Neutral positioning holds its own during ultrasound-guided internal jugular catheterization
In adults undergoing elective surgery, a neutral supine position performed as well as Trendelenburg for ultrasound-guided internal jugular vein catheterization when experienced anesthesiologists used a real-time short-axis out-of-plane approach. The randomized, controlled non-inferiority trial enrolled 216 adults and asked a practical question that has long shaped bedside workflow: does head-down tilt still add value once ultrasound is already guiding the needle?
It did not improve first-pass success.
First-attempt success reached 95.33% in the Trendelenburg group and 99.07% in the neutral group, a difference that favored the neutral position by 3.75 percentage points. The 95% confidence interval ranged from −1.2% to +9.6%, and the lower bound stayed above the prespecified −5% non-inferiority margin. Statistically, that satisfied the trial’s central goal and confirmed that neutral positioning was non-inferior in this setting.
First-pass success stayed high in both groups
The study’s most clinically relevant signal is the consistency of success across both arms. Under real-time ultrasound guidance, the classic rationale for Trendelenburg is straightforward: venous filling should enlarge the target vessel, reduce collapsibility, and make cannulation easier. Yet when operators can see the vein, the needle, and the surrounding anatomy in real time, the marginal gain from gravity-assisted venous engorgement may shrink sharply. In this trial, the success rates remained high either way, suggesting that image guidance may have already neutralized much of the positional advantage historically attributed to Trendelenburg.
The non-inferiority result also held in intention-to-treat analysis and in sensitivity analyses using 3% and 7% margins. That consistency matters because it reduces the chance that the finding rests on a narrow statistical choice. In practical terms, anesthesiologists working in elective surgical patients under general anesthesia do not appear to need routine head-down tilt solely to preserve first-pass access when the procedure is performed by skilled operators using ultrasound.
Trendelenburg enlarged the vein without changing the bedside outcome
Trendelenburg did produce larger internal jugular dimensions. Vertical length and cross-sectional area were both significantly greater in the tilted position, confirming the expected physiologic response to venous pooling in the neck. The striking part is what followed: the anatomic gain did not translate into better clinical success.
That disconnect is clinically important. Vessel size is only one determinant of successful cannulation. Needle tip visualization, operator experience, patient anatomy, and the precision of real-time ultrasound guidance all influence whether the needle enters the lumen on the first attempt. Once the target is continuously visualized, incremental increases in diameter may no longer meaningfully change the procedure’s outcome. In other words, a bigger vein is not always a more useful vein when the operator already has a clear sonographic roadmap.
Safety and efficiency did not depend on a head-down tilt
Secondary outcomes included catheterization time, complication rate, and internal jugular vein dimensions. The trial abstract does not provide detailed numeric differences for time or complications, but the overall interpretation remained stable: neutral positioning performed at least as well as Trendelenburg in the measured procedural domain. For bedside teams, that opens the door to a simpler setup in elective cases where a head-down tilt may be uncomfortable, cumbersome, or unnecessary.
This has implications beyond convenience. Trendelenburg is often used reflexively during central venous access, partly because it is embedded in procedural habit and partly because it is thought to reduce air embolism risk by increasing central venous pressure. Yet in a controlled environment with experienced operators and ultrasound visualization, the routine need for tilt becomes less obvious. A neutral position may also be easier to maintain in patients for whom head-down positioning is undesirable because of respiratory mechanics, hemodynamic concerns, or surgical constraints, although those specific subgroups were not the focus of this study.
What this trial does and does not settle
The population was narrow: elective adult surgical patients undergoing central venous catheterization under general anesthesia, with procedures performed by experienced anesthesiologists. The findings therefore fit best where conditions are controlled and ultrasound skill is high. They do not automatically generalize to emergency access, novice operators, difficult anatomy, or settings where ultrasound is not used consistently.
Even so, the clinical message is concrete. When real-time ultrasound is already in play and an experienced operator is at the bedside, neutral positioning is enough to preserve high first-attempt success for internal jugular cannulation. Trendelenburg still enlarges the vein, but in this trial that did not buy a procedural advantage.
The result should prompt a reassessment of routine head-down positioning during ultrasound-guided internal jugular access, especially in cases where patient comfort, ventilation, or operative logistics make tilt inconvenient. The study leaves open whether the same equivalence would hold in less controlled circumstances, among less experienced clinicians, or during urgent procedures where anatomy and physiology are less forgiving. Those settings are where the old habit may still need testing.