الفهرس 
Definition, Etiology and Epidemiology of PediatricOnly 14 pages are availabe for public view
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Abstract
BMI is calculated by dividing a person’s weight in kilograms by the square of height in meters. Body mass index (BMI) can be used as a measure to determine childhood overweight and obesity. For children and teens, BMI is age-and sex-specific and is often referred to as BMI-for-age. A child’s weight status is determined using an age- and sex-specific percentile for BMI rather than the BMI categories used for adults. This is because children’s body composition varies as they age and varies between boys and girls. Therefore, BMI levels among children and teens need to be expressed relative to other children of the same age and sex.
There are many studies implicating external causes such as activity level, diet, social status, education, and exposure as risk factors for obesity. There are also many studies that provide evidence for the inherited or genetic predisposition of obesity. So the possible causes of childhood obesity include: poor diet, physical inactivity and rare genetic factor,
Unlike adult, most of the children, body weight is almost constant despite huge variations in daily food intake and energy expenditure. Therefore, complex physiological systems equilibrate energy expenditure with energy intake. Energy balance is regulated by peripheral signals (hormones) that are integrated in the brain centers, including the hypothalamus, brainstem, and reward centers, which in turn modulate feeding and energy expenditure.
Some hormones reflect the long-term nutritional status of the body (including leptin, insulin, and adiponectin), whereas other circulating gut hormones act acutely to initiate or terminate a meal (such as pancreatic polypeptide, glucagon-like peptide 1 and 2, and cholecystokinin) and result in appetite stimulation or satiety.
Because the population of children coming to surgery is increasingly over-weight, it is important that pediatric anesthesiologists are aware of the spectrum of physiologic derangement that may be present. Fortunately, most children with obesity do not have all of the longstanding medical issues of their obese adult counterparts, because most do not present until later in life. However, if the children have been obese for several years, especially if they trend into the morbidly obese range, the longstanding medical issues may become evident.
For most obese children, i.v. induction is preferred and a rapid sequence induction technique may need to be considered due to increased risk of acid aspiration. However, venous access may be more difficult in this group secondary to increased s.c. fat deposits.
Most children find prolonged and repeated cannulation attempts difficult and distressing, even with distraction techniques and topical anesthesia, and may only co-operate for a short period, so the inhalation route may need to be considered. Gas induction may lead to an increased risk of airway complications.
It is safer to use a tracheal tube rather than laryngeal mask airway (LMA) in this group even for minor surgery. Correct sizing for the LMA is often difficult in the obese child, leading to inadequate seal, air in the stomach, and therefore increased aspiration risk.
Positioning of obese children presents a challenge, as with obese adults, it is important to prevent pressure necrosis during prolonged procedures. For younger obese patients, additional padding and attention to bony prominences as with all patients may be sufficient.
The dosage of medicines in children is usually calculated on a milligram per kilogram basis. Drug dosing in obese children presents a particular challenge. Dose calculation using total body weight for many of the anesthetic agents may lead to overdose and subsequent adverse physiological sequelae. Therefore, the calculation of drug dosing on ideal body weight or even lean body mass may be preferred.
Obese children pose unique dosing challenges, including the risk of both overdose and underdose. These issues are not only problematic for the anesthetic agents, but hold true for many other medications, including antibiotics and chemotherapeutic agents.
Obese children have an increased incidence of airway obstruction after operation and also require a longer duration of stay in the post-anesthesia care unit (PACU) after their procedure. In the immediate postoperative period, oxygen therapy will be required and may need to be continued once the child is on the ward. Obese children should be extubated fully awake after the return of airway reflexes to minimize the risk of airway obstruction and positioned appropriately to prevent airway obstruction in PACU. Constant observation with oxygen saturation monitoring is vital.
There have been increasing numbers of children presenting for bariatric surgery. There are ethical concerns about using surgery to treat obesity in children. The patients who are operated on tend to be at the extreme end of the obesity spectrum and may have higher BMIs and actually be heavier than the average adult patients presenting for the same procedure. There is a balance of risks to consider in these very obese children, in that a higher risk surgical procedure, such as a gastric bypass, may be preferred over a low-risk one, such as a gastric band, on the grounds of long-term efficacy.