Identification of modifiable risk factors for acute kidney injury after coronary artery bypass graft surgery in an Asian population

Miniaturized versus conventional cardiopulmonary bypass and acute kidney injury after cardiac surgery

Introduction:

Acute kidney injury (AKI) is a serious complication after coronary artery bypass grafting (CABG). There are conflicting reports whether a miniaturized cardiopulmonary bypass (MCPB) system is associated with a lower AKI incidence compared with conventional cardiopulmonary bypass (CCPB). It is unknown if AKI risk factors differ between the two groups. We assessed if MCPB decreases AKI after CABG and compared the risk factors between both groups.

Methods:

Sixty-eight Asian patients presenting for elective CABG at a tertiary heart centre were enrolled. They were randomly assigned to MCPB (n=34) or CCPB group (n=34) and followed up in a single-blinded, prospective, randomized, controlled trial. The primary outcome was Acute Kidney Injury Network stage 1 AKI.

Results:

The AKI incidence was 21.5% and was not significantly different between patients undergoing MCPB versus CCPB (21.9% versus 21.2%, p=0.948). The first CPB haematocrit was independently associated with AKI in the MCPB group (Relative Risk [RR]=0.484, 95% Confidence Interval [CI]=0.268-0.876, p=0.016); post-operative blood loss and inflammation were independently associated with AKI in the CCPB group (RR=1.005, 95%CI=1.003-1.007, p<0.001; RR=1.018, 95%CI=1.010-1.028, p<0.001).

Conclusion:

The MCPB system is not associated with a lower incidence of AKI in Asian patients undergoing CABG. Risk factors for AKI differed between patients using the MCPB and CCPB systems.

The inflammatory response between miniaturised and conventional cardiopulmonary bypass after cardiac surgery in an Asian population

INTRODUCTION

We compared the systemic inflammatory response of the MCPB system to the CCPB system with cell salvage and phosphorylcholine-coated tubing amongst Asian patients undergoing coronary artery bypass grafting.

METHODS

Seventy-eight patients were randomly assigned to the MCPB or the CCPB groups equally and followed up in a prospective, single-blinded, randomised, controlled trial. Levels of TNF-α, IL-6, CRP and LDH were measured peri-operatively.

RESULTS

The systemic inflammatory response was similar in both groups (TNF-α: p=0.222; IL-6: p=0.991; CRP: p=0.258). Only haemolysis was significantly higher in the CCPB group (LDH: p=0.011). The MCPB system was twice more expensive, but had a near 4-fold cost saving in tranfusions. Overall, the MCPB system cost 20% more than the modified CCPB system.

CONCLUSION

These results corroborate with studies that demonstrated the avoidance of cardiotomy suction rather than the MCPB system, itself, leads to an attenuated inflammatory response. The absence of obvious clinical benefit and the higher costs involved with the MCPB system would preclude its routine use.

Persistent kidney injury at hospital discharge after cardiac surgery with cardiopulmonary bypass in patients with normal preoperative serum creatinine and normal estimated glomerular filtration rate

OBJECTIVE

Acute kidney injury is a serious complication after cardiac surgery. Although it resolves in most cases, a significant portion of patients persistently have raised creatinine values at hospital discharge. These patients are at greater risk for developing chronic kidney disease and mortality. Therefore, the present study aimed to ascertain risk factors of persistent acute kidney injury after cardiac surgery in patients with normal preoperative renal function.

DESIGN

Prospective cohort study.

SETTING

Tertiary heart centers.

PARTICIPANTS

2,181 adult cardiac surgical patients, predominantly Asian.

INTERVENTIONS

Cardiac surgery between August 2008 and July 2012.

MEASUREMENTS AND MAIN RESULTS

The incidence of acute kidney injury, as defined by the Acute Kidney Injury Network stage 1 criteria, was 21.7%. At discharge, 10.5% of these patients had persistent kidney injury, which was defined as a ≥ 26.4 μmol/L (≥ 0.3 mg/dL) difference between preoperative and discharge creatinine levels and/or a 50% rise in serum creatinine. These patients were more likely to be aged ≥ 70 years (relative risk = 2.232, 95% confidence interval = 1.326-3.757, p = 0.003), have a higher peak postoperative creatinine value within 48 hours (relative risk = 1.007, 95% confidence interval = 1.004-1.010, p<0.001), and have lower hemoglobin on intensive care unit arrival (relative risk = 0.759, 95% confidence interval = 0.577-0.998, p = 0.048).

CONCLUSIONS

Age ≥ 70 years, higher peak postoperative creatinine within 48 hours, and lower hemoglobin on intensive care unit arrival are associated with persistent acute kidney injury. Strategies to improve hemoglobin on intensive care unit arrival potentially can reduce persistent acute kidney injury. The authors recommend that patients aged ≥ 70 years undergo further renal evaluation for better risk stratification.

Hemoglobin Level to Facilitate Off-Pump Coronary Artery Bypass without Transfusion

BACKGROUND

Conservation of blood during cardiac surgery is important because of the shortage of donor blood, risks associated with transfusion, and the costs of allogeneic blood products. This retrospective study explored the feasibility of off-pump coronary artery bypass (OPCAB) without transfusion.

METHODS

One hundred and two consecutive patients underwent OPCAB from January 2007 to June 2012 at Hallym University Sacred Heart Hospital. Excluding 10 chronic renal failures patients, 102 patients were enrolled. Their characteristics, clinical data, and laboratory data were analyzed. We investigated the success rate of OPCAB without transfusion according to pre-operative hemoglobin (Hb), and the cutoff point of the Hb level and the risk factors for transfusion. We implemented multidisciplinary blood-saving protocols.

RESULTS

The overall operative mortality and the success rate of OPCAB without transfusion were 2.9% (3/102) and 73.5% (75/102). The success rates in patients with Hb<11, 11 <Hb<14, and 14<Hb were 35.0%, 79.2%, and 89.7% (p=0.01), respectively. The risk factors for transfusion are age>70 years, diagnosis of acute myocardial infarction, preoperative Hb and creatinine levels, and operation time. The events precipitating the need for transfusion were low Hb level in 9 patients and hypotension or excessive bleeding in 18 patients.

CONCLUSION

The preoperative Hb level of >11 facilitates OPCAB without transfusion. These results suggest that transfusion-free OPCAB can be performed by modifying the risk factors and correctable causes of transfusion and improving various blood salvage methods.