Lecture 2 (Part 1): Newborn Adjustment PDF

Lecture 2 (part 1) Adjustment of Newborn for Extra- uterine Life Mosby items and derived items © 2005, 2001 by Mosby, Inc.  Adjustment to Extrauterine Life: Respiratory System Initiation of respiration is the most critical adaptation Chemical factors stimulate breathing – Hyp...

Lecture 2 (part 1) Adjustment of Newborn for Extra- uterine Life Mosby items and derived items © 2005, 2001 by Mosby, Inc.  Adjustment to Extrauterine Life: Respiratory System Initiation of respiration is the most critical adaptation Chemical factors stimulate breathing – Hypoxemia, hypercarbia, low pH Thermal factors stimulate breathing – Newborn leaves a warm environment and enters a cooler atmosphere – Skin sensory impulses are transmitted to the respiratory center in the medulla Mosby items and derived items © 2005, 2001 by Mosby, Inc. Adjustment to Extrauterine Life: Respiratory System Tactile factors stimulate breathing – Descent through the birth canal – Tapping the newborn’s feet, rubbing the torso, or suctioning. Mosby items and derived items © 2005, 2001 by Mosby, Inc. Newborn Respiration Fetal lung fluid removal (how?) – Compression of chest with passage through birth canal – Lymphatic vessels and pulmonary capillaries Expansion of alveoli – Occurs with initiation of breathing – Role of surfactant in keeping alveoli expanded Mosby items and derived items © 2005, 2001 by Mosby, Inc. Newborn Management Provide tactile stimulation by:  drying wet skin of newly delivered infant. Remove wet linens immediately after drying newborn.  Rub or flick soles of newborn’s feet if additional stimulation is required.  Don’t slap newborn’s buttocks (no beneficial effect; can cause cerebral trauma). Mosby items and derived items © 2005, 2001 by Mosby, Inc. Newborn Circulation Circulatory changes allow blood to flow through lungs. Pressure changes in heart, lungs, and vessels. Functional closure of fetal shunts – Foramen ovale – Ductus arteriosus – Ductus venosus Mosby items and derived items © 2005, 2001 by Mosby, Inc. Sequential Circulatory Changes in the Newborn Inspired oxygen dilates pulmonary vessels Pulmonary vascular resistance decreases and pulmonary blood flow increases Pressure in RA, RV, and pulmonary arteries decreases Gradual increase in systemic vascular resistance after clamping of cord Mosby items and derived items © 2005, 2001 by Mosby, Inc. Further Circulatory Changes in the Newborn LA pressure > RA pressure leads to closure of foramen ovale Increase of pulmonary blood flow and dramatic reduction of pulmonary vascular resistance begins to close the ductus arteriosus Mosby items and derived items © 2005, 2001 by Mosby, Inc. Changes at Birth Mosby items and derived items © 2009, 2005 by Mosby, Inc., an Mosby items and derived items © 2005, 2001 by Mosby, Inc. affiliate of Elsevier Inc. Typical Times for Newborn Circulatory Changes Foramen ovale: functional closure soon after birth Ductus arteriosus: functional closure in about 4 days after birth; anatomic closure takes considerably longer Failed closure of the above shunts takes blood away from newborn’s pulmonary circulation Mosby items and derived items © 2005, 2001 by Mosby, Inc.  Thermoregulation The newborn has nonshievering thermogenesis which accomplished primarily by metabolism of Brown Fat that. Increased the metabolic rate in the brain, heart and liver. Brown fat is located in superficial deposits in the inter-scapular region, axillae, thoracic inlet, along the vertebral column, and around the kidneys. Mosby items and derived items © 2005, 2001 by Mosby, Inc.  Mechanism of Heat loss Convection - heat from body to air.  Nursery room should be kept at 24c and wrap the baby well. Radiation - heat from body to cooler solid surfaces in relative proximity.  Nursery cribs and examination table are placed away from outside windows to prevent this way of heat loss. Mosby items and derived items © 2005, 2001 by Mosby, Inc.  Evaporation - liquid on body is converted to a vapor.  Delay the bathing and dry the newborn directly after birth. Conduction - heat from body to cooler surfaces in direct contact.  Use warmed crib and warm measuring tape and stethoscope. Mosby items and derived items © 2005, 2001 by Mosby, Inc. Factors Predisposing the Newborn to Excessive Heat Loss Large surface area results in heat loss to environment Newborn’s thin layer of adipose is poor insulator Newborn cannot shiver to increase heat production Immature thermoregulatory center in the brain. Blood vessels are closer to the surface of the skin. Mosby items and derived items © 2005, 2001 by Mosby, Inc. Hemopoietic System Blood volume depends on placental transport of blood FT (full term) newborn blood volume is approximately 80-85 mL/kg body weight Avg blood volume for newborn = 300 mL +/- 100 mL Mosby items and derived items © 2005, 2001 by Mosby, Inc. Fluid and Electrolytes Newborn body weight is 73% fluid (Adult is 58% fluid) Infant has higher ratio of extracellular fluid than adult Infant has higher level of total body Na++ and Cl + Infant has lower level of total body K+, Mg + +, and phosphate + Mosby items and derived items © 2005, 2001 by Mosby, Inc.  Implications Rate of fluid exchange in newborn much faster than in adult Rate of metabolism in newborn twice as great related to body weight Acid forms quickly, leading to rapid development of acidosis. Immature kidney cannot concentrate urine to conserve body fluid Mosby items and derived items © 2005, 2001 by Mosby, Inc. Newborn Resultant Problems Prone to dehydration Prone to acidosis Prone to over hydration/ fluid overload Mosby items and derived items © 2005, 2001 by Mosby, Inc.