Pathopysiology Of A Preterm Neonate Flashcards
Terminology
Newborns = neonates = newborn infant
0-4 weeks 28 day
A baby must adapt physiologically to extra- uterine life
Neonatal period is a period of transition for both baby and family
The moment of birth
Physical size
Weight
- Average 3.5kg
- May lose 5-10% birth weight in 1st week of life and should regain this by day 10
- Steady gain at 180-210 g per week thereafter
Length
- average 51cm
Head circumference
- 35-36cm
- grows 2cm in first month
- size and speed of head growth is significant
More than 10th or less than 90th centipedes may indicate abnormality
Adaptation
Infants are most vulnerable in fist 24 hours of life
The neonate must achieve physiological changes that are critical to survival
In a healthy neonate, this transition occurs without problems
Organ system failure/ malformation/ disease can delay/ hinder/ prevent the adaptation to extrauterine life
Essential adeption
Respiration
Circulation
Thermoregulation
Nutrition - glucose homestasis
Excretion
Respiration’s
The infant must use their respiratory system for uptake of oxygen, and removal of carbon dioxide
The lungs need to be sufficiently developed for successful gaseous exchange
Lung liquid needs to be removed
Surfactant production is required to reduce surface tension between the walls of the alveoli
Circulatory changes at birth
Lungs expand
Pulmonary vessels dilate
Resistance drops in pulmonary circuit
Blood rushes to fill the pulmonary vessels
Rising o2 causes constriction of ducts artereosus
Pressure rise in the left atrium causing the closure of the foremen ovale
Foetal circulation
Placenta
Umbilical vein
Ductus arteriosus
Foramen ovale
Ductus venosus
Umbilical arteries
Postnatal heart
Ductus arteriosus closed
Right atrium
Forage ovale closed
Inferior vena cava
Right ventricle
Pulmonary trunk
Left atrium
Left ventricle
The APGAR Score
1 min 5 min 10 min
Appearance- blue, pale - body pink, Lima blue, all pink
Pulse- absent, <100, >100
Grimace- none, grimace, cry
Activity- limp, some flexion of limbs, active movement, well flexed limbs
Respiratory effort- none, slow, irregular, god strong cry
APGAR
> 8-10 no intervention
5-7 may need o2, stimulation and reassessment
< 5 will require prolonged/ major intervention
Thermoregulation
Neonates is at high risk of heat loss
. Poor temperature control due to immature hypothalamus
. Inability to spontaneously generate heat by shivering
. High surface area: volume ratio
.low levels of insulation -thin body shell
Normal bodily temperature range 36.5 37.2 °C
Can utilise town fat reserves - brown fat thermogenesis
Limb movement can generate heat
Sweat mechanism is poorly developed
Glucose homeostasis
Blood glucose levels fall for the first two hours after birth, then rise due to mobilsed energy stores
Energy stores are mobilised at birth:
- glygogenolysis ( brakedown of glycogen)
- lypolysis (breakdown of fats)
- gluconeogenesis (production of glucose)
Glycogen reserve depleted after 12 hours - fat then used as energy
Feeding needs to be established
First days
Stabilisation of body temperature
Establishment of feeding
Kidney, bladder and dowel function
Erythrocyte homeostasis and neonatal jaundice
The guy and feeding
Sucking/ swallowing coordinated
Stomach has a 15-30 ml capacity which increase rapidly in first few weeks
Cardiac sphincter is weak - reflux
Meconium passage in 12 - 24 hours
Established stools from day 3
High energy requirements for growth
Low gastric acid and enzymes levels
Gut structure present but physiology immature
Metabolic needs
High metabolic rate
High oxygen and energy needs
Limited nutrient storage
Glycogen stores easily depleted
Less able to mount metabolic response to stress
Immature liver
Neonatal jaundice
Yellowish discolouration of the white parts of the eyes and akin in a newborn baby due to high bilirubin levels
Common condition, particularly in babies born before 38 weeks gestation and some breast fed babies
Typically appears on the second or third day of life
Usually occurs because a baby’s liver isn’t mature enough to get rid of bilirubin in the bloodstream
Phtototherapy
Infant under phototherapy unit
The eyes are shielded and a super is used contain stools
Immediate physiological changes at birth
Oxygenation/ removal of carbon dioxide occurs via gaseous exchange in the lungs, rather then via the placenta
Foetal circulation must change to neonatal circulation
Glucoses homeostasis
Thermoregulation
Respiratory system
Infants under 6 months are obligate nose breathers
Shorter, narrower airways and compliant chest - increased resistance at active inspiration
Large tongue and large floppy epiglottis
Conical larynx airways shape
Diaphragm is the main respiratory muscle respiratory rate 30-40 and irregular
Increased demand for oxygen postnatally to meet metabolic demands
Rate depends rather than depth
Easily collapsed and fatigued
Reduced surface tension of alveoli
Increased risk of collapse
Cardiovascular system
Circulating blood volume 85ml/kg
Less contractile heart, left and right ventricles are of similar size at birth
Rate rather than force dependent
Unstable vascular resistance
Higher haematocrit
75-84% of Hb is feral
Rental system
Total body water is 70-80% and higher proportion of extra cellular fluid
First urine should be passed at birth or within the first 24 hours
High surface area to volume ratio
High basal metablic rate
Functionally immunature kidneys with low GFR
Fluid intake gradually increases on demand
Immature homeostasis
Neurological
Neurological the normal neonates is expected to react to certain stimuli in a particular way which gives an indication of normality
Musecle tone
Reflexes
States of consciousness
30 days
Immune response
Neurological function
Adult circulation
Beyond the neonatal period system continues to mature
Respiratory system, immune system, renal function, haemoglobin levels
Immune system
Low levels of specific immunoglobulins
Poor opsonisation
Reduced complement and phagocytosis
Reduced antigen recognition
Local bacterial infection can easily progress
Passive immunity for a give period
Neurological
Brain 12% body weight with high glucose requirement
Peripheral nervous system and myelination incomplete
Poor auto regulation immature cavalry response - exaggerated
Low pain threshold
The face
Symmetrical and well defined
Milia ( epidermal cysts) or superficial marks fade by 12 weeks
Tears produced at 2-3 months
Any squint should resolve by 2 ‘moths
Mouth palate, tongue, mucosal integrity
Ear location and shape
The skin
Clear, soft and silky and maybe covered with vernix and or languo at birth
Observe for scaliness, elastity and oedema
Fragile and permeable
Mongolian blue spots in some babies with darker pigmentations
Stork bites, erythema toxicum, milia
Jaundice may be evident at 3 - 10 days in 30-50% of all neonates
Umbilical could separates within 7-10 days
The sense
Sight- eyes open and attention to visual stimulus, prefer face and contrast, fix and follow at 6 weeks with full 20:20 at 4-6months
Hearing - head turns, prefer human voices
Touch - responsive, rooting, hand to mouth
Smell- breast mild and mother’s skin
Taste- differences sweet / sour
Pain perception is present
The trunk and limbs
Should be well aligned with a relatively large abdomen
Limbs equal in length with correct number of digits
Good movement and tone
Hips checks for dislocation
Sleep states
Length of sleep cycles change normally with the maturation of the CNS
Term: sleep - wake in 4 hours cycles later on longer
