Mod 8a- Obstetric physiology

Question 1

True or false: anaesthetic risk decreases as pregnancy gets longer

Answer 1

false, becomes more risk

Question 2

What are 6 resp changes in pregnancy

Answer 2

FRC decreased 20%
Ventilation increased (progesterone)
At term minute ventilation increased 50%
O2 consumption increases 40 – 60% and 100% in labour
Blood gas: compensated respiratory alkalosis
O2 dissociation curve shifted to right

Question 3

What are the consequences of the resp changes

Answer 3

greater risk of hypoxaemia: decreased O2 stores, increased O2 demand

Airway difficulties: oedema, worse malampati score

Question 4

5 CVS changes during pregnancy

Answer 4

Cardiac output increased up to 50%
Systemic vascular resistance decreased by 20%
During labour cardiac output increases a further 40% (especially due to
pain)
Aortocaval compression (supine hypotensive syndrome) when lying down
Delivery: autotransfusion of up to 500ml

Question 5

3 haematological changes during pregnancy

Answer 5

Blood volume increases 30-40%
Plasma protein concentration decreases
Hypercoagulable state

Question 6

5 GIT changes in pregnancy

Answer 6

Increased gastric acid production
Delayed gastric emptying from 12 weeks +
* Increased even further during labour (pain, anxiety, opiates may
be used)
Decreased lower oesophageal sphincter tone
Increased risk of gastro-oesophageal reflux
* Returns to normal > 48 hours after delivery
Increased aspiration risk

Question 7

What is placental blood flow dependent on?

Answer 7

Maternal blood pressure. Spinal anaesthesia induces hypotension frequently

Question 8

5 Challenges of providing anaesthesia in obstetrics

Answer 8

Airway at risk of both aspiration and difficult intubation
Respiratory capacity decreased–rapid desaturation
Increased metabolic demands
Two patients to bear in mind
Caesarean section is major surgery with potentially major blood los