The potential for dexamethasone and other glucocorticoids to prolong peripheral nerve blocks was first noted almost 20 years ago.
While the effect has been observed with several different blocks (upper & lower extremity, and even TAP blocks), the clinical significance varies and several questions still remain:
Is the effect exclusive to perineural dexamethasone? Several studies have observed similar effects for both IV and perineural dexamethasone (though less profound than other papers).
Is the effect safe? This is perhaps the most concerning, as there are suggestions that the effect may represent an enhancement of the well-known neurotoxicity of local anaesthetic agents.
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.summary