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Newsletter October 2022: Cricoid pressure in rapid sequence induction: Is it time to release the pressure?

Kean Seng Cheah

“Are you pro or against cricoid pressure?” This was the exact question in a short debate among colleagues during our theatre tea break.

sept-4Sellick first demonstrated cricoid pressure in cadavers to prevent reflux of gastric content from reaching the pharynx in a small case series in 1960¹. He later reported applying this technique in 26 high-risk patients, of which he found 23 patients did not report regurgitation before, during or after intubation. Three of his patients had regurgitation upon release of cricoid pressure. He published his findings in The Lancet, which subsequently received recognition worldwide. It was rapidly included as “standard of care” for rapid sequence induction (RSI). This manoeuvre was even given its name after him – The Sellick manoeuvre.

Fast forward 6 decades since its introduction, the evidence-based recommendation to apply cricoid pressure to prevent gastric regurgitation and aspiration remained at level 4 (evidence based on case series) and Grade D recommendation (weak evidence and practice with caution). Many anaesthetists advocate the abandonment of cricoid pressure, but some are still holding on it, due to fear of aspiration in patient. The 2015 guidelines of management of unanticipated difficult intubation in adults from the Difficult Airway Society still recommend cricoid pressure as routine standard practice², but some professional associations are moving away from that in recent years. Clinical practice guidelines from the Scandanavian Society of Anaesthesia and Intensive Care in 2010 no longer recommend cricoid pressure as mandatory but can be used with individual judgement³. The European Resuscitation Council removed cricoid pressure as routine practice in RSI. If cricoid pressure is used it should be adjusted, relaxed or released if it impedes ventilation/intubation₄⁴. Germany was one of the first countries to design national guidelines on airway management in 2004. In 2015, the German society of Anaesthesia and Intensive Care revised its recommendation to omit cricoid pressure after weighing up the potential risks vs benefits⁵. However, none of the guidelines adopts a firm policy to remove cricoid pressure completely. In other words, do it at your own risk and judgement because the evidence is weak.

After all these years, no study has provided convincing evidence that cricoid pressure is effective in preventing aspiration⁶. Not only does the risk of aspiration not increase in absence of cricoid pressure, but aspiration still occurs despite being in cases where cricoid pressure being applied correctly⁷. It has well proven that cricoid pressure can worsen laryngoscopy view and makes ventilation difficult⁸. Inadvertent excessive force by airway assistant, especially a junior personnel, results in complete airway occlusion, increase difficulty for airway person to visualize the vocal cord. This relationship of cricoid pressure and laryngoscopy is complex with several reports showed worsening of laryngoscopy view with cricoid pressure even in patients with a good initial view⁸.

Why it makes sense historically but in the modern day?

Looking back in his publication, there was a good reason why Sellick designed this technique to avoid gastric reflux during intubation. From his original description, Sellick used cricoid pressure with manual ventilation before securing the airway because it was the “standard practice” in his time. It was not until 1964 both Wylie and Stevens proposed that ventilation should be delayed until tracheal intubation is completed. Sellick made a good initiative by modifying the technique of anaesthesia in his time but this practice based on initial small case series 60 years ago no longer fits well in 21st century. Many raised questions in his technique with concerns of more harm than good done to the patient. Sellick positioned his patients in Trendelenburg position to clearly demonstrate regurgitation if present, this obviously is not the standard practice in current day. The lack of information on method of anaesthesia and the force of cricoid pressure used by Sellick remained questionable. How closely can we relate the lower sphincter and intragastric pressure from cadaveric study to real patients remained unknown. After all, the dynamic process of sphincter tone and gastric pressure in real patient is hard to replicate in the non-responsive tissue of the cadaver. Many narrative reviews, correspondence, randomised control trials and systemic review have shown that cricoid pressure is not effective in preventing aspiration, so is it time to let go of your pressure?

Why cricoid pressure is not effective all the time?

Reports have shown that regurgitation can still occur despite cricoid pressure being applied correctly⁷. One of the reasons is because cricoid cartilage and oesophagus is not aligned directly in some people. Smith et al⁹. reported in his paper that one-half of the volunteer have their oesophagus displaced laterally in MRI/CT imaging in normal circumstances, so cricoid pressure further displaced the oesophagus in 90.5% of subjects, to the left in 69.4% and to the right in 21.1%. This lateral displacement of the oesophagus often results in ineffective cricoid pressure.

Many anaesthetists failed to generate correct cricoid pressure reliably. The statement “cricoid pressure should be applied at force of 10N when patient is awake and increase to 30N when asleep” is often easy enough to comprehend but difficult to perform correctly. In one simulation experience done by experienced operator⁹, out of 114 attempts of target force 30N cricoid pressure, only 15 (13%) was successful, and 35 (31%) fall in the range of 25-35N. This adds to 44% in total. It also means when cricoid pressure is applied, 56% of the time, we are not getting even close to an acceptable range of 25-35N. That is not surprising if the outcome is even more inconsistent when it comes to a real patient with variable neck anatomy. This shows how universally we are aware of how much force to apply for cricoid pressure but how inaccurate it can be in reality. “The art of firm pressure on cricoid” takes more than just the operator’s finger and more than a few seconds of education. It involves multiple education, training, simulation and repeat until we achieve satisfying consistency. Although the quality and accuracy of cricoid pressure improve following education and training, it is still almost impossible for human subjects to achieve pre-defined proficiency of cricoid pressure from one study¹⁰.

We need stronger evidence before we decide to continue.

For cricoid pressure to be effective and safe, it takes more than just achieving accurate pre-fixed tension. It depends on the patient factor and the person who is performing intubation. To reliably perform this study required many standardisation factors, to make the comparison between 2 groups of patients with or without cricoid pressure while ignoring the other factors is difficult to make a meaningful interpretation and conclusion. Many anaesthetists used force of 30N for cricoid pressure, but is it really safe to use 30N to everyone in general? Should we use higher pressure in a patient with obesity with a thick neck? Similarly, should we use lower pressure among low BMI and paediatric age groups? Should we use lesser force if the presence of nasogastric tube in patient, or patient with head-up position?

Looking at the current evidence, if cricoid pressure is not proven to be effective in preventing aspiration but likely results in more complications, then guidelines should be firm in its phrase, rather than leaving 2 minds. After all, we as clinicians always refer to respective guidelines for good clinical practice. Not only that, clinical guidelines often have medico-legal implications.

References

  1. SELLICK BA. Lancet. 1961 Aug 19;2(7199):404-6.  
  2. Frerk C, Mitchell VS, McNarry AF et al. Br J Anaesth. 2015 Dec;115(6):827-48. 
  3. Jensen AG, Callesen T, Hagemo JS et al. Acta Anaesthesiol Scand. 2010 Sep;54(8):922-50.  
  4. Soar J, Nolan JP, Böttiger BW. Resuscitation. 2015 Oct; 95:100-47. 
  5. http://www.awmf.org/uploads/tx_szleitlinien/001-028l_S1_Atemwegsmanagement_2015-04_01.pdf
  6. Birenbaum A, Hajage D, Roche S et al. JAMA Surg. 2019 Jan 1;154(1):96. 
  7. Fenton PM, Reynolds F. Int J Obstet Anesth. 2009 Apr;18(2):106-10. 
  8. Haslam, N., Parker, L. and Duggan, Anaesthesia, 60: 41-47.  
  9. Smith KJ, Ladak S, Choi PT et al. Can J Anaesth. 2002 May;49(5):503-7. 
  10. Johnson RL, Cannon EK, Mantilla CB et al. Br J Anaesth. 2013 Sep;111(3):338-46.  
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9 replies

Hans-Joachim Priebe
Dear Dr. Ramos, answers to the questions previously raised by Dr. Seng and myself a month ago would be appreciated. Thanks.
11 days ago
Marcelo Sperandio Ramos
Polemic points (no consensus), a pair of obsolete “sacred cows”: 1 - No ventilation rule and 2 – Cricoid pressure Both “sacred cows” (No ventilation and cricoid pressure) were stated about 60 years ago with a very weak or no evidence base and adopted for the lack of better choice by the anesthetic community. Nowadays they still survive not for their intrinsic value, but for tradition, fear of legal implication in breaking a rule (for more stupid the rules may be) and there is robust evidence against both “sacred cows”. The intended meaning for “sacred cow” in this text is: one that is often unreasonably immune from criticism or opposition. Sacred cow (idiom), something considered (perhaps unreasonably) immune to question or criticism. 1. Sacred cow # 1 – NO ventilation rule Rapid Sequence Induction (RSI) was de-scribed in 1970 following the description of cricoid pressure to prevent aspiration. This 1970 anesthesia (traditional) method describes a period of apnea with no positive pressure ventilation. Almost every element of the original technique has been challenged or adapted and updated nowadays. This may be because there is little good evidence published since the original description to show that traditional RSI effectively reduces aspiration or improves patient outcomes , besides that, at that time there were no pulse oximeter to show how dangerously low the saturations fell after the apnea period. It is now known that some patients can become hypoxic during the apnea phase between pre-oxygenation and tracheal intubation . The incidence of hypoxia during RSI can be very high . Because I will never be 100% sure that I can ventilate and/or intubate my patient, I refuse to give up the extremely useful “diagnostic maneuver” provided by face mask ventilation (and yes, I do agree that mask ventilation is carried out more easily and effectively with full relaxation). The management of the situation “cannot ventilate & cannot intubate” – (CICO) is different from the management of the situation “can ventilate & cannot intubate”; and the trial of face mask ventilation is the only way to know on which terrain I am standing on. It is not surprising that rapid sequence intubation is often accompanied with desaturation both in pre and intra hospital setting , . As soon as the patient is unconscious and apneic, the “diagnostic maneuver” of mask ventilation (and preferably an optimized one) will direct the course of action (if VL fails). By optimized mask ventilation, I mean good anesthetic depth, proper relaxation, the best possible mask seal with two hands if necessary, and a properly placed oropharyngeal airway. I would rather find that the patient is difficult/impossible to ventilate by mask immediately after induction, when the saturation is yet at the best possible level, than at the point in which saturation is already low and falling. If despite my best “educated guess” I made a judgment error and induced the wrong patient (the one I thought I could but, in reality cannot mask ventilate), I would resort to VL intubation attempt straight away and if it fails, to a second generation supraglottic device for rescue ventilation and / or conduit for flexible endoscopic intubation. Several studies , , , . , , including an “UpToDate” review confirm my practice of gentle (less than 20 cm of water) mask ventilation during the interval between induction and laryngoscopy and strengthened my belief that NO ventilation rule is an illogical relic of the past that should be banned. In my opinion, the benefits of this approach far outweigh the risks. Obviously, mask ventilation improves oxygenation compared to abiding to the pointless recommendation of waiting the effect of the paralytic agent for at least 60 precious seconds and doing nothing to support oxygenation (maybe THRIVE - high flow nasal oxygen - could be a game changer in this apneic period. In addition, if the laryngoscopy fails, mask ventilation is mandatory. Especially in patients with reduced tolerance for apnea (covid, pregnant, obese, etc.), performing a modified RSI with the provision of gentle manual ventilation (<20 cm H2O) could help to avoid hypoxia . There would be no source of polemic in this point (ventilation) if it weren’t for the concern of the potential of gastric insufflation generated by ventilation. Because ultrasound became ubiquitous and can detect gastric insufflation with greater accuracy than the epigastric stethoscope, a few studies appeared in the literature heralding that a considerable number of even elective and properly fastened patients could be at risk due to face mask ventilation. Whereas there is some controversy in literature about which level of pressure during mask ventilation (15? or 20?) leads to an acceptable (or not) increase in the risk of gastric insufflation due to mask ventilation ; there is no doubt that the lack of mask ventilation will lead to dangerous (and potentially fatal) hypoxia if intubation cannot be carried out in first attempt for whatsoever reason. Amplifying what I believe is a wrong rationale (because entrance of gas into the stomach in far to be equivalent of aspiration), there is a study defending no ventilation even routine patients ; while I defend the opposite line of though, the one that allows gentle ventilation even for rapid sequence induction. I listed this topic as a polemic one because there is robust literature defending the addition of gentle (restricted pressure) ventilation in the time lapse between the injection and the laryngoscopy, defying the “sacred cow # 1” of NO ventilation rule, along with its version on steroids (supported by gastric ultrasound studies). The newer (modern) perspective given by gastric ultrasound detection of gastric insufflation does not justify persisting to abide to an old fashioned (“sacred cow”) nonsense rule of no ventilation that denies two precious features: Oxygen to the patient and information for the anesthesiologist. This nonsense NO ventilation rule is made even more pointless if we consider the next “sacred cow”. Sacred cow #2 – Cricoid pressure – to do or not to do (Sellick maneuver) Application of cricoid pressure (CP) for patients undergoing rapid-sequence intubation is controversial. Multiple specialty societies have recommended that CP is not effective in preventing aspiration; rather it may turn laryngoscopy more challenging and impair bag-valve mask ventilation. The technique involves the application of pressure (force near 30 N) to the cricoid cartilage, thus occluding the esophagus which passes directly behind it (modern studies showed that it is not the anatomic reality). There are so many studies both in the PRO and in the CON sides that it is really amazing how there is no definitive answer about a maneuver that was described in the 60’s! I remember the 2014 SAM meeting where I heard as “the final conclusion” of a lecture about the theme: “Regardless of you do, or not (cricoid pressure) it is important that you have a good lawyer!” There is a vast literature about the theme, both in traditional journals and on internet pages. What I believe was the final nail in the coffin to universal recommendation of cricoid pressure was the IRIS study . This (IRIS) study is commented at internet sites which I strongly recommend reading , , , , . According to the authors conclusions of the IRIS study: “This large randomized clinical trial performed in patients undergoing anesthesia with RSI failed to demonstrate the noninferiority of the sham procedure in preventing pulmonary aspiration” Although this (IRIS) study failed to demonstrate non-inferiority of sham cricoid pressure to cricoid pressure the data does not show any hint that cricoid pressure is the better approach. In fact, there was a significant difference in terms of difficulty of intubation favoring no application of cricoid pressure and, the difficulty in view was relieved in most cases by removing cricoid pressure. There is good evidence that cricoid pressure (CP) impedes the gastric insufflation during ventilation . It is illogical that CP would be unidirectional in its effectiveness and would prevent gastric insufflation during positive-pressure ventilation while not preventing esophageal contents from reaching the pharynx if regurgitation occurs. Several studies showed that the cricoid cartilage is not on the esophagus and that there is lateral displacement, but such lateral displacement does not reduce the effectiveness of CP. Therefore, ventilation following drug administration may be less likely to provoke aspiration (if you are a “believer of the sacred cows” for the sake of tradition, you ought to choose which sacred cow you are going to follow, since “sacred cow #1” is contradicted by “sacred cow #2”). The UK is one of only a few countries with a high use of cricoid pressure. Other national and international guidelines including those by the European Resuscitation Council, Scandinavian Clinical Practice Guidelines, and German Airway Management Guidelines do not support its use. The use of cricoid pressure as an essential component of RSI is decreasing . When it is used it is widely recommended that it should be rapidly released in the event of a poor view at laryngoscopy. Navigating through the myriad of studies both PRO and CON the use of cricoid pressure, my conclusion is that the maneuver may be useful immediately following the near simultaneous injection of the hypnotic, opiate and paralytic agent and beginning of video laryngoscopy; just to be switched for a BURP maneuver (or any helping external laryngeal displacement according to the view on the screen), as actual intubation attempt begins.
20 days ago
Kean Seng
Thank you everyone for feedback. Thank you Dr Ramos for sharing your practice. In addition to question raised by Dr Priebe, can I ask if you use this technique for all emergency cases? or only selectively in elective, well fasted patient? Thanks!
1 month ago
PT Gan
Thanks for the interesting read :)
1 month ago
Hans-Joachim Priebe
Overall, I agree with the author’s opinion. Dr. Ramos’ comment triggers a couple of questions. Who is applying cricoid pressure (CP) while you are ventilating the patient? Is that person trained in ‘correctly’ applying CP (whatever ‘correctly’ means in this context …)? How much force is that person applying? How do you monitor that force? How do you know that the applied CP is effectively occluding the upper esophagus? Thank you for your clarification.
2 months ago
Theng keng ping
True indeed
2 months ago
gabriel gurm
True, indeed. GG
2 months ago
Marcelo A Ramos
I buse cricoid pressure during the interval between the injection of drugs and the attempt of laryngoscopy because I DO VENTILATE the patients in this brief period between injection and laryngoscopy. There are several studies (with the gastric US) that show that it works for avoiding gastric insulation. As soon as my hand touches the laryngoscope the cricoid pressure is replaced for a BURP maneuver, not over the cricoid cartilage, but thyroid cartilage, as needed. The person who performs these pressures does it as guided by the shared vision of the VL scene, to maximize the chance of first-attempt success.
2 months ago
Adrian Wong
I agree with the authors thoughts and final comments. In particular, this is something so entrenched that the only way to move forward is to have Guidelines that support not using it. If it remains, colleagues may continue to use it for fear of litigation should patients come to harm when not used.
2 months ago

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