Pediatric Anesthesia Intraoperative Awareness During Pediatric Anesthesia

COMMENT A long neglected area, the subject of awareness and recall under anesthesia in the pediatric population, has seen increased interest of late. This dates to the important articles by Davidson et al and Lopez et al. The incidence was found to be 0.8% in the study of Davidson et al and 1.2% in the work of Lopez et al, substantially higher than the usual quoted 0.1% to 0.2% in adult patients. Both articles used a follow-up questionnaire at specific time points to determine the incidence of awareness. This method, despite the greatest rigor of the investigators, is fraught with the possibility that what a child recalls is not actually an intraoperative event. Davidson et al followed up their work with a recent study using the Brice method. This method exposes the child to a specific intraoperative sound using headphones and then uses postoperative questioning to determine if the child can recall the sound. The method is simple and elegant, overcoming some of the inherent difficulties in assessing pediatric awareness. The investigation, however, suffered from the fact that the attending anesthesiologist knew his/her patient would later be questioned about intraoperative sounds. One also cannot ignore the possibility of a deeper level of anesthesia being unintentionally administered to the study patients. This might have accounted for the incidence of recall being zero, a sharp difference from the work of Davidson et al in 2005. The work of Blussé van Oud-Alblas et al shows an incidence of 0.6% using their most strict criteria. A more liberal definition of awareness results in an incidence of 1.5%. Their methods were also structured questionnaires given at specific time points, taking great care not to use leading or suggestive questions. There is now a growing body of evidence that the incidence of pediatric awareness and recall is higher than in adults. We are also gaining insight into the nature of awareness. Pediatric patients seem to recall tactile and auditory sensations. Interestingly, the pediatric brain may be more prone to a dreamlike state under anesthesia. In the group of children who were not deemed to have awareness, fully 9% had recall of dreaming under anesthesia. Two of 6 children with recall also reported dreaming under anesthesia. Much less often do children report pain, anxiety, and paralysis even when muscle relaxants are used. The experience seems to be regarded by children as more curious than stressful and serious psychological effects are rare. Although the nature of awareness is becoming clearer, identifiable risk factors are proving elusive. If identifiable risk factors are absent, perhaps there is a test that might reveal the likelihood of intraoperative awareness. A weakness of the study is the lack of bispectral index (BIS) monitoring. Because BIS is the only widely available monitor purporting to reduce the incidence of awareness, it would be interesting to know the BIS levels at the time points during surgery when the children reported awareness. All children who were aware had conventional general anesthesia at what seemed to be adequate levels and without other complications. Analysis of the 6 patients with awareness discerned no obvious risk factors. A higher proportion of awareness patients received muscle relaxants, but the numbers remain too small to determine a trend. The use of induction rooms has been implicated because the depth of anesthesia may lighten during transfer to the operating room, but this remains speculative and probably of little importance. A clear demonstration of the mystery of human memory, awareness, and recall is shown in an unrelated work by Blussé van Oud-Alblas, which is also the subject of commentary in this issue of Survey of Anesthesiology. In their study, they conducted wake-up tests during scoliosis surgery. Twenty patients were intentionally awakened during surgery, told to move their feet and hands, and given a color to remember. Even with such a small group, one would expect some awareness and recall, but there was none. If we cannot demonstrate awareness when we actually create it, how can we ever understand why it occurs when we are actively trying to prevent it?