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Posts tagged Perioperative medicine.

The importance of non-inferiority and equivalence

Three papers from the first BJA of the new decade highlight the importance of non-inferiority: protective ventilation strategies, dexamethasone for prolonging interscalene blocks, and high inspired oxygen and surgical site infections.

Although none investigated new questions, they all represent studies into areas of ongoing uncertainty. They are each a useful reminder that most perioperative interventions do not significantly improve outcomes, although the majority of these probably do not ever make it to publication.

Lung-protection and atelectasis

Généreux et al. investigated the atelectasis-preventing benefit of a common protective ventilation strategy (PEEP and regular recruitment manoeuvres). Notable not just because there was no difference in atelectasis after extubation, but because the use of ultrasound to measure atelectasis helped to better track the intraoperative and post-extubation changes between the intervention and control groups. [→ article summary]

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Small Changes & Protection: antihypertensives, cognitive decline and ischaemic preconditioning

Metajournal on Small Changes & Protection: antihypertensives, cognitive decline and ischaemic preconditioning

Three interesting articles that appeared in the past few months, all following a common theme of ‘protection with small changes’. Although only one is itself practice changing, together they challenge us to continue to look to how small practice changes may have significant protective and preventative effects in the lives of our patients.

Antihypertensives evening dosing

Hermida et al. (2019) published impressive results from the massive, 10-year Hygia Project, which randomised almost 20,000 patients to take anti-hypertensive medications at bedtime or awakening.

Not only did patients who took antihypertensives (of any class) in the evenings have better blood pressure control, they also received a 45% reduction in major cardiovascular outcomes, including CVD death, infarct, coronary revascularisation, heart failure and stroke!

Given that many critical care doctors briefly touch on the medications their patients are taking, a simple “you should ask your primary physician about when its best to take your blood pressure tablets” could have a disproportionately large impact on patient health.

Read on for protection with intravenous lidocaine and ischaemic conditioning...

The Cardiology Referral: Avoid hypoxia, avoid hypotension?

Recently I needed to refer a patient preoperatively to a cardiologist for review. This is not an uncommon situation – one which happens thousands of times every week throughout the world. And yet it is a referral that anesthesiologists and anesthetists often do very poorly.

Avoid hypoxia, avoid hypotension?

We sometimes roll our eyes at recommendations made by physician colleagues: either providing unhelpful physiological parameters that we normally aim to maintain anyway (“avoid hypoxia?”), or stepping outside their expertise and boxing the anesthetist in by suggesting specific anesthetic techniques (“okay for a spinal”).

It is easy to be annoyed at both the lack of value this adds to our perioperative planning, as well as to the nonchalant ignorance of intraoperative medicine that it betrays. At the end of the day though, it’s our fault.

As Dr Andrew Silvers, a Melbourne cardiac and neuro-anesthetist recently opined, if your cardiologist replies with “avoid hypoxia and avoid hypotension” then YOU the anesthetist or anesthesiologist are at fault for not asking your cardiology colleague specific questions that will materially effect your perioperative planning.

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Metoclopramide: it actually works!?

Metoclopramide had long been written off by many anesthetists and anesthesiologists, aware of trials and meta-analyses that show no or limited effect in treating or preventing nausea and vomiting – in particular limited ability to prevent post-operative nausea and vomiting (PONV). Most recently Henzi, Walder and Tramèr (1999) were able to show only very limited benefit for metoclopramide 10 mg in preventing vomiting and no significant effect in preventing nausea in adults.1,2,3

What is metoclopramide?

Metoclopromaide is a benzamide, predominately used for antiemesis and its gastric prokinetic effect. It is marketed under the names Maxalon®, Pramin® and Reglan® in various countries. Although considered an old drug its antiemetic action was first identified in 1964 by French doctors Justin-Besançon and Laville.3 (In contrast the analgesic tramadol is often considered a "modern" drug outside of Europe, but was launched by Grünenthal GmbH in 1977.)

Metoclopramide readily crosses the blood-brain barrier where it mediates anti-emetic effects primarily as a dopamine D2 antagonist in the chemoreceptor trigger zone (CTZ – located in the area postrema of the 4th ventricle). Metoclopramide also has mixed 5-HT3 receptor antagonist and 5-HT4 receptor agonist actions. The former may contribute to anti-emesis at higher doses and the later to its pro-kinetic effects. Muscarinic cholinergic actions have also been identified, both through increasing acetylcholine release and by increasing receptor sensitivity to acetylcholine in the upper GI tract – further contributing to the pro-kinetic effect.

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  1. Henzi I, Walder B, Tramèr MR. Metoclopramide in the prevention of postoperative nausea and vomiting: a quantitative systematic review of randomized, placebo-controlled studies. Br J Anaesth. 1999 Nov;83(5):761-71. 

  2. It's also interesting to note that there was no dose responsive effect regardless of route. NNT to prevent early (<6h) and late (<48h) vomiting were 9.1 (95% CI 5.5-27) and 10 (6-41) respectively. In children the best documented regimen was 0.25 mg/kg. NNT to prevent early vomiting was 5.8 (3.9-11); there was no effect on late vomiting. There was only a single documented case of extrapyramidal side effects out of 3260 patients, giving an incidence of 0.03%. 

  3. Justin-Besançon L, Laville C.C R Seances Soc Biol Fil. 1964;158:723-7. 

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