British journal of anaesthesia
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The under-representation of women in academic leadership roles, including in anaesthesiology, is a well-documented phenomenon that has persisted for decades despite more women attending medical school, participating in anaesthesiology residencies, and joining academic faculties. The percentage of female anaesthesiologists who hold senior academic ranks or leadership roles, such as chair, lags behind the percentage of female anaesthesiologists overall. Trends towards increasing the numbers of women serving in educational leadership roles, specifically residency programme directors, suggest that there are areas in which academic anaesthesiology has been, and can continue, improving gender imbalance. Continued institutional efforts to recruit women into anaesthesiology, reduce gender bias, and promote interventions that foster gender equity in hiring and promotion will continue to benefit women, academic anaesthesiology departments, and the healthcare system overall.
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Why is this important?
Hypotension associated with spinal anaesthesia for Caesarean section is common. Increased interested over the past decade has resulted in some consensus recommending phenylephrine infusions, however there are few studies that directly compare this to other vasopressors.
What did Singh and team do?
By analysing 52 high-to-moderate quality RCTs and over 4,000 patients, Singh performed a Bayesian network meta-analysis to indirectly compare various vasopressors.
It's notable that umbilical artery base excess was used as the primary outcome, although other neonatal and maternal outcomes (nausea, vomiting, bradycardia) were secondarily assessed. Nonetheless, this study prioritised the fetal effects of hypotension management.
"We selected umbilical arterial BE as our primary outcome because it is thought to represent the effect of pronounced fetal hypoxaemia, anaerobic metabolism, and accumulation of non-volatile acids, that is the metabolic component of acidaemia."
Ok, what's a Bayesian network meta-analysis anyway?
A network meta-analysis compares trial interventions indirectly, when researchers are interested in a comparison between two factors (eg. use of metaraminol vs phenylephrine) that have not been directly compared by included RCTs (eg. a study comparing metaraminol vs ephedrine, and a study of phenylepherine vs ephedrine). A Bayesian NMA allows simultaneous comparison of multiple-arm trials, considering prior probability along with the likelihood of outcome rank between interventions.
A Bayesian NMA acknowledges the uncertainty of research conclusions and the probabilistic nature of clinical decision making.
Singh concluded...
Norepinephrine (noradrenaline), metaraminol, and mephentermine showed the lowest likelihood of adverse neonatal acid-base effects, and ephedrine the greatest.
"...norepinephrine, metaraminol, and mephentermine had the lowest probability of adversely affecting the fetal acid-base status as assessed by their effect on umbilical arterial base excess (probability rank order: norepinephrine > mephentermine > metaraminol > phenylephrine > ephedrine)."
When combined, there was a 66% probability that norepinephrine & mephentermine are the best agents for supporting umbilical a. BE.
There was a 66% probability that metaraminol is the best treatment for optimising umbilical artery pH, an 85% combined-probability that metaraminol & norepinephrine are best for umbilical a. pCO2, and 85% that they are the two best agents for avoiding maternal nausea and vomiting.
Be smart
Given the very nature of meta-analyses and the challenge of indirect comparison among agents from heterogenous studies, the conclusions are only suggestive of the benefits of phenylephrine alternatives. A large RCT is still needed! (And despite it's popularity in some countries, there are still only a small number of trials of metaraminol.)
Nevertheless, other than for bradycardia, ephedrine was most likely the worst for all outcomes, reinforcing past conclusions that there are better pressor choices.
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Randomized Controlled Trial
A randomised double-blind dose-response study of weight-adjusted infusions of norepinephrine for preventing hypotension during combined spinal-epidural anaesthesia for Caesarean delivery.
Norepinephrine (noradrenaline) infusion at 0.08 μg/kg/min prevents spinal-associated hypotension during cesarean section in 90% of patients, although increasing dose increases reactive hypertension.
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Multicenter Study
Integration of the Duke Activity Status Index into preoperative risk evaluation: a multicentre prospective cohort study.
The Duke Activity Status Index (DASI) questionnaire might help incorporate self-reported functional capacity into preoperative risk assessment. Nonetheless, prognostically important thresholds in DASI scores remain unclear. We conducted a nested cohort analysis of the Measurement of Exercise Tolerance before Surgery (METS) study to characterise the association of preoperative DASI scores with postoperative death or complications. ⋯ A DASI score of 34 represents a threshold for identifying patients at risk for myocardial injury, myocardial infarction, moderate-to-severe complications, and new disability.
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Review Meta Analysis
Intravenous lidocaine to prevent postoperative airway complications in adults: a systematic review and meta-analysis.
Cough: why care?
Although often minor, common post-operative complications have by definition a broad impact on the perioperative experience. Some common complications, such as coughing on extubation, can also have significant surgical consequences such as for neurosurgical or ophthalmic procedures.
Both coughing on extubation (reported incidence 15-94%) and post-operative sore throat (21-72%) are very common among surgical patients.
What did they do?
Yang and team performed a high-quality meta-analysis of RCTs investigating the effect of intravenous lidocaine/lignocaine on coughing at extubation. Many of these trials also looked at further secondary effects, such as post-operative sore throat. They included 16 trials, totalling 1,516 subjects. Although the trials demonstrated significant heterogeneity, subgroup analyses still confirmed the study's findings.
And they found...
There was significant reduction in cough RR 0.64 (0.48-0.86 & NNT=5), and post-operative sore throat RR 0.46 (0.32-0.67), though no difference in laryngospasm, adverse events or time to extubation with modern volatile agents.
Analysing various lidocaine timings (pre-operative vs intra-operative) and dose ranges (low <1.5mg/kg or high >1.5 mg/kg) yielded no evidence of clear advantage. Nonetheless the findings are consistent with previous reviews, such as from Clivio et al. (2019) showing lidocaine 1.5 mg/kg reduced cough (RR: 0.44; 0.33–0.58), and that the effect is probably dose responsive.
Ok, but how does lidocaine work?
The mechanism of action reducing cough is not understood, although several possibilities have been proposed, including...
"...the suppression of airway sensory C fibres, the reduction of neural discharge of peripheral nerve fibres, and the selective depression of pain transmission in the spinal cord."
Bottom-line
Peri-operative intravenous lignocaine effectively reduces coughing on extubation and reduces post-operative sore throat, without any increase in adverse events.
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