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perinatal asphyxia is an insult to the foetus or new born due to a lack of
oxygenand or lack of perfusion to various organ
it is often associated with tissue lactic acidosis and hypercarbia
there is no definite definition for perinatal asphyxia
the american academy of pediatric committee on fetus and new born has
suggested essential criteria for defining perinatal asphyxia
Essential criteria for perinatal asphyxia
Prolonged metabolic or mixed acidemia (pH <7.0) on an
umbilical arterial blood sample
Persistence of Apgar score of 0-3 for >5 min
Neurological manifestations, e.g. seizures, coma, hypotonia
or hypoxic ischemic encephalopathy (HIE) in the immediate neonatal period
Evidence of multiorgan dysfunction in the immediate neonatal period
? national neonatology forum of india and WHO use an apgar of 0-3 and 4-7 at 1 min
to define severe and moderate birth asphyxia
? for the community setting NNF defines asphyxia as absence of cry at 1 min and
severe asphyxia as absent or inadequate breathing at 5 minutes
PATHOPHYSIOLOGY OF ASPHYXIA
PRIMERY APNEA-when an infant is deprived of oxygen an initial brief period
of rapid braething occurs .if the asphyxia continues the respiratory movement
cease and infant enters into a period of apnea called primery apnea
during this period heart rate will fall,neuromuscular tone diminishes,blood
pressure normal
usually tactile stimulation -reinitiate respiration
SECONDARY APNEA-if the asphyxia continues infant devolops deep
gasping respiration ,blood pressure will fall ,infant become flaccid
infant is unresponsive to stimulation
the primery and secondary apnoea clinically indistingushable
indistinguishable hence when faced with an apneic infant at birth one should
assume-secondary apnea
1. LUNG INFLATION
during intrauterine life lungs do not take part in gas exchange which is take
care of by plcenta
lungs are filled with fluid secreted by type 2 aleveolar cells
fluid is reabsorbed into the perivascular space then into blood and lymphatics
removal is slowed in when the labour is absent -elective cs
removal of fluid from the alveoli is facilitated respiration soon after birth
problem in clearing of fluid can occur in any condition which causes
inadequate dilatation of alveoli like in prematurity or sedation
PULMONARY CIRCULATION
? during intra uterine life there is little blood flow to the pulmonary circulation
due to pulmoary vasoconstriction but after birth pulmonary vasodilatation take
place and resistence will fall down
? in an asphyxiated infant due to hypoxia and acidosis the pulmonary arterioles
remain constricted and ductus arteriosus remains open
? it will lead to poor oxygenation of tissues due to inadequate uptake of oxygen
? in mildly asphyxiated children whose oxygen and ph are slightly lowered can
be corrected by quickly restoring the circulation
? but in infants with severe asphyxia ventilation alone is not useful they require
combination of oxygenation and correction of metabolic acidosis
CARDIAC FUNCTION AND SYSTEMIC
CIRCULATION
in asphyxia there is redistribution of blood flow to preserve the blood suply to
vital oragan like heart and brain
so there will be vasoconstriction in bowel,kidney,skin,muscle
if the asphyxia is prolonged the cardiac function and cardiac output too
detoriate and blood flow to all organ is further reduced
it will lead to progressive organ damage
at this stage it is neccessary to give cardiac stimulant and volume expander
to support heart and circulation
NEUROPATHOLOGY
these differs according to gestation
TERM
selective neuronal necrosis- involves cerebral cortex ,hippocampus,basal
ganglia,cerebellum,and anterior horn cells of spinal cord depending on site it manifest
as diminished conciousness,seizures,and abnormalities of feeding,breathing
parasagittal cerebral injury-it is vulnarable to ishcemia resulting in proximal limb
weakness that may devolop quadriparesis
status marmoratus of basal ganglia and thalamus-longterm sequale such as
choreoathetosis,quadriparesis and retardation
focal and multifocal ischemic cerebral necrosis
PRETERM
selective neuronal necrosis-it is rare in preterm diencephalic neuronal necrosis
restricted to thalamus and brainstem with or wthout hypothalamus and lateral
geniculate body is seen
? periventricular leukomalacia-it results from hypoxic ischemic leading to coagulative
necrosis and infarction of periventricular white matter
? cerebral cotex is spared due to rich suply of arteries
DIAGNOSIS
levene classification of hypoxic ischemic encephalopathy
feature
mild
moderate
severe
conciousnes
irritability
lethargy
comatose
tone
hypotonia
marked hypotonia
severe hypotonia
seizure
no
yes
prolonged
sucking/respiration
poor suck
unable to suck
unable to susstain
spontaneous respiration
PREPERATION FOR RESUSCITATION
each delivary should be viewed as an emergency and basic readiness must
be ensured to manage hypoxia
I. a radiant heat sourse must be ready for use
II. all resuscitation equipment immediately and should be working
III. atleast one skilled person in neonatal resuscition
EVALUATION
? it is based primerely on three signs-respiration,heart rate,and color
? LOW HEART RATE is the most important sign
ROLE OF APGAR SCORE
it is an objective method for evaluating the new born condition
it is generally performed at 1 minute and again at 5 minutes after birth
but resucitation should be initiated before the 1 minute score so APGAR
SCORE IS NOT USED TO GUIDE THE RESUSCITATION
but it can be used asses how the baby is responding to resuscitation
apgar score should be obatained every 5 minutes for upto 20 minutes if the 5
minute apgar score is less than 7
apgar score
Sign
0
1
2
Heart rate
Absent
Slow (<100 beats/min)
normal
Respiration
Absent
Weak cry
good strong cry
Muscle tone
Limp
Some flexion
active movement
Reflex irritability
No response
Grimace
cough or sneeze
Color
Blue or pale
Body pink, extremities
completely pink
blue
TABC OF RESUSCITATION
T-TEMPERATURE-provide warmth dry the baby and remove the wet linen
A-AIRWAY-position the infant clear the airway(wipe baby mouth and nose or
suction the mouth and nose some instance the trachea .insert an
endotracheal tube if necessary to ensure an open airway
B-BREATHING-tactile stimulation to initiate respiration,positive pressure
breaths canbe given either with bag and mask or bag and ET tube when
necessary
C-CIRCULATION-maintain the circulation with chest compression and
medication
RESUSCITATION ALGORITHM
at the time of birth three questions about new born should be asked
1. TERM GESTATION
2. BREATHING OR CRYING
3. GOOD MUSCLE TONE(flexed posture and active movement by the baby)
INITIAL STEPS
warmth-baby should be place under a heat source preferably
under radiant warmer.the baby should not be covered with
blankets or towels to ensure the full visualization and to permit the
radiant heat to reach the baby
positioning-the baby should be placed on her babck or side with
the neck slightly extended.this brings the posterior pharynx
,larynx,and trachea in line facilitates breathing.to help maintain the
correct position place rolled blanket or towel under the shoulder
elevating them 3/4 or 1 inch off the matress
This post was last modified on 12 August 2021