November 2015, the Difficult Airway Society have published their updated guidelines for management of difficult intubation in adults. Again DAS provide an excellent overview on unanticipated difficult intubations in adults... worth reading for anyone involved in critical care!
When reading this article I couldn't help myself putting a special focus on the controversial issue of cricoid pressure (CP) for rapid sequence induction (RSI). This topic has become a major matter of debate as scientific evidence of its effect on preventing aspiration of gastric content is basically lacking. There is quite some evidence available showing that cricoid pressure might actually impair intubation or potentially harm the patient. More background information and links on this topic you can find here. While some guidelines have actually 'softened' or abandoned the recommendation for the use of CP, most of them have not... and continue to recommend CP. It was therefore of great interest to see what the panel of the DAS would come up with!
For anaesthetists working in Britain and Ireland the DAS guidelines are of special interest as they represent some sort of legal binding on how to proceed at their daily work. We took a closer look at the new guidelines... and got surprised:
"This (CP) is a standard component of rapid sequence induction in the UK". Ok... so no change there! This statement is pretty clear and leaves no space for interpretation - sounds imperative. A little less clear are the following text passages on why CP remains a standard component.
"It is often overlooked that cricoid pressure has been shown to prevent gastric distension during mask ventilation and was originally described for this purpose"... Well, actually cricoid pressure was originally described by Brian Arthur Sellick in the Lancet in 1961 as a preliminary report of an un-controlled case study and the purpose of cricoid pressure was to control regurgitation of gastric content during induction of anaesthesia.
CP and Gastric Insufflation
The reference cited in the context of gastric insufflation and cricoid pressure is an article by Salem and Sellik form Anaesthesia and Analgesia in 1974 (read the original article here). They write: one aim of CP is the prevention of aspiration. The other one is the prevention of gastric insufflation during mask ventilation. The presented evidence in that regard though is not really convincing:
a) A historical letter of Dr. William Cullen... dated back in 1774!
b) The other reference is an article by Salem himself on the 'efficacy of cricoid pressure in preventing gastric inflation during bag-mask ventilation in paediatric patients, but not adults!
Another article cited by the DAS (Obstetric Anaesthetists' Association/Difficult Airway Society difficult and failed tracheal intubation guidelines – the way forward for the obstetric airway Br. J. Anaesth. (2015) 115 (6): 815-818) actually recommends gentle ventilation with low insufflation pressure during RSI which should not overcome correctly applied cricoid pressure. This suggests that CP makes gentle bag-mask ventilation safe.
Indeed, Lawes et al. already showed in 1987 that when bag-mask ventilating, it was not possible to cause gas to enter the stomach in any patient with a patent airway when cricoid pressure was applied. BUT he also stated that: In the absence of cricoid pressure the lungs of all the patients could be ventilated “gently” satisfactorily by hand without gas entering the stomach.
The Bottom Line
Going through these overall brilliant guidelines by the DAS I still haven't been convinced about the usefulness of cricoid pressure and resume (once again):
- Cricoid pressure for rapid sequence induction remains a non-evidence-based manoeuvre and should be seriously questioned!
And by the way, I feel the DAS actually knows that. You have to acknowledge what Hagberg writes in the BJA editorial:
..."the application of CP during rapid sequence induction remains a matter of debate; some believe in its effectiveness in preventing pulmonary aspiration, whereas others believe it should be abandoned because of the paucity of scientific evidence of benefit and possible complications."
..."The literature does demonstrate that the use of CP is likely to make airway interventions, such as mask ventilation, SGA insertion, direct laryngoscopy, and intubation more difficult."
..."As a result of the lack of sufficient scientific evidence that CP reduces regurgitation, in addition to evidence that it may interfere with airway management..."
Difficult Airway Society DAS 2015 guidelines for management of unanticipated difficult intubation in adults, Br. J. Anaesth. 2015 OPEN ACCESS
BIJC post on Cricoid Pressure 04/2014
Hagberg et al. DAS 2015 Guidelines - Editorial, Br. J. Anaesth. 2015, 1-3 OPEN ACCESS
Lawes et al. Inflation Pressure, Gastric Insufflation and Rapid Sequence Induction, Br. J. Anaesth. 1987
Microbiologically confirmed ventilator-associated pneumonia (VAP) or ventilator-associated conditions (VAC, e.g. worsening oxygenation) in intubated patients remains a major concern in ICU's. VAP is defined as a hospital-acquired pneumonia which develops within 48-72 hours after endotracheal intubation.
To prevent this complication ICU's uniformly have adapted the VAP-bundle, a bunch of measures aiming to prevent ventilator-associated pneumonia. Unfortunately the evidence of the VAP-bundle is not as robust as one might think it is. Here's the evidence of some elements of the VAP bundle:
- Elevation of the head to bed 45° (low evidence)
- Daily sedation interruptions (the impact on reducing VAP has not been shown so far)
- Daily oral chlorhexidine rinses (low evidence)
... it's most likely the combination of measures that is of benefit to the patient... hopefully! But hold on, there is another intervention that finally brings quite some evidence with it!
Active suctioning of the subglottic area, where nasal-oral secretions gather and create a rich culture medium for all sorts of micro-organisms, also aims to reduce the incidence of VAP. In contrast to the classical VAP-bundle the evidence here is strongly in favour for these devices!
In 2005 four registrars in cardiothoracic surgery looked into this topic and summarised their efforts online on Best Evidence Topics, best bets.org. In this blog they review 13 relevant articles on the use of subglottic suctioning and conclude: subglottic suction significantly reduces the incidence of VAP in high risk patients - which means a NNT of 8 if ventilated for more than 3 days. They also mention that this measure is cost effective, despite the more expensive tubes.
In the same year Dezfulian et al. presented a systematic meta-analysis of randomized trials in the American Journal of Medicine. They ended up with 5 studies including 869 patients. They also came to the conclusion that subglottic secretion drainage is effective in preventing VAP in patients expected to be ventilated for more than 72 hours.
In 2011 Hallais et al. looked into the issue of cost-effectiveness with a cost-benefit analysis. Even when assuming the most pessimistic scenario of VAP incidence and costs the replacement of conventional ventilation with continuous subglottic suctioning would still be cost-effective.
In 2011 Muscedere et al. published an 'official' review article in Critical Care Medicine and also ended up with 13 randomised clinical trial, most of them the same 'BestBETs' had already identified 6 years before. It is therefore not surprising to see that they also found a highly significant reduction in VAP. They were also able to demonstrate a reduction in ICU length of stay and duration of mechanical ventilation, although the strength of this association was weakened by heterogeneity of study results.
We finally would like to mention the latest randomised controlled trial on this topic which was published in Critical Care Medicine this January 2015. Damas et al. randomly assigned 352 patients to either receive subglottic suctioning or not. Again sublottic suctioning significantly reduced VAP prevalence and therefore also antibiotic use.
At least we have identified one area in critical care where an impressive pile of evidence supporting the use of subglottic suctioning in long-term intubated patients is present... and even better: cost-effective analyses also come out in great favour for this measure!
Take-home message: Subglottic suctioning does prevent VAP in patients likely to be ventilated more than (48-) 72 hours and should be used in these situations.
Review BestBETs 2005
Dezfulian C et al. Am J Med. 2005 Jan;118(1):11-8
Hallais C. et al. Infect Control Hosp Epidemiol. 2011 Feb;32(2):131-5
Muscedere J et al. Crit Care Med. 2011 Vol. 39, No. 8
Damas P et al. Crit Care Med. 2015 Jan;43(1):22-30
In the most recent edition of 'Continuing Education in Anaesthesia, Critical Care and Pain' there is a very good overview article on rapid sequence induction (RSI) and its place in modern anaesthesia. Wallace and McGuire also critically look at cricoid pressure (CP) as a part of classical RSI.
In their publication they state that "there have been no prospective randomized clinical studies performed to prove the clinical hypothesis and the level of evidence to support the use of cricoid pressure is poor (Level 5)". Level 5 corresponds to 'Expert Opinion' (see table below). They also mention that aspiration has occured despite CP, that CP is often poorly performed, that it may hinder bag-valve mask ventilation as well as LMA insertion and that is may worsen laryngoscopy. It's mentioned that "Critically, it has also been shown to potentially obstruct the upper airway and reduce time to desaturation".
'This is nothing new' you might say. Why am I mentioning this? Well, the remarkable thing about this article is the fact that it was published in a Journal that is a joint venture of the British Journal of Anaesthesia BJA and The Royal College of Anaesthetists in collaboration with the Intensive Care Society and Pain Society. Considering the fact that The NAP4 guidelines continue to support its use as part of an RSI and as such, it is still considered a standard of care in the UK and therefore also Ireland, this publication might indicate some change in mind... or not?
The authors summarize: Application of cricoid pressure is advisable — unless it obscures the view at laryngoscopy or interferes with manual ventilation or supraglottic airway device placement.
I personally still would want to know what exactly makes a 'Level 5' medical intervention 'advisable' especially in regards of all the possible problems and complications associated with it.
Wallace et al., Continuing Education in Anaesthesia, Critical Care & Pain, Volume 14(3), June 2014, p 130–135
Read our previous BIJC post: Cricoid Pressure for RSI in the ICU: Time to Let Go? (Updated)
Most of us being trained as anaesthetists in the last couple of years have learnt to perform a rapid sequence induction (RSI) including the application of cricoid pressure (aka the Sellick manoeuvre) in order to prevent aspiration of gastric content.
Over the last couple of years though this manoeuvre has been seriously questioned as scientific evidence is lacking and there are concerns that cricoid pressure might actually be potentially harmful.
A lot has been written on this topic so far and some great reviews can be found easily on the internet thanks to the concept of Open Free Access Meducation (FOAMed, see below). Still I would like to add some thoughts on to this discussion and maybe mention one or two more interesting facts.
Cricoid pressure was actually first described by Sellick in the Lancet in 1961 as a preliminary report and basically represented an un-controlled case study in which no or only insufficient information on the studies patient population was provided. There was no standardisation of the force for cricoid pressure as of the medications used for induction. There was also no information on the quality of laryngoscopy and intubation. Steinmann and Priebe (abstract in english) have exactly analysed this publication and found some relevant methodological shortcomings. It is therefore remarkable that this publication led to an anaesthetic dogma practised all over the world.
As mentioned in the European Resuscitation Council Guidelines of 2005, studies in anaesthetised patients show that cricoid pressure impairs ventilation in many patients, increases peak inspiratory pressures and causes complete obstruction in up to 50% of patients depending on the amount of pressure applied (Petito, Lawes, Hartsilver, Allman, Hocking, Mac, Ho, Shorten).
The incidence of a difficult intubation is significantly higher in preclinical emergency situations than in an elective theatre environment (Timmermann A et al. Resuscitation 2007;70(2):179-185). It is therefore possible, that cricoid pressure itself actually is one of the reasons why unexperienced emergency physicians experience additional difficulties when intubating 'in the field'.
One concern often mentioned is the fear that non-adherence to current guidelines by not applying cricoid pressure might have adverse legal implications. But what do current guidelines actually say? Priebe et al. partially looked at this in 2012. Several guidelines indeed still recommend cricoid pressure, sometimes even with less force in the awake patient. But some guidelines have started to implement current evidence.
The 2010 Clnical Practice Guidelines on General Anaesthesia for Emergency Situations by the Scandinavian Society of Anaesthesiology and Intensive Care Medicine state following:
(i) The use of CP cannot be recommended on the basis of scientific evidence (recommendation E, supported by non-randomized, historic controls, case series, uncontrolled studies and expert opinion)
(ii) The use of CP is therefore not considered mandatory but can be used on individual judgement (recommendation E).
(iii) If facemask ventilation becomes necessary, CP can be recommended because it may reduce the risk of causing inflation of the stomach (recommendation D, supported by non-randomized, contemporaneous controls)
The 2005 European Resuscitation Council Guidelines (page 1322, pdf here) puts it this way:
- The routine use of cricoid pressure in cardiac arrest is not recommended.
- Studies in anaesthetised patients show that cricoid pressure impairs ventilation in many patients, increases peak inspiratory pressures and causes complete obstruction in up to 50% of patients depending on the amount of cricoid pressure (in the range of recommended effective pressure) that is applied.
Still though it has to be mentioned that the Difficult Airwas Society (DAS) continues to recommend cricoid pressure for RSI on it's website. The current recommendation though seems to date back to 2004 and the question is mentioned on their website whether any pressure should be applied before loss of consciousness.
Also the Association of Anaesthetists in Great Britain and Ireland recommends cricoid pressure in their AAGBI Safety Guidelines of 2009 on pre-hospital anaesthesia. It is also mentioned that 'badly applied cricoid pressure is a cause of a poor view at laryngoscopy. It may need to be adjusted or released to facilitate intubation or ventilation'.
While the discussion on this issue in adults will continue the dogma of cricoid pressure might soon fall in paediatric patients as Neuhaus D et al. published a Swiss trial in 2013 where they could show that a controlled rapid sequence induction without cricoid pressure is actually safe.
Further research is on its way: Trethrewy E et al. Trials. 2012 Feb 16;13:17. Until then it seems as if we are faced with guidelines mostly still in favour for cricoid pressure and evidence based medicine, which is rather discouraging us of further performing this procedure. It is good practice to constantly question current guidelines and further improve them for the patient's sake. Indeed you have to ask yourself on how far you want to stick to current guidelines for legal reasons or if you change your practice according to emerging evidence.
Some of the hospitals I worked at in Switzerland have stopped performing cricoid pressure for RSI some years ago and haven't encountered any worsening in their patient outcomes. Taking into account that most RSI in the ICU resemble emergency intubations out of hospital rather than the controlled environment of a theatre I feel there are good reasons to start re-evaluating and possibly change current guidelines.
Other very interesting resources of information can be found here (FOAMed):
- lifeinthefastlane.com on cricoid pressure
- resus.me on cricoid pressure
- Update 02/05/14: Minh Le Cong published a statement of the NAP 4 investigators on his blog website: statement from NAP 4 (on prehospitalmed.com)
... The discussion goes on!
Many intensive care units try to avoid extubations at nighttime due to the fear of potentially fatal complications and possibly higher reintubation rates. However, it might actually be favourable to extubate patients as soon as possible, as this might have a positive impact on ventilation related complications and patient's length of stay. Interestingly nobody has ever looked at this special topic so far.
Tischenkel BR et al. have now looked at this topic in a retrospective cohort study of two hospitals in the state of New York. In this paper, published in the Journal of Intensive Care Medicine this month, they looked at a total of 2240 patients which were extubated in intensive care units over the period of almost 2 years. As a result they could show that nighttime extubations did not have a higher likelihood of reintubation, length of stay or mortality compared to those during the day. They conclude that patients should be extubated as soon as they meet parameters in order to potentially decrease complications of mechanical ventilation. These data, they say, do not support delaying extubations until daytime.
I fully agree... as long as there is somebody in the unit able to deal with potentially deleterious complications!
Tischenkel BR et al. J Intensive Care Med April 24, 2014
It has been almost for 40 years that the positive effect of prone positioning in ARDS patients was recognised. But even up to 2012 no benefit on mortality could be found in several studies and also the duration of prone positioning was not found to make any difference.
In June 2013 Guerin et al. published the PROSEVA trial which indeed showed some amazing results. It is the 5th biggest trial of it's kind and finally was able to actually now show a dramatic reduction in mortality: the 28 day mortality was 32.8% in the supine group (229 patients), compared to only 16% in the prone group (237 patients). This benefit in outcome persisted also after 90 days... a miracle?
Most probably these results reflect the very strict adherence to the guidelines of ARDSnet in regards of paralysation and use of very low tidal volumes. One thing that has to be mentioned is the high number of patients with ARDS which have excluded from the trial for several reasons.
So should we now follow this study and prone more aggressively?
One answer might be the just recently published meta-analysis by Lee at al. in Critical Care Medicine. This paper looked at a total of 11 randomised controlled trials and therefore takes all recent publications into account. The authors come to the conclusion that prone positioning indeed does reduce mortality significantly and were marked in the subgroup where the duration of prone positioning was more than 10 hours. This is the first time somebody actually comments on the length of prone positioning in terms of benefit for the patient.
As always though there are also adverse effects of this therapy as prone positioning was significantly associated with pressure sores and maybe most importantly major airway problems.
Overall, the concept of prone positioning in severe ARDS seems to be well established and should be implemented in the clinical procedures of every intensive care unit. This is particularly true for regions where quick access to extra corporal CO2 removal or oxygenation devices is difficult.
Guerin C et al. N Engl J Med. 2013 Jun 6;368(23):2159-68.
Lee JM et al. Crit Care Med. 2014 May;42(5):1252-62.
Ferguson et al. Intensive Care Med. 2012 Oct;38(10):1573-82.
A very nice and quick overview on treatment options for ARDS was presented by Ferguson et al. in Intensive Care Medicine 2012:
In this recently published Brief Report in the Journal of Academic Emergency Medicine Patanwala et al. looked retrospectively at first pass intubation success by comparing Ketamine to Etomidate. The final cohort included 2098 patients and even after adjusting for potential confounders there was no difference in success rates between the two drugs. In regards of recent discussions on the safety of Etomidate (e.g. adrenal suppression) this study seems to be another puzzle piece favoring other induction agents than Etomidate.
Looking at recent publications on paralyzing agents and personal experience I feel that Ketamine and Rocuronium is a favorable combination for rapid sequence inductions in the ICU... what do you think?
Patanwala A et al.Academic Emergency. 2014 Feb
Curley J et al. Critical Care. 2011,15:190
Marsch SC et al.Crit Care. 2011 Aug 16;15(4):R199