Backgrounds: Despite its importance, there has been no study fully elucidating the direct impact of isoflurane on intraoperative left ventricular (LV) systolic performance during cardiac surgery. To evaluate LV systolic long-axis performance, peak systolic tissue Doppler velocities of the lateralmitral annulus (S’) has beenmeasured. We hypothesized that incremental isoflurane dosagewould dose-dependently reduce S' in cardiac surgery patients.
Methods: In 25 cardiac surgery patientswith remifentanil dose 1.0 μg/kg/min, we determined intraop S' values of the lateralmitral annulus at 10min exposure to isoflurane 1.0, 1.5, and 2.0MAC (T1, T2, and T3) by using TEE (Fig. 1).
Results: Four patientswere excluded due to AF and IHD, and 1was due to improper TDI alignment. TEE recorded data of 20 patientswere finally analyzed. In Bland- Altman analysis, themean of differences between the 1st and 2ndmeasured valueswere not significantly different from0 in all comparisons. Themean agreements (95% LOA) for S', e' and a'were 0.088 (-1.56–1.72), 0.047 (-2.98–3.07) and 0.089 (-1.36–1.54), respectively. Between the 1st and 2ndmeasured values, correlation coefficient were 0.743 for S', 0.736 for e' and 0.630 for a' (all p<0.001). As displayed in Table 1 and 2,mean values of S'were dose-dependently reduced at all increments of isoflurane dosage at T1 vs. T2, T2 vs. T3, and T1 vs. T3: F(3, 17) =79.598, p < 0.001:Wilk’s lamda=0.066, as described in Table 2 and Fig. 3;mean differences were - 0.96 (95% confidence interval, CI -1.63−-0.32) cm/s, - 2.09 (95%CI -3.08− -1.09) cm/s and -1.11 (95%CI -1.66 −-0.57) cm/s, respectively (Fig. 2). Mean values of a' were significantly reduced at T1 vs. T3 and T2 vs. T3: mean differences were -1.94 (95%CI -3.13− -0.75) cm/s and -1.07 (95%CI -1.73 − -0.41) cm/s respectively. LVEF was reduced at T1 vs. T3:mean difference was - 4.45 (95% CI -7.52−-1.38) %. DT was significantly reduced at T1 vs. T3:mean difference was -23.8 (95%CI -40.5−-7.1) ms. The serial data of e', E, A, and E/e' at T1, T2, and T3 showed no significant changes. BIS values
were significantly reduced at T1 vs. T2 and T1 vs. T3. Phenylephrine infusion rateswere dose-dependently increased at T1 vs. T2, T1 vs. T3 and T2 vs. T3. BPswere reduced at T1 vs. T3 and T1 vs.T3:mean differences were -3.70 (95%CI -6.33− -1.07)mmHg and -5.10 (95%CI -8.13 − -2.07)mmHg, respectively. The serial data of theHR, CVP, CI and SVRI showed no significant changes.
Conclusions: Administering isoflurane appears to dose-dependently reduce S' indicating LV systolic longaxis performance in patients undergoing cardiac surgery. The direction of future researchmay include investigating the clinical relevancy of these findings.
References
1. J AmSocEchocardiogr 2013;26: 727–35
2. J AmSocEchocardiogr 1998;11: 442–9

Effects of isoflurane increments on intraoperative left ventricular systolic long-axis performance during remifentanil-based isoflurane-supplemented anesthesia for cardiac surgery: a prospective observational study