Intubation of patients with angioedema: A retrospective study of different methods over three year period.

BACKGROUND: Angioedema (AE) is edema of the skin, subcutaneous tissue and/or submucosal tissues, resulting from extravasation of intravascular fluid. Swelling of the supraglottic mucosa can lead to airway obstruction with consequent hypoxia, brain damage and death. To date, fiberoptic bronchoscope (FOB) intubation of the spontaneously breathing patient is the preferred method for an anticipated difficult intubation. However, other alternative devices can be utilized to intubate angioedema successfully.
MATERIALS AND METHODS: A retrospective chart review was performed over a three-year period (2008-2010) of all patients with angioedema that required airway intervention. We hypothesized that fiberoptic intubation would have a higher success rate for intubation attempts; however, would take longer to perform when compared to videolaryngoscopic (VL) intubation. Outcomes for FOB versus VL intubations were reviewed, along with alternative miscellaneous methods of tracheal intubation in the setting of angioedema.
RESULTS: Thirty-three patients were grouped, according to the chosen method of intubation into FOB (n=12), VL (n=11), and miscellaneous (n=10) groups. No significant difference was found in first intubation attempts or number of intubation attempts between the three groups. Duration of time to perform successful intubation revealed a significantly shorter intubation time (P<0.05) in the VL group (6.9±0.9 min) and miscellaneous group (9.1±2.0 min) than that of the FOB group (10.4±0.7 min).
CONCLUSION: This retrospective review of intubation methods showed that VL could be performed faster than FOB without an increase in adverse events.

INTRODUCTION

Angioedema manifests as episodes of localized swelling in the dermis, subcutaneous tissue, mucosa and/or submucosal tissues. When angioedema affects the airway, it is a potential cause of complete airway obstruction which could have fatal consequences if left untreated.[1] Etiologies of this condition include; idiopathic, genetic, allergic, toxic or drugs. Common drugs associated with angioedema: Non-steroidal anti-inflammatory drugs including aspirin, angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor antagonists (ARBs).[1234567]

The challenge of this condition is whether to observe the patient or immediately secure the airway, either by intubation or surgical airway. Airway edema may become so severe and extensive that tracheotomy may not be successful in providing a patent airway.[8]

Until recently, fiberoptic intubation of a spontaneously breathing patient was regarded as the “gold standard” for anticipated difficult airway.[91011] However, within the last decade, the use of new videolaryngoscopic devices (GlideScope®, the Pentax AWS, Truview EVO2) has increased. These devices have been observed to provide a viable alternative for management of difficult airway.[12] To date, there has been no published data regarding the comparison of fiberoptic bronchoscope versus the videolaryngoscopic devices in the setting of angioedema.

In this study we retrospectively evaluated successful tracheal intubations using the fiberoptic bronchoscopy versus alternative methods such as VL, intubating LMA, and standard direct laryngoscopy. The focus of the study was to determine whether or not fiberoptic bronchoscopy was superior to videolaryngoscopy and other alternative intubating techniques.

MATERIALS AND METHODS

A retrospective chart review was conducted over a three year period (2008-2010) at our institution. This study was approved by the governing Institutional Review Board protocol receipt number 1009008817. As this was a retrospective study, informed consent could not be obtained, but data was suitably anonymised according to IRB recommendations. All investigators in this study read and followed the guidelines found in the Declaration of Helsinki. Potential charts were identified by a computerized search of the hospital's records (Surginet, Cerner Corporation, Kansas City, MO) with the search terms being “emergency intubation” and/or “emergency tracheostomy”. All tracheal intubations were performed by attending anesthesiologist in the operating room with a trauma surgeon on standby for possible tracheostomy. All 10 attending anesthesiologists had 3 years or more of experience. The GlideScope® device had been used by all ten of them one year prior (2007-2008) to the time period reviewed. All videolaryngoscopy was performed with GlideScope® (Verathon Inc., Bothell, WA). Airway interventions outside of the operating room setting were not included in this review.

Patient charts were analyzed to determine the cause of the angioedema, patient's age, presenting symptoms, location of edema, and duration of intubation. Also, recorded was the device used for intubation, the proportion of successful first intubation attempts, failures of any other device, progression to a surgical airway, and complications of the intubation. The outcome of each intubation effort was evaluated, comparing the number of attempts to secure the airway and length of time taken for intubation. In this study, duration of intubation time was defined as the period of time beginning from administration of intravenous medications until an appropriate end-tidal CO2 capnograph trace was recorded. Hemodynamic parameters were stable in all charts that were reviewed. Old age was not a factor for hemodynamic instability in these particular cases reviewed. Furthermore, the investigators noted each specific airway management technique utilized.

Inclusion criteria included patients aged 18-80, and a diagnosis of angioedema that compromised the airway and required intubation as determined by the anesthesiologist. All patients in this study received corticosteroids, H-1 and H-2 blockers in the emergency department prior to airway management. The anatomical site and symptoms of each angioedema case were recorded in Table 1. The decision to proceed with intubation was based on angioedema resulting in one or more of the following: Stridor, shortness of breath, difficulty controlling secretions, hypoxia (O2 saturation below 90%), and hypercapnia (PaCO2>45 mmHg on ABG). Other difficult airways that did not meet the clinical criteria for the diagnosis of angioedema were excluded. Electronic data handling included each patient being assigned a three digit number kept on a secured master list. All gathered information was stored in accordance with HIPPA guidelines for the protection of any confidential patient information.

Table 1

Angioedema presenting site and symptoms in each patient group

Statistical analysis

Comparisons between the 3 study groups used a parametric analysis of variance (ANOVA) procedure to examine mean differences between study groups on the continuously scaled variables of number of attempts to secure airway and duration of intubation time. Assumptions of normality and/or homogeneity of variance were checked and verified. Categorical data (occurrence of successful first intubation attempt) was measured using a Chi-squared test. As the data for groups for duration of intubation showed a non-normal distribution, a Kruskal-Wallis ANOVA was used to examine differences between the means. Significant differences between the groups for duration of intubation were measured with pair-wise Mann-Whitney tests. Data was as expressed as mean±standard error. Statistical significance was set at a P-value≤0.05.

RESULTS

Fifty-eight patients were identified as potentially eligible for the study with the inclusion process outlined in Figure 1. From these patients 43 were given a diagnosis of angioedema. Ten of these 43 patients were excluded from the study; 8 based on age criteria and the other 2 patients were diagnosed with angioedema but were excluded as no airway intervention was required. The remaining 33 patients were then divided into three groups based on the primary device used to secure the airway; (1) fiberoptic bronchoscopy (FOB; n=12), (2) videolaryngoscopy (VL; n=11) and (3) miscellaneous (n=10). Of the ten patients in the miscellaneous group, six patients had their trachea intubated via direct laryngoscopy, three with an intubating laryngeal mask airway (ILMA), and one performed with a blind nasal technique. There was no statistical difference in the mean age of all thirty-three patients. There was no statistically significant difference in the proportion of successful first intubation attempts or the total number of attempts of intubation between the three groups [Table 2]. There was a statistically significant difference in the duration of intubation time (P<0.05), with the VL group (6.9±0.9 min) and miscellaneous group (9.1±2.0 min) significantly less than that of the FOB group (10.4±0.7 min; Table 2). No complications were noted in any of the 33 patients reviewed. Thirty cases were determined to result from by ACE inhibitor therapy, while three were idiopathic.

Figure 1

Inclusion criteria for eligibility of patients in the study

Table 2

Intubation outcomes

DISCUSSION

Much has been published about angioedema regarding its epidemiology, airway risk, and demographics. Nonetheless, to date there has been no analysis of the devices/methods used to intubate the trachea in this setting. Traditionally, fiberoptic intubation of the spontaneously breathing patient has been employed for the anticipated difficult airway.[11] The last decade has seen the introduction of new devices that can be used effectively in intubating these challenging airways (GlideScope®, the Pentax AWS, Truview EVO2).[12] GlideScope® was the intubation device used in the OR suites at our institution. The advantage of its use when compared to fiberoptic is that it produces a “macro” view of the supraglottic structures. Furthermore, proficiency in fiberoptic intubation can take significantly longer then that of videolaryngoscopy.[1314] The observation that there was no statistically significant difference in the number of attempts to intubate the trachea when using either one of the devices is an indication of the utility of VL. Moreover, VL appeared a more efficient method as it required the least amount of time in establishing a safe and secured airway, which could make the difference in avoiding cardiopulmonary arrest secondary to hypoxemia.

Chiu et al., in a multicenter review proposed a staging system based on the location and severity of angioedema with the purpose to aid the clinician to make a decision whether to intubate or observe the patient.[4] This classification system describes three types of angioedema and other authors suggested possible management options [Table 3].[15] Patients presenting with type 1 and 2 angioedema are to be observed in a monitored setting. For patients presenting with a type 3 angioedema, intubation with a fiberoptic bronchoscope has been recommended as any airway manipulation to already swollen airway can exacerbate the condition, turning a type 1 airway into a type 3.[12] A patient presenting with a type 3 angioedema should have the airway secured with fiberoptic bronchoscope, however there are reports available of anesthesia providers securing this airway through other devices.[12] Table 3 outlines the angioedema classifications and recommendations.

Table 3

Classification of angioedema and suggested plans of management

While the data in our pilot study is underpowered due to its small sample size, additional numbers may give a clearer indication in cases of angioedema of when to intubate and which device to use. A published case series suggests both fiberoptic and VL could be used in combination for an awake difficult intubation.[16] Specific anatomical considerations would preclude the use of VL such as inability to insert the blade secondary to tongue and lip edema or massive edema of the pharynx that would render one unable to maneuver the device. Specifically, GlideScope® as a VL method has its own inherent risks such as uvular, soft palate, and tonsillar pillar injuries.[1718]

Other airway methods reviewed in our study included intubating LMA. In the three cases the intubating LMA was used twice as a rescue device for failed direct laryngoscopy and once as the primary method. Although in these 3 cases it was successfully used, we suggest it is not an ideal device for airway management. The distorted swelling in angioedema prevents secured seal with the intubating LMA, thus impairing ventilation.[19] One case of blind nasal intubation was successfully used in this study. In general, blind nasal intubations are used less frequently due to the popularity of VL which can provide an operator with better control. Direct laryngoscopy may still have a role in less severe (type I and II) angioedema class.

A limitation of this study was that this was a retrospective review with a small sample size. Additional numbers are needed to confirm if the significant differences between FOB and VL groups observed in this study are valid. Another major limitation was that intubations were performed by different anesthesiologists (n=10) and there was no grading system to evaluate the severity of angioedema. Also, in our study we have included only cases managed in the operating suites. This means that our study is more representative of urgent cases, not emergent variety.

CONCLUSION

Although fiberoptic and videolaryngoscopic intubation methods were similarly effective in the airway management if angioedema, videolaryngoscopy was significantly more time efficient in securing the airway. A more rapid securing of the airway during angioedema may change patient outcomes dramatically, particularly in avoiding cardiopulmonary arrest secondary to hypoxemia.