From the Guidelines
For hyponatremia with acute kidney injury (AKI) in the setting of diarrhea and volume depletion, the primary treatment is careful volume resuscitation with isotonic fluids, typically normal saline (0.9% NaCl), as recommended by the KDIGO clinical practice guideline for acute kidney injury 1. Begin with a 1-2 L bolus of normal saline, followed by maintenance fluids at 100-150 mL/hour, adjusting based on clinical response.
- Monitor serum sodium levels every 4-6 hours initially, aiming for correction rates not exceeding 8 mEq/L in 24 hours to avoid osmotic demyelination syndrome.
- Simultaneously address the underlying cause of diarrhea with appropriate antimicrobials if infectious, or anti-motility agents like loperamide 4mg initially followed by 2mg after each loose stool (maximum 16mg/day) if non-infectious.
- Ensure electrolyte replacement including potassium and bicarbonate if needed.
- Avoid hypotonic fluids which can worsen hyponatremia. This approach works because the hyponatremia is likely hypovolemic in nature, caused by both sodium and free water losses from diarrhea with subsequent ADH release.
- The AKI is pre-renal from volume depletion, and should improve with adequate fluid resuscitation. If the patient has heart failure or cirrhosis, fluid administration should be more cautious with close hemodynamic monitoring to prevent volume overload, as suggested by the EASL clinical practice guidelines for the management of patients with decompensated cirrhosis 1. In addition, the use of diuretics should be avoided in the treatment of AKI, except in the management of volume overload, as recommended by the KDIGO clinical practice guideline for acute kidney injury 1 and the Kidney International guideline 1.
From the Research
Diagnosis of Hyponatremia with Acute Kidney Injury (AKI)
- Hyponatremia is defined by a serum sodium level of less than 135 mEq/L and most commonly results from water retention 2.
- When evaluating patients, clinicians should categorize them according to their fluid volume status (hypovolemic hyponatremia, euvolemic hyponatremia, or hypervolemic hyponatremia) 2.
- AKI is common in patients presenting with hyponatremia and is usually of prerenal origin, with a frequent cause being diuretics 3.
Management of Hyponatremia with AKI
- The approach to managing hyponatremia should consist of treating the underlying cause 2.
- For patients with severely symptomatic hyponatremia, US and European guidelines recommend treating with bolus hypertonic saline to reverse hyponatremic encephalopathy by increasing the serum sodium level by 4 mEq/L to 6 mEq/L within 1 to 2 hours but by no more than 10 mEq/L within the first 24 hours 2, 4.
- However, overly rapid correction of chronic hyponatremia may cause osmotic demyelination, a rare but severe neurological condition 2, 5.
- In patients with AKI, admission serum creatinine was 271 ± 252 µmol/L and the origin was usually prerenal, and survivors recovered with fluid resuscitation only 3.
- Diuretics are ineffective and even detrimental in the prevention and treatment of AKI, and neither shorten the duration of AKI, nor reduce the need for renal replacement therapy 6.
Considerations in Diarrhea and Hypovolemia
- Symptoms caused by hypovolemia can be misinterpreted as severely symptomatic hyponatremia, and diuresis should be monitored 4.
- Isotonic fluid replacement can correct both hypovolemia and hyponatremia, and did not lead to overly rapid correction of hyponatremia in patients with AKI 3.
- Aggressive potassium supplement would have been the first-line therapy for patients presenting with chronic hyponatremia and hypokalemia associated with volume depletion 5.