Cross-sectional Area Of Right Internal Jugular Vein Research Articles

Influence of various positive airway pressure levels on catheterization of the right internal jugular vein

Background: Central venous catheterization is a commonly used method of administering drugs and measuring central venous pressure during major surgery. Chronic obstructive pulmonary disease, acute respiratory distress syndrome, and obstructive sleep apnea are among the respiratory disorders that can be treated with positive airway pressure (PAP). While PAP therapy benefits patients with respiratory disorders, its impact on central venous catheterization must be more adequately studied, particularly in the right internal jugular vein (RTIJV). Aims and Objectives: The study aimed to predict the most applicable PAP for RTIJV catheterization and to evaluate the complications with different airway pressures. Materials and Methods: This study was conducted using a comparative prospective randomized control trial study design in a tertiary care hospital. One hundred participants were selected from subjects who came for gastrointestinal tract surgery and urological surgery, and they were randomized through a computer-generated random number table. Results: Participants were divided into four different groups (A, B, C, and D), and they were subjected to four pressures 0 cmH2O, 10 cmH2O, 15 cmH2O, and 20 cmH2O, respectively. The cross-sectional area of RTIJV is significantly increased in Groups C and D compared to Groups A and B. The number of completed catheterizations was higher in Groups C and D. The number of first-pass punctures was also higher in Groups C and D. Depth of needle insertion is significantly reduced with increased pressure. Conclusion: Moderate-to-high PAPs, specifically around 15 cmH2O to 20 cmH2O, boost catheterization success. This is achieved through improved vein dilation, enhanced accuracy, and decreased needle insertion depth.

Anatomical changes of the internal jugular vein with Trendelenburg position and head rotation. Evidence for a safer catheterization

IntroductionCentral venous catheterization (CVC) is procedure used in hospital settings for patient monitoring, diagnostic, and therapeutic means. The right internal jugular vein (RIJV) is the first choice recommended, with ultrasound (US)‐guided as the gold standard. This method is not always available, especially in rural settings or developing countries, and complications are still frequent even under expert hands.The head‐down tilt (Trendelenburg) position involves elevation of the lower limbs to favor venous return and increase neck veins regurgitation. Evidence is scarce and contradicting regarding the safety of degree of inclination and head rotation.The objective of this study was to determine the effects of different degrees of Trendelenburg and head rotation on the RIJV and right common carotid artery (RCCA).MethodsAn experimental, longitudinal, prospective, analytical study was performed. Healthy adults of both sexes were recruited to voluntarily participate.Inclusion criteria: adults between 18 and 29 years of age, with normal vital signs, and a BMI ≤24.9. Those with RIJV pathology, anatomical variations, neck surgeries, COVID, or metabolic diseases were excluded.Neck US‐imaging was performed, obtaining cross‐sectional area (CSA) measurements of RIJV and RCCA, and their relationship, at the inferior level of the thyroid cartilage. Randomization at Trendelenburg positions of 0°, 5°, 10° and 15° and left head‐rotation of 0°, 45° and 90° in each inclination were performed. Vital signs and oxygen saturation were monitored between each position, as well questioning for discomfort symptoms.ResultsMeasurement of the RIJV and RCCA area was performed in 54 healthy participants (30 men), age range 21‐32. RIJV basal CSA was 1.0±0.5mm2 in a supine position (0°) without head rotation (0°). Trendelenburg angle and head‐rotation increased the CSA of the RIJV in a statistically significant way, obtaining the greatest area in a 15° Trendelenburg position and maximum rotation (Table 1). This, in turn, had no statistically significant difference with 10° Trendelenburg and 45° rotation (Table 2).ConclusionsA 5º, 10º, or 15º Trendelenburg position and contralateral head rotation increase RIJV CSA. Head rotation also changes the location of the vein anterior to the RCCA at maximum rotation, but not significantly at 45º.Although the greatest area obtained is achieved at the 15º Trendelenburg position with 90º head rotation, this position is uncomfortable and does not have statistical difference with 10º Trendelenburg position with 45 to 90º head rotation, which represents an increase of the initial diameter of 60% of CSA, making it a feasible position.Although Ultrasound‐guided catheterization is the gold‐standard, Trendelenburg position and 45º head rotation help increase RIJV diameter, to create a safer procedure.Significance and implicationsThis study provides anatomical evidence of RIJV changes with Trendelenburg and head rotation. Most international guidelines focus on CVC approach, and fail to mention patient positioning. The publishing of this data will aid with future versions of CVC guidelines.

The effect of different pressures of pneumoperitoneum on the dimensions of internal jugular vein – A prospective double-blind, randomised study

During laparoscopic surgeries, pneumoperitoneum increases intraabdominal pressure (IAP) which can increase the central venous pressure (CVP), and significant haemodynamic changes. In this study, we evaluated the effect of two different pressures of pneumoperitoneum, standard (13-15 mmHg), and low (6-8 mmHg) on the cross-sectional area (CSA) of the internal jugular vein (IJV) using ultrasonography, haemodynamic changes and duration of surgery. Surgeon's comfort and feasibility of performing laparoscopic surgeries with low pressure pneumoperitoneum was also studied. This prospective, double-blind, randomised study included 148 patients of American Society of Anesthesiologists physical status class I and II undergoing laparoscopic surgeries. They were allocated into two groups: group S (standard) (number (n) = 73) had the IAP maintained between 13-15 mmHg; group L (low) had an IAP of 6-8 mmHg (n = 75). CSA of right IJV was measured before induction of anaesthesia (T1), 5 min after intubation (T2), 5 min after pneumoperitoneum (T3), before desufflation (T4) and 5 min prior to extubation (T5). Chi-square test, and Student's paired and unpaired t test were used for statistical analysis. The increase in IJV CSA at T3 when compared to T2 was statistically significant in both the groups (P < 0.001). On desufflation, the change in IJV CSA showed significant decrease in T5 value than T4 value in both the groups (P < 0.001). However, the percentage change in the IJV CSA was more in group S (35.4%) than group L (21.2%). CSA of IJV increased significantly even with lower IAP of 6-8 mmHg. Laparoscopic surgery can be performed conveniently even at low IAP.

Trendelenburg position for internal jugular vein catheterization: A systematic review and meta-analysis.

To determine the effect of Trendelenburg position on the diameter or cross-section area of the internal jugular vein (IJV) a systematic review and metanalysis was performed. Studies that evaluated the cross-sectional area (CSA) and anteroposterior (AP) diameter of the right internal jugular vein (RIJV) with ultrasonography in supine and any degree of head-down tilt (Trendelenburg position) were analyzed. A total of 22 articles (613 study subjects) were included. A >5° Trendelenburg position statistically increases RIJV CSA and AP diameter. Further inclination from 10° does not statistically benefit IJV size. This position should be recommended for CVC placement, when patient conditions allow it, and US-guided cannulation is not available.

Anatomical changes of the internal jugular vein with Trendelenburg position: A systematic review and meta‐analysis

Introduction The anatomy of the internal jugular vein (IJV) may be influenced by the position of the patient. A head-down-tilt or Trendelenburg position could potentially increase the size and diameter of the IJV, however, its use in clinical scenarios, such as cathetherization (a frequent procedure), is debatable. Small venous cross-section could make cannulation difficult, even while guided by ultrasound, increasing the risk of complications. The objective of this study was to systematically review all studies that analyze parameters of IJV size variations due to Trendelenburg position evaluated by ultrasound. Methods Adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, all cross-sectional studies comparing the effect of Trendelenburg position were included. Any degree of head-down tilt with a supine position on the cross-sectional area (CSA) and anteroposterior (AP) diameter of the right internal jugular vein (RIJV) in healthy adults were eligible. Measurements and outcomes had to be with ultrasonography. An experienced librarian designed and conducted the search strategy in Ovid MEDLINE, EMBASE, Web of Science, Scopus, and Cochrane. Four independent reviewers, working in duplicate, assessed for eligibility of studies. Cross-sectional area (CSA) and anteroposterior (AP) diameter of the RIJV were collected and pooled using fixed-effects meta-analyses. Effect sizes are presented as mean difference (MD) and 95% confidence interval (CI). Heterogeneity between studies was assessed using the X2 test and I2 statistic. Data syntheses were conducted using Review Manager Version 5.3. Results A total of 22 articles (613 study subjects) were included. The overall risk of bias was moderate. In healthy adults, exposure to any degree of the Trendelenburg position significantly increased the CSA (MD:0.38cm²; [95% CI:0.35-0.41]; P<0.00001; I²=0%) and AP diameter (MD:1.87 mm; [95% CI:1.51-2.23]; P<0.00001; I²=0%) of the RIJV. No significant changes were exhibited when comparing the results of studies performed with the head rotated (MD:0.35cm²; [95% CI:0.29-0.42]; P<0.00001; I²=0%) with those using a neutral position of the head (MD:0.38 cm²; [95% CI:0.35-0.41]; P<0.00001; I²=0%) No significant increase of the AP diameter of the RIJV was identified from the 10° Trendelenburg position to both 15° and 20° inclinations. Conclusions The available published evidence favors Trendelenburg position, with a >5° statistically increasing RIJV CSA and AP diameter. Further inclination from 10° does not statistically benefit IJV size. This position should be recommended by international guidelines for CVC placement, when patient conditions allow it, as most guidelines fail to mention patient positioning.

Effects of combined the trendelenburg and passive leg raising positions on the cross-sectional area of the right internal jugular vein.

The primary aim of this study was to assess the effects of a combination of the passive leg raising (PLR) and Trendelenburg positions on the cross-sectional area (CSA) of the right internal jugular vein (RIJV) using ultrasound measurement in awake patients. This prospective observational cross-over study measured the CSA of RIJV in patients in supine (Supine-I), Trendelenburg, Trendelenburg with passive leg raising (T + PLR position), and repeated supine position (Supine-II). The CSA and vertical and horizontal diameters of the RIJVs were compared before and after each position. A total of 120 adult patients were enrolled in the study. The mean CSA of the RIJV significantly increased from 91.2 ± 31.7 mm2 to 110.4 ± 38.2 mm2 in the Trendelenburg position compared to the supine position (P < 0.05). However, there were no statistically significant differences in CSA were observed between the Trendelenburg and Trendelenburg + PLR positions. Although the PLR + Trendelenburg position increased the jugular vein diameter relative to the supine position, its clinical usefulness is limited as this increase was still lower than that achieved with the Trendelenburg position alone.

The Effects of Positive End-Expiratory Pressure on Cross-Sectional Area of Internal Jugular Vein in Obese Patients

Introduction: Obesity is one of the most important risk factors for complications of internal jugular vein (IJV) cannulation. The efficacy and safety of positive end-expiratory pressure (PEEP) are still under debate in obese patients. The aim of this prospective randomized ultrasound study was to investigate effects of different PEEP levels on the cross-sectional area (CSA) of right IJV and overlap with carotid artery (CA) in anesthetized obese patients. Materials and Methods: Seventy-two obese patients undergoing various elective surgeries under general endotracheal anesthesia were enrolled. We measured CSA of right IJV, margin of safety (MOS), and degree of overlap between CA and IJV at PEEP 0 (P0), 5 (P5), and 12 (P12) cm H2O levels. We defined a ≥20% increase in CSA as clinically relevant. Results: Data were collected for all the 72 patients enrolled in the study. Application of 12, but not 5 cm H2O PEEP, resulted in a clinically significant increase in CSA of right IJV. When compared to P0, application of P5 and P12 increased both degree of overlap (p < 0.001 each) and MOS (p < 0.001 each). None of the patients experienced severe hypotension or bradycardia. Conclusions: Application of 12 cm H2O PEEP provides a clinically significant increase in CSA of right IJV without relevant reduction of MOS in anesthetized obese patients.

Effects of incrementally increasing tidal volume on the right internal jugular vein in pediatric patients

The aim of the present study was to evaluate the effects of incremental increases of tidal volume (TV) on the cross-sectional area (CSA) and size of the right internal jugular vein (RIJV), and the relationship between RIJV and the carotid artery (CA). This prospective study included 23 pediatric patients aged between 7 and 12 years who were anesthetized. Using a standard anesthesia protocol, the TV was increased from 6 to 10 mL/kg in 1 mL/kg increments. For each TV, images of the RIJV and CA at the level of the cricoid cartilage were recorded at the end of the inspiration. From these results, the CSA and size of the RIJV and the percentage of CA overlap were calculated. The median (interquartile range) RIJV CSA was 0.82 (0.52-1.07) cm2 at a TV of 6 mL/kg and significantly increased to 0.86 (0.58-1.05), 0.88 (0.55-1.08), 0.95 (0.62-1.17) and 1.02 (0.70-1.20) cm2 at TVs of 7, 8, 9 and 10 mL/kg, respectively. There were no significant differences in the percentage overlap of the CA between all TVs. The median (interquartile range) transverse diameter was 1.16 (0.99-1.36) cm at a TV of 6 mL/kg and significantly increased to 1.20 (1.10-1.41), 1.26 (1.05-1.45), 1.28 (1.10-1.49) and 1.35 (1.12-1.52) cm at TVs of 7, 8, 9 and 10 mL/kg, respectively. The median (interquartile range) anteroposterior diameter was 0.77 (0.72-0.90) cm at a TV of 6 mL/kg and significantly increased to 0.81 (0.72-0.94), 0.85 (0.74-0.99), 0.88 (0.75-1.02) and 0.89 (0.79-1.06) cm at TVs of 7, 8, 9 and 10 mL/kg, respectively. This study reveals that a TV of 10 mL/kg in anesthetized children achieved the greatest size in the RIJV, and caused no difference in the CA overlap. These results suggest that a TV of 10 mL/kg is the optimal choice when facilitating catheterization and in the avoidance of complications in anesthetized children connected to mechanical ventilator that are required to undergo RIJV catheterization.

Effect of Trendelenburg position on right and left internal jugular vein cross-sectional area.

Background Unlike the right internal jugular vein (RIJV), there is a paucity of data regarding the effect of the Trendelenburg position on the left internal jugular vein (LIJV). The purpose of this study is to investigate the cross-sectional area (CSA) of the LIJV and RIJV and their response to the Trendelenburg position using two-dimensional ultrasound in adult subjects.MethodsThis study enrolled fifty-eight patients with American Society of Anesthesiologists physical status class I-II who were undergoing general anesthesia. CSAs of both the RIJV and LIJV were measured with a two-dimensional ultrasound in the supine position and then in a 10° Trendelenburg position.ResultsIn the supine position, the transverse diameter, anteroposterior diameter, and CSA of the RIJV were significantly larger than those of the LIJV (P < 0.001). Of 58 patients, the RIJV CSA was larger than the LIJV CSA in 43 patients (74.1%), and the LIJV CSA was larger than the RIJV CSA in 15 patients (25.9%). In the Trendelenburg position, CSAs of the RIJV and LIJV increased 39.4 and 25.5%, respectively, compared with the supine position. However, RIJV changed at a rate that was significantly greater than that of the LIJV (P < 0.05). Of 58 patients, the RIJV CSA was larger than the LIJV CSA in 48 patients (82.8%), and the LIJV CSA was larger than the RIJV CSA in 10 patients (17.2%).ConclusionsIn supine position, the RIJV CSA was larger than the LIJV CSA. The increased CSA in the Trendelenburg position was greater in the RIJV than the LIJV.

Effects of incrementally increasing tidal volume on the cross-sectional area of the right internal jugular vein

BackgroundDifferent tidal volume (TV) settings during mechanical ventilation alter intrathoracic blood volume, and these changes could alter central venous pressure and the cross sectional area (CSA) of the right internal jugular vein (RIJV). The aim of this study was to determine the optimal TV for maximizing the CSA of the RIJV in the supine and Trendelenburg positions in anesthetized patients.MethodsForty patients were randomly allocated to a supine group (Group S, n = 20) or a Trendelenburg group (Group T, n = 20) by computer generated randomization. RIJV CSAs were measured repeatedly after increasing the inspiratory volume in 1 ml/kg increments from a TV of 8 ml/kg to 14 ml/kg using ultrasound images.ResultsPeak inspiratory pressure increased significantly on increasing TV from 11 ml/kg to 14 ml/kg and between baseline (TV 8 ml/kg) and 11 ml/kg in both groups (P < 0.05). RIJV CSA was not increased versus baseline even after TV changes in either group and no intergroup difference was found.ConclusionsTV increases do not increase the CSA of the RIJV within the TV range 8 to 14 ml/kg in the supine or 10° Trendelenburg position.

Factors Predictive of Right Internal Jugular Vein Cross-Sectional Area Change in Response to Trendelenburg Positioning

Background/Purpose: The right internal jugular vein (RIJV) is the most commonly accessed central venous site in the cardiac operating room. The Trendelenburg position is frequently used to increase the cross-sectional area (CSA) of the RIJV to facilitate its cannulation. However, the extent of change of RIJV CSA in response to Trendelenburg positioning in anesthetized patients and its predictive factors remain unknown. Methods: Thirty-seven patients presented for the cardiac surgery, and 20 ASA I and II surgical patients without a history of cardiac disease (control) were studied. After induction of anesthesia, RIJV CSA was measured both at supine level position and in 10-degree Trendelenburg using vascular ultrasonography. Central venous pressure was measured in cardiac surgery patients only, since the patients in control group did not require invasive lines placement. Results and Conclusions: Body-surface area, central venous pressure, type of surgery and ejection fraction did not show any correlation with the degree of RIJV CSA change. RIJV dilation in response to Trendelenburg was significantly less pronounced, and more variable, in female patients.

The Effect of Passive Leg Elevation and/or Trendelenburg Position on the Cross-Sectional Area of the Internal Jugular Vein in Infants and Young Children Undergoing Surgery for Congenital Heart Disease

In this study we evaluated the effect of passive leg elevation (LE) and Trendelenburg (T) position on the cross-sectional area (CSA) of the internal jugular vein (IJV) in infants and young children undergoing surgery for congenital heart disease. A secondary aim was to compare the CSA of the IJV between subjects with right-to-left (RL) shunt and left-to-right (LR) shunt. Ninety infants and small children from 10 days to 31 months old weighing from 1.5 to 9.7 kg were assigned to group RL (n = 48) or LR (n = 42). In both groups, the CSA, transverse, and vertical diameters of the IJV on both sides of the neck were measured using a 2-dimensional ultrasound transducer in the following positions: supine position, 15° of T position, supine position with 50° of LE, and 15° of Trendelenburg position with 50° of LE (TLE). A more than 25% increase in mean CSA of the IJV was considered clinically significant. In group LR, T, LE, and TLE significantly increased CSA of both right (at least 12.3%, 10.3%, and 18.3%, respectively, "at least" refers to the lower 95% confidence limits) and left (at least 15.8%, 15.0%, and 18.9%, respectively) IJVs, whereas only TLE increased the CSA of both IJVs significantly in group RL (at least 8.2% and 7.7% in the right and left, respectively). The increase in the CSA of the right IJV related to T and TLE was larger in group LR than in group RL (at least 12.3% vs 1.2% for T and at least 18.3% vs 8.2% for TLE, respectively). A clinically significant increase in CSA was achieved in both right and left IJVs with TLE in group LR (mean 28.6% and 26.3%, respectively). The CSA of the right IJV was larger than that of the left IJV in most (at least 69.2%) patients. Passive LE was as effective as T position to increase the CSA of the IJV, but there was no clinically significant increase in the CSA with any single maneuver. Only T position with passive LE achieved a clinically significant increase in the CSA of both IJVs in infants and young children with LR shunt, but not in the same age group with RL shunt.

Effects of four different positive airway pressures on right internal jugular vein catheterisation

The right internal jugular vein (RIJV) is often used for central venous catheterisation in patients undergoing major surgery. The efficacy of this route correlates with the diameter of the vein which can be influenced by airway pressure. To investigate four positive airway pressures (PAPs) in mechanically ventilated patients and to determine the most suitable of these for RIJV catheterisation. Prospective, randomised, controlled study. Two Chinese medical centres. Two hundred and forty patients scheduled for gastrointestinal tract surgery under general anaesthesia (male-to-female ratio, 135 : 105; American Society of Anesthesiologists' physical status class, I-III; age range, 19-81 years); patients were excluded from the study if they had a history of haematological disease, external neck injury, RIJV catheterisation, severe cardiovascular disease, RIJV thrombosis, injection-site infection, pneumothorax and pulmonary bulla. They were randomised into four groups of 60, each to undergo RIJV catheterisation at a PAP of 0 (1 cmH2O = 0.098 kPa, group A); 15 (group B); 20 (group C); and 25 cmH2O (group D). Primary outcomes were central venous pressure (CVP) and RIJV cross-sectional area which were measured before and during PAP; the number of catheterisations completed in 30 s; the number of first pass punctures; heart rate and mean arterial pressure which were monitored continuously; and the incidence of complications which included local haematoma, pneumothorax and internal carotid artery (ICA) puncture. Two patients were excluded following ICA puncture, leaving 238 for analysis. In groups C and D, the CVP and the cross-sectional area of RIJV were significantly larger; the number completing catheterisation within 30 s and the number of first pass punctures increased significantly and was comparable between these two groups. Compared with groups A and B, the incidences of hypotension and bradycardia were significantly increased in groups C and D. The incidence of local haematoma was significantly increased in group D compared with other groups. RIJV catheterisation was completed successfully in all but two patients in group A. A PAP of 20 cmH2O seems most suitable for successful RIJV catheterisation in mechanically ventilated patients. It is associated with an increase in cross-sectional RIJV area and CVP, which facilitate cannulation, and results in fewer puncture-related complications. However, meticulous haemodynamic monitoring is needed to avoid hypotension and bradycardia.

Effects of Positive End-Expiratory Pressure on Internal Jugular Vein Cross-Sectional Area in Anesthetized Adults

We tested whether positive end-expiratory pressure (PEEP) increases right internal jugular vein (RIJV) cross-sectional area (CSA) in 45 ASA physical status I and II adults. All patients received a standardized IV fluid bolus, induction of general anesthesia, tracheal intubation, and mechanical ventilation. We evaluated the CSA of the RIJV using ultrasound without PEEP (control) and with PEEP (10 cm H(2)O) in the supine, level position. Addition of PEEP increased RIJV CSA 0.42 + or - 0.41 cm(2) (mean + or - SD, median 0.34 cm(2), P < 0.001), which represented a 41% mean increase in CSA.

Detection of elevated right atrial pressure using a simple bedside ultrasound measure

Accurate assessment of right atrial pressure (RAP) often requires invasive measurement. With normal RAP, Valsalva increases right internal jugular vein (RIJV) cross sectional area (CSA) 20% to 30%. With high RAP, when venous compliance is low, we hypothesized that the increase in CSA would be blunted and could be detected non-invasively with bedside ultrasound. RIJV ultrasound images were obtained in 67 patients undergoing right heart catheterization. The median RAP at end-expiration was 7 mm Hg (interquartile range [IQR] 5-9 mm Hg) in patients with normal RAP (n = 47) versus 15 mm Hg (IQR 12-22 mm Hg) in patients with elevated RAP (n = 20). With Valsalva, the median percent change in RIJV CSA was 35% (IQR 19%-79%) versus 5% (IQR 3%-14%) for normal and high RAP, respectively. By receiver operating curve analysis, a <17% increase in RIJV CSA with Valsalva predicted elevated RAP (> or =12 mmHg) with 90% sensitivity, 74% specificity, 94% negative predictive value, and 60% positive predictive value (area under the curve 0.86, P < .001). An increase in RIJV CSA >17% during Valsalva effectively rules out elevated RAP. This simple bedside technique may be useful to assess central venous pressure and reduce the need for invasive pressure measurement.

Trendelenburg Position, Simulated Valsalva Maneuver, and Liver Compression Do Not Alter the Size of the Right Internal Jugular Vein in Patients with a Bidirectional Glenn Shunt

Ultrasound is increasingly used to facilitate right internal jugular vein (RIJV) cannulation in children. In children without cardiac disease, position changes and enhancement maneuvers increase RIJV cross-sectional area (CSA) and further facilitate cannulation. We investigated the effect of these maneuvers on RIJV CSA in children with a bidirectional Glenn (BDG) shunt presenting for a Fontan procedure. The CSA (cm(2)) of the RIJV in 21 children with a BDG shunt presenting for a Fontan procedure was assessed by ultrasonic planimetry (SonoSite). Two positions, supine (S) and 15 degrees Trendelenburg (T); and two enhancements maneuvers, manual liver compression (L) and a simulated Valsalva maneuver (V) were utilized in combination. Eight separate measurements (S, S + L, S + V, S + L + V, T, T + L, T + V, T + L + V) were made in each patient. Data were analyzed using one-way analysis of variance with repeated measures and with Tukey post hoc pairwise comparison analysis. No significant change in the RIJV CSA or % change in CSA from baseline (S) was observed. Position changes and enhancement maneuvers are unlikely to facilitate RIJV cannulation in BDG shunt patients presenting for Fontan procedure because these interventions do not increase RIJV CSA.