Zhao Mingyao: Bmc.zzu. 2006-2-12

Zhao Mingyao BMC.ZZU. 2006-2-12

Disorder of potassium metabolism serum [K+] mmol/L 3.5 ~ 5.5 Normal level < 3.5 hypokalemia > 5.5 hyperkalemia

Function of K+ enzyme activity cellular electricity cellular osmolality acid-base balance

H+

K+ Na+

Part 1 General introduction 1. Potassium content and distribution

Potassium content and distribution 50~55mmol/Kg×BW ECF

ICF

K+

K+

K 3.5~ 5.5 mmol/L +

1.4%

K+ 140~160mmol/L

Direction of K+ shifting

90%

2.Maintenance of potassium balance

Maintenance of potassium balance intake

50~55mmol/Kg×BW ICF

K+ ECF 3.5~ 5.5 mmol/L

K+

140~160mmol/L

kidney 90%

GI tract

Direction of K+ shifting

Skin?

(1) The control of K+ transfer between intra- & extracellular compartments

K+ shifts between ICF and ECF Insulin, β-adrenergic agonist, ADS, K+, exercise, pH, osmolanity ECF

ICF

K+

K+

3.5~ 5.5 mmol/L

140~160 mmol/L

(2) Regulation of renal K+ excretion

Regulation of renal K+ excretion

K+ Na+

-- -

tubular cell

ICF

K+

Na+-K+ ATPase

kidney 90%

ADS, guanylin, [K+]s, urinary flow rate, pH, distal delivery of sodium, impermeable anion

Part 2 Hypokalemia • Defined as [k+]s < 3.5 mmol/L

1.Causes (1)K+ Intake↓: (2)K+ redistribution: pH↑, some drugs, barium and crude cottonseed poison, familial hypokalemic periodic paralysis, (3)K+ loss: • In general infant － gastrointestinal tract adult － kidney: diuretics, renal tubular acidosis, ADS ↑, Mg2+ ↓

2.Effect on body (1)neuromuscular irritability ↓ hyperpolarization impeding

(2) Effect on heart Excitability ↑ ---- Et-Em Conductivity ↓ ---- Em, phase 0, rapid Na+ inward flow ↓

Automaticity ↑ ---- slow K+ outward flow ↓ Contractility ↑ ---- Ca2+ inward flow ↑

typical feature of ECG during hypokalemia < 2.5 mmol/L + U wave(ECG) aura sign of cardiac asystole

•

Representative ECG tracings showing evolution of U-wave amplitude before intiation of TdP in drug-induced arrhythmia in rabbit. (A) Baseline before infusion of drug. (B) ECG tracing 12 minutes after drug infusion shows emergence of a U wave (marked by arrowhead in this and subsequent panels). C and D show progressive increase in U wave amplitude 2 min (C) and 10s (D) before TdP initiation. (E) U-wave amplification increases further and is associated with premature beats and TdP. Scale bar is 10 mV (vertical) and 200 ms (horizontal) throughout.

(3) Misccllaneous effect • Metabolic alkalosis • Paradoxical acidic urine • Rhabdomyolysis

3. Principle of prevention & treatment oral slow low concentration limited total amount/d urine existence

Part 3

Hyperkalemia

• Defined as [k+]s >5.5 mmol/L

1.Causes (1)K+ Intake ↑ : (2)K+ shift into ECF ↑ : pH ↓, some drugs (β-R antagonist), cell injury, familial hyperkalemic periodic paralysis

(3)Renal K+ excretion ↓: GFR ↓ ↓, ADS ↓(Addison`s disease), diuretics with blocking ADS

2. Effect on body (1)Neuromuscular irritability ↑, then↓ partial depolarization? Excitation ↑ depolarization impeding

(2) Effect on heart Excitability ↑, then↓ ---- Et-Em ↓, closing Conductivity ↓ ---- Em, phase 0, rapid Na+ inward flow ↓

Automaticity ↓ ---- outward flow slow K ↑ Contractility ↓ ---- Ca inward flow ↓ +

2+

typical feature of ECG during hyperkalemia > 7.5mmol/L + tent-like T wave aura sign of cardiac asystole

•

Figure 2 - ECG tracing showing other ECG changes to include: absent "P wave", tall tented "T" wave, and widening of QRS complex. K+ level was 7.8 mmol/L.

（ 3 ） Effect on acid and base • Metabolic acidosis • Paradoxical alkaline urine

3. Principle of prevention and treatment ①Limit origination: intake ↓ ② Sodium and calcium salt opposite the toxicity of hyperkalemia

③ Shifted into cell (transient, such as GI fluid, pH ↑) ④ Remove K+ out of body Na+-K+ cation exchange resin enema hemodialysis

Question 1. Is this is certainly hyperkalemia if serum K+ > 5.5mmol/L Pseudohyperkalemia: blood sample hemolysis ; plt >1012 /L; WBC >2×1011/L

Is it certainly hypokalemia facing familial periodic paralysis?

Question 2.

Wrong , divided to hypokalemia and hyperkalemia

Question 3.

Disease Case

A infant with serious diarrhea and vomiting, a large amount of NGS solution administered , intestine peristalsis ↓ ， gastricoenterouse flatulence, tympanic resonance. Diagnosis: ？ paralyzed ileus How did it occur?

2006-02-11