Comparative outcomes of central venous access via open jugular and ultrasound-guided subclavian approaches in low-weight pediatric patients: a study with secondary outcomes

Abstract

Background

The necessity of this study stems from the lack of comparative evidence on the outcomes of central venous catheterization via the open internal jugular and ultrasound-guided subclavian approaches in low-weight pediatric patients. Its innovation lies in the simultaneous evaluation of both primary and secondary outcomes of these two techniques in this vulnerable population.

Methods

This prospective randomized clinical trial at Mardani Azar Children’s Hospital (winter 2022–2023) included 92 pediatric patients under five kilograms weight, randomly assigned to either open internal jugular or ultrasound-guided subclavian vein catheterization (46 per group). Procedural success and major complications—such as pneumothorax, arterial cannulation, ectopic catheter placement, infection, and thrombosis—were evaluated intraoperatively and during a two-weeks follow-up using imaging and clinical assessment.

Results

The mean catheter placement time was significantly longer in the jugular group than in the subclavian group (41.19 ± 13.8 vs. 33.15 ± 12.12 min; P = 0.04). No cases of pneumothorax, hemothorax, bleeding, arrhythmia, occlusion, infection, or death occurred in either group. Hematoma developed only in the jugular group (6 vs. 0; P = 0.02), and all cases were associated with a procedure duration greater than 35 min (P = 0.041). In the subclavian group, all failures (n = 4) and upper limb edema (n = 3) occurred exclusively in patients under 2.5 kg, with both outcomes significantly linked to lower body weight (P = 0.03 and P = 0.014, respectively). Other complications showed no significant differences between groups.

Conclusion

Both approaches were generally safe, with no major adverse events observed in either group. Ultrasound-guided subclavian access was associated with a shorter procedure time, whereas hematoma occurred only in the jugular group and catheterization failure and upper-limb edema were seen only in low-weight infants in the subclavian group. However, because access site and technique were evaluated together, their independent effects could not be determined. In addition, the findings in infants weighing < 2.5 kg were based on few events and should be considered hypothesis-generating rather than definitive.

Trial registration

This clinical trial was registered in the Iranian Registry of Clinical Trials (IRCT) with the code IRCT20230901059317N1(Registration date: 2024-02-16).

Introduction

Central venous access is a fundamental therapeutic tool in pediatric medicine, particularly for patients admitted to intensive care units. This technique enables the administration of vasopressor agents, hypertonic solutions, total parenteral nutrition, transfusion of blood products, as well as frequent blood sampling and advanced hemodynamic monitoring [1]. However, central venous catheterization in neonates and children weighing less than 5 kg poses considerable challenges due to their unique anatomic and physiologic characteristics [2]. Smaller vessel calibers, closer proximity to vital structures such as arteries and nerves, increased vessel mobility compared to adults, and limited physiologic reserves all contribute to a heightened risk of complications in this vulnerable population [3].

Over the past decades, attention has increasingly focused on identifying the most suitable and safest approach to central venous access in these patients. Two principal techniques are commonly used: the open internal jugular vein approach and the ultrasound-guided subclavian approach [4]. The open jugular technique, a classic surgical procedure, involves making a small incision in the neck and directly visualizing the internal jugular vein for catheter insertion [5]. While this method allows for better bleeding control and direct identification of adjacent structures, it is also associated with higher risks of infection at the surgical site, potential injury to adjacent tissues, longer procedure times, and the possibility of scarring [6].

With advances in ultrasound technology and the adoption of minimally invasive interventions, ultrasound-guided subclavian vein cannulation has emerged as a popular and modern alternative. Real-time ultrasound guidance facilitates anatomical identification of the subclavian vein and enables safe needle advancement under direct visualization [7]. Several advantages have been reported for this approach, including reduced rates of unsuccessful attempts, lower risk of vascular or organ injury, decreased incidence of complications such as pneumothorax and hemothorax, and higher first-pass success rates [8]. Nevertheless, in infants and children weighing less than 5 kg, the small vessel size, shallow depth, and the close anatomical relationship to the subclavian artery and the lung apex maintain a significant risk of complications, underscoring the importance of operator expertise and technical proficiency [9].

While numerous studies have addressed the efficacy and safety of each technique individually in children and neonates, comparative clinical data focusing on patients weighing less than 5 kg remain limited and fragmented [10]. Selecting the optimal access route and technique can have a significant impact on immediate outcomes (such as procedural success, acute complications, and early infection) and long-term results (including late infection, thrombosis, and catheter displacement). Further complicating the decision are patient-related factors such as underlying health status, coagulopathy, the experience of the medical team, and the availability of advanced equipment [11, 12].

Improvements in neonatal and pediatric intensive care have increased the survival of premature and critically ill infants, making the identification of safer, more effective, and less complication-prone approaches to central venous access a key research priority [13]. In this context, a direct comparison of the outcomes and complications associated with the open internal jugular and ultrasound-guided subclavian approaches will provide valuable evidence to inform clinical protocols and enhance quality of care [14].

Accordingly, the present study aims to compare the clinical outcomes and complications of central venous catheterization performed via these two major techniques in children weighing less than 5 kg. By identifying the strengths and limitations of each approach, this research seeks to provide actionable insights and scientific evidence that can guide optimal clinical decision-making in this particularly high-risk pediatric population. Ultimately, our findings may contribute to improving clinical outcomes and patient safety for low-weight infants treated in critical care settings.

Materials and methods

Study design

This investigation was structured as a prospective, randomized clinical trial involving pediatrics, neonates and infants patients under five kilograms weighing who were candidates for central venous catheterization. The study was conducted at Mardani Azar Children’s Hospital, affiliated with Tabriz University of Medical Sciences. Data collection and patient enrollment took place over a one-year period, from winter 2022 to winter 2023.

Sampling

The sample size was estimated using the formula for comparing two independent groups. Based on this calculation and findings from a similar study [15], the incidence of complications was considered to be 30% in the open jugular group and 10% in the ultrasound-guided subclavian group, with a statistical power of 80% and a type I error of 0.05. The required sample size was determined to be 60 patients, accounting for a 10% attrition rate. However, given the higher number of eligible cases during the one-year study period, a total of 92 patients were ultimately enrolled and analyzed using a convenience sampling method.

Eligibility criteria

Eligible participants for this study were pediatric patients weighing less than 5 kg who required central venous catheterization for clinical indications such as medication administration, parenteral nutrition, or advanced monitoring. Inclusion criteria encompassed children admitted to Mardani Azar Children’s Hospital during the study period and whose legal guardians provided informed consent. Patients were excluded if they had congenital or acquired coagulopathy, anatomical abnormalities of the neck or chest preventing catheter insertion, active local or systemic infection at the time of procedure, history of central venous catheterization complications, or if they were deemed unsuitable for either the open internal jugular or ultrasound-guided subclavian approach by the attending medical team. This approach ensured a homogenous study population while minimizing confounding variables and procedure-related risks. It should be noted that all procedures were performed by the study’s primary supervising investigator, who had a minimum of five consecutive years of experience in neonatal catheter placement.

Randomization and blinding

In this study, the randomization process was carried out using the https://Randomization.com platform in a structured and reproducible manner. The total number of participants (92 patients) and the target allocation (two equally sized groups) were first entered into the Randomization Tool. A fixed-block randomization scheme was then selected to ensure balanced group distribution throughout enrollment. After specifying the block size (e.g., blocks of four or six) and enabling the anti-predictability option, the system generated a coded randomization list that assigned each consecutively enrolled patient to either the intervention or control group based on their allocation number. The encrypted output file was made available exclusively to the primary supervising investigator, ensuring confidentiality and maintaining full blinding of the data-collecting physician and other study personnel involved in outcome assessment. While the operating surgeon (the primary supervisor) was necessarily aware of the assigned intervention and therefore could not be blinded, both the biostatistician responsible for data analysis and the data-collecting physician (the resident author of the thesis) who recorded the relevant outcomes were blinded to the group allocations and the type of surgical technique performed on each patient. As a result, this study was conducted in a single-blind design.

Procedure

Patient preparation

All patients initially underwent either local anesthesia with lidocaine or sedation using sevoflurane gas, midazolam, or fentanyl, selected based on individual patient conditions. In the sedation group, anesthesia was managed either via mask ventilation or endotracheal intubation, as clinically appropriate. Each patient was positioned supine with a roll placed under the shoulder and the head rotated 45 degrees to the left. The neck was prepared and draped in a sterile fashion. A 5 F ARROW central venous catheter was used in all cases.

Initial cannulation attempt

To avoid any ambiguity regarding patient enrollment, it is important to clarify that no attempts at internal jugular venous cannulation were performed prior to randomization. All eligible patients first underwent a preliminary ultrasound assessment of the neck and chest to exclude pneumothorax, anatomical abnormalities, or any potential contraindications to either the subclavian or internal jugular approach. This step was conducted solely to ensure baseline procedural safety and did not involve any form of vascular intervention. After confirming eligibility, patients were randomized according to the study protocol to either the internal jugular approach or the ultrasound-guided subclavian approach. All cannulation attempts were subsequently performed only after randomization and strictly according to each patient’s assigned group. Post-procedural assessment for pneumothorax was performed in both groups by an experienced operator.

Open internal jugular vein group

In the first group, open internal jugular catheterization was performed. A small skin incision was made on the neck, and the right internal jugular vein was dissected and isolated. A separate venotomy was then created, and the central venous catheter was inserted directly under direct vision without using a guidewire. The vein was repaired and the catheter was secured with non-absorbable sutures. In a minority of cases, distal ligation of the vein was performed as necessary. If initial placement was unsuccessful, the left internal jugular vein was utilized using the same technique.

Ultrasound-guided subclavian vein group

In the second group, ultrasound-guided subclavian vein cannulation was performed in accordance with the latest Armstrong radiology reference guidelines [16, 17]. The subclavian artery and vein were identified both in transverse and longitudinal planes beneath the ultrasound probe, below the clavicle and above the second rib. The subclavian vein was cannulated from a lateral approach under the clavicle. Once intravascular needle placement was confirmed by blood aspiration and ultrasound, a guidewire was advanced through the needle into the vein. Guidewire placement was further verified by ultrasound. The needle was then removed, and a dilator was passed over the guidewire. Following removal of the dilator, the central venous catheter was advanced over the guidewire into the subclavian vein. After confirmation of correct intravascular positioning, the guidewire was withdrawn, and the catheter was secured to the skin with suture. In cases of failed subclavian access, open internal jugular catheterization was then attempted.

The following devices were used for catheter insertion: a double-lumen 5 Fr catheter (1.8 mm OD × 13 cm), a marked spring wire guide (0.53 mm diameter × 45 cm) with a straight soft tip at one end and a J-tip at the other, a 25-gauge injection needle, a 20-gauge introducer needle, a 5-mL syringe, and two tissue dilators (6 Fr; 2 mm × 7.6 cm and 2 mm × 4.1 cm). The Seldinger wire-assisted technique was employed. For ultrasound guidance, the probe was positioned beneath the clavicle, and differentiation of the subclavian artery and vein was ensured using flow characteristics and Doppler parameters, including a peak systolic velocity (PSV) of < 200 cm/s and a resistance index (RI) between 0.8 and 0.9 for arterial identification. The subclavian vein was simultaneously confirmed based on its anatomic location. These steps were undertaken to prevent inadvertent arterial cannulation and ensure accurate venous access.

Post-procedural assessment and follow-up

After catheter placement, all patients were evaluated intraoperatively for the position and possible complications including arterial cannulation, pneumothorax, hemothorax, ectopic catheter migration (outside the superior vena cava), and arrhythmia using both ultrasound and portable chest radiography. Post-operatively, patients were serially examined for thrombosis using echocardiography by an experienced operator, and monitored for hematoma, infection, and bleeding at the catheter site over a two-week period. All patients were thoroughly assessed for every possible complication to ensure that no adverse event was overlooked.

Statistical analysis

All study data were analyzed using SPSS software version 16. Descriptive statistics, including frequency, percentage, mean, and standard deviation, were utilized to summarize the data. The Chi-square test was employed to compare qualitative variables between groups. For comparisons of quantitative variables, the one-way ANOVA, independent t-test, and the non-parametric Kruskal-Wallis test were applied as appropriate. A p-value less than 0.05 was considered statistically significant.

Results

A total of 92 patients were enrolled and randomly assigned into two groups of 46 each. All participants received their allocated intervention and were followed throughout the study. There was no loss to follow-up, withdrawal, or exclusion after randomization. Data analysis was performed for all 92 patients according to the intention-to-treat principle, and each participant was included in the final analysis. Thus, the attrition rate was zero, and the flow of participants was fully maintained from allocation through to analysis (Fig. 1).

Fig. 1.

Patient enrollment and follow-up process based on the CONSORT flowchart

In this study, 92 patients were assessed in two groups of 46 each. The subclavian group included 18 females and 28 males, while the jugular group included 23 females and 23 males (P = 0.89). The mean age was similar between the subclavian and jugular groups (28.6 ± 3.9 vs. 23.26 ± 4.5 days; Mean Difference [MD] = 5.34 days; 95% CI: −11.5 to + 22.1, P = 0.76). Likewise, average weight did not differ significantly (3.13 ± 0.1 vs. 2.96 ± 0.1 kg; MD = 0.17 kg; 95% CI: −0.04 to + 0.38, P = 0.34). In terms of gestational status, the subclavian and jugular groups comprised 26 and 20 term infants, and 20 and 26 preterm infants, respectively (RR for preterm status = 1.14; 95% CI: 0.77–1.70, P = 0.29). Regarding anesthesia, 25 patients in the subclavian group and 14 in the jugular group underwent anesthesia with a face mask, while 21 in the subclavian group and 32 in the jugular group underwent endotracheal intubation (RR = 0.83; 95% CI: 0.55–1.24, P = 0.19).

Baseline characteristics were comparable between the jugular and subclavian access groups across both weight categories (< 2.5 kg and ≥ 2.5 kg). The distribution of sex did not differ significantly between groups (P = 0.761). Mean age at the time of catheter insertion was similar across access routes and weight subgroups (P = 0.344). Likewise, mean body weight showed no statistically significant difference between the corresponding groups (P = 0.341). The proportion of term versus preterm neonates was also comparable between groups, with no significant difference observed (P = 0.293)(Table 1).

Table 1.

Baseline characteristics of neonates according to weight and venous access route

Variables	Jugular Vein Access Weight ≥ 2.5 kg (n = 35)	Jugular Vein Access Weight < 2.5 kg (n = 12)	Subclavian Vein Access Weight ≥ 2.5 kg (n = 35)	Subclavian Vein Access Weight < 2.5 kg (n = 11)	P value
Sex, n	18 Female / 17 Male	5 Female / 6 Male	12 Female / 22 Male	6 Female / 6 Male	0.761 *
Age, days (mean ± SD)	28.50 ± 5.10	24.40 ± 2.96	28.10 ± 4.25	25.60 ± 3.10	0.344 **
Weight, kg (mean ± SD)	3.20 ± 0.30	2.15 ± 0.10	3.55 ± 0.41	2.10 ± 0.12	0.341 **
Term neonates, n	19	1	25	1	0.293 *
Preterm neonates, n	16	10	9	11

*: Fisher’s Exact Test; **:Independent Samples t-test

Catheter insertion time was measured from the initiation of the cannulation procedure to the moment the operator declared the attempt successful or unsuccessful. The mean catheter placement time was notably longer in the jugular group compared with the subclavian group. This difference was clinically and statistically meaningful (MD = 8.04 min; 95% CI: 1.0–15.0; P = 0.04)(Fig. 2).

Fig. 2.

Comparison of catheter placement time between jugular and subclavian groups

No cases of pneumothorax, hemothorax, bleeding, arrhythmia, occlusion, infection, or death were observed in either the jugular or subclavian groups, with all event rates being zero in both groups. Thrombosis was documented in both groups, with 6 cases in the jugular group and 5 cases in the subclavian group, showing no significant difference (P = 0.95). Catheter migration occurred in 3 patients in the subclavian group but was not observed in the jugular group (P = 0.24, not significant). Hematoma developed in 6 patients in the jugular group but was absent in the subclavian group, representing a statistically significant difference (P = 0.02). Upper limb edema was seen in 3 patients from the subclavian group and not in the jugular group (P = 0.7, not significant). Failure occurred in 4 patients in the subclavian group and in none from the jugular group (P = 0.11, not significant)(Table 2).

Table 2.

Distribution of catheterization failure and upper limb edema by weight subgroups in jugular and subclavian groups

Variables	Jugular Group			Subclavian Group
	< 2.5 kg	≥ 2.5 kg	P Value	< 2.5 kg	≥ 2.5 kg	P Value
Catheterization failure, n	0	0	1	4	0	0.03
Upper limb edema, n	0	0	1	3	0	0.014
Thrombosis	3	3	1	3	2	0.107
Catheter Migration	0	0	1	1	2	0.115
Hematoma	4	2	0.120	0	0	1

In the subgroup analysis based on weight, all catheterization failures (n = 4) and upper limb edema cases (n = 3) occurred exclusively in subclavian patients weighing < 2.5 kg. Catheterization failure was significantly more frequent in infants < 2.5 kg compared with those ≥ 2.5 kg (RR = 9.0; 95% CI: 1.26–64.3). Similarly, the incidence of upper limb edema was higher among infants < 2.5 kg (RR = 7.0; 95% CI: 1.11–44.0). No events were observed in either weight subgroup within the jugular group (Table 2).

In the ultrasound-guided subclavian vein group, four procedures resulted in primary puncture failure and required conversion to open internal jugular vein cut-down. The reasons for failure included small venous caliber in two patients, suboptimal ultrasound visualization due to positioning limitations in one patient, and anatomical challenges in one very low-weight neonate. All four converted cases occurred in patients weighing less than 2.5 kg. All cases were analyzed according to the intention-to-treat principle and remained in their originally assigned group.

Moreover, all hematoma cases were exclusive to the jugular group and occurred when the procedure duration exceeded 35 min. Subgroup comparison (< 35 vs. >35 min) demonstrated a meaningful association between prolonged procedure duration and hematoma occurrence (RR = 6.0; 95% CI: 1.1–32.4) (Fig. 3).

Fig. 3.

Incidence of hematoma according to procedure duration in the jugular group

During the study period, no clinically apparent signs of altered cerebral or regional venous drainage were observed following IJV cut-down, and no related adverse events were identified. However, because no dedicated neurological evaluation, Doppler ultrasonography, or imaging-based assessment of venous drainage was performed, these findings should not be interpreted as evidence that venous drainage was unaffected.

Discussion

The present study offers a focused appraisal of open jugular cutdown versus ultrasound-guided subclavian access for central venous catheterization in low-weight pediatric patients, emphasizing anatomical complexity, technical demands, and weight-related vulnerability. The prolonged operative time observed with the open jugular approach reflects the inherent challenges of surgical exposure and delicate tissue handling in neonates and small infants, as previously noted in similar pediatric cohorts [18]. In contrast, ultrasound guidance provides real-time visualization that facilitates accurate venipuncture with minimal tissue disruption, a benefit well supported in contemporary literature [19].

Importantly, there were no incidences of critical complications such as pneumothorax, hemothorax, major bleeding, arrhythmia, venous obstruction, infection, or mortality in either group. This absence of severe complications supports the fundamental safety of both approaches when performed by experienced teams. It aligns with prior pediatric studies indicating low rates of catastrophic events with proper technique and patient selection [20].

Four catheterization failures occurred in the ultrasound-guided subclavian group, though the difference was not statistically significant compared with open jugular access. Since all failures were observed in infants weighing less than 2.5 kg, a post-hoc subgroup analysis was performed. This analysis demonstrated lower procedural success via the subclavian route in infants under 2.5 kg. However, the 2.5 kg value should be interpreted only as a tentative clinical reference threshold rather than a definitive or universal cut-off for procedural decision-making, given the small subgroup size and limited number of events. Similarly, Karapinar et al. [21] reported comparable findings, suggesting that in younger pediatric patients, the risk of catheterization failure increases with the use of the subclavian vein, and consequently femoral or jugular cannulation should be considered instead. Nardi et al. [3] also described a significantly lower success rate for subclavian access compared to jugular or femoral routes in children weighing less than 5 kg, supporting our observation. Upper-limb edema occurred exclusively in the subclavian group and only among infants weighing less than 2.5 kg. While subgroup analysis identified a statistically significant association between low body weight and edema, this observation must be interpreted within the methodological constraints of the study, which compared two procedural strategies differing simultaneously in both venous access site (internal jugular vs. subclavian) and operative modality (open cutdown vs. ultrasound-guided percutaneous cannulation). As a result, the observed differences in catheterization failure and limb edema cannot be attributed solely to vein anatomy, reflecting a major dual confounding factor.

It is also noteworthy that no statistically significant differences were found between the two groups in other expected complications, including infection, major bleeding, and vascular events. These findings support the overall clinical feasibility of both approaches within the setting of this study, although they should not be interpreted as definitive evidence of equivalent safety under all circumstances. Accordingly, the choice of central venous access in low-weight pediatric patients should remain individualized, taking into account patient anatomy, procedural considerations, and operator experience [22, 23]. Although open cut-down of the internal jugular vein has been associated theoretically with impaired cerebral or regional venous drainage, no clinically apparent evidence of such complications was observed in our cohort. Specifically, no facial edema, clinical signs suggestive of increased intracranial pressure, or neurological deterioration were documented after IJV cut-down. However, because no dedicated neurological assessment, Doppler ultrasonography, or imaging-based evaluation of venous drainage was performed, the absence of clinically evident complications should not be interpreted as proof that venous drainage remained unaffected. Moreover, the 2-week follow-up period is insufficient for assessing long-term cerebral venous circulatory outcomes, representing another limitation that warrants explicit recognition. Given the limited sample size, this potential risk cannot be excluded and warrants further evaluation in prospective studies incorporating targeted neurological and imaging-based assessment.

No major adverse events—such as pneumothorax, hemothorax, bleeding, arrhythmia, catheter occlusion, infection, or mortality—occurred in the present cohort. Although catheter-related thrombosis was detected in both groups on routine two-week echocardiography, it did not impair catheter function and appeared to represent an expected, rather than technique-specific, phenomenon. Comparable observations have been described by Karapinar et al. [21], who similarly reported thrombosis without functional compromise, alongside complications that led them to favor jugular or femoral access in pediatric patients. Additional reports of catheter obstruction following ultrasound-guided subclavian placement [24] and the well-documented influence of operator experience on complication rates [25]. further underscore the procedural sensitivity of central venous access in infants. The very low complication rates observed here likely reflect the involvement of a highly experienced operator, and the fact that all procedures were performed by a single, highly experienced clinician should be acknowledged as a limitation to external generalizability. The very low complication profile in our study likely reflects performance by a highly experienced operator. It is crucial to acknowledge that the exceptionally low complication profile observed in our study may be partially attributable to the fact that all procedures were performed by a single, highly experienced operator. Consequently, these findings should be interpreted with caution, as the high safety profile and procedural success rates may not be fully generalizable to clinical settings or centers with varying levels of practitioner expertise.

Finally, the relationship between procedural duration and hematoma formation warrants careful interpretation. All hematomas in the jugular group occurred in procedures exceeding 35 min. However, because multivariable regression analysis was not performed to adjust for potential confounders, prolonged procedural time cannot be confirmed as an independent risk factor for hematoma. The current finding reflects a univariate association only, and causal inference is not warranted. Furthermore, the study design does not allow separation of whether hematoma formation was influenced primarily by venous access site, surgical modality, or the interaction between them. These findings highlight the importance of targeted operator training, ongoing skill assessment, and broader adoption of adjunctive technologies such as real-time ultrasonography to optimize outcomes and minimize complications [23].

Conclusion

Both approaches were generally safe, with no major adverse events in either group. Ultrasound-guided subclavian access was associated with shorter procedure time, whereas hematoma occurred only in the jugular group and catheterization failure and upper-limb edema were seen only in low-weight infants in the subclavian group. However, because this study compared two combined strategies that differed in both access site and technique, the independent effect of either factor cannot be determined. In addition, the subgroup findings in infants weighing < 2.5 kg were based on few events and should be considered hypothesis-generating. Therefore, these results suggest possible differences between the two approaches but do not justify definitive weight-based recommendations.

This study has several important limitations. Most notably, the study design involves the simultaneous comparison of two distinct variables: the access technique (open versus ultrasound-guided) and the venous access site (internal jugular versus subclavian vein). This concurrent comparison complicates the independent interpretation of each factor and increases the risk of confounding, making it difficult to attribute the observed differences in outcomes solely to either the technique or the access site. Nevertheless, the primary objective of the study was to evaluate two commonly applied clinical strategies as they are routinely performed in our institution, based on surgeon preference, patient condition, and available resources, rather than to isolate the pure effect of a single technique. Although this approach represents a methodological limitation, it reflects real-world clinical practice in low-weight neonatal and infant populations. Additionally, the non-randomized selection of the access route may have been influenced by clinical, anatomical, or operator-related factors. Future studies employing randomized designs, larger sample sizes, and comparisons of different techniques at a fixed venous site are warranted to more clearly delineate the independent effects of access technique and access location. In addition, procedure-related failures requiring conversion occurred, particularly in very low-weight infants, and should be considered a practical limitation of the ultrasound-guided subclavian approach that may influence outcome interpretation.

Abbreviations

ANOVA

Analysis of variance

CVC

Central venous catheter

IRCT

Iranian registry of clinical trials

ITT

Intention–to–treat

LLM

Large language model

REC

Research ethics committee

SPSS

Statistical package for the social sciences

Authors' contributions

All authors contributed to the study design, data collection, manuscript preparation, and final revision.

Funding

This study was financially supported by Tabriz University of Medical Sciences.

Data availability

The datasets used and analyzed during the current study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

Written informed consent was obtained from all participants after providing detailed explanations regarding the nature of the study. Strict confidentiality was maintained throughout the research, and no personal or identifying information about the patients was disclosed at any stage. It is noteworthy that all procedures performed in this study were solely for therapeutic purposes, with no additional financial burden imposed on the patients. Parents were informed that both catheterization methods were equally beneficial for central venous access and that there would be no difference in cost between the two techniques. The study protocol was approved by the Ethics Committee of Tabriz University of Medical Sciences under the code IR.TBZMED.REC.1402.610, and the clinical trial was registered in the Iranian Registry of Clinical Trials (IRCT) with the code IRCT20230901059317N1/ https://irct.behdasht.gov.ir/trial/72449. This study was conducted in full accordance with the principles of the Declaration of Helsinki. Given that the authors of the present study are nonnative English speakers and minor linguistic inaccuracies might have occurred during the initial drafting process, the manuscript was subsequently refined using a Large Language Model (LLM) such as ChatGPT to improve clarity and language quality. The authors affirm that this tool—and any similar language based applications—was used solely for stylistic enhancement and grammatical correction, and not for data analysis, primary writing, or any other component of the research process.

Consent for publication

There are no patient personal data included in this manuscript.

Competing interests

The authors declare no competing interests.