Ultrasound-Guided Regional Anesthesia Using a Head-Mounted Video Display: A Randomized Clinical Study
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Pain Physician 2021; 24:83-87 • ISSN 1533-3159
Randomized Clinical Study
Ultrasound-Guided Regional Anesthesia Using
a Head-Mounted Video Display: A Randomized
Clinical Study
Rene Przkora, MD, PhD1 Juan Mora, MD1, Pavel Balduyeu, MD1, Matthew Meroney, MD1,
Terrie Vasilopoulos, PhD1,2 and Daneshvari Solanki, MD3
From: 1Department of Background: Ultrasonography is increasingly being used in every field of medicine, especially regional
Anesthesiology, University anesthesia. To successfully perform the procedure, a knowledge of anatomy and ultrasonoanatomy as
of Florida College of
Medicine, Gainesville, well as technical 3D hand-eye coordination skills are required. Medical practitioners who use ultrasound
FL; 2Department of devices to perform regional blocks have to correlate the position of the ultrasound probe on the patient,
Orthopaedics and needle position, and ultrasound picture. To achieve that, the practitioner has to intermittently look between
Rehabilitation, University the patient and the ultrasonography screen. This requires extra head rotations, increasing the time and
of Florida College of
Medicine, Gainesville,
complexity of the procedure. Newer technologies are available that can alleviate the need for these extra
FL; 3Department of head movements, such as head-mounted displays (HMDs), which are connected to the ultrasonography
Anesthesiology, University machine and project the ultrasonography picture onto the HMD goggles so that the provider can see the
of Texas Medical Branch, monitor without unnecessary head rotations.
Galveston, TX
Objective: Our theory was that the use of the HMD goggles would decrease the overall procedure
Address Correspondence:
Rene Przkora, MD,
duration as well as provider head rotations.
PhD, Department of
Anesthesiology, University Study Design: This was a randomized clinical study.
of Florida College of
Medicine Setting: The research was conducted at an academic medical center at the University of Texas Medical
PO Box 100254 Branch, Galveston, TX.
Gainesville, FL 32610
E-mail: Methods: We secured Institutional Review Board (IRB) approval to perform the study. We chose an HMD,
rprzkora@anest.ufl.edu which can be mounted on the head like regular goggles. By connecting the HMD with the ultrasonography
machine, the ultrasound picture can be projected directly in front of the physician’s eyes. Twenty-four
Disclaimer: This study
was supported by patients were randomized to receive a regional anesthetic performed by anesthesiology residents using
departmental sources. a conventional ultrasound-guided approach or using the HMD in addition. We measured the number
of attempts, head rotations, and time needed to obtain a satisfactory nerve stimulation in addition to
Conflict of interest: Each outcomes and adverse effects. Our data were interpreted by our statistician with P < .05 indicating statistical
author certifies that he or
she, or a member of his or significance.
her immediate family, has
no commercial association Results: Regional anesthetics performed with the HMD were significantly faster (59.08 vs 175.08 seconds)
(i.e., consultancies, with significantly fewer head movements (0.83 vs 4.75) and attempts (1 vs 1.42). There were no significant
stock ownership, equity differences in patient demographics, type of regional anesthetic, level of resident training, or outcomes. No
interest, patent/licensing complications were noted.
arrangements, etc.) that
might pose a conflict of Limitations: A limitation of our research is that neither observers nor providers were blinded to the way
interest in connection with
the submitted manuscript. blocks were performed. This would have been practically impossible because participants had to wear an
HMD.
Manuscript received:
07-26-2019 Conclusions: The HMD could provide advantages in regional anesthesia by decreasing the time and
Revised manuscript attempts and improving ergonomics. These findings can be easily translated into other ultrasound- or optic/
received: camera-guided procedures outside of regional anesthesia, such as vascular access or laparoscopic surgery.
05-04-2020
Accepted for publication:
IRB: UTMB IRB #12-143
06-19-2020
Free full manuscript:
Key words: Head-mounted video display, nerve blocks, randomized clinical study, regional anesthesia,
www.painphysicianjournal. regional blocks, ultrasound, vascular access
com
Pain Physician 2021: 24:83-87
www.painphysicianjournal.comPain Physician: January/February 2021 24:83-87
N umerous technological advances are changing
the field of regional analgesia and anesthesia.
Ultrasound guidance during many nerve block
procedures is increasingly prevalent, and growing
evidence supports its use (1).
simulated environment could be translated to complex
clinical settings in regional anesthesia.
Methods
We secured Institutional Review Board approval at
To successfully perform this procedure, knowledge our academic medical center (University of Texas Medi-
of anatomy and ultrasonoanatomy as well as technical cal Branch) to perform the study. We pulled an enve-
3D hand-eye coordination skills are required. Medical lope to randomize 24 patients, half of whom received
practitioners who use ultrasound devices to perform a regional anesthetic performed by anesthesiology
regional blocks have to correlate the position of the residents using a conventional ultrasound-guided ap-
ultrasound probe on the patient, needle position, proach and half of whom received regional anesthetic
and ultrasound picture. To achieve that, they have to from residents using ultrasound and an HMD (Fig. 1).
intermittently look between the patient and the ultra- Anesthesia residents (CA-2) who were on their initial
sonography screen. This requires extra head rotations, regional anesthesia rotation participated. They simu-
increasing the time and complexity of the procedure. lated blocks with the Blue Phantom (5 blocks with the
Furthermore, these head rotations could distract the HMD, 5 blocks without the HMD) before using the
physician, potentially interfering with their grip on the HMD on patients.
ultrasound probe, ultimately losing the image of the Our institution purchased the HMD (Wrap Trade
target structure. Mark Video Eyewear, Vuzix Corporation, Rochester,
Newer technologies are available that can allevi- NY), which is a binocular image monitor fitted to the
ate the need for these extra head movements, such as face like regular goggles. The ultrasound machine (So-
head-mounted displays (HMDs). These devices are con- noSite, Bothell, WA; Fig. 2) image was then translated
nected to the ultrasonography machine and project the onto the HMD in front of the provider’s eyes. A 13-6
ultrasonography picture onto the HMD goggles so that MHz probe was used.
the provider can see the monitor without unnecessary We performed all regional blocks using an in-plane
head rotations between the patient and the ultraso- approach with a 21-gauge, 50-mm Stimuplex needle
nography machine (2,3). with a 30° bevel (Braun Medical Inc., Bethlehem, PA).
Our theory was that the use of HMD goggles The ultrasound machine was placed on one side of
would decrease the total procedure duration as well the patient, opposite to the provider, unless an HMD
as provider head rotations in a randomized clinical was used. In that case, the ultrasonography machine
study. We initially performed the study using the Blue was hidden behind the provider to remove a potential
Phantom (CAE Healthcare, Sarasota, FL) to simulate an distraction and the bias created by the operator’s reli-
extremity for a peripheral, ultrasound-guided nerve ance on the ultrasonography screen rather than the
block (4). We selected 20 providers with varying levels HMD image. A designated observer recorded the time
of procedural and ultrasound skills and training and from the visualization of the target nerve in the patient
instructed them to complete a regional nerve block and skin perforation until the target nerve was touched
with ultrasonography with and without the HMD. We with the needle tip, causing stimulation. Another des-
measured the number of attempts, head rotations, ignated observer measured the ultrasonography probe
and time needed to obtain a needle position. We and head rotations of the providers. The same position
analyzed the data with a t test and considered P < .05 was maintained for all providers throughout the entire
statistically significant. study. Adjustments of the ultrasonography probe (such
According to our results, providers accomplished as movement of the probe to reacquire the picture of
regional blocks faster with the HMD than without it the needle or target nerve) were noted and rotations
(7.1 vs 10.9 seconds). In addition, the HMD drasti- of the head > 45° (either rotation or extension/flexion)
cally decreased the number of ultrasonography probe were counted. We measured the number of attempts,
manipulations and head rotations. These findings head rotations, and time to acquire a satisfactory
indicated that the HMD improved the efficiency of nerve stimulation in addition to outcomes and adverse
simulated regional blocks and that clinical studies were effects.
warranted. Based on that, in our current research we We analyzed the data with a t test and considered
sought to determine if our results with the HMD in a P < .05 statistically significant.
84 www.painphysicianjournal.comUltrasound-Guided Regional Anesthesia Using HMD
Fig. 1. Flow chart of the study’s design.
Results
Regional anesthetics performed
with the HMD were delivered signifi-
cantly faster than with the conven-
tional ultrasound-guided approach (P
< .05; mean: 59.08 vs 175.08 seconds;
standard deviation [SD]: 42.46 vs
171.51; Fig. 3). There were significant-
ly fewer provider head movements
with the HMD (P < .05; mean: 0.83
vs 4.75 head movements; SD: 0.83 vs
2.30; Fig. 4) and attempts (P < .05;
mean: 1 vs 1.42 attempts; SD: 0 vs Fig. 2. Head-mounted video display lateral and frontal view.
0.52; Fig. 5). There were no significant
differences in patient demographics
(Table 1), type of regional anesthetic (Table 2), level of
resident training, or outcomes. No complications were
noted.
Discussion
The HMD could provide advantages in regional an-
esthesia by decreasing the time and number of attempts
and by improving ergonomics. These benefits can be
easily translated into other ultrasound- or optic/camera-
guided procedures performed by any ultrasonographer
outside of regional anesthesia, such as vascular access or Fig. 3. Time in seconds. Statistically significant with P <
laparoscopic surgery or radiology and cardiology. .05; data in mean and standard error of the mean.
www.painphysicianjournal.com 85Pain Physician: January/February 2021 24:83-87
Table 1. Patient demographics
No HMD HMD
Demographics
(mean ± SD) (mean ± SD)
Number of patients 12 12
Age (yrs) 55 ± 22 65 ± 10
Gender (male/female) 4 of 8 3 of 9
BMI 29 ± 8 31 ± 8
ASA class 2 2
Upper/lower extremity blocks 3 of 9 3 of 9
Abbreviations: ASA, American Society of Anesthesiologists; BMI,
body mass index; HMD, head-mounted display; SD, standard devia-
Fig. 4. Head movements. Statistically significant with P < tion.
.05; data in mean and standard error of the mean.
Table 2. Regional anesthesia demographics
Type of RA HMD Without HMD
Interscalene 2 2
Axillary 1 1
Femoral 7 5
Popliteal 2 4
Abbreviations: HMD, head-mounted display; RA, regional anesthetic
hand-eye coordination, which is supported by the fact
that these types of mistakes decrease with provider
Fig. 5. Number of attempts. Statistically significant with experience (5).
P < .05; data in mean and standard error of the mean. In our current study, we demonstrated that an HMD
of the ultrasonography image improves efficiency and
ergonomics, similar to what we demonstrated in our
Sites et al (5) used a detailed video analysis of simulated nerve block study (4). Head rotations and
performances of ultrasound-guided regional blocks ultrasonography probe adjustments were significantly
by 6 anesthesia residents during a dedicated 1-month decreased with the video goggles and the duration
rotation. They performed 520 regional blocks with of the blocks was significantly shortened compared to
398 errors committed. The 2 most common errors the classical way of performing nerve blocks. The HMD
were failure to visualize the needle before advance- could eliminate up to 40% of all mistakes observed by
ment (43.7%) and unintentional probe movement Sites et al.
(26.9%). Lack of needle visualization leads many less- A limitation of our research is that neither ob-
experienced operators to use the probe to find their servers nor providers were blinded to the way blocks
needle, which causes loss of target visualization, forc- were performed. Practically speaking, this would
ing further intentional probe movement in efforts to have been impossible because participants had to
reimage the targeted structure. Unintentional ultraso- wear an HMD.
nography probe movement is a sign of poor hand-eye We acknowledge that setting up HMD goggles by
coordination. Poor ergonomics and awkward hand connecting them with cables to the ultrasonography
position most likely contributed to the unintentional machine required some extra set-up time in the begin-
probe movement because 70% of the cases of poor ning, but this can be addressed by using wireless tech-
ergonomics also had at least one episode of uninten- nology in the future. Wireless technology could help in
tional probe movement. Altogether, up to 39.9% of using limited regional block areas in a more ergonomic
all combined errors might be related to problems with way for providers as well.
86 www.painphysicianjournal.comUltrasound-Guided Regional Anesthesia Using HMD
Author Contributions previous related work and wrote the first draft of the
Drs. Przkora and Solanki had full access to all the manuscript. Drs. Meroney, Mora, Vasilopoulos, and
data in the study and take responsibility for the integ- Balduyeu provided revision for intellectual content and
rity of the data and the accuracy of the data analysis. final approval of the manuscript.
Drs. Przkora and Solanki designed the study protocol. We would like to thank the editorial board of Pain
Drs. Przkora, Solanki, Mora, Balduyeu, and Meroney Physician for review and criticism in improving the
managed the literature searches and summaries of manuscript.
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