Pediatric Anesthesia ISSN 1155-5645
ORIGINAL ARTICLE
Emergency airway access in children – transtracheal cannulas and tracheotomy assessed in a porcine model Rolf J. Holm-Knudsen1, Lars S. Rasmussen1, Birgitte Charabi2, Morten Bøttger1 & Michael S. Kristensen1 1 Department of Anaesthesia, Centre of Head and Orthopaedics, Copenhagen University Hospital, Copenhagen, Denmark 2 Department of Otorhinolaryngology Head & Neck Surgery, Centre of Head and Orthopaedics, Copenhagen University Hospital, Copenhagen, Denmark
Keywords difficult airway; animal model; airway algorithm; emergency tracheotomy; children; transtracheal cannula Correspondence Rolf Holm-Knudsen, Department of Anaesthesia, Centre of Head and Orthopaedics, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark Email:
[email protected] Section Editor: Charles Cote Accepted 4 September 2012 doi:10.1111/pan.12045
Summary Objectives: In the rare scenario when it is impossible to oxygenate or intubate a child, no evidence exists on what strategy to follow. Aim: The aim of this study was to compare the time and success rate when using two different transtracheal needle techniques and also to measure the success rate and time when performing an emergency tracheotomy in a piglet cadaver model. Methods: In this randomized cross-over study, we included 32 anesthesiologists who each inserted two transtracheal cannulas (TTC) using a jet ventilation catheter and an intravenous catheter in a piglet model. Second, they performed an emergency tracheotomy. A maximum of 2 and 4 min were allowed for the procedures, respectively. The TTC procedures were recorded using a video scope. Results: Placement of a transtracheal cannula was successful in 65.6% and 68.8% of the attempts (P = 0.76), and the median duration of the attempts was 69 and 42 s (P = 0.32), using the jet ventilation catheter and the intravenous catheter, respectively. Complications were frequent in both groups, especially perforation of the posterior tracheal wall. Performing an emergency tracheotomy was successful in 97%, in a median of 88 s. Conclusions: In a piglet model, we found no significant difference in success rates or time to insert a jet ventilation cannula or an intravenous catheter transtracheally, but the incidence of complications was high. In the same model, we found a 97% success rate for performing an emergency tracheotomy within 4 min with a low rate of complications.
Introduction Several algorithms for management of the difficult adult airway exist. In a situation where it is not possible to oxygenate or intubate the patient, it is usually recommended to obtain access to the airway by some sort of invasive procedure, either by inserting a needle through the cricothyroid membrane or by performing a surgical cricothyrotomy. The usefulness of this approach has been well documented in adults (1–7). In children, however, the situation is different. Only one national pediatric algorithm, exists and the recommendations in © 2012 Blackwell Publishing Ltd Pediatric Anesthesia 22 (2012) 1159–1165
a cannot ventilate–cannot intubate situation are much less precise (8). Some authors suggest following the adult guidelines (9), others prefer a needle technique (10–12), while others again recommend the surgical approach (13,14). It is not possible to compare these techniques in clinical studies on small children, but suitable animal models may be useful. In a previous study, we evaluated the success rate and time needed to insert an intravenous cannula (BD Venflon Pro, Becton Dickinson A/S, Franklin Lakes, NJ, USA) transtracheally, and we also determined the success rate and time used to perform an emergency tracheotomy in a model of 8-kg piglets. We 1159
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found a success rate of only 27% for inserting the transtracheal cannula (TTC) within 2 min (15). The low success rate was surprising, and it was discussed, whether a dedicated jet device would have been a better choice. In addition, we found an 80% success rate for emergency tracheotomy within a predefined time limit of 4 min. The purpose of this study was to assess time consumption and success rate for inserting a TTC using either a jet ventilation catheter or an intravenous catheter. We also determined the success rate and time used to perform an emergency tracheotomy. Our primary hypothesis was that the time to insertion of a TTC would be faster using a dedicated jet ventilation catheter than with an ordinary intravenous catheter. Materials and methods We used an animal model based on fresh cadavers of piglets, weighing around eight kilograms, and assumed the airway of these piglets to have dimensions comparable to the airway of small children. To validate the model, we measured the distance from the skin to the second tracheal cartilage by ultrasound in 10 piglets and did a CT scan of the airway of one of the piglets and compared the result with an archive CT scan of an 18-month-old child. During the airway procedures, the piglets were placed supine and stabilized between two supporting pillows, allowing the larynx and the most proximal part of the trachea to be identified by palpation. The airway was managed by anesthesiologists who attended a course dealing with the difficult pediatric airway, and they all provided written informed consent to participate. None of the anesthesiologists had previously performed invasive airway procedures on a child or practiced on the piglet model. The participants had prior to the workshop during the course attended a lecture on transtracheal jet ventilation. Immediately before performing the airway procedure, the technique was again demonstrated in a short PowerPoint presentation. The piglets were prepared prior to the workshop, and a laryngeal mask no. 2 (Aura Straight; Ambu A/S, Ballerup, Denmark) was inserted. The airway was cleaned by suctioning, and a disposable video bronchoscope (Ascope; Ambu A/S) was inserted via the laryngeal mask with the tip placed in a subglottic position, making it possible to overlook the cranial part of the trachea during the procedure. The participants were allowed to palpate the neck of the piglets to become acquainted with localizing the larynx. For the TTC placement, a technique based on the recommendations by The European Resuscitation Council guidelines was used (16). A water-filled five-ml 1160
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syringe with a 14 GA over-the-needle catheter attached was used to locate the trachea percutaneously just distal to the cricoid cartilage at an angle of 45° caudally. After verification of correct needle position by air aspiration, the angle of the needle was reduced, and the catheter advanced off the needle into the lumen of trachea. Aspiration of air from the catheter was recommended to confirm correct position. The catheter was connected via a three-way stopcock to an oxygen source. Inspiration or ‘jetting’ was performed by occluding the free limb of the stopcock by a finger causing oxygen to be insufflated via the catheter for 1 s followed by 4 s for ‘expiration’. The participants worked in teams of two, one being the ‘anesthesiologist’ in charge and one the ‘assistant’. Afterward, the roles were switched around. The teams themselves decided the order of the roles. Each participant inserted two transtracheal cannulas using two different devices in randomized order, either a dedicated device (jet ventilation catheter for children [14 GA], VBM Medizintechnik GmbH, Sulz am Neckar, Germany) or an intravenous catheter (BD VenflonTM Pro Safety [14 GA]). To focus the timing on the procedure itself, in both cases, the device was ready and prefilled 5-ml syringes were available. The timing was started, when the participant touched the neck of the piglet and ended, when the participant declared the catheter to be located correctly in the lumen of the trachea. The number of attempts and the time used were recorded by an independent observer using a stopwatch. Maximal allowed time was 120 s which the participants were told before the study. Success was determined by the ability to insufflate oxygen via the catheter and an endoscopic view showing the tip of the catheter lying in the lumen of the trachea independent of the route of insertion, which could be translaryngeally. In the cases where a sufficient endoscopic view was not obtained, the decision of success was based on direct observation of the movements of the diaphragm through the eviscerated abdominal cavity. The video scope was operated by a person solely dedicated to this. Recordings were stored on a laptop using standard video software. The participants and the investigator were blinded for the endoscopic view until the end of the procedure. For the modified surgical tracheotomy, we selected tools readily available in the operating room: a scalpel, a pair of scissors with a sharp tip and three towel forceps. Prior to the workshop, the participants had attended a lecture on pediatric emergency tracheotomy. Immediately before performing the tracheotomy, the technique was again demonstrated in a short PowerPoint presentation. No guiding was done during the procedure. © 2012 Blackwell Publishing Ltd Pediatric Anesthesia 22 (2012) 1159–1165
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The larynx and proximal trachea were identified by palpation, and a vertical incision was performed through the skin and subcutaneous tissue from the upper part of larynx to the sternal notch. The strap muscles were grasped with two towel forceps and separated in the midline giving access to palpate and identify the trachea. The participants were encouraged not to look for, but to palpate, the tracheal rings in order to identify the trachea because in a real situation, bleeding will make visual identification of the trachea more difficult. The trachea was stabilized by grasping it with a towel forceps, and while the sharp tip of the scissors was inserted between two tracheal rings one to two cm distal to the larynx, the trachea was lifted anteriorly in order not to damage the posterior wall or resect the cartilage. A vertical cut was performed in the midline of the trachea with the scissors, and the endotracheal tube was inserted. Placement was verified by successful ventilation of the lungs. We chose to use the scissors to cut the tracheal rings, as we found this easier to control in the hands of nonsurgical trained healthcare providers. A tracheotomy attempt was considered a failure if no endotracheal tube was placed within 240 s. The participants were told about the maximum time allowed prior to the study. Complications during the procedure were documented. After the workshop, the trachea of the piglets was transected below the cricoid cartilage, and the tracheal diameter was measured to estimate which age of children the piglet trachea corresponded to. The video recordings were later reviewed by two examiners, who focused on the placement of the catheters and the occurrence of complications during the procedure. Statistics Continuous data are reported as median and interquartile range. Success rate is reported as frequency with 95% confidence interval. We compared time used for
(a)
inserting the transtracheal catheter with a paired rank sum test. The time is set to 121 s if the catheter was not in place within 120 s. Success rate is compared with McNemar’s test. A P-value
