
True/False: Central diabetes insipidus is treated with Loop Diuretics. False. Treated with desmopressin
Created by: bcriss