FRCA Notes

Placenta Accreta Spectrum Disorders

Resources

  • The incidence of 'placenta accreta spectrum' (PAS) is 1 in 600, but is increasing due to higher rates of LSCS
  • The risk is higher if placenta praevia is present
  • There is an abnormal adherence between the placenta and the uterus
  • The lack of normal placental separation from the uterine wall leads to:
    • Rapid maternal haemorrhage
    • Increased need for LSCS
    • Higher rates of hysterectomy; PAS is the commonest indication for this and required in up to 90% of PAS patients
    • Increased maternal mortality
  • It is diagnosed by use of antenatal USS ± MRI in the second or third trimester

Classification

Pathology Frequency Description
Accreta 85% Placenta is adherent to, but does not invade, the myometrium
Increta 18% Placenta invades through the myometrium
Percreta 7% Placenta invades through uterine serosa ± other pelvic structures e.g. bladder


Perioperative management of patients with placenta accreta spectrum disorders

Obstetric planning

  • Elective LSCS is planned for 35 - 36+6 weeks' gestation
  • This reduces the risk of APH or other emergencies
  • Requires antenatal steroids to enhance foetal lung maturity from 34 - 36 weeks' gestation

  • Delivery should take place in a unit with appropriate capabilities e.g. access to hybrid theatres, critical care support
  • Typically two senior obstetricians are required
  • Input from other specialties is required, e.g.:
    • Obstetric anaesthetists
    • Interventional radiology
    • Vascular surgery
    • Urology; 15% of cases require cystotomy

Anaesthetic review

  • Should identify risk factors for and discuss anaesthetic options, including GA and RA
  • Detection and optimisation of anaemia
  • Discussion about transfusion, blood product use and cell salvage

Plan for major haemorrhage

Blood loss Prevalence
>2L 66%
>5L 15%
>10L 7%

  • Liaison with Haematology for availability of blood products
  • Appropriate cross-matching; 4 units RBC in theatre + 4 units FFP in theatre ± further in blood bank
  • Availability of rapid-transfusions systems
  • Cell salvage
  • Point of care testing e.g. VHA
  • Adequate staff/support
  • Consideration of location e.g. main theatres, hybrid operating suite
  • Plans for rescue techniques (see below)

Monitoring

  • AAGBI monitoring as standard
  • 2 x wide bore IV access e.g. 14G, 16G
  • ± A-line
  • CVC often not required
  • Point of care TTE/TOE can help manage maternal volume status to guide resuscitation in major haemorrhage

Anaesthetic technique

  • Technique may be influenced by maternal preferences

  • Neuraxial techniques can be safely performed
  • CSE may be appropriate, although 21% of patients with placenta praevia and suspected PAS required conversion to GA
  • Conversion to GA is typically to facilitate surgical exposure or for pain control
  • Some patients will be offered 'elective' conversion to GA post-delivery but pre-hysterectomy

  • GA is often required e.g. heavy blood loss, long procedure, to facilitate other procedures

Vascular occlusion techniques

  • Prophylactic insertion of a balloon to occlude the internal iliac arteries is associated with lower intra-operative blood loss and lower rates of hysterectomy
  • REBOA (resuscitative endovascular balloon occlusion of the aorta) has also been described
  • May be especially useful in patients who refuse either hysterectomy or blood product transfusion

Measuring blood loss

  • Estimating blood loss intra-operatively may be difficult, especially as visual estimation decreases in accuracy as increasing volumes are lost
  • Methods to quantitatively assess blood loss (QBL methods) include:
    • Gravimetry
    • Calibrated under-buttock V-drapes
    • Colorimetric technologies
  • These may be used to help improve estimation of blood loss, though have not been proven to lower maternal morbidity

  • HDU care is often required, especially if hysterectomy or major blood loss
  • Vigilant monitoring is often required owing to the risk of further bleeding, fluid overload and MODS
  • VTE prophylaxis; may have increased risk due to surgical complexity and relative post-operative immobilisation

Analgesia

  • Analgesia requirements are typically higher due to greater surgical complexity, including greater tissue trauma and longer operative times
  • As ever, multi-modal analgesia is the name of the game; patients may benefit from regional techniques e.g. TAP blocks even if they've received intrathecal opioid
  • No evidence that routine use of ketamine, clonidine or gabapentin significantly enhances analgesia for those post-LSCS for PAS