Article Notes
- Sellick's original 1961 description is based upon significantly flawed audit data.
- There is much contradictory primary science research showing some effect of CP.
- NAP4 found pulmonary aspiration responsible for more deaths than intubation or ventilation failures, and the US ASA Closed Claims database shows it to be the third most common pulmonary event leading to claims. Thus recommendations and guidelines for the use of cricoid pressure carry very real medicolegal implications even in the absence of quality clinical evidence.
- Microaspiration in elective surgery is common (20%) but does not appear to be modified by CP.
- CP has a variable effect on the ease of intubation.
- There is no agreement on CP application technique nor even on scenarios where it should or should not be used.
- CP guidelines are variable, based on low-quality evidence and largely dependent on expert opinion.
- CP use is largely up to individual judgement, with a pragmatic approach best adopted for its application or release.
- Perhaps the greatest impact can be gained from ultrasound evaluation of gastric volume to identify those most at risk of aspiration?
- Complicating large volume resuscitation in an awake patient.
- Accentuating hypotension due to sympathectic block.
- Having an unsecured airway in the event of intraoperative crisis.
- Creating neuraxial uncertainty when coagulopathy occurs.
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Notably, a further 5 (4%) required GA conversion before delivery due to inadequate block. ↩
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The researchers administered the remaining 90 mcg fentanyl IV, along with droperidol 1.25 mg and acetaminophen/paracetamol 15mg/kg after baby delivery. An NSAID (diclofenac 50mg) was only provided when breakthrough pain was requested. ↩
Zdravkovic, Rice and Brull take an objective look at the current evidence for cricoid pressure (CP) and professional guidelines for its use, reiterating the persistent uncertainty and general low-quality of evidence supporting use or avoidance.
They note...
Be smart
Bedside risk stratification for pulmonary aspiration is probably the single greatest modifiable factor in anesthesia practice to reduce aspiration, almost certainly of greater importance than the ongoing cricoid pressure debate – which may never be conclusively resolved.
Daniel Jolley
What did they do?
Markley et al. conducted a single-center retrospective cohort study of 23 years of data from a tertiary North American academic hospital. The investigators identified 129 patients meeting criteria, requiring elective Cesarean delivery (CD/CS) for suspected morbidly adherent placenta (MAP): placenta accreta, increta or percreta.
Why the fuss?
Historically there has been concern that neuraxial anaesthesia may add additional complexity when managing a major haemorrhage associated with MAP CS, by:
And they found...
The majority of patients with morbidly adherent placentas can be safely managed with neuraxial anesthesia alone. GA conversion was also safe for those requiring it.
Of the 129 patients, 5% were electively given a GA. Of the 122 (95%) who received neuraxial anesthesia (NA), only 15 (12%) were converted to GA after delivery.1 There were three difficult intubations (AFOI, VL and bougie each) among the 22 GAs. NA was predominately combined-spinal epidural or epidural.
Of the 72 patients requiring hysterectomy, 21% (15) needed NA-GA conversion.
The only independent predictors for GA conversion were history of ≥3 previous CS and long surgical duration.
The big question
Although retrospective, this data again reassures that neuraxial anesthesia can be a safe and appropriate choice for cesarean delivery with placenta accreta, increta or percreta. The big question will be whether you are happy managing an emergent NA-GA conversion and intubation in the 1-in-8 requiring it (or 1-in-5 with hysterectomy) or plan for an elective GA pre-surgery.
Daniel Jolley
What did they do?
Tamura and team randomised 176 elective CS patients to spinal anaesthesia with or without morphine, in addition to placebo or ultrasound-guided quadratus lumborum block (QLB).
And they found
Only intrathecal morphine significantly improved analgesia, not QLB whether performed with or without spinal morphine. Thus QLB probably does not improve analgesia further beyond current best practices.
Not so fast...
While this modest-sized RCT concluded that QLB did not improve pain after caesarean section, the conclusion is i) somewhat inconsistent with earlier studies that did show benefit, and ii) the adjuvant analgesic regime1 used may not be applicable to practice outside Japan.
Daniel Jolley
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.
Daniel Jolley