ESRA UPDATES journal club invites leading experts in (regional) anaesthesia to select one (or more) article(s) which for him/her were/are important, interesting or changed his/her clinical practice. This choice can be a general big randomized study but can also be very personal. For this edition our choice went to Maria Paz Sebastian.
Dr. Maria Paz Sebastian is a consultant in anaesthetics and acute pain at the Royal National Orthopaedic Hospital (RNOH) NHS Trust since 2015. After graduating and completing her anaesthetic training in Madrid, she worked as Consultant Anaesthetist in Bilbao. Maria undertook the regional anaesthesia fellowship at University College London Hospital and she is currently the Regional Anaesthesia Lead at RNOH. Maria is extremely passionate about teaching ultrasound and regional anaesthesia. She was awarded on the ESRA educational video competition 2019. Maria was elected council member of RAUK in 2020, where she is the Lead for Equality and Diversity and is working on supporting and advancing the role of women in regional anaesthesia.
So many interesting papers have shaped the way I perform regional anaesthesia that it has been very difficult to choose just a few. In the end, I have selected papers which support some very specific parts of my practice; I hope they might provide some food-for-thought.
The first paper I would like to focus on is The Second ASRA Practice Advisory on Neurologic Complications Associated with Regional Anesthesia and Pain Medicine: Executive Summary 2015 (1). This practice advisory reviews the published evidence and condenses findings and recommendations on perioperative neurological complications.
Many important points are summarized on this paper. Among them, I would like to highlight one which influenced what I consent patients for.
Despite our concerns regarding the risk of nerve damage when performing blocks, this review did not find peripheral nerve blocks to be an independent risk factor for perioperative nerve injury. However, the review found enough evidence to support an association between nerve damage and general anaesthesia and epidural techniques.
The most recent paper published studying the incidence and aetiology of postoperative neurological symptoms after peripheral nerve block (2), supports this conclusion. Lam KK, et al. carried out a retrospective cohort study of 19219 patients. They found the incidence of prolonged (>10 days) postoperative neurological symptoms (PONS) related to peripheral nerve blocks to be 0.2:1000 whilst the incidence of PONS from all causes was 1:1000.
Some patient characteristics and surgical factors further influence the risk of PONS (1) but it is clear that patients should be consented for the risk of nerve injury regardless of the anaesthetic technique used.
The next topic I would like to focus on is the type, volume and concentration of local anaesthetic (LA) used when performing peripheral nerve blocks. We usually base our decision on the desired onset and duration of analgesia or anaesthesia.
It has been demonstrated that the mass of LA, rather than the volume and concentration, is the determining factor of the nerve block’s onset and duration (3-5). However, it seems that beyond a certain threshold, increases in LA mass produce very little or no increase in onset speed or duration of analgesia (5-6).
Nader A. et al. (5) hypothesized that this threshold corresponds with the dose at which the ion channels along a predetermined length of the nerve are bound with LA molecules. By the time these ion channels are free again, the remaining LA molecules have been “washed” from the surrounding tissues and won’t be available to bind ion channels and prolong the blockade.
This theory is based on the results of their double-blinded and randomized dose-ranging study (5), which analyses the success and duration of ultrasound-guided and nerve-stimulator–assisted sciatic nerve block using 2.5 ml to 30 mL of 0.5% ropivacaine and 0.5% bupivacaine on 139 patients.
They found that volumes of 10 to 30 ml had similar onset times, block duration and postoperative pain scores and analgesia consumption, while lower volumes than 10 ml were associated with longer time to complete successful blockade and with a dose-dependent decrease in block duration.
Other examples demonstrating this threshold effect for different blocks can be found in the literature. Riazi S. et al. (7) randomized forty patients to receive an ultrasound-guided interscalene brachial plexus block of either 5 or 20 ml of ropivacaine 0.5%. They found no significant differences in pain scores, sleep quality, and total morphine consumption up to 24h after surgery between both groups.
Therefore, the use of high volumes of high concentration LA seems unnecessary to prolong analgesia and may increase the risk of LAST and/or nerve damage; LA neurotoxicity seems to be concentration dependent (1).
The last paper I would like to comment on is a meta-analysis of randomized controlled trials studying the use of a single dose of perioperative dexamethasone on postoperative pain and opioid consumption (8). They analysed 24 studies with a total of 2,751 subjects having a wide range of surgeries.
Dexamethasone at doses of 0.1mg/kg or lower failed to show an opioid sparing effect. On the other hand, doses higher than 0.1 mg/kg were found to reduce postoperative pain and opioid consumption in the first 24h without an increase in rates of wound infection or delayed wound healing.
Although the low doses of dexamethasone typically used to prevent postoperative nausea and vomiting do not seem to provide analgesic benefit, this study implies that increasing the dose to 0.11mg/kg may decrease post operative pain and opioid consumption.
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