In a patient with rhabdomyolysis and markedly elevated creatine kinase, when should intravenous sodium bicarbonate be administered, what dosing regimen is recommended, and how should the therapy be monitored?

Sodium Bicarbonate in Rhabdomyolysis: Evidence-Based Recommendations

Primary Recommendation

Sodium bicarbonate should NOT be routinely administered in rhabdomyolysis and is only indicated if documented metabolic acidosis with pH <7.1 develops; the cornerstone of treatment is aggressive intravenous fluid resuscitation targeting urine output ≥300 mL/hour, initiated within 6 hours of muscle injury. 1, 2

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When to Withhold Bicarbonate Therapy

The Eastern Association for the Surgery of Trauma conditionally recommends AGAINST routine bicarbonate use in rhabdomyolysis, as meta-analysis showed no improvement in acute renal failure rates or dialysis requirements compared to fluids alone. 1

• Three studies specifically found no significant difference in ARF rates between patients receiving versus not receiving sodium bicarbonate in rhabdomyolysis. 2
• A retrospective ICU analysis demonstrated that once appropriate saline expansion is provided (approximately 200 mL/hour), the addition of mannitol and bicarbonate appears unnecessary—all patients avoided established renal failure with saline alone. 3
• The quality of evidence is very low (retrospective studies), but the consistent finding across multiple investigations is that bicarbonate adds no benefit beyond aggressive fluid resuscitation. 1

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Specific Indication: Documented Severe Acidosis

Administer sodium bicarbonate ONLY if arterial pH falls below 7.1 with documented metabolic acidosis, not prophylactically. 4, 5

Dosing Protocol When pH <7.1:

• Initial bolus: 50 mmol (50 mL of 8.4% solution) IV given slowly over several minutes. 4
• Alternative dosing: 1-2 mEq/kg IV administered slowly. 4
• Target pH: 7.2-7.3, NOT complete normalization. 4
• Repeat dosing guided by arterial blood gas analysis every 2-4 hours, not empirically. 4

Critical Safety Requirements:

• Ensure adequate ventilation BEFORE each bicarbonate dose, as bicarbonate generates CO₂ that must be eliminated to prevent paradoxical intracellular acidosis. 4, 2
• Monitor serum sodium to avoid exceeding 150-155 mEq/L. 4
• Monitor serum potassium every 2-4 hours, as bicarbonate shifts potassium intracellularly and can precipitate severe hypokalemia. 4
• Monitor ionized calcium, as large bicarbonate doses can decrease free calcium and worsen cardiac contractility. 4

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Primary Treatment Algorithm for Rhabdomyolysis

Immediate Actions (Within 6 Hours of Muscle Injury):

1. Initiate Aggressive IV Fluid Resuscitation:

• Use isotonic crystalloids (0.9% normal saline or balanced crystalloids like Plasmalyte). 6, 2
• Target urine output: ≥300 mL/hour for at least the first 24 hours in adults. 5, 2
• Fluid rate: Typically 200-400 mL/hour initially, adjusted to maintain target urine output. 3, 2
• Delayed fluid administration beyond 6 hours significantly increases ARF risk—eight investigations confirmed this critical timing window. 2

2. Monitor Creatine Kinase (CK) Levels:

• Diagnosis requires CK ≥5-10 times upper limit of normal (typically >1,000 U/L). 5, 7
• Continue IV fluids until CK falls below 1,000 U/L. 5

3. Assess for Complications:

• Check arterial blood gas if acidosis suspected (pH <7.1 is bicarbonate threshold). 4, 5
• Monitor for hyperkalemia, hypocalcemia, hyperphosphatemia—these require specific management. 5, 7
• Evaluate for compartment syndrome requiring fasciotomy. 5
• Screen for disseminated intravascular coagulation. 5, 7

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Monitoring Parameters During Treatment

• Urine output: Hourly measurement targeting ≥300 mL/hour. 5, 2
• Serum creatinine: Daily to assess renal function trajectory. 3
• CK levels: Every 12-24 hours until trending below 1,000 U/L. 5
• Arterial blood gases: Only if clinical acidosis suspected (pH <7.1). 4
• Electrolytes: Every 6-12 hours initially (sodium, potassium, calcium, phosphate). 4, 5
• Fluid balance: Strict intake/output monitoring to avoid fluid overload while maintaining target urine output. 2

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Common Pitfalls to Avoid

• Do NOT give bicarbonate prophylactically or for "urine alkalinization"—no controlled trials demonstrate benefit, and three studies showed no ARF difference. 1, 2
• Do NOT delay fluid resuscitation—waiting beyond 6 hours dramatically increases ARF risk. 2
• Do NOT use inadequate fluid volumes—target urine output of 300 mL/hour requires aggressive rates (often 200-400 mL/hour IV). 2
• Do NOT give bicarbonate without ensuring adequate ventilation—this causes paradoxical intracellular acidosis and worsens outcomes. 4
• Do NOT ignore electrolyte abnormalities—hyperkalemia and hypocalcemia can cause fatal arrhythmias. 5, 7
• Do NOT continue fluids indefinitely—taper once CK <1,000 U/L and urine output stable. 5

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Special Considerations

If Urine Output Remains <300 mL/Hour Despite Adequate Fluids:

• Consider mannitol (not bicarbonate) to augment diuresis, though evidence for benefit is limited. 5, 2
• Reassess volume status and hemodynamics—may need vasopressor support if hypotensive. 6
• Evaluate for compartment syndrome requiring surgical decompression. 5

Contraindications to Aggressive Fluid Resuscitation:

• Advanced heart failure with volume overload. 8
• Pulmonary edema or significant respiratory compromise. 6
• In these cases, consider early renal replacement therapy rather than pushing fluids. 6

Renal Replacement Therapy Indications:

• Persistent oliguria despite adequate fluid resuscitation. 6
• Severe hyperkalemia unresponsive to medical management. 4
• Volume overload preventing adequate fluid administration. 6
• Severe metabolic acidosis (pH <7.1) refractory to bicarbonate. 4

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Prognosis

• Overall mortality in rhabdomyolysis may reach 8% despite treatment. 7
• Acute renal failure occurs in 4-33% of patients. 7
• Full recovery of renal function is common when early aggressive IV fluid resuscitation is provided. 7
• Prognosis is favorable when treatment begins within 6 hours and maintains urine output ≥300 mL/hour. 2