Preoxygenation during induction of anesthesia in non-critically ill patients: A systematic review

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.

Introducing a free-breathing MRI method to assess peri-operative myocardial oxygenation and function: A volunteer cohort study

BACKGROUND

Induction of general anaesthesia has many potential triggers for peri-operative myocardial ischaemia including the acute disturbance of blood gases that frequently follows alterations in breathing and ventilation patterns. Free-breathing oxygenation-sensitive cardiovascular magnetic resonance (OS-CMR) imaging may provide the opportunity to continuously quantify the impact of such triggers on myocardial oxygenation.

OBJECTIVE

To investigate the impact of breathing patterns that simulate induction of general anaesthesia on myocardial oxygenation in awake healthy adults using continuous OS-CMR imaging.

DESIGN

Prospective observational study.

SETTING

Single-centre university hospital. Recruitment from August 2020 to January 2022.

PARTICIPANTS

Thirty-two healthy volunteers younger than 45 years old were recruited. Data were analysed from n  = 29 (69% male individuals).

INTERVENTION

Participants performed a simulated induction breathing manoeuvre consisting of 2.5 min paced breathing with a respiration rate of 14 breaths per minute, followed by 5 deep breaths, then apnoea for up to 60s inside a magnetic resonance imaging scanner (MRI). Cardiac images were acquired with the traditional OS-CMR sequence (OS bh-cine ), which requires apnoea for acquisition and with two free-breathing OS-CMR sequences: a high-resolution single-shot sequence (OS fb-ss ) and a real-time cine sequence (OS fb-rtcine ).

MAIN OUTCOME MEASURES

Myocardial oxygenation response at the end of the paced breathing period and at the 30 s timepoint during the subsequent apnoea, reflecting the time of successful intubation in a clinical setting.

RESULTS

The paced breathing followed by five deep breaths significantly reduced myocardial oxygenation, which was observed with all three techniques (OS bh-cine -6.0 ± 2.6%, OS fb-ss -12.0 ± 5.9%, OS fb-rtcine -5.4 ± 7.0%, all P  < 0.05). The subsequent vasodilating stimulus of apnoea then significantly increased myocardial oxygenation (OS bh-cine 6.8 ± 3.1%, OS fb-ss 8.4 ± 5.6%, OS fb-rtcine 15.7 ± 10.0%, all P  < 0.01). The free-breathing sequences were reproducible and were not inferior to the original sequence for any stage.

CONCLUSION

Breathing manoeuvres simulating induction of general anaesthesia cause dynamic alterations of myocardial oxygenation in young volunteers, which can be quantified continuously with free-breathing OS-CMR. Introducing these new imaging techniques into peri-operative studies may throw new light into the mechanisms of peri-operative perturbations of myocardial tissue oxygenation and ischaemia.

VISUAL ABSTRACT

http://links.lww.com/EJA/A922.

Comparison of preoxygenation with a high-flow nasal cannula and a simple face mask before intubation in Korean patients with head and neck cancer

BACKGROUND

Although preoxygenation is an essential procedure for safe endotracheal intubation, in some cases securing sufficient time for tracheal intubation may not be possible. Patients with head and neck cancer might have a difficult airway and need a longer time for endotracheal intubation. We hypothesized that the extended apneic period with preoxygenation via a high-flow nasal cannula (HFNC) is beneficial to patients who undergo head and neck surgery compared with preoxygenation with a simple mask.

METHODS

The study was conducted as a single-center, single-blinded, prospective, randomized controlled trial. Patients were divided into groups based on one of the two preoxygenation.

METHODS

HFNC group or simple facemask (mask group). Preoxygenation was performed for 5 minutes with each method, and endotracheal intubation for all patients was performed using a video laryngoscope. Oxygen partial pressures of the arterial blood were compared at the predefined time points.

RESULTS

For the primary outcome, the mean arterial oxygen partial pressure (PaO2 ) immediately after intubation was 454.2 mm Hg (95% confidence interval [CI], 416.9-491.5 mm Hg) in the HFNC group and 370.7 mm Hg (95% CI, 333.7-407.4 mm Hg) in the mask group (P=0.002). The peak PaO2 at 5 minutes after preoxygenation was not statistically different between the groups (P=0.355).

CONCLUSIONS

Preoxygenation with a HFNC extending to the apneic period before endotracheal intubation may be beneficial in patients with head and neck cancer.

Recommendations from the Brazilian Society of Anesthesiology (SBA) for difficult airway management in adults

Difficult airway management represents a major challenge, requiring a careful approach, advanced technical expertise, and accurate protocols. The task force of the Brazilian Society of Anesthesiology (SBA) presents a report with updated recommendations for the management of difficult airway in adults. These recommendations were developed based on the consensus of a group of expert anesthesiologists, aiming to provide strategies for managing difficulties during tracheal intubation. They are based on evidence published in international guidelines and opinions of experts. The report underlines the essential steps for proper difficult airway management, encompassing assessment, preparation, positioning, pre-oxygenation, minimizing trauma, and maintaining arterial oxygenation. Additional strategies for using advanced tools, such as video laryngoscopy, flexible bronchoscopy, and supraglottic devices, are discussed. The report considers recent advances in understanding crisis management, and the implementation seeks to further patient safety and improve clinical outcomes. The recommendations are outlined to be uncomplicated and easy to implement. The report underscores the importance of ongoing education, training in realistic simulations, and familiarity with the latest technologies available.

A quasi-experimental study of fresh oxygen flow on patients' oxygen reserve during mask-assisted ventilation under general anesthesia induction

Background

To compare the effect of different amounts of fresh oxygen flow on oxygen reserve in patients undergoing general anesthesia.

Methods

Seventy-two patients were enrolled in this quasi-experimental study. Patients were randomly divided into experimental groups with a fresh oxygen flow of 1 L/min, 2 L/min, 4 L/min, and 8 L/min (denoted as G1, G2, G3, and G4, respectively) for 2 min of mask-assisted ventilation. Safe apnea time (SAT) was the primary endpoint; SAT was defined as the time from the cessation of ventilation to the time the patient's pulse oxygen saturation (SpO2) decreased to 90%. Ventilation indicators such as end-tidal oxygen concentration (EtO2), end-tidal carbon dioxide partial pressure (EtCO2), SpO2, and carbon dioxide (CO2) elimination amount, during mask-assisted ventilation, were the secondary endpoints.

Results

The SAT of G1, G2, G3, and G4 were 305.1 ± 97.0 s, 315 ± 112.5 s, 381.3 ± 118.6 s, and 359 ± 104.4 s, respectively (p > 0.05). The EtO2 after 2 min of mask-assisted ventilation in groups G1, G2, G3, and G4 were 69.7 ± 8.8%, 75.2 ± 5.0%, 82.5 ± 3.3%, and 86.8 ± 1.5%, respectively (p < 0.05). Also, there was a moderate positive correlation between the fresh oxygen flow and EtO2 (correlation coefficient r = 0.52, 95% CI 0.31-0.67, p < 0.0001). The CO2 elimination in the G1 and G2 groups was greater than that in the G4 group (p < 0.05). There was no significant difference in other indicators among the groups (all p > 0.05).

Conclusion

The amount of fresh oxygen flow during mask-assisted ventilation was positively correlated with EtO2. Also, even though there was no significant difference, the patients' oxygen reserves increased with the increase in fresh oxygen flow.

Perioperative Noninvasive Ventilation After Adult or Pediatric Surgery: A Comprehensive Review

Postoperative pulmonary complications and acute respiratory failure are among the leading causes of adverse postoperative outcomes. Noninvasive ventilation may safely and effectively prevent acute respiratory failure in high-risk patients after cardiothoracic surgery and after abdominal surgery. Moreover, noninvasive ventilation can be used to treat postoperative hypoxemia, particularly after abdominal surgery. Noninvasive ventilation also can be helpful to prevent or manage intraoperative acute respiratory failure during non-general anesthesia, primarily in patients with poor respiratory function. Finally, noninvasive ventilation is superior to standard preoxygenation in delaying desaturation during intubation in morbidly obese and in critically ill hypoxemic patients. The few available studies in children suggest that noninvasive ventilation could be safe and valuable in treating hypoxemic or hypercapnic acute respiratory failure after cardiac surgery; on the other hand, it could be dangerous after tracheoesophageal correction.

Routine practice in mechanical ventilation in cardiac surgery in Italy

BACKGROUND

Management of mechanical ventilation is a key issue in the prevention of postoperative pulmonary complications (PPCs) and the improvement of surgical outcome. This is especially true in cardiac surgery where the use of the cardiopulmonary bypass (CPB) increases the risk of lung injury. In the last years a growing number of studies have shown that protective ventilation has led to excellent results. However, the literature in this regard is lacking in cardiac surgery and there are no univocal guidelines in this sense. The aim of this survey was to investigate the actual clinical practice about ventilation techniques used in the Italian cardiac surgery centers.

METHODS

A questionnaire of 32-item was sent to 69 Italian cardiac surgery centers, 56 of which return a completed form (81.2%). The questionnaire was assembled by three independent researchers and the final version was e-mailed to all members of the SIAARTI (Italian society of anesthesia resuscitation and intensive care medicine) Study Group on Cardiothoracic and Vascular Anesthesia. The answers were collected using a Google Forms sheet. In case of multiple questionnaires returned from the same center (i.e., different physicians from the same center responded) the head of department was asked to give a definite answer. Furthermore, for the 17 centers who reported multiple questionnaires, no large differences were found between the responses of different doctors belonging to the same center (12.3%±4.2% of discordant answers).

RESULTS

Intraoperatively, patients were ventilated with a tidal volume (TV) of 6-8 mL/kg (91.1% of centers), a positive end-expiration pressure of 3-5 cmH2O (76.8% of centers) and a fraction of inspired oxygen (FiO2) of 50-80% (60.7% of centers). During the CPB, the "stop ventilation" technique was frequently adopted (73.2%). Before the discharge from the intensive care unit (ICU) non-invasive ventilation (NIV) was never applied in 32.1% of the centers, but it was used in 46.4% of patients with postoperative complications.

CONCLUSIONS

This study shows a significant heterogeneity in ventilatory techniques among the Italian centers during CPB, whereas in the other surgical time the majority of the responding centers adopted a protective mechanical ventilation strategy.

Comparison of preoxygenation efficiency with Intersurgical Economy and Intersurgical QuadraLite anaesthetic face masks

BACKGROUND

Sufficient preoxygenation prevents arterial oxygen desaturation prior to intubation. An optimally sealed facemask is necessary for fast preoxygenation. The study was aimed at comparing the efficiency of preoxygenation using two different face masks.

MATERIALS AND METHODS

In 2018, a prospective study was conducted. Patients were classified into two groups: group A - Intersurgical Economy face masks, group B - Intersurgical QuadraLite masks. The circuit was flushed with 100% O2 for 30s, preoxygenation started with flow of 8l/min, FiO2100. The patients were asked to breathe deeply. Fentanyl (1-2 mcg/kg) was administered to increase mask toleration. End-tidal oxygen concentration (EtO2) ≥90% was the goal. EtO2 was monitored after 30, 60, 90, 120, 180, 210, 240, 270 and 300 seconds. Data was analyzed using the Independent-Samples T-test and the Mann-Whitney-U test.

RESULTS

Twelve patients were enrolled in group A and 19 in group B. Differences in sex, age, BMI and Mallampati class in the groups were statistically insignificant (p = 0.13, 0.39, 0.65, 0.43 respectively). Patients assigned to ASA I - 25.8% (n = 8->2/6), ASA II - 71.0 % (n = 22->10/12), ASA III - 3.2% (n = 1->0/1), p = 0.64. The success rate of preoxygenation to EtO290 within 5 min was statistically significantly different in the groups, with 33.3% in group A and 94.7% in group B (p < 0.01). Mean time to EtO290 was 228.3 ± 104.0/164.4 ± 84.3. Mean EtO2 after: 30s - 56.0 ± 13.5/69.3 ± 11.2 (p < 0.01); 60s - 63.8 ± 15.3/76.1 ± 11.7 (p = 0.02), 90s - 67.8 ± 17.7/80.7 ± 10.1 (p = 0.03); 120s-69.6 ± 18.2/83.4 ± 10.0 (p = 0.03), 150s-71.1 ± 19.0/87.1 ± 6.5 (p = 0.01); 180s - 72.9 ± 16.8/88.5 ± 5.3 (p = 0.01), 210s - 72.6 ± 18.0/89.2 ± 5.1 (p < 0.01); 240s - 74.17 ± 15.4/90.0 ± 4.3 (p < 0.01), 270s-76.3 ± 16.3/90.2 ± 3.6; 300s - 77.8 ± 14.6/90.2 ± 1.5 (p < 0.01).

CONCLUSIONS

Preoxygenation was significantly more efficient and faster with Intersurgical QuadraLite face masks.