Journal Club: AKI and timing of RRT in Post-op ITU Patients

Dr Andrew SteinConsultant in Renal and Acute Medicine

UHCW, Coventry

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

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

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

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

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

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

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

Results 2

Results 3

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

Results 5

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)

Limitations of Study1. Observational retrospective studies are prone to bias.

Not a randomised prospective randomised controlled trial (RCT)

2. This study investigated patients predominantly undergoing CV surgery. Results may not serve as a representative sample of ICU AKI patients

3. 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

4. One of the predefined indications for RRT initiation, CVP>12 mmHg may not be an adequate proxy for fluid overload

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

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)

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