To the Editor:
The authors wish to thank Dr Homs and Dr González-Costello for their interest in our article. They express their doubts concerning the effect of pretreatment with beta-blockers in patients with postoperative low cardiac output syndrome (LCOS) randomized to dobutamine, supporting their arguments with the practice guidelines for the treatment of acute heart failure and the LIDO study.1-3
We consider their doubts to be logical and valid; we have discussed this point over the last 2 years, and have obtained certain conclusions to the contrary.
First, we should correct an error: of the 68 patients assigned to dobutamine, 23 had not been taking beta blockers preoperatively; that is, one third of our patient population, a number that can not be considered small.
Second, we compared the mortality of the patients randomized to levosimendan (6/69) with that of those treated with dobutamine who had not received preoperative beta-blocker therapy (7/23), and a trend toward significance was observed (P=.1), that was insufficient due to the smaller number of patients considered at that time.
With respect to possible differences in the chronotropic effect, Figure 5 of our study shows that, in contrast to the finding indicated in the letter, the group randomized to dobutamine had a slightly higher cardiac output.
Another argument that should be considered would be the initial dose of dobutamine employed (5 µg/kg body weight), which is twice as high as the initial dose we usually administer, and the rapid rate at which it was increased (every 15 minutes); after 45 minutes, the nonresponders were receiving 12.5 µg/kg.
With all due respect, both the guidelines and the LIDO study only marginally consider patients who are in the postoperative period following heart surgery. Thus, it is difficult not to evaluate situations, such as the use of cardiopulmonary bypass and its consequences, systemic inflammatory response, coagulopathy, the use of general anesthesia and positive pressure mechanical ventilation, catecholamine discharge (which partly counteracts the effect of preoperative beta-blockers), all of which make postoperative LCOS a very particular form of acute heart failure.