1. Journal Club: AKI and timing of RRT in Post-op ITU Patients
Dr Andrew Stein
Consultant in Renal and Acute Medicine
UHCW, Coventry

2. U-curve association between timing of renal replacement therapy initiation and in-hospital mortality in postoperative acute kidney injury. Shiao et al. PLoS One. 2012; 7(8): e42952

3. Background 1 – Epidemiology and Prognosis
5-10% of hospital admissions have AKI or AKI/CKD; 35-45% in a med take audit on Oct 2012
5-15% ICU patients require RRT
Despite advances in Rx, AKI still has a high mortality:
20% overall
30% if referred to renal
50% if dialysed
70% on ICU

4. AKI/CKD 100 Consecutive Medical Take Patients at UHCW: Oct 2012

5. Background 2
Postoperative acute kidney injury (AKI) is associated with poor outcome in surgical patients
Uncertain whether ‘early RRT’ on ICU is of benefit
This study evaluated whether the timing of renal replacement therapy (RRT) initiation affects the in-hospital mortality of patients with postoperative AKI

6. Method 1 Multicentre retrospective observational study
ICUs in a tertiary hospital (National Taiwan University Hospital) and its branch hospitals in Taiwan between January, 2002, and April, 2009
Adult patients with postoperative AKI who underwent RRT

7. Method 2
Demographic data, comorbid diseases, types of surgery and RRT, and the indications for RRT were documented
Patients were categorised according to the period of time between the ICU admission and RRT initiation as the early (EG, 1 day), intermediate (IG, 2-3 days), and late (LG, >4 days) groups
In hospital mortality rate was the primary endpoint

8. Results 1 648 (418 men, mean age 63.0±15.9 years) were enrolled
379 patients (58.5%) died during the hospitalisation
Mortality showed a U-shaped curve

9. Results 2

10. Results 3

11. Results 4
First peak of mortality rate related to the comorbidity and ECMO support
Second peak was associated with older age, sepsis, and later initiation of RRT

12. Results 5

13. Results 6
According to the Cox proportional hazard method (comparing the LG and the IG group): age, diabetes, cirrhosis, extracorporeal membrane oxygenation support, initial neurological dysfunction pre-RRT mean arterial pressure, inotropic equivalent, APACHE II scores and sepsis were independent predictors of in-hospital mortality (p<0.001)

14. Limitations of Study
Observational retrospective studies are prone to bias. Not a randomised prospective randomised controlled trial (RCT)
This study investigated patients predominantly undergoing CV surgery. Results may not serve as a representative sample of ICU AKI patients
Study was designed to enroll only patients with postoperative AKI requiring RRT. Cannot compare current data with those whose renal function recovered without RRT or those who died before RRT initiation
One of the predefined indications for RRT initiation, CVP>12 mmHg may not be an adequate proxy for fluid overload

15. Known AKI Prognostic Factors
Older age
Pre-existing CKD
Cause of AKI (eg sepsis)
Multiorgan failure (ie, the more organs that fail, the worse the prognosis)
Oliguria
Hypotension
Vasopressor support

16. Renal Outcomes of ICU AKI
The duration and severity of AKI predicts the development of progressive chronic kidney disease (CKD)
In a large ICU follow-up study, of patients with AKI, 57% returned to normal renal function, 33% had mild to moderate CKD and 10% severe renal failure (Schiffl, NDT 2005)

17. Conclusions
This study found a U-curve association between the timing of RRT initiation, in post-op ICU surgical patients, and in-hospital mortality
9 predictors of outcome were described