Acid Base Physiology

Question 1

Causes of fetal hypoxia

Answer 1

Maternal oxygenation compromised
Maternal perfusion of placenta is reduced
Delivery of oxygenated blood from the placenta to the fetus is impeded

All can include haemorrhage, vasovagal, epidural, uterine contractions, abruption, cord compression

Question 2

Effect of build up of lactic acid

Answer 2

Depletion of buffer system —>metabolic acidosis—>lower fetal pH and poor apgar

Question 3

Maternal acid-base balance in pregnancy

Answer 3

Fall in arterial CO2 tension and rise in O2 tension, reduction in plasma bicarbonate
—>results in a primary respiratory alkalosis and a compensatory metabolic acidosis
Ph tends towards alkaline in pregnancy

Question 4

Fetal pH levels of acidosis

Answer 4

PH <7.2 - acidosis

Ph 7.2-7.25 - pre-acidosis

Question 5

Essential criteria that define an acute, intrapartum hypoxia event

Answer 5

Acidosis on FBS, umbilical arterial cord, or early neonatal bloods (pH <7, BE >12)
Spastic quadriplegia or diskinetic type of CP
Early onset of mod to severe neonatal encephalopathy <34/40
Other causes excluded (congenital abnormality)

Question 6

Suggestive criteria of acute, intrapartum hypoxia event

Answer 6

Sentinel hypoxia event (cord prolapse)
-early evidence of multi-organ involvement
Early evidence of cerebral imaging abnormality
Apgar <6 for >5min
Sudden, rapid, sustained deterioration in the FHR pattern when previously normal