What's the story here?
Growing evidence points to significant anti-depressant effects of several anesthetic agents, including ketamine, nitrous oxide, propofol and isoflurane. These may provide avenues for use as novel antidepressants or lead to development of new agents, supplanting other therapies such as ECT.
Why is this important?
Major depression and its consequences contributes to significant disease burden worldwide. Depression prevalence is increasing globally, with one third suffering treatment-resistant depression, unresponsive to modern antidepressant drugs.
Isoflurane when administered to achieve burst suppression (1.5-2 MAC) may have antidepressant effects in 75% of those treated, and achieved full remission in 50% in one 2013 study, comparable to ECT but with fewer cognitive side effects.
N2O use in one small pilot study resulted in depression improvement, likely through similar mechanisms as ketamine. Similarly, propofol-induced burst suppression has also shown an antidepressant effect similar in magnitude to isoflurane.
Bottom line: Several anesthetic agents appear to offer significant antidepressant benefits, which may lead to more mainstream use and supplant ECT. Anesthesiologists will be need to be aware of these effects as they become involved in their provision.
ICU resuscitation with 20% ‘concentrated’ albumin decreases fluid requirements compared with 4% albumin, without apparent harm.
Pulse Pressure Variation and Stroke Volume Variation has limited sensitivity and specificity when assessing the response to intra-operative fluid challenge.
It’s likely safe to continue metformin and sulphonylureas in those fasting for day surgery, in the absence of renal impairment.
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.
It's probably safe and beneficial to continue metformin and sulphonylureas perioperatively in those having ambulatory day-surgery with normal renal function.
In children single-agent antiemetic prophylaxis is as equally effective as TIVA in preventing post-operative vomiting.
Important caveats to temper our sugammadex enthuasiasm...
- Sugammadex is still cost-prohibitive for many health systems.
- Although neuromuscular reversal is demonstrably better than for neostigmine, sugammadex use does not obviate the need for neuromuscular monitoring (Kotake 2013: Reversal with sugammadex in the absence of monitoring did not preclude residual neuromuscular block).
- Sugammadex is an important option to consider in a CICO crisis, but it is not a ‘Get Out of Gaol Free’ card (Kyle 2012: A persistent 'can't intubate, can't oxygenate' crisis despite rocuronium reversal with sugammadex).
- Sugammadex is now the leading cause of perioperative anaphylaxis in Japan, and we have likely underestimated the risk of sugammadex hypersensitivity. (see: Sugammadex anaphylaxis: all that glitters?).
Is the conventional assumption that left-lateral tilt and uterine displacement avoids aortocaval compression during Caesarean section actually valid?
50 years of assumed orthodoxy is challenged by studies showing that:
- True aortal compression is relatively uncommon (Higuchi 2015, Lee 2012).
- Caval compression is probably near-universal, but also usually not improved by a mere 15 degree tilt. (An impractical 30 degrees is more likely required for meaningful impact!) (Palmer 2015).
- Caval compression probably has limited haemodynamic or fetal consequences in the fit, well, term parturient (Higuchi 2015; Lee 2012).
- Judicious use of vasopressor infusions may obviate the need for traditional uterine displacement (Lee 2017; Farber 2017).
Time to change practice then?
Not quite yet...
Duration of rocuronium action directly correlates with BMI.
Intraoperative dexamethasone reduces the incidence of postoperative sore throat for up to 24 hours and postoperative hoarseness for 1 hour.