What electrolytes and molecules are affected in Acute Kidney Injury (AKI)?

Electrolytes and Molecules Affected in Acute Kidney Injury (AKI)

In acute kidney injury, the primary electrolyte and molecular disturbances include hyperkalemia, metabolic acidosis, hyperphosphatemia, hypocalcemia, and hyponatremia, with severity correlating to AKI progression and mortality risk. 1

Common Electrolyte Abnormalities in AKI

Potassium Abnormalities

• Hyperkalemia is one of the most common and dangerous electrolyte disturbances in AKI, with higher serum potassium levels (>4.6 mmol/L) associated with progression to severe AKI and increased mortality 2
• After initiation of renal replacement therapy, the pattern may shift to hypokalemia, which requires careful monitoring 1, 3

Acid-Base Disturbances

• Metabolic acidosis is a hallmark finding in AKI due to impaired acid excretion and bicarbonate reabsorption 1
• After dialysis initiation, patients may develop metabolic alkalosis due to overcorrection, which typically self-corrects between dialysis sessions 4

Phosphate Abnormalities

• Hyperphosphatemia is common in AKI due to decreased phosphate excretion 1
• Severe hyperphosphatemia (≥4.5 mg/dL) is associated with significantly higher 28-day and 90-day mortality in septic AKI patients 3
• Paradoxically, hypophosphatemia can develop during intensive renal replacement therapy with a prevalence of up to 60-80% 5

Calcium Abnormalities

• Hypocalcemia is prevalent in AKI, occurring in approximately 51.5% of patients 6
• The mechanism involves impaired vitamin D metabolism and calcium-phosphate imbalance 7
• Post-dialysis hypercalcemia may occur but rarely requires immediate intervention unless symptomatic 4

Sodium Abnormalities

• Hyponatremia affects approximately 53% of AKI patients 6
• Both hyponatremia (<137 mmol/L) and hypernatremia (>141 mmol/L) are associated with higher risk of progression to severe AKI and increased mortality 2
• Renal sodium loss accounts for approximately 64.7% of hyponatremia cases in AKI 6

Magnesium Abnormalities

• Hypomagnesemia occurs in up to 34.9% of AKI patients 6
• Renal magnesium wasting accounts for 83.3% of cases 6
• Particular attention to magnesium levels is needed when using regional citrate anticoagulation during renal replacement therapy 5

Patterns of Electrolyte Disturbances Based on AKI Stage and Treatment

Pre-Dialysis AKI

• Electrolyte disorders are prevalent among hospitalized patients with AKI, with reported cumulative incidence up to 65%, especially in critically ill patients 5
• Multiple electrolyte deficiencies are common, with 60% of patients having at least one electrolyte deficiency and 67.6% having at least one electrolyte excess before starting renal replacement therapy 3

Post-Dialysis AKI

• After initiation of continuous renal replacement therapy (CRRT), electrolyte excesses are greatly improved, but deficiencies like hypokalemia and hypophosphatemia become more prevalent 3
• Monitoring electrolytes 24 hours post-dialysis is essential to assess for rebound abnormalities or overcorrection 5, 4

Clinical Significance and Outcomes

• AKI occurs in approximately 90.9% of patients with exertional heat stroke, with 16.7% requiring acute dialysis 6
• Hyperphosphatemia confers a 2.2-fold and 2.6-fold increased risk of 28-day and 90-day mortality, respectively, in septic AKI patients undergoing CRRT 3
• Abnormal serum sodium or potassium levels before AKI diagnosis are associated with AKI progression and poor prognosis, with lower serum sodium and higher serum potassium more likely to progress to AKI stage 3 or death 2

Monitoring Recommendations

• Electrolyte abnormalities should be closely monitored in all AKI patients, particularly those receiving renal replacement therapy 5
• For patients on dialysis, check electrolytes 24 hours post-dialysis to assess for rebound abnormalities or overcorrection 5, 4
• Pay particular attention to potassium levels, as both hyperkalemia and hypokalemia can precipitate cardiac arrhythmias in AKI patients 4
• Monitor for symptoms of electrolyte imbalances rather than treating laboratory values alone 4

Pitfalls to Avoid

• Avoid aggressive correction of post-dialysis electrolyte abnormalities, as this can lead to dangerous fluctuations 5, 4
• Be cautious with calcium supplementation in AKI patients with elevated calcium levels, as this can worsen vascular calcification 5, 4
• Remember that dialysis patients have wide fluctuations in electrolytes between treatments, and laboratory values should be interpreted in this context 5, 4