**2. Delirium**

The issue of the development of POD in children is completely different. Due to the pronounced clinical picture and the absence of the need for preoperative testing, the detection of this complication is much easier compared to POCD. Moreover, according to the studies of N. Sikich and J. Lerman, AML in children in most cases proceeds in an active form with severe symptoms [8]. This distinguishes it from POD in adults, in which up to 75% are hypoactive and mixed, and therefore hidden from diagnosis, forms, which is confirmed by their detectability, which is only 40% [9].

The current definitions of POD are presented in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) [10] and the International Statistical Classification of Diseases and Related Health Problems (ICD-10) [11], according to which the definition of POD sounds like "acute emerging disorder of consciousness with impairment of the functions of attention and understanding." The timing of its occurrence is limited to 5 days of the postoperative period. Previously, delirium was perceived not as a separate syndrome, but as an inevitable symptom, necessarily accompanying a critical state. In the literature, one can find various terms regarding POD, such as critical illness encephalopathy or ICU psychosis [12, 13]. However, for several years now, the term "postoperative delirium" has been approved, and the European Society of Anesthesiologists (ESA) even released a guideline on this condition [9], so this is the term we will use. Of particular value to us is the presence in this manual of a section devoted to the peculiarities of AML in children, even though the definition of delirium in childhood is not given there. After all, neither the DSM-5 nor the ICD-10 contains the child population. Nevertheless, this was an important step in the study of delirium in children, given that there have always been difficulties in the study of delirium in the pediatric population.

The widespread and systematic introduction of protocols for screening patients for delirium in the intensive care and intensive care units made it possible to study this issue in detail in the adult population and identify its absolute relevance. High numbers of delirium prevalence were obtained, as well as many consequences of delirium for the patient and medical organizations were revealed: dementia persisting for up to 15 months after surgery and more [14], increased mortality and morbidity in the immediate and late postoperative periods, prolongation of the period of stay patient in intensive care units, the development of dependence on the ventilator and an even higher probability of infectious complications, although the mechanism of the relationship between these complications and cognitive impairments has not yet been elucidated [15, 16]. Thus, the studied characteristics of delirium in the adult population stimulated researchers to study POD in children. However, such works are still few in number, and it is very difficult to carry out them and obtain objective data. Very revealing is a study that surveyed pediatric intensive care and intensive care units around the world about whether they routinely screen for delirium? And 75% of the respondents answered that they do not use it [17]. This is due, of course, not so much to the reluctance to carry out such screening, as the difficulties in its implementation. There is always a difference in the cognitive status, psychomotor and psycho-speech development, characteristics for each age period of the child [18, 19]. We must not

## *Delirium in Children after Cardiac Surgery: Brain Resuscitation DOI: http://dx.doi.org/10.5772/intechopen.102130*

forget that many diseases significantly affect the preoperative cognitive abilities of children, as happens in children with congenital heart disease (CHD). And then their cognitive potential can be strikingly different due to the variability of cerebral perfusion and oxygenation, starting from birth [20]. This implies the need for a large number of different test systems for screening for delirium. The number of scientific works devoted to the pediatric population, especially in the last 10 years, has increased dramatically, according to how the delirium assessment scales in children appear and are validated, which are clearly insufficient [21]. In recent years, data on the epidemiology and clinical features of POD in children are only beginning to accumulate.

Based on the data that are found in the world literature, the prevalence of POD in children can be represented only in the range from 2 to 80% [22–24]. The breadth of this range can be explained by the fact that research on delirium in children is carried out in different age groups, with various pathologies and types of surgical correction, so there is no one average indicator and cannot be. Against this background, it seems interesting that a large study in 2003 with the participation of 521 children, demonstrating the frequency of occurrence of delirium in different areas of surgery [25]. So, the leading position was taken by otorhinolaryngology with an indicator of 26%. At the same time, urology and orthopedics have more modest figures—15%, and abdominal surgery—13%. Quite strange data, given the absolutely different volumes of surgical intervention in the presented surgical profiles, but the authors of the article themselves could not explain this dependence. This study did not affect young patients with CHD after their surgical correction. There are two explanations for this: firstly, surgery to correct CHD is most often carried out in conditions of artificial circulation, which immediately presupposes a large set of pathological factors, which we will discuss later. Secondly, all congenital heart diseases differ greatly in their hemodynamics and, consequently, in the level of hypoxemia and blood supply to the brain, which affects the child's cognitive abilities both before and after surgery [20]. However, there are works on a group of pediatric patients undergoing cardiac surgery. For example, a study by A. Patel et al. Deserves attention, in which patients were observed from birth to 21 years after correction of various CHD [26]. Based on its results, the frequency of POD development was revealed—49%. Interestingly, in addition to the prevalence of delirium, it also revealed an increase in the number of bed days for such patients in intensive care, which coincides with the adult population. Additionally, the risk factors for the development of POD in children after this type of surgery were also considered, but this will be discussed a little later. The only drawback of this study was that it included children with a RACHS score (scale for assessing the severity and risk of CHD correction) from 1 to 6 points. In other words, a mixed assessment was carried out for all children with a wide variety of hemodynamic and cerebral oxygenation options, which, of course, cannot but affect the results [20]. Similar data are available in another study of a cohort of patients with the same type of surgery, after which the incidence of delirium was 57% [27]. Thus, the world literature does not provide data on the assessment of children with a ranking by the types of CHD and their correction, which indicates the prospects of studying this issue.
