Preoperative IABP in high risk patients undergoing CABG.

A recent international consensus conference on the reduction in mortality in cardiac anesthesia and intensive care included intraoperative aortic balloon pump among the ancillary (i.e. non-surgical) drugs/techniques/strategies that might influence survival rates in patients undergoing cardiac surgery. The consensus conferences state that "Pre-operative intraoperative aortic balloon pump might reduce 30-day mortality in elective high risk patients undergoing coronary artery bypass surgery unless specifically contraindicated". The authors of this "expert opinion" presents their insights into the use of the preoperative intraoperative aortic balloon pump and conclude that based on available limited randomized controlled trials and clinical experience preoperative intraoperative aortic balloon pump saves lives in unstable patients.

The authors of the recent international consensus conference on the reduction in mortality in cardiac anesthesia and intensive care [1, 2] should be applauded for their efforts to apply the evidence base for our practice in this manner.

We have several insights into the use of the preoperative intraoperative aortic balloon pump (IABP) in coronary artery bypass surgery (CABG), acquired during the preparation of our meta-analyss [3] and of its recent update [4] which we would like to share:

a) the randomised controlled trials in this area are limited. Principally, the trials come from a single institution, and the same Principle Investigator, over a short period of time;

b) the trials include a high proportion of high risk unstable patients. Risk stratification in these studies is poor and operative mortality is much higher than would be expected by today’s standards;

c) a high proportion of the patients in the control arm crossed over into the treatment arm due to post operative instability.

The issue that had to be addressed in analysing this data was how many patients were truly elective and admitted from home, versus how many were in-house urgent patients with unstable angina and or heart failure. This matters because one may argue that the latter group is receiving “treatment” with the preoperative IABP rather than it acting as a “prophylactic” intervention. These are two distinct group of patients. Without doubt and any cardiac surgeon will recognise, we do not need a randomized controlled trial (RCT) to tells us deployment of IABP in unstable patients improves outcome. This is common and consistent in our experience. We don’t need an RCT to tell us a parachute works! The question we were interested in was whether a preoperative IABP in any specific sub-groups of elective patients is efficacious. We attempted to contact the authors of these studies to acquire Individual Patient Data (IPD) to perform an IPD meta-analysis, however this was not fruitful. The answer to this question remains unclear. From clinical experience, we conclude that it is difficult to perceive any elective patientthat might benefit from this intervention.

Our conclusion remains, based on available limited RCTs and clinical experience: preoperative IABP saves lives in unstable patients.