Perinatal Asphyxia and Infection

Question 1

Hypoxia-Ischaemia at birth

Answer 1

Infants need resuscitations at birth
–> may have absent HR< infant not breathing
–> may require airway, respiratory and haemodynamic support
Infant subsequently encephalopathic

Question 2

Hypoxia-ischaemia warnings

Answer 2

Decreased foetal warnings

Sentinel events- placental abruption, uterine rupture, cord prolapse

Question 3

HI Preserved blood supply

Answer 3

CNS
Myocardium
Adrenals

Question 4

HI Vulnerable blood supply

Answer 4

Kidneys
GI tract
Liver
Muscle

Question 5

Encephalopathy in newborn

Answer 5

Abnormal neurologic function + consciousness level
Abnormalities of tone and reflexes
Autonomic dysfunction
Seizures

Question 6

Sarnat study of perinatal asphyxia

Answer 6

Stage 1- less than 24 hrs, hyperalertness, uninhibited Moro and stretch reflexes, symp. effects and normal EEG
Stage 2- obtundation, hypotonia, multifocal seizures, EEG periodic pattern sometimes preceded by continuous delta activity
Stage 3- stuporous, flaccid and brain stem + autonomic functions suppressed

Question 7

Foetal/perinatal hypoxia +/or ischaemic cerebral insult

Answer 7

Leads to primary neuronal injury
Primary energy failure
Derangement of cellular function
Secondary energy failure
Secondary neuronal injury, further necrosis and apoptosis

Question 8

Energy consequences Hypoxia-Ischaemia

Answer 8

Phosphorus spectra normal first few hours after resuscitation
12-24 hours- progressive decline in PCr/Pi ratio
Delayed ATP decline

Question 9

Secondary energy failure

Answer 9

Acute hypoxia ischaemia –> reperfusion (after resuscitation) –> secondary energy failure (several hours after reperfusion)

Question 10

Cerebral Hypoxic-Ischaemic injury

Answer 10

Primary neuronal death

Resuscitation – Reperfusion, Oxygenation

Cerebrovascular dysfunction
Glutamate release
Free radicals
Calcium entry
Apoptosis

Secondary neuronal death

Question 11

Mechanisms of brain injury in Hypoxia-Ischaemia

Answer 11

Glucose + O2 deprivation
Energy depletion – decreased ATP
Glutamate receptor activation
Accumulation of intracellular Ca
Free radicals – NO, superoxide, Fe, H2O2, 
Lipid peroxidation 
Oligodendroglial death
Apoptosis

Question 12

Neuroprotection targets

Answer 12

Decreased energy depletion
Glutamate
Inhibition of leukocyte/microglial/cytokine effects
Blockade of downstream intracellular events

Question 13

Decreased energy depletion

Answer 13

Glucose
Hypothermia
Barbiturates

Question 14

Glutamate

Answer 14

Inhibit glutamate release (Ca channel blockers, magnesium, adenosine, hypothermia)
Fix glutamate uptake impairment - hypothermia
Glutamate receptor blockade- magnesium

Question 15

Blockade of downstream intracellular events

Answer 15

Hypothermia
Free radical synthesis inhibitors (allopurinol, magnesium)
Free radical scavengers (Vit E)
NOS inhibitors
Anti-apoptotic agents

Question 16

Hypothermia

Answer 16

Decreased cerebral metabolism
Decreased energy use
Decreased accumulation of excitotoxic amino acids
Decreased NO synthetase activity 
Decreased free radical activity

Question 17

Early onset sepsis

Answer 17

Within 48 hours
Microbes acquired from mother
Before or during passage through birth canal
2-3 per 1000 live births
Fulminating septicaemia --> meningitis, pneumonia
PROM
Maternal UTI
Prematurity

Question 18

Organisms causing early-onset sepsis

Answer 18

Group B Strep

E Coli

Question 19

Early Onset GBS

Answer 19

Most cases sepsis develop within first few hours
May mimic perinatal hypoxia-ischaemia
–> apnoea, severe hypoxia, cardio-resp failure, hypotension, metabolic acidosis, tachycardia, poor perfusion

Question 20

Early onset GBS predisposing factors

Answer 20

1% babies born vaginally to mothers who carry GBS become infected
Evidence chorioamnionitis including maternal fever
Prolonged labour
Prolonged rupture of membranes
Low birthweight

Question 21

Prevention + treatment of GBS sepsis

Answer 21

Prevention vertical transmission- intrapartum antibiotic prophylaxis to women who show carriage during pregnancy screening
Treatment- Benzylpenicillin with amikacin or gentamicin

Question 22

Late onset sepsis

Answer 22

More than 48 hours after birth
From Postnatal environment
Nosocomial
4-5 per 1000 live births
Mostly preterm infants on neonatal units

Question 23

Late onset sepsis organisms

Answer 23

Coagulase-negative staphylococci

Staph Aureus

Question 24

Early onset GBS investigations

Answer 24

FBC- neutropenia
CRP- rise may be delayed by 12 hours
Blood cultures
Lumbar puncture
Chest X ray