Clinical StudyA Shallow Angle Short-Axis Out-of-Plane ApproachReduces the Rate of Posterior Wall Injuries in Central VenousCatheterization: A Simulation Study

KunitaroWatanabe,1 Joho Tokumine ,1 Alan Kawarai Lefor,2 Akira Motoyasu ,1

KumiMoriyama ,1 and Tomoko Yorozu 1

1Department of Anesthesiology, Kyorin University School of Medicine, Tokyo, Japan2Department of Surgery, Jichi Medical University, Tochigi-ken, Japan

Correspondence should be addressed to Joho Tokumine; ii36469@wa2.so-net.ne.jp

Received 11 April 2018; Revised 18 August 2018; Accepted 27 August 2018; Published 10 September 2018

Academic Editor: Takashi Yazawa

Copyright © 2018 Kunitaro Watanabe et al. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

The short-axis out-of-plane approach (SAX-OOP) is commonly used in ultrasound-guided internal jugular vein catheterization.However, this approach has a risk of posterior vein wall injuries. The authors hypothesized that a shallow angle of approach mayreduce the rate of posterior wall injuries compared with the conventional steep angle approach.The present study aimed to evaluatewhether a difference in the angle of approach of the needle affects the rate of posterior wall injuries. The present study was arandomized crossover-controlled trial involving 40 medical residents, conducted in the clinical training center at a hospital with aresidency program.The primary outcomemeasure was the rate of posterior vessel wall injuries. Subjects received a didactic lectureduring which the instructors taught three SAX-OOP techniques including the conventional free-hand method (procedure C), aneedle navigation system (procedure N), and a shallow puncture angle using a guidance system (procedure S). Participants weretrained in these approaches under supervision and each technique tested in a simulation environment. Thirty-four of 40 residentshad no previous experience with central venous catheterization and were included in the final analysis. The rate of posterior vesselwall injuries in procedure S (9%) was significantly lower than using the other approaches (procedure C, 53%; procedure N, 41%). Inconclusion, a shallow angle of approach using the SAX-OOP technique resulted in significantly fewer posterior vein wall injuriesin central venous catheterization compared with steep angle techniques.

1. Introduction

Ultrasound-guided internal jugular vein catheterizationreduces the rate of complications compared with the anatom-ical landmark technique, although complications still occurin approximately 4% of procedures [1]. The most commonlyused technique for ultrasound-guided internal jugular veincatheterization is the short-axis out-of-plane (SAX-OOP)approach [2].This approach, however, occasionally results inposterior vein wall injury, which has a considerable risk ofinadvertent arterial injuries [3].The long-axis in-plane (LAX-IN) approach is generally associated with fewer posteriorwall injuries [4, 5]. Innovations in technology may enableus to reduce the risk for posterior wall injuries using the

SAX-OOP approach. A recent needle navigation system usedwith ultrasound imaging enables the operator to navigatethe needle trajectory and depth in real time. Auyong et al.[6] reported that this needle navigation technology yieldeda high success rate and reduced the rate of posterior wallinjuries.

We conducted a pilot study that did not result in anyimprovement in the rate of posterior wall injuries using thisneedle navigation system but did have a shorter procedureduration (Table 1). Seven residents performed ultrasound-guided central vein venipuncture in a simulation environ-ment, with and without the guidance system. Posterior wallinjuries occurred in 71% of procedures using the navigationsystem and 71% using the free-hand technique. These results

HindawiBioMed Research InternationalVolume 2018, Article ID 4793174, 5 pageshttps://doi.org/10.1155/2018/4793174

2 BioMed Research International

Table 1: Results of a previous pilot study (unpublished).

Outcome Navigationsystem

Free-handtechnique

P value(Statistical test)

Posterior vessel wall injury (%) 71 71 1.00(Fisher’s exact test)

Arterial injury (%) 0 0 1.00(T-test)

Overall success rate (%) 100 100 1.00(Fisher’s exact test)

Needle passes until success, mean ± SD 1.0 ± 0 1.1 ± 0.38 0.34(T-test)

Procedure duration (s), mean ± SD 74 ± 46 145 ± 70 0.04(T-test)

are different from those reported in the literature [6]. Furtherevaluation identified that the difference between our pilotstudy and previous results revealed that the authors used ashallow angle of approach for the needle. The pilot study weconducted used a steep angle of approach, as described inthe guidelines of the American Society of Echocardiography(ASE) & Society of Cardiovascular Anesthesiologists (SCA)[2]. Therefore, the present study aimed to evaluate whether adifference in the angle of approach of the needle affects therate of posterior wall injury.

2. Materials and Methods

The present study was reviewed and approved by the localEthics Committee of Kyorin University [Tokyo, Japan];Reception. No. 682-01) and registered in the UniversityHospitalMedical Information Network Center Clinical TrialsRegistration System (UMIN000024559, Kunitaro Watanabe,2016/10/25). Informed written consent was obtained from allparticipants. Subjects with previous experience performingcentral venous catheterization were excluded.

The study was performed using a commercially availableultrasound device (eZono4000�, eZono AG, Jena, Germany),equipped with novel, real time, and needle navigationtechnology [6]. This system enables free-hand navigationto visualize the needle trajectory and needle tip positionusing ultrasound imaging. The needle used was a 20-gauge(20G) metal introducer needle (effective length 32mm, CVLegaforce EX�, Terumo Co., Tokyo, Japan) [7].The simulatorused was developed for ultrasound-guided internal jugularvein catheterization (UGP GEL�, Alfabio Co., Japan). Thesimulated internal jugular vein and carotid artery werelocated at 11mm and 22mm from the surface. The simulatedinternal jugular vein was connected to a water server tankthrough a tube to maintain pressure at 10 cmH2O, which wasmonitored by a pressure transducer.

Forty residents were initially enrolled in the study.Study participants received a didactic lecture to explainultrasound-guided central venous catheterization. Theinstructors demonstrated how to perform three differentapproaches including the conventional free-hand SAX-OOP(procedure C) approach, the conventional SAX-OOP usingthe novel needle navigation system (procedure N), and

Figure 1: Conventional short-axis out-of-plane approach. Theneedle insertion site is close to the ultrasound probe, and the angleis adjusted to match the (simulated) internal jugular vein. Thisstandard techniquemay result in a steep angle of the needle tomatchthe internal jugular vein. Using this approach, posterior vein wallinjuries were more common and difficult to identify.

the SAX-OOP technique with a shallow angle of approachand the needle navigation system (procedure S), using asimulator.

Guidelines from the ASE and the SCA recommend thatthe needle enters the skin close to the ultrasound probe. Theangle is then adjusted to match the target internal jugularvein [2]. Following this standard technique may result in asteep angle between the needle and the internal jugular vein(Figure 1). Instructors taught the standard steep angle SAX-OOP method for procedure C and the SAX-OOP using theneedle navigation system, with the entry site close to theprobe, for procedure N. For procedure S, the needle entry siteinto the skinwas further from the probe—approximately 1 cmcephalad—resulting in a shallow angle of entry to the targetvein.The needle was inclined at approximately 30∘ to the skinin procedure S (Figure 2).

During simulation training, participants could observethe inside of the simulated vessel using an endoscope, whichis part of the simulator, and could confirmwhether the needletip was inside or outside of the vessel. Simulation trainingcontinued until participants were confident in their abilitywith the technique and were given advice by the instructor asdesired. The training did not exceed 2 h for any participant.

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Table 2: Summary of outcome measures and resident preferences.

Outcome Procedure C(Conventional)

Procedure N(Navigation)

Procedure S(Shallow angle +

navigation)Posterior vessel wall injury (%) 53 41 9Arterial injury (%) 0 0 0Overall success rate (%) 100 100 100Needle passes until success, mean ± SD 1.0 ± 0 1.0 ± 0.2 1.0 ± 0Procedure duration (s), mean ± SD 56 ± 21 43 ± 15 49 ± 18Comfort with procedure∗, median (IQR) 4 (3–4) 4 (4–5) 4 (4–5)Preferred procedure (%) 3 41 56∗Scored according to a Likert scale (1-5 [5 is best]). IQR, interquartile range.

Figure 2: Short-axis out-of-plane approach with shallow angle ofentry using a needle navigation system. The needle enters the skinfurther from the probe, approximately 1 cm cephalad, which allowsfor a shallow angle of entry toward the simulated internal jugularvein. The needle is inclined at approximately 30∘ to the target vein.

After simulation training, a test was conducted using eachapproach. All participants performed all three approaches inthe test. The endoscopic view inside of the simulated vesselwas no longer visible to the participants but was recordedduring the test. The video recordings were sequentially num-bered. The video numbers were later randomized by com-puter to assure anonymity.The technique used and individualidentification were concealed for the evaluation. Two seniorphysicians, who did not participate in the test, observed therecorded videos and evaluated whether the procedure wasperformed successfully and whether a posterior wall injuryoccurred.

This was a randomized crossover-controlled trial. Thesequence for each participant to perform each techniquewas randomly decided using a random number table. Theprimary outcomemeasurewas the rate of posterior vessel wallinjuries. Secondary outcomes include success rate, needlepasses until success, procedure duration, and unanticipatedarterial injury. Aquestionnairewas completed by participantsto assess their comfort with the procedures using a 5-pointLikert scale (5 = very comfortable, 1 = not at all comfortable)and their preferences in clinical practice.

3. Statistical Analysis

There are no studies which compare different punctureangles. The method described by Auyong et al. used aslightly shallower insertion angle compared to the ASE andSCA recommended technique [6]. We performed a poweranalysis to determine an order of magnitude result.The studyreported by Auyong et al. found the incidence of posteriorvessel wall puncture without and with needle navigation tobe 49% and 13%, respectively [6]. The sample size requiredfor 80% power at � = 0.05 was estimated to be 31 participants.In this study, we included 40 residents to guard against drop-outs and exclusions.

Fisher’s exact test was used to evaluate the rate ofposterior wall puncture, rate of arterial puncture, successrate, and Likert scale scores. Analysis of variance and Bonfer-roni correction were used to compare continuous variables.Numerical values were expressed as percentages (%) or asmean ± standard deviation for normally distributed variablesandmedian (interquartile range) for nonnormally distributedvariables. A p value < 0.05 was considered to be statisticallysignificant. Statistical analyses were performed using EZRusing R commander, version 1.32 (Saitama Medical Center,Jichi Medical University, Saitama, Japan) [8].

4. Results

Thirty-four residents were enrolled in the study (six of the40 originally recruited residents had previously performedcentral venous catheterization andwere, therefore, excluded).A summary of outcome measures and resident preferencesis presented in Table 2. The rate of posterior vessel wallpuncture for procedure S (9%) was significantly lower thanthe other two procedures (p < 0.01).There was no statisticallysignificant difference between procedures C (53%) and N(41%).

There was a statistically significant difference in proce-dure duration among the three procedures (p = 0.02). Theduration for procedure N (43 ± 15 s) was shorter than forprocedure C (56 ± 21 s) (p = 0.01). The clinical relevance ofthis difference (<10s) is marginal. There was no differencebetween procedures S (49 ± 18) and C. There was nodifference in the number of needle passes among the three

4 BioMed Research International

procedures (p = 0.37). There were no arterial injuries in anyof the three procedures, and all had a 100% success rate.

Comfort with performing procedure N was significantlyhigher than for procedure C (p = 0.02). There was nosignificant difference in comfort with the procedure betweenprocedures S and C (p = 0.1) or procedures N and S (p = 1.0).The preferred procedure in clinical practice assessed by thesurvey after the study was significantly the highest for theshallow angle SAX-OOP (procedure S) approach (56%).

5. Discussion

The conventional SAX-OOP approach has a risk of posteriorvein wall injury. The present study shows that this risk is notdue to the SAX-OOP approach itself, but rather to the steepangle of needle insertion. If the angle of approach is decreasedfrom 60∘ to 30∘, the calculated needle trajectory path fromthe anterior wall to the posterior wall is approximately 1.7times longer. This may explain why a shallow angle reducesthe rate of posterior wall injury. The reduced rate of posteriorwall injuries may also be related to needle handling skillduring ultrasound guidance. Experts performing ultrasound-guided central venous catheterizationmay stop advancing theneedle when the needle tip enters the ultrasound beam, whilenovice operators usually do not stop at that point. Expertsdo not sense a risk using a steep angle of approach and haveadequate skill handling the needle. The conventional steepangle of insertion has the benefit of easily advancing theneedle directly to the target vein because the needle entry siteinto the skin is close to the ultrasound beam. However, theconventional steep angle used in the SAX-OOP approach hasthe drawback of a higher rate of posterior wall injuries.

Both the LAX-IN and oblique approaches usually requirea shallow angle of approach, whichmay partially explain whythese approaches are not usually associated with posteriorwall injuries [9–11]. The LAX-IN approach is difficult to usefor internal jugular vein catheterization due to limitationsrelated to manipulating the ultrasound probe on the neck. Asmall-footprint probe is required to use the LAX-IN approachin smaller adult patients. Performing the LAX-IN approachalso requires precise scanning skills to place the probe onthe longitudinal center-line to prevent anterior wall to lateralwall injuries [12]. Advancing the needle within the ultrasoundbeam requires skilled hands. The medial oblique approach isan alternative option to prevent posterior wall injuries. Thisalso requires a highly experienced operator to advance theneedle within the ultrasound beam [13].

As mentioned, the needle trajectory path from the ante-rior to the posterior wall will be longer when the angle ofapproach is shallower, which follows from simple geometricconsiderations. This simple calculation may be affected bydilation of the internal jugular vein with patients in theTrendelenburg position and/or during a Valsalva maneuver,or constriction of the vein with dehydration and/or decreasedcirculating volume. Needle size may also be a factor becausea smaller-gauge needle can penetrate the anterior vein wallmore easily than a larger needle andmay be helpful to preventposterior vein wall injuries. We recommend using a <20Gneedle to reduce the rate of posterior wall injuries.

A shallow angle of approach of the needle reduces the rateof posterior wall injuries and requires the skin entry site to befurther from the ultrasound probe. However, this increaseddistance may be associated with risk. Operators can use ashallow angle of insertion while still using the conventionalsteep angle approach. This technique is simple: the operatorbegins with the conventional approach and alters the anglefrom steep to shallowwhen the needle tip reaches the anteriorvein wall.

6. Conclusions

This study demonstrates that the increased number ofposterior vein wall injuries associated with the SAX-OOPapproach is due to the relatively steep angle of approach. Ashallow angle of approach resulted in fewer posterior veinwall injuries. This procedural complication is not limited tothe SAX-OOP technique. Further innovations to limit thiscomplication are anticipated.

Data Availability

Data are available in Supplementary Materials.

Disclosure

This work was performed in Kyorin University School ofMedicine, 6-20-2 Sinkawa, Mitaka, Tokyo 181-8611, Japan.

Conflicts of Interest

Dr. Tokumine is a technical adviser to the Nippon CovidienCo. (Japan) and has conducted an ultrasound-guided tech-nical training course for that company. The other authorsdeclare that they have no conflicts of interest.

Acknowledgments

The authors thank the junior residents of Kyorin UniversityHospital for their participation in the study. This study wassupported by a research grant from Terumo Co., Tokyo,Japan.

Supplementary Materials

Supplementary files include raw data of this research, whichare demographic data of the participants, data of outcomesin each procedure types, and answers to the postseminarquestionnaire. (Supplementary Materials)

References

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[2] C. A. Troianos, G. S. Hartman, K. E. Glas et al., “Guidelines forperforming ultrasound guided vascular cannulation,” Anesthe-sia & Analgesia, vol. 114, no. 1, pp. 46–72, 2012.

[3] M. Blaivas and S. Adhikari, “An unseen danger: Frequency ofposterior vessel wall penetration by needles during attempts toplace internal jugular vein central catheters using ultrasoundguidance,” Critical Care Medicine, vol. 37, no. 8, pp. 2345–2349,2009.

[4] M. B. Stone, C. Moon, D. Sutijono, and M. Blaivas, “Needle tipvisualization during ultrasound-guided vascular access: short-axis vs long-axis approach,”TheAmerican Journal of EmergencyMedicine, vol. 28, no. 3, pp. 343–347, 2010.

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[6] D. B. Auyong, S. C. Yuan, A. N. Rymer, C. L. Green, and N.A. Hanson, “A randomized crossover study comparing a novelneedle guidance technology for simulated internal jugular veincannulation,” Anesthesiology, vol. 123, no. 3, pp. 535–541, 2015.

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[13] M. Batllori,M. Urra, E. Uriarte et al., “Randomized comparisonof three transducer orientation approaches for ultrasoundguided internal jugular venous cannulation,” British Journal ofAnaesthesia, vol. 116, no. 3, pp. 370–376, 2016.

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