General anaesthesia
The National Health Service maternity data suggest that between 2% and 4% of deliveries are carried out under general anaesthesia annually. General anaesthesia in obstetrics is indicated for immediate operative deliveries, and in situations where regional anaesthesia for operative intervention is contraindicated or has been performed and found to be inadequate for surgical anaesthesia.
Technique
The risk of hypotension from aortocaval compression should be reduced by placing the parturient in a supine position with a 15-degree left lateral tilt.
• Induction—thiopentone is the induction agent most frequently used for induction of anaesthesia in the obstetric population. The use of propofol is slowly gaining popularity in obstetrics. Both drugs rapidly cross the placenta but do not cause excessive neonatal depression when standard doses are used. Ketamine is useful in the presence of hypotension from haemorrhage. It does not cause a reduction in blood pressure because of its sympathomimetic effects. Ketamine may cause delirium and hallucinations in the mother and can be rapidly detected in the fetus.
• Muscle relaxation—suxamethonium is the muscle relaxant of choice for obstetric general anaesthesia because its fast onset time (her understand the options available for pain relief and its impact on her, the course of her labour, and her baby.
Options for pain relief should ideally be discussed with parturients before the onset of labour. The broad range of options and their associated risks and benefits should be discussed without bias. Excellent resources can be found on the Obstetric Anaesthetists' Association website (https://www.oaa-anaes.ac.uk) including printable patient information cards in multiple languages.