Background
Acute kidney injury(AKI) during pregnancy or postpartum is associated with significant maternal and neonatal morbidity. It is increasingly recognised that AKI may remain unidentified due to lack of established pregnancy-specific reference ranges for serum creatinine, poor reliability of eGFR in pregnancy, and previously unmeasured baseline renal function. We aimed to determine the theoretical proportion of ‘missed’ AKI based on serum creatinine reported to the ANZICS data registry.
Methods
Data relating to women of child-bearing age(15-49 yrs) admitted to ICU was obtained from the ANZICS CORE registry(2006-2015). AKI prevalence and severity was determined using: (1)the highest serum creatinine(Cr) in the first 24hrs of ICU admission, (2)validated classification systems (RIFLE/AKIN/KDIGO), and (3)published population estimates of baseline serum creatinine in pregnancy (median Cr=53 umol/L) and non-pregnant women 15-49yrs(median Cr=74 umol/L). Definitions of AKI severity: Mild =1.5-1.9 x estimated baseline Cr, Moderate/Severe =>2 x estimated baseline Cr.
Results
143,484 eligible patient episodes were identified, of which 11,176 were during pregnancy or postpartum. AKI prevalence using non-pregnant baseline Cr was 6.7% (n=749) in the pregnancy group and 8.5% (n=11,492) in non-pregnant age-matched controls, p<0.0001. Adjusting for pregnancy (AKI=Cr >80 umol/L) increased prevalence to 17.1% (n=1,911) in the pregnancy group. Moderate/Severe AKI prevalence was 7.7% (n=860) in pregnancy, and 5.3% (n=12,609) in the non-pregnant group, p<0.0001. Leading ICU admission diagnoses in the pregnancy group with AKI were hypertensive disorders of pregnancy and complications associated with emergency Caesarian section. AKI was an independent risk factor for mortality, with a rate of 0.4% in the pregnancy group vs 1.5% in non-pregnant group, p<0.0001.
Conclusion
Using this model, 60% of pregnancy-related AKI may be missed if serum creatinine-based definitions are used without adjusting for pregnancy. This observation reinforces the need for greater awareness in identifying and reporting AKI, and developing improved techniques for measuring renal function in pregnancy.