In Response.

Abstract

We read with great interest the letter by Priebe1 regarding our review of the use of cricoid pressure (CP).2 While many of the points1 actually reiterate, not dispute, our original conclusions, we again underscore the purpose for our review, stated clearly in our opening paragraph: “[w]e therefore review the available scientific [emphasis added] evidence of the effectiveness and safety of CP…”. We are well aware that clinical care standards vary immensely.2 We also recognize that Germany has largely abandoned CP use in clinical practice3,4 and that the author himself is a strong advocate against CP use.5 Alternatively, other experts strongly defend this procedure.6 One issue that requires clarification is Priebe’s reference to the Sellick Interest in Rapid Sequence Induction (IRIS) randomized trial and the intubation difficulty posed by CP.7 We reanalyzed the original IRIS trial data of Cormack-Lehane scores. We used χ2 test, which yields significant P values in large sample sizes.8 We herein report Cramer’s V of 0.09 as the strength of association measure,9 suggesting a weak association between CP and higher Cormack-Lehane scores. Moreover, operators were asked to release CP in only 14% of CP cases and in 5% of sham group, improving the glottic view in 62% and 33% of cases, respectively.7 The sham group reported improvement in Cormack-Lehane score after sham interruption,7 likely reflecting the assessors’ anticipation of CP use. We suggest that most of the experienced operators could detect CP at laryngoscopy, while the sham itself is likely to be readily guessed (more frequently than by chance) by the operators, making them more likely to report an improved view after its release. In clinically relevant outcomes, the groups did not differ in the number of attempts at intubation or arterial oxygen desaturation, and median intubation times were similar (27 seconds in CP group and 23 seconds in sham group); a 4-second difference is statistically significant7 but not clinically relevant.10 The IRIS trial concluded, “… the interference of the CP with airway control has previously been overestimated.” Moreover, a “…significant increase in the incidence of difficult tracheal intubation…” was not observed, as Priebe1 suggested. From an evidence-based medicine point of view, the IRIS (noninferiority) study7 was severely underpowered. This limitation is acknowledged in the accompanying editorial: “the noninferiority of withholding CP could not be proven because of the overall lower-than-expected incidence of aspiration.”11 Therefore, there is no evidence-based foundation for the selective (and likely erroneous) interpretation, “the study nevertheless documents lack benefit of the application of CP with simultaneous interference with optimal airway management.”1 Alternatively, we would be remiss if we did not also acknowledge study’s tremendous value, as it is the first study granted ethical permission not to use CP during rapid sequence intubation in patients. We continue to recommend that investigators use previous findings effectively in planned research designs, and include generally accepted indicators such as percent of glottic opening score,12,13 upper lip bite test (which has the highest sensitivity for diagnosing difficult laryngoscopy),14 and modified Mallampati test (which has the highest sensitivity for diagnosing difficult tracheal intubation),14 none of which were used in the IRIS study.7 With strong opinions on either side of the argument,1,6 we believe we provided a balanced review of current evidence on CP use, and we are not surprised that our article2 incited controversy. We sincerely hope the debate will galvanize future researchers to provide definitive evidence that can then be translated into guidelines, rather than the consensus opinions that drive current clinical care. Marko Zdravkovic, MDDepartment of Anaesthesiology,Intensive Care and Pain ManagementUniversity Medical Centre MariborMaribor, SloveniaFaculty of MedicineMaribor, Slovenia Mark J. Rice, MDDepartment of AnesthesiologyVanderbilt University Medical CenterNashville, Tennessee Sorin J. Brull, MD, FCARCSI (Hon)Department of Anesthesiology and Perioperative MedicineMayo Clinic College of Medicine and ScienceJacksonville, Florida[email protected]