Created May 18, 2020, last updated 19 days ago.
Collection: 122, Score: 154, Trend score: 0, Read count: 155, Articles count: 5, Created: 2020-05-18 02:08:30 UTC. Updated: 2021-02-07 07:13:10 UTC.
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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."
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
We reviewed the literature on obstetric failed tracheal intubation from 1970 onwards. The incidence remained unchanged over the period at 2.6 (95% CI 2.0 to 3.2) per 1000 anaesthetics (1 in 390) for obstetric general anaesthesia and 2.3 (95% CI 1.7 to 2.9) per 1000 general anaesthetics (1 in 443) for caesarean section. Maternal mortality from failed intubation was 2.3 (95% CI 0.3 to 8.2) per 100000 general anaesthetics for caesarean section (one death per 90 failed intubations). ⋯ A prospective study of obstetric general anaesthesia found that transient maternal hypoxaemia occurred in over two-thirds of cases of failed intubation, usually without sequelae. Pulmonary aspiration occurred in 8% but the rate of maternal intensive care unit admission after failed intubation was the same as that after uneventful general anaesthesia. Poor neonatal outcomes were often associated with preoperative fetal compromise, although failed intubation and lowest maternal oxygen saturation were independent predictors of neonatal intensive care unit admission.
The obstetric airway is a significant cause of maternal morbidity and mortality. Endotracheal intubation is considered the standard of care but the laryngeal mask airway (LMA) has gained acceptance as a rescue airway and has been incorporated into the obstetric airway management guidelines. In this randomized controlled equivalence trial, we compared the Supreme LMA (SLMA) with endotracheal intubation (ETT) in managing the obstetric airway during cesarean section. ⋯ SLMA could be an alternative airway management technique for a carefully selected low-risk obstetric population, with similar insertion success rates, reduced time to ventilation and less hemodynamic changes compared with ETT. Our findings are consistent with the airway guidelines in recommending the second-line use of LMA in the management of the obstetric airway.
The Supreme™ laryngeal mask airway (SLMA) is a single-use LMA with double lumen design that allows separation of the respiratory and the alimentary tract, hence potentially reducing the gastric volume and risk of aspiration. The purpose of this prospective cohort study is to evaluate the the role of the SLMA as an airway technique for women undergoing category 2 and 3 Cesarean delivery under general anesthesia. ⋯ The SLMA could be an alternative effective airway in category 2 and 3 parturients emergency Cesarean Delivery under general anesthesia in a carefully-selected obstetric population.
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