Keywords: pediatric circulatory system anatomy and physiology
Cardiovascular anatomical characteristics
(A) The heart weight pediatric heart compared to the weight of the adult. The neonatal heart weight of about 20 to 25 grams, accounting for 0.8% of the body weight, while adults accounted for only 0.5%. 1-2 years old up to 60 grams, the equivalent of two times of the newborn, the age of 5 to 4 times 6 times 9 criteria postpubertal increased to 12 to 14 times, reaching adult levels. In addition to early adolescence, heavier the heart than girls of each age boys.
(B) atrioventricular growth rate the first year after birth atrial growth rate faster than the ventricular, 2 years of both the growth rate of close to 10-year-old after ventricular growth exceeding atrium. The left and right ventricular growth is uneven. Fetal period right ventricular load, left ventricular dominant right heart load. Neonatal period left and right ventricular wall thickness of 1:1, approximately 5mm. With increasing age, the amount of circulation widening significantly increased left ventricular load, left ventricular wall thickness than the right side of the growth is faster. 6 years of age, left ventricular wall thickness of 10mm, right ventricle compared with 6mm 1.6:1 (Adult 2.6:1). The age of 15, left ventricular wall thickness increased to 2.5 times, while the new-born right ventricle increased by only 1/3 of the original thickness.
(C) of the heart chamber volume from birth to adult volume of the four chambers of the heart the speed of development is not balanced. Newborn heart chamber volume of 20 ~ 22ml birth five times in seven years of age, about 100 ~~ 120ml puberty for 140ml, 18 to 20 years of age up to 240 ~ 250ml birth 12 times.
(D) the heart of the location of the position and shape of pediatric cardiac age growth and change. Heart Duocheng transverse children under 2 years of age, after the age of 2 with the Children’s stood up to walk, the development of the lung and the chest and diaphragmatic decline, the heart by a transverse position turning into oblique. The pediatric heart shape infancy is spherical, conical or oval; nearly 6-year-old followed by the adult heart shape, oblong.
(E) arterial vascular characteristics of pediatric relatively coarse than adults, such as newborn artery and vein diameter ratio of 1:1 face adult for 1:2; coronary artery is relatively thicker than adults, fully myocardial blood supply. Great vessels, 10 to 12 years ago than pulmonary artery and aorta crude, after the opposite. Infancy, lungs, kidneys, intestines and skin microvascular caliber than adult thick, it is the good of the blood supply to these organs than adults.
Second, the heart of the physiological characteristics of
(A) heart rate, the less age, heart rate, the more speed. Faster heart rate due to the Pediatric metabolism, body tissues need more blood supply, but the heart with each stroke volume is limited only to compensate for the lack of increase the number of beats. Infant fans go the immature nerve finished Zhen, central nervous degrees lower, weak inhibition of cardiac contraction frequency and intensity, while sympathetic dominant, it is easy to accelerated heart rate. Children’s heart rate normal (see Schedule 1) varies with age, and the number of unstable, therefore, should be measured by heart rate in children with quiet accurate. General each increased 1 ° C temperature, heart rate increased by about 15 times per minute. Heart rate during sleep can be reduced about 20 times per minute.
(B) its level of arterial blood pressure mainly depends on the cardiac output and peripheral vascular resistance. The smaller the pediatric age, the lower the arterial pressure. Neonatal blood pressure is lower, not easily measured by palpation or skin turn red method only for the approximation of the systolic blood pressure. The newborn systolic blood pressure between 53 ~ 71mmhg (7.05 ~ 9.44kpa), average of 65mmhg (8.65kpa). Different age blood pressure (see Schedule 2). For ease of projections, the upper limb blood pressure in children is normal can be calculated by the following formula:
= 80 + (2 x age) mmhg systolic blood pressure more than 1-year-old, the equivalent of 104 + (0.26 × age) kpa, diastolic blood pressure is systolic blood pressure 2/3. Higher standard 20mmhg (2.6kpa) above considerations for high blood pressure, lower than this standard 20mmhg (2.6kpa) above may be considered for hypotension. Normal lower limb than the upper limb blood pressure about 20-40mmhg (2.6 ~ 5.2kpa). Pulse pressure the difference between systolic and diastolic blood pressure, and the normal 30 to 40 mm Hg in (4.0 ~ 5.2kpa)
Pediatric blood pressure is affected by many external factors. Such as crying, posture changes, emotional stress can make a temporary rise in blood pressure. It should be absolutely quiet when measuring blood pressure.
(C) the venous pressure level of cardiac output, vascular function and circulating blood volume. Upper and lower chamber venous return to the right ventricle disruption also affects venous pressure.
Venous pressure is usually 3 to 5 years of age to 40 ~ 50mmh2o (0.39 ~ 0.49kpa) ,5-10-year-old is about 50 to 60mmh2o (0.49 ~ 0.58kpa). Normal children sitting or standing position, can not see the full jugular vein, Taiwan stalk to prompt venous pressure high. Right heart failure, pericardial effusion, constrictive pericarditis, or children crying, physical activity, changing position, you can see the jugular vein full of signs that prompted sick reason or temporary venous pressure rise high.
(D) measuring method commonly used in children’s cycle time of the cycle time for intravenous injection of 5% fluorescein. Normal infants average cycle time of 7 seconds. Children 11 seconds. In congestive heart failure, prolonged, congenital heart disease to the lip of the right-to-left shunt arm cycle is shortened.