Article Notes
This update to their 2011 meta-analysis supports their conclusion that aspirin modestly reduces myocardial infarction when used for primary prevention, but at the expense of increased risk of intracranial and major bleeding.
Why is this important?
6% of the world's population has diabetes mellitus, making it one of the most common perioperative comorbidities. Withholding oral-hypoglycaemics pre-op is common, but worsens glucose control and so may increase post-op complications.
What did they find?
Ambulatory patients who had their metformin and/or sulphonylurea OHG agents continued perioperatively had better glucose control.
Be cautious as this was a relatively small study, and not adequately powered to compare hypoglycaemia rates or (ridiculously) rare complications such as lactic acidosis. Additionally, no investigation was made of post-op complications, instead using glucose control as a surrogate outcome.
Bottom line
It's probably safe and beneficial to continue metformin and sulphonylureas perioperatively in those having ambulatory day-surgery with normal renal function.
This is a very significant and large study, and should give us pause to ponder the consequences of invasive airway management and surgery requiring muscle relaxation. It is also important to note that qualitative neuromuscular monitoring (as opposed to quantitative) appears to offer no risk reduction, consistent with other research in this area.
Nonetheless, the retrospective nature of this study means these relationships should not necessarily be viewed as causal. This is not a study of an intervention per se, but the association between certain perioperative characteristics that may be unavoidable (e.g. using muscle relaxants).
An important paper for any concerned anaesthetist or anesthesiologist to read in full.
Carbetocin is a long-acting synthetic oxytocin analog. Although a 100 mcg dose is currently recommended, there is still some question as to the ideal dose. Dosing as low as 20 mcg may possibly be equally effective.
Carbetocin is currently only recommended for use during elective cesarean delivery, obviating the need for a post-operative oxytocin infusion currently practiced in many countries. In some countries it is also used after vaginal delivery.
It is at least as efficacious as intravenous oxytocin, and may possibly be superior at reducing postpartum haemorrhage.
Due to it's comparatively high cost compared with oxytocin however, the economic benefit of avoiding post-operative oxytocin infusions has not been demonstrated.
In the scenario of emergency cesarean section after labor augmentation with oxytocin, a much larger dose is likely required and carbetocin cannot be recommended.
One study has suggested a post-operative analgesic benefit of carbetocin vs oxytocin, although the evidence base for this is far from conclusive.
Another useful review of neuraxial tranexamic acid, although not indexed by pubmed. Full-text below:
Gupta et al., Tranexamic acid: Beware of anaesthetic misadventures, J Obst Anaesth Crit Care 2018.
Murphy et al. showed in this randomised, non-blinded trial that patients monitored with quantitative acceleromyography before extubation experienced less PORC, less desaturation below 90% (0% versus 21%) and less airway obstruction (0% versus 11%) during transport to the PACU.
Once in the PACU these patients also experienced less frequent, shorter duration and less severe hypoxic events.
The 5-second Head Lift Test and the Tongue Depressor Test, often used to detect PORC in the PACU are of limited use for detecting TOFR < 0.9, having sensitivities of only 11% and 13% and specificities of 87% and 90% respectively.
The Head Lift Test cannot identify POCR with a TOFR > 0.5. Debaene’s study population demonstrated Positive and Negative Predictive Values of the Head Lift and Tongue Depressor Tests of only 53-58%!
Subjective, qualitative neuromuscular monitors fare no better: Tactile TOF Fade and Double Burst Stimulation (DBS) have similar sensitivities (11% and 13% respectively), although high specificities (99% each). This provides a good Positive Predictive Value (93% & 97%) but a very poor Negative Predictive Value (57% & 58%) (depending on the incidence of PORC).