Dr Reeha Mahajan, Dr Sunita Kumari
“Children are not small adults” is a well-known dictum. The infants and children possess significant anatomical, physiological, cognitive, and psychological differences in comparison to adults, that need to be considered. The younger the child, the more marked are the differences. As the child grows, the number of differences decrease, and residual differences tend to become less critical. Very young children, infants and newborns are more susceptible to environmental harms and other illnesses, because of their small size, immature physiology, vulnerable anatomy, and differences in the ways, their bodies metabolise the medicines. Small children have more chances of getting sick or severely injured. Their needs are diverse in different stages of life.
Some of the significant anatomical and physiological distinctions between children and adults, which are of relevance to the general public are highlighted as under:
Differences in the Airway/ Respiratory Apparatus
Children have comparatively narrower airways which increase the risk of obstruction due to swelling which may be caused by inhalational burns or respiratory infections. Also, foreign bodies such as food or small toys, mucus produced in the nasal passage by various infections, small mouth with large tongue in infants, and pressure from outside inadvertently applied on the neck may be the other causes of respiratory obstruction in children. The rib cage of children is soft, with poorly developed chest muscles, resulting in fatigue due to the reliance only on their diaphragm for bringing out the breathing movements. The ribs are oriented more horizontally in infants and young children than in older children and adults, resulting in lessening of the movements of the chest. Also, the chest wall is less rigid due to the springier rib cartilages in children. This causes retraction of chest wall during episodes of respiratory distress and decreases the volume of air taken in during each breath. But children require more oxygen per kilogram of their body weight as compared to adults. Infants are obligatory nasal breather and even partial nasal blockage increases resistance which can result in difficulty feeding and laboured breathing.
The alveoli (gas exchange units) in children are smaller in size as well as fewer in number resulting in less oxygenation of blood. Therefore, infants and small children have higher respiratory rate to achieve adequate oxygen delivery to all tissues of the body.
Deficient temperature regulation mechanisms
Small children are not as adaptable to temperature change as adults. Neonates and infants have large head size, thinner skin, and higher surface-to-mass ratio which makes them more vulnerable to rapid heat loss and consequent hypothermia. The thin skin of neonates provides poor insulation, apart from other temperature regulating mechanisms being poorly developed in them. This is especially true in premature and low birth weight babies. Even full-term newborn baby may not be able to regulate its temperature if the surrounding atmosphere is too cold.
Differences in metabolism
Higher rate of metabolism in children leads to higher waste production and therefore more fluid and nutrition requirement. The length of intestine is proportionally long and may lead to greater fluid losses in case of diarrhoea. The brain develops at a rapid rate during infancy and requires the continuous supply of oxygen and glucose. Therefore, children have more energy requirements but very less glycogen stores and as a result, children, infants and neonates develop hypoglycaemia and muscle fatigue extremely rapidly. There is need for frequent feeds for neonates and young children. The level of development of different organs determines the patterns of disease that can occur in childhood and influence drug treatment and responses to them. There is an increase in oxygen consumption due to a higher respiratory rate, driven by a higher metabolic rate. The increased respiratory rate also contributes to increased water loss from the lungs.
Cranial and Neurological differences
Young children have a higher centre of gravity, due to larger heads in relation to body size. This makes children more susceptible to head injuries. The risk of falls is increased due to developing motor function. Diffuse brain injury and even brain haemorrhage with head trauma is more common in children because of thinner cranial bones. The anterior fontanelle closes at the age of 12-18 months and posterior fontanelle closes at the age of 2-3 months. The anatomy of the central nervous system undergoes significant changes in children, including rapid development of cerebral metabolism and changes in cerebral blood flow.
Cardiovascular differences
Children are vulnerable to fluid loss due to evaporation from their large body surface area. Therefore, to maintain an adequate circulating fluid volume and blood pressure, they require greater amounts of fluids. Their heart is large in relation to body size and has less pumping efficiency but the metabolic demand is high. Consequently, the workload on the heart is increased. During conditions of dehydration and blood loss, only small volume loss can have greater effects in children.
Small volume of blood loss is highly significant in neonates and small children. For example, in an infant weighing 5 kg, a 100ml of blood loss represents the loss of about 10% of its total blood volume. Also, young children have more subcutaneous tissue and smaller and narrower veins which makes vascular access further difficult in them. Therefore, early action is required.
Gastrointestinal differences:
Nutritious diet is important for the growth of infants and young children. Frequent feeds are required for neonates and young children as they rely on parents and care givers to meet the requirements for nutrition and fluid requirements. Moreover, when the child is sick, it becomes especially difficult for the care givers to meet the increased demands of nutrition and fluid. The lower oesophageal sphincter tone is immature until the age of one month and in some cases may not develop until the age of one year. This can result in spewing of feeds.
Immature Kidney and Liver functions. Due to the age-related differences in the liver and kidneys, there is inadequate detoxification and slow excretion of drugs in children, making them more vulnerable to their toxic effects. We need to exercise caution while giving medicine to them. Immature tubular function of kidneys results in decreased urine concentration leading to loss of salt and water. The normal urine output in small children and infants is around 1-2ml/kg/hr, while in adolescents, the value is 0.5-1ml/kg/hr.
Pulled elbow is another very common phenomenon in children which leads to injury of elbow region, resulting from fall and swinging of children while holding their hands. There is no obvious swelling or deformity but the child avoids moving the affected arm and holds it close to its body. The practice of swinging children while holding their hands should be avoided.
Susceptibility to Trauma and Injuries
The greatest contributor of childhood mortality is trauma. Naughtiness of children combined with changing levels of maturity expose them to higher risk of trauma than adults. These differences also influence the assessment as well as management of traumatic injuries in childhood. The majority of infants sustain their injuries at home. Infants are in a habit of grasping the objects and placing them in their mouth till the age of about 4 months, they start crawling around the age of 3 to 5 months and ‘cruise’ around the furniture between the age of 8 to 12 months. Mobility as well as curiosity increases further in pre-schoolers (1 to 4 years) but without any improvement in awareness of dangers or hazards making them more vulnerable to burns, falls and accidental ingestion of harmful substances. School age (5-9 years) is the phase of rapidly developing skills like climbing, swimming and other forms of playing activities. These children have more chances of accidents like sports injuries than being involved in industrial and motor vehicle injuries like adults. Older children have risk taking behaviour and consequently have more chances of assaults, intoxication, intentional self-harm and road traffic accidents. Children when involved in same type of accidents as adults suffer from different types of injuries because of their small size, vulnerable anatomy and immature physiology. Small children and infants have smaller airways which compromises their breathing ability in the event of slight swelling due to minor injuries. An injury of same magnitude in different aged children raises different concerns and may have varying consequences.
Differences in dealing with stress
During emergency situation, children invariably require help from adults as they are not fully capable of safeguarding themselves. Adolescents and older children can take their cues from elders whereas young children may cry, scream or freeze. Most of the time they are not able to explain, what is hurting or bothering them. Law states that an adult person is always required for making medical decisions for a child. In the event of any disaster mental stress can be extremely harder on children. They have very less experiences bouncing back from tough situations. Love and affection play a pivotal role in the holistic well-being of children. Physical and mental games stimulate their IQ development.
Adequate knowledge of these imperative anatomical and physiological variances can facilitate anticipation and detection of potential or incipient troubles compromising the well-being of kids.
(Dr Reeha Mahajan, is Associate Professor, Department of Anatomy & Dr Sunita Kumari, is Assistant Professor, Department of Physiology, AIIMS Jammu)
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