Real-time Detection of Gastric Insufflation Related to Facemask Pressure–controlled Ventilation Using Ultrasonography of the Antrum and Epigastric Auscultation in Nonparalyzed Patients

Oropharyngeal leak pressure of the LMA Protector™ vs the LMA Supreme™; a prospective, randomized, controlled clinical trial

BACKGROUND

Clinical characteristics such as oropharyngeal leak pressure (OLP) and ventilation peak pressure are important factors for successful use of supraglottic airway devices in general anaesthesia. We hypothesized that the LMA Protector™ compared to the LMA Supreme™ may develop a higher OLP, which could be of clinical significance.

METHODS

Ninety-six patients were randomized to the LMA Protector™ or LMA Supreme™ groups. We measured oropharyngeal leak pressure within 5 minutes after insertion of the supraglottic airway device with a standardized cuff pressure at 60 cm H₂ O. Secondary parameters, such as insertion time of the supraglottic airway device, the number of attempts inserting the supraglottic airway device and the gastric tube, volume of gastric contents, and maximum airway pressure, as well as pulse oximetry throughout the operation were measured. Further, blood staining after removal of the supraglottic airway device and postoperative airway morbidity 3 hours after surgery were determined.

RESULTS

The mean difference of oropharyngeal leak pressure was 5.2 (95% CI 2.8-7.6), ie, 30.9 (7.4) cmH₂ O for the LMA Protector™ vs 25.6 (4.4) cmH₂ O for the LMA Supreme™ (P < 0.001; mean(SD)). Similarly, there was a mean difference between OLP and maximal ventilation peak pressure 5.6 (95% CI 3.1-8.2) ie 19.6 (7.7) cmH₂ O for the LMA Protector™ vs 14.0 (4.4) cmH₂ O for the LMA Supreme™ (P < 0.001). No difference was found between the groups for other secondary parameters, as well as postoperative airway morbidity.

CONCLUSION

The LMA Protector™ enabled a higher OLP compared to the LMA Supreme™. This finding may be important for patients requiring a higher peak pressure for sufficient supraglottic airway device ventilation.

Bag-Mask Ventilation during Tracheal Intubation of Critically Ill Adults

BACKGROUND

Hypoxemia is the most common complication during tracheal intubation of critically ill adults and may increase the risk of cardiac arrest and death. Whether positive-pressure ventilation with a bag-mask device (bag-mask ventilation) during tracheal intubation of critically ill adults prevents hypoxemia without increasing the risk of aspiration remains controversial.

METHODS

In a multicenter, randomized trial conducted in seven intensive care units in the United States, we randomly assigned adults undergoing tracheal intubation to receive either ventilation with a bag-mask device or no ventilation between induction and laryngoscopy. The primary outcome was the lowest oxygen saturation observed during the interval between induction and 2 minutes after tracheal intubation. The secondary outcome was the incidence of severe hypoxemia, defined as an oxygen saturation of less than 80%.

RESULTS

Among the 401 patients enrolled, the median lowest oxygen saturation was 96% (interquartile range, 87 to 99) in the bag-mask ventilation group and 93% (interquartile range, 81 to 99) in the no-ventilation group (P = 0.01). A total of 21 patients (10.9%) in the bag-mask ventilation group had severe hypoxemia, as compared with 45 patients (22.8%) in the no-ventilation group (relative risk, 0.48; 95% confidence interval [CI], 0.30 to 0.77). Operator-reported aspiration occurred during 2.5% of intubations in the bag-mask ventilation group and during 4.0% in the no-ventilation group (P = 0.41). The incidence of new opacity on chest radiography in the 48 hours after tracheal intubation was 16.4% and 14.8%, respectively (P = 0.73).

CONCLUSIONS

Among critically ill adults undergoing tracheal intubation, patients receiving bag-mask ventilation had higher oxygen saturations and a lower incidence of severe hypoxemia than those receiving no ventilation. (Funded by Vanderbilt Institute for Clinical and Translational Research and others; PreVent ClinicalTrials.gov number, NCT03026322.).

Ultra-modified rapid sequence induction with transnasal humidified rapid insufflation ventilatory exchange: Challenging convention

During positive pressure ventilation, gastric inflation and subsequent pulmonary aspiration can occur. Rapid sequence induction (RSI) technique is an age-old formula to prevent this. We adopted a novel approach of RSI for patients with high risk of aspiration and evaluated it further in patients undergoing laparoscopic surgeries. We believe that, in patients with risk of gastric insufflation and pulmonary aspiration, transnasal humidified rapid-insufflation ventilatory exchange can be useful in facilitating pre- and apnoeic oxygenation till tracheal isolation is achieved.

Effects of Stomach Inflation on Cardiopulmonary Function and Survival During Hemorrhagic Shock: A Randomized, Controlled, Porcine Study

BACKGROUND

Ventilation of an unprotected airway may result in stomach inflation. The purpose of this study was to evaluate the effect of clinically realistic stomach inflation on cardiopulmonary function during hemorrhagic shock in a porcine model.

METHODS

Pigs were randomized to a sham control group (n = 9), hemorrhagic shock (35 mL kg over 15 min [n = 9]), and hemorrhagic shock combined with stomach inflation (35 mL kg over 15 min and 5 L stomach inflation [n = 10]).

RESULTS

When compared with the control group, hemorrhagic shock (n = 9) increased heart rate (103 ± 11 vs. 146 ± 37 beats min; P = 0.002) and lactate (1.4 ± 0.5 vs. 4.0 ± 1.9 mmol L; P < 0.001), and decreased mean arterial blood pressure (81.3 ± 12.8 vs. 35.4 ± 8.1 mmHg; P < 0.001) and stroke-volume index (38.1 ± 6.4 vs. 13.6 ± 4.8 mL min m; P < 0.001). Hemorrhagic shock combined with stomach inflation (n = 10) versus hemorrhagic shock only (n = 9) increased intra-abdominal pressure (27.0 ± 9.3 vs. 1.1 ± 1.0 mmHg; P < 0.001), and decreased stroke-volume index (9.9 ± 6.0 vs. 20.8 ± 8.5 mL min m; P = 0.007), and dynamic respiratory system compliance (10.8 ± 4.5 vs. 38.1 ± 6.1 mL cmH2O; P < 0.001). Before versus after stomach evacuation during hemorrhagic shock, intra-abdominal pressure decreased (27.0 ± 9.3 vs. 9.8 ± 5.4 mmHg; P = 0.042). Survival in the sham control and hemorrhagic shock group was 9 of 9, respectively, and 3 of 10 after hemorrhagic shock and stomach inflation (P < 0.001).

CONCLUSIONS

During hemorrhagic shock stomach inflation caused an abdominal compartment syndrome and thereby impaired cardiopulmonary function and aerobic metabolism, and increased mortality. Subsequent stomach evacuation partly reversed adverse stomach-inflation triggered effects.

Comparison of Arterial Oxygenation and Acid-Base Balance with the use of Transnasal Humidified Rapid-insufflation Ventilatory Exchange versus Tidal Volume Breathing with Continuous Positive Airway Pressure for Preoxygenation and Apneic Ventilation

Background:

Preoxygenation and apneic ventilation prolong apnea time without desaturation.

Aims:

The primary objective of this study is to compare arterial oxygenation during the periods of apnea following preoxygenation and apneic ventilation with tidal volume breathing for 3 min with continuous positive airway pressure (CPAP) versus with transnasal humidified rapid-insufflation ventilatory exchange (THRIVE).

Settings and Designs:

This prospective randomized study was conducted in 20 adult patients at a tertiary care institution.

Subjects and Methods:

Group C patients (n = 10) were preoxygenated with 100% oxygen using a face mask at a rate of 6 L/min for 3 min with CPAP of 15 cm of H₂O. In Group H, oxygen was administered using THRIVE at 30 L/min for 3 min. Apneic ventilation was given in Group C with 10 L/min oxygen with CPAP of 15 cm H₂O and in Group H with THRIVE at 60 L/min. The endpoint was desaturation to 90% or maximum duration of 12 min.

Statistical Analysis Used:

Chi-square test and Mann–Whitney test.

Results:

Both groups tolerated apnea for 12 min without desaturation. PaO₂ in Group C was significantly higher than Group H from 3 min of apnea to 12 min. The PaCO₂ was significantly lower in Group C from 6 min. The pH was comparable in both groups except at 12 min with Group H having significantly lower pH.

Conclusion:

Tidal volume breathing with CPAP resulted in significantly higher arterial oxygen levels than THRIVE, though both modalities were equally effective in prolonging apnea time without desaturation up to 12 min. Group C showed an added advantage of lower PaCO₂ with less acidemia.

Guidelines for the management of tracheal intubation in critically ill adults

These guidelines describe a comprehensive strategy to optimize oxygenation, airway management, and tracheal intubation in critically ill patients, in all hospital locations. They are a direct response to the 4^th National Audit Project of the Royal College of Anaesthetists and Difficult Airway Society, which highlighted deficient management of these extremely vulnerable patients leading to major complications and avoidable deaths. They are founded on robust evidence where available, supplemented by expert consensus opinion where it is not. These guidelines recognize that improved outcomes of emergency airway management require closer attention to human factors, rather than simply introduction of new devices or improved technical proficiency. They stress the role of the airway team, a shared mental model, planning, and communication throughout airway management. The primacy of oxygenation including pre- and peroxygenation is emphasized. A modified rapid sequence approach is recommended. Optimal management is presented in an algorithm that combines Plans B and C, incorporating elements of the Vortex approach. To avoid delays and task fixation, the importance of limiting procedural attempts, promptly recognizing failure, and transitioning to the next algorithm step are emphasized. The guidelines recommend early use of a videolaryngoscope, with a screen visible to all, and second generation supraglottic airways for airway rescue. Recommendations for emergency front of neck airway are for a scalpel-bougie-tube technique while acknowledging the value of other techniques performed by trained experts. As most critical care airway catastrophes occur after intubation, from dislodged or blocked tubes, essential methods to avoid these complications are also emphasized.

Determination of the optimal inspiratory pressure providing adequate ventilation while minimizing gastric insufflation using real-time ultrasonography in Chinese children: a prospective, randomized, double-blind study

Background

During facemask ventilation, gastric insufflation is defined as appearance of a comet-tail or an acoustic shadow on ultrasonography. Ultrasonographic measurement of antral cross-section area (CSA) may reflect an insufflated antrum and provide interesting semi-quantitative data in regard to the gastric insufflation. This study aimed to determine the appropriate level of inspiratory pressure sufficient to provide adequate pulmonary ventilation with a lower occurrence of gastric insufflation during facemask pressure-controlled ventilation using real-time ultrasonography in paralyzed children.

Methods

Ninety children, ASA I-II, aged from 2 to 4 years, scheduled for general anesthesia were enrolled in this randomized and double-blinded study. Children were randomized into one of the five groups (P8, P10, P12, P14, and P16) defined by the applied inspiratory pressure during facemask ventilation: 8, 10, 12, 14, and 16 cm H₂O. Anesthesia induction was conducted with fentanyl and propofol. Rocuronium was administrated as a muscle relaxant. After rocuronium administration, facemask ventilation was performed for 120 s. Gastric insufflation (GI+) was detected by ultrasonography, and the antral CSA before and after facemask ventilation were also measured using ultrasonography. Respiratory variables were monitored.

Results

Gastric insufflation was detected in 32 children (3/18 in group P8, 5/18 in group P10, 7/18 in group P12, 8/16 in group P14, and 9/14 in group P16). The antral CSA after facemask ventilation statistically increased in subgroups P14 GI+ and P16 GI+ for whom gastric insufflation was detected by ultrasonography, whereas it did not change statistically in other groups. Lung ventilation was inadequate for group P8 or P10.

Conclusion

We concluded that an inspiratory pressure of 12 cm H₂O is sufficient to provide adequate ventilation with a lower occurrence of gastric insufflation during induction of general anesthesia in paralyzed Chinese children aged from 2 to 4 years old.

Trial registration

(ChiCTR-IPR-16007960). Registered 21 February 2016

Conclusion heading: Ultrasound for determining gastric insufflation

A randomized comparison of volume- and pressure-controlled ventilation in children with the i-gel: Effects on peak inspiratory pressure, oropharyngeal leak pressure, and gastric insufflation

BACKGROUND

The i-gel provides good airway sealing but gastric insufflation may occur when peak inspiratory pressure (PIP) exceeds the sealing pressure of the i-gel without a gastric tube. Pressure-controlled ventilation (PCV) provides lower PIP compared with volume-controlled ventilation (VCV) and low PIP may reduce the incidence of gastric insufflation in children during positive pressure ventilation. This study was designed to evaluate PIP, oropharyngeal leak pressure, and gastric insufflation during VCV or PCV in children undergoing general anesthesia with i-gel without a gastric tube in situ.

METHODS

A prospective, randomized-controlled study was conducted. Thirty-four children, aged 6 to 84 months, were randomly allocated into the VCV or PCV group. Fiberoptic bronchoscopy was performed to confirm appropriate position of i-gel. Oropharyngeal leak pressure and PIP were measured after i-gel insertion, after caudal block, and after surgery. Ultrasonography was performed to detect gastric insufflation. Gastric tube was not inserted.

RESULTS

PIP in cm H2O was significantly lower in the PCV group than in the VCV group after i-gel insertion (10 [9-12] vs 12 [11-15], P = .021), after caudal block (11 [10-12] vs 13 [11-15], P = .014), and after surgery (10 [10-12] vs 13 [11-14], P = .002). There was no difference in the incidence of gastric insufflation between the 2 groups (4/17 in the VCV group and 3/17 in the PCV group) (P > .999).

CONCLUSION

When i-gel was used without a gastric tube, gastric insufflation occurred regardless of the ventilation modes, which provided different PIP.

Comparison of modified chin lift technique with EC technique for mask ventilation in adult apneic patients

Background:

Mask ventilation (MV) is an essential basic life support skill. We used chin lift maneuver for MV and named as modified chin lift technique (MCL). EC technique is most common technique used for MV.

Aims:

The aim of this study is to compare the efficacy of both techniques for MV in term of expired tidal volume (TV). Secondarily, we also assessed the effect of experience on the performance of these both techniques.

Settings and Design:

The study area was operation theater of our hospital. This was a prospective, randomized, crossover study.

Methods:

A total 108 adults undergoing elective surgery under general anesthesia were recruited. In all patients, operators (novice/anesthesiologist) randomly performed both techniques either to start with EC or MCL technique. Expired TV was measured for one minute for each technique.

Statistical Analysis:

Paired t-test was used to compare TV.

Results and Conclusion:

The mean TV was significantly higher in MCL group than EC group (528.08 [104.96] ml vs. 483.39 [103] ml; P < 0.001). The novice (521.89 [117.9] ml vs. 478.70 [130.29] ml; P < 0.001) as well as anesthesiologists (534.27 [110.85] ml vs. 488.08 [111.6] ml; P < 0.001) was able to generate significantly more TV with MCL technique than EC technique. The TV did not differ significantly between novice and anesthesiologist for EC technique (P = 0.474) or MCL technique (P = 0.187). Novices as well as anesthesiologist felt MCL technique more satisfactory (70%).

Clinical Trial Registration:

CTRI/2016/04/006874.

Manual vs. pressure-controlled facemask ventilation for anaesthetic induction in paralysed children: a randomised controlled trial

BACKGROUND

During anaesthetic induction with a facemask, the inconsistent inspiratory flow with manual ventilation (MV) raises the peak airway pressure (PAP), which can be significantly higher than PAP during pressure-controlled ventilation (PCV). In this study, PAP was compared between MV and PCV at the same tidal volume of 8-10 ml/kg during facemask ventilation for anaesthetic induction in children. The occurrence of gastric insufflation (GI) was evaluated with ultrasonography and stethoscopic auscultation.

METHODS

Forty-eight children, aged 0.5-7 years, undergoing elective urologic surgery were randomly allocated into either Group MV or Group PCV. Under light sedation with thiopental iv., ultrasonography (US) was performed and the gastric antrum was identified. After additional thiopental and rocuronium administration, facemask ventilation with a tidal volume of 8-10 ml/kg was performed for 3 min, whereas respiratory parameters were recorded at 1 min intervals. Real-time US and stethoscopic auscultation were performed for evaluation of GI.

RESULTS

In the MV group, PAP was higher at all the time points compared with the PCV group (14 vs. 9.5, 15 vs. 10 and 15 vs. 9 cmH2 O, all P < 0.05). However, there was no difference in the GI occurrence between Group MV and Group PCV (7 vs. 3, P = 0.284). There was no difference between PAP in patients with GI and without GI (P > 0.05). Ultrasonography was more sensitive in detecting GI than the stethoscopic auscultation (10 vs. 5). Gastric antral area was expanded after facemask ventilation in both groups, but there were no intergroup differences.

CONCLUSION

Although PCV provided lower PAP than MV at the same tidal volume, the risk of GI may not be eliminated during facemask ventilation in paralysed small children.

Should anesthesiologists have to confirm effective facemask ventilation before administering the muscle relaxant?

There is ongoing controversy as to whether effective facemask ventilation (FMV) should be established following induction of anesthesia before a muscle relaxant is administered. The rationale for such practice is the belief that, should FMV be ineffective, non-paralyzed patients can be woken up, and subsequently an alternative airway management can be considered. However, the chances of successfully restoring adequate spontaneous respiration before severe hypoxemia develops in an anesthetized, apneic patient who is prone to anesthetic-induced respiratory depression and airway collapse are very small. On the other hand, the overall evidence shows that muscle relaxation is likely to improve or leave unchanged, but not to worsen, the quality of FMV. Furthermore, muscle relaxation will facilitate placement of a supraglottic airway device and endotracheal intubation, interventions which may become essential should the patient become hypoxemic during failed FMV. Thus, the earliest administration of a muscle relaxant following induction of anesthesia may well be the most effective and safest practice. Insistence on demonstration of adequate FMV before administration of a muscle relaxant is more of a ritual than an evidence-based practice. It should therefore be abandoned.

[Contribution of ultrasonography for the preoperative assessment of gastric contents]

The assessment of the risk of pulmonary aspiration of gastric contents may be difficult in the preoperative period, apart from typical circumstances. The development of ultrasonography in anesthesia and critical care has led to consider ultrasonic imaging of gastric contents for preoperative risk assessment of "full" stomach in clinical practice. Ultrasonography of the body of the stomach allows direct visualization of the gastric contents. However, the stomach is often difficult to identify, particularly when it is empty. Moreover, quantitative assessment of gastric volume is delicate, and no standardized method of ultrasonography of the body of the stomach for preoperative assessment of gastric contents was described. On the contrary, ultrasonography of the antral cross-sectional area, which was initially described for the assessment of gastric emptying as an alternative method to repeated measurements of the variations of antropyloric volume after ingestion of a test meal, is easy to perform and is highly reproducible through using the aorta and the left lobe of the liver as internal landmarks. Qualitative assessment of the gastric antrum allows easily diagnosis of a "full" stomach. The measurement of antral area may allow a more accurate estimate of the presence or absence of gastric contents at risk of lung injury in the event of regurgitation and aspiration (gastric volume >0.8 ml/kg and/or with solid particles), defining the "risk" stomach. The use of antral ultrasonography may help the anesthesiologist to assess the risk of pulmonary aspiration according to clinical history of the patient, in order to choose an appropriate strategy minimizing the occurrence of this complication.