Knowledge
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Is the conventional assumption that left-lateral tilt and uterine displacement avoids aortocaval compression during Caesarean section actually valid?
50 years of assumed orthodoxy is challenged by studies showing that:
- True aortal compression is relatively uncommon (Higuchi 2015, Lee 2012).
- Caval compression is probably near-universal, but also usually not improved by a mere 15 degree tilt. (An impractical 30 degrees is more likely required for meaningful impact!) (Palmer 2015).
- Caval compression probably has limited haemodynamic or fetal consequences in the fit, well, term parturient (Higuchi 2015; Lee 2012).
- Judicious use of vasopressor infusions may obviate the need for traditional uterine displacement (Lee 2017; Farber 2017).
Time to change practice then?
Not quite yet...
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Articles of interest relevant to labor epidural analgesia, both specifically focusing on obstetric epidurals and more peripherally relevant to obstetric labor analgesia.
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Carbetocin is a long-acting synthetic oxytocin analog. Although a 100 mcg dose is currently recommended, there is still some question as to the ideal dose. Dosing as low as 20 mcg may possibly be equally effective.
Carbetocin is currently only recommended for use during elective cesarean delivery, obviating the need for a post-operative oxytocin infusion currently practiced in many countries. In some countries it is also used after vaginal delivery.
It is at least as efficacious as intravenous oxytocin, and may possibly be superior at reducing postpartum haemorrhage.
Due to it's comparatively high cost compared with oxytocin however, the economic benefit of avoiding post-operative oxytocin infusions has not been demonstrated.
In the scenario of emergency cesarean section after labor augmentation with oxytocin, a much larger dose is likely required and carbetocin cannot be recommended.
One study has suggested a post-operative analgesic benefit of carbetocin vs oxytocin, although the evidence base for this is far from conclusive.
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