الفهرس 
Introduction and aim of workOnly 14 pages are availabe for public view
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Abstract
The formation of explicit and implicit memories during anesthesia and surgery (awareness) is considered potentially damaging to the human psyche. Explicit memory may be recalled spontaneously or may be provoked by postoperative events or questioning. In contrast implicit memory may not be consciously recalled but may affect behavior or performance at a later time (298).
Awareness requires explicit memory and as explained in definition of awareness but children begin to develop some form of explicit memory at approximately 3 years of age (299). Therefore if we consider only explicit recall there is little relevance in discussing awareness in infants and toddlers. However younger children could still form implicit memory or have periods of consciousness during anesthesia. There is very little research or discussion examining the effect of consciousness or implicit memory formation during anesthesia in infants. This does not mean that infants do not need anesthesia (300).
On the contrary, there is good evidence that they do. Infants form implicit memory for painful experiences and there is increasing evidence that untreated pain is detrimental to infants like persisting changes in behavior and worse clinical outcomes (301,302).
The anatomic and the physiologic aspect of the awareness in pediatric anesthesia can be summarized in the flowing points:
1) The thalamus has been described as the gate to consciousness and may be one of the main targets of anesthesia (120).
2) On the other hand anesthetics may induce unconsciousness by cortical disintegration (122).
3) In the anesthetized brain potentials become more regular and less chaotic and this may reflect reduced information capacity and loss of connectivity.
4) Consciousness requires integration of both thalamic and cortical functions.
5) Anesthetic effects which prevent thalamocortical or corticothalamic feedback may induce unconsciousness which seems mainly induced by cortical disintegration and thalamic effects of anesthetics are important to prevent arousal (303).
6) The main targets for the amnesic effects of the brain are the entorhinal cortex, amygdala and hippocampus and all of these areas are suppressed by anesthetics.
7) As long as amnesic effects cannot reliably be quantified general anesthesia should be focused on unconsciousness rather than amnesia (136).
A relatively idea is that consciousness is not an all or none phenomenon but it develops as a continuum throughout fetal and infant life. However even with this argument there is a point where it must start. As mentioned above implicit memory is formed earlier than explicit memory There is increasing evidence that neonates, preterm babies and perhaps even the fetus can form some types of implicit memory. The relevance of these memories is unclear though evidence is emerging that implicit memory of nociceptive stimuli may adversely influence subsequent behavior and response to similar stimuli. The information to guide us with how much anesthesia is needed to prevent these memories in toddlers, infants and neonates is not standerized (304,305).
Children’s responses to drugs have much in common with the responses in adult but the perception that anesthetic drug effects on pediatric age group differ from adult arises because the drugs have not been adequately studied in pediatric populations who have size- and age-related effects as well as different diseases (306).
There is situation in which age-related performance data changes have been described and many of these have application in anesthesia for example: MAC age-related changes of anesthetic inhalation agents. On the molecular level anesthetics may induce unconsciousness by affecting ion channels (K2P), blockade of excitatory (glutamate, acetylcholine) and neurotransmitter effects on the Inhibitory GABA receptors which may not reach maturity until 10 years of age influence the response seen after benzodiazepines in children(307).
The preoperatively consideration includes if there is a higher risk for anesthesia awareness and informs the family of the pediatric patients of the possibility of intraoperative awareness. The ASA has published guidelines recommended that stringent efforts must be made to prevent awareness (13).
Premedication with amnestic agents should be considered as the results of some studies show that the application of benzodiazepines reduces the incidence of awareness(215, 308)
There was no difference in the frequency of awareness and recall in respect to premedication according to the results of Sandin et al. study (5).This observation seems to agree with the suggestion of a minor role of benzodiazepine premedication in protection from awareness and recall during anesthesia(212, 5) .
Any firm conclusion about the effect of benzodiazepines on the frequency of awareness and recall should be drawn cautiously because the timing of the administration in relation to the operation is not standardized and the duration of surgery varied considerably.
Consultants who participated in ASA Practice advisory for intraoperative awareness strongly agree that functioning of anesthesia delivery systems (e.g., vaporizers, infusion pumps, fresh gas flow, intravenous lines) should be checked to reduce the risk of intraoperative awareness. Monitoring of the concentrations of inspired and expired gases and inhalation agents and general vigilance should eliminate cases caused by inadequate anesthetic delivery. In high risk situation, monitoring of depth of anesthesia is justified. The use of such monitoring may also be advisable in patients in whom clinical signs of light anesthesia may be masked (concurrent β-blockers,
diabetes (215, 308).
Awareness during anesthesia is common in pediatric patient than adult and well described adverse outcome that may result in serious emotional injury and post-traumatic stress disorder. A properly trained anesthetist administering anesthesia according to knowledge of pharmacology of the pediatric patients and surgical characteristics assisted by clinical signs and monitoring can minimize the risk of awareness. Measures to prevent awareness include avoidance of light anesthesia, gaining more knowledge about anesthetic requirements of patients and development of methods to detect consciousness during anesthesia should be more and more studied (188,13, 6)