Cricoid Pressure in Rapid Sequence Induction

This systematic review and meta-analysis aimed to determine whether cricoid pressure protects against aspiration and whether this technique adversely affects intubating conditions in adult patients. A systematic review of five databases was performed for randomised controlled trials comparing cricoid pressure to no cricoid or sham cricoid during intubation. The primary outcome was incidence of aspiration and the secondary outcomes included first attempt intubation success, time to intubation, Cormack and Lehane Grade 3 or 4 and difficult intubation. The search identified twelve high quality RCTs with 4,862 patients for inclusion. Among four studies reporting the primary outcome, there was no difference (RR=1.18; 95%CI=0.71 to 1.96; I2=0%; p=0.51). Only 3 studies were in patients at high risk of aspiration. There was significantly worse first attempt success (RR= 0.94; 95%CI= 0.89 to 0.99; I2=66%; p=0.02), time to intubation (WMD= 6.77seconds; 95%CI=4.40 to 9.14seconds; I2=97%) and laryngoscopy views (RR=1.69; 95%CI=1.41 to 2.02;I2=1%; p<0.00001) with cricoid pressure. Cricoid pressure failed to show any increase in protection from aspiration and may increase difficulty of intubation. Further studies in high-risk patients, such as intensive care patients, are required.

Cricoid pressure (CP) is often used during general anesthesia induction to prevent passive regurgitation of gastric contents. The authors used magnetic resonance imaging to determine the anatomic relationship between the esophagus and the cricoid cartilage ("cricoid") with and without CP. Magnetic resonance images of the necks of 22 healthy volunteers were reviewed with and without CP. Esophageal and airway dimensions, distance between the midline of the vertebral body and the midline of the esophagus, and distance between the lateral border of the cricoid or vertebral body and the lateral border of the esophagus were measured. The esophagus was displaced laterally relative to the cricoid in 52.6% of necks without CP and 90.5% with CP. CP shifted the esophagus relative to its initial position to the left in 68.4% of subjects and to the right in 21.1% of subjects. Unopposed esophagus was seen in 47.4% of necks without CP and 71.4% with CP. Lateral laryngeal displacement and airway compression were demonstrated in 66.7% and 81.0% of necks, respectively, as a result of CP. In the absence of CP, the esophagus was lateral to the cricoid in more than 50% of the sample. CP further displaced both the esophagus and the larynx laterally.

Pregnancy is associated with an increased risk of pulmonary aspiration during general anaesthesia, but the incidence of this complication is not well defined. We performed a retrospective database review in a tertiary care university hospital to determine the incidence of pulmonary aspiration in pregnant patients undergoing endotracheal intubation, with and without Rapid Sequence Induction (RSI), as well as face-mask ventilation and supraglottic airway devices. We included Patients in the 2nd or 3rd trimester of pregnancy and immediate postpartum undergoing surgical procedures. The primary endpoint was the occurrence of pulmonary aspiration. Data from 2,390 patients undergoing general anaesthesia for cerclage of cervix uteri, manual removal of retained placenta, repair of obstetric laceration, or postpartum bleeding were retrospectively evaluated. A supraglottic airway device or face-mask ventilation was used in 1,425/2,390 (60%) of patients, while 638/2,390 (27%) were intubated. RSI was used in 522/638 (82%) of patients undergoing tracheal intubation, or 522/2,390 (22%) of the entire cohort. In-depth review of the charts, including 54 patients who had been initially classified as "possible pulmonary aspiration" by anaesthetists, revealed that this adverse event did not occur in the cohort. In conclusion, in this obstetric surgery patient population at risk for pulmonary aspiration, supraglottic airway devices were used in approximately 60% of cases. Yet, no aspiration event was detected with either a supraglottic airway or endotracheal intubation.

Application of cricoid pressure (CP) during rapid sequence induction and intubation sequence has been a "standard" of care for many decades, despite limited scientific proof of its efficacy in preventing pulmonary aspiration of gastric contents. While some of the current rapid sequence induction and intubation guidelines recommend its use, other international guidelines do not, and many clinicians argue that there is insufficient evidence to either continue or abandon its use. Recently published articles and accompanying editorials have reignited the debate on the efficacy and safety of CP application and have generated multiple responses that pointed out the various (and significant) limitations of the available evidence. Thus, a critical discussion of available data must be undertaken before making a final clinical decision on such an important patient safety issue. In this review, the authors will take an objective look at the available scientific evidence about the effectiveness and safety of CP in patients at risk of pulmonary aspiration of gastric contents. We suggest that current data are inadequate to impose clinical guidelines on the use of CP because we acknowledge that currently there is not, and there may never be, a method to prevent aspiration in all patients. In addition, we reiterate that a universally accepted medical-legal standard for approaching the high-risk aspiration patient does not exist, discuss the differences in practice between the US and international practitioners regarding use of CP, and propose 5 recommendations on how future studies might be designed to obtain optimal scientific evidence about the effectiveness and safety of CP in patients at risk for pulmonary aspiration.

We have studied 42 female patients undergoing elective day-case surgery allocated randomly to two groups. After induction of anaesthesia an attempt was made to insert a laryngeal mask airway after application of cricoid pressure in one group or with no cricoid pressure in the other. The anaesthetist was unaware of the application, or not, of cricoid pressure. Successful insertion was achieved at the first or second attempt in 19 of the 22 patients in the non-cricoid pressure group, but in only three of the 20 patients in the cricoid pressure group (chi 2 18.62, P < 0.001). The laryngeal mask airway was then inserted successfully in all 17 patients after removal of cricoid pressure. The implications of having to remove cricoid pressure if a laryngeal mask airway is to be inserted are discussed.

The application of cricoid force remains controversial in modern practice. This review critically assesses the anatomic, physiologic, and contemporary clinical evidence of cricoid force application. There may be a sound anatomic basis to cricoid force application, involving occlusion of the postcricoid hypopharynx, but the physiologic basis is uncertain. Clinical evidence to date has not reliably determined efficacy of cricoid force application, largely because of inconsistent localization and application. Modern evidence suggests no clinically relevant implications to successful intubation with cricoid force application, particularly when videolaryngoscopy is used. Paralaryngeal force application demonstrates promise, but the evidence remains insufficient to globally change practice. Overall, the authors found uncertainty regarding the contemporary role of the application of cricoid force; however, when performed, it may be improved by localization of the cricoid cartilage using ultrasound, application of correct force by a trained assistant, and the use of videolaryngoscopy, although strong specific evidence is limited.

To assess the effect of cricoid pressure on the positioning of and ventilation through the laryngeal mask airway (LMA). In a double-blind, randomized design, the LMA was inserted with (CP[+] group, n = 20) or without double-handed cricoid pressure (CP[-] group, n = 20). Ventilation through the LMA was assessed by measuring expiratory tidal volume and judged as adequate when a mean expiratory tidal volume of > or = 10 ml.kg-1 could be obtained. The LMA position was examined by fibreoscopy. The position of the mask relative to the cricoid cartilage and the cervical spine was radiologically examined (n = 10 in each group). Ventilation was adequate in all patients in the CP[-] group but in only five patients (25%) of the CP[+] group (P < 0.001). The glottis was visible fibreoptically below the mask aperture in all patients in the CP[-] group, but in only three patients in the CP[+] group (P < 0.001). Fibreoscopy showed that the mask was not inserted far enough in the remaining 17 patients of the CP[+] group. The reason for unsuccessful ventilation in the CP[+] group was excessive gas leakage (n = 2) and/or partial or complete airway obstruction (n = 13), which was noted fibreoptically. The radiographs showed that the tip of the mask in the CP[-] group was located below the level of the cricoid cartilage (C6 or C7 vertebra). The mask tip in the CP[+] group was above this level (C4 or C5 vertebra) (P < 0.01). Cricoid pressure impedes positioning of and ventilation through the LMA.