Session Key Points
- Aortocaval compression can result in a fall in maternal cardiac output (CO), and/or a fall in fetoplacental perfusion
- Maternal CO increases by 40% at term and rises further in labour and post-delivery
- Functional residual capacity falls, minute ventilation and oxygen consumption rise, leading to more rapid desaturation during apnoea and to a more rapid rise in end-tidal oxygen concentrations with pre-oxygenation, and to lower maternal PaCO2
- Anatomical changes to the airway and chest increase the difficulty of laryngoscopy and intubation and make endobrochial intubation more likely. Displacement of the heart leads to characteristic ECG changes
- Gastrointestinal changes lead to an increased tendency to gastro-oesophageal reflux of more acidic gastric contents
- Maternal blood volume rises more than plasma volume. There is a fall in normal haemoglobin concentration. Changes in the coagulation system predispose the mother to thromboembolism
- There is increased maternal sensitivity to both local and general anaesthetics
- Renal changes lead to proteinuria and dilatation of the urine collecting system. There is an increase in GFR. There is a predisposition to urinary tract infection
- Hormonal and metabolic changes lead to a tendency to diabetes, to sodium and water retention and to an increase in BMR
