Introduction
“Pediatric patients feel pain and similarly they also have awareness during anaesthesia like of adults this fact now.”
Awareness during general anesthesia is potentially an important issue for adults, infants and young children. In October of 2004, the Joint Commission on Hospital Accreditation (JCAHO) issued a sentinel alert regarding anesthesia awareness (Issue 32, October 6, 2004). For the past number of months, the ASA Task Force has been holding meetings to craft a consensus statement regarding the need (if any) of monitoring awareness during anesthesia. Frequently, these types of consensus statements do not adequately address the needs of children. Because of concerns regarding the pediatric aged patient, the preverbal status of young children, an insufficient amount of peer-reviewed scientific and medical literature regarding pediatric awareness during anesthesia, and the reliability of awareness monitors (regardless of design or manufacturer) to predict or reduce the incidence of awareness in children.1 Adults who experience intra-operative awareness can develop disturbing long-lasting after-effects, such as daytime anxiety, sleep disturbances, nightmares, flashbacks and, in the worst case, a post-traumatic stress disorder (PTSD). It is unknown whether intra-operative awareness has a similar psychological impact in children. The results of the one present study suggest that children suffer less psychological sequelae than adults following intra-operative awareness. This may be due to the fact that the children reported less frightening intra-operative sensations as compared with the adults, and had less understanding of the anaesthesia procedure, and this may have influenced their appraisal of their awareness and protected them from the full impact of this potentially traumatic experience.2
Awareness during anesthesia
Awareness during anesthesia has become an important concern for both patients and physicians. Unintentional awareness during general anesthesia occurs when a patient becomes cognizant of some or all the events during surgery and has direct recall of these events. For purposes of discussion, awareness will be used in the context of the patient’s being able to recall the events. That is, the ability to have a memory of such events. Traditional clinical monitors such as at rest blood pressure during anesthesia, the use of benzodiazepines and the use of end-tidal gas monitoring are not necessarily useful in preventing awareness. In addition, awareness is not always reported immediately after the surgery. Thirty-five to 50% of cases are reported during delayed interviews (one week to one month later).1
In adults, higher incidences of awareness have been reported in patients undergoing Cesarean section, cardiac surgery or treatment for trauma. Awareness under anesthesia in children is even more difficult to quantify. The vivid imaginations of children, the difficulty in separating fantasy from reality, the ability to extract information without being suggestive, make quantification of awareness in children difficult. There are no published case reports of awareness in children and few published studies. In 1973, McKire reported an incidence of 5% but some of the patients were only anesthetized with nitrous oxide. More recently, Davidson, in a study involving 86 children, determined the incidence of awareness in children 5 to 12 years of age to be 0.8%. This is a 4- to 8-fold increase reported in adults. Is there something different in children that predispose them to awareness? At equivalent MAC concentrations of sevoflurane and desflurane, BIS and entropy measurements are greater in children. Are children more likely to retain information during relatively deeper levels of anesthesia? In addition, in children can one extract information regarding intraoperative awareness without influencing the results? 3

Recent review on awareness during surgical procedures in pediatric patients
Intraoperative awareness refers to a patient’s explicit recall of events during a procedure performed under general anaesthesia. Awareness is well described in adults, with an incidence in the order of 0.1–0.2% for low-risk surgical procedures. 1 ,2 Being conscious during surgery is a traumatic event that may result in developing chronic posttraumatic stress disorder.3  Until recently, the incidence and aetiology of awareness in children had not been studied extensively. Two cohort studies in Australia and Switzerland in 864 and 410 children, respectively, reported an incidence of awareness of around 1%, which is considerably higher than in adults.4, 5
Demonstrating a 0.6% incidence of intraoperative awareness in children, our study confirms recent reported incidences from other countries. The incidence in children appears to be higher than that reported in adults (0.1–0.2%).6 There are several similarities between our data and recent peadiatric studies.4, 5 First, the incidences of awareness are comparable. Secondly, auditory and tactile sensations were most frequently recalled, more than pain, anxiety, and paralysis. Thirdly, in general, awareness was not experienced as stressful. The results from our study therefore add to the validity of the previously reported findings. Intraoperative awareness during paediatric anaesthesia appears to be a complication that occurs at an estimated incidence of around 1%, irrespective of geographic location, institution, or anaesthetic practices.
Alternatively, applying the criteria used by Lopez and colleagues 2 (unanimous coding of ‘awareness’ or two adjudicators coding ‘awareness’ and the third ‘possible awareness’) would have resulted in a 1.2% incidence (11 out of 928 children). The peadiatric studies which have assessed awareness vary in number of patients, number and type of interviews, and the definition of awareness . Davidson and colleagues administered a structured postoperative interview to 864 children aged 5–12 years within 24 h, and at 3 and 30 days after surgery. Cases were classified as awareness when all four adjudicators agreed on this. Thus, seven cases were classified as awareness, giving an incidence of 0.8%.3 Lopez and colleagues administered two interviews adapted to children’s cognitive abilities in 410 patients aged 6–16 yrs, respectively, within 24 h and at 1 month after surgery. Awareness was defined as the coding of ‘awareness’ by three adjudicators or when two adjudicators coded them as ‘awareness’ and the third adjudicator as ‘possible awareness’. This resulted in an incidence of awareness of 1.2%.6 Older studies have reported incidences between 0% and 5%.
Several possible risk factors for awareness have been suggested. Studies in adults pointed at neuromuscular blocking agents as a risk factor. In an editorial, Davis suggested that the use of induction rooms may increase the incidence of awareness in children because administration of anaesthetics is discontinued during transfer to the operation theatre. In adult studies, too, the use of induction rooms does not seem to influence the incidence of awareness. The children in our study were mostly ASA I or II patients undergoing elective surgery. As previous research in adults has demonstrated an increased risk of awareness in severely ill patients (ASA physical status III–V) undergoing major surgery, this may have led to underestimation of the incidence.7
The following are the issues in pediatric patients: 1
(1) Awareness during anesthesia in children with regard to incidence and impact
(2) The developmental aspects of the EEG and the anesthetic effects on the adult and pediatric EEG
(3) The limitations of cerebral monitoring devices
(4) The relationships of integrating EEG data with drug pharmacology
Structured awareness screening interview used in different studies;
Interview on day 1
1 Were you upset, worried, or frightened about your operation?
2 How upset, worried, or frightened were you?
3 What was the last thing you remember before the operation?
4 How did the doctor make you go to sleep?
5 What is the first thing you remember after your operation?
6 After you fell asleep, do you remember anything that happened during the operation?
7 Did you have any dreams during the operation?
8 Did you feel anything during the operation?
9 Did you hear anything during the operation?
10 Did you have pain after the operation?
11 Did you have an operation before?
12 Did you hear or feel anything during previous operations?

Interview on days 3–7 and day 30
1 What was the last thing you remember before the operation?
2 How did the doctor make you go to sleep?
3 What is the next thing you remember after your operation?
4 Did you have any dreams during the operation?
5 Did you feel anything during the operation?
6 Did you hear anything during the operation?

Additional questions for suspected awareness cases
1 Did you notice sounds?
2 Did you notice tactile sensations?
3 Did you have visual perceptions?
4 Did you feel pain?
5 Were you paralysed?
6 Did you feel something in your mouth or throat?
7 What went through your mind?
8 Did you believe you were dreaming?
9 How long did it last?
10 Did you try to alert anyone?
11 Did you inform your parents or the doctor?

Integrating EEG monitoring devices with drug pharmacology1
Devices that monitor anesthetic effect generally process, acquired evoked responses from auditory stimuli or process brain electrical activity. The auditory evoked potentials are electrical responses of the brainstem, auditory pathways and auditory cortex that result from auditory stimulation. Anesthetic agents affect the brainstem responses very little, while early cortical responses, also known as mid-latency responses, have an increase in latency and a decrease in amplitude as a result of increasing concentrations of anesthetic agents. Although descriptive reports of the use of auditory evoked responses have been published, there are no randomized control trials that have evaluated its role on intraoperative awareness.
Numerous commercial monitors that process spontaneous EEG and electromyographic activity are available. Entropy monitor, narcotrend monitor, patient state analyzer, SNAP index, Danameter, cerebral state monitor, process the EEG data and compute a value that is reflective of the patient’s hypnotic state. Although there are many publications regarding their clinical use, there are no randomized control trials with these services that have evaluated intraoperative awareness.
The BIS monitor also uses EEG data and by combining in a proprietary algorithm involving burst suppression data and frequency domain data, complex electrical patterns are transformed into a single value that is reflective of the patient’s hypnotic state. A large number of BIS studies have been published that correlate age, anesthetic agents, and drug concentration to the BIS value. In addition, RCT have also been published regarding the use of BIS and intraoperative awareness.
Although BIS has been shown to reduce the incidence of awareness in adults and decrease the anesthetic requirements in patients, nonetheless, issues involving specific drug effect and patient variability create significant limitations in its use. Because drug use alters the brain’s state, different drugs effect BIS differently in spite of the fact that the patient’s level of sedation may be the same. Increasing amounts of ketamine, for example, will increase a patient’s level of sedation. However, the BIS values will remain unchanged. Nitrous oxide, an anesthetic agent frequently administered to decrease the anesthetic requirements of patient inhaled anesthetic agents appears to have little effect on BIS. Opioids decrease BIS but not in a predictable dose dependent way. Inhaled anesthetic agents have a dose dependent effect on BIS but the interpatient variability is large. BIS values of 50 have been observed with sevoflurane concentrations ranging from 0.5% to 2.5%. Large variability has also been associated with propofol. BIS values of 50 and less have been observed with plasma concentrations that range from 1 to 10 mcg/ml. Neuromuscular blocking agents, when administered without any hypnotic agent or anesthetic to awake volunteers profoundly affected the BIS. Messier and colleagues demonstrated that in awake volunteers administered only alcuronium and succinylcholine, the BIS resembled a well-sedated patient.

The irony of EEG monitoring for awareness is that the monitor is sensing changes in the cortex. Sleep is a non-waking state with preserved brainstem arousability, and coma is a non-waking state with absent brainstem arousability. In patients with impaired cerebral reactivity, distortion and disappearance of normal EEG patterns; along with the appearance of abnormal patterns occur. In addition, slowing of posterior alpha, from upper alpha to lower alpha frequencies, into the theta range occurs. Also, in these patients frontal beta slows from the upper range to the lower range, and even into the alpha range. What if awareness is a subcortical function? Classic endpoints for awareness generally assess patient movement, performance and memory tests. Advances in neuroimaging suggest that the thalamus, a subcortical structure, may be involved in awareness during anesthesia. If sleep is a non-waking state with preserved brainstem arousability, and coma is a non-waking state with absent brainstem arousability, may be the future monitoring in anesthesia will access both cortical and subcortical activity.
For children, the issue of determining intraoperative awareness is compounded by the issues of when and how one extracts such information. It is well documented that most cases of awareness are discovered days to weeks after the event. For children, behavior changes are frequent following surgery. Is postoperative behavioral change a function of intraoperative awareness? As one tries to determine whether awareness occurs, how frequent is it, and what the psychosocial implications for the patient may be, at present, in children we are left with black box solutions. The present day monitors are imprecise, and maybe the best that can be achieved is to describe awareness as a phenomenon and determine if certain types of interventions (monitors) can reduce the incidence without really knowing how the true mechanism is involved.
Conclusion
Recent studies have confirmed the higher incidence of intraoperative awareness in children than in adults while using modern anaesthetic techniques. Neither the old nor the recent studies clearly identify predictive risk factors. Children describe the same perceptions as adults during their awareness period (mainly auditory and tactile sensations), but with fewer negative thoughts. Moreover, they do not seem to be affected by this experience, as they do not have long-term psychological sequelae. The prevention of intraoperative awareness in children is the same as in adults, the major factor being awareness of this complication.
References;

1. Peter J. Davis. Awareness: Where do we stand? Presented at SPA Annual Meeting, 2006

1. Lopez U, Habre W, Van der Linden M, Iselin-Chaves IA.Intra-operative awareness in children and post-traumatic stress disorder. Anaesthesia. 2008 ;63(5):474-81.

1. Davidson AJ, Huang GH, Czarnecki C, Gibson MA, Stewart SA, Jamsen K, Stargatt R. Awareness during anesthesia in children: a prospective cohort study. Anesth Analg. 2005 ;100(3):653-61, table of contents.

1. Malviya S, Galinkin JL, Bannister CF, Burke C, Zuk J, Popenhagen M, Brown S, Voepel-Lewis T. The incidence of intraoperative awareness in children: childhood awareness and recall evaluation. Anesth Analg. 2009 ;109(5):1421-7.

1. Iselin-Chaves I, Lopez U, Habre W.Intraoperative awareness in children: myth or reality? Curr Opin Anaesthesiol. 2006 ;19(3):309-14.

1. Lopez U, Iselin-Chavez I, Habre W. Incidence of awareness during general anaesthesia in children. Br J Anaesth. 2004; 93(3):490P-491P.

1. H. J. Blusse´ van Oud-Alblas, M. van Dijk, C. Liu, D. Tibboel, J. Klein and F. Weber. Intraoperative awareness during paediatric anaesthesia. British Journal of Anaesthesia 2009. 102 (1): 104–10