Acute Kidney Injury in Pregnancy

Acute kidney injury in pregnancy is a sudden fall in kidney function, with creatinine rising by 26 micromol/L or more in 48 hours or to 1.5 times baseline. Normal pregnancy creatinine is 40 to 75 micromol/L, so values above 90 micromol/L need action. Causes include hyperemesis, haemorrhage, sepsis (septic abortion, puerperal sepsis, pyelonephritis), preeclampsia and HELLP syndrome, abruption, acute fatty liver, thrombotic microangiopathy and drugs.

• Risk factors: haemorrhage, sepsis, unsafe abortion, severe preeclampsia, NSAID use, aminoglycosides.
• Early recognition and fluid resuscitation can prevent progression.
• Dialysis is needed in a minority.

Women have reduced urine output (below 0.5 mL/kg/hour for 6 hours), nausea, drowsiness, oedema and breathlessness, along with features of the cause such as fever, bleeding or hypertension.

• Urine output below 400 mL in 24 hours.
• Hypovolaemia or fluid overload.
• Differential diagnosis: prerenal azotaemia, acute tubular necrosis, obstruction (uterine, stones), glomerulonephritis, thrombotic thrombocytopenic purpura, haemolytic uraemic syndrome, chronic kidney disease.
• Complications: hyperkalaemia, pulmonary oedema, metabolic acidosis, uraemia, need for dialysis, preterm birth, fetal death, maternal death, chronic kidney disease.

The approach is to confirm injury, find the cause and look for complications.

• Creatinine and urea (repeat daily), sodium, potassium, bicarbonate, calcium, phosphate, glucose.
• Urinalysis with microscopy, urine sodium, urine protein to creatinine ratio, full blood count and film, liver enzymes, lactate dehydrogenase, coagulation screen, blood cultures.
• Renal and pelvic ultrasound for obstruction; ECG for hyperkalaemia; chest X-ray with shielding.
• Venous blood gas and lactate.

The principle is to restore perfusion, stop nephrotoxins, treat the cause, and plan dialysis and delivery.

• Supportive: strict fluid balance with urinary catheter and hourly output; daily weight; stop NSAIDs, aminoglycosides and contrast; low potassium and low salt diet; oxygen if hypoxic; left lateral position.
• Pharmacological: Ringer's lactate or sodium chloride 0.9 percent 500 mL IV over 15 minutes, repeated and reassessed until perfusion returns; transfuse for haemorrhage; ceftriaxone 2 g IV daily plus metronidazole 500 mg IV 8-hourly for sepsis, within 1 hour; noradrenaline 0.05 micrograms/kg/minute IV titrated for mean arterial pressure of 65 mmHg or more; furosemide 40 to 80 mg IV for fluid overload; hyperkalaemia (potassium above 6.0 mmol/L or ECG changes): calcium gluconate 10 percent 10 mL IV over 10 minutes, then soluble insulin 10 units IV with dextrose 50 percent 50 mL, and salbutamol 10 to 20 mg nebulised; sodium bicarbonate 8.4 percent 50 mL IV for pH below 7.2; magnesium sulphate 4 g IV over 20 minutes then 1 g per hour for preeclampsia (reduce to 0.5 g per hour if oliguric, with levels monitored).
• Procedures: dialysis for refractory hyperkalaemia, pulmonary oedema, acidosis, uraemic symptoms or creatinine above 500 micromol/L; relieve obstruction by ureteric stent or nephrostomy; delivery for preeclampsia, abruption, fetal compromise or maternal deterioration.
• Special groups: septic abortion needs evacuation of the uterus within 6 hours of antibiotics; thrombotic thrombocytopenic purpura needs plasma exchange 1 plasma volume daily with prednisolone 1 mg/kg oral daily; women with eclampsia need magnesium dose reduction in oliguria.
• Red flags: potassium above 6.0 mmol/L, urine output below 0.3 mL/kg/hour, pulmonary oedema, pH below 7.2, confusion, bleeding.
• Follow-up: creatinine and electrolytes daily until stable, then weekly; renal review at 3 months postpartum; check blood pressure and urine protein.