British journal of anaesthesia
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LMA and Caesarean – why should I care?
There is a small attitude change underway in the use of supraglottic airway devices (SGA) in obstetric anaesthesia. While there is already an appreciation of their role in obstetric airway rescue, we now see a shift in some countries to use an SGA as the primary airway choice for Caesarean section under general anaesthesia.
Anaesthesiologists need to be aware of this attitudinal shift, and importantly appreciate the inherent compromises and uncertainties driving it.
In this editorial, Metodiev & Mushambi review changing attitudes toward obstetric airway preference, the realities of maternal aspiration risk, and several large studies suggesting acceptable safety when using a SGA for Caesarean GA.
The tension between airway and aspiration
It is well accepted that regional anaesthesia for Caesarean section is overwhelmingly the best choice, driven first by the historical experience of maternal general anaesthesia risk. The very features that underline this safety improvement are also those in tension when considering endotracheal intubation or SGA: risk of failed intubation versus aspiration.
Studies showing safety
Several retrospective, prospective and randomised studies totalling more than 8,000 patients have concluded that in these populations, SGA use (mainly 2nd generation devices, such as ProSeal™ or LMA Supreme™) was not associated with any greater risk of aspiration. This includes both the single largest study investigating 3,000 women (Halaseah 2010), and two RCTs (Yao 2019 & Li 2017), none of which identified any cases of aspiration (although there was a single regurgitation).
So on the surface, SGA use appears arguably safe, particularly with careful patient selection. Among the studies, generally obese patients and those with reflux were excluded, muscle relaxants were frequently used, an orogastric tube was inserted, and cricoid pressure was used at least for some periods of airway intervention.
And yet we do know from NAP4 (2011) that aspiration is a real danger, accounting for 50% of anaesthesia-related deaths.
Is gastric ultrasound the answer?
No. Next question... 😉
While gastric ultrasound shows some utility in quantifying residual gastric volume, it is 1. Not possible to equate this to aspiration risk in pregnant patients, 2. Technically difficult in the pregnant patient.
They conclude that...
"...there is insufficient evidence to recommend universal or selective replacement of tracheal tubes with SGA devices during general anaesthesia for Caesarean delivery. Aspiration remains the main concern."
Be smart
And before you get too excited by the lack of observed aspiration in these large studies, as Metodiev & Mushambi note, many of the studied populations were Asian and Middle Eastern, having different diets and obesity prevalence than Europe, Oceania and North America.
summary -
Finger-cuff derived blood pressure & CO/CI measurement shows some accuracy when compared with invasive methods, however too much heterogeneity exists among studies for it to be reliably interchangeable.
pearl -
The world is currently facing an unprecedented healthcare crisis caused by a pandemic novel beta coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The pathogen is spread by human-to-human transmission via droplets exposure and contact transfer, causing mild symptoms in the majority of cases, but critical illness, bilateral viral pneumonia, and acute respiratory distress syndrome (ARDS) in a minority. ⋯ This article presents a summary of learning points in epidemiological infection control from the SARS epidemic, alongside a review of evidence connecting current understanding of the virologic and environmental contamination properties of SARS-CoV-2. We present suggestions for how personal protective equipment policies relate to the viral pandemic context and how the risk of transmission by and to anaesthetists, intensivists, and other healthcare workers can be minimised.
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Multicenter Study Observational Study
Myocardial infarction after noncardiac surgery in Sweden: a national, retrospective observational cohort study.
The precise incidence of perioperative myocardial infarction (MI) after noncardiac surgery remains unclear. We determined the incidence and risk factors for perioperative MI after noncardiac surgery and the risk of MI and mortality compared with matched non-surgical patients. ⋯ In a large Swedish surgical cohort, the incidence of MI within 30 days of noncardiac surgery was 0.41%, chiefly occurring in a small subset of higher risk patients.