Electrolytes (Na) Flashcards by Brooke Thornburg

Electrolyte concentrations in body fluids

-sodium outside (ECF)
-potassium inside (ICF)

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Goals of electrolyte therapy

-prevent/treat serious complications
-normalize serum concentration
-identify and correct underlying causes
-avoid overcorrection

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Sodium 135-145 mEq/L

-primary extracellular cation
-needed to maintain cellular integrity
-maintains osmolar gradient = regulate fluid homeostasis

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HYPOnatremia

-most common electrolyte disturbance in hospital
-brain injury (seizure/death)
-too rapid correction of sodium (demyelination)
-acute effects of HYPO-osmolality
-big time morbidity and mortality

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Classification of HYPOnatremia

-Na+ < 135 mEq/L
-what’s tonicity?
-what’s volume status

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Osmolality

-275-290 mOsm/L
-number of particles per liter of water
-measure or estimate

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Serum Osmolality calculation

Osm = (2*Na) + (BUN/2.8) + (Glucose/18)

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ISOtonic hyponatremia (pseudohyponatremia)

-extreme elevations of lipid and proteins increase total plasma volume
-seen with hypertriglyceridemia or hyperproteinemia
-leads to dilution effect
-sodium appears low (just displaced)
-measured Osm not really affected
-Calculated Osm is low due to low sodium
=osmolality gap

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Hypertonic Hyponatremia

-often seen with elevated Blood glucose (>120-140)
->290mOsm

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Corrected Serum Sodium

-serum sodium falls by 1.6 mEq/L per 100mg/dL increase in BG over 100mg/dL

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Corrected Serum sodium equation

Serum Na + 1.6((BG-100)/100))

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Hypotonic Hyponatremia classification

-must check volume status to classify
->90% of all hyponatremia

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HYPOvolemic Hypotonic hyponatremia

-TBW and Na+ dec
-RENAL causes (urine Na+ > 20mEq/L)
-NON-Renal causes (urine <20 mEq/L)

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Renal Causes of HYPOvolemic hypotonic hyponatremia

-lots of Na+ in urine (>20mEq/L)
-diuretics
-adrenal insufficiency (mineralcorticoid deficiency)
-salt losing nephropathy
-cerebral salt wasting

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Non-renal Causes of HYPOcvolemic hypotonic hyponatremia

-blood loss/ hemorrhage
-skin losses (burn/sweat/wound)
-GI losses (vomit, diarrhea, suction)

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Isovolemic hypotonic hyponatremia

-TBW inc
-Na+ normal or slight inc
-slight excess of ECF
-no peripheral or pulmonary edema
-appears euvolemic

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Isovolemic Hypotonic hyponatremia causes

-adrenal insufficiency (glucocorticoid defic)
-HYPOthyroidism
-psychogenic polydipsia
-SIADH

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Syndrome of Inappropriate AntiDiuretic Hormone release (SIADH)

-most common cause of isotonic hypo hyponatremia
-water intake exceeds kidney ability to excrete water

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causes of SIADH

-tumors
-CNS disorders
-DRUGS

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Possible Drug-Induced SIADH

-antineoplastics (cyclophosphamide and vincristine)
-antipsyc**
-bromocriptine
-carbamazepine*
-chlorpropamide
-desmopressin
-meperidine/morphine
-nictoine
-NSAIDs (ibuprofen)
-oxytocin
-fluoxetine/sertraline**
-TCAs (amitryptyline)
-Imipramine
-Tolbutamide

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Treatment of SIADH

-remove underlying cause
1. free water restrivtion
2. Vaptans if 24-48 hours of free water restriction fails (conivaptan and tolvaptan)

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Hypervolemic Hypotonic hyponatremia

-TBW and Na+ inc
-expanded ECF volume and edema

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Hypervolemic Hypotonic Hyponatremia seen in

-Cirrhosis
-Heart failure
-Kidney Failure (acute/chronic)
-nephrotic syndromes

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Clinical presentation of hypotonic hyponatremia

-mostly asymptomatic (Na+> 125 mEq/L
-HYPO = dehydration
-Hyper = Edema

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Hypovolemic hypotonic hyponatremia presentation

-dehydration -dec skin turgor -orthostatic HTN -tachycardia -dry membranes

Presentation of isovolemic hypotonic hyponatremia

-malaise -psychosis -seizures -coma

Presentation of hypervolemic hypotonic hyponatremia

-edema -weight gain

presentation of acute hyponatremia

-over 12 hours or less -nausea -malaise -weakness -headache -disoriented -coma -seizure -respiratory arrest

Goals of HYPOvolemic tx

-restore volume deficit

Isovolemic or Hypervolemic tx goals

-underlying cause? -symptoms?

IMPORTANT note about treatment

-in most cases, do not correct sodium higher than 0.5 mEq/L/hr or no more than NMT 8-12 mEq/L/day

Hypovolemix tx options

-symptomatic: 3% NaCl (HYPERtonic) -asymptomatic: 0.9% NaCl (isotonic)

Isovolemic tx

-symptomatic: furosemide + 3% NaCl -asymptomatic: 0.9% NaCl and water restriction

Hypervolemic tx

-symptomatic: furosemide and JUDICIOUS 3% NaCl -asymp: furosemide

Acute Hyponatremia

-less than 48 hours -brain cells swell w water -cerebral edema -severe neurologic sx -brain herniation -death

Chronic Hyponatremia

-more than 48 hours -brain cells extrude solutes -minimal brain swelling -mild neurologic sx -brain herniation is rare -death rare

Acute Symptomatic Hyponatremia

-severe: mental status and seizures -metabolic encephalopathy can develop: (edema, inc pressure, herniation, fatal sometimes) -tx immediately

Treatment of Acute Symptomatic Hyponatremia

-inc serum Na+ by 1-2 mEq/L/hr until symptoms resolve -HYPERtonic saline (3% NaCl) -replace half of sodium deficit in 8 hours then remaining deficit (half the rate) within 8-16 hours (rules of 8s) -goal: 120mEq/L*** -complete correction unnecessary -inc of 4-6 mEq/L is usually good -MAX 8-12 mEq/L in first 24 hours

Too rapid correction of acute symptomatic hyponatremia

-diffuse demyelinating lesions -central pontine myelinolysis

Risk v benefit

-risk of cerebral edema from hyponatremia better than risk of demyelination from overcorrecting

Demyelination Risk Factors

-serum Na < 105 mEq/L -Hypokalemia -alchoholism -malnutrition -liver disease -hypoxemia -cancer -burns -diabetes -renal failure -sodium inc too fast

Acute Symptomatic Hyponatremia Monitoring

-in ICU or equiv -exam heart, lungs, neurological status several times over first 12 hours -serum Na+ q2-4h until asymptomatic then q6-8h until WNL

Pharmacist's role on serum Na+

-manage acid base/electrolyte status and IVF

HYPERnatremia

-always HYPERtonic -impaired thirst response in infants, elderly, disabled -result of loss of water or ingestion of sodium/hypertonic fluids -must assess volume status

Classification of HYPERnatremia

-Hypovolemic -Isovolemic -Hypervolemic

HYPOvolemic HYPERnatremia tx goals

-restore hemodynamic status first if needed (0.9%NaCl) -once IV volume restored: -calc free water deficit

Free Water Deficit

NL TBW * ((serumNa/140)-1)

Replacing Free Water Deficit

-provide free water -match I/O if possible -don't correct too quickly -adjust as needed -goal: 0.5 mEq/L/hr decrease in serum Na

Providing free water

-D5W continuous infusion -enteral free water via feeding tube

Don't correct free water too quickly (HYPOvolemic HYPERnatremia)

-give 1/2 total deficit over 24 hours -give remaining over next 24-48 hours -adjust as needed

Monitoring Parameters for HYPOvolemic Hypernatremia

-check serum Na and fluids q 3-6h for first 24 hours -then q6-12h after sx resolve and Na <145 -I/O q 8-12h -overall fluid balance q24h

look at calculations

weights too

Isovolemic Hypernatremia (diabetes)

-Central: (brain injury, CNS, meningitis) -Nephrogenic (drugs, radiocontrast dies, ATN, inherited)

Isovolemic Hypernatremia treatment

-Desmopressin (DDAVP) -Vasopressin

Desmopressin (DDVAP)

-treat ISOvolemic HYPERnatremia -acute: admin subq or IV 0.25-0.5mL BID -chronic: intranasal 0.05-0.2mL BID

Vasopressin

-tx acute ISOvolemic Hypernatremia -continuous infusion titrated hourly to goal UOP

HYPERvolemic hypernatremia causes

-uncommon from hypertonic fluids -hypertonic saline resuscitation -excess NaHCO3 admin -too much dietary salt

Hypervolemic Hypernatremia treatment

-stop hypertonic fluids/cause -rapidly excreted -diuretic if needed -match I/O

Change in serum Na equation

(fluid Na - serum Na)/(TBW + 1L) -estimates change in serum sodium per one liter of any given fluid -can calculate for inc or dec in sodium -determine change prn for goal time period

HYPOvolemic HYPERnatremia

-loss of water -TBW and Na LOW -renal, Gi, adrenal, lung, skin

ISOvolemic HYPERnatremia

-TBW low -Na fine -diabetes, skin loss, latrogenic, osmotic diuresis, polydipsia

HYPERvolemic HYPERnatremia

-TBW and Na HIGH -mineralcorticoid excess