PHYSIOLOGY OF NEWBORN

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NEWBORN PHYSIOLOGY:

NEWBORN PHYSIOLOGY

Who is a new born?:

Who is a new born? ‘ A live baby born either normal or as high risk irrespective of gestational age’

Slide 3:

Transition from intrauterine to extrauterine life. Dependence to independence Bio-psycho-social adaptation. Newborn’s adjustment depends upon: Genetic composition Competency of recent Intrauterine environment Care during birth Care during neonatal period Physiological & Psychological basis of Newborn adaptation

Immediate physiological adjustment of newborn:

Immediate physiological adjustment of newborn Respiratory movements in utero – Start from 11 wks of fetal life By 34 wks – regular movements present (40 – 70/ mt) Extra-uterine resp function establishes due to : - Extrauterine respiratory movements - Air entry overcoming opposing forces - Air remaining in the alveoli during expiration (FRC) - Fall in Pulmonary vascular resistance - Increase in pulmonary blood flow

Chemical stimuli (Transitory asphyxia of fetus & Neonate):

Chemical stimuli (Transitory asphyxia of fetus & Neonate) Foetal factors – Compression of umbilical cord Changes in maternal posture Fall in maternal oxygenation (bearing down) Neonatal factors – Cessation of placental gas exchange Cessation of umbilical cord pulsation Cutting of the cord ---- Temporary asphyxia  Resp center stimulated

Thermal stimuli :

Thermal stimuli Change in temp from intra uterine (98.6 F) to extra uterine (70.75 F) Excites nerve impulses in skin  Resp center stimulated

Sensory & Physical stimuli:

Sensory & Physical stimuli Tactile stimuli – Touch Auditory – Sounds---noises Visual – light  Resp center stimulated

Mechanical stimuli:

Mechanical stimuli Compression of chest in birth canal Sudden expansion (recoil)  -ve pressure  Inspiration (mechanical suctioning)

INITIATION OF RESPIRATION:

INITIATION OF RESPIRATION CHEMICAL STIMULI SENSORY STIMULI THERMAL STIMULI < Pao2, > Paco2 < pH MECHANICAL STIMULI Sound, Light, Pain Smell, Touch Cold Chest Compression Chest Recoil Stimulation of Aortic & Carotid Chemoreceptors Auditory, Visual Olfactory, Tactile Proprioceptic Chemoreceptors Thermal Receptors Stretch Receptors Resp. Centre -medulla Afferent nerve impulse Via SPINAL CORD Contraction of diaphram Expulsion of lung Fluid Passive inspiration INITIATION OF RESPIRATION

ESTABLISHMENT OF RESPIRATION:

ESTABLISHMENT OF RESPIRATION CHEMICAL STIMULI SENSORY STIMULI THERMAL STIMULI Mechanical events MECHANICAL STIMULI Chest recoil 1/3 of fluid lost <ed Alveolar surface tension (surfactant) Chest compression Subsequent breaths causes absorption of remaining fluid <ed Pulm vascular resistance >ed Alveolar PaO 2 >ed Pulm vascular volume >ed Pulm & lymphatic circulation Air entry into lungs <ed Interstitial pressure ADEQUATE OXYGENATION PROMOTED Baby cries! FIRST BREATH

Factors opposing first breath:

Factors opposing first breath Alveolar surface tension Viscosity of lung fluid Degree of lung compliance Mucus, blood, meconium, amniotic fluid

ASSESSMENT The Apgar score:

ASSESSMENT The A pgar score SIGN 0 1 2 Heart Rate Absent Slow (<100) More than 100 Resp. Rate Absent Slow, Irregular, Weak cry Good strong cry Muscle Tone Flaccid Some flexion Well flexed Reflex No Response Grimace Cough, Sneeze Colour Blue, Pale Body pink, extremities blue Normal skin colour

Modified action oriented assessment of baby at birth:

Modified action oriented assessment of baby at birth Fetal distress Yes/ No Duration Pethidine to mother Yes/ No Hrs before birth First cry ___mts after birth Respiration Absent/ slow/ irregular Heart rate Absent/ <100/>100 per mt

Characteristics of Neonatal Respiration:

Characteristics of Neonatal Respiration Normal rate – 30 – 50/ mt Nature – Diaphragmatic with some synchronization with chest movement Initially shallow, irregular Later, deep & regular Periodic respiration --- normal breathing In deep – regular resp Obligatory nose breathers Danger signs - Rate <30 or > 60/ mt at rest Dysnea, cyanosis >ed use of IC muscles (Resp distress) Noisy breathing (?fluid/ other obstruction)

CIRCULATORY ADAPTATIONS:

CIRCULATORY ADAPTATIONS becomes Fossa ovalis Becomes Ligamentum arteriosum Becomes Ligamentum venosum Umbilical vein becomes Round ligament Become Umbilical ligaments

CIRCULATORY ADAPTATIONS:

CIRCULATORY ADAPTATIONS UMBILICAL CORD – CUT & CLAMPED <ed blood flow <ed pulm vascular resistance <ed pressure on Rt side VENTILATION Pulm vascular dilatation, <ed resistance & >ed flow >ed blood flow to the Lt side Lung expansion Closure of foramen ovale, Ductus venosus, ductus arteriosus >ed pressure on the Lt side FOETAL SHUNT REVERSED

CIRCULATORY CHANGES:

CIRCULATORY CHANGES HR – Initially 175 – 180/ mt---120 – 150/ mt BP – 74/47 mm Hg (resting) >es by 20 Heart murmur – Slight cardiomegaly - Immediately after birth Last for a few days

HEMATOPOIETIC SYSTEM:

HEMATOPOIETIC SYSTEM RBC – 5 – 6.5 milliion/ mm cube. <es to 4 – 5 million by 10 th day Reticulocytes – 4 – 6%. <es to 2% Hemoglobin – 16 – 20 gm%. <es to 15 gm% WBCs – 20,000/mm cube at birth. <es to 10,000/ mm cube by 3 rd day. Then gradual rise till end of the week S Bil – 1-2 gm% (Immature liver)

ENDOCRINE & METABOLIC ADAPTATION:

ENDOCRINE & METABOLIC ADAPTATION

THERMOREGULATION :

THERMOREGULATION Anatomic factors Environmental factors Large surface area Evaporation Less adipose tissue Conduction Thin epidermis Low humidity and fast air current Convection Presence of fluid on neonates body Ambient temp. at birth cooler than intrauterine environment Radiation Ability to produce heat and maintain a normal body temperature

NEONATAL RESPONSES TO -:

NEONATAL RESPONSES TO - Hypothermia Hyperthermia Vasoconstriction Vasodilation Increased Metabolic Rate Increased O2 consumption Increased Muscular activity Increased water loss Non shivering thermogenesis

GIT ADAPTATIONS:

GIT ADAPTATIONS Mature mostly all over. Some salivary glands functional Liver immature at first. Deficient in – Glucoronyl enzyme  Physiological jaundice Prothrombin & coagulation factors  Bleeding tendency Glycogen stores  Hypoglycemia Stomach capacity – 90 ml, emptying 2 ½ - 3 hrs, rapid peristalsis & digestion Enzymes – Adequate for proteins & simple sugars. Pancreatic amylase deficient ………………

Slide 23:

Bowel movement – Frequent (7- 10), semi solid Intestines – Larger in relation to body size, more no of secretory glands, more surface area for absorption Cardio-esophageal sphincter – Relaxed (  Regurgitation) Meconium – (Amniotic fluid, mucus, bile pigments, fatty acids, epithelial cells , blood) – First 3 days Transitional stool – By 4 th day (colour, consistency, odor)

RENAL ADAPTATIONS:

RENAL ADAPTATIONS Structurally mature, functionally immature Frequent voiding (20) for 15 – 20 days Inability to concentrate urine  susceptible to dehydration, acidosis, electrolyte imbalance Urine – Sp Gr 1.000, no colour, no smell till 2 – 3 months Total volume – 200 – 300ml/ 24 hrs (15 to 30 ml /Kg per 24 hrs).

MUSCULO-SKELETAL ADPTATIONS:

MUSCULO-SKELETAL ADPTATIONS Bones – Ossification continued Nose – Mostly cartilagenous. Frequently flattened Skull bones – 6 (soft) with open sutures Sinuses – incompletely formed Muscular system completely formed – Grows in size

IMMUNOLOGIC ADAPTATIONS:

IMMUNOLOGIC ADAPTATIONS Immunoglobins – Foetus synthesizes immunoglobins – 20 th week of gestation. (IgM, IgG and IgE) IgG crosses placenta. IgA secreted in colostrum IgM does not cross placenta. Surface protection - Vernix caseosa, skin & mucus membrane RE system – Produces neutrophils, Monocytes, Eosinophils & Lymphocytes.

NEUROLOGICAL ADAPTATIONS:

NEUROLOGICAL ADAPTATIONS Newborn’s brain – 25% of adult size. Incomplete myelination of nerve fibres. Primitive reflexes disappear when nervous system develops. ANS and Brainstem co-ordinate vital respiratory & cardiac functions.

SENSORY ADAPTATION:

SENSORY ADAPTATION Vision – Eyes structurally incomplete Ciliary muscles immature – Poor accommodation & fixation (hypermetropia in first month) Pupillary reaction - Blink reflex + Corneal reflex + Tear glands – Not active till 2 – 4 weeks of life

SENSORY ADAPTATION..:

SENSORY ADAPTATION.. Hearing – Startle reflex, crying Low frequency voices <es cry & motor activity Can identify mother’s voice by 3 days of life Smell – Reacts to strong smell Can identify mother’s milk

SENSORY ADAPTATION..:

SENSORY ADAPTATION.. Taste - Can distinguish taste Taste buds – on tip of tongue in early life Touch – Can perceive touch all over body Responds to patting, stroking, rubbing Cries with painful stimuli

PSYCHOLOGICAL ADAPTATION:

PSYCHOLOGICAL ADAPTATION Early mother/ father child bonding ‘Rooming In’…’Bedding in’ Gentle handling

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