Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5910_Библиотеки_им_академика_М_И_Перельмана

The perinatal period is the most complicated age-group with numerous subcategories and vari­ations in methods used for categorization. The developmental and drug disposition differences are commonly related to either gestational age (GA)at birth or birth weight in combination with postnatal age (PNA). Gestational age (GA) is dened as the number of weeks from the rst day of the last menstrual cycle of the mother, with the viable age for survival of a newborn being approximately 22–23weeks or higher of gesta­tion at birth [6]. This is a more practical method compared to determining postconceptional age, which would be the age from the time of concep­tion, a date often unknown. A GA of at least 37weeks is considered full-term for a newborn. Postnatal age (PNA) refers to the age since birth. While GAmay not be reliable in some patients or as applicable to those with in utero development issues, other well-accepted terminologies associ­ated with neonatal physiology are based on the birth weight, with low birth weight neonates being considered a weight of <2500g with addi­tional stratications below that weight as described in Table19.2 [7]. It has been shown that postmenstrual (GA at birth + PNA) or post­conceptional age is most correlated with appro­priate dosing for medications excreted from the body primarily via the kidneys, such as vancomy­cin and gentamicin [8, 9]. Thus, many medication dosing recommendations are based on this descriptor, sometimes combined with the patient’s birth weight.