The effect of etomidate on airway management practices of an air medical transport service

FOCUS ON AIRWAY MANAGEMENT THE EFFECT

ETOMIDATE ON AIRWAY MANAGEMENT PRACTICES OF AN AIR MEDICAL TRANSPORT SERVICE

OF

Howard A. Werman, MD, David Schwegman, MD, James P. Gerard, MD intubation methods by the air medical transport crew. Etomidate significantly reduced the need for administration of paralytic agents used in an RSI. Key words: air ambulances; intubation, intratracheal; etomidate; neuromusculardepolarizing agents.

ABSTRACT Objective. The authors studied the effect of introducing etomidate on the airway management practices of their air transport crew and specifically considered the need for paralytic agents during rapid-sequence intubation. Methods. A prospective observational review of the transport records for all patients aged greater than 10 years who required intubation transported by the air medical crew before (PRE) and after (POST) the introduction of etomidate into the authors’ rapid-sequence induction protocol was conducted. Data were collected, including the method of intubation, indications for intubation, and complications from the procedure. The following outcomes were measured: the method used for intubation (nasotracheal or orotracheal), oral intubation success rate, number of attempts for oral intubation, need for paralytic agents, and complications with the procedure. Results. Comparing the PRE and POST periods, nasotracheal intubation was performed in 27 of 70 (38.6%) versus 33 of 71 (46.4%; p = 0.237997). The overall success rate for intubation in the PRE period was 67 of 70 (95.7%), with 95.3% of orotracheal intubations being successful. In the POST period, the overall success rate was 65 of 71 (91.5%), with 94.7% of orotracheal intubations being successful. Complication rates were similar between the groups. Etomidate reduced the use of paralytic agents from 46 of 62 (74.6%) of patients receiving midazolam to 10 of 22 (45.5%) intubated with etomidate (p = 0.02). Conclusions. Etomidate did not appear to have an impact on the selection of

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Airway management is the first priority in patient stabilization for air medical transport. Because of the critical nature of patients transported, air medical transport crews are often called on to establish a definitive airway using orotracheal or nasotracheal techniques as well as surgical approaches. Over the past several years, rapid-sequence intubation techniques have been introduced to air medical transport programs as a method to provide a secure airway before transport.1,2 This technique requires the use of paralytic agents, sedative drugs, and other premedications to successfully execute the intubation procedure in an emergency setting. Traditionally, sedative hypnotic agents such as midazolam and diazepam have been used as sedative agents for rapid sequence intubation (RSI). Because of their propensity to cause respiratory depression and hypotension, these agents might not be ideal for use in the critically ill or injured patient typically seen in the air medical environment. In addition, there is a wide clinical response among patients receiving sedative doses of midazolam. This limits the ability to use RSI as a method of airway management and favors more traditional approaches such as nasotracheal intubation, which are better tolerated in the conscious patient. Problems with the use of midazolam as a sedative agent had been cited by our medical crews as a barrier to performing orotracheal intubation using RSI in our transport program. Etomidate is a nonbarbiturate, nonbenzodiazepine sedative/hypnotic drug that has been used as an induction agent in many RSI protocols. The drug offers the advantage of producing little cardiovascular effects

Received March 1, 2003, from the Department of Emergency Medicine (HAW), The Ohio State University College of Medicine and Public Health, and MedFlight, Columbus, Ohio; the Department of Emergency Medicine (DS), Emory University School of Medicine, Atlanta, Georgia; and Highline Community Hospital (JPG), Burien, Washington. Revisions received September 17, 2003, and November 17, 2003; accepted for publication November 18, 2003. Presented at the National Association of EMS Physicians Annual Meeting, Tucson, Arizona, January 2002. Address correspondence and reprint requests to: Howard A. Werman, MD, Department of Emergency Medicine, 154 Means Hall, 1654 Upham Drive, Columbus, OH 43210. e-mail: . doi:10.1016/j.prehos.2003.12.012

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and minimal respiratory depression while offering cerebroprotection.3 The drug is rapid in onset, has a predicable dose–response curve, and possesses a short duration of action. One additional benefit is the ability of etomidate to produce adequate intubating conditions without the need for paralytic agents in some patients requiring emergent airway control. Several studies have documented the ability of the drug to produce intubating conditions in patients without the need for subsequent paralytic administration as part of a RSI technique.4–6 As a result of concerns about the use of midazolam in RSI, our critical care transport service recently introduced etomidate as an alternative sedative agent. This gave us an opportunity to examine the impact of introducing this medication on our airway control practices. The purposes of our investigation were 1) to examine the impact of introducing etomidate on the distribution of intubation approaches used by our air medical crew, and 2) to determine the need for administration of paralytic agents when etomidate was introduced as part of our RSI protocol.

reviewed the properties and clinical uses of etomidate and provided refresher training on the RSI technique. A written examination was completed by all crewmembers before implementation of the revised RSI protocol. It should be noted that etomidate was approved only for use as a part of the full RSI protocol but was not approved for sedation in oral or nasal intubation. Thus, the administration of etomidate demonstrated intent to perform a full RSI. A prospective review of the transport records for all medical and trauma patients greater than age 10 years transported by the air medical crew who required intubation during the study period were included in our analysis. The age of 10 years was chosen because it is at this age at which patients receive standard pharmacologic management in performing an RSI protocol. In addition, etomidate is not U.S. Food and Drug Administration-approved for use in patients less than age 10. Patients intubated after cardiac arrest were excluded from the analysis. Crewmembers exercised total discretion in choosing the intubation approach and pharmacologic adjuncts in compliance with written protocols and were blinded to the ongoing study. Each crewmember was instructed to assess the level of sedation after the administration of either midazolam or etomidate; oral intubation was attempted without paralysis as part of the RSI if the crewmember felt that appropriate conditions allowed the procedure to be performed successfully. Nasotracheal intubation was contraindicated in patients with suspected midfacial fractures and basilar skull fractures. In addition, the technique was relatively contraindicated in patients less than age 12. Data were prospectively collected on the intubation practices for our air medical transport service for ten months before the introduction of etomidate (PRE; May 1999 to January 2000) as well as six months after the drug’s introduction (POST; February 2000 to July 2000). Each crewmember was asked to complete a standard data collection tool for the analysis (see Fig. 1). Demographic information included the age and sex of the patient, the nature of the transport (medical vs. trauma), and the type of transport (scene vs. interhospital). In addition, each crewmember was asked to specify the indication for intubation. Indications included airway protection, decreased level of consciousness (Glasgow Coma Scale <9), airway obstruction, respiratory failure, or other indication. Crewmembers were free to specify several indications if they were applicable. The following outcomes were measured: the method used for intubation (nasotracheal or orotracheal), intubation success rate, number of attempts to intubation, need for paralytic agents, and complications with the procedure. An intubation attempt was defined as any attempt to place the endotracheal tube into the

METHODS MedFlight is a critical care transport service that serves central and southeast Ohio. Our service uses mobile intensive care unit, rotary-wing, and fixed-wing vehicles. Each vehicle is staffed with a critical care nurse and a field-experienced paramedic with a minimum of five years of clinical service. Each crew member must maintain current certification in advanced cardiac life support and pediatric advanced life support and have successfully completed a basic trauma life support (BTLS) or prehospital trauma life support (PHTLS) course before employment. Crews complete annual competency training in intubation techniques and our RSI protocol. In addition, the program medical director audits all intubations performed by the medical crew. MedFlight has been using RSI for intubation since its inception in 1995. The other option for intubation was blind nasotracheal. Before the study period, our RSI protocol for adults used midazolam (Versed), at a dosage of 1.0 to 2.5 mg per dose, as the sole sedative/induction agent for intubation. Midazolam was also available for use as a single sedative agent to assist in nasal intubations. Etomidate was introduced as an alternative sedative/hypnotic agent for induction as part of our RSI protocol. A protocol for confirming tube placement using both clinical criteria (vapor in endotracheal tube, presence of breath sounds, absence of gastric insufflation, and symmetric movement of the chest) and immediate application of capnometry is a routine part of the intubation procedure. Each crewmember was responsible for completing a self-study program, which

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FIGURE 1. Intubation data collection sheet. LOC = loss of consciousness; ET = endotracheal tube. oropharynx or nasal passage with intent to pass the tube through the vocal cords. For the purposes of this study, we analyzed only the initial method selected to secure the airway irrespective of the method used to successfully intubate the patient. It should be noted that a change in the method for successful intubation was noted in less than five cases in each study group. Complications were recorded for each intubation and included vomiting, aspiration, seizure activity, esophageal intubation, and the need for subsequent cricothyroidotomy. The use of oral versus nasal intubation approaches was compared between the study periods. Additionally, the use of paralytic agents as part of an RSI technique for all orotracheal attempts in which midazolam was used was compared with those patients receiving etomidate in the POST group. A two-tailed Student t-test was used to compare demographic data between the two groups. A chi-squared analysis was used to compare the change in intubation success rates between the study periods and the distribution of intubation techniques between the two periods with p < 0.05 considered to be

statistically significant. Because of the nature of the study design and the fact that no patient-specific information was reported, the institutional review board ruled that the study was exempt from review.

RESULTS One hundred forty-one patients were intubated during the study period. There were 70 intubations analyzed before introduction of etomidate (PRE) and 71 intubations after the introduction of the drug (POST). The groups were similar with respect to patient age, sex, nature of transport, and type of transport as depicted in Table 1. No patient was intubated for cardiac arrest, but two patients in the POST group sustained cardiac arrest subsequent to intubation. The results of the study are summarized in Table 2. In the PRE period, 74% were intubated to protect the airway, 79% were intubated because of a decreased level of consciousness, 9% were intubated as a result of airway obstruction, 45% for respiratory failure, and 20% of intubations were done for other unspecified

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TABLE 1. Demographic Comparison between PRE and POST Groups Percent male Average age (yr) Percent medical Percent scene response

PRE

POST

p-value

68.1 44.0 39.1 53.6

62.9 41.8 38.6 48.6

0.41 0.68 0.61 0.45

indications. In the POST period, 82% of patients were intubated for airway protection, 83% for decreased level of consciousness, 14% for airway obstruction, 32% for respiratory failure, and 20% for unspecified other causes. Because medical crews could select more than one indication for intubation, the totals for both PRE and POST groups exceeded 100%. Comparing the PRE and POST periods, nasotracheal intubation was performed in 27 of 70 (38.6%) versus 33 of 71 (46.4%) (p = 0.237997) patients. The overall success rate for intubation in the PRE period was 67 of 70 (95.7%), with 41 of 43 (95.3%) of orotracheal intubations being successful. In the POST period, the overall success rate was 65 of 71 (91.5%), with 36 of 38 (94.7%) of orotracheal intubations being successful. The average number of attempts for successful intubation was 1.46 for patients receiving midazolam and 1.64 for patients receiving etomidate. Etomidate did not improve the rate of successful orotracheal intubation; the procedure was successful in 75 of 76 (98.7%) patients with midazolam and 22 of 23 (95.7%) with etomidate (p = 0.501291). However, when used a part of an RSI, etomidate reduced the use of paralytic agents from 46 of 62 (74.6%) with midazolam to 10 of 22 (45.5%) (p = 0.02). There were no cases of missed esophageal intubation. In 15 cases, the esophagus was intubated during an unsuccessful intubation attempt. In every case, however, esophageal intubation was promptly recognized and the endotracheal tube was removed. Only one patient in the PRE group required a cricothyroidotomy after three unsuccessful orotracheal intubation and one unsuccessful nasotracheal attempts. Myoclonus was noted in only one patient (0.7%). This patient had received etomidate. Seizures were noted in three cases (2.1%); only one of these patients had received etomidate. Other complications included vomiting (10.1%) and aspiration (2.9%). There was a difference in complication rates between the PRE (13 of 70; 18.6%) and POST (23 of 71; 32.4%) periods, although this difference did not reach statistical significance.

DISCUSSION The intent of our study was to examine the effect of the introduction of a new sedative/hypnotic agent, etomidate, on the airway practices of our air medical

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TABLE 2. Results between PRE and POST Groups PRE

POST

74% 79% 9% 20%

82% 83% 14% 20%

Intubation Nasotracheal (successful) Nasotracheal (attempt) Orotracheal (successful) Orotracheal (attempt) Percent nasotracheal Percent orotracheal No. of orotracheal attempts

26 (96.3%) 27 41 (95.3) 43 38.6% 71.4% 1.42 6 0.73

29 (87.9%) 33 36 (94.7%) 38 46.4% 63.6% 1.32 6 0.65

Complications Aspiration Cricothyroidotomy Esophageal intubation Myoclonus Seizure Vomiting Total patients Total complications

2 1 5 0 2 3 8 (11.4%) 13 (18.6%)

2 0 9 1 1 10 15 (21.1%) 23 (32.4%)

Indication Protect the airway Decreased level of consciousness Airway obstruction Unspecified

transport program. During the educational phase, the benefits of this new agent, which included a predictable dose–response curve, rapid onset and duration of action, cerebroprotective properties, and limited cardiovascular effect, were emphasized.3 The benefits of this drug were contrasted to midazolam, which had been the sole sedative agent available to perform RSI. In addition, the introduction of etomidate provided the opportunity to reemphasize the RSI technique as a method of establishing a definitive airway in our transport population and to discuss disadvantages of nasotracheal intubation in long-term critical care management. Despite these efforts, we were unable to effect a change in the intubation practices of our medical crews as measured by the ratio between attempted nasotracheal and orotracheal intubations. Our results are in contrast to the findings of Swanson7 who showed that a formal airway educational program produced a demonstrable increase in the use of RSI. The authors did report a decline in the use of paralytics without sedation and a decrease in the cricothyroidotomy rate after introducing their airway training program. We chose to look at the ratio of orotracheal to nasotracheal intubations between the study periods. Our study failed to show any change in this ratio and also failed to demonstrate any change in the success rates for these procedures that were attempted after the training program. Our study did confirm that once etomidate was introduced as a sedative/hypnotic agent into our protocols that a significant decrease in the use of paralytics was noted. This effect was first reported by Plewa et al.,4 who found that when etomidate was

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used as a sedative/hypnotic agent in trauma patients, paralytic agents were required in only 30% to achieve successful intubating conditions. Migden and Reardon5 further confirmed the ability to avoid the use of paralytic agents when using etomidate in nontrauma patients. Bozeman and Young6 demonstrated that 89% of intubations could be successfully accomplished in the air transport environment using etomidate alone as a sedative agent. However, 16% of their total attempts were considered difficult to complete using only etomidate. Similarly, Kociszewski et al.8 showed that etomidate alone without paralytic agents was sufficient to produce intubating conditions in 88% of patients in their air transport patients. On the other hand, Swanson et al.9 found that etomidate was used without paralytic agents in only 21% of RSI procedures in their program. They confirmed a high intubation success rate (96%) and a low complication rate with the use of etomidate. The finding that etomidate can reduce the use of paralytic agents during intubation is significant because it has been documented that the use of succinylcholine under emergency intubating conditions significantly increases the complication rates for such procedures.10 There are several potential explanations for our lack of change in the distribution of oral and nasal intubation techniques. Although our air transport medical crews are required to have a minimum of five years of clinical experience, the majority of our providers have in excess of ten years of field and transport experience. Each has attained a level of comfort in performing certain airway maneuvers, especially nasotracheal intubations. This is confirmed by the overall success rate for nasotracheal intubation of 96.2% in the PRE period and 87.9% in the POST period. It is also possible that as experience with the sedative/hypnotic agent etomidate is gained over time that our medical crews could become more comfortable using this agent and the RSI procedure to secure an airway. In this investigation, we chose to study the time period immediately after the training program in the use of etomidate. Our assumption was that this would represent the time when the crews would be most comfortable in the use of the new protocol and thus, change their behavior. To see if intubation approaches change over time, we intend to reexamine this issue after one year of adopting this change in protocol. Our total complication rate of 18% (25 of 141) was consistent with other studies examining rapid sequence induction in the air medical environment. Sing et al.12 found intubation complications in 18% (15 of 84) of their patients. Vilke et al.11 found a complication rate of 17.8% (67 of 377) in their patients who underwent nasotracheal intubation or oral intubation using RSI. On the other hand, our complications were limited to

those mishaps identified at the time of intubation through receipt of the patient at the receiving facility. Late pulmonary complications were not considered in this study because inpatient data were not available. Additionally, the finding of myoclonus in only one patient during the study is lower than the traditional rate of 30% to 65% incidence reported in the literature,3 even if one includes two additional patients who were reported to have had ‘‘seizures’’ in this group.

LIMITATIONS There are several potential limitations with the current investigation. Some have already been discussed. This investigation used a convenience sample of ten months of historical data and six months of postintervention data to evaluate the effect of our educational intervention. We were not able to detect a significant change in the time period immediately after the introduction of etomidate. The power of this study to detect a 7.8% decline in attempted nasotracheal intubation was almost 90% for sample sizes of 70 in the PRE group and 71 in the POST group, which is below the commonly accepted level of 0.20 in most studies.13 In addition, the complications of intubation were selfreported by the crew members. It is likely that the true incidence is somewhat higher. Additionally, with no inpatient data available for each patient, we were limited in our ability to comment on clinical outcomes or long-term complications for our intubated patients such as aspiration pneumonia or pneumothorax. Finally, we were unable to separate out the effects of introducing the drug itself from the effect of an educational program emphasizing orotracheal intubation using an RSI. Thus, we were in fact studying the effects of both the benefits of the drug as well as the effects of our educational program. As a result, we chose to look not only at the distribution of oral and nasal intubation, but also at the effect on the use of paralytic agents.

CONCLUSION The addition of etomidate as an alternative sedative agent in an RSI protocol did not appear to have an impact on the airway management practices of our air medical transport crew. This could be a function of the crew’s comfort with specific airway-securing measures. The comparative use of nasotracheal and orotracheal techniques did not change between the two time periods with introduction of the drug. Etomidate did significantly reduce the need for administration of paralytic agents used in an RSI. Our intubation complication rates were low and did not change significantly with the addition of etomidate to our airway protocols. Further study is needed to determine if the use of

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etomidate over time will alter the airway management practices of an air transport program.

6. Bozeman WP, Young S. Etomidate as a sole agent for endotracheal intubation in the prehospital air medical setting. Air Med J. 2002;21:32–7. 7. Swanson ER, Fosnocht DE. Effect of an airway education program on prehospital intubation. Air Med J. 2002;21:28–31. 8. Kociszewski C, Thomas SH, Harrison T, Wedel SK. Etomidate versus succinylcholine for intubation in an air medical setting. Am J Emerg Med. 2000;18:757–63. 9. Swanson ER, Fosnocht DE, Neff RJ. The use of etomidate for rapid-sequence intubation in the air medical setting. Prehosp Emerg Care. 2001;5:142–6. 10. Orebaugh SL. Succinylcholine: adverse effects and alternatives in emergency medicine. Am J Emerg Med. 1999;17: 715–21. 11. Vilke GM, Hoyt DB, Epperson M, et al. Intubation techniques in the helicopter. J Emerg Med. 1993;12:217–24. 12. Sing RF, Rotondo MF, Zonies DH, et al. Rapid sequence induction for intubation by an aeromedical transport team: a critical analysis. Am J Emerg Med. 1998;16:598–602. 13. Brown CG, Kelen GD, Ashton JJ, Werman HA. The beta error and sample size determination in clinical trials in emergency medicine. Ann Emerg Med. 1987;16:183–7.

The authors thank Rizwan Pasha, MD, for his contribution to the manuscript.

References 1. Syverud SA, Borron SW, Storer DL, et al. Prehospital use of neuromuscular blocking agents in a helicopter ambulance program. Ann Emerg Med. 1988;6:236–42. 2. Murphy-Macabobby M, Marshall WJ, Schneider C, et al. Neuromuscular blockade in aeromedical airway management. Ann Emerg Med. 1991;21:664–8. 3. Bergen JM, Smith DC. A review of etomidate for rapid sequence intubation in the emergency department. J Emerg Med. 1997; 15:221–30. 4. Plewa MC, King R, Johnson D, Adams D. Etomidate use during emergency intubation of trauma patients. Am J Emerg Med. 1997;15:98–9. 5. Migden DR, Reardon RF. Etomidate sedation for intubation. Am J Emerg Med. 1998;16:101–2.

d

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