Evaluation of Influencing Variables in Awakening Concentration and Concentration at Body Movements of Propofol TCI (Targeted Controlled Infusion) Targeted at the Effector Site

Overview

Age has been related to awakening propofol concentration at effector site of TCI, but not to the loss of consciousness concentration, neither to the concentration of body movements during surgery, that can be interpreted as a sign of light anesthesia and lead to awareness. This study aims to determinate the incidence and the propofol TCI concentration at the effector site, in patients undergoing general anaesthesia without NBDs, of any patients body movements, defined as any spontaneous movements (but no reflex movements) during surgery.

Target-Controlled-Infusion (TCI), estimating the effect-size concentration (Ce) of propofol and its elimination time with a computerized system, provides the anaesthesiologist useful information to guide anaesthesia. Although the correlation between propofol at the effector site at loss of consciousness (Ce LOC) and age is still debated with contrasting results, the correlation between propofol at the effector site at return of consciousness (Ce ROC) and age is well established, and some authors suggested that, due also for age-related changes in both pharmacokinetics and pharmacodynamics of propofol, its dosage should be reduced in elderly patients. Lowering propofol dosage however, can lead to an higher incidence of awareness during general anaesthesia, even if anaesthesia management is guided by consciousness monitors. Awareness during anaesthesia has recently been defined not as a binary phenomenon, but as a graded spectra of states and, during general anaesthesia without using neuromuscular blocking drugs (NBDs), body movement on the operating table can be taken as an indication of increasing probability of consciousness or 'light' anaesthesia. Hence, this study aims to evaluate the impact of age on the concentration at the effector site of propofol-remifentanil anaesthesia administered with TCI pump and without NBDs. Concnetration at the effector site of Propofol at the return of consciousness (CeP ROC) and at any clinical sign of superficialization such as body movements (CeP BM) will be considered.

Conditions