Abstract

Objective

Catheterization of the internal jugular vein (IJV) after placement of a laryngeal mask airway (LMA) has been reported to be difficult. The purpose of this study was to evaluate the accuracy of the central landmark for catheterization of the right IJV after placement of a ProSeal™ LMA.

Methods

We enrolled 80 patients (30 men and 50 women) who were scheduled to undergo surgery under general anesthesia conveyed by a size 3 ProSeal™ LMA. A needle pathway based on the central landmark for right IJV catheterization was simulated. Ultrasound images were obtained, which we contrasted with the simulated pathway to evaluate whether the landmark accuracy remained unchanged after placement of the ProSeal™ LMA. Both frequency of simulated right carotid artery (CA) puncture and overlap between the right IJV and right CA were also investigated.

Results

The simulated needle pathway ran along the course of the right IJV in 60% (48/80) of subjects, and transected the CA in 31.3% (25/80) of subjects. Both events together occurred in 20% (16/80) of subjects. The central landmark had a medial bias of 6.8 mm (95% confidence interval, 5.3-8.4). In 83.8% (67/80) of subjects, the center of the right IJV was lateral to the central landmark. The possibility of overlap of the right IJV and CA was high after ProSeal™ LMA placement.

Conclusion

After placement of the ProSeal™ LMA, the central landmark could not offer a good success rate at the first puncture attempt. When using the central landmark to catheterize the IJV after a ProSeal™ LMA placement, medial deviation of the central landmark should be considered. Ultrasound guidance may be helpful in difficult cases.

Keywords

catheterization, central venous; jugular veins; laryngeal masks: ProSeal;

1. Introduction

Central venous catheterization is associated with a complication  rate  of  approximately  10−15%.¹  The “central landmark”² is commonly used for central venous  catheterization  of  the  right  internal  jugu-lar vein (IJV). However, the landmark-based punc-ture  technique  is  associated  with  a  4−33%  failure rate and a 5−10% rate of inadvertent trauma includ-ing carotid artery (CA) puncture.^3,4 Catheterization of the right IJV after placement of a laryngeal mask airway (LMA) may become more difficult and often causes iatrogenicity, because of overlap of the IJV and  CA,  displacement  of  the  sternocleidomastoid  muscle to act as a principal landmark, and difficulty in palpating the CA.^5,6

Bailey et al evaluated the accuracy of the cen-tral  landmark  for  right  IJV  catheterization  in  the  absence  of  LMA  placement,⁷  and  Takeyama  et  al  reported the increased overlapping of the IJV and CA after Classic™ LMA placement.³ However, there has been no previous investigation on the accuracy of the central landmark for right IJV catheterization after placement of a ProSeal™ LMA.

The  purpose  of  the  study  was  to  evaluate  the  accuracy of the central landmark for IJV catheteri-zation after placement of a ProSeal™ LMA. We used the  digital  cursor  incorporated  in  the  ultrasound  unit to simulate a needle path based on the cen-tral landmark. We then determined the bias of the intersection of the landmark and frequency of the simulated needle path intersecting the IJV or CA, or both together.

2. Methods

After the approval of the review board of the insti-tutional  ethics  committee  of  Kaohsiung  Medical  University  Hospital  and  having  obtained  patient  written informed consent, 80 patients (50 women and 30 men) scheduled to undergo elective surgery under general anesthesia conveyed by a ProSeal™ LMA (Laryngeal Mask Company, San Diego, CA, USA) were enrolled in the study. The surgeries included procedures of the extremities, transurethral proce-dures, mastectomies and inguinal herniorrhaphies.

Before ProSeal™ LMA placement, general anes-thesia was induced with intravenous thiamylal sodium 125 mg and maintained with inhalation of sevoflurane in 100% oxygen. After anesthetization, the patient was kept in the supine position and the head was rotated 30º to the left from the midline.^6,8 A central landmark was marked out on the surface of the right side of the neck, with two heads of the sternoclei-domastoid muscle to form the apex, the sides of a triangle  and  the  clavicle  to  serve  as  the  base.^2,7 Patients  in  whom  the  central  landmark  could  not  be defined were not enrolled in this study.

We routinely used the ProSeal™ LMA, and a size 3  was  our  choice  because  it  suits  most  adult  pa-tients in our daily practice. The cuff pressure was kept at 50−60 cmH2O. If a size 3 ProSeal™ LMA did not  suit  properly  the  patient  was  excluded  from  the study.

Two-dimensional  ultrasound  images  were  ob-tained using a high frequency, 38 mm linear array transducer in the 5−10 MHz range, and a SonoSite Titan unit (SonoSite Ultrasound, Bothell, WA, USA) with  flow  Doppler,  compound  imaging  and  image  capturing capabilities.

After  the  size  3  ProSeal™  LMA  was  properly  placed,  the  sole  investigator  placed  the  probe  at  the apex of the marked-out central landmark and the probe was aimed towards the subject’s ipsilat-eral  nipple,  at  approximately  a  30º  angle  to  the  coronal plane. We used the vertical cursor of the ultrasound image to simulate the needle path whose entry site was the anatomical “central landmark”, and  each  image  was  recorded  for  analysis  as  in  Figure 1.

We tried to determine the accuracy of the central landmark after the placement of a size 3 ProSeal™ LMA. Accuracy determination was decided by two elements: precision and bias. Precision of the cen-tral landmark was defined as the simulated needle path intersecting the right IJV without intersecting the right CA. We documented the rate of the simu-lated needle path intersecting the IJV, CA or both vessels. Then the bias of the central landmark and the percent of overlap of the IJV and CA were cal-culated from the recorded images.

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Figure 1 A representative image obtained in the study. The figure shows a patient in whom the central landmark is medial to the center of the right internal jugular vein (IJV) and the simulated needle path intersects both the IJV and right carotid artery (CA). The vertical white dot-ted line represents the simulated needle pathway whose entry site was the anatomical “central landmark”.

The bias of the central landmark was defined as the measured deviation described below. We mea-sured the landmark bias for each patient, and the measured deviation was calculated from the length of  a  perpendicular  line  drawn  from  the  center  of the vein to the cursor (simulated needle path). The measured deviation was considered positive if the simulated needle path was medial to the center of the IJV. In clinical practice, it was identical to that of  the  central  landmark  being  medial  to  the  tar-geted IJV. The measured deviation was considered negative if the simulated needle path was lateral to  the  center  of  the  IJV.  The  bias  of  the  central  landmark was obtained by calculating the mean of the  measured  deviation  in  a  manner  reported  by  Bland and Altman.⁹

The  overlap  index  (OI)  has  been  proposed  to  represent the percent of overlap of the IJV and CA.¹⁰ The OI was derived from the ratio of the overlap-ping length of the IJV to the horizontal diameter of the CA. The formula for calculation is as follows: OI = [overlap (mm)/CA diameter (mm)] × 100.¹⁰

Demographic data and measured deviation be-tween sexes were analyzed by the Student t test. The one sample t test was used to test the mean of measured  deviation  against  zero  for  all  patients,  with separation of the men and women. Sex differ-ences in OIs were analyzed by the Mann-Whitney U test.  The  SPSS  statistical  software  package  (SPSS  Inc., Chicago, IL, USA) was used for all analyses. All statistical  tests  were  two-tailed  and  p < 0.05  was considered to be statistically significant.

3. Results

Demographic data of all 80 patients are shown in Table  1.  In  the  study,  men  were  younger,  heavier  and taller than women, but body mass index (BMI) did not differ significantly between sexes. Besides, there was no significant difference in OI between men and women (Table 2). No patient was exclud-ed from the study because of unsuitable ProSeal™ LMA placement.

The simulated needle path followed the course of the right IJV in 60% (48/80) of subjects, and tran-sected  the  CA  in  31.3%  (25/80)  of  subjects.  Both  events together occurred in 20% (16/80) of subjects. After  ProSeal™  LMA  placement,  the  OI  was  55.7  (95% confidence interval [CI], 47.6−63.9).

Figure  2  illustrates  a  plot  depicting  the  preci-sion and bias for all patients. The central landmark had a medial deviation of 6.8 mm (95% CI, 5.3−8.4) and this distance did not differ significantly between men  and  women  (p =  0.7).  The  central  landmark  resulted in a simulated needle path that was more often (83.8%, 67/80 patients) medial to the center of the IJV (p < 0.001; Figure 2).

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Figure 2 Plot showing the measured deviation for all patients. For each subject, the measured deviation is equal to the distance of a perpendicular line drawn from the center of the internal jugular vein (IJV) to the simu-lated needle path. Simulated needle paths medial to the center of the IJV were assigned a positive number (above the zero horizontal line) and paths lateral to the center of the internal jugular vein were negative. The majority of needle paths, based on the central landmark, were medial to the center of the IJV, with an average measured deviation of 6.8 mm (the black line).

4. Discussion

According  to  the  measured  deviation  of  the  cen-tral landmark obtained in our study, we found that this landmark had a bias which would advise clinical practitioners  to  introduce  the  needle  in  a  path  6.8 mm medial to the center of the right IJV. Fur-thermore, the medial bias of the central landmark will  produce  a  high  incidence  (31.3%)  of  carotid  puncture if no modification is made to correct the bias.  From  our  results,  it  is  recommended  that  if  the puncture at the first attempt is unsuccessful, the needle should be directed more medially at the next attempt. Bailey et al⁷ reported a similar medial deviation about 4 mm away from the center of the right  IJV  in  awake  subjects.  In  contrast  with  the  study of Bailey et al,7 the degree of measured bias of the central landmark was found to enlarge after LMA placement.

The  precise  rate  of  successful  landmark-based  right  IJV  puncture  was  found  to  be  only  60%,  not  sufficient for standard clinical practice. The mea-sured bias and imprecision of the central landmark may explain the difficulty of right IJV catheteriza-tion  after  LMA  placement.³  Although  ultrasound-guided central venous catheterization and regional anesthesia  have  gained  more  and  more  popular-ity,^8,11−14  many  clinical  practitioners  still  perform  these  anesthetic  techniques  based  on  a  surface  anatomic landmark. In our study, the center of the right IJV was located medially to the central land-mark at a mean distance of 6.8 mm. Hence, we sug-gest that the bias for the central landmark should be taken into consideration whenever it is used to catheterize the right IJV after placement of a size 3 ProSeal™ LMA.

Takeyama et al³ reported a significant increase in the OI after placement of a Classic™ LMA in the central landmark. The OI did not differ significantly between size 3 LMA and size 4 LMA (median, 100 and 79, respectively). Troianos et al¹⁵ reported a high OI (> 75%) in ultrasound images in 54% out of 1136 patients without LMA placement. In our results, the mean OI in all patients after ProSeal™ LMA place-ment was 55.7 (95% CI, 47.6−63.9) and only 12.5% (10/80) of patients were found without overlap of the IJV and CA. It is possible that the ProSeal™ LMA, which has a cuff on the back of the mask, may affect the  anatomy  of  the  surrounding  structures  more  than a Classic™ LMA after cuff inflation. However, the OI after ProSeal™ LMA placement in our study was not higher than that after a Classic™ LMA place-ment  as  reported  in  Takeyama  et  al’s  study.³ The rational explanation for the discrepancy in the re-sults  may  arise  from  our  use  of  a  uniform  size  of  ProSeal™  LMA,  and  racial  traits.  The  influence  of  different kinds of LMA on OI was not studied. We are of the opinion that a further randomized, controlled study is required to identify the differences between the ProSeal™ LMA and Classic™ LMA.

The rate of carotid puncture after ProSeal™ LMA placement is extremely high (31.3%) compared with that without LMA placement in other published re-ports, which ranged from < 1% to 6.3−9.4%.^1,2 Our results showed a high OI with 20% (16/80) of sub-jects having the simulated needle path transecting both the IJV and CA. This rate of carotid puncture might be overestimated compared with actual IJV catheterization.  However,  performing  ultrasound  imaging before IJV catheterization in a patient with an  LMA  in  place  is  mandatory  to  avoid  a  possible  carotid puncture.

Our study has certain innate limitations. First, most of our enrolled patients were not overweight and we did not include an analysis of the effect of BMI on the accuracy of the central landmark. There-fore,  our  results  should  merely  be  applicable  to  those whose demographic data lie within our stud-ied range. Another potential limitation is that we only  simulated  needle  pathways  rather  than  per-formed actual punctures for ethical reasons. We are looking forward to assessment of the success rate of ultrasound-guided IJV catheterization with an LMA in place in future.

In conclusion, after a ProSeal™ LMA placement, the  central  landmark  does  not  offer  an  adequate  success rate at the first puncture attempt because the measured bias may lead to a more medial punc-ture  than  real  targeting  of  the  center  of  the  IJV.  The  bias  should  be  considered  when  the  central  landmark is used for right IJV catheterization after ProSeal™ LMA placement. Ultrasound guidance may be helpful in difficult cases.