DISORDERS OF POTASSIUM HOMEOSTASIS

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DISORDERS OF POTASSIUM HOMEOSTASIS

• Informal Academic in Service

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Overview

• Hypokalemia
• Hyperkalemia
• Case Discussion

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HYPOKALEMIA Serum potassium lt 3.5 mEq/L
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Pathophysiology

• Total body potassium deficit
• Shifting of serum potassium into the
  intracellular compartment
• Causes
• Drugs (loop and thiazide diuretics)
• Diarrhea
• Vomiting
• Hypomagnesemia

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Principal cell
Lumen
Blood
Na
Na
-

K
K
Aldosterone ??????????????????????? K ???
Hypo Mg
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Loop VS Thiazide
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Principal cell
Thaizide

Blood
Lumen

Na
-
Na

-
K

-
K

????????????????????? 9 ??????? HCTZ

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Principal cell
Loop

Lumen
Blood

Na
-
Na

-
K
-

K
Ca2

Ca2
?????????????????? ??? 3 ??????? furosemide
Ca2

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• ??????? HCTZ ??? lost K ??????? Furosemide

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Clinical Presentation

• Nonspecific signs and symptoms
• Cardiovascular
• Hypertension
• Cardiac arrhythmias heart block, atrial flutter,
  paroxysmal atrial tachycardia, ventricular
  fibrillation, and digitalis-induced arrhythmias
• ECG effects (serum K lt2.5 mEq/L) ST-segment
  depression or flattening, T-wave inversion and
  U-wave elevation
• Neuromuscular symptoms
• Muscle weakness, cramping, malaise and myalgias

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Treatment

• Every 1 mEq/L fall of K below 3.5 mEq/L ? Total
  body deficit of 100-400 mEq
• Chronic used of loop or thiazide diuretics
  generally need 40-100 mEq of K
• K supplementation
• Oral KCl
• IV
• severe hypokalemia
• signs and symptoms of hypokalemia
• Inability to tolerate oral therapy

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Treatment

• K administration
• Dilute in saline because dextrose can stimulate
  insulin secretion and worsen intracellular
  shifting of K
• 10-20 mEq of K in 100 ml of NSS through a
  peripheral vein over 1 hr
• ECG monitoring (If infusion rates gt 10 mEq/hr)

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HYPERKALEMIA Serum potassium gt 5.5 mEq/L
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Pathophysiology

• Kintake gt Kexcretion
• Transcellular distribution of K is disturbed
• Causes
• Increased K intake
• Decreased K excretion
• Tubular unresponsiveness to aldosterone
• Redistribution of K to the extracellular space
• Drugs ACEI, ARB, K-sparing diuretics

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Clinical Presentation

• Frequently asymptomatic
• Heart palpitations or skipped heartbeats
• ECG change (serum K 5.5-6 mEq/L)
• Peaked T waves
• Widening of the PR interval
• Loss of the P wave
• Widening of the QRS complex
• Merging of the QRS complex with the T wave
  resulting in a sine-wave pattern

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Treatment

• Dialysis
• Calcium administration
• Insulin and dextrose, sodium bicarbonate, or
  albuterol
• Sodium polystyrene sulfonate/Calcium polystyrene
  sulfonate

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Treatment algorithm for hyperkalemia
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Treatment

• Dialysis
• Most rapid lowering serum K
• Calcium
• Rapidly reverses ECG arrhythmias
• Not lower serum K
• Short acting
• Must be repeated if signs or symptoms recur
• Insulin dextrose/sodium bicarbonate/albuterol
• Rapid shift potassium intracellularly

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Treatment

• Sodium polystyrene sulfonate (kayexalate)
• Mild to moderate hyperkalemia (K 5-7 mEq/L)
• Each gram of resin exchanges 1 mEq of Na for 1
  mEq of K
• Sorbitol promotes excretion of K (by diarrhea)
• Tolerated effective oral gt rectal
• Calcium polystyrene sulfonate
• Same kayexalate used
• For patient who restriction of Na

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Therapeutic Alternatives for the Management of
Hyperkalemia
Medication Dose Route of Administration Onset/Duration of Action
Calcium 1 g (1 ampule) IV over 510 min 12 min/1030 min
Furosemide 2040 mg IV 515 min/46 hr
Regular insulin 510 units IV or SC 30 min/26 hr
Dextrose 10 1,000 mL (100 g) IV over 12 hr 30 min/26 hr
Dextrose 50 50 mL (25 g) IV over 5 min 30 min/26 hr
Sodium bicarbonate 50100 mEq IV over 25 min 30 min/26 hr
Albuterol 1020 mg Nebulized over 10 min 30 min/12 hr
Hemodialysis 4 hours N/A Immediate/variable
Sodium polystyrene sulfonate 1560 g Oral or rectal 1 hour/variable
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Case DiscussionWarfarin clinic
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Case 1

• ????????????????? 57 ??
• Supraventricular tachycardia, DM, HT
• ???????? Warfarin dose 15 mg/wk
• ????????? enalapril ??? 5 mg/day ???? 10 mg/day
• ??????????????? spironolactone ??? consult
  ??????????
• ????????????? (spironolactone) ???????????????????
  
• Advice sign of bleed/embolism
• ???????? 12/01/54

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LAB

• INR 2.1 PT 22.7
• Hb 12.3 Hct 35.1 WBC 5360 Plate 229000
• Na 137 K 5.0 Cl 103 CO2 28
• BUN 22 Cr 1.9 FBS 124

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Subjective data

• ????????????????? 57 ??
• Hx Supraventricular tachycardia, DM, HT
• Warfarin dose 15 mg/wk (dose ????)
• ?????????????? enalapril ??? 5 mg/day ???? 10
  mg/day
• ??????????????? spironolactone ????????????? off
  ????????????? ?????????????????????????

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Objective data

• INR 2.1 PT 22.7
• K 5.0
• BUN 22 Cr 1.9
• FBS 124
• ???????? 12/01/54

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Assessment

• Spironolactone
• Dose 25-50 mg/day in 1-2 divide dose
• Contraindication hyperkalemia, acute renal
  insufficiency
• ADR gynecomastia, hyperkalemia, metabolic
  acidosis

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Assessment

• Enalapril
• Dose 2.5-5.0 mg/day then increase as require at
  1-2 wk (Max 40 mg/day)
• Contraindication angioedema
• ADR hyperkalemia (1 to 3.8 )

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Assessment

• K 5.0 ? High potassium
• Cr 1.9 mg/dl ? ClCr 36 ml/min
• Spironolactone ????????????????? ClCr lt 10 ml/min
• ??????? ??????????????????????? spironolactone
• Management
• ??????????? enalapril ??????? spironolactone
  ????????
• ????????? serum K, renal function ??? ECG change

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Plan

• Goal
• Electrolyte balance
• Therapeutic plan
• RM
• Enalapril 5 mg 1x2 pc
• Spironolactone 25 mg 1x1 pc

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Plan

• Efficacy monitoring
• K 3.5-5.0 mEq/L
• BUN, Scr
• Toxicity monitoring
• Hyperkalemia
• Renal insufficiency

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Plan

• Education plan
• ???????????????????? ?????? ???
  ???????????????????
• ????????????????????
• Future plan
• ??????????????????????????
• ?????????????????????????????????

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Case 2

• ?????????????? ???? 47 ??
• ???????????????????????????
• INR 2.37
• K 3.4 ????????? KCl elixir 10 ??????? 15 ml PO
  stat

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????????? KCl elixir 10 15 ml??????
???????????????
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Potassium Chloride

• KCl 1 g ??? Approximate K 13 mEq
• 10 KCl elixir ?? KCl 10 g/100 ml
• ?????????? 10 KCl elixir 15 ml KCl 1.5 g
• ??????? ?????????? K 19.5 mEq

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Total K replecement

• K 40 mEq oral ????? K ??????? 1 mEq/L
• K 19.5 mEq oral ????? K ??????? 0.5 mEq/L
• ??????? ?????? ??????? serum K 3.40.5 3.9
  mEq/L

KNormal range 3.5-5.0 mEq/L
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References

• Charles F Lacy, et al. Drug Information Handbook
  2008-2009. 17th edition 2008.
• Barbara G Wells, et al. Pharmacotherapy Handbook.
  7th edition 2009.
• ??????????????????????????????????????????????????
  ????????????????? ????????????????,
  ???????????????????????????????
  ????????????????????????????????.
  ???????????????????????????????? ?.?. ???? 2552.
• Mancia G, et al. 2007 ESH-ESC Practice Guidelines
  for the Management of Arterial Hypertension.
  Journal of Hypertension 25 (9), 2007.
• http//www.thomsonhc.com

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