Triage: sent in by PCP for low potassium 2.8. c/o arm and leg cramping and weakness and generalized weakness. hx of chronic constipation and chronic laxative use.

History: A patient in their mid-50’s with a history of constipation, GERD and depression is transported from home to the ER for generalized weakness and muscle cramps.  She denies any chest pain but does have mild SOB

Vital signs: T: 36.5 °C (Oral) HR: 58 (Peripheral) RR: 18 BP: 85/56 SpO2: 99%

Physical Exam: unremarkable

An ECG is done 

Computer Read: NSR at 71, possible RAE

What is the most likely cause of ECG findings in this patient?

  • A) Acute coronary occlusion
  • B) Blood clot (PE)
  • C) Cardiac tamponade
  • D) Drug toxicity
  • E) Electrolyte issue

Bonus Question: Your resident wants to order albuterol for her COPD.  Should you agree?

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ECG interpretation: There is subtle ST depression which could be from ischemia but the DDx includes hypokalemia.  The shape of the ST segment and T waves also suggests hypokalemia.  There also appears to be a subtle U wave in mutiple leads

QUIZ ANSWER:

  • A) Acute coronary occlusion – not common with flat T waves
  • B) Blood clot (PE) – not a good clinical fit
  • C) Cardiac tamponade – no tachycardia and voltage not low
  • D) Drug toxicity – good thought
  • E) Electrolyte issue – CORRECT

 

Case Outcome:

Potassium critically low at 2.4 and bicarb very high at 40. BUN 24, Cloridelow at 86.  Other labs in the metabolic panel and CBC essentially normal. Magnesium actually high at 3.3.

Urine sodium <20mEq/L, next day Mg and K both normal at 2.3 and 3.7

hypokalemia eventually determined to be due to her laxative abuse.

 

METABOLIC ALKALOSIS: bicarb = bicarbonate, comp = compensation, Cl = chloride

  • Formulae:     Bicarb:35 àpH:7.55 typically
  •                         Respiratory compensation: bicarb­10 àpCO2 ­7, max pCO2 55
  • Dangers:       Electrolyte: abberations in Ca++, K+, Mg++, Cl–
  •                         Cardiac: dysrhythmia if pH >7.6
  • Causes:         Mostly GI, renal, metabolic or endocrine.  See below
  • Urine Cl– <10:Diuretics, vomiting, NG suction, ­pCO2 >CF, ileostomy/diarrhea/laxative, Bartter, Gitelman
  •    Rx:               IV saline & correct electrolytes then PPI and possibly Diamox
  • Urine Cl– >10: ¯K+, ¯Mg++, ­Ca++, ¯albumin >>Cushing’s/Conn’s/steroid, Liddle, refeeding
  •    Rx:               Correct electrolytes then possibly Diamox, Aldactone or amiloride

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