Background: We analyzed the changes in the peak systolic velocity (S′) in tissue Doppler imaging (TDI) of mitral annular motion during the increments of propofol’s concentration for target-controlled infusion (TCI) on cardiac contractile performance in patients undergoing cardiac surgery under remifentanil-propofol anesthesia. We also analyzed the changes of S′ and BIS values to determine propofol’s dose-dependent probability for producing decline of contractile performance and inadvertently deep hypnosis, as secondary measures.
Methods: Anesthesia was induced and maintained with target-controlled infusions of propofol and remifentanil in cardiac surgery patients with LV EF >50% (n=33). In a fixed remifentanil’s plasma concentration (20 ng/ml), propofol’s effect-site concentration(Ce1) was adjusted to maintain BIS 40-60.  TDI tracing of the lateral mitral annulus were recorded by TEE at Ce1 and the recordings were repeated at two incremental Ces; doubled and tripled Ce1(Ce2 and Ce3), respectively. S′ at Ce1, Ce2 and Ce3 were determined as off-line analyses. During propofol increments, phenylephrine infusion rates were adjusted to maintain BP within 80-120 % of pre-induction values. By using non-linear mixed effect modeling (NONMEM), propofol’s Ces with 50% probability for reducing S' at Ce1 by≥10% and ≥20% (Ce50-10% and Ce50-20%, respectively) were determined.
Results: Mean differences of S' in Ce1 vs. Ce2, Ce2 vs. Ce3, and Ce1 vs. Ce3 were -1.1(95%CI -1.7−-0.4), -1.1(95%CI -1.8−-0.5), and -2.2 (95% CI -2.9−-1.6)cm/s, respectively(all p<0.001). Phenylephrine dosage and BIS values significantly increased and reduced during propofol increments (p<0.001 in both). Propofol’s Ce1, Ce2 and Ce 3 were 0.8, 1.6 and 2.4μg/ml, respectively. Ce50-10% and Ce50-20% in NONMEM were 1.4 μg/ml and 2.1μg/ml, respectively.
Conclusions: While  Ce increments dose-dependently reduce S' in cardiac surgery patients. During TCI propfol-remifentanil anesthesia using remifentanil 20 ng/ml, propofol Ce for BIS 40-60 was  0.8 μg/ml. Ces for reducing S' at Ce 0.8 μg/ml, by 10% and 20%, with 50% probability were 1.4 μg/ml and 2.1μg/ml, respectively.
References
1. Claeys MA, et al. Br J Anaesth 1988; 60: 3-9
2. Bilotta F, et al. Anaesthesia 2001; 56: 266-71
3. Skubas N. Anesth Analg 2009; 108: 48-66

The analysis the effect site concentration of propofol affecting the left ventricular long-axis systolic performance: mitral annular tissue Doppler study