renal-exam 1-magnesium

  1. function of mg
    nature's psysiological calcium blocker, reguates k and ca channels, req for proper functioning of na-k-atpase pump, mg plays a role in the secretion of and bone sensitivity to PTH
  2. benefits of mg
    antidysrhythmic(DOC for torsades, dig induced tachyarr), seizure prevention and control in toxemia of pregnancy, tocolytic for preterm labor, may be benificial in lowering bp, may improve survival after MI, may improve cardiac fxn and survival in CHF pts
  3. Mg RDA-females
  4. Mg RDA males
    420 mg/d
  5. Mg distribution
    2nd most abundant INTRAcellular cation after potassium, no hormonal regulation of distribution, often hypo and hyper states found
  6. normal ECF range of Mg
    1.7-2.3 mg/dL
  7. Mg abs
    only 30-40% absorbed from ileum and jej, amt absorbed inverse with amt stored and ingested, dependent on vit D for absorption
  8. hypermagnesemia-decreased renal excretion
    GFR<30ml/min in renal insufficiency-renal impairment and elderly
  9. excessive intake-hypermagnesemia
    mg containing lax and antacids (MOM, Mg citrate), and tx of toxemia of pregnancy and use of ureteral irrigants
  10. neuromuscular signs and sx if Mg > 4mg/dl
    neuromuscular blockade, decreased DTRs about 7, somnolence, coma-9, respiratory depression...respiratory arrest >12
  11. cardiovascular signs and sx- Mg > 4mg/dl
    hypotension >3, bradycardia >4, complete heart block or asystole >14-15
  12. treatment of hypermg(req in all pts with Mg >8 mg/dl and in symptomatic pts with Mg >4 mg/dl
    reduce intake, enhance elim, and antago physiologic effects of Mg, 1. calcium gluconate (chloride) 1 gm IV, directly antag the neuromuscular and CV effects, effects are rapid but short lived, doses can be repeated hourly prn,2. IV saline at 100-150 ml/hr + furosemide 40-80 mg IV q 2-6 hr 3. dialysis if ESRD
  13. monitoring for tx of hypermg
    hourly Mg in pts with severe, symptomatic hypermg until no sx, Mg <4, then as needed; EKG, urine output, volume status
  14. Gi causes of hypomg
    decreased intake(malnut, alcoholism) decreased abs secondary to bowel disease (IBD, short bowel syn) increased losses (diarrhea/lax/vomiting, prolonged NG suction
  15. renal causes of hypomg
    renal tubular disorders(interfere with ability to reabsor Mg) hypercalcemia/hypercalciuria(ca and Mg compete for reabs in loop)
  16. drugs causing hypomg
    diuretics(esp loops), AGs, AMp B, laxative abuse, cisp, cyclos, tacro, dig, foscarnet, pentamidine
  17. factors that cause redistribution of Mg from ECF to ICF
    glucose, aa, insulin administration to pts with severe malnutritin, acute pancreatitis
  18. neuromuscular signs and sx generally not seen unless Mg less than or equal to 1 mg/dl
    neuromuscular hyperactivity: muscle twitching, muscle weakness, tremors, tetany, muscle weakness, paresthesias, chvostcks and trousseau's signs, seizures
  19. CV signs and sx generally not seen unless Mg <-1 mg/dl
    ECG changes: QT prolongation, QRS widening, torsades, V fib, coronary artery spasms
  20. concommitant disorders in potasssium and calcium homeostasis causing hypomg
    hypokalemia, hypocalc(via decreased release or sensitivty of bone to PTH)
  21. goals of tx for hypomg
    resolution of signs/sx, restore normal serum Mg level, correct concommitant elyte abnor, identify and correct underlying cause
  22. consideration in tx of hypomg
    Use LBW (or ABW if less than IBW) to calc replacement dose, reduce doses by 50% if CrCl <30 ml/min, replace mg deficit over 3-5 days
  23. IV considerations for treating hypomg
    available as Mg sulfate 50% solution (1gm/2mL) (1gm=8mEq), dilute to conc NMT 20% to minimize phlebitis, give slow IV (less than or equal to 8mEq/hr, 1 g/hr, to minimize ADRs)
  24. IM considerations for hypomg
    undiluted, very painful, reserved for severe hypomg and no IV access
  25. oral consideration for tx of hypomg
    diarrhea is self-limiting SE, oral converted to Mg-chloride in gut (req acid pH) preparations available as chloride salt may be better tolerated as less is needed, Mg Ox(oxide) 400 mg 1-2 QID, Slow-Mag(chloride) 64 mg 1-2 BID
  26. serum Mg <1.2 mg/dl WITH life-threatening sx (seizures, arrhy)
    Day 1: LD-2 gm Mg sulfate mixed with 6 ml NS (for a total of 10 cc) and give IV over 5 min Followed by: 1 mEq/kg IV inf over 24 hours

    Day 2-5: 0.5 meq/kg/day in main IV fluids

    Monitor: serum Mg hourly until stable q6-12, q24 h
  27. Mg <1.2 WITHOUT life-threatening sx
    Day 1:1mEq/Kg/24 hours in main IV or divide into 5 doses and give IM q 4 hours

    Days 2-5: 0.5 mEq/kg/day in IV main fluids or divide and give IM q 6-8 hours

    Monitoring: serum mg q 6-12 hours until stable then q 24 hours
  28. Mg 1.2 mg/dl-1.8 mg/dl OR chhronic replacement (alcoholics, bowel dx)
    • MOM 5 mL QID
    • Mg containing antacides 15 ml TID-QID
    • Mg oxide 400 mg 1-2 QID
    • Mg chloride 1-2 ts BID

    Monitor: serum Mg daily PRN
  29. tx of torsades
    1-2 gm (LD) over 5 min followed by 0.5-1 gm/hr
  30. tx of toxemia of pregnancy
    10-20 gm IV/24 hours
Card Set
renal-exam 1-magnesium
exam 1