Review Note

Last Update: 03/27/2025 09:37 PM

Current Deck: ACG Part 2::Obstetrics

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Commit #309764

SS_OB 1.34 Discuss the anaesthetic management of problems that may arise with labour and delivery, including the following situations:
- abnormla placental implantation

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Commit #309764

Placenta Previa

Placenta sits within 20mm of internal os. Incidence 1 in 200

Often resolves as the lower segment develops later in pregnancy
Repeat USS offered for assessment

Choice of anaesthetic :

Contentious and often based on institution

Posterior accreta : neuroaxial
Anterior accreta : neuroaxial (+/- arterial line, + extra large drip)
Placental previa : GA +/- spinal

Consider spinal for positioning, catheter, etc to reduce GA delivery to foetus.

Placenta previa

Low implantation of the placenta in the uterus, either overlying or encroaching on the cervical os. Placenta sits within 20mm of internal os

Affects 0.6% of pregnancies, more common in multiparous women.

Especially common in women who have had a previous LSCS.

Sx: painless vaginal bleeding in the third trimester.

Classification

Total – placenta completely covers the os.

Partial – some encroachment on the os by the placenta.

Marginal – placenta not covering but close to the internal os.

Placenta accreta

Placenta is adherent to the implantation site with an absent decidua and thus adherent to the myometrium.

Increased likelihood in patients with previous LSCS.

Classification

Increta – placenta invades the myometrium (but not serosa).

Percreta – placenta extends through the myometrium and may adhere to surrounding structures; hysterectomy required in 95% of women with a 7% overall mortality rate.

Investigations

US, MRI.
- a negative US or MRI doesnt rule out

Management

Arterial embolization under radiologic guidance may decrease the extent of bleeding before or during caesarean hysterectomy.

Cell salvage.

Anaesthetic management

Dictated by likelihood of maternal haemorrhage, maternal preference, obstetric/anaesthetic experience.

Pre-op

Increased risk of haemorrhage as:
- Placenta may have to be divided to facilitate delivery.
- Lower uterine segment does not contract as effectively as the body of the uterus, so the placental bed may continue to bleed following delivery.
- Regional anaesthesia can be safely used for placenta praevia, providing the patient is normovolaemic before neuraxial technique is performed.

Pre-op evaluation and assessment

Consider interventional radiology.

Large IV access x2.

Bloods – FBE, G&H, crossmatch 2-8U blood.

Cell salvage should be used if available.

Intra-op

For bleeding patients, GA is preferred choice.

Need for a range of uterotonics – oxytocin, ergometrine, carboprost, misoprostol.

Don't forget surgical methods of controlling bleeding – bimanual compression of the uterus, ligation of internal iliac arteries, temporary compression of the aorta.

Post-op

HDU monitoring as haemorrhage may still occur.

Vasa Previa

Uncommon placental condition, which can result in a true emergency.

High fetal mortality.

Fetal velamentous insertion of the umbilical vessels, so they run through amniotic membranes traversing between the fetal presenting part and the cervical os.

Vessels are susceptible to trauma during labour and are fragile, leading to fetal bleeding – small amount of blood loss may result in fetal demise unless quickly diagnosed and emergency LSCS can be performed immediately.

Sx: vaginal bleeding and FHR abnormalities immediately on rupture of the amniotic membranes.

Anaesthetic management

Fastest anaesthetic technique for LSCS.

GC notes