Emergency cricothyrotomy – a systematic review

Emergency cricothyrotomy has long been established as the last-resort and potentially life-saving procedure for patients who cannot be intubated or ventilated and would otherwise face imminent death. It is essential to identify the situation and perform an emergency cricothyrotomy before the patient ends up with a cardiac arrest [1‐3]. How often “cannot intubate, cannot ventilate” (CICV) situations followed by the need for a surgical airway occur depends on the location of the patient, the qualifications and experience of the health care provider, and the medical condition of the patient. The published incidence numbers of CICV situations with the use of surgical airway techniques vary from 0 to 18.5% in the studies included in Table 1[4‐19]. However, these figures should be read with caution since some figures are old and may not be representative for the present practice in the relevant services. Furthermore, the incidence will probably vary depending on how early in the applied airway management algorithm it is recommended to perform an emergency cricothyrotomy.

Traditionally, a surgical airway has been established by making an incision through the skin and the cricothyroid membrane into the tracheal lumen through which an endotracheal tube is inserted [20]. This method is not without complications, and several investigators have modified the technique [21, 22]. In recent years, a number of commercial kits that include all of the necessary equipment to establish a surgical airway have reached the market. These commercial kits can be divided into two broad categories. One category depends on puncture of the cricothyroid membrane with a needle, followed by the insertion of a guidewire through the needle (Seldinger technique) [23]. A specially designed endotracheal tube included in the kit can be inserted into the trachea over the guidewire, if necessary, after the prior use of a dilator. The other category of commercial kits does not rely on the use of a guidewire; in these kits, a cutting device is employed to create a lumen in the cricothyroid membrane that is wide enough to accommodate the endotracheal tube included in the kit. Furthermore, some authors recommend that a temporary airway be established by puncturing the cricothyroid membrane with a wide-bore cannula through which the patient can be ventilated and oxygenated [20].

Because the CICV-situation is encountered infrequently, most health care providers have little if any clinical experience with the various techniques that can be employed. It is unclear which of the available methods that is most reliable and fastest to perform in the extremely time-critical CICV situations. The goal of this systematic review was to identify the current available research literature to evaluate the evidence-based information on this topic.

The systematic literature searches yielded 1,405 unique references, including a meta-analysis performed by Hubble and coworkers [28]. A total of 108 full text articles were retrieved, and two authors read them independently; 24 studies were included in this review (Figure 1) [21, 22, 24, 25, 29‐48]. The 85 studies that were excluded in this process did not include sufficient information on comparison between two or more techniques to be included in this review. All the remaining 24 studies were prospective experimental studies with varying degrees of randomisation (Table 3). Studies involving human cadavers (ten studies), various airway simulators (eight studies), a pig laryngeal model (three studies), anaesthetised sheep (two studies) and sheep cadavers (one study) were included. The interventions were performed by students and professionals from a variety of disciplines (anaesthesiology, emergency medicine, intensive care unit physicians, medical students, paramedics). In the study involving the largest number of participants, 64 anaesthesiologists took part, while the smallest study in this respect involved two anaesthesiologists. Studies were included from the following eight countries: USA (eight studies), Germany (five studies), Austria (three studies), Australia (two studies), Ireland (two studies), United Kingdom (two studies) and one each from Canada and The Netherlands. The oldest study was published in 1993, and the most recent was published in 2012.

The risk of bias of the included studies is summarised in Figure 2. Methods of randomisation and allocation were poorly described in the majority of the articles. Therefore, we have concluded with an unclear risk of bias for most of the studies.

Relevant Forest plots are presented in Additional file 1 and characteristics of the included studies are summarised in Table 4.

Nine groups of comparisons were included:

This is to our knowledge the first systematic review comparing all commercial kits designed to perform emergency cricothyrotomy with surgical and needle techniques. The main result of this review is that no technique has been proven to be superior to the others, regarding success rate or time consumption. The quality of evidence is low or very low for several reasons. The studies are uniformly small, so that even though a number of studies comparing two or more techniques have been published, relatively few events have actually been analysed. When evidence is drawn from small studies, the results are uncertain and normally contain large confidence intervals. A common consequence of small trials is heterogeneity among studies, of which there are multiple examples in this review. A tendency exists toward many unique comparisons, rather than more general comparisons, and there is large variation among the roles of health care providers who perform these procedures. However, there were no studies involving surgeons. This can be interpreted that the perceived success rate with surgical techniques for experienced surgeons is so high that they do not find the commercial kits an interesting alternative even though there are no studies supporting this notion.

The studies were performed on a number of models varying from human cadavers and dead animal models to a multitude of airway models. It was difficult to make direct comparisons among studies since the primary study authors to a large degree had defined their own unique starting and stopping points in the time measurements.

Emergency cricothyrotomies are performed under stressful conditions and severe time pressure. If unsuccessful, these procedures can prove fatal or severely disabling for patients. In a laboratory setting, it is very demanding to achieve the same level of stress. Furthermore, it can be necessary to perform emergency cricothyrotomies under suboptimal conditions, such as prehospital settings, in which a lack of light, background noise and entrapped patients may add to the difficulty. Of the studies identified in this review, only one study included these types of factors that most likely affect both the success rate and the time consumption [28, 30]. Furthermore, as a result of the models used, the procedures were performed without bleeding. In real life situations, bleeding will occur, thus increasing the level of difficulty of the procedure.

In the majority of the studies, there were no upper time limit that should not be exceeded for the procedure to be accepted as successful, and – with one exception – in the studies that operated with an upper limit it was between 180 and 300 seconds. An emergency cricothyrotomy will usually be performed in CICV-situation when other devices have failed and the clinical condition of the patient has already started to deteriorate. In such situations, the operator does not have 180 to 300 seconds at their disposal to perform the procedure. Salah and coworkers on the other hand chose to publish the success rate after 40 seconds, an – in our opinion – clinically much more realistic time frame, and none of the participating anaesthesiologists succeeded to establish a secure airway with Mini in this study even after five attempts [33]. In contrast, after five attempts approximately two thirds of the participants managed to establish a secure airway with the surgical technique. This study underscore the point that focusing on success rate only is insufficient; time aspects are also essential. In general, the difference in success rates may reflect varying definition of success, and operator experience, but study model probably also has an influence on outcome.

Arnd, Mlkr and Mini are the three Seldinger-based techniques included in this review, and we only identified a single study where two Seldinger-based techniques were compared. The study in which Mlkr and Mini were compared was the only study where a statistically significant difference in success rate between two devices/techniques was found. Mini was significantly faster than Mlkr, and in this study, Mini had a 100% success rate in contrast to the 74% success rate of Mlkr.

In the five different comparisons between a kit based upon the Seldinger technique and a kit not based upon this technique (Mlkr vs. Pati, Mlkr vs. PCK, Mlkr vs. QT1, Mlkr vs. QT2 and Mini vs. QT1), no statistically significant difference in the success rate was found. However, these studies were small, as were all the studies included in the review, making it necessary to interpret these results with great caution. The success rate is not the only important parameter in the context of emergency cricothyrotomies; time consumption is also critical. Individual studies tended to use their own unique combinations of starting and stopping points, making the evaluation of time comparisons difficult. Even so, it is evident that in some cases, the Seldinger-based technique was faster than the non-Seldinger technique, while in other studies, the opposite result was found. This could partly be due to different studies using different techniques and time measurements. However, when Mlkr and PCK were compared, for instance, two studies found that Mlkr was the faster technique, while two studies concluded that PCK was the faster technique. One might suspect that in those studies where anaesthesiologists performed the procedures, the Seldinger-based techniques would be faster because of the familiarity anaesthesiologists have with this technique. However, in the three comparisons of Mlkr and PCK performed by anaesthesiologists, PCK was faster than Mlkr in two of the three studies.

In four studies, a Seldinger-based technique was compared with a surgical technique (Arnd vs. Surg, Mlkr vs. Surg, Mlkr vs. Csci, Mini vs. Surg), and no statistical difference in success rate was detected. In the large majority of the comparisons, the surgical technique was faster than the Seldinger technique, even though in one study, the opposite result was found. These studies indicate that surgical techniques are generally faster than Seldinger-based kits, while both techniques have high success rates. This may indicate that surgical techniques should be favored by most healthcare providers. However, it is not unreasonable to assume that the lack of bleeding in the majority of the study models may – especially for the surgical techniques – result in artificially short procedure times and high success rates [49].

In the two studies where a Seldinger-based technique was compared with a needle technique (Mlkr vs. Trac, Mini vs. Need), the success rate was 100% for all procedures. Regarding time consumption, the results conflicted, with one study showing that the Seldinger-based technique was faster and the other showing the opposite result. This discrepancy may be explained by the fact that neither the Seldinger-based technique nor the needle technique used was the same in the two studies.

Seven different comparisons between a non-Seldinger kit and an open surgical technique were found (Airf vs. Surg, Pert vs. Surg., PCK vs. Surg, QT1 vs. Surg, QT2 vs. Surg, QT1 vs. Csci, Trqu vs. Surg). It is a weakness that five of the seven comparisons were only performed once, but this is the case for most of the currently published comparisons in this field. Conflicting results were obtained. In some instances, the non-Seldinger technique was faster, while in other instances the surgical technique was. Even in the two comparisons that were studied in more than one publication, the results conflicted, ultimately not indicating which technique was faster. The success rates were uniformly high for all devices in all studies.

There were also seven different comparisons of a non-Seldinger kit compared to a needle technique (Airf. vs. Need, Pati vs. Trac, PCK vs. Need, QT1 vs. Need, QT2 vs. Need, QT2 vs. Trac, Trqu vs. Need). All comparisons were performed only once. Each study was small, and no significant differences in success rates were detected. With the exception of the comparison between QT2 and Trac, the needle technique was found to be the faster technique, although the time differences were small and insignificant. Furthermore, it has been argued that needle techniques – in contrast to the other techniques - do not result in an airway that leads to adequate oxygenation and ventilation due to the small calibre of the artificial airway. The needle may kink and is not suitable for patient transport.

Four different comparisons between two surgical techniques were identified (Surg vs. Bair, Surg vs. RFST, Surg vs. Csci, RFST vs. BACT). All techniques had a high success rate, and no significant difference in success rate was found. However, these studies were also small, and, as was the case with all comparisons performed, any difference must be pronounced to have been detected. However, significant time differences were shown to indicate that BACT was faster than RFST, which in turn was faster than Surg. Csci was also significantly faster than Surg, but this technique has never been compared to RFST or BACT.

The field of techniques for establishing an emergency cricothyrotomy is hampered by the many very small studies performed. There is limited evidence of low and very low quality comparing these different emergency techniques for use in CICV situations. That none of the techniques produced better results than the others in these studies does not necessarily indicate that they are all equally good, and these conclusions will likely change as new evidence becomes available. This review does not justify recommending one technique over others. Success may rely on the operator’s experience and skill/training and not on the technique chosen.

Search strategy: 10.04.2013

Search strategy: 10.04.2013

#1 (cricothyr* or cricotomy or cricothracheotomy or thyrocrico* or intercricothyro*) (39)

#1 (quicktrach or seldinger or portex or pck or minitrach or melker) 184

#2 (portex or cook or vbm) 2997

#3 ((difficult or definite or management or surgery or surgical or obstruction* or control) NEAR/2 airway*) 2123

#4 (cricothyr* or cricotomy or cricothracheotomy or thyrocrico* or intercricothyro*) 39

#5 (( #1 OR #2 ) AND ( #3 OR #4 )) 49

#6 (#5 AND NOT #4) 45

TI ( cricothyr* or cricotomy or cricothracheotomy or thyrocrico* or intercricothyro* ) or AB ( cricothyr* or cricotomy or cricothracheotomy or thyrocrico* or intercricothyro* )

(261)

(MH "Cricothyrotomy") (87)

S32 S30 and S31 (25)

S31 S28 or S29 (1102)

S30 S25 or S26 or S27 (6159)

S29 portex or cook or vbm (925)

S28 TX quicktrach or seldinger or portex or pck or minitrach or melker (227)

S27 TX difficult N2 airway or definite N2 airway or management N2 airway or surgery N2 airway or surgical N2 airway or obstruction* N2 airway or control N2 airway (5976)

S26 TI ( cricothyr* or cricotomy or cricothracheotomy or thyrocrico* or intercricothyro* ) or AB ( cricothyr* or cricotomy or cricothracheotomy or thyrocrico* or intercricothyro* ) (198)

S25 (MH "Cricothyrotomy") (72)

#2 Search #1 Limits: published in the last 1 year

#1 Search cricothyr* or cricotomy or cricothracheotomy or thyrocrico* or intercricothyro*

#58 Search #54 AND (#55 or #56) Limits: published in the last 1 year

#57 Search #54 AND (#55 or #56)

#56 Search cricothyr* or cricotomy or cricothracheotomy or thyrocrico* or intercricothyro*

#55 Search (difficult or definite or management or surgery or surgical or obstruction* or control) and airway

#54 Search ((quicktrach or seldinger or portex or pck or minitrach or melker) ) OR portex or cook or vbm

(cricothyr* or cricotomy or cricothracheotomy or thyrocrico* or intercricothyro*).tw