Fetal Heart Flashcards
What is the purpose of fetal heart monitoring?
To detect insufficient oxygenation at an early stage because heart rate pattern changes in response to oxygenation
What 4 factors is fetal oxygenation dependant upon
Maternal oxygenation
Maternal blood flow
Placental function
Fetal circulation
What is fetal cardiac output controlled by?
Heart rate
Where does the heart beat start?
In the sinoatrial node
What determines the rate of normal heart beat?
Sinoatrial node
Where does the impulses from the sinoatrial node move to?
Atrioventricular node
What nervous system can adjust heart rate?
Autonomic nervous system
What division of the autonomic nervous system increases heart rate
Sympathetic nervous system (fight or flight)
What division of the autonomic nervous system decreases heart rate?
Parasympathetic nervous system (rest and digest)
What does good baseline variability on a CTG demonstrate?
A healthy autonomic nervous system
What two types of receptors can influence the autonomic nervous system?
Chemoreceptors
Baroreceptors
Chemoreceptors
Receptors that defect change in blood concentration of certain substances such as oxygen and carbon dioxide
What would the autonomic nervous system response be to a drop in oxygen in the blood?
Chemoreceptors would detect this and stimulate Parasympathetic nervous system to activate adrenaline release and increase in heart rate
Baroreceptor
Receptors that detect changes in arterial blood pressure
How would the autonomic nervous system respond to a rise in BP?
Baroreceptors would detect this and Stimulate parasympathetic nervous system which would decrease heart rate
Why is the fetus fairly resistant to hypoxia?
It has higher levels of haemaglobin and a greater affinity to oxygen
Fetal response to a fall in oxygen saturation
Chemoreceptors trigger sympathetic activity
Increase in heart rate and therefore increase in cardiac output
What is one of the initial signs of fetal response to hypoxic environment
Baseline tachycardia
Why is oxygen necessary for fetus
Oxygen required to utilise glucose
What would happen in a case of prolonged oxygen deprivation
All liver glucose used up
Anaerobic metabolism
Why is fetal blood lactate checker sometimes
To test for whether the fetus went into survival mode due to hypoxia and used glucose reserves and had to use anaerobic metabolism (lactate as a product)
The length of time a fetus can withstand hypoxia depends on what?
Glycogen stores
