To the Editor:—
There is increasing experimental evidence that volatile anesthetics may have a cardioprotective effect, either by decreasing the extent of the reperfusion injury or by a pharmacologic preconditioning effect. These findings may ultimately have an impact on the anesthetic practice for patients with ischemic heart disease. 1Recent studies in coronary surgery patients have suggested that the use of volatile anesthetic agents may result in the preservation of left ventricular function and lower troponin I levels after cardiopulmonary bypass. 2,3However, variables such as differences in cardioplegic solutions, adequacy of myocardial protection, presence of cardiopulmonary bypass, adequacy of surgical revascularization, and many others may affect the extent of perioperative myocardial ischemia and, ultimately, the success of the intervention. This results in a complex situation in which the potential beneficial effects of volatile anesthetics may depend on these determining factors.
With respect to this issue, we would like to report some of the results of the yearly quality assessment report of one of our cardiac surgical centers. Last year was significant, because this center was rebuilt to provide for the implementation of a volatile anesthetic regimen during the cardiac surgical procedures. Previously, the anesthesia machines and cardiopulmonary bypass circuits were not equipped with vaporizers. In addition, the monitoring equipment did not include an end-tidal anesthetic concentration measurement system. From January 2 to June 26, 2002 (period A), 107 patients underwent coronary artery surgery. During this period, anesthesia consisted of a combination of midazolam (0.2–0.3 mg/kg) and high-dose sufentanil (5–8 μg/kg) without the use of volatile anesthetics. From July 2 to December 31 (period B), 91 patients had coronary surgery. During this second period, anesthesia consisted of the same combination of drugs with a reduction in the dose of midazolam and sufentanil used, but with the administration of sevoflurane (0.5–2%) throughout the procedure. When the different outcome variables were analyzed at the beginning of this year, troponin T levels (measured using monoclonal antibodies immunologic assay; Elecys 2010®, Roche, Basel, Switzerland) were found to be consistently lower in the patients operated on in period B (fig. 1). The need for inotropic support for weaning from cardiopulmonary bypass was significantly lower in period B (36% of patients in period B vs. 52% in period A; P = 0.019). In addition, the incidence of low cardiac output (defined as the need for inotropic support for a cardiac index below 2.0 1 · min−1· m2) was also significantly lower in period B (19% of patients in period B vs. 35% in period A; P = 0.014). Patient characteristics, medication, and intraoperative data were similar during both time periods (table 1). The same surgical and anesthetic team performed all procedures, and the hemodynamic strategies were the same. The only difference was the introduction of sevoflurane in the anesthetic regimen, supporting a possible cardioprotective effect of this agent in the setting of coronary surgery. This observation seemed interesting because it suggested that the effects of sevoflurane observed previously, 3in a specific setting of intermittent cross-clamping with the use of the nucleoside transport inhibitor lidoflazine, were also present with a different surgical technique using continuous aortic cross-clamping and cardioprotection with cold crystalloid cardioplegia. Another interesting point was that patients undergoing valve surgery also demonstrated a difference in postoperative troponin T release between both time periods (period A [n = 18] at day 0: 1.1 ± 0.8 ng/ml, at day 1: 1.3 ± 1.0 ng/ml, at day 2: 1.1 ± 0.8 ng/ml; period B [n = 28] at day 0: 0.8 ± 0.7 ng/ml, at day 1: 0.7 ± 0.5 ng/ml, at day 2: 0.6 ± 0.3 ng/ml; difference between periods at day 1 and 2 statistically significant for P < 0.05)
Although these observations lack the power of a prospective randomized study, they suggest that the beneficial effects of a volatile anesthetic regimen on myocardial function represent a genuine phenomenon in the clinical setting of cardiac surgery. They provide additional circumstantial evidence for a potential cardioprotective effect of sevoflurane. Clinical investigations on a large patient population scale should now be undertaken to definitively elucidate this question.