Neonatal physiology Flashcards
Why is the foetal circulation different to normal circulation?
- Dont need to purify blood via liver as mother does this
- Doesn’t need to oxygenate blood so bypasses lungs
- Instead get single rather than double circulation
What is the structure that allows blood to flow straight from the right atrium to left atrium?
Foramen ovale
What structure allows most of the blood flowing through pulmonary arteries to re-enter heart instead of lungs?
Ductus arteriosus
Describe the foetal circulation?
- Oxygenated blood flows through umbilical vein bypassing the liver
- umbilical vein joins the IVC as does deoxygenated blood from lower body
- IVC supplies blood through to the right atrium where IVC blood moves straight into left side of heart but blood coming in from head moves into right ventricle
- Blood flows from left atrium into left ventricle and up through aorta to the head of the foetus
- blood then returns to right atrium from head where it moves into right ventricle and mainly bypasses lungs to descending aorta
- then flows eventually back to placenta via umbilical arteries
What structure allows most of the blood to bypass the liver?
ductus venosus
How at birth does the single circulation become systemic and pulmonary?
- umbilical veins and arteries are clamped off
- Causes rise in BP in systemic circulation
- Baby takes first breath so lungs expand and increased oxygen tensions cause huge reduction in pulmonary vascular resistance
- pressure in RA, RV and pulmonary trunk fall
- pressure difference present in utero has been reversed
- Foramen oval initially closes like valve then will fibrose
- ductus arterioles closes within few days due to high O2 tension
- Ductus venosus closes hours after birth and fibroses
What are the respiratory adjustments made at birth?
- First breath of baby very important to avoid brain anoxia
- initial breath requires huge inspiratory intrapleural pressure to overcome surface tension of fluid that fills alveoli
- intra pleural pressure required needed reduces rapidly in subsequent breaths
- compliance still remains lower in neonates than adults
- expiration is also active not passive to overcome resistance from fluid in airways
- resp rate and minute volume far greater than in adults
What immunoglobulins are given to baby from mother?
- IgG through placenta
- IgA through colostrum
- passive immunity then declines and is replaced by active acquired immunity
- babies shouldnt be in an environment that is too clean
What is a normals neonate respiratory rate and minute volume?
RR = 40 breaths/min MV = 650 ml/min
What is respiratory distress syndrome?
Respiratory distress caused by surfactant deficiency increasing work of breathing
Why do new-borns often lose weight in the first few days fo life?
drop weight due to difficulties in breastfeeding both in production by mother or suckling technique of baby this usually resolves quickly
What supplements may a mother need in the first few days of breastfeeding?
Iron, calcium and Vitamin D as in great demand by baby
What happens to babies temperatures after birth?
- Greater metabolic rate so generate more heat
- however initially temp drops by 1-2 digress in first 12 hours
- neonate also large SA:V ratio so lose heat quicker
Why do temperatures fluctuate more in newborns?
- still significant temperature fluctuations due to immaturity of thermoregulatory mechanisms
how can infants produce heat?
- To increase heat infant can use brown fat to uncouple ADP phosphorylase from mitochondrial function
