Research Critique of Management of the Difficult Airway

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Introduction

This paper will critique “Prehospital Management of the Difficult Airway: A Prospective Cohort Study” by Keir Warner, Sam Sharar, Michael Copass, and Eileen Bulger, from the Journal of Emergency Medicine, Vol 36., pp 257-256, 2009.

The purpose of the study is to properly define how to manage difficult airway in prehospital management. The failure to set up an ultimate airway is the main reason for death when sufficient oxygenation and ventilation cannot be otherwise obtained. In this instance, death is avoidable as early airway management is very important in cardiac arrest patients and the exhausted, but is also significant in patients at danger for the progressive loss of airway patency and individuals at danger for aspiration, such as those individuals with head or neck injuries. Oral endotracheal intubation (ETI) is the present standard for the best airway administration and accomplishment rates in the prehospital locations vary from 33–100% (Wang, 2006). This unpredictability has been credited to advanced life support (ALS) provider differences in the level of early preparation, ongoing learning, medical mistake, or access to neuromuscular blocking agents (NMBAs) (Bulger et al, 2007). Numerous studies in both the field and the Emergency Department (ED) have established enhanced ETI success rates with the use of NMBAs. Continuing ability maintenance may also be very important, as the incidence of ALS provider performance of airway measures is considerably associated with ETI success rates (Garza et al, 2003).

The paper was able to discuss its riddance. It add up to these ALS provider issues, and why many patients need definitive airway access may be complicated to intubate due to anatomic irregularities, distressing injuries, foreign bodies, incapacity to open the jaw, or insufficient muscle relaxation. Such “difficult airway” patients have an advanced occurrence of complications and an increased threat of death. If a patient cannot undertake successful ETI in the prehospital location, the ALS provider must either return to bag-valve-mask ventilation or resort to a more sophisticated airway method. a number of highly developed airway measures have come out to help administer these demanding cases, including surgical cricothyroidotomy, retrograde ETI, transtracheal jet ventilation (TTJV), and Eschmann sty let (gum elastic bougie)-assisted ETI. Lately, with the arrival of supraglottic airway devices such as the Combitube and the laryngeal mask airway, the position of prehospital intubation has been questioned, as achievement rates are extremely changeable in pre-hospital ETI (Bulger et al, 2007). The reasons for this reading were to broadly assess a large legion of patients experiencing prehospital endotracheal intubation with and without rapid sequence intubation (RSI), and especially illustrate the incidence, presentation, and management of the difficult airway and look at consequences of airway breakdown.

Study Design

The study design focused on a group of patients who undergo attempted oral ETI in the prehospital location over a 4-year period. It was carried out in conjunction with the Fire Department Medic Program and nine hospitals within the city of Seattle. The procedure was evaluated and accepted by the University Institutional Review Board (IRB), as well as the IRBs for each other hospital. Subjects were incorporated if they were assessed by ALS providers and undergo attempted ETI in the prehospital location. Patients were disqualified if they undergo inter-facility transfers after previous failed airway management. Patients were divided into two groups: “non-difficult airway,” classified as successful endotracheal intubation within four attempts (two attempts per provider); or “difficult airway,” describe as more than four attempts at ETI or the need for attempting any advanced airway management process.

EMS System and Paramedic Education

This course necessitates 2500h of educational, laboratory, and field practice for certification. All paramedics are taught to carry out rapid sequence intubations. In addition, all paramedics are mandatory to recertify their airway management expertise every 2 years in an advanced airway clinics consisting of educational lectures by anesthesiology, and surgical airway laboratory the medical director and trauma surgeons. A minimum of 12 simple ETIs per year is mandatory for qualifications.

Airway Management Protocols

Throughout the learning period, the EMS scheme use many different methods for airway management, including BVM with oral/nasal pharyngeal airways, endotracheal intubation, Eschmann-assisted intubation, retrograde intubation, TTJV, and surgical cricothyroidotomy. The application of RSI is permitted under the direction of the physician providing medical control. All medics are taught to use the paralytics, succinylcholine at a dose of 1–1.5 mg/kg for laryngoscopy, and pancuronium (0.1 mg/kg) for post-intubation paralysis during transfer. Previous to ETI attempts, every effort is made to optimize intubating circumstances, including the use of head elevated positioning (except trauma) and cricoid pressure or external laryngeal handling. Each medic is permissible for two attempts at intubation before going on to the complicated airway algorithm.

Data Collection

Potential information was collected for each qualified patient using a consistent airway management survey form completed at the termination of the patient’s prehospital care by the provider performing the airway process. This survey form detailed the number of intubation attempts, series, and outcomes of advanced airway measures and issues contributing to a complicated airway. The medics documented their explanation of the features contributing to tricky ETI and these were later on classified by the abstractor. This information was then combined with the electronic database uphold by the Fire Department, which coconf thorough prehospital information for all patient come across. Integrating these two balancing datasets guaranteed that a prehospital questionnaire was finished for every patient who undergoes attempted ETI. The Fire Department’s electronic record also offers additional factor regarding demographics, means of injury or sickness, vital signs and preliminary Glasgow Coma Scale (GCS) score, use of NMBAs or sedatives, measures performed, and destination of transfer.

All patients meeting complicated airway criterion undergo hospital follow-up with complete chart evaluation. The hospital follow-up was carried out in a display fashion by a skilled chart abstractor. At set periods throughout the learning, the abstractor would travel to all hospitals within the city and gather the essential data from the patient’s chart. Hospital records were collected by means of a standardized form and included ED airway administration, prehospital airway difficulties perceive after hospital admittance, occurrence of shock and need for cardiopulmonary resuscitation (CPR), admitting/discharge analysis, and initial chest X-ray study outcomes. Added outcome actions included medical analysis of aspiration and succeeding progress of pneumonia, hospital death, presence and severity of neurologic deficit, and final outlook. Neurologic result was based on the thought of the treating physician and the discharge location. Information is reentered into an Excel folder by a skilled study abstractor.

Statistical Analysis

The study compared the demographic, injury severity, and outcome data were performed using the Student’s t-test for continuous variables and the chi-squared test for categorical variables. Analysis was conducted using SPSS (SPSS 13.0; SPSS Inc., Chicago, IL). Significance was considered at p <0.05.

Results

The study found that between April 2001 and April 2005 there were 80,501 ALS patient contacts, of which 4114 undergo attempted ETI. Of these, 23 patients were disqualified as inter-facility transfers with previous failed airway management, leaving a total of 4091 (5.1%) patients registered. Patients vary in age from 1to107 years, together with 49 children ages 1 to 14 years. Of these 4091 patients, 3961 (96.8%) undergo successful oral ETI within four attempts and include the non-difficult airway group, leaving 130 (3.2%) patients in the difficult airway group. The mean and median numbers of ETI attempts were 1.3 and 1, correspondingly, for the non-difficult airway group, compared to 5.4 and 5, in that order, for the difficult airway group. There was no dissimilarity in demographic variables among the two groups. In general, 83% of patients were seen for medical complaint, with 17% being care for distressing injuries. There was a somewhat higher percentage of trauma patients in the difficult airway group (20%vs.15%), although it did not accomplish statistical implication. The study found that there was no distinction between the groups concerning the proportion of patients in cardiac arrest.

Use of Neuromuscular Blocking Agents

The study further established that 62.3% of patients undergo RSI by means of succinylcholine for paralysis. The most distinguished factor coupled with not needing RSI was the presence of cardiac arrest necessitating CPR, present in 86.1% of patients who did not need RSI, but only 8% of patients who did need RSI (p<0.001). apart from those patients in cardiac arrest, the mean initial GCS score was also considerably lower in patients who did not go through RSI (7.2) in contrast to those who did (8.7, p <0.001). There was no important disparity in the proportion of difficult airway patients between those who received NMBAs and those who did not (3.4% vs.2.8%, respectively).

Prehospital Difficult Airway Management

Of the 130 patients in the difficult airway group indicated in the study, 102 patients received more than four attempts at ETI and 28 patients goes straight to an advanced airway technique. Of 130 patients in the group, 59 were effectively intubated orally following more than four attempts; while 43 patients were administer with BVM ventilation for transfer to the hospital. There were 9 patients for whom ultimate airway access could not be accomplished and who could not be efficiently ventilated using a BVM. In general, there were 40 attempts at advanced measures with unreliable success rates. Of these measures, nasal and digital intubation had the worst success rates, at 0% and 14.3%, in that order. The most ultimate of the advanced interventions was surgical cricothyroidotomy, with a success rate of 91%. Of the 130 patients in the difficult airway group, a safe prehospital airway was completed in 78(60%), for an overall success rate of 98.7% for all 4091 patients. In the post-intubation questionnaire, ALS providers were requested to personally recognize factors that may have contributed to the complicated airway. The most usually explain features were anterior trachea (39.2%), small mouth (30%), and foreign body aspiration (27%).

Transport and Hospital Management of Difficult Airway Cohort

Of the 130 difficult airway patients, 27 died in the field and 10 were gone to hospital record due to complexity of matching hospital and prehospital accounts, leaving 93 patients transferred to an ED with total follow-up. Of these, upon arrival in the ED, 57 patients (61.3%) had a safe airway and 33 (35.5%) were effectively managed by BVM ventilation. Twenty-two patients (23.7%) were in shock (systolic blood pressure <90mmHg) and 12 patients (12.9%) were in full cardiac arrest. Of the 33 patients effectively managed by BVM ventilation throughout transfer to the hospital, 18 (54.5%) were orally intubated in the ED by direct laryngoscopy, 5 (15.1%) were orally intubated with the help of an Eschmann stylet, 3(9.1%) were intubated with the help of a fiber optic device, and 7(21.2%) were not intubated and were instead managed using non-invasive techniques. Of the 9 patients who are unsuccessful to have any best airway placed in the prehospital location and were not capable to be efficiently ventilated, 4 were found in medical cardiac arrest and were pronounced deceased after initial laryngoscopy attempts and failed ventilation by BVM, but before surgical airway attempts. The remaining 5 patients were considered failed airway patients. The remaining 3 patients were found in cardiac arrest and transferred to the hospital, where they were found to have suspected esophageal intubation and underwent subsequent ED ETI.

Complications of the Prehospital Airway Management

Among the sum of 4091 patients with prehospital intubation attempts, 3 patients (0.07%) had an unrecognized esophageal placement of their endotracheal tube (ETT).

Two extra (pediatric) patients had an unintentional extubation on the way to the hospital and were then reintubated in the ED. Eleven patients (0.3%) go through prehospital surgical cricothyroidotomy throughout the learning period. Of these, one patient died in the field and the remaining patients were transferred to the hospital.

There were two reported complications taking place in 2 patients. One of these patients required operational reconsideration for extreme bleeding and trachea damage, and the other patient had sustained a gunshot wound to the neck and had poor ventilation, oxygenation, and continuing CPR.

Hospital Outcome of Difficult Airway Cohort

Of the 93 patients transported to the hospital, 30 died during their hospital stay, with a third of deaths occurring in the ED and 60% in the Intensive Care Unit. Of these deaths, airway complications were judged as possible contributing factors in 6 patients. Seventeen patients had aspiration of either gastric contents or foreign body, diagnosed on arrival to the ED, with 88.2% occurring in the prehospital phase of care. Five of these patients went on to develop aspiration pneumonia. Of the 63 patients who survived to discharge, 79.4% returned to baseline neurologic status, leaving 13 patients with a persistent cognitive neurologic deficit. Only 2 of those with neurologic deficit were thought to be related to initial airway management, with the remainder attributed to the underlying disease process or associated injury. The pooled mortality for the difficult airway cohort, including prehospital and hospital deaths, was 43.8%.

Pediatric Intubation

During the 4-year study period, medics intubated 49 pediatric patients (aged ≤14 years). Most pediatric patients were seen for medical issues (n 24, 49%), including 5 with severe respiratory distress (10.2%), 4 with respiratory arrest (8.2%), 10 with cardiac arrest (20.9%), with the remaining medical complaints a result of exacerbation of previous medical conditions. Forty-one percent of pediatric patients were intubated for traumatic injury; the most prevalent mechanism was 6 patients struck by moving vehicle (12.2%), followed by 4 in motor vehicle crashes (8.2%) and 4 falls from height (8.2%). Eight percent of pediatric patients had environmental injury such as burns (2%) and drowning (6%). Overdoses, both accidental and those with intent to harm self, accounted for 6.1%. Rapid sequence intubation was used in 26 pediatric intubations (53%), with succinylcholine as the primary paralytic, and atropine available for premedication. Sixty- one percent of patients were intubated on the first laryngoscopic attempt, with success rates rising to 92% by the third attempt. Three patients were judged to be difficult airways, one patient requiring six attempts at ETT placement and the other 2 patients having unintentional extubation after uncomplicated initial ETT placement. Both patients who were extubated had uncuffed endotracheal tubes placed. The overall difficult airway rate for the pediatric population was 6.1%.

Discussion / Conclusion

The study described prehospital “difficult airway” as one needing more than four attempts at ETI or the utilization of any advanced airway management methods. An earlier study by Bulger et al (2007) already indicated that ETI can be carried out in the prehospital setting with success rates as high as 98.2% and as low as 33%. The amount of ETI attempts also may relate to concluding patient result, as earlier hospital studies have shown a rising occurrence of hypoxia with growing laryngoscopic attempts (Wang, 2006). The study further reviewed the maximum of three attempts at oral ETI recommended as sensible to accomplish prehospital ETI by Wang (2006) as Davis et al (2003) reported a remarkable increase in prehospital airway management success rates for patients with severe head injury (39% to 86%) with the addition of NMBAs for airway management. In the difficult airway group, 36% of patients received only BVM ventilation and were transferred to EDs with no main unpleasant consequences. On the other hand, if the patient cannot be intubated and also cannot be sufficiently oxygenated or ventilated with BVM ventilation, the condition maybe hastily deadly. In such cases throughout the study period, TTJV, retrograde ETI, and surgical cricothyroidotomy were accessible to ALS providers as persistent airway additions to rapidly institute ventilation and oxygenation. Surgical cricothyroidotomy offer best airway access but is persistent and necessitate important training and skill preservation. Bair et al. report a surgical cricothyroidotomy rate of 1.1% in the ED, and a prehospital cricothyroidotomy rate of 10.9%. In this study, the cricothyroidotomy rate was only 0.3%, signifying that this process is not often required in a prehospital ALS structure with widespread experience and access to NMBAs to make possible intubation. The most generally observed downside of cricothyroidotomy is the high difficulty rate, including unwarranted bleeding, aspiration, tracheal/cricoid ring breakage, damage to other close by anatomic structures, and fake airway passage into the extra-tracheal space. This article review established an 18% complication rate of field cricothyroidotomy, which is similar to other studies (Bair, 2003).

This review of the study understood that 3 out of 4091 patients with unrecognized esophageal intubation, all of whom were in cardiac arrest at the time of ETI, making the colorimetric CO2 detect or a less reliable indicator of endotracheal tube position.

As Katz and Falk (2001) reported, constant expired CO2 (EtCO2) checking can be used to lessen esophageal tube placement and ETT displacement in the prehospital setting. Also, ETI has been shown to facilitate hyperventilation that leads to cerebral ischemia that is mainly detrimental in patients suffering from traumatic brain injury (Warner, 2007).

It is then concluded that research in this area is divided, with some studies showing increased survival in patients undergoing prehospital ETI by aeromedical crews and paramedics (Bair, 2003). On the other hand, some studies have shown that prehospital ETI by paramedics is disadvantageous after brain injury while the paper concludes that ED intubation and survival after traumatic brain injury, definitive securing if airway with ETI increases survival.

Reference

Wang HE, Yealy DM. (2006). How many attempts are required to accomplish out-of-hospital endotracheal intubation? Acad Emerg Med;13:372–7.
Bulger EM, Nathens AB, Rivara FP, MacKenzie E, Sabath DR, Jurkovich GJ. (2007). National variability in out-of-hospital treatment after traumatic injury. Ann Emerg Med; 49:293–301.
Davis DP, Ochs M, Hoyt DB, Bailey D, Marshall LK, Rosen P. (2003). Paramedic-administered neuromuscular blockade improves pre-hospital intubation success in severely head-injured patients. J Trauma; 55:713–9.
Garza AG, Gratton MC, Coontz D, Noble E, Ma OJ. (2003). Effect of paramedic experience on orotracheal intubation success rates. J Emerg Med; 25:251–6.
Bair AE, Panacek EA, Wisner DH, Bales R, Sakles JC. (2003). Cricothyrotomy: a 5-year experience a tone institution. J Emerg Med; 24:151–6.
Katz SH, Falk JL. (2001). Misplaced endotracheal tubes by paramedics in an urban emergency medical services system. Ann Emerg Med; 37:32–7.
Warner KJ, Cuschieri J, Copass MK, et al. (2007). The impact of prehospital ventilation on outcome following severe traumatic brain injury. J Trauma; 62:1330–8.

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