Comparison of apnoeic oxygen techniques in term pregnant subjects: a computational modelling study

Effectiveness of preoxygenation strategies: a systematic review and network meta-analysis

BACKGROUND

Preoxygenation is universally recommended before induction of general anaesthesia to prolong safe apnoea time. The optimal technique for preoxygenation is unclear. We conducted a systematic review to determine the preoxygenation technique associated with the greatest effectiveness in adult patients having general anaesthesia.

METHODS

We searched six databases for randomised controlled trials of patients aged ≥16 yr, receiving general anaesthesia in any setting and comparing different preoxygenation techniques and methods. Our primary effectiveness outcome was safe apnoea time, and secondary outcomes included incidence of arterial oxygen desaturation; lowest SpO2 during airway management; time to end-tidal oxygen concentration of 90%; and [Formula: see text] and [Formula: see text] at the end of preoxygenation. We assessed the quality of evidence according to Grading of Recommendations, Assessment, Development and Evaluation (GRADE) recommendations.

RESULTS

We included 52 studies of 3914 patients. High-flow nasal oxygen with patients in a head-up position was most likely to be associated with a prolonged safe apnoea time when compared with other strategies, with a mean difference (95% credible interval) of 291 (138-456) s and 203 (79-343) s compared with preoxygenation with a facemask in the supine and head-up positions, respectively. Subgroup analysis of studies without apnoeic oxygenation also showed high-flow nasal oxygen in the head-up position as the highest ranked technique, with a statistically significantly delayed mean difference (95% credible interval) safe apnoea time compared with facemask in supine and head-up positions of 222 (63-378) s and 139 (15-262) s, respectively. High-flow nasal oxygen was also the highest ranked technique for increased [Formula: see text] at the end of preoxygenation. However, the incidence of arterial desaturation was less likely to occur when a facemask with pressure support was used compared with other techniques, and [Formula: see text] was most likely to be lowest when preoxygenation took place with patients deep breathing in a supine position.

CONCLUSIONS

Preoxygenation of adults before induction of general anaesthesia was most effective in terms of safe apnoea time when performed with high-flow nasal oxygen with patients in the head-up position in comparison with facemask alone. Also, high-flow nasal oxygen in the head-up position is likely to be the most effective technique to prolong safe apnoea time among those evaluated. Clinicians should consider this technique and patient position in routine practice.

SYSTEMATIC REVIEW PROTOCOL

PROSPERO CRD42022326046.

Anesthetic challenges of pregnant obesity women

Obesity causes significant morbidity and increases the mortality risk for both mother and fetus. With an increasing projected prevalence, it is vital that the obstetric anesthetist is equipped with the knowledge and tools to manage these women. A multi-disciplinary team approach and early planning is required. Neuraxial analgesia for labor helps to negate the need for general anesthesia, which is associated with increased risk in this subset of women. Catheter techniques for neuraxial anesthesia allow for titration, manipulation, and prolongation of the anesthetic block to reduce the risk of conversion to general anesthesia.

Simple steps towards improving safety in obstetric airway management: A quality improvement project

BACKGROUND

Guidelines from the Obstetric Anaesthetists' Association and Difficult Airway Society state that 'a videolaryngoscope should be immediately available for all obstetric general anaesthetics'.

OBJECTIVE

To report the incidence of videolaryngoscopy use, and other airway management safety interventions, in an obstetric population before and after various quality improvement interventions.

DESIGN

Prospective data collection was undertaken over 18 months, divided into three separate 6-month periods: June to November 2019; March to August 2021; January to June 2022. These periods relate to evaluation of specific quality improvement interventions.

SETTING

The project was carried out in a large tertiary referral obstetric unit.

PATIENTS

We identified 401 pregnant women (> 20 weeks' gestation) and postnatal women (up to 48 h post delivery) undergoing an obstetric surgical procedure under general anaesthesia.

INTERVENTIONS

To standardise practice, an intubation checklist was introduced in December 2020 and multidisciplinary staff training in August 2021.

MAIN OUTCOME MEASURES

Primary outcome measures were use of a Macintosh-style videolaryngoscope and tracheal intubation success. Secondary outcome measures were use of an intubation checklist; low flow nasal oxygen; and ramped patient positioning.

RESULTS

Data from 334 tracheal intubations (83.3% of cases) were recorded. Videolaryngoscope use increased from 60% in 2019, to 88% in 2021, to 94% in 2022. Tracheal intubation was successful in all patients, with 94% first pass success overall and only 0.9% requiring three attempts. Use of secondary outcome measures also increased: low flow nasal oxygen from 48% in 2019 to 90% in 2022; ramped positioning from 95% in 2021 to 97% in 2022; and checklist use from 63% in 2021 to 92% in 2022.

CONCLUSIONS

We describe the successful adoption of simple safety measures introduced into routine practice. These comprised videolaryngoscopy, ramped positioning and low flow nasal oxygen. Their introduction was supported by the implementation of an intubation checklist and multidisciplinary team training.

Peri-intubation oxygenation for Caesarean delivery: is there an optimal technique?

Peri-intubation oxygen administration to the pregnant patient during induction of general anaesthesia is critical to avoiding hypoxaemia and harm to the mother and fetus. Recent modelling comparing low-flow with high-flow nasal oxygen in simulated term pregnant women of varying body habitus, taken together with previous work, suggests that face mask preoxygenation with the use of low-flow or high-flow nasal oxygen during the period of apnoea prolongs the safe apnoea period, with the benefit varying by body habitus. Low-flow compared with high-flow nasal oxygen may be easier to combine with face mask preoxygenation and is readily available in all operating theatres, although future improvements in high-flow nasal oxygen delivery systems may improve ease of use for this indication.