Supplementation of pre-oxygenation in morbidly obese patients using nasopharyngeal oxygen insufflation

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.

Comparison of different weight-based scalars of remimazolam tosylate for anesthesia induction in obese patients: study protocol for a prospective, controlled trial

BACKGROUND

The physiologic and anthropometric characteristics changes associated with obesity may result in the alternation of pharmacologic management. Remimazolam tosylate is a new type of ultra-short-acting benzodiazepine with stable context-sensitive half-time (CSHT) and no lipid accumulation after long-time infusion. Although remimazolam tosylate has potential advantages for the induction and maintenance of anesthesia in obese patients, the appropriate induction dosing scalars among obese patients are unknown. Therefore, we aim to compare the different weight-based scalars for dosing remimazolam tosylate of anesthesia induction among obese patients.

METHODS/DESIGN

The study will be performed as a prospective, single-center, double-blind, controlled clinical trial. The study design is a comparison of remimazolam tosylate requirements based on total body weight (TBW) or lean body weight (LBW) to reach a Modified Observer's Assessment of Alertness and Sedation (MOAA/S) score of 0 among obese subjects (BMI ≥ 35 kg/m2). Another twenty normal-weight subjects (18.5 kg/m2 ≤ BMI < 25 kg/m2) will be enrolled as a control group, whose induction dose is scaled based on TBW. The infusion rate of remimazolam tosylate during induction is 12 mg/kg/h in all groups.

DISCUSSION

Results of the present study will provide evidence of dose scalar of remimazolam tosylate to guide the clinical practice of anesthesia induction in obese patients.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR220005664. Registered on 9 February 2022, https://www.chictr.org.cn/showproj.aspx?proj=151150 .

Giant Ovarian Tumor

Giant ovarian tumors are rare, as most cases are diagnosed during routine gynecological check-ups or abdominal ultrasound examinations. They are a challenge for gynecologists and surgeons. Diagnosis in such patients is difficult due to the limitations of the medical apparatus. Perioperative management requires specialized anesthetic medical care and is associated with high mortality. The paper presents the case of a 23-year-old woman with a giant ovarian serous tumor, characterized by an enlargement of the abdominal circumference, periodic abdominal pain, irregular menstruation, and infertility. The patient attributed these nonspecific symptoms to obesity; therefore, she was hesitant to schedule a doctor's appointment. The patient underwent laparotomy, and the cyst originating from the left ovary was removed along with part of the organ. An intraoperative examination was performed. After confirming the benign nature of the lesion, the operation was completed. In our work, we concentrated on the multidisciplinary care of the patient who required enhanced medical care from the internal medicine, cardiology, anesthesiology, rehabilitation medicine, and gynecology specialists. There were no hemodynamic changes in the heart during hospitalization. There were no significant early or late postoperative complications. In this case, we also paid attention to compression symptoms resulting from a giant ovarian tumor and the high risk of intraoperative complications resulting from its resection.

Effectiveness of high-flow nasal cannula oxygen in apneic oxygenation during intubation in high-risk surgical patients: a systematic review protocol

OBJECTIVE

This review will investigate the effectiveness of high-flow nasal oxygen in apneic oxygenation through safe apnea time and other ventilation parameters in patients at high risk of oxygen desaturation during induction and tracheal intubation for anesthesia management.

INTRODUCTION

High-risk surgical patient groups include obese patients, those with suspected or known obstructive sleep apnea, and critically ill patients, who are at risk of rapid oxygen desaturation during intubation. Conventional oxygen administration in induction and intubation of patients undergoing general anesthesia include nasal cannulas, simple face masks, Venturi, buccal oxygenation, bag-valve mask ventilation, and non-invasive ventilation. High-flow nasal oxygen has emerged as a novel technique, and is advantageous because it increases positive end-expiratory pressure and oxygen delivered.

INCLUSION CRITERIA

Eligible studies will include high-risk surgical patients aged 18 or above requiring endotracheal intubation in both emergency and elective anesthetic settings. High-risk patients are defined as those with suspected or known obstructive sleep apnea, obesity (BMI > 35), or critically ill patients (scored the American Society of Anesthesiologists classification as 3 or above).

METHODS

The review will follow the JBI methodology for systematic reviews of effectiveness. Databases to be searched include MEDLINE, Embase, and Scopus. Reference lists of selected studies will then be hand-searched for additional eligible studies. The primary outcome will be safe apnea time, with secondary outcomes including oxygen and carbon dioxide parameters, and adverse events (eg, gastric distension). Studies will, where possible, be pooled in statistical meta-analyses with data heterogeneity assessed using the standard χ2 and I2 tests.

REVIEW REGISTRATION

PROSPERO CRD42022312145.

Oxygenation during the apnoeic phase preceding intubation in adults in prehospital, emergency department, intensive care and operating theatre environments

BACKGROUND

Apnoeic oxygenation is the delivery of oxygen during the apnoeic phase preceding intubation. It is used to prevent respiratory complications of endotracheal intubation that have the potential to lead to significant adverse events including dysrhythmia, haemodynamic decompensation, hypoxic brain injury and death. Oxygen delivered by nasal cannulae during the apnoeic phase of intubation (apnoeic oxygenation) may serve as a non-invasive adjunct to endotracheal intubation to decrease the incidence of hypoxaemia, morbidity and mortality.

OBJECTIVES

To evaluate the benefits and harms of apnoeic oxygenation before intubation in adults in the prehospital, emergency department, intensive care unit and operating theatre environments compared to no apnoeic oxygenation during intubation.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 4 November 2022.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and quasi-RCTs that compared the use of any form of apnoeic oxygenation including high flow and low flow nasal cannulae versus no apnoeic oxygenation during intubation. We defined quasi-randomization as participant allocation to each arm by means that were not truly random, such as alternation, case record number or date of birth. We excluded comparative prospective cohort and comparative retrospective cohort studies, physiological modelling studies and case reports.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were 1. hospital stay and 2. incidence of severe hypoxaemia. Our secondary outcomes were 3. incidence of hypoxaemia, 4. lowest recorded saturation of pulse oximetry (SpO2), 5. intensive care unit (ICU) stay, 6. first pass success rate, 7. adverse events and 8.

MORTALITY

We used GRADE to assess certainty of evidence.

MAIN RESULTS

We included 23 RCTs (2264 participants) in our analyses. Eight studies (729 participants) investigated the use of low-flow (15 L/minute or less), and 15 studies (1535 participants) investigated the use of high-flow (greater than 15 L/minute) oxygen. Settings were varied and included the emergency department (2 studies, 327 participants), ICU (7 studies, 913 participants) and operating theatre (14 studies, 1024 participants). We considered two studies to be at low risk of bias across all domains. None of the studies reported on hospital length of stay. In predominately critically ill people, there may be little to no difference in the incidence of severe hypoxaemia (SpO2 less than 80%) when using apnoeic oxygenation at any flow rate from the start of apnoea until successful intubation (risk ratio (RR) 0.86, 95% confidence interval (CI) 0.66 to 1.11; P = 0.25, I² = 0%; 15 studies, 1802 participants; low-certainty evidence). There was insufficient evidence of any effect on the incidence of hypoxaemia (SpO2 less than 93%) (RR 0.58, 95% CI 0.23 to 1.46; P = 0.25, I² = 36%; 3 studies, 489 participants; low-certainty evidence). There may be an improvement in the lowest recorded oxygen saturation, with a mean increase of 1.9% (95% CI 0.75% to 3.05%; P < 0.001, I² = 86%; 15 studies, 1525 participants; low-certainty evidence). There may be a reduction in the duration of ICU stay with the use of apnoeic oxygenation during intubation (mean difference (MD) ‒1.13 days, 95% CI ‒1.51 to ‒0.74; P < 0.0001, I² = 46%; 5 studies, 815 participants; low-certainty evidence). There may be little to no difference in first pass success rate (RR 1.00, 95% CI 0.93 to 1.08; P = 0.79, I² = 0%; 8 studies, 826 participants; moderate-certainty evidence). There may be little to no difference in incidence of adverse events including oral trauma, arrhythmia, aspiration, hypotension, pneumonia and cardiac arrest when apnoeic oxygenation is used. There was insufficient evidence about any effect on mortality (RR 0.84, 95% CI 0.70 to 1.00; P = 0.06, I² = 0%; 6 studies, 1015 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

There was some evidence that oxygenation during the apnoeic phase of intubation may improve the lowest recorded oxygen saturation. However, the differences in oxygen saturation were unlikely to be clinically significant. This did not translate into any measurable effect on the incidence of hypoxaemia or severe hypoxaemia in a group of predominately critically ill people. We were unable to assess the influence on hospital length of stay; however, there was a reduction in ICU stay in the apnoeic oxygenation group. The mechanism for this is unclear as there was little to no difference in first pass success or adverse event rates.

Effectiveness of Face mask only oxygenation and apnoeic oxygenation in addition to face mask in sustaining PaO2 during rapid sequence induction - A randomized control trial

Background and Aims

Apnoeic oxygenation, although useful during elective intubations, has not shown consistent beneficial results during emergency intubations in critically ill patients. We aimed to study the effectiveness of adding apnoeic oxygenation to our routine practice of using facemask alone, in emergency laparotomy patients needing rapid sequence induction (RSI), for sustaining partial pressure of oxygen (PaO2).

Material and Methods

Seventy-two patients undergoing RSI for emergency laparotomy were randomly allocated to either receive pre-oxygenation with 5 L/min of oxygen (O2) with a facemask (Group-FM) or apnoeic oxygenation with 10 L/min of O2 through a nasal catheter in addition to pre-oxygenation (Group-NC). Apnoea (90 s) was allowed from the removal of the facemask before the resumption of ventilation. Arterial blood gas analysis was done at the baseline, following pre-oxygenation and after 90 s of apnoea to study the PaO2 and partial pressure of carbon dioxide (PaCO2). The circuit O2 concentrations (fraction of inspired [FiO2] and end-tidal [EtO2]) were also noted to ensure a steady state of O2 uptake was reached.

Results

The circuit O2 concentrations were 90 ± 4% in group FM and 93 ± 5% in Group-NC. The FiO2-EtO2 difference was 4% in both groups. During the 90 s apnoea following pre-oxygenation, there was a fall in the PaO2 by 38% in Group-FM and 12% in Group-NC (P = 0.000). Increase in PaCO2 was similar in both groups (Group-FM: 44 [range: 32-55] mmHg; Group-NC: 42 [range: 33-54] mmHg, P = 0.809).

Conclusion

Apnoeic insufflation of O2 using a nasopharyngeal catheter along with facemask oxygenation is more effective in sustaining PaO2 for 90 s during RSI than facemask-only oxygenation in patients undergoing emergency laparotomy.

Comparing nasopharyngeal apnoeic oxygenation at 18 l/min to preoxygenation alone in obese patients - A randomised controlled study

STUDY OBJECTIVE

Investigate a low-cost, nasopharyngeal apnoeic oxygenation technique, establish its efficacy, and compare it to preoxygenation only in an obese population. The study's hypothesis was that nasopharyngeal apnoeic oxygenation at 18 l.min^-1 would significantly prolong safe apnoea time compared to preoxygenation alone.

DESIGN

Randomised controlled study.

SETTING

Theatre complex of a resource constrained hospital.

PATIENTS

30 adult, obese (BMI ≥ 35 kg.m^-2) patients presenting for elective surgery. Patients with limiting cardio-respiratory disease, suspected difficult airway, risk of aspiration, and that were pregnant, were excluded. Patients were allocated by block randomisation in a 1:2 ratio to a preoxygenation-only (No-AO) and an intervention group (NPA-O₂).

INTERVENTIONS

All patients were preoxygenated to an Et-O2 > 80%, followed by a standardised induction. The intervention group received oxygen at 18 l.min^-1 via the nasopharyngeal catheter intervention. The desaturation process was documented until an SpO₂ of 92% or 600 s was reached.

MEASUREMENTS

Baseline demographic and clinical characteristics were collected. The primary outcome was safe apnoea time, defined as the time taken to desaturate to an SpO₂ of 92%. Secondary outcomes were rate of carbon dioxide accumulation and factors affecting the risk of desaturation.

MAIN RESULTS

The study was conducted in a morbidly obese population (NoAO = 41,1 kg.m^-2; NPA-O₂ = 42,5 kg.m^-2). The risk of desaturation was signifantly lower in the intervention group (Hazzard Ratio = 0,072, 95% CI[0,019-0,283]) (Log-Rank test, p < 0.001). The median safe apnoea time was significantly longer in the intervention group (NoAO = 262 s [IQR 190-316]; NPA-O₂ = 600 s [IQR 600-600]) (Mann-Whitney-U test, p < 0.001). The mean rate of CO₂ accumalation was significantly slower in the intervention group (NoAO = 0,47 ± 0,14 kPa.min^-1; NPA-O₂ = 0,3 ± 0,09 kPa.min^-1) (t-test, p = 0.003). There were no statistically significant risk factors associated with an increased risk of desaturation found.

CONCLUSIONS

Nasopharyngeal apnoeic oxygenation at 18 l/min prolongs safe apnoea time, compared to preoxygenation alone, and reduces the risk of desaturation in morbidly obese patients.

CLINICAL TRIAL REGISTRATION

PACTR202202665252087; WC/202004/007.

Ramped versus sniffing position in the videolaryngoscopy-guided tracheal intubation of morbidly obese patients: a prospective randomized study

BACKGROUND

Ramped positioning is recommended for intubating obese patients undergoing direct laryngoscopy. However, whether the use of the ramped position can provide any benefit in videolaryngoscopy-guided intubation remains unclear. This study assessed intubation time using videolaryngoscopy in morbidly obese patients in the ramped versus sniffing positions.

METHODS

This is a prospective randomized study in patients with morbid obesity (n = 82; body mass index [BMI] ≥ 35 kg/m2). Patients were randomly allocated to either the ramped or the standard sniffing position groups. During the induction of general anesthesia, difficulty in mask ventilation was assessed using the Warters scale. Tracheal intubation was performed using a C-MAC® D-Blade videolaryngoscope, and intubation difficulty was assessed using the intubation difficulty scale (IDS). The primary endpoint was the total intubation time calculated as the sum of the laryngoscopy and tube insertion times.

RESULTS

The percentage of difficult mask ventilation (Warters scale ≥ 4) was significantly lower in the ramped (n = 40) than in the sniffing group (n = 41) (2.5% vs. 34.1%, P < 0.001). The percentage of easy intubation (IDS = 0) was significantly higher in the ramped than in the sniffing group (70.0% vs. 7.3%, P < 0.001). The total intubation time was significantly shorter in the ramped than in the sniffing group (22.5 ± 6.2 vs. 40.9 ± 9.0, P < 0.001).

CONCLUSIONS

Compared with the sniffing position, the ramped position reduced intubation time in morbidly obese patients and effectively facilitated both mask ventilation and tracheal intubation using videolaryngoscopy.

Apnoeic oxygenation in morbid obesity: a randomised controlled trial comparing facemask and high-flow nasal oxygen delivery

BACKGROUND

Obesity is a risk factor for airway-related incidents during anaesthesia. High-flow nasal oxygen has been advocated to improve safety in high-risk groups, but its effectiveness in the obese population is uncertain. This study compared the effect of high-flow nasal oxygen and low-flow facemask oxygen delivery on duration of apnoea in morbidly obese patients.

METHODS

Morbidly obese patients undergoing bariatric surgery were randomly allocated to receive either high-flow nasal (70 L min^-1) or facemask (15 L min^-1) oxygen. After induction of anaesthesia, the patients were apnoeic for 18 min or until peripheral oxygen saturation decreased to 92%.

RESULTS

Eighty patients were studied (41 High-Flow Nasal Oxygen, 39 Facemask). The median apnoea time was 18 min in both the High-Flow Nasal Oxygen (IQR 18-18 min) and the Facemask (inter-quartile range [IQR], 4.1-18 min) groups. Five patients in the High-Flow Nasal Oxygen group and 14 patients in the Facemask group desaturated to 92% within 18 min. The risk of desaturation was significantly lower in the High-Flow Nasal Oxygen group (hazard ratio=0.27; 95% confidence interval [CI], 0.11-0.65; P=0.007).

CONCLUSIONS

In experienced hands, apnoeic oxygenation is possible in morbidly obese patients, and oxygen desaturation did not occur for 18 min in the majority of patients, whether oxygen delivery was high-flow nasal or low-flow facemask. High-flow nasal oxygen may reduce desaturation risk compared with facemask oxygen. Desaturation risk is a more clinically relevant outcome than duration of apnoea. Individual physiological factors are likely to be the primary determinant of risk rather than method of oxygen delivery.

CLINICAL TRIAL REGISTRATION

NCT03428256.

Role of modified nasopharyngeal oxygen therapy in apnoeic oxygenation under general anaesthesia: a single-centre, randomized controlled clinical study

Apnoeic oxygenation is not only important for patients who cannot be intubated/ventilated, but also can be routinely employed when planning to secure the airway.We aimed to compare safe apnoea times between patients receiving modified nasopharyngeal oxygen therapy and those receiving high-flow nasal oxygen therapy (HFNO) following the induction of general anaesthesia.This was a single-centre, randomized controlled clinical study. Eighty-four female patients undergoing elective laparoscopic gynaecological surgery under general anaesthesia were randomly assigned to the high-flow nasal oxygen therapy group (Group HFNO) or the modified nasopharyngeal oxygen therapy group (Group Naso). A Kaplan-Meier survival curve was used to describe the apnoeic oxygenation time.The safe apnoea time of the patients in the Group Naso was higher than that of the patients in the Group HFNO (20 (19.3 to 20.0) vs. 16.5 (12.9 to 20) minutes, P < 0.05). The incidence of SpO₂ < 95% in the Group Naso was lower than that in the Group HFNO; hazard ratio 0.3 (95% confidence interval 0.2 to 0.6, P < 0.0001). Modified nasopharyngeal oxygen therapy which uses far less oxygen than HFNO is a convenient and effective method of apnoeic oxygenation in normal female patients.Trial registration: https://www.chictr.org.cn , ChiCTR2000039433; date of registration: 28/10/2020.

Medium-Flow Oxygenation Through Facial Mask and Nasal Cannula in a Limited Resource Setting

Introduction: In centers with limited resources, a high flow nasal cannula is not available, thus we assess if preoxygenation with 15L flow of O2 available from anesthesia machines can prolong the safety period of induction of anesthesia before intubation and provide more time for securing the airway. Moreover, we compared the preoxygenation with standard 6L vs. 15L O2 through a facemask or a nasal cannula. Material and methods: Patients were allocated into four groups. Group I patients were preoxygenated with a nasal cannula on 6L of oxygen, patients in group II were preoxygenated with a nasal cannula on 15L of oxygen, patients in group III were preoxygenated with a facemask on 6L of oxygen, and patients in group IV were preoxygenated with a facemask on 15L of oxygen. The primary endpoint was time to desaturation and intubation. The secondary endpoints were PaO2, PaCO2, Sat% and ETCO2. Results: The groups with 15L preoxygenation had a statistically significant prolonged time to desaturation and intubation. Patients allocated to group II have a statistically significant greater PaO2 and lesser ETCO2 compered with group I. However, between patients in group III and IV there is a difference only in PaCO2, and although this effect is significant, both groups have values within the normal range. Conclusion: In centers with limited resources, preoxygenation with the maximum available oxygen flow from anesthesia machines (15L/min) are useful. This prolongs the safety period for securing the airway. We suggest the use of the maximum available amount of oxygen flow from anesthesia machines in clinical settings.

Anesthetic management of a severely obese patient (body mass index 70.1 kg/m2) undergoing giant ovarian tumor resection: a case report

BACKGROUND

Giant ovarian tumors are rarely seen with severe obesity. There are few reports of perioperative management of giant ovarian tumors and severe obesity. Here, we report the perioperative management of physiological changes in massive intraabdominal tumors in a patient with severe obesity.

CASE PRESENTATION

A 46-year-old Japanese woman (height 166 cm, weight 193.2 kg; body mass index 70.1 kg/m²) was scheduled to undergo laparotomy for a giant ovarian tumor. The patient was placed in the ramp position. Preoxygenation was performed using a high-flow nasal cannula, and awake tracheal intubation was performed using a video laryngoscope. Mechanical ventilation using a limited tidal volume with moderate positive end-expiratory pressure was applied during the surgical procedure. The aspiration speed for 15 L of tumor aspirate was set to under 1 L/minute, and the possibility of reexpansion pulmonary edema was foreseen by conventional monitoring.

CONCLUSIONS

We successfully completed anesthetic management in a patient with concomitant severe obesity and giant ovarian tumors.

A review on the anesthetic management of obese patients undergoing surgery

There has been an observed increase in theprevalence of obesity over the past few decades. The prevalence of anesthesiology related complications is also observed more frequently in obese patients as compared to patients that are not obese. Due to the increased complications that accompany obesity, obese patients are now more often requiring surgical interventions. Therefore, it is important that anesthesiologists be aware of this development and is equipped to manage these patients effectively and appropriately. As a result, this review highlights the effective management of obese patients undergoing surgery focusing on the preoperative, perioperative and postoperative care of these patients.

Tracheal Tube-Mounted Camera Assisted Intubation vs. Videolaryngoscopy in Expected Difficult Airway: A Prospective, Randomized Trial (VivaOP Trial)

Background: Tracheal intubation in patients with an expected difficult airway may be facilitated by videolaryngoscopy (VL). The VL viewing axis angle is specified by the blade shape and visualization of the larynx may fail if the angle does not meet anatomy of the patient. A tube with an integrated camera at its tip (VST, VivaSight-SL) may be advantageous due to its adjustable viewing axis by means of angulating an included stylet.

Methods: With ethics approval, we studied the VST vs. VL in a prospective non-inferiority trial using end-tidal oxygen fractions (etO₂) after intubation, first-attempt success rates (FAS), visualization assessed by the percentage of glottis opening (POGO) scale, and time to intubation (TTI) as outcome parameters.

Results: In this study, 48 patients with a predicted difficult airway were randomized 1:1 to intubation with VST or VL. Concerning oxygenation, the VST was non-inferior to VL with etO₂ of 0.79 ± 0.08 (95% CIs: 0.75–0.82) vs. 0.81 ± 0.06 (0.79–0.84) for the VL group, mean difference 0.02 (−0.07 to 0.02), p = 0.234. FAS was 79% for VST and 88% for VL (p = 0.449). POGO was 89 ± 21% in the VST-group and 60 ± 36% in the VL group, p = 0.002. TTI was 100 ± 57 s in the VST group and 68 ± 65 s in the VL group (p = 0.079). TTI with one attempt was 84 ± 31 s vs. 49 ± 14 s, p < 0.001.

Conclusion: In patients with difficult airways, tracheal intubation with the VST is feasible without negative impact on oxygenation, improves visualization but prolongs intubation. The VST deserves further study to identify patients that might benefit from intubation with VST.

Pre-oxygenation and apneic oxygenation in patients living with obesity – A review of novel techniques

Morbidly obese patients are in the group of patients, who can desaturate fast because of changes in lung volumes and reduction in Functional Residual Capasity due to obesity. There are novel methods to improve preoxygenation and to maintain oxygneation during intubation efforts. In this paper we present methods of apneic oxygenation for morbidly obese patients.

Bag-Mask Ventilation Versus Apneic Oxygenation During Tracheal Intubation in Critically Ill Adults: A Secondary Analysis of 2 Randomized Trials

Background: Hypoxemia is common during tracheal intubation in intensive care units. To prevent hypoxemia during intubation, 2 methods of delivering oxygen between induction and laryngoscopy have been proposed: bag-mask ventilation and supplemental oxygen delivered by nasal cannula without ventilation (apneic oxygenation). Whether one of these approaches is more effective for preventing hypoxemia during intubation of critically ill patients is unknown. Methods: We performed a secondary analysis of data from 138 patients enrolled in 2, consecutive randomized trials of airway management in an academic intensive care unit. A total of 61 patients were randomized to receive bag-mask ventilation in a trial comparing bag-mask ventilation to none, and 77 patients were randomized to receive 100% oxygen at 15 L/min by nasal cannula in a trial comparing apneic oxygenation to none. Using multivariable linear regression accounting for age, body mass index, severity of illness, and oxygen saturation at induction, we compared patients assigned to bag-mask ventilation with those assigned to apneic oxygenation regarding lowest oxygen saturations from induction to 2 min after intubation. Results: Patients assigned to bag-mask ventilation and apneic oxygenation were similar at baseline. The median lowest oxygen saturation was 96% (interquartile range [IQR] 89%-100%) in the bag-mask ventilation group and 92% (IQR 84%-99%) in the apneic oxygenation group. After adjustment for prespecified confounders, bag-mask ventilation was associated with a higher lowest oxygen saturation compared to apneic oxygenation (mean difference, 4.2%; 95% confidence interval, 0.7%-7.8%; P = .02). The incidence of severe hypoxemia (oxygen saturation<80%) was 6.6% in the bag-mask ventilation group and 15.6% in the apneic oxygenation group (adjusted odds ratio, 0.33; P = .09). Conclusions: This secondary analysis of patients assigned to bag-mask ventilation and apneic oxygenation during 2 clinical trials suggests that bag-mask ventilation is associated with higher oxygen saturation during intubation compared to apneic oxygenation.

Oxygenation laryngoscope vs. nasal standard and nasal high flow oxygenation in a technical simulation of apnoeic oxygenation

Background

Failed airway management is the major contributor for anaesthesia-related morbidity and mortality. Cannot-intubate-cannot-ventilate scenarios are the most critical emergency in airway management, and belong to the worst imaginable scenarios in an anaesthetist’s life. In such situations, apnoeic oxygenation might be useful to avoid hypoxaemia. Anaesthesia guidelines recommend careful preoxygenation and application of high flow oxygen in difficult intubation scenarios to prevent episodes of deoxygenation. In this study, we evaluated the decrease in oxygen concentration in a model when using different strategies of oxygenation: using a special oxygenation laryngoscope, nasal oxygen, nasal high flow oxygen, and control.

Methods

In this experimental study we compared no oxygen application as a control, standard pure oxygen application of 10 l·min^− 1 via nasal cannula, high flow 90% oxygen application at 20 l·min^− 1 using a special nasal high flow device, and pure oxygen application via our oxygenation laryngoscope at 10 l·min^− 1. We preoxygenated a simulation lung to 97% oxygen concentration and connected this to the trachea of a manikin model simulating apnoeic oxygenation. Decrease in oxygen concentration in the simulation lung was measured continuously for 20 min.

Results

Oxygen concentration in the simulation lung dropped from 97 ± 1% at baseline to 40 ± 1% in the no oxygen group, to 80 ± 1% in the standard nasal oxygen group, and to 73 ± 2% in the high flow nasal oxygenation group. However, it remained at 96 ± 0% in the oxygenation laryngoscope group (p < 0.001 between all groups).

Conclusions

In this technical simulation, oxygenation via oxygenation laryngoscope was more effective than standard oxygen insufflation via nasal cannula, which was more effective than nasal high flow insufflation of 90% oxygen.

Randomised controlled trial to assess the effectiveness of apnoeic oxygenation in adults using low-flow or high-flow nasal cannula with head side elevation versus usual care to prevent desaturation during endotracheal intubation in the emergency department (ApOxED): study protocol

INTRODUCTION

Apnoeic oxygenation is a process of delivering continuous oxygen through nasal cannula during direct laryngoscopy. The oxygen that is delivered through these nasal cannulas is either low flow or high flow. Although the effectiveness of apnoeic oxygenation has been shown through systematic reviews and randomised controlled trials, a comparison of high-flow versus low-flow oxygen delivery has not been tested through a superiority study design. In this study we propose to assess the effectiveness of giving low-flow oxygen with head side elevation versus high-flow oxygen with head side elevation against the usual practice of care in which no oxygen is provided during direct laryngoscopy.

METHODS AND ANALYSIS

This will be a three-arm study instituting a block randomisation technique with a sample size of 46 in each arm (see table 1). Due to the nature of the intervention, no blinding will be introduced. The primary outcomes will be lowest non-invasive oxygen saturation measurement during direct laryngoscopy and during the 2 min after the placement of the tube and the first pass success rate. The intervention constitutes head side elevation up to 30° for improving glottis visualisation together with low-flow or high-flow oxygen delivery through nasal cannula to increase safe apnoea time for participants undergoing endotracheal intubation. Primary analysis will be intention to treat.

ETHICS AND DISSEMINATION

The study is approved by the Ethical Review Committee of Aga Khan University Hospital (2019-0726-2463). The project is an institution University Research Committee grant recipient 192 002ER-PK. The results of the study will be disseminated among participants, patient communities and healthcare professionals in the institution through seminars, presentations and emails. Further, the findings will be published in a highly accessed peer-reviewed medical journal and will be presented at both national and international conferences.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT04242537).

Duration of safe apnea in patients with morbid obesity during passive oxygenation using high-flow nasal insufflation versus regular flow nasal insufflation, a randomized trial

BACKGROUND

Obese patients are at risk for rapid oxygen desaturation during anesthesia induction. Apneic oxygenation with regular flow oxygen insufflation has successfully been used to prolong the duration of safe apnea without desaturation (DAWD) in morbidly obese patients. Using high-flown nasal insufflation of oxygen (HFNI) for apneic oxygenation might further increase the DAWD.

OBJECTIVES

To compare the duration of safe apnea using high-flown nasal insufflation of oxygen or standard flow oxygen insufflation for apneic oxygenation in a simulated difficult intubation scenario in patients with morbid obesity.

SETTING

Operating room, University Hospital, Austria.

METHODS

In a prospective, randomized, clinical trial, patients received standardized preoxygenation and anesthesia induction. Apneic oxygenation was performed using standard nasal prongs (10 L/min) or HFNI (120 L/min) during laryngoscopy. A Cormack-Lehane 3° view was maintained until the oxygen saturation on pulse oximetry (SpO₂) dropped ≤95% or for a maximum of 15 minutes. The primary outcome of this study was to compare the duration of safe apnea using HFNI or standard flow oxygen insufflation for apneic oxygenation. In addition, arterial blood gas results, and airway pressures were investigated.

RESULTS

In 40 patients with morbid obesity (body mass index [BMI] >40 kg/m²) and the American Society of Anesthesiologists physical classification ≤3 who underwent bariatric surgery, the median duration of safe apnea was 601 (268-900) seconds in the standard group and 537 (399-808) seconds in the HFNI group (P = .698). No differences in arterial blood gas results were observed between the groups. The median airway pressure was 0 (0-0) cm H₂O in the standard group and 1 (0-2) cm H₂O in the HFNI group (P = .005).

CONCLUSION

Compared with standard nasal apneic oxygenation, HFNI did not increase the duration of safe apnea in patients with morbid obesity. A significant but clinically negligible higher airway pressure was observed when using HFNI.

Prevention of Oxygen Desaturation in Morbidly Obese Patients During Electroconvulsive Therapy: A Narrative Review

In general, preoxygenation is performed using a face mask with oxygen in a supine position, and oxygenation is maintained with manual mask ventilation during electroconvulsive therapy (ECT). However, hypoxic episodes during ECT are not uncommon with this conventional method, especially in morbidly obese patients. The most important property of ventilatory mechanics in patients with obesity is reduced functional residual capacity (FRC). Thus, increasing FRC and oxygen reserves is an important step to improve oxygenation and prevent oxygen desaturation in these individuals. Head-up position, use of apneic oxygenation, noninvasive positive pressure ventilation, and high-flow nasal cannula help increase FRC and oxygen reserves, resulting in improved oxygenation and prolonged safe apnea period. Furthermore, significantly higher incidence of difficult mask ventilation is common in morbidly obese individuals. Supraglottic airway devices establish effective ventilation in patients with difficult airways. Thus, the use of supraglottic airway devices is strongly recommended in these patients. Conversely, because muscle fasciculation induced by depolarizing neuromuscular blocking agents markedly increases oxygen consumption, especially in individuals with obesity, the use of nondepolarizing neuromuscular blocking agents may contribute to better oxygenation in morbidly obese patients during ECT.

A prospective, up-down sequential allocation study investigating the effectiveness of vital capacity breaths using high-flow nasal oxygenation versus a tight-fitting face mask to pre-oxygenate term pregnant women

BACKGROUND

The role of high flow nasal oxygenation (HFNO) for pre-oxygenation before obstetric general anaesthesia remains unclear. This study aimed to determine the number of vital capacity breaths using HFNO required to pre-oxygenate 90% of parturients to an end-tidal oxygen concentration fraction (F_ETO₂) of ≥0.90 (termed EN90).

METHODS

Using up-down, sequential allocation trial design, volunteer term parturients undergoing caesarean delivery were investigated with HFNO with their mouth closed, followed by mouth open, and if F_ETO₂ ≥0.90 was not achieved after a maximum of 20 vital capacity breaths, pre-oxygenation was attempted with a face mask. The primary outcome was the number of vital capacity breaths required using HFNO (mouth open and closed) to achieve EN90. Secondary outcomes included assessment of EN90 using mouth open versus mouth closed and face mask pre-oxygenation, maternal satisfaction and evaluation of fetal cardiotocography.

RESULTS

Twenty women at term were recruited. Successful pre-oxygenation occurred in 4 (20%), 3 (15%) and 14 (70%) women with HFNO mouth closed, HFNO mouth open, and via face mask respectively. At up to 20 vital capacity breaths, face mask pre-oxygenation was more successful at achieving EN90 compared with both HFNO with a closed (P=0.006) or open (P=0.001) mouth. Closed mouth HFNO did not outperform open mouth pre-oxygenation.

CONCLUSION

Face mask pre-oxygenation is more effective at achieving EN90 compared with to HFNO within a clinically acceptable number of vital capacity breaths. Further studies are needed to determine the role of HFNO in optimising the time before desaturation and for apnoeic oxygenation in term parturients.

C-arm fluoroscopy for tracheal intubation in a patient with severe cervical spine pathology

Tracheal intubation is challenging in patients with severe cervical spine pathology. In such cases, awake fiberoptic intubation is the gold standard and safest option for tracheal intubation. However, this technique requires the patient's understanding and cooperation, and therefore, may be contraindicated in patients with refusal or poor tolerance. Herein, we report successful orotracheal intubation in a patient with limited mouth opening and severe cervical spine rigidity under general anesthesia using an extraglottic airway device and a gum-elastic bougie under C-arm fluoroscopic guidance.

Perioperative care of the obese patient

Background

Obesity has become an increasing problem worldwide during the past few decades. Hence, surgeons and anaesthetists will care for an increasing number of obese patients in the foreseeable future, and should be prepared to provide optimal management for these individuals. This review provides an update of recent evidence regarding perioperative strategies for obese patients.

Methods

A search for papers on the perioperative care of obese patients (English language only) was performed in July 2019 using the PubMed, Scopus, Web of Science and Cochrane Library electronic databases. The review focused on the results of RCTs, although observational studies, meta-analyses, reviews, guidelines and other reports discussing the perioperative care of obese patients were also considered. When data from obese patients were not available, relevant data from non-obese populations were used.

Results and conclusion

Obese patients require comprehensive preoperative evaluation. Experienced medical teams, appropriate equipment and monitoring, careful anaesthetic management, and an adequate perioperative ventilation strategy may improve postoperative outcomes. Additional perioperative precautions are necessary in patients with severe morbid obesity, metabolic syndrome, untreated or severe obstructive sleep apnoea syndrome, or obesity hypoventilation syndrome; patients receiving home ventilatory support or postoperative opioid therapy; and obese patients undergoing open operations, long procedures or revisional surgery.

Apneic nasal oxygenation and safe apnea time during pediatric intubations by learners

BACKGROUND

Apneic nasal oxygenation (ApOx) prolongs the time to desaturation during intubation of adult patients, but there is limited prospective evidence for apneic oxygenation in pediatric patients.

AIMS

We hypothesized that ApOx during operating room intubation of pediatric patients by inexperienced learners would prolong the interval before desaturation.

METHODS

This prospective observational study compared intubation data for 196 pediatric surgical patients intubated by learners under baseline practice (no nasal cannula), to 160 patients enrolled after adoption of routine apneic nasal cannula oxygenation at 5 L/min. The primary outcome was elapsed time between anesthetic induction and pulse oximetry (SpO₂ ) falling to 95, if ever.

RESULTS

Nasal cannula oxygenation during intubation by learners delayed desaturation to SpO₂ 95 (risk ratio for this event before intubation 0.05, 95% CI 0.03-0.09; P < 0.0001).

CONCLUSIONS

Apneic oxygenation via nasal cannula during intubation of pediatric surgical patients prolongs time before desaturation, thus extending the safe interval for airway management by learners.

Effect of nasal or nasopharyngeal apneic oxygenation on desaturation during induction of anesthesia and endotracheal intubation in the operating room: A narrative review of randomized controlled trials

OBJECTIVES

To determine whether apneic oxygenation through nasal or nasopharyngeal catheters can counteract hypoxemia and desaturation during induction of anesthesia and endotracheal intubation.

DESIGN

Narrative review of randomized controlled trials.

SETTING

Operating room.

PATIENTS

295 ASA I-II patients in elective surgery.

INTERVENTION

PubMed and Embase databases were searched for studies with apneic oxygenation. The review included randomized controlled trials with apneic oxygenation through nasal or nasopharyngeal catheters as the intervention in the setting of endotracheal intubation in adults.

MEASUREMENTS

Outcome measures were time until desaturation or degree of hypoxemia.

MAIN RESULTS

Eight randomized controlled trials were included, with a total of 295 patients. Apneic oxygenation was administered by nasopharyngeal catheter in four studies and by nasal catheter in four studies. The eight included articles studied apneic oxygenation at flow rates of 3-10 l/min in ASA I-II patients undergoing elective anesthesia in the operating room. Apneic oxygenation significantly prolonged time until desaturation opposed to the control groups in seven of the eight studies of patients undergoing anesthesia for elective surgery.

CONCLUSION

Apneic oxygenation through nasal or nasopharyngeal catheters can prolong time to desaturation and decrease degree of desaturation during induction of anesthesia and endotracheal intubation in adult ASA I-II patients undergoing anesthesia for elective surgery.

A survey of practice of rapid sequence induction for caesarean section in England

BACKGROUND

In view of newer techniques of preoxygenation and laryngoscopy and recent obstetric guidelines concerning the management of difficult intubation, we aimed to evaluate the current practice of rapid sequence induction for caesarean section in England.

METHODS

In 2017, 316 questionnaire surveys were posted to all 158 hospitals with caesarean section capabilities in England. At each hospital, one questionnaire was to be completed by the obstetric anaesthetic consultant lead and one by an anaesthetic trainee. Differences in responses between consultants and trainees, regardless of their place of work, were compared for all data using the chi-square and the Fisher's exact tests.

RESULTS

One-hundred-and-eighty complete questionnaires were returned, with an overall response rate of 57%, 98 (54%) from obstetric anaesthetic consultant leads and 82 (45.6%) from trainees). Both head up (57%) and ramped (56%) were the preferred positions for preoxygenation. Less than half of respondents (43%) preoxygenated until the surgeon was scrubbed. Cricoid pressure was used by almost all respondents (98%). Thiopentone (67%) was the most commonly chosen anaesthetic induction agent and most respondents (82%) supported a change to the use of propofol. Suxamethonium (92%) was the neuromuscular blocker of choice but more than half the respondents (52%) supported a change to rocuronium. In the event of a failed intubation, the rescue supraglottic airway device of choice was the i-gel® (65%).

CONCLUSIONS

Our survey demonstrated the significant variation in the practice of rapid sequence induction for caesarean section in obstetrics in the United Kingdom.

Nasal Cannula Apneic Oxygenation Prevents Desaturation During Endotracheal Intubation: An Integrative Literature Review

Patients requiring emergency airway management may be at greater risk of acute hypoxemic events because of underlying lung pathology, high metabolic demands, insufficient respiratory drive, obesity, or the inability to protect their airway against aspiration. Emergency tracheal intubation is often required before complete information needed to assess the risk of procedural hypoxia is acquired (i.e., arterial blood gas level, hemoglobin value, or chest radiograph). During pre-oxygenation, administering high-flow nasal oxygen in addition to a non-rebreather face mask can significantly boost the effective inspired oxygen. Similarly, with the apnea created by rapid sequence intubation (RSI) procedures, the same high-flow nasal cannula can help maintain or increase oxygen saturation during efforts to secure the tube (oral intubation). Thus, the use of nasal oxygen during pre-oxygenation and continued during apnea can prevent hypoxia before and during intubation, extending safe apnea time, and improve first-pass success attempts. We conducted a literature review of nasal-cannula apneic oxygenation during intubation, focusing on two components: oxygen saturation during intubation, and oxygen desaturation time. We performed an electronic literature search from 1980 to November 2017, using PubMed, Elsevier, ScienceDirect, and EBSCO. We identified 14 studies that pointed toward the benefits of using nasal cannula during emergency intubation.

Apnoeic oxygenation by nasal cannula during airway management in children undergoing general anaesthesia: a pilot randomised controlled trial

Background

Airway management is a core clinical skill in anaesthesia. Pre-oxygenation prior to induction of anaesthesia is a standard practice to prevent desaturation. Apnoeic oxygenation in adults is effective and prolongs the time to desaturation. The effectiveness of apnoeic oxygenation in the adult is well documented; however, evidence in the paediatric is lacking. Therefore, the aim of this study was to investigate the effectiveness of apnoeic oxygenation during airway management in children.

Methods

This was a pilot randomised controlled trial. Patients were randomised to receive either apnoeic oxygenation or standard care during the induction of anaesthesia. The primary outcome was the duration of safe apnoea, defined as a composite of the time to first event, either time for SpO2 to drop to 92% or time to successfully secure the airway, and the lowest SpO2 observed during airway management. Secondary outcomes were the number of patients whose SpO2 dropped below 95% and the number of patients whose SpO2 dropped below 92%.

Results

A total of 30 patients were randomised, 15 to apnoeic oxygenation and 15 to standard care. No significant difference was observed in the time to first event (p = 0.870). However, patients randomised to apnoeic oxygenation had significantly higher SpO2 observed compared to the standard care group (p = 0.004). All patients in the apnoeic oxygenation group maintained SpO2 of 100% during airway management, compared to only six in the standard care group. SpO2 dropped below 92% in one patient, with the lowest SPO₂ recorded 73%.

Conclusion

This study suggests that providing 3 l/min oxygen by nasal cannula following pre-oxygenation contributes to maintaining high levels of oxygen saturation during airway management in children, contributing to increased patients’ safety during general anaesthesia.

Trial registration

Retrospectively registered at ClinicalTrials.gov, NCT03271827. Registered: 4 September 2017.

Apnoeic oxygenation during intubation: a systematic review and meta-analysis

Apnoeic oxygenation during intubation is used to prevent desaturation during intubation. The aim of this review was to assess whether apnoeic oxygenation during endotracheal intubation reduced the incidence of hypoxaemia. Five major databases were systematically searched for all relevant studies published up to May 2016. All study designs with a control group and a group receiving apnoeic oxygenation were included in this review. These studies were then assessed for level of evidence and risk of bias. The data were then analysed using a meta-analysis. Eleven studies (six high quality randomised controlled trials, four low quality level two studies and one low quality level three study) were found. In the meta-analysis there was strong evidence for benefit of apnoeic oxygenation in terms of improved SpO₂ in elective surgical patients, obese patients and those undergoing emergency intubation without respiratory failure. However, no significant benefit was found in patients with respiratory failure. This is the first meta-analysis to be performed on apnoeic oxygenation during intubation. Apnoeic oxygenation provides significant benefit in terms of improving SpO₂ for the majority of intubations, although there appears to be no benefit in patients whose indication for intubation is respiratory failure. Apnoeic oxygenation ought to be considered for integration into intubation protocols.

A Multicenter, Randomized Trial of Ramped Position vs Sniffing Position During Endotracheal Intubation of Critically Ill Adults

BACKGROUND

Hypoxemia is the most common complication during endotracheal intubation of critically ill adults. Intubation in the ramped position has been hypothesized to prevent hypoxemia by increasing functional residual capacity and decreasing the duration of intubation, but has never been studied outside of the operating room.

METHODS

Multicenter, randomized trial comparing the ramped position (head of the bed elevated to 25°) with the sniffing position (torso supine, neck flexed, and head extended) among 260 adults undergoing endotracheal intubation by pulmonary and critical care medicine fellows in four ICUs between July 22, 2015, and July 19, 2016. The primary outcome was lowest arterial oxygen saturation between induction and 2 minutes after intubation. Secondary outcomes included Cormack-Lehane grade of glottic view, difficulty of intubation, and number of laryngoscopy attempts.

RESULTS

The median lowest arterial oxygen saturation was 93% (interquartile range [IQR], 84%-99%) with the ramped position vs 92% (IQR, 79%-98%) with the sniffing position (P = .27). The ramped position appeared to increase the incidence of grade III or IV view (25.4% vs 11.5%, P = .01), increase the incidence of difficult intubation (12.3% vs 4.6%, P = .04), and decrease the rate of intubation on the first attempt (76.2% vs 85.4%, P = .02), respectively.

CONCLUSIONS

In this multicenter trial, the ramped position did not improve oxygenation during endotracheal intubation of critically ill adults compared with the sniffing position. The ramped position may worsen glottic view and increase the number of laryngoscopy attempts required for successful intubation.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT02497729; URL: www.clinicaltrials.gov.

Intubation using apnoeic oxygenation to prevent desaturation: A systematic review and meta-analysis

PURPOSE

To determine whether or not apnoeic oxygenation reduces the incidence of hypoxaemia during endotracheal intubation.

MATERIALS AND METHODS

A systematic search of six databases for all relevant studies until November 2016 was performed. All study designs using apnoeic oxygenation during intubation were eligible for inclusion. All studies were assessed for level of evidence and risk of bias. A meta-analysis was performed on all data using Revman 5.3.

RESULTS

Seventeen studies including 2422 patients were retrieved. Overall there was a significant reduction in the incidence of desaturation (RR=0.65; p<0.00001), critical desaturation (RR=0.61, p=0.002) and safe apnoea time (WMD=1.73min, p<0.00001). There was no significant difference in mortality (RR=0.77, p=0.08).

CONCLUSIONS

In patients whom are being intubated for any indication other than respiratory failure, apnoeic oxygenation at any flow rate 15L or greater is likely to reduce their incidence of desaturation (<90%) and critical desaturation (<80%). However, further high quality RCTs are required given the high degree of heterogeneity in many of the outcomes and subgroup analyses.