Knowledge
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What is the Quadratus Lumborum Block (QLB)?
The quadratus lumborum muscle is the deepest abdominal wall muscle, running posteriorly, dorsolateral to psoas major. Three different types of QLB have been described
What's the deal with QLB for Cesarean section?
QLB is interesting because it may offer analgesia for visceral pain after caesarean section, in addition to somatic pain. Visceral pain may be a significant contributor to post-CS pain experience, and is not blocked by existing adjuvant techniques such as the transversus abdominal plane (TAP) block.
The proposed effect of QLB on visceral pain may be due to local anaesthetic spread to the paravertebral space, although evidence confirming this is scant and suggests it occurs only in small volumes and inconsistently at best.
Additionally, as with the demonstrated inadequacy of objective sensory block from a TAP block, studies of the sensory level effects of QLB also show limited actual sensory block – even if the QLB has shown some analgesic benefit in some studies.
Some QLB studies have shown analgesic benefit for post-CS patients, although most are small studies. At this stage it appears unlikely that QLB provides routine analgesic benefit for patents already receiving standard-of-care multimodal analgesia in combination with a neuraxial anaesthetic for caesarean ection.
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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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