ABSTRACT
This chapter looks at clinical biochemistry at the extremes of age, that is, in neonates and the elderly. The most significant advances in medical care has been the survival rate of very small preterm infants, which has increased because of improved specialized medical and nursing techniques for treating the neonate. The chapter examines these infants can experience a number of abnormal biochemical conditions. Diseases occurring during the neonatal period can be divided into two main groups: those of infants born before term, in whom immaturity contributes to the severity of the disease, and those of full-term infants. The plasma urea concentration is low in newborn infants compared with that in adults, despite the relatively low glomerular filtration rate; the high anabolic rate results in more nitrogen being incorporated into protein rather than into urea than in adults. Renal function in newborn infants can maintain basic homeostasis but may not be able to respond adequately to illness or other stresses.
