In an adult with diabetic ketoacidosis, acute kidney injury, and chronic kidney disease, what investigations and laboratory tests are required and what is the appropriate treatment plan, including specific medication dosages?

Management of DKA with AKI and CKD

In adults with diabetic ketoacidosis complicated by acute kidney injury and chronic kidney disease, initiate aggressive fluid resuscitation with isotonic saline at 15-20 ml/kg/hour (1-1.5 liters in the first hour), followed by insulin therapy and intensive potassium monitoring, while adjusting fluid rates and insulin dosing based on renal function and avoiding rapid osmolality shifts. 1

Initial Laboratory Evaluation

Essential Diagnostic Tests

• Arterial blood gas to document metabolic acidosis with pH <7.3 1
• Serum β-hydroxybutyrate specifically (not nitroprusside-based tests, which miss this predominant ketone and should not be used for monitoring) 1
• Serum glucose (typically >250 mg/dL, though euglycemic DKA exists with glucose <250 mg/dL, particularly with SGLT2 inhibitor use) 1, 2
• Serum bicarbonate to confirm levels <15-18 mEq/L 1
• Electrolytes with calculated anion gap (>10 mEq/L in mild DKA, >12 mEq/L in moderate-severe) 1, 3
• BUN/creatinine to assess renal function and hydration status, critical given the AKI/CKD context 1
• Corrected serum sodium by adding 1.6 mEq/L for each 100 mg/dL glucose above 100 mg/dL 1

Additional Monitoring Tests

• Serum phosphate, magnesium, and calcium (typical deficits: phosphate 3-5 mmol/kg, magnesium 4-6 mEq/kg, calcium 1-2 mEq/kg) 1
• Complete blood count with differential to identify infection as precipitating cause 2
• Urinalysis (though avoid relying on urine ketones alone for diagnosis) 1, 2
• A1C for baseline glycemic control assessment 2
• ECG to evaluate for cardiac complications and hyperkalemia 2
• Blood and urine cultures if infection suspected 2

Critical Diagnostic Pitfalls

• Never rely on urine ketone testing alone as it is insufficient and misleading 1
• Exclude other causes of high anion gap metabolic acidosis including lactic acidosis, salicylate toxicity, methanol/ethylene glycol ingestion, uremia, and alcoholic ketoacidosis 1, 3
• Recognize euglycemic DKA particularly in patients on SGLT2 inhibitors 2

Fluid Resuscitation Protocol

Initial Fluid Management

• Isotonic saline (0.9% NaCl) at 15-20 ml/kg/hour during the first hour (1-1.5 liters in average adult) in absence of cardiac compromise 1
• Consider balanced electrolyte solutions as recent evidence shows faster DKA resolution (mean difference -5.36 hours) compared to 0.9% saline, with lower post-resuscitation chloride and sodium levels 4
• After initial hour, adjust to either 0.9% or 0.45% NaCl based on corrected serum sodium and hydration status 5

Renal-Specific Considerations

• Target correction of estimated deficits within 24 hours with serum osmolality change not exceeding 3 mOsm/kg H₂O per hour to prevent cerebral edema 1
• Monitor fluid overload carefully given impaired renal clearance in AKI/CKD 6
• Typical total body deficits: water 6-9 liters, sodium 7-10 mEq/kg, potassium 3-5 mEq/kg, chloride 5-13 mEq/kg 1

Insulin Therapy

Insulin Administration

• Begin insulin therapy after initial fluid resuscitation (not before, to avoid worsening hypovolemia) 7, 8
• Continue insulin infusion until acidosis resolves (bicarbonate ≥18 mEq/L, venous pH >7.3), not just until glucose normalizes 3
• Add dextrose to IV fluids when glucose reaches 200 mg/dL to prevent hypoglycemia while continuing insulin to clear ketoacidosis 3

Critical Insulin Management Error

• Never stop insulin when glucose normalizes before acidosis resolves as this causes rebound hyperglycemia and ketoacidosis 3

Electrolyte Replacement

Potassium Management (Critical in Renal Dysfunction)

• Initiate potassium replacement once renal function is assured (urine output established) 1, 5
• Add 20-30 mEq/L potassium to IV fluids (2/3 KCl and 1/3 KPO₄) until patient is stable and can tolerate oral supplementation 1
• Monitor potassium every 2-4 hours as insulin drives potassium intracellularly, risking life-threatening hypokalemia despite total body depletion 1, 7
• Exercise extreme caution in AKI/CKD as impaired renal excretion increases hyperkalemia risk 9

Bicarbonate Therapy

• **Only consider bicarbonate therapy when pH <6.9** (not necessary if pH >7.0) 3
• In CKD patients with chronic acidosis (serum bicarbonate <22 mmol/L), oral bicarbonate supplementation can be given to maintain normal range once acute DKA resolves 6

Phosphate Considerations

• Typical phosphate deficit is 3-5 mmol/kg 1
• Replacement included in potassium supplementation (1/3 as KPO₄) 1

Monitoring Protocol

Frequency of Assessments

• Check arterial blood gases and serum electrolytes every 2-4 hours during active treatment 3
• Monitor venous pH and anion gap every 2-4 hours to track resolution 3
• Continuous assessment of vital signs, fluid input/output, and mental status 1
• Hemodynamic monitoring to track blood pressure improvement 1

Resolution Criteria

• DKA resolution requires: serum bicarbonate ≥18 mEq/L, glucose <200 mg/dL, and venous pH >7.3 3
• Anion gap closure indicates resolution of ketoacidosis 3

Treatment Complications to Monitor

• Hypoglycemia from excessive insulin 3
• Hypokalemia from insulin-driven intracellular shift 3, 7
• Hyperchloremic acidosis from excessive saline administration (less common with balanced solutions) 3, 4
• Fluid overload particularly in AKI/CKD patients with impaired clearance 6
• Cerebral edema from overly rapid osmolality correction 1

Nephrology Consultation Indications

Refer to nephrology for: 6

• GFR <30 ml/min/1.73 m² (baseline CKD)
• Abrupt sustained fall in GFR (AKI component)
• Progression of CKD (drop in eGFR from baseline by 25% or sustained decline >5 ml/min/1.73 m²/year)
• Need for renal replacement therapy consideration 6

Special Considerations in AKI/CKD Context

Contrast Avoidance

• Avoid gadolinium-containing contrast if GFR <15 ml/min/1.73 m² unless no alternative 6
• If GFR <30 ml/min/1.73 m² and gadolinium required, use macrocyclic chelate preparation 6
• For iodinated contrast with GFR <60 ml/min/1.73 m²: avoid high-osmolar agents, use lowest dose, withdraw nephrotoxic agents, ensure adequate hydration, measure GFR 48-96 hours post-procedure 6

Medication Adjustments

• Withdraw potentially nephrotoxic agents during acute illness 6
• Consider ACE-I/ARB discontinuation during acute DKA with AKI, with careful re-initiation planning 6

Blood Pressure Management Post-Resolution

• Target BP ≤140/90 mmHg if urine albumin <30 mg/24 hours 6
• Target BP <130/80 mmHg if urine albumin ≥30 mg/24 hours 6
• Use ARB or ACE-I in diabetic CKD patients with albuminuria once acute phase resolves 6