Electrolytes (Na) Flashcards
Electrolyte concentrations in body fluids
-sodium outside (ECF)
-potassium inside (ICF)
Goals of electrolyte therapy
-prevent/treat serious complications
-normalize serum concentration
-identify and correct underlying causes
-avoid overcorrection
Sodium 135-145 mEq/L
-primary extracellular cation
-needed to maintain cellular integrity
-maintains osmolar gradient = regulate fluid homeostasis
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
Classification of HYPOnatremia
-Na+ < 135 mEq/L
-what’s tonicity?
-what’s volume status
Osmolality
-275-290 mOsm/L
-number of particles per liter of water
-measure or estimate
Serum Osmolality calculation
Osm = (2*Na) + (BUN/2.8) + (Glucose/18)
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
Hypertonic Hyponatremia
-often seen with elevated Blood glucose (>120-140)
->290mOsm
Corrected Serum Sodium
-serum sodium falls by 1.6 mEq/L per 100mg/dL increase in BG over 100mg/dL
Corrected Serum sodium equation
Serum Na + 1.6((BG-100)/100))
Hypotonic Hyponatremia classification
-must check volume status to classify
->90% of all hyponatremia
HYPOvolemic Hypotonic hyponatremia
-TBW and Na+ dec
-RENAL causes (urine Na+ > 20mEq/L)
-NON-Renal causes (urine <20 mEq/L)
Renal Causes of HYPOvolemic hypotonic hyponatremia
-lots of Na+ in urine (>20mEq/L)
-diuretics
-adrenal insufficiency (mineralcorticoid deficiency)
-salt losing nephropathy
-cerebral salt wasting
Non-renal Causes of HYPOcvolemic hypotonic hyponatremia
-blood loss/ hemorrhage
-skin losses (burn/sweat/wound)
-GI losses (vomit, diarrhea, suction)
Isovolemic hypotonic hyponatremia
-TBW inc
-Na+ normal or slight inc
-slight excess of ECF
-no peripheral or pulmonary edema
-appears euvolemic
Isovolemic Hypotonic hyponatremia causes
-adrenal insufficiency (glucocorticoid defic)
-HYPOthyroidism
-psychogenic polydipsia
-SIADH
Syndrome of Inappropriate AntiDiuretic Hormone release (SIADH)
-most common cause of isotonic hypo hyponatremia
-water intake exceeds kidney ability to excrete water
causes of SIADH
-tumors
-CNS disorders
-DRUGS
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
Treatment of SIADH
-remove underlying cause
1. free water restrivtion
2. Vaptans if 24-48 hours of free water restriction fails (conivaptan and tolvaptan)
Hypervolemic Hypotonic hyponatremia
-TBW and Na+ inc
-expanded ECF volume and edema
Hypervolemic Hypotonic Hyponatremia seen in
-Cirrhosis
-Heart failure
-Kidney Failure (acute/chronic)
-nephrotic syndromes
Clinical presentation of hypotonic hyponatremia
-mostly asymptomatic (Na+> 125 mEq/L
-HYPO = dehydration
-Hyper = Edema
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
