Effect of positive end-expiratory pressure on gastric insufflation during induction of anaesthesia when using pressure-controlled ventilation via a face mask: A randomised controlled trial

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.

Pre-oxygenation with high-flow oxygen through the nasopharyngeal airway compared to facemask on carbon dioxide clearance in emergency adults: a prospective randomized non-blinded clinical trial

INTRODUCTION

Before tracheal intubation, it is essential to provide sufficient oxygen reserve for emergency patients with full stomachs. Recent studies have demonstrated that high-flow nasal oxygen (HFNO) effectively pre-oxygenates and prolongs apneic oxygenation during tracheal intubation. Despite its effectiveness, the use of HFNO remains controversial due to concerns regarding carbon dioxide clearance. The air leakage and unknown upper airway obstruction during HFNO therapy cause reduced oxygen flow above the vocal cords, possibly weaken the carbon dioxide clearance.

METHODS

Patients requiring emergency surgery who had fasted < 8 h and not drunk < 2 h were randomly assigned to the high-flow group, who received 100% oxygen at 30-60 L/min through nasopharyngeal airway (NPA), or the mask group, who received 100% oxygen at 8 L/min. PaO2 and PaCO2 were measured immediately before pre-oxygenation (T0), anesthesia induction (T1), tracheal intubation (T2), and mechanical ventilation (T3). The gastric antrum's cross-sectional area (CSA) was measured using ultrasound technology at T0, T1, and T3. Details of complications, including hypoxemia, reflux, nasopharyngeal bleeding, postoperative pulmonary infection, postoperative nausea and vomiting (PONV), and postoperative nasopharyngeal pain, were recorded. The primary outcomes were PaCO2 measured at T1, T2, and T3. The secondary outcomes included PaO2 at T1, T2, and T3, CSA at T1 and T3, and complications happened during this trial.

RESULTS

Pre-oxygenation was administered by high-flow oxygen through NPA (n = 58) or facemask (n = 57) to 115 patients. The mean (SD) PaCO2 was 32.3 (6.7) mmHg in the high-flow group and 34.6 (5.2) mmHg in the mask group (P = 0.045) at T1, 45.0 (5.5) mmHg and 49.4 (4.6) mmHg (P < 0.001) at T2, and 47.9 (5.1) mmHg and 52.9 (4.6) mmHg (P < 0.001) at T3, respectively. The median ([IQR] [range]) PaO2 in the high-flow and mask groups was 404.5 (329.1-458.1 [159.8-552.9]) mmHg and 358.9 (274.0-413.3 [129.0-539.1]) mmHg (P = 0.007) at T1, 343.0 (251.6-428.7 [73.9-522.1]) mmHg and 258.3 (162.5-347.5 [56.0-481.0]) mmHg (P < 0.001) at T2, and 333.5 (229.9-411.4 [60.5-492.4]) mmHg and 149.8 (87.0-246.6 [51.2-447.5]) mmHg (P < 0.001) at T3, respectively. The CSA in the high-flow and mask groups was 371.9 (287.4-557.9 [129.0-991.2]) mm2 and 386.8 (292.0-537.3 [88.3-1651.7]) mm2 at T1 (P = 0.920) and 452.6 (343.7-618.4 [161.6-988.1]) mm2 and 385.6 (306.3-562.0 [105.5-922.9]) mm2 at T3 (P = 0.173), respectively. The number (proportion) of complications in the high-flow and mask groups is shown below: hypoxemia: 1 (1.7%) vs. 9 (15.8%, P = 0.019); reflux: 0 (0%) vs. 0 (0%); nasopharyngeal bleeding: 1 (1.7%) vs. 0 (0%, P = 1.000); pulmonary infection: 4 (6.9%) vs. 3 (5.3%, P = 1.000); PONV: 4 (6.9%) vs. 4 (7.0%, P = 1.000), and nasopharyngeal pain: 0 (0%) vs. 0 (0%).

CONCLUSIONS

Compared to facemasks, pre-oxygenation with high-flow oxygen through NPA offers improved carbon dioxide clearance and enhanced oxygenation prior to tracheal intubation in patients undergoing emergency surgery, while the risk of gastric inflation had not been ruled out.

TRIAL REGISTRATION

This trial was registered prospectively at the Chinese Clinical Research Registry on 26/4/2022 (Registration number: ChiCTR2200059192).

Bilevel positive airway pressure ventilation in patients susceptible to hypoxemia during procedural sedation for colonoscopy: a prospective randomized controlled study

BACKGROUND AND AIMS

Hypoxemia is one of the most common adverse events during colonoscopy, particularly among patients who are diagnosed with obstructive sleep apnea (OSA) or are overweight. Consequently, the objective of this study was to evaluate the effectiveness of bilevel positive airway pressure (BPAP) ventilation for patients with high-risk hypoxemia during colonoscopy with sedation.

METHODS

In this trial, 127 patients who met the eligibility criteria were randomly assigned to the BPAP oxygen group and nasal cannula (NC) group. The primary endpoint was the incidence of hypoxemia.

RESULTS

Compared with the use of NC, BPAP ventilation exhibited a significant reduction in the incidence of hypoxemia, decreasing it from 23.8% to 6.3% (absolute risk difference, 17.5%; 95% confidence interval, 5.4-29.6; P = .006). Importantly, BPAP ventilation prevented the occurrence of severe hypoxemia (9.5% vs 0%; absolute risk difference, 9.5%; 95% confidence interval, 2.3-16.7; P = .035). In addition, the BPAP group required fewer airway interventions (P < .05).

CONCLUSIONS

In individuals with OSA or overweight status, the use of BPAP ventilation during colonoscopy significantly reduced the incidence of hypoxemia. (Clinical trial registration number: ChiCTR2300073193.).

Effect of paratracheal pressure on the effectiveness of mask ventilation in obese anesthetized patients: a randomized, cross-over study

Paratracheal pressure has been recently suggested to compress and occlude the upper esophagus at the lower left paratracheal region to prevent gastric regurgitation alternative to cricoid pressure. It also prevents gastric insufflation. The aim of this randomized cross-over study was to investigate the effectiveness of paratracheal pressure on mask ventilation in obese anesthetized paralyzed patients. After the induction of anesthesia, two-handed mask ventilation was initiated in a volume-controlled mode with a tidal volume of 8 mL kg‒1 based on ideal body weight (IBW), a respiratory rate of 12 breaths min- 1, and positive end-expiratory pressure of 10 cmH2O. Expiratory tidal volume and peak inspiratory pressure were recorded alternately with or without the application of 30 Newtons (approximately 3.06 kg) paratracheal pressure during a total of 16 successive breaths over 80 s. Association of patient characteristics with the effectiveness of paratracheal pressure on mask ventilation, defined as the difference in expiratory tidal volume between the presence or absence of paratracheal pressure were evaluated. In 48 obese anesthetized paralyzed patients, expiratory tidal volume was significantly higher with the application of paratracheal pressure than without paratracheal pressure [496.8 (74.1) mL kg- 1 of IBW vs. 403.8 (58.4) mL kg- 1 of IBW, respectively; P < 0.001]. Peak inspiratory pressure was also significantly higher with the application of paratracheal pressure compared to that with no paratracheal pressure [21.4 (1.2) cmH2O vs. 18.9 (1.6) cmH2O, respectively; P < 0.001]. No significant association was observed between patient characteristics and the effectiveness of paratracheal pressure on mask ventilation. Hypoxemia did not occur in any of the patients during mask ventilation with or without paratracheal pressure. The application of paratracheal pressure significantly increased both the expiratory tidal volume and peak inspiratory pressure during face-mask ventilation with a volume-controlled mode in obese anesthetized paralyzed patients. Gastric insufflation was not evaluated in this study during mask ventilation with or without paratracheal pressure.

Pressure-controlled versus manual facemask ventilation for anaesthetic induction in adults: A randomised controlled non-inferiority trial

BACKGROUND

Pressure-controlled face mask ventilation (PC-FMV) with positive end-expiratory pressure (PEEP) after apnoea following induction of general anaesthesia prolongs safe apnoea time and reduces atelectasis formation. However, depending on the set inspiratory pressure, a delayed confirmation of a patent airway might occur. We hypothesised that by lowering the peak inspiratory pressure (PIP) when using PC-FMV with PEEP, confirmation of a patent airway would not be delayed as studied by the first return of CO2 , compared with manual face mask ventilation (Manual FMV).

METHODS

This was a single-centre, randomised controlled non-inferiority trial. Seventy adult patients scheduled for elective day-case surgery under general anaesthesia with body mass index between 18.5 and 29.9 kg m-2 , American Society of Anesthesiologists (ASA) classes I-III, and without anticipated difficult FMV, were included. Before the start of pre-oxygenation and induction of general anaesthesia, participants were randomly allocated to receive ventilation with either PC-FMV with PEEP, at a PIP of 11 and a PEEP of 6 cmH2 O or Manual FMV, with the adjustable pressure-limiting valve set at 11 cmH2 O. The primary outcome variable was the number of ventilatory attempts needed until confirmation of a patent airway, defined as the return of at least 1.3 kPa CO2 .

RESULTS

The return of ≥1.3 kPa CO2 on the capnography curve was observed after mean ± SD, 3.6 ± 4.2 and 2.5 ± 1.9 ventilatory attempts/breaths with PC-FMV with PEEP and Manual FMV, respectively. The difference in means (1.1 ventilatory attempts/breaths) had a 99% CI of -1.0 to 3.1, within the accepted upper margin of four breaths for non-inferiority.

CONCLUSION

Following induction of general anaesthesia, PC-FMV with PEEP was used without delaying a patent airway as confirmed with capnography, if moderate pressures were used.

Ultrasound Assessment of Gastric Volume in Parturients After High-Flow Nasal Oxygen Therapy

BACKGROUND

High-flow nasal oxygen (HFNO) therapy is widely used in critical care obstetrics to improve oxygenation. Much of the benefit of HFNO is linked to the creation of modest levels of positive airway pressure. Pregnant women are generally considered to be at high risk of regurgitation and aspiration. It is unknown whether HFNO may cause gas insufflation into the stomach and further increase this risk. Therefore, this study aimed to systematically evaluate the possible safety effects of HFNO on gastric volume in healthy fasted parturients.

METHODS

Sixty fasted parturients scheduled for elective cesarean delivery were enrolled in an observer-blinded, prospective, interventional study. We used ultrasonography to assess changes of antral cross-sectional area (CSA) and gastric volume before and after a 20-minute treatment with HFNO at a rate of 50 L·min -1 . The primary outcome was the change in gastric volume from before to after HFNO therapy, and the secondary outcome was the distribution of antral grades.

RESULTS

In semirecumbent right lateral position, the antral CSA at baseline and after treatment with HFNO was 3.81 (3.01-4.72) cm 2 and 3.79 (3.03-4.54) cm 2 , respectively. The estimated fluid volume at baseline and after treatment with HFNO was 38.51 (33.39-54.62) mL and 39.71 (32.00-52.82) mL, respectively. All participants had either a grade 0 or grade 1 antrum, and most of them had a grade 0 antrum. There was no significant difference in gastric volume and distribution of antral grades before and after HFNO therapy. Gastric air distension was not shown in any of the parturients either at baseline or after treatment with HFNO.

CONCLUSIONS

Treatment with HFNO for 20 minutes at flow rates up to 50 L·min -1 did not increase gastric volume in term pregnant women breathing spontaneously when evaluated by gastric ultrasonography.

High-Flow Nasal Cannula for Apneic Oxygenation in Obese Patients for Elective Surgery: A Systematic Review and Meta-Analysis

BACKGROUND

Obese patients desaturate rapidly during the apneic period after induction of anesthesia for elective surgery. Administration of oxygen using high-flow nasal cannulae (HFNCs) may prevent desaturation in nonobese patients compared to facemask (FM) preoxygenation. The aim of this meta-analysis was to compare the effectiveness of HFNC to FM preoxygenation techniques in reducing preintubation desaturation in obese patients undergoing elective surgery.

METHODS

This study protocol was registered on PROSPERO (CRD42022309391). Adult studies that compared HFNC and FM preoxygenation in obese patients requiring general anesthesia for elective surgery were included. The primary outcome was desaturation resulting in oxygen saturation of <92% from induction of anesthesia until intubation. Secondary outcomes included the lowest arterial oxygen content before intubation expressed in mm Hg, safe apnea time expressed in seconds, the lowest oxygen saturation before intubation expressed as a percentage, patient-reported discomfort, the need for rescue ventilation, and the incidence of aspiration of gastric contents during intubation. Risk of bias was assessed using the Cochrane Collaboration tool. Certainty was assessed following the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

Six studies including 351 participants were eligible for analysis. There was no difference in odds of oxygen desaturation <92% between HFNC and FM (odds ratio [OR], 0.49; 95% confidence interval [CI], 0.15-1.63; P = .24). The HFNC group had a significantly longer safe apnea time (mean difference [MD], -124.20 with 95% CI, -200.47 to -47.93; P = .001). There was no difference between HFNC and FM in the lowest arterial oxygen content (MD, -23.90; 95% CI, -88.64 to 40.85; P = .47) and the lowest peripheral oxygenation saturation (MD, -0.47 with 95% CI, -5.07 to 4.12; P = .84). HFNC had a lower odd of discomfort than FM (OR, 0.13; 95% CI, 0.03-0.52; P = .004). There was no difference in the odds of aspiration of gastric contents between HFNC and FM (OR, 0.33; 95% CI, 0.01-8.21; P = .50). The risk of bias for our primary and secondary outcomes was low. The GRADE assessment for our primary outcome indicated a low level of certainty. For secondary outcomes, the GRADE assessment indicated a very low certainty for all outcomes except for patient discomfort, which was indicated as a moderate level of certainty.

CONCLUSIONS

There may be no difference between HFNC and FM preoxygenation in preventing oxygen desaturation <92% or the lowest oxygen saturation before intubation. Preparation remains important to prevent and manage desaturation during induction of obese patients.

Optimal Insertion Depth of Gastric Decompression Tube with a Thermistor for Patients Undergoing Laparoscopic Surgery in Trendelenburg Position

Monitoring core temperature is crucial for maintaining normothermia during general anesthesia. Insertion of a gastric decompression tube (GDT) may be required during laparoscopic surgery. Recently, a newly designed GDT with a thermistor for monitoring esophageal temperature has been introduced. The purpose of the present study was to evaluate the optimal insertion depth of a GDT with a thermistor. Forty-eight patients undergoing elective laparoscopic surgery in the Trendelenburg position were included in the study. The GDT was inserted to a depth of nose-earlobe-xiphoid distance (NEX) + 12 cm and withdrawn sequentially, 2 cm at a time, at 5-min intervals. Temperatures of the GDT thermistor were compared with the core temperature of the tympanic membrane (TM) using Bland and Altman analysis. The correlation between optimal insertion depth of the GDT and anatomical distance (cricoid cartilage to the carina, CCD; carina to the left hemidiaphragm, CLHD) was evaluated, and a mathematical model to predict the optimal insertion depth of the GDT with a thermistor was calculated. Temperatures of TM and GDT thermistor at NEX + 4 cm showed good agreement and strong correlation, but better agreement and stronger correlation were seen at the actual location with the most minor temperature differences. The optimal insertion depth of the GDT was estimated as -15.524 + 0.414 × CCD - 0.145 × CLHD and showed a strong correlation with the actual GDT insertion depth (correlation coefficient 0.797, adjusted R² = 0.636). The mathematical formula using CCD and CLHD would be helpful in determining the optimal insertion depth of a GDT with a thermistor.

Nasal Continuous Positive Airway Pressure as a Preferred Airway Management During IV Sedation of Obese Patients With Obstructive Sleep Apnea Undergoing Functional Luminal Imaging Probe Panometry

The functional luminal imaging probe (FLIP) utilizes high-resolution planimetry to provide information regarding esophagogastric junction (EGJ) diameter, EGJ distensibility, and reactive contractile patterns of the esophageal body. This is an FDA-approved measurement tool utilized to both diagnose and measure various upper gastrointestinal disorders. While patients are sedated during FLIP panometry, significant respiratory variations can affect the quality of FLIP panometry results. Nasal continuous positive airway pressure (CPAP) can be utilized to prevent intraoperative or postoperative hypoxia in obese patients as well as those with obstructive sleep apnea (OSA). In this retrospective chart review, we compared obese patients with a diagnosis of OSA who underwent FLIP panometry utilizing nasal CPAP as airway management against a group who underwent the same procedure with a nasal cannula to evaluate the incidence of hypoxia, hypercapnia, variation in cardiovascular dynamics, and the quality of FLIP panometry readings.

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.

Evaluation of adequacy of ventilation and gastric insufflation at three levels of inspiratory pressure for facemask ventilation during induction of anaesthesia: A randomised controlled trial

BACKGROUND

In this study, we aimed to compare three inspiratory pressures during face-mask ventilation in paralysed patients regarding the subsequent incidence of gastric insufflation and the adequacy of lung ventilation.

METHODS

In this randomised controlled trial, we included adult patients undergoing elective surgery under general anaesthesia. The patients were randomly allocated to receive positive inspiratory pressure (PIP) of 10, 15, or 20 cmH₂O during pressure-controlled mask ventilation. Antral cross-sectional area (CSA) was assessed by ultrasound at baseline before mask ventilation and after endotracheal intubation and gastric insufflation was defined as increased CSA after endotracheal intubation > 30% of the baseline measurement. The primary outcome was the incidence of gastric insufflation. Other outcomes included the tidal volume, and the incidence of adequate ventilation (tidal volume of 6-10 mL/kg predicted body weight).

RESULTS

We analysed data from 36 patients in each group. The number of patients with gastric insufflation was lowest in the PIP 10 group (0/36 [0%]) in comparison with PIP 15 (2/36 [19%] and PIP 20 36/36 [100%] groups (P-values of 0.019 and < 0.001, respectively). The probability of adequate ventilation at any time point was the highest in PIP 10, followed by PIP 15, and was the lowest in the PIP 20 group.

CONCLUSION

An inspiratory pressure of 10 cmH₂O in paralysed patients provided the least risk of gastric insufflation with adequate ventilation during induction of general anaesthesia compared to inspiratory pressure of 15- and 20 cmH₂O.

Comparison of the third-generation streamlined liner of the pharynx airway (SLIPA-3G) with the laryngeal mask airway supreme for laparoscopic cholecystectomy: a randomized prospective study

Background

The third-generation streamlined liner of the pharynx airway (SLIPA-3G) is a new-generation supraglottic airway device (SAD) that is non-cuffed and disposable, with a sealing pressure that varies dynamically with the airway pressure. This study compared the SLIPA-3G with the laryngeal mask airway supreme (LMAS) in patients undergoing laparoscopic cholecystectomy.

Methods

Two hundred and twenty patients scheduled for laparoscopic cholecystectomy were randomly allocated to either the SLIPA-3G group or the LMAS group. Data were collected on the patients’ hemodynamic parameters at different time points, ease of insertion, fiberoptic view, oropharyngeal leak pressure (OLP) at different time points and SAD-related complications.

Results

The mean OLP immediately after device placement in the LMAS group was significantly higher than that of the SLIPA-3G group (31.34 ± 6.99 cmH₂O vs.28.94 ± 6.01 cmH₂O, P = 0.008, 95% CI 0.62–4.17). The OLPs of the two groups were not significantly different after the induction of a pneumoperitoneum until the end of surgery. The OLP increased gradually through the course of the operation in the SLIPA-3G group (P value = 0.035) but not in the LMAS group (P value = 0.945). There was no significant difference between the two groups in hemodynamic parameters, insertion time and success rate, fiberoptic view and complication rate.

Conclusions

The SLIPA-3G and LMAS were associated with comparable OLPs, hemodynamic parameters, ease of insertion, fiberoptic views and complication rates when used during laparoscopic cholecystectomy. The SLIPA-3G can be used as an effective alternative to the LMAS in patients undergoing laparoscopic surgeries.

Recovery of lower oesophageal barrier function: a pilot study comparing a mixture of atropine and neostigmine and sugammadex: A randomised controlled pilot study

BACKGROUND

The lower oesophageal sphincter (LOS) barrier serves to prevent regurgitation of gastric contents. Although general anaesthesia depresses its function, its recovery process during emergence from anaesthesia has not been systematically examined.

OBJECTIVE

To explore whether recovery of lower oesophageal barrier function differed between patients receiving a mixture of 1 mg atropine and 2 mg neostigmine and those receiving 2 mg kg-1 sugammadex during emergence from anaesthesia.

DESIGN

An unblinded randomised controlled pilot study.

SETTING

A single university hospital from January 2016 to December 2018.

PATIENTS

A total of 20 non-obese adult females undergoing minor surgery.

INTERVENTION

The patients were randomly assigned to a group either receiving atropine and neostigmine or sugammadex for reversal of rocuronium.

MAIN OUTCOME MEASURES

Through use of the high-resolution manometry technique, the lower oesophageal barrier pressure (PBAR: primary variable) defined as a pressure difference between pressures at the LOS and the stomach was measured at five distinguishable time points during emergence from total intravenous anaesthesia. A mixed effects model for repeated measures was used to test the hypothesis.

RESULTS

In all patients baseline PBAR values were positive even under muscle paralysis and general anaesthesia before administration of reversal agents, and did not differ between the groups (P = 0.299). During recovery from muscle paralysis and general anaesthesia, PBAR (mean ± SD) significantly increased (P = 0.004) from 17.0 ± 2.9 to 21.0 ± 5.0 mmHg in the atropine and neostigmine group (n = 8) and from 19.1 ± 9.0 to 24.5 ± 12.7 mmHg in the sugammadex group (n = 11). PBAR significantly increased immediately after return of consciousness in both groups, whereas return of muscle tone, lightening of anaesthesia and tracheal extubation did not change it.

CONCLUSION

Recovery of the lower oesophageal barrier function does not differ between patients receiving either atropine and neostigmine or sugammadex and is completed after recovery of consciousness from general anaesthesia.

TRIAL REGISTRATION

UMIN Clinical Trials Registry: UMIN000020500: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&recptno=R000023594&type=summary&language=E.

Body position and the effectiveness of mask ventilation in anaesthetised paralysed obese patients: A randomised cross-over study

BACKGROUND

Airway management is more challenging in the obese. Compared with the supine position, the sitting position can decrease the collapsibility of the upper airway and improve respiratory mechanics.

OBJECTIVE

The aim of this study was to evaluate the 25° semisitting position on the effectiveness of mask ventilation in anaesthetised paralysed obese patients.

DESIGN

A randomised, cross-over study.

SETTING

Medical centre managed by a university tertiary hospital.

PATIENTS

Thirty-eight obese adults scheduled for general anaesthesia.

METHODS

After anaesthesia and paralysis, two-handed mask ventilation was performed in the supine and 25° semi-sitting positions with a cross-over, in a randomised order. During mask ventilation, mechanical ventilation was delivered with a pressure-controlled mode with a peak inspiratory pressure of 15 cmH2O, a respiratory rate of 15 bpm, and no positive end-expiratory pressure. Ventilatory outcomes were based upon lean body weight.

MAIN OUTCOMES

Exhaled tidal volume (ml kg-1), respiratory minute volume (ml kg-1 min-1), and the occurrence of inadequate ventilation, defined as an exhaled tidal volume less than 4 ml kg-1, or absence of end-tidal CO2 recording.

RESULTS

Exhaled tidal volume (mean ± SD) in the 25° semi-sitting position was higher than in the supine position, 9.3 ± 2.7 vs. 7.6 ± 2.4 ml kg-1; P less than 0.001. Respiratory minute volume was improved in the 25° semisitting position compared with that in the supine position, 139.6 ± 40.7 vs. 113.4 ± 35.7 ml kg-1 min-1; P less than 0.001.

CONCLUSION

The 25° semisitting position improved mask ventilation compared with the supine position in anaesthetised paralysed obese patients.

TRIAL REGISTRY NUMBER

ClinicalTrials.gov (NCT03996161).

Effects of neuromuscular blocking agents on the clinical performance of i-gel® and surgical condition in elderly patients undergoing hand surgery: a prospective randomized controlled trial

Background: The effects of neuromuscular blocking agents on the clinical performance of supraglottic airway devices and surgical condition in elderly patients undergoing hand surgery have not been established. We evaluated the effects of rocuronium on the clinical performance of an i-gel^® supraglottic device and surgical condition in elderly patients undergoing orthopedic hand surgery. Methods: Patients aged 65-85 years were randomized to receive either rocuronium (rocuronium group) or saline (control group). We compared the rates of successful insertion of the i-gel on the first attempt as a primary outcome and also assessed the adequacy of i-gel maintenance during controlled ventilation, anesthetic requirement, surgical condition, and recovery time. Results: The rates of successful insertion of the i-gel on a first attempt were 93.1% in the rocuronium group versus 82.1% in the control group (P = 0.423). Peak inspiratory pressure (PIP) was lower in the rocuronium group than in the control group (15.2 vs. 17.9 cmH₂O, respectively, P = 0.028). Spontaneous breathing was less common in the rocuronium group (24.1% vs. 57.1%, respectively, P = 0.011). The requirement of additional fentanyl to suppress spontaneous breathing or patient movement was less in the rocuronium group than in the control group (24.1% vs. 50.0%, respectively, P = 0.043). Surgical condition did not differ between the two groups. Recovery time was shorter in the rocuronium group than in the control group (8.4 vs. 9.9 min, respectively, P = 0.030). Conclusions: Rocuronium did not enhance the success rate of inserting the i-gel^® or the surgical condition in elderly patients. However, using rocuronium reduced PIP, the frequency of spontaneous breathing, the requirement for additional fentanyl and patients' recovery time.