Article

Effects of videolaryngoscopes on cognitive workload during tracheal intubation performed by emergency residents

Correspondence / American Journal of Emergency Medicine 37 (2019) 1963-1988 1973

have found D50W to be more readily available in resuscitation situations. Emergency department staff may be more familiar with D50W than D10W or D25W. While several studies evalu- ate the use of D10W for patients of all ages in the prehospital setting [6,7], D50W continues to be the most common formula-

tion used to treat hypoglycemia in adults in U.S. emergency

https://doi.org/10.1016/j.ajem.2019.03.054

References

30 March 2019

departments. Unlike D50W and D25W, premixed syringes of D10W are not commercially produced, so D10W must be infused from a bag or withdrawn from the bag in order to be administered.

The following technique allows for the creation of any dextrose concentration lower than 50% from D50W, and the resulting mix- ture is ready for push infusion from a 60 mL syringe. Gather a D50W ampule or vial, a 60 mL luer-lock syringe, an 18 gauge nee- dle or a transfer device, and enough sterile water to dilute the mix- ture. Draw up an amount of D50W in the 60 mL syringe that matches the desired concentration of dextrose. For example, draw up 10 mL to create D10W, and 25 mL to create D25W. The D50W may be drawn into the 60 mL syringe either directly with an 18 gauge needle, or by using a transfer device (Fig. 1). Dilute the mix- ture to 50 mL total volume with sterile water, label appropriately, and mix by inverting the syringe and then turning it upright sev- eral times. Some 60 mL syringe manufacturers place a circle around the 50 mL marker, which can serve as a memory aid. The operator can potentially make any concentration of dextrose lower than 50% using this technique. As an example, 12.5 mL of D50W diluted to 50 mL with 37.5 mL of sterile water would create D12.5W. The most useful dextrose concentrations to an EP, how- ever, are D10W and D25W. The final volume of 50 mL will often allow for additional boluses as needed. Used in conjunction with the ”rule of 50″, this technique allows for treatment of hypo- glycemia at any age (Fig. 2).

If sterile water is unavailable, normal saline can be used to

dilute the D50. In the case of dilution to D10, this will be 1 part D50W (osmolarity 2552 mOsm/L) and 4 parts normal saline (osmolarity 308 mOsm/L). The osmolarity of this mixture will be 757 mOsm/L [(4 x 308 + 2552) / 5], which is higher than D10W (505 mOsm/L) but still lower than the recommended maximum osmolarity for a pediatric peripheral infusion. The additional sodium and chloride would also need to be considered in the con- text of the resuscitation.

We created a video demonstration of the technique and uploaded it to YouTube (https://youtu.be/CdArekqU2u4).

In the future, D10W may gain wide acceptance for hypo- glycemia treatment at all ages in the United States, simplifying treatment. This transition occurred in the United Kingdom in the early 2000s and has been advocated for in Australia [6,7]. Until the United States adopts this practice, our technique offers a straightforward means to dilute dextrose by hand. For EPs working in emergency departments that do not have D25W and D10W readily available, this technique may be used to rapidly create these concentrations in order to treat pediatric hypoglycemia.

Timothy P. Young * Caitlin S. Borkowski Rhiannon N. Main Heather M. Kuntz

Loma Linda University Medical Simulation Center, Loma Linda, CA, USA Department of Emergency Medicine, Loma Linda University Medical

Center, Loma Linda, CA, USA

* Corresponding author at: Department of Emergency Medicine, Loma Linda University Medical Center, 11234 Anderson Street, A-

108, Loma Linda, CA 92354, USA.

E-mail address: [email protected] (T.P. Young)

Boullata JI, Gilbert K, Sacks G, Labossiere RJ, Crill C, Goday P, et al. A.S.P.E.N. clinical guidelines: parenteral nutrition ordering, order review, compounding, labeling, and dispensing. JPEN J Parenter Enteral Nutr 2014;38:334-77.
  • Dugan S, Le J, Jew RK. Maximum tolerated osmolarity for peripheral administration of parenteral nutrition in pediatric patients. JPEN J Parenter Enteral Nutr 2014;38:847-51.
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  • Remick K, Gausche-Hill M, Joseph MM, Brown K, Snow SK, Wright JL, et al. Pediatric readiness in the emergency department. Ann Emerg Med 2018;72: e123-36.
  • Guidelines for Care of Children in the Emergency Department. https://www. aap.org/en-us/Documents/Checklist-Guidelines_for_Care_of_Children.pdf (accessed January 25, 2019).
  • Moore C, Woollard M. Dextrose 10% or 50% in the treatment of hypoglycaemia out of hospital? A randomised controlled trial. Emerg Med J 2005;22:512-5.
  • Nehme Z, Cudini D. A review of the efficacy of 10% dextrose as an alternative to high concentration glucose in the treatment of out-of-hospital hypoglycaemia. Australas. J. Paramedicine 2009;7. https://doi.org/10.33151/ajp.7.3.177.
  • Effects of videolaryngoscopes on cognitive workload during tracheal intubation performed by emergency residents

    Tracheal intubation using direct laryngoscopy (DL) is the gold standard for airway management during resuscitation of severely ill patients [1]. The procedure may be challenging even for experi- enced physicians. In prehospital settings, tracheal intubation may be even more difficult considering unfavorable conditions such as poor or bright light, narrow space, and uncomfortable position of rescuers [2]. Lack of practice by emergency physicians due to the small number of procedures performed each year adds to the difficulty [3]. These two additional factors may be associated with lower success rates [4] and worse outcomes [5].

    Videolaryngoscopes (VL) are devices developed to address the difficulties associated with tracheal intubation [6]. VLs provide indirect view of upper airway using optical or video camera tech- nology, thereby improving glottis visualization compared to DL [7], but have not been associated with better first attempt success rate or shorter time for tracheal intubation when performed by experi- enced physicians [8]. Besides technical performance, usability is an important factor that may be associated with tracheal intubation failure [9] that can be assessed using cognitive workload. Cognitive workload is defined as the level of overall effort expended by indi- viduals in response to a task and is closely related to the usability of devices having been developed to fulfill this task. High cognitive workload is associated with greater number of Medical errors and worse outcomes [9]. We hypothesized that VL use could be helpful for emergency novices by reducing cognitive workload during challenging tracheal intubation.

    In an experimental study, two VLs (APA [BD Carefusion, USA] and AT [Vygon, France]) were compared to DL in a randomized order through two consecutive simulated situations (easy and pre- hospital scenarios). Emergency residents with little experience in tracheal intubation were enrolled in the study. They attended the- oretical and practical training courses prior to inclusion.

    The easy scenario was conducted using fresh cadavers with good laryngeal visibility on DL installed in supine position on a dis- section table in a room with sufficient luminosity. The prehospital

    1974 Correspondence / American Journal of Emergency Medicine 37 (2019) 1963-1988

    Table 1

    Usability assessment according to situation and device used.

    Usability scales

    Direct laryngoscopy

    Airtraq

    p-Valuea

    APA

    p-Valuea

    Easy airway scenario

    TLX

    54 [38-71]

    62 [48-75]

    0.10

    54 [43-65]

    0.57

    Mental WL

    8 [5-16]

    13 [7-21]

    0.31

    11 [5-14]

    0.47

    Physical WL

    3 [0-7]

    4 [2-9]

    <0.001

    2 [0-4]

    0.39

    Temporal WL

    13 [11-24]

    16 [13–21]

    0.83

    13 [7-16]

    0.30

    Performance

    9 [5-13]

    8 [5-13]

    0.44

    8 [3-16]

    0.39

    Effort

    3 [0-4.5]

    6.3 [4-12]

    0.004

    3 [1–12]

    0.073

    Frustration

    6 [0-15]

    0 [0–20]

    0.94

    1 [0-7]

    0.061

    Perceived difficulty

    3 [2-5]

    5 [4-7]

    0.005

    5 [3-7]

    0.076

    Prehospital scenario

    TLX

    81 [62-87]

    33 [30-45]

    0.005

    48 [31-66]

    0.008

    Mental WL

    5 [0-9]

    5 [2–10]

    0.94

    4 [3-14]

    0.43

    Physical WL

    15 [5-25]

    2 [1-5]

    0.005

    1 [0-4]

    0.003

    Temporal WL

    13 [7-17]

    12 [8-16]

    0.64

    16 [9-21]

    0.43

    Performance

    9 [6-13]

    6 [4-10]

    0.21

    9 [5-17]

    1

    Effort

    18 [12–23]

    3 [2-8]

    0.004

    5 [2-10]

    0.007

    Frustration

    11 [0-20]

    1 [0-9]

    0.28

    1 [0-5]

    0.037

    Perceived difficulty

    8 [6-10]

    4 [3-6]

    0.011

    5 [2-7]

    0.012

    Data are expressed as median and first and third interquartile or in population and proportion. Perceived difficulty was assessed according to a Likert-scale ranging from 0 (no difficulty) to 10 (high difficulty). NASA-TLX dimensions were rated using a Likert-type scale ranging from 0 (low level) to 100 (high level) except for performance ranging from 0 (high performance) to 100 (low performance) and secondly weighting by letting the subjects compare them pairwise, based on their perceived importance. The sum of the weighted ratings is used to obtain the TLX. APA – Carefusion APA videolaryngoscope; TLX – Task Load Index; WL – Workload. Data in italics shown the significative p- value.

    a Comparison against direct laryngoscopy.

    scenario was conducted using one high-fidelity manikin (Sim- man3G, Laerdal, Stavanger, Norway), installed in supine position on the floor, in a small room with poor ambient light.

    We used tracheal tubes with 7.5-mm internal diameter, size 4 Macintoch Blade and size 4 difficult intubation blade for APA and AT. Students had 180 s to succeed in each tracheal intubation. The main endpoint was cognitive workload measured using NASA-TLX previously described [10,11]. Secondary endpoints were glottis visualization using the Cormack-Lehane scale [12], success rate and time to successful intubation split into three sequences (vocal cord exposure, tracheal tube insertion, cuff inflation).

    A total of 73 sequences were recorded in easy scenario (LD, n = 25; AT, n = 23; APA, n = 25) and 78 in prehospital scenario (LD, n = 26; AT, n = 26; APA, n = 26) for a total of 151 tracheal intubations.

    In Easy scenario, TLX were similar between DL and AT or APA use (Table 1). Cormack-Lehane scale was similar between DL and both VLs (Table 2). Tracheal intubation success rate was comparable and time to successful tracheal intubation was shorter with DL than AT or APA use. With VLs, participants mentioned difficulties in advancing tracheal tube due to a hitch against arythenoids and removing the blade after tracheal intubation.

    In Prehospital scenario, TLX values were higher with DL than Airtraq or APA. Glottis visualization was better with both VLs com- pared to DL (Table 2). Tracheal intubation success rate was similar between DL and each VL and time to successful intubation was higher with DL than AT but similar with APA.

    In this simulation trial, VLs neither reduced cognitive workload nor improved intubation success rate in the easy scenario. Partici-

    Table 2

    Time necessary to perform successful intubation and glottis visualization according to the devices.

    Direct laryngoscopy

    Airtraq

    p-Valuea

    APA

    p-Valuea

    Easy airway scenario

    Intubation step N; time in s

    Vocal cords exposure

    25; 12 [6-14]

    23; 12 [6-22]

    0.36

    25; 12 [6-24]

    0.48

    Tube insertion

    25; 7 [5-17]

    22; 9 [7-54]

    0.13

    21; 13 [6-35]

    0.13

    Cuff inflation

    25; 9 [6-10]

    22; 12 [6-16]

    0.18

    21; 12 [8-15]

    0.036

    Total time for success

    25; 32 [20-41]

    22; 43 [30-96]

    0.019

    21; 46 [42-57]

    0.002

    Cormack class

    N = 25

    N = 23

    N = 25

    I

    19 (79)

    17 (75)

    1

    13 (54)

    0.19

    II

    5 (21)

    5 (21)

    8 (33)

    III

    0 (0)

    1 (4)

    2 (8)

    IV

    0 (0)

    0 (0)

    1 (4)

    Prehospital scenario Intubation step N; time in sec

    Vocal cords exposure

    26; 16 [10–30]

    26; 7 [3-17]

    0.002

    26; 5 [3–12]

    <0.001

    Tube insertion

    18; 14 [10-36]

    24; 7 [4-12]

    <0.001

    20; 5 [3–10]

    <0.001

    Cuff inflation

    18; 6 [5-12]

    24; 8 [6-12]

    0.09

    20; 8 [4-13]

    0.71

    Total time for success, in s

    18; 31 [60-112]

    24; 24 [18-35]

    0.001

    20; 26 [14-37]

    0.11

    Cormack class

    N = 24

    N = 24

    N = 24

    I

    6 (25)

    18 (75)

    <0.001

    8 (33.3)

    0.009

    II

    4 (16.7)

    6 (25)

    12 (50)

    III

    8 (33.3)

    0 (0)

    4 (16.7)

    IV

    6 (25)

    0 (0)

    0 (0)

    Data are expressed as number of values, median [interquartile range] or number (proportion). Vocal cord exposure, tube insertion, cuff inflation represented data of participants who succeeded in performing the step. Total time represented data of all participants. In case of failure, total time was set at 180 s. The Cormack class was assessed for only 24 of the participants in the prehospital scenario.

    APA – Carefusion APA videolaryngoscope; TLX – Task Load Index; WL – Workload; PH – Prehospital; EA – Easy Airway. Data in italics shown the significative p-value.

    a Comparison with direct laryngoscopy.

    Correspondence / American Journal of Emergency Medicine 37 (2019) 1963-1988 1975

    pants mentioned difficulties in advancing tracheal tube due to a hitch against arytenoids, as previously reported [13].

    By contrast, VLs reduced cognitive workload in the prehospital scenario. Although the use of VLs was not associated with better success rate or a lower tracheal intubation time, cognitive work- load assessment suggested easier conditions for tracheal intuba- tion performed by novices. VLs can be useful because the acute angle of a VL blade allows direct visualization of the glottis regard- less of the position of the rescuers or of the patient’s head [7]. A difficult intubation in prehospital settings differed from anesthesia definition [2]. Patient on the floor is an independent predictor of difficult intubation, because this position requires changes in res- cuers position and patients’ head, both impeding vision of the glot- tis [14].

    Our main limit is that we used Simulated models instead of real patients. However, fresh cadavers and high-fidelity manikins are known to closely simulate real conditions and are considered as good alternatives [15]. Moreover, it would not be ethical to con- duct this study in living patients.

    To conclude, VLs may be helpful for novices during tracheal intubation in difficult prehospital settings.

    Authors contribution statements

    NM conceived the study. NM, JGue, JGui and MD recorded data. OM and JPR supervised the study. NM performed statistical analy- sis. NM and JGue wrote the manuscript with support from OM. All authors discussed the results and contributed to the final manu- script. All authors approved the final manuscript.

    Ethics approval statements

    Not applicable.

    Clinical trial registration

    Not applicable.

    Funding statement

    None.

    Competings interest

    None declared.

    Acknowledgment

    The authors acknowledge all donators of a whole body after death for education and research. The authors wish to thank Jeffrey Arsham, an American medical translator, for reviewing and editing our original English-language manuscript. Carefusion France pro- vided the devices required to perform the study.

    Nicolas Marjanovic, MD

    Emergency Department and Prehospital Care, University Hospital of

    Poitiers, Poitiers, France ABS-Lab – Anatomy Biomechanics and Simulation Laboratory, University of Poitiers, School of Medicine, France Corresponding author at: Emergency Department, University Hospital of Poitiers, 86000 Poitiers, France.

    E-mail address: [email protected]

    Julien Guilbot MD Olivier Mimoz MD, PhD

    ABS-Lab – Anatomy Biomechanics and Simulation Laboratory, Univer-

    sity of Poitiers, School of Medicine, France

    Jean-Pierre Richer MD, PhDcb

    Digestive and Endocrinological Surgery Department, University Hospital

    of Poitiers, Poitiers, France ABS-Lab – Anatomy Biomechanics and Simulation Laboratory, University of Poitiers, School of Medicine, France

    Marie Dubocage MD

    Emergency Department and Prehospital Care, University Hospital of

    Poitiers, Poitiers, France University of Poitiers, School of Medicine, France

    Jeremy Guenezan, MD

    Emergency Department and Prehospital Care, University Hospital of

    Poitiers, Poitiers, France ABS-Lab – Anatomy Biomechanics and Simulation Laboratory, Univer-

    sity of Poitiers, School of Medicine, France

    22 March 2019

    https://doi.org/10.1016/j.ajem.2019.04.002

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