Ultrasonographic assessment of altered anatomical relationship between internal jugular vein and common carotid artery with supraglottic airway in children: LMA vs i-gel™.

BACKGROUND AND AIMS: Use of ultrasound (US) during internal jugular vein (IJV) cannulation reduces the risk of associated complications in children under general anaesthesia. We studied the effect of two varieties of supraglottic airway device (SGAD), the Ambu AuraOnce™ LMA (Ambu LMA), and i-gel™ on the anatomical relationship between IJV and common carotid artery (CCA). Both these SGAD are known to have similar safety profile in paediatric age group.
METHODS: A total of 62 children were randomly allocated into 2 groups. In group L: Ambu AuraOnce™ LMA (Ambu LMA) and in group I: i-gel™ was inserted. After induction of GA, US images were taken with head in neutral and 30 degrees rotated to the opposite side both before and after insertion of SGAD. The relationship between IJV and CCA was noted as lateral, anterolateral, and anterior. Degree of overlap between the two vessels was also noted.
RESULTS: Lateral rotation of the head significantly alters the relationship between the IJV and CCA and also increases the degree of overlap between them. Though these changes were noted to be similar with both varieties of SGAD, but between the two varieties of SGAD, these changes were significantly higher in group I.
CONCLUSION: Higher oesophageal sealing pressure exerted by i-gel™ as compared to other SGAD might cause increased distortion of the surrounding soft tissue leading to altered anatomical relationship between IJV and CCA, which makes the CCA vulnerable to puncture during IJV cannulation using landmark technique.

INTRODUCTION

In children, the internal jugular vein (IJV) is often cannulated for central venous access. Evidence suggests that use of the real time ultrasound (US) scanning improves the safety and accuracy of IJV cannulation.[123456]

In the paediatric population general anaesthesia (GA) is required for IJV cannulation, and supraglottic airway device (SGAD) is safely used for maintaining the airway in anaesthetised children.[78] However, insertion of the SGAD may lead to complications while puncturing the IJV.[910] There are studies showing alteration in the relationship between IJV and common carotid artery (CCA) after insertion of SGAD[1112] making the IJV puncture difficult and prone to complications, whereas another study done in paediatric population does not validate these findings.[13]

The effect of i-gel™ insertion on changing the relative anatomy between IJV and CCA has not been studied. The i-gel™ is a second generation SGAD with a prefixed non-inflatable cuff. The aim of our study was to compare the degree of overlap between right IJV and CCA between two SGADs: Ambu AuraOnce™ LMA (Ambu LMA) (Ambu A/S, Ballerup, Denmark) which is a single use SGAD with a prefixed curvature versus i-gel™ (Intersurgical Ltd., Wokingham, Berkshire, United Kingdom), in children with the head in neutral position and with 30 degrees rotation to the left side, both prior to and after the insertion of SGAD.

METHODS

The protocol was approved by the Institutional Ethics Committee with reference no EC/TMC/24/14. The written informed consent was taken from the parents. A total number of 62 children between the age group of 1 to12 years (American Society of Anesthesiologists physical status I or II) requiring IJV cannulation for chemoport insertion under GA were included for this prospective randomised study. Children with known or suspected anatomic abnormalities of neck and thorax, mediastinal mass, superior vena cava syndrome and history of previous IJV cannulation and also parents of those who were not willing to participate in the study were excluded from this study.

The children were randomised through computer generated simple randomization into 2 groups (31 children in each group) as per the SGAD chosen. In group L: Ambu AuraOnce™ LMA (Ambu LMA) was inserted as the SGAD whereas in group I: i-gel™ was inserted after induction of anaesthesia. The cuff pressure in group L was kept below 30 cm of water and none of the patients required more cuff pressure to prevent significant leak. After induction of anaesthesia, with the child breathing spontaneously, and positioned in 15 degrees Trendelenburg position, ultrasound images of the neck were taken at the level of the cricoid cartilage in following positions before and after insertion of SGA in both the groups:

P1 (Before insertion of SGAD): head in neutral position

P2 (after insertion of SGAD): head in neutral position

P3 (Before insertion of SGAD): head rotated 30 degrees to the left side

P4 (After insertion of SGAD): head rotated 30 degreess to the left side.

A 6-13 MHz linear array probe (GE Logiq-e portable ultrasound machine), was used to visualise the relevant structures and the images were stored in the US machine. Single investigator blinded to the type of SGAD inserted took following measurements from the stored images.

Relationship between IJV and CCA noted as lateral (R1), anterolateral (R2) and anterior (R3) [Figure 1]

Figure 1

Relationship between IJV and CCA. CCA: Common Carotid Artery. IJV: Internal Jugular Vein. R1: Lateral. R2: Anterolateral. R3: Anterior

Common carotid artery diameter (CCAD) in cm

Degree of overlap (DO) between IJV and CCA. DO was calculated as ratio of the overlapping length of the IJV to the horizontal diameter of the CCA and expressed in percentage [Figure 2].

Figure 2

Degree of overlap (DO) between IJV and CCA. CCAD: Common Carotid Artery Diameter. IJV: Internal Jugular Vein. DO: Degree of overlap

RESULTS

All the data were analyzed using software SAS 9.3 (Copyright © 2011, SAS Institute Inc., Cary, NC, USA). The total number of patients recruited to this study was 62. Overall three patients from group L were withdrawn after recruitment. In two patients there were technical errors with the stored images and in one patient it was found to have intrathoracic mass after induction of general anaesthesia. So, the data of 59 patients were considered for statistical analysis. Demographic details are given in Table 1.

Table 1

Demographics

Demographics (mean)	Group L (n=28)	Group I (n=31)
Age in years (SD)	5.48 (3.8)	4.94 (2.49)
Height in cm (SD)	109.57 (18.86)	105.77 (16.94)
Weight in kg (SD)	20.35 (9.08)	19.12 (8.96)
Gender (Male:Female)	21:7	22:9

Age, height and weight and gender were comparable and no statistical difference was noted between both the groups.

It was observed in our study that prior to insertion of any SGAD only the turning of the head from supine (P1) to 30 degree lateral (P3) changes the relative anatomy between IJV and CCA from R1 to R2/R3 in 32% of the patients. This change was found to be significant (P < 0.01).

Insertion of SGAD with head in neutral position (P3) changed the relationship from R1 to R2 in 18% of the patients in group L (none observed the changes from R1 to R3), whereas the change noted in group I was 32% (10% R1 to R2, and 22% from R1 to R3). This change in relative anatomy was statistically significant in both the groups (P < 0.01) [Figure 3].

Figure 3

Change in relative anatomy in two groups. Gp-L/P3: Group-L in P3 position. Gp-I/P3: Group- I in P3 position. Gp-L/P4: Group-L in P4 position. Gp-I/P4: Group- I in P4 position

When the head was turned lateral with SGAD in situ (P4), the CCA became complete anterior from anterolateral in 7% patients in group L, and in 51% of the patients in group I, statistically significant (P < 0.01) in both the groups [Figure 3].

Though, it was observed that lateral turning of the head changes the relative anatomy between IJV and CCA, but after insertion of SGAD, these changes were higher in group I as compared to that of group L both in neutral and head lateral positions (32%vs 18% and 51% vs. 7% respectively.

Degree of overlap increased significantly (P value = 0.01), when the head was turned lateral before inserting any of the two SGAD. After inserting the SGAD, DO increased by 8% in group L and 35% in group I with head in neutral position (P3), statistically significant (P < 0.01). With SGAD in situ when head was rotated 30 degrees (P4) the DO increased by 6% in group L and 33% in group I. This change in DO between two groups were also found to be statistically significant (P < 0.01) [Figure 4].

Figure 4

Degree of Overlap (%). P1 (Before insertion of SGAD): head in neutral position. P2 (after insertion of SGAD): head in neutral position. P3 (Before insertion of SGAD): head rotated 30 degree to the left side. P4 (After insertion of SGAD): head rotated 30 degrees to the left side

DISCUSSION

In paediatric population, IJV cannulation for chemoport insertion requires general anaesthesia and SGAD is considered safe for administering GA in children.[78] Both Ambu AuraOnce™ LMA (Ambu LMA) and i-gel™ have been used in children with similar safety profile.[14]

There are numerous studies which do not recommend the rotation of the head as it changes the relative anatomy between IJV and CCA making the CCA prone to puncture during IJV cannulation.[1516] We also observed that turning of the head to the opposite side not only changes the relative anatomy between the two vessels but also increases the degree of overlap between the two.

We noted that insertion of both types of SGAD significantly changes the relative anatomy between IJV and CCA and also increases the degree of overlap between the two. These changes make the CCA vulnerable to puncture while accessing the IJV during landmark technique.

Takeyama et al.[11] demonstrated that there is increased overlapping between right IJV and CCA in adults after laryngeal mask airway-Classic placement. In their study, measurement was done at three levels-high, mid and low level with the head rotated 30 degrees to the left. Nagaraja et al.[12] showed change in relative position between IJV and CCA after laryngeal mask airway placement in 8.3% of patients. The head was kept neutral and the measurements were taken before and after placement of laryngeal mask airway. In another study Matsuda et al.[13] found no significant change in overlapping between IJV and CCA after LMA placement. They did all the measurements in 15 degree Trendelenburg position with head turned 30 degrees to the opposite side and they used LMA Softseal (Portex, Smiths medical, London, UK) and Ambu (Tokibo, Tokyo, Japan), whereas we used Ambu AuraOnce™LMA (Ambu LMA) (Ambu A/S, Ballerup, Denmark) and i-gel™ (Intersurgical Ltd., Wokingham, Berkshire, United Kingdom). Each SGAD has cuff with different volume and pressure, and I-Gel has a prefixed gel elastomer non inflatable cuff, which may have contributed to the difference in our results.

We took the measurements with head in neutral and 30 degree rotated to the opposite side, both before and after placement of 2 varieties of SGAD- Ambu AuraOnce™LMA (Ambu LMA) and i-gel™. It was found that the relationship between IJV and CCA not only changes significantly when the head is rotated to the other side but also with insertion of both types of SGAD. The change was more significantly noted with i-gel™ as compared to Ambu AuraOnce™LMA (Ambu LMA).

There are published literature demonstrating the effect of various types of LMA on the anatomical relationship between the two vessels, but the effect of i-gel™ has not been studied so far.

The i-gel™ is a relatively new and disposable supraglottic airway device which is made of a soft gel-like elastomer with a non-inflatable cuff and a channel for gastric catheter placement except in size number 1.[17] Studies which have demonstrated that i-gel™ exerts higher oesophageal sealing pressure than paediatric Ambu,[14] laryngeal mask airway ProSeal and laryngeal mask airway Classic.[1819] This higher leak pressure provides higher safety in obese patients, during pneumoperitoneum and during lithotomy position.[20]

We speculate that the i-gel™ being made up of elastomer gel exerts higher oesophageal sealing pressure which also causes increased distortion of the surrounding soft tissue anatomy leading to increased overlapping between IJV and CCA.

Our study only compared the two varieties of SGAD and used ultrasound guidance to puncture the IJV in all the patients. Hence we did not compare the incidence of CCA puncture or the number of attempts taken to access the IJV in two groups using landmark technique.

We did not study the relationship between size of the device and displacement of IJA/CCA, and used appropriate recommended sizes but different size may have different effect on the relationship of IJA and CCA

We recommend more prospective studies to be conducted both in children and in adults, comparing with number of attempts taken to puncture IJV and incidence of CCA puncture using landmark technique with i-gel™ in situ.

Major limitation of our study was that we did not compare the supraglottic devices with endo tracheal tube (ETT) with regards to positional and anatomical changes. ETT being the gold standard of care, and comparison with ETT would have further affirmed the findings of our study.

The relationship changes between CCA and IJV are dependent on type of the device used and therefore may be unpredictable when different types of devices are used. Therefore, the recommendation will be Ultrasound imaging approach is preferable for this reason.

CONCLUSION

The i-gel™ as compared to Ambu AuraOnce™LMA (Ambu LMA) caused increased alteration in the anatomical relationship between IJV and CCA.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.