Cardiac-surgery-associated acute kidney injury (CSA-AKI) more than doubles the risk of kidney failure, a data linkage study between two long-standing Australian clinical quality registries has found.
The study’s findings “…reinforce the need for improved perioperative surgical and perfusion management for all cardiac surgical patients…” to reduce the incidence of CSA-AKI.
“These improvements to clinical care would moderate kidney failure progression and ameliorate the significant burden of kidney disease on the community and the health system,” the study concluded.
The study comprised data from more than 90,000 adults undergoing cardiac surgery in Australia between January 2010 and December 2018 and reported to the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) Cardiac Surgery Database.
Most patients were male (73.7%) with a median age of 67 years and with comorbidities such as hypertension (71.9%), obesity (35.3%) and diabetes (28.9%). The most common procedures were isolated coronary artery bypass grafting (CABG; 50.8%), isolated valve surgery (21.8%), and valve with CABG (10.7%).
The study, published in BMC Nephrology [link here], found postoperative AKI occurred in more than a quarter of cases – 20.0% Stage 1, 3.3% Stage 2 and 3.0% Stage 3. Of the stage 3 AKI cases, half (53.2%) required dialysis.
The study found 465 people (0.51%) developed kidney failure – estimated from incident kidney replacement therapy in data linkage with the Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry – during a median follow-up time of 3.4 years.
The overall cumulative incidence of kidney failure at five years post-surgery was 0.65%.
The investigators found Stage 1-2 AKI increased the long term risk of kidney failure more than two-fold (SHR>2.5) while Stage 3 AKI increased the risk more than four-fold (SHR >4.4) compared to no AKI.
A multivariate analysis showed the adjusted risk of kidney failure:
- tended to decrease with increasing age group
- increased in patients with hypertension and diabetes
- decreased in obese patients
- was highest in patients undergoing isolated CABG and aortic procedures compared to isolated valve or valve with CABG
- was highest in patients with the lowest preoperative eGFR.
The investigators, led by Dr Dominic Keuskamp from ANZDATA, said some of their findings were counterintuitive and paradoxical.
For example, the inverse relationship between age and kidney failure risk may seem counterintuitive.
“However, we suggest that selection for cardiac surgery leads to younger cohorts with relatively more aggressive systemic disease, and subsequently kidney disease,” they said.
As well, the obesity paradox may be partly explained given low BMI is considered a marker for frailty, malnutrition or cachexia.
They said the study represented the largest reported samples of cardiac surgeries for this type of analysis.
“The increased risk of kidney failure associated with even stage 1-2 CSA-AKI highlights the critical importance of AKI prevention, while also the rigorous measurement of injury severity in the estimation of risk,” the investigators said.
“The enduring influence of pre-existing CKD or its risk factors (especially diabetes) on the emergence of postoperative kidney failure underscores the importance of early detection of CKD, which remains largely preventable through modifiable risk factors, and long-term nephrology follow-up following surgery.”