塩化カリウム / グルコン酸カリウム
カリウムは生命維持に不可欠な重要な細胞内電解質です。特に心臓、骨格筋、平滑筋などの興奮性組織において、細胞の静止膜電位を維持する上で極めて重要な役割を果たします。 **臨床のポイント：** * **低カリウム血症**は、慢性腎臓病（特に猫）、積極的な利尿、糖尿病性ケトアシドーシス（DKA）、および重度の消化管からの喪失によく見られる合併症です。 * **グルコン酸カリウム**は、消化管への刺激が少なく、軽度のアルカリ化作用があるため、通常、経口補給に推奨されます。 * **塩化カリウム（KCl）**は静脈内補給の標準ですが、致命的な不整脈を防ぐために投与前に**必ず**希釈する必要があります。 * 酸塩基平衡異常（アシドーシスはカリウムを細胞外に移動させる）が存在する場合、血清レベルが正常に見えても、全身のカリウム枯渇が重度である可能性があります。
作用機序: Potassium is the principal intracellular cation in the body. It works primarily via the **Na+/K+ ATPase pump** to maintain the electrochemical gradient across cell membranes. * Maintains cellular tonicity and resting membrane potential → essential for nerve impulse transmission. * Regulates smooth, skeletal, and cardiac muscle contraction. * Acts as a crucial cofactor in carbohydrate utilization and protein synthesis. * Essential for the maintenance of normal renal function.
動物種別の用量
- Treatment of chronic mild hypokalemia (3.0-3.5 mEq/L) · 0.5-1 mEq/kg mixed in food once or twice daily · PO · q12-24h
- Treatment of chronic mild hypokalemia (Tumil-K powder) · 1/4 teaspoonful (2 mEq) per 4.5 kg body weight in food twice daily; adjust as necessary · PO · q12h
- Moderate to severe (<3.0 mEq/L) or acute hypokalemia · Rate should not exceed 0.5 mEq/kg/hour. Under dire circumstances (serum K < 2.0 mEq/L), rate can be increased to 1.5 mEq/kg/hour along with close EKG monitoring. · IV · Continuous
- Subcutaneous fluid supplementation (<10 kg patients) · 150 mL SC every 12 hours of isotonic fluids containing 30-35 mEq/L KCl · SC · q12h
- Oral maintenance supplementation · 2-4 mEq/day · PO · Daily · Using potassium gluconate.
- Sliding scale IV supplementation based on Serum K+ · Serum K+ <2 mEq/L = 60 mEq/1000 mL IV fluid; Serum K+ 2-2.5 mEq/L = 40 mEq/1000 mL IV fluid; Serum K+ 2.5-3 mEq/L = 30 mEq/1000 mL IV fluid; Serum K+ 3-3.5 mEq/L = 20 mEq/1000 mL IV fluid. Infusion rates should generally not exceed 0.5 mEq/kg/hour. · IV · Continuous
- Hypokalemia in 'downer' cows · 80 grams sodium chloride and 20 grams potassium chloride in 10 liters of water via stomach tube. Provide a bucket containing similar solution for cow to drink and another containing fresh water. · PO · Once
- Hypokalemia maintenance/treatment · 50 grams PO daily; 1 mEq/kg/hour IV drip · PO/IV · Daily/Continuous
投与経路
禁忌
- Hyperkalemia
- Renal failure or severe renal impairment
- Severe hemolytic reactions
- Untreated Addison's disease (hypoadrenocorticism)
- Acute dehydration
- GI motility impairment (for solid oral dosage forms)
有害事象
- Hyperkalemia (muscle weakness, cardiac conduction disturbances)
- Gastrointestinal distress (vomiting, diarrhea) with oral therapy
- Vein irritation and phlebitis with IV therapy
薬物相互作用
- ACE Inhibitors (e.g., enalapril) · Potassium retention may occur; increased risk for hyperkalemia.
- Digoxin · In patients with severe or complete heart block receiving digitalis therapy, it is often recommended not to use potassium salts.
- NSAIDs · Oral potassium given with non-steroidal anti-inflammatory agents may increase the risk of gastrointestinal adverse effects.
- Potassium-Sparing Diuretics (e.g., spironolactone) · Potassium retention may occur; increased risk for hyperkalemia.
モニタリング
- Serum potassium levels
- Other electrolytes (sodium, chloride, magnesium, calcium)
- Acid/base status
- Blood glucose
- ECG (especially during IV administration)
- CBC
- Urinalysis and renal function parameters
過量投与
Fatal hyperkalemia may develop if potassium salts are administered too rapidly IV or if potassium renal excretory mechanisms are impaired. **Clinical Signs of Hyperkalemia:** * Muscular weakness * Gastrointestinal disturbances * Severe cardiac conduction disturbances (bradycardia, atrial standstill, ventricular fibrillation, asystole) **Treatment of Hyperkalemia:** * Immediate discontinuation of the potassium supplement. * Continuous ECG, acid/base, and electrolyte monitoring. * **Medical interventions:** Glucose/insulin infusions (drives K+ into cells), sodium bicarbonate (alkalinization drives K+ into cells), calcium therapy (cardioprotective, antagonizes K+ effects on the heart), and polystyrene sulfonate resin (binds K+ in the GI tract).
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