Article Notes
- Safety concerns regarding respiratory depression cannot be ignored, and because managing this relies upon staff vigilance, increased PCA use may conversely lead to a normalisation of risk and institutional complacency, rather than safety improvement.
- Analgesia is still inferior to epidural, even if maternal satisfaction is comparable.
- Technique acceptability might not be as good in communities with high pre-existing epidural use.
Accurately identifying the cricothyroid membrane is foundational for front-of-neck rescue of airway misadventure. Yet the very patients who are at risk of a cannot intubate, cannot oxygenate scenario (eg. obese, neck pathology) are also likely to make identifying the cricothyroid membrane (CTM) difficult.
Naveed and co. compared the accuracy of CTM palpation to ultrasound in a single-blinded randomized trial of 223 patients, with poorly defined landmarks, undergoing CT neck.
The ultrasound group showed a 10-time greater success in identifying the CTM (correct within 5 mm of actual; 81% vs 8%), along with a 5-times smaller mean distance from actual to estimated, than did the palpation group.
So what's the take home?
Given the wide-availability of ultrasound and it's acceptability to patients, any pre-induction marking of the CTM in an anticipated difficult airway should employ neck ultrasound in all but the most obviously-palpable necks.
In an emergent CICO situation, neck ultrasound likely has utility, though at the potential cost of procedural complexity and delay.
Daniel Jolley
The more I think about these results, the more interesting it is.
Reducing instrumental delivery rate is a real benefit for women, though is this due to avoiding epidurals or some other difference? How do we balance the issues of safety, analgesia, perineal trauma and maternal satisfaction? And how do we communicate this to labouring women in a meaningful way?
Questions questions...
Daniel Jolley
What did they do?
Wilson et al randomized 401 laboring women across multiple centers to either remifentanil PCA or pethidine/meperidine IM, then compared the progression of these women to labour epidural.
On the surface... this might appear disingenuous, as it compares remifentanil PCA to widely-shown-to-be-ineffective parenteral pethidine – rather than to the gold standard labour epidural. But it's also a study of how the technique might practically be used in the real world.
What they found
Women with remifentanil PCA progressed half as often to require epidural analgesia than those receiving pethidine (19% vs 41%).
Though it's one of the secondary findings that is most interesting: the remifentanil group were less likely to need instrumental delivery (15% vs 26%).
But don't get carried away
Despite the demonstrated superiority of remi PCA to pethidine, the technique is not without it's issues:
And finally... why are we so eager to do away with the labour epidural? Serious complications are very uncommon to rare, the technique is widely acceptable to women, and it is more effective than any other modality.
Is this change driven by the needs of pregnant women, or the health system's limited resources?
Daniel Jolley
What did they do?
Using a randmoized, double-blind crossover study, Fong et al anaesthetized eight male volunteers twice with 1.2% isoflurane for 1 hour, after propofol induction. In the final 10 minutes subjects were randomized to IV caffeine or placebo. No opioids were administered.
Receiving IV caffeine hastened emergence by over 40%, as measured by BIS and psychomotor testing.
Return of gag reflex was used as the marker of emergence, although time to emergence was consistent with eye opening and BIS.
How much caffeine did they give?!?
15 mg/kg of caffeine citrate, equivalent to 7.5 mg/kg of base caffeine – the same caffeine as in two large cups of coffee for a 70 kg male.
Come on, surely this isn't that important?
Although the mean 7 min difference may not appear clinically significant, especially when using more modern volatiles, this study is a good proof of concept of how caffeine may be a useful clinical tool when faced with delayed emergence after anesthesia and for patients at greatest risk of persistent psychomotor depression post-anesthesia, such as the elderly.
Daniel Jolley