Sodium Bicarbonate
**Sodium bicarbonate** is a systemic and urinary alkalinizing agent widely used in veterinary emergency and critical care, as well as for chronic management of specific conditions. - **Emergency Acid-Base Management**: Primarily utilized to correct severe metabolic acidosis, particularly when the underlying cause cannot be rapidly reversed and blood pH drops to critically low levels. - **Electrolyte Crises**: Serves as an adjunctive treatment for life-threatening **hyperkalemia** (by driving potassium intracellularly) and **hypercalcemia**. - **Urinary Alkalinization**: Administered orally to manage or prevent specific uroliths (e.g., urate, cystine) by increasing urine pH. > **Clinical Pearl**: The routine use of sodium bicarbonate in cardiopulmonary resuscitation (CPR) and diabetic ketoacidosis (DKA) has fallen out of favor. In DKA, it can worsen intracellular hypokalemia and cause paradoxical CNS acidosis. In CPR, it can lead to hypercapnia if the patient is not adequately ventilated.
กลไกการออกฤทธิ์: Sodium bicarbonate acts as an exogenous source of bicarbonate anion (**$HCO_3^-$**), which is the primary extracellular buffer in the body. - **Buffering Acidosis**: $HCO_3^-$ combines with free hydrogen ions ($H^+$) to form carbonic acid ($H_2CO_3$), which then dissociates into water ($H_2O$) and carbon dioxide ($CO_2$). - **Pathway**: **$HCO_3^-$ + $H^+$ → $H_2CO_3$ → $H_2O$ + $CO_2$** (The $CO_2$ must be exhaled via the lungs, highlighting the need for adequate ventilation). - **Hyperkalemia Management**: By increasing blood pH, it stimulates the $Na^+/H^+$ exchanger and subsequently the $Na^+/K^+$-ATPase pump, driving **potassium into cells** and rapidly lowering serum potassium levels. - **Urinary Alkalinization**: Bicarbonate is excreted in the urine, raising the pH. This increases the solubility of weak acids (like uric acid and cystine) and decreases the solubility of weak bases.
ขนาดยาตามชนิดสัตว์
- Acidosis (Ruminants) · 2-5 mEq/kg IV for a 4-8 hour period · IV · Once · Over 4-8 hours
- Acidosis (Ruminants) · 2-5 mEq/kg IV for a 4-8 hour period · IV · Once · Over 4-8 hours
- Severe metabolic acidosis · mEq of bicarbonate required = 0.5 x body weight in kg x (desired total CO2 mEq/L minus measured total CO2 mEq/L). Give 1/2 of the calculated dose slowly over 3-4 hours IV. · IV · Once · Over 3-4 hours · Recheck blood gases and assess clinical status. Avoid over-alkalinization.
- Metabolic acidosis secondary to uremia · 0.3 x body weight (kilograms) x the base deficit. Administration of one third of this dose slowly IV and the rest placed in the intravenous fluids. OR 1-2 mEq/kg of bicarbonate can be given as a slow IV bolus if blood gas is not possible. · IV · Once · Over several hours · Avoid rapid IV boluses. Recheck blood gas after 2-4 hours.
- Adjunctive therapy of diabetic ketoacidosis · Dose (in mEq) = body weight in kgs. x 0.4 x (12 - patient's bicarbonate) x 0.5. Give above dose over 6 hours in IV fluids. · IV · Once · Over 6 hours · Only if plasma bicarbonate is <=11 mEq/L. Recheck and repeat if still <=11 mEq/L. Use is controversial.
- Adjunctive treatment of hypercalcemic crisis · mEq of bicarbonate required = 0.3 x body weight in kg x (desired plasma bicarbonate mEq/L - measured plasma bicarbonate mEq/L); or 1 mEq/kg IV every 10-15 minutes; maximum total dose: 4 mEq/L · IV · q10-15m · Until effect or max dose
- Adjunctive therapy for hyperkalemic crises · 2-3 mEq/kg IV over 30 minutes (if decreased tissue perfusion/renal failure and no DKA) OR 1-2 mEq/kg IV slowly · IV · Once · Over 30 minutes or slowly · Must be used judiciously.
วิธีการให้ยา
ข้อห้ามใช้
- Metabolic or respiratory alkalosis
- Excessive chloride loss secondary to vomiting or GI suction
- Patients at risk for development of diuretic-induced hypochloremic alkalosis
- Hypocalcemia (alkalosis may induce tetany)
- Hypoventilating patients
- Hypercapnoeic patients
- Animals unable to effectively expel carbon dioxide
อาการไม่พึงประสงค์
- Metabolic alkalosis
- Hypokalemia
- Hypocalcemia
- 'Overshoot' alkalosis
- Hypernatremia
- Volume overload
- Congestive heart failure
- Shifts in the oxygen dissociation curve (decreased tissue oxygenation)
- Paradoxical CNS acidosis leading to respiratory arrest
- Hypercapnia (if not well ventilated during CPR)
- Predisposition to ventricular fibrillation
- Hypernatraemia
- Congestive heart failure (due to sodium load)
- Decreased tissue oxygenation (shift in oxygen dissociation curve)
- Paradoxical CNS acidosis
- Respiratory arrest
อันตรกิริยาระหว่างยา
- Anticholinergic agents · Concomitant oral sodium bicarbonate may reduce absorption; administer separately
- Azole antifungals (ketoconazole, itraconazole) · Concomitant oral sodium bicarbonate may reduce absorption; administer separately
- Ciprofloxacin, Enrofloxacin · Solubility is decreased in an alkaline environment; monitor for signs of crystalluria
- Corticosteroids · Patients receiving high dosages of sodium bicarbonate and ACTH or glucocorticoids may develop hypernatremia
- Diuretics (e.g., thiazides, furosemide) · Concurrent use in patients receiving potassium-wasting diuretics may cause hypochloremic alkalosis
- Ephedrine · When urine is alkalinized, excretion may be decreased
- Histamine2 blocking agents (e.g., cimetidine, ranitidine) · Concomitant oral sodium bicarbonate may reduce absorption; administer separately
- Iron products · Concomitant oral sodium bicarbonate may reduce absorption; administer separately
- Oral medications (general) · Can increase or reduce absorption rate/extent; avoid giving other drugs within 12 hours of oral sodium bicarbonate
- Quinidine · When urine is alkalinized, excretion may be decreased
- Salicylates · When urine is alkalinized, excretion of weakly acidic drugs may be increased
การติดตาม
- Acid/base status (venous or arterial blood gases)
- Serum electrolytes (especially potassium, calcium, and sodium)
- Urine pH (if being used to alkalinize urine)
- Blood gas analysis (pH, pCO2, HCO3-)
- Serum electrolytes (Na+, K+, Ca2+)
- Respiratory rate and effort
- Clinical signs of fluid overload or congestive heart failure
การได้รับยาเกินขนาด
Overdose or overly rapid administration can cause **severe alkalosis**, leading to irritability, muscle twitching, or **tetany** (due to a sudden drop in ionized calcium). - **Mild Overdose**: May only require discontinuing the bicarbonate therapy or using a rebreathing mask. - **Severe Alkalosis**: May require intravenous calcium therapy to treat tetany. - **Electrolyte Correction**: Sodium chloride or potassium chloride may be necessary if hypokalemia or hypochloremia is present. > Always thoroughly check dosages and frequently monitor electrolyte and acid/base status during administration.
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