Article Notes
- Remifentanil infusions above 0.20-0.25 μg/kg/min are associated with hyperalgesia (OIH = Opioid Induced Hyperalgesia) and tolerance (AOT = Acute Opioid Tolerance) respectively.
- Some of these effects can be mitigated by multimodal analgesia (notably ketamine), and possibly by gradual weaning of a remifentanil infusion.
- The findings have been predominately identified in rats and volunteer human studies. The clinical and longterm significance is still uncertain.
- Although OIH and AOT arise from different physiological mechanisms, they are clinically difficult (if not impossible) to differentiate.
- The clinical priority for management is prevention.
Take this one with a large grain of salt. At best it shows cerebral perfusion was safely maintained in this small cohort of patients receiving a rather unique, though not personalized, anesthetic recipe.
It’s very unlikely that this 22 patient observational study is sufficiently powered to reassure concerns that prone positioning does not effect cerebral blood flow, although it does point in that direction.
Daniel Jolley
Daniel Jolley
One of the earliest published case series linking post-operative hepatic necrosis to halothane anaesthesia.
We now know this occurs in about 1 in 10,000-30,000 adult halothane anaesthetics, and 1 in 60,000 in children, with a historical mortality of 30-70%. In 20% of cases the hepatitis is mild and self-limiting.
Daniel Jolley
An infamous article from 1985 that investigated the relationship between perioperative myocardial ischaemia and postoperative myocardial infarction in 1,023 elective CABG patients. The study findings are broadly consistent with our understanding that increasing myocardial oxygen demand in those with coronary artery disease is undesirable.
Although there are unsurprising problems with this 35 year old article, it is best known for the infamous anesthesiologist number 7 who subjected his/her patients to disproportionately more postop infarcts, along with tachycardia and hypertension.
Final word? Don’t be a number 7 anesthesiologist...
Daniel Jolley
What did they do?
Kowark and friends randomised 343 patients across four German hospitals to receive desflurane, sevoflurane or propofol for maintenance anesthesia using a laryngeal airway for surgery expected to be up to 2 hours.
And they found?
There was no difference in airway reactions among the three groups, and the desflurane patients emerged (statistically) significantly faster.
Hang on...
But the difference in emergence times was, i) at most only 2 minutes, and ii) was a surrogate marker for what actually matters – when a patient leaves the PACU or hospital – which wasn't reported.
Additionally, the study protocol very prescriptively defined when volatiles were decreased (50% at 5 min before expected surgical finish) and ceased – the same for both Des and Sevo. Yet it is common practice to begin weaning Sevo earlier than Des if trying to achieve comparable emergence.
Could this even be applied to my patients?
Probably not. Unless you are in the habit of using remifentanil infusions (0.15 mcg/kg/min) for surgery that almost certainly does not justify its use and have access to uniquely European analgesics piritramide and metamizole.
The elephant in the room...
Why do we persist in trying to find new justifications for desflurane, given its expense and high environmental costs? (And for that matter, remifentanil?!).
This study demonstrates the well known faster pharmacokinetics of desflurane during an unnecessarily complex laryngeal mask anesthetic, and yet adds little to meaningful clinical outcomes.
Daniel Jolley
Also see Carbon Footprint from Anaesthetic gas use [pdf] from the UK’s Sustainable Development Unit.
Daniel Jolley