Electrolyte and acid/base disorders Flashcards
Hormones affecting kidney
PTH: increased Ca2+ reabsorption, decrease reabsorption of phosphate, activate Via D
RAAS
Atrial natriuretic peptide: constrict efferent a, dilates afferent -> increased GFR -> diuresis
ADH: vasopressin - water reabsorption, urine concentration
SIADH
too much ADH
absorbing too much H2O -> low serum osmolarity, low serum Na+
excessive concentration of urine
High ADH from: small cell lung CA lung pathology head trauma, stroke, CNS infections drugs - cyclophophamide idiopathic
Central pontine myelinolysis
replace Na+ too quickly -> locked in sn
Excessive thirst + polyuria workup for DI
check glucose to r/o DM
check osmolality - low urine and high serum
water deprivation test - (normal -> concentrated urine) - urine osmolality stays low in DI
Central vs nephrogenic:
Desmopressin challenge (ADH analog)
-Central DI: increase urine concentration by 50%
-nephrogenic DI: no change or less than 50% if rises
Diabetic insipidus
too little ADH
increased urine volume
dilute urine
high serum osmolarity
low urine specific gravity
Central DI
abnl ADH production by hypothalamus
complete - no ADH
partial - insufficient ADH
Tx: intranasal desmopressin
Nephrogenic DI
kidney unresponsive to ADH
Lithium
Demeclocycline - tx SIADH
hypercalcemia
mutation of ADH receptor gene
Tx:
HCTZ - causes slight dehydration -> increased H2O absorption in proximal tubule -> more concentrated urine downstream
indomethacin - decreases RBF -> lower urine output
Amiloride for Lithium induced
Causes of K+ shifts out of cell -> hyperkalemia
low insulin b-blockers acidosis digoxin cell lysis - leukemia
Causes of K+ shift into cells -> hypokalemia
Ways to Correct hyperkalemia:
insulin: IV insulin + dextrose
b-agonist: albuterol
Alkalosis : IV bicarb
Cell creation/proliferation - cancer
Hyponatremia sx
confusion altered mental status - esp elderly seizures stupor coma
Hypercalcemia sx
“stone, bones, abdominal growns and psychiatric overtones”
confusion, delirium
hypocalcemia sx
tetany
+ Troussea/Chvostek signs
Hypomagnesemia sx
tetany
EKG abnl - arrhythmias -> prolonged QT
-VT, torsades
Hypermagnesemia sx
low reflexes
serial neuro exams
hypokalemia sx
prolonged QT -> VT, torsades
flat T wave, U wave
