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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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The remifentanil PCA for labour analgesia controversy continues...
Those advocating its first-line use point to reassuring evidence of maternal satisfaction and acceptability, reduced epidural rates, and some suggestion of reduced instrumental delivery rates.
For the negative, the ongoing safety concerns created by routine use of remifentanil PCAs are foremost, particularly given how uneven hospitals can be at implementing best safety practices. Observed rates of significant desaturation range from 25-70%, in addition to potential neonatal effects.
The greatest challenge facing the remiPCA advocates, is that the labour epidural is still the most effective form of labour analgesia, and has only improved over the decades as safety has been both maintained and increased.
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Why the excitement?
Since the landmark 2017 WOMAN trial (collected below) showed that tranexamic acid (TXA) may reduce mortality in post-partum haemorrhage, TXA has increasingly been found in close proximity to where obstetric spinal anaesthetics are commonly performed.
TXA's operating theatre ubiquity has also been enhanced by it's replacement of aprotonin in cardiac surgery (Myles 2017, Koster 2015), after the former's associated mortality bump, along with the increasingly routine use of TXA in major joint surgery to reduce bleeding and transfusion (Ho 2003, Poeran 2014).
Recent reviews have identified 21 case reports of mistaken intrathecal administration of TXA over 60 years of anaesthetic publications – although it is likely many cases have been unreported.
Seems rare - why should I be concerned?
- Intrathecal TXA has a 50% mortality, and frequently leaves survivors with permanent neurological injury.
- Once recognised, immediate, aggressive management may improve outcome (particularly, CSF lavage).
- Although rarely published, the increased use of intra-operative TXA may bring it into close proximity with common intrathecal drug ampoules, increasing the risk of this devastating error. Case report publication dates support the increasing incidence.
- Knowing the potential for this error is the first step to avoiding it both personally and systemically.
- Almost all cases involve drug swap errors with major human factor contributions.
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