Isoflurane's Effect on Intraoperative Systolic Left Ventricular Performance in Cardiac Valve Surgery Patients

Abstract

Background: Isoflurane, a common anesthetic for cardiac surgery, reduced myocardial contractility in many experimental studies, few studies have determined isoflurane's direct impact on the left ventricular (LV) contractile function during cardiac surgery. We determined whether isoflurane dose-dependently reduces the peak systolic velocity of the lateral mitral annulus in tissue Doppler imaging (S') in patients undergoing cardiac surgery.

Methods: During isoflurane-supplemented remifentanil-based anesthesia for patients undergoing cardiac surgery with preoperative LV ejection fraction greater than 50% (n = 20), we analyzed the changes of S' at each isoflurane dose increment (1.0, 1.5, and 2.0 minimum alveolar concentration [MAC]: T1, T2, and T3, respectively) with a fixed remifentanil dosage (1.0 μg/min/kg) by using transesophageal echocardiography.

Results: Mean S' values (95% confidence interval [CI]) at T1, T2, and T3 were 10.5 (8.8-12.2), 9.5 (8.3-10.8), and 8.4 (7.3-9.5) cm/s, respectively (P < 0.001 in multivariate analysis of variance test). Their mean differences at T1 vs. T2, T2 vs. T3, and T1 vs. T3 were -1.0 (-1.6, -0.3), -1.1 (-1.7, -0.6), and -2.1 (-3.1, -1.1) cm/s, respectively. Phenylephrine infusion rates were significantly increased (0.26, 0.22, and 0.47 μg/kg/min at T1, T2, and T3, respectively, P < 0.001).

Conclusion: Isoflurane increments (1.0-2.0 MAC) dose-dependently reduced LV systolic long-axis performance during cardiac surgeries with a preserved preoperative systolic function.

Trial registration: ClinicalTrials.gov NCT01819012.

Keywords: Echocardiography; Heart function test; Isoflurane.

Fig. 1

Patient recruitment and analysis diagram. Twenty-one patients were recruited and one was excluded due to the failure to align Doppler beam parallel to the axis of the lateral annular motion during the entire systolic period. LVEF = left ventricular ejection fraction, TTE = transthoracic echocardiography, TEE = transesophageal echocardiography, MAC = minimum alveolar concentration, BIS = Bispectral index, MV = mitral valve, TDI = tissue Doppler imaging, BP = blood pressure, HR = heart rate, bpm = beat per minute.

Fig. 2

Correlation and agreement of the first and second measurements of TDI parameters. Measure 1: first measurements of each variable. Measure 2: second measurements of each variable. The solid line shows the mean difference and the dash lines show the LOAs (mean difference ± 1.96 standard deviations). TDI = tissue Doppler imaging, S′ = peak velocity of the lateral mitral annulus during systole, e′ = peak velocity of tissue Doppler imaging mitral annulus during early relaxation, a′ = peak velocity of mitral annular TDI during late atrial contraction, LOA = limits of agreement, T1, T2, and T3 = after 10-minute-exposure to isoflurane 1.0, 1.5, and 2.0 MAC, respectively, MAC = minimum alveolar concentration.

Fig. 3

S′, e′, a′, and BIS during the increments of isoflurane dosage. The boxes show the 25th and 75th percentiles, and horizontal lines within the box show median values. The whiskers show the lowest and highest values in the 25th percentile minus 1.5 IQR and 75th percentile plus 1.5 IQR regions, respectively. The optimal hypnosis level for general anesthesia is a BIS value between 40 and 60. S′ = peak velocity of the lateral mitral annulus during systole, e′ = peak velocity of tissue Doppler imaging mitral annulus during early relaxation, a′ = peak velocity of tissue Doppler imaging mitral annulus during late atrial contraction, BIS = Bispectral index, IQR = interquartile range, T1, T2, and T3 = after 10-minute-exposure to isoflurane 1.0, 1.5, and 2.0 MAC, respectively, MAC = minimum alveolar concentration. ^aP < 0.05 vs. T1; ^bP < 0.05 vs. T2.