Sellick

Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia

Sellick BA. The Lancet 1961, Volume 278, Issue 7199, Pages 404-406

Clinical Question

  • Does the application of cricoid pressure during induction of anaesthesia control the regurgitation and  pulmonary aspiration of gastric or oesophageal contents?

Design

  • Case series of 26 patients

Setting

  • Single centre (Middlesex Hospital, London)

Population

  • Inclusion: Patients at ‘high risk’ of regurgitation of oesophageal or stomach contents
    • 18 laparotomy for intestinal obstruction
    • 3 gastrectomy for pyloric stenosis
    • 2 oesophagoscopy for achalasia of the cardia
    • 2 forceps delivery
    • 1 resection for oesophageal cancer

Intervention

  • Application of cricoid pressures
    • exerted by an assistant (nurse or midwife accompanying patient ‘can be shown in a few seconds how to do it’
    • before induction, cricoid is palpated and lightly held between the thumb and second finger. Pressure is exerted on the cricoid cartilage mainly by the index finger as anaesthesia begins
    • as soon as consciousness is lost, firm pressure is applied without obstruction of the patient’s airway
    • cricoid pressure is maintained until intubation and inflation of the cuff of the endotracheal tube is completed
  • In all cases:
    • Ryle’s or oesophageal tubes were fully aspirated and then removed before induction of anaesthesia. The rationale was that this would otherwise interfere with the effectiveness of cricoid pressure
    • patients were positioned in a slight head-down tilt
  • Other interventions:
    • pre-oxygenation was advised
    • an intravenous barbituate and muscle relaxant was used. However, if the patient was ‘seriously ill’ inhalational induction was considered
  • A short acting muscle relaxant was noted to provide faster intubating conditions

Control

  • No control group

Outcome

  • Primary outcome: regurgitation of oesophageal or gastric content visualised into the pharynx
    • 23 patients – cricoid pressure maintained until endotracheal cuff inflated
      • 0 witnessed regurgitation
    • 3 patients – cricoid pressure released after induction of anaesthesia and before intubation
      • 3 out of 3 had regurgitation
  • Secondary outcome: whilst the author concludes that cricoid pressure prevents gastric distension from bag-valve-mask ventilation, this is not mentioned in the results and the methodology just reports that it is feasible to do this

Authors’ Conclusions

  • Cricoid pressure can a) control regurgitation of stomach or oesophageal contents during induction of anaesthesia and b) prevent gastric distension from postive-pressure ventilation applied by facepiece or mouth-to-mouth respiration. It is contraindicated during active vomiting

Strengths

  • This is an important case series from over 60 years ago
  • The choice of technique for intubation was based on practice at the time and therefore easily applicable

Weaknesses

  • There are many…
  • Not randomised
  • Only 3 patients had cricoid pressure released and no statistical tools should be applied
  • Removing an orogastric tube in a patient who is considered ‘high risk’ is questionable now
  • Positioning head down again is not modern practice and would have increased the risk of regurgitation. Whether it reduces risk of aspiration can be debated but this case series was looking for regurgitation
  • Force used with cricoid pressure not mentioned or validated
  • There is no mention of choice of anaesthetic agents and whilst a quick acting muscle relaxant may have been used, it not clear if this did happen
  • No mention of grades of anaesthetists involved. Variability in practice including the use of positive pressure ventilation prior to intubation will affect gastric distension regardless of whether cricoid pressure is applied
  • Difficulties such as recognised oesophageal intubation are not mentioned. This would increase your risk of regurgitation
  • This is Grade 4 evidence and strength of recommendation would be low by current standards

The Bottom Line

  • There is no empirical evidence supporting the use of cricoid pressure (CP) beyond this single case series and expert opinion (grade 4-5 evidence)
  • Those advocating its use, emphasise the associated high mortality rate if aspiration occurs. Opposition point to the poor evidence for improved safety and potential harm with CP. This includes making it harder to intubate and ventilate if the anatomy of the glottis becomes distorted as well as decreasing oesophageal tone (which may actually increase the risk of regurgitation)
  • The Difficult Airway Society (DAS) are revising their guidelines for 2015 and I hope will begin to de-emphasise the overstated evidence base for CP use in RSI.

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