Neuraxial morphine does not have a protective effect on headache after unintentional dural puncture.
Why should you care?
Not only is venous cannulation a common procedure, but so is resultant thrombophlebitis – occurring in up to 75% of patients. This has important morbidity, patient-experience and economic consequences.
What does this study add?
Although many risk factors have been identified (insertion sterility, location, access technique, drug use, micro-particles, etc.), Villa and friends investigated whether in-line filters would reduce phlebitis incidence.
This modest, single-center trial randomized surgical patients between in-line filter (for 96 hours) or standard line, before anesthesia induction. Filter user reduced thrombophlebitis 13-fold at 48 hours, and at 96 hours sustained potency of 50% more of the cannulae.
What sort of filters did they use?
They used an 11 cm2 positively-charged 0.2 µm filter for fluid and most drugs, a 4.5 cm2 1.2 µm filter for propofol infusions, and a positively-charged 1.65 cm2 0.2 µm for opioid infusions.
The filters did slow gravity-fed infusion rates as they aged, however this was not clinically significant when using a peristaltic pump.
We should be better stewards of our patient's IV access. For short-term access <48h focus should be on technique and sterility, but for access needed for 48h or longer, an inline filter offers significant benefit with limited downside.
Finally some evidence to show the inaccuracy of palpation in rescue FON access! This will potentially change my practice. Now I'm more inclined to pre-site the CTM via ultrasound in patients with no necks prior to induction.
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.
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?
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:
- 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.
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?
Intraoperative corticosteroids may decrease postoperative complications, including infection, after major surgery.
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.
Although slightly lowering 5 minute Apgar scores, opioids used to attenuate the maternal pressor response to intubation did not have clinically significant effects on neonates.
Local anesthetic myotoxicity may be clinically significant, particularly with bupivacaine, at higher LA concentrations and with longer exposure.