Cricoid pressure impedes insertion of, and ventilation through, the ProSeal laryngeal mask airway in anesthetized, paralyzed patients

Left paratracheal pressure versus cricoid pressure for successful laryngeal mask airway insertion in adult patients: a randomized, non-inferiority trial

BACKGROUND

Cricoid pressure (CP) is used to prevent pulmonary aspiration of regurgitated gastric contents and gastric insufflation during positive-pressure ventilation. However, CP impedes the successful insertion of laryngeal mask airway (LMA). Left paratracheal pressure (LPP), a manoeuvre of applying backward digital force at the lower left paratracheal level, was recently introduced as an alternative to CP. We assessed whether LPP is non-inferior to CP in successful LMA insertion on the first attempt in adult patients undergoing general anaesthesia.

METHODS

In this non-inferiority randomized controlled trial, 108 patients undergoing general anaesthesia were randomly allocated to receive either LPP or CP during LMA insertion. The primary outcome was the success rate of LMA insertion on the first attempt. The margin of non-inferiority was defined as 15%.

RESULTS

The success rate of LMA insertion on the first attempt was 68.5% (37/54) in the LPP group and 51.9% (28/54) in the CP group (P=0.077) with between-group difference of 16.7% (two-sided 95% CI, -1.9% to 35.2%). Time for successful device insertion was comparable in the two groups (P=0.355), whereas LMA insertion was easier in the LPP group than in the CP group (P=0.001). There was no significant difference between the two groups for change in antral cross-sectional area measured before and after mask ventilation (P=0.081). No serious complication was evident in any group.

CONCLUSIONS

This randomized clinical trial demonstrated the non-inferiority of LPP over CP in the success rate of LMA insertion on the first attempt in adult patients undergoing general anaesthesia.

Canadian Airway Focus Group updated consensus-based recommendations for management of the difficult airway: part 1. Difficult airway management encountered in an unconscious patient

PURPOSE

Since the last Canadian Airway Focus Group (CAFG) guidelines were published in 2013, the literature on airway management has expanded substantially. The CAFG therefore re-convened to examine this literature and update practice recommendations. This first of two articles addresses difficulty encountered with airway management in an unconscious patient.

SOURCE

Canadian Airway Focus Group members, including anesthesia, emergency medicine, and critical care physicians, were assigned topics to search. Searches were run in the Medline, EMBASE, Cochrane Central Register of Controlled Trials, and CINAHL databases. Results were presented to the group and discussed during video conferences every two weeks from April 2018 to July 2020. These CAFG recommendations are based on the best available published evidence. Where high-quality evidence was lacking, statements are based on group consensus.

FINDINGS AND KEY RECOMMENDATIONS

Most studies comparing video laryngoscopy (VL) with direct laryngoscopy indicate a higher first attempt and overall success rate with VL, and lower complication rates. Thus, resources allowing, the CAFG now recommends use of VL with appropriately selected blade type to facilitate all tracheal intubations. If a first attempt at tracheal intubation or supraglottic airway (SGA) placement is unsuccessful, further attempts can be made as long as patient ventilation and oxygenation is maintained. Nevertheless, total attempts should be limited (to three or fewer) before declaring failure and pausing to consider "exit strategy" options. For failed intubation, exit strategy options in the still-oxygenated patient include awakening (if feasible), temporizing with an SGA, a single further attempt at tracheal intubation using a different technique, or front-of-neck airway access (FONA). Failure of tracheal intubation, face-mask ventilation, and SGA ventilation together with current or imminent hypoxemia defines a "cannot ventilate, cannot oxygenate" emergency. Neuromuscular blockade should be confirmed or established, and a single final attempt at face-mask ventilation, SGA placement, or tracheal intubation with hyper-angulated blade VL can be made, if it had not already been attempted. If ventilation remains impossible, emergency FONA should occur without delay using a scalpel-bougie-tube technique (in the adult patient). The CAFG recommends all institutions designate an individual as "airway lead" to help institute difficult airway protocols, ensure adequate training and equipment, and help with airway-related quality reviews.

Clinical Evaluation of the Cricoid Pressure Effect on Bag Mask Ventilation, ProSeal Laryngeal Mask Airway Placement and Ventilation

Objective

Supraglottic airway devices can be life-saving in the 'cannot intubate, cannot oxygenate' situation. The cricoid pressure (CP) is considered critical in the prevention of aspiration. The aim of this self-controlled study was to evaluate the effect of CP on the bag mask ventilation (BMV), and the placement of and the ventilation through, the ProSeal laryngeal mask airway (LMA).

Methods

In 60 adult patients undergoing elective surgery, after induction of anaesthesia, the effect of bimanual CP (≈30N) on BMV, ventilation through the ProSeal LMA, its anatomic position and airway seal pressures were evaluated. CP was released, the ProSeal LMA was reseated (appropriate position), the above assessments were repeated, and the effect of CP on the tidal volume (TV) and peak inspiratory pressure (PIP) was noted.

Results

Out of 60 patients, the bag mask ventilation with CP was adequate in 25 (41.7%) patients compared to 59 (98.3%) patients without CP; p<0.001. The ventilation via the ProSeal LMA with CP was excellent, adequate and impossible in 0.0% (0), 49.2% (29) and 50.8% (30) patients, respectively, compared to 93.3% (56), 6.7% (4), 0% (0) patients, respectively, without CP; p<0.001. Releasing CP and advancing the ProSeal LMA to its appropriate position significantly improved the ventilation and anatomic position scores; both p<0.001. Airway seal pressures improved significantly without CP compared to with CP; p<0.001). With the ProSeal LMA in a proper position, the CP application resulted in a significant decrease in the mean expired TV (489.14±91.62 vs. 355.08±104.42 mL) with an increase in PIP (16.72±5.01 vs. 30.71±6.74 cmH2O); both p<0.001.

Conclusion

The application of bimanual CP (≈30N) interferes with the bag mask ventilation and prevents both the correct placement and ventilation via the ProSeal LMA in adult patients.

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.

Effect of Cricoid Pressure on the Insertion Efficacy of Six Supraglottic Devices: A Crossover Randomized Simulation Trial

BACKGROUND

No study has ever compared the efficacy of various types of supraglottic devices (SGDs) for securing the airway under cricoid pressure.

OBJECTIVE

This study aimed to evaluate the efficacy of six SGDs, LMA-ProSeal (ProSeal), LMA-Classic (Classic), Laryngeal Tube (LT), LMA-Supreme (Supreme), air-Q (air-Q), and i-gel (i-gel), in airway management under cricoid pressure using a manikin.

METHODS

Fifteen novice doctors and 16 experienced doctors used the six SGDs under cricoid or sham pressure on an adult manikin. Insertion time, successful ventilation rate, and subjective insertion difficulty on a visual analogue scale (VAS) were measured.

RESULTS

Both novice and experienced doctors had a significantly lower ventilation success rate under cricoid pressure than under sham pressure when using the ProSeal, Classic, and LT, but not when using the other three SGDs. Novice doctors required a significantly longer insertion time under cricoid pressure than under sham pressure with all SGDs. Experienced doctors required a significantly longer insertion time under cricoid pressure than with sham pressure when using the ProSeal, Classic, and LT, but not when using the other three SGDs. Subjective insertion difficulty on VAS was significantly higher under cricoid pressure than under sham pressure with all six SGDs.

CONCLUSION

Ventilation success rate under cricoid pressure was significantly lower than under sham pressure when using the ProSeal, Classic, and LT, but not when using the other three SGDs in both novice and experienced doctors.

All India Difficult Airway Association 2016 guidelines for the management of unanticipated difficult tracheal intubation in adults

The All India Difficult Airway Association (AIDAA) guidelines for management of the unanticipated difficult airway in adults provide a structured, stepwise approach to manage unanticipated difficulty during tracheal intubation in adults. They have been developed based on the available evidence; wherever robust evidence was lacking, or to suit the needs and situation in India, recommendations were arrived at by consensus opinion of airway experts, incorporating the responses to a questionnaire sent to members of the AIDAA and the Indian Society of Anaesthesiologists. We recommend optimum pre-oxygenation and nasal insufflation of 15 L/min oxygen during apnoea in all patients, and calling for help if the initial attempt at intubation is unsuccessful. Transnasal humidified rapid insufflations of oxygen at 70 L/min (transnasal humidified rapid insufflation ventilatory exchange) should be used when available. We recommend no more than three attempts at tracheal intubation and two attempts at supraglottic airway device (SAD) insertion if intubation fails, provided oxygen saturation remains ≥ 95%. Intubation should be confirmed by capnography. Blind tracheal intubation through the SAD is not recommended. If SAD insertion fails, one final attempt at mask ventilation should be tried after ensuring neuromuscular blockade using the optimal technique for mask ventilation. Failure to intubate the trachea as well as an inability to ventilate the lungs by face mask and SAD constitutes 'complete ventilation failure', and emergency cricothyroidotomy should be performed. Patient counselling, documentation and standard reporting of the airway difficulty using a 'difficult airway alert form' must be done. In addition, the AIDAA provides suggestions for the contents of a difficult airway cart.

Assessment before airway management

It is wise to plan and prepare for the unexpected difficult airway. Although it is essential to take a history and examine every patient prior to airway management, preoperative anticipation of a difficult airway occurs in only 50% of patients subsequently found to have a difficult airway. Bedside screening tests lack accuracy. The modified Mallampati test and the measurement of thyromental distance are unreliable for prediction of difficult tracheal intubation. Knowledge of risk factors for various airway management techniques may help when devising an airway management plan.

Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults

These guidelines provide a strategy to manage unanticipated difficulty with tracheal intubation. They are founded on published evidence. Where evidence is lacking, they have been directed by feedback from members of the Difficult Airway Society and based on expert opinion. These guidelines have been informed by advances in the understanding of crisis management; they emphasize the recognition and declaration of difficulty during airway management. A simplified, single algorithm now covers unanticipated difficulties in both routine intubation and rapid sequence induction. Planning for failed intubation should form part of the pre-induction briefing, particularly for urgent surgery. Emphasis is placed on assessment, preparation, positioning, preoxygenation, maintenance of oxygenation, and minimizing trauma from airway interventions. It is recommended that the number of airway interventions are limited, and blind techniques using a bougie or through supraglottic airway devices have been superseded by video- or fibre-optically guided intubation. If tracheal intubation fails, supraglottic airway devices are recommended to provide a route for oxygenation while reviewing how to proceed. Second-generation devices have advantages and are recommended. When both tracheal intubation and supraglottic airway device insertion have failed, waking the patient is the default option. If at this stage, face-mask oxygenation is impossible in the presence of muscle relaxation, cricothyroidotomy should follow immediately. Scalpel cricothyroidotomy is recommended as the preferred rescue technique and should be practised by all anaesthetists. The plans outlined are designed to be simple and easy to follow. They should be regularly rehearsed and made familiar to the whole theatre team.

Cardiac Arrest Resuscitation

Cardiac arrest is a dynamic disease that tests the multitasking and leadership abilities of emergency physicians. Providers must simultaneously manage the logistics of resuscitation while searching for the cause of cardiac arrest. The astute clinician will also realize that he or she is orchestrating only one portion of a larger series of events, each of which directly affects patient outcomes. Resuscitation science is rapidly evolving, and emergency providers must be familiar with the latest evidence and controversies surrounding resuscitative techniques. This article reviews evidence, discusses controversies, and offers strategies to provide quality cardiac arrest resuscitation.

Effect of cricoid pressure on placement of the I-gel™ : a randomised study

We studied 40 adult patients to see if cricoid pressure affected placement of the I-gel(™). In a randomised crossover design, the i-gel was placed with and without cricoid pressure, and we compared the success rate of adequate ventilation through the i-gel, time to placement and the rate of optimal position of the device between the two circumstances. Cricoid pressure significantly decreased the success rate of adequate ventilation through the i-gel (40 vs 34 patients) (p = 0.041, 95% CI for difference 4-26%), and significantly decreased the rate of the optimal position (39 vs 17 patients) (p < 0.001). The time to achieve adequate ventilation was significantly longer (p < 0.001) with cricoid pressure than without (median difference 8 s; 95% CI for median difference 3-12 s). Cricoid pressure significantly decreases the success rate of ventilation through the i-gel, but the success rate of ventilation through the i-gel is reasonably high.

The difficult airway with recommendations for management--part 2--the anticipated difficult airway

BACKGROUND

Appropriate planning is crucial to avoid morbidity and mortality when difficulty is anticipated with airway management. Many guidelines developed by national societies have focused on management of difficulty encountered in the unconscious patient; however, little guidance appears in the literature on how best to approach the patient with an anticipated difficult airway.

METHODS

To review this and other subjects, the Canadian Airway Focus Group (CAFG) was re-formed. With representation from anesthesiology, emergency medicine, and critical care, CAFG members were assigned topics for review. As literature reviews were completed, results were presented and discussed during teleconferences and two face-to-face meetings. When appropriate, evidence- or consensus-based recommendations were made, and levels of evidence were assigned.

PRINCIPAL FINDINGS

Previously published predictors of difficult direct laryngoscopy are widely known. More recent studies report predictors of difficult face mask ventilation, video laryngoscopy, use of a supraglottic device, and cricothyrotomy. All are important facets of a complete airway evaluation and must be considered when difficulty is anticipated with airway management. Many studies now document the increasing patient morbidity that occurs with multiple attempts at tracheal intubation. Therefore, when difficulty is anticipated, tracheal intubation after induction of general anesthesia should be considered only when success with the chosen device(s) can be predicted in a maximum of three attempts. Concomitant predicted difficulty using oxygenation by face mask or supraglottic device ventilation as a fallback makes an awake approach advisable. Contextual issues, such as patient cooperation, availability of additional skilled help, and the clinician's experience, must also be considered in deciding the appropriate strategy.

CONCLUSIONS

With an appropriate airway evaluation and consideration of relevant contextual issues, a rational decision can be made on whether an awake approach to tracheal intubation will maximize patient safety or if airway management can safely proceed after induction of general anesthesia. With predicted difficulty, close attention should be paid to details of implementing the chosen approach. This should include having a plan in case of the failure of tracheal intubation or patient oxygenation.

The effects of head flexion on airway seal, quality of ventilation and orogastric tube placement using the ProSeal laryngeal mask airway

This prospective self-controlled study was designed to evaluate the influences of head flexion on airway seal, quality of ventilation, and orogastric tube placement through the ProSeal laryngeal mask airway (ProSeal LMA) in 80 anaesthetised, paralysed adult patients. After the ProSeal LMA was inserted and the cuff pressure was set at 5.9 kPa, ventilation quality, airway seal pressure, fibreoptic positions of the cuff and the drainage tube, orogastric tube placement and efficacy of intermittent positive pressure ventilation (IPPV) were assessed in two randomly selected positions: neutral and flexed position. When compared to the neutral head position, the head flexed significantly improved the airway seal pressure and the quality of ventilation of the ProSeal LMA (p < 0.05). Fibreoptic scores of the cuff position did not correlate with either the ability to obtain excellent or adequate ventilation through the ProSeal LMA or the ability to generate an airway seal pressure of >or= 2 kPa. Orogastric tube placement via the drainage tube was successful on the first attempt in all patients in the neutral position compared with seven failures following three attempts in the flexed position (p < 0.05). There were no significant differences between the two head positions in the volume of air required to obtain an intracuff pressure of 5.9 kPa, fibreoptic score of the drainage tube position, and expiratory tidal volume and peak inspiratory pressure during IPPV (p > 0.05). In conclusion, head flexion improves airway seal and ventilation quality of the ProSeal LMA. However, placement of an orogastric tube via the drainage tube is impaired in the flexed position compared to the neutral position. Fibreoptic scoring of the ProSeal cuff position is not an accurate test to assess the airway seal and ventilation function.