KDIGO Clinical Practice Guideline for Acute Kidney Injury
On-pump vs. off-pump coronary artery bypass surgery: Recommendations and Rationale

Chapter 3.9: Other methods of prevention of AKI in the critically ill

On-pump vs. Off-pump coronary artery bypass Surgery

The type of cardiac surgery is important in the discussion on risk for kidney problems associated with this surgery. Valvular procedures or aorta surgery are associated with a higher risk. One of the most controversial risk factors is on-pump vs. off-pump coronary artery bypass surgery. Off-pump coronary artery bypass obviously removes the bypass circuit but can be associated with greater hemodynamic instability secondary to ventricular compression as the heart is manipulated to access the coronary arteries.³⁵⁶ It is possible, with standard operative techniques, to perform coronary artery bypass surgery (but not valve surgery) without using cardiopulmonary bypass. This technique is known as ‘‘off-pump’’ coronary artery bypass surgery.

It has been hypothesized that preservation of physiologic renal perfusion by avoidance of cardiopulmonary bypass would partially nullify the risk of AKI in patients receiving coronary artery bypass surgery. Potential benefits that have been posited for off-pump coronary artery bypass (compared to on-pump procedures) are reduced mortality, reduction of AKI risk (and in particular, acute dialysis, which is associated with a perioperative mortality of 42% in the Society of Thoracic Surgeons database), reduced risk of cerebral dysfunction (due to stroke and neurocognitive dysfunction, the latter sometimes referred to as ‘‘pump head’’), reduction in ICU stay and days in hospital, and reduction in atrial fibrillation. As in other areas covered by these guidelines only mortality, risk for RRT, and AKI risk are addressed as endpoint measures. It must, however, be remembered that the potential benefits of off-pump coronary artery bypass might be predominantly outside these areas of focus.

• 3.9.1: We suggest that off-pump coronary artery bypass graft surgery not be selected solely for the purpose of reducing perioperative AKI or need for RRT. (2C)

Rationale

As detailed in Suppl Tables 15 and 16, which summarize RCTs, the balance of the potential benefit and harms is uncertain and the quality of the evidence is weak, that offpump surgery is associated with better outcomes of the three end-points used in these guidelines: incidence of AKI, need for RRT, or mortality.

A recent good-quality RCT³⁵⁷ was performed in 2203 patients (only ~8% of patients with SCr > 1.5 mg/dl [ > 133 µmol/l]) (Suppl Table 16). There was no significant difference between off-pump and on-pump coronary artery bypass graft in the rate of the 30-day composite outcome. The rate of the 1-year composite outcome was higher for off-pump than for on-pump coronary artery bypass graft. Follow-up angiograms in the majority of the patients revealed that the overall rate of graft patency was lower in the off-pump group than in the on-pump group (82.6% vs. 87.8%, P <0.01).

A comprehensive meta-analysis including RCTs, and abstracts from the proceedings of scientific meetings through February 2010, was recently published.³⁵⁸ AKI was defined by a mixture of criteria, including biochemical parameter, urine output, and dialysis requirement. Mortality was evaluated among the studies that reported kidney-related outcomes. This analysis compared off-pump with the more traditional on-pump technique. Off-pump coronary artery bypass graft was associated with a statistically significant 40% lower odds of postoperative AKI and a nonsignificant 33% lower odds for dialysis requirement. Within the selected trials, off-pump coronary artery bypass graft surgery was not associated with a significant decrease in mortality. It is apparent from this meta-analysis that the trials were clinically heterogeneous, particularly in regards to their definitions of kidney outcomes, and mostly were of poor to fair quality (based on the Jadad score). The very low event rates (often 0–1 patients) make the estimates suspect and highly imprecise. There is also a question of publication bias. There are several large trials in progress that are likely to generate more definitive data. In chronic dialysis patients, there are observational US Renal Data Systems data to weakly support the use of off-pump technique (slightly lower mortality). However, with any technical advance that is introduced in certain centers, institutional familiarity with the technique, operator experience, and characteristics of the population referred to the center are likely to be important modulators of outcomes. In conclusion, based on the analysis of the RCTs and the recent meta-analysis, the Work Group found that there was not enough evidence to recommend offpump coronary artery bypass for reducing AKI or the need for RRT.