Comparison between direct puncture trocar and Seldinger technique in ultrasound-guided drainage of pleural fluid collections (DIESEL study): A prospective observational study

Abstract

Background and Objective:

There is a paucity of data comparing the direct puncture trocar technique and the Seldinger technique for the drainage of pleural fluid collections with respect to technical and clinical success rates and complication rates.

Methods:

The pleural fluid collections were drained using either the direct puncture trocar or the Seldinger technique by a single operator under ultrasound guidance. Technical success rates, clinical success rates, pain scores determined using a visual analog scale, complication rates, and mortality rates were compared between the two techniques.

Results:

A total of 94 patients were included in the analysis. Technical success was achieved in 97.87% of cases in the Seldinger group and 91.48% in the direct puncture trocar group (P = 0.30). Clinical success was achieved in 90.09% of cases in the Seldinger group and 89.13% in the direct puncture trocar group (P = 0.50). Patients experienced more pain with the Seldinger technique in the immediate periprocedural period (median visual analog scale [VAS] score of 6) as compared to the direct puncture trocar group (median VAS score of 5) [P = 0.003]. Direct puncture trocar technique was significantly faster (mean procedure duration of 4.30 ± 2.41 min (direct puncture trocar group) vs 7.89 ± 2.12 min (Seldinger group) [P = 0.00]).

Conclusion:

The direct puncture trocar technique appears to provide comparable technical and clinical success to the Seldinger technique for ultrasound-guided pleural drainage, with shorter procedural duration and lower immediate pain perception. Larger randomized studies are required to confirm these findings.

INTRODUCTION

Fluid collections within the pleural cavity can arise from various etiologies, including infection, inflammation, trauma, cardiogenic shock, postoperative state, and iatrogenic causes.[1] Pleural fluid collections may be broadly divided into exudative and transudative, based on the criteria proposed by Light et al.[2] The management of pleural fluid collections depends on the nature of the collection and the patient’s symptoms, with drainage recommended for infected collections, hemothorax, and massive pleural effusions that compromise respiratory function.[3] Traditionally, pleural fluid collections requiring drainage have been managed by placing large-bore chest drains (>28 F).[4] In recent years, there has been a shift in the approach to drainage of pleural fluid collection with preference for smaller catheters (<16 F) due to better tolerance, less pain, and safer insertion under image guidance.[4] Placement of a percutaneous catheter into the pleural cavity may be performed under ultrasound or computed tomography guidance. Ultrasound offers the distinct advantage of providing real-time feedback during catheter placement, eliminating the risk of radiation exposure to both the patient and the operator.[5] Furthermore, using ultrasound guidance, bedside placement of the catheter in critical care units and the emergency department is feasible.[6] There are two distinct techniques for placing a percutaneous catheter into a pleural collection: the Seldinger technique and the direct puncture trocar technique. The Seldinger technique requires the puncture of the chest wall using a needle for access into the pleural fluid collection, with subsequent introduction of a guidewire, followed by serial dilatation of the tract over the guidewire and placement of a catheter into the pleural cavity.[7] On the other hand, the direct puncture trocar technique is straightforward: the catheter, along with the inner trocar, is directly introduced into the fluid collection without the need for a needle, guidewire, or fascial dilators.[7] While both techniques are feasible for placing a percutaneous catheter into a pleural fluid collection, it is unclear which offers better technical and clinical outcomes in terms of successful catheter placement within the fluid collection and a more favorable risk profile. There is a paucity of prospective studies comparing the head-to-head effectiveness of the two techniques for percutaneous catheter placement in the management of pleural fluid collections. This study was conducted with a specific research question: which of the two techniques—the direct puncture trocar or the Seldinger technique—has a better technical success rate for ultrasound-guided percutaneous catheter drainage of pleural fluid collections. Additionally, we sought to determine the differences in clinical success rates and complication rates between the two techniques.

MATERIALS AND METHODS

This study was conducted prospectively over 2 years. Written and informed consent was obtained from the patients’ next of kin before the procedures, as well as for the collection of data for this study.

Patient selection

Consecutive patients who were referred to our facility for ultrasound-guided percutaneous catheter drainage of pleural fluid collections were included in the study. The indication for percutaneous drainage of a fluid collection was established by a senior clinician with >10 years of experience in the management of chest and pleural diseases. The feasibility of percutaneous drainage using ultrasound as the imaging modality was established by a consultant interventional radiologist with >10 years of experience in percutaneous ultrasound-guided procedures. The same operator performed all the procedures. The size of the catheter deployed into the pleural fluid collection was at the operator’s discretion. Patients with large-bore chest drains or pleural catheters already in place elsewhere, requiring further pleural drainage procedures, were excluded from the study. Additionally, patients with pneumothorax, hydropneumothorax, or pyopneumothorax, those with general contraindications to image-guided percutaneous procedures, and pregnant females were excluded.

Patient allocation strategy

Patients were enrolled consecutively and allocated to either the direct puncture trocar technique or the Seldinger technique, using a predefined alternating allocation sequence (1:1 ratio). To minimize selection bias, allocation was performed before procedural planning and was not influenced by patient characteristics, anatomical complexity, or ultrasound findings. All procedures were performed by a single experienced operator to reduce inter-operator variability. However, given the non-randomized allocation and the potential for residual confounding, a propensity score matching (PSM) analysis was prespecified to adjust for baseline differences between the groups. The propensity score was derived using a multivariable logistic regression model that incorporated clinically relevant covariates, including age, gender, diagnosis, indication for drainage, collection size and depth, catheter size, and anatomical approach. Matching was performed using a nearest-neighbor 1:1 method without replacement, with a predefined caliper width. Covariate balance after matching was assessed using standardized mean differences (SMDs), with a threshold of <0.1 considered acceptable. This combined approach (systematic allocation with post hoc adjustment) was used to enhance comparability between groups while maintaining the feasibility of a prospective real-world study design.

General considerations for the percutaneous drainage of pleural fluid collections

The patients were placed in the lateral decubitus position, with the side of interest up. The site of catheter insertion was determined by the operator based on the site where the maximum depth of pleural fluid was obtained using a curvilinear ultrasound probe (frequency of 3–5 MHz), through the intercostal window. In most cases, the site of entry into the pleural cavity was attempted in the mid-axillary line; however, any variation in this approach was left to the operator’s discretion, depending on feasibility. The intercostal space was pierced in the center of the space to avoid the neurovascular structures at the margins of the adjacent ribs. All procedures were performed using standard aseptic technique, and written informed consent was obtained from the patients’ next of kin. All the procedures were carried out under local anesthesia, after injection of 2% lignocaine (without adrenaline). For patients requiring drainage of pleural fluid collections in the intensive care unit, the procedure was performed at the bedside; otherwise, it was performed in the interventional radiology facility.

Direct puncture trocar technique

The site of entry into the pleural fluid collection was prepped and draped using standard sterile technique, and a stab incision was created using an 11-number surgical blade. A percutaneous drainage catheter (pigtail or Malecot) of appropriate size, as chosen by the operator, was then advanced through the stab incision, into the pleural fluid collection under ultrasound guidance. Once the tip of the trocar needle was visualized in the collection, the inner trocar was removed, and the catheter was advanced into the collection to form the pigtail or Malecot locking mechanism at the distal end of the catheter. With the catheter in place, the position was confirmed by both ultrasound and aspiration of the contents.

Seldinger technique

The site of entry into the pleural fluid collection was prepped and draped using standard sterile technique, and a stab incision was created using an 11-number surgical blade. The collection was assessed under ultrasound guidance with an 18-G needle. After the position was confirmed in the collection with ultrasound guidance, a 0.035-in. guidewire was advanced into the collection through the needle. After this, the needle was removed, and the access tract was serially dilated using fascial dilators. The tract was dilated up to the size of the drainage catheter to be deployed. After serial dilatation of the tract, the drainage catheter was threaded over the guidewire and advanced under ultrasound guidance into the fluid collection. Once the position was confirmed in the collection, the guidewire and the inner straightener of the catheter were removed to form the pigtail or Malecot locking mechanism at the catheter’s distal end. The final position of the catheter was confirmed by ultrasound and by free aspiration of the fluid.

After placement of the catheter

In all cases, the catheter was sutured to the skin with nylon (2-0) or silk (2-0) sutures and connected to a drainage bag with an underwater seal mechanism for gravity-dependent drainage. A chest X-ray was performed after 2 h in all cases to evaluate for a pneumothorax, and additional imaging was performed as indicated in each case. Any other complications arising after the procedure were documented, and appropriate investigations and interventions were performed. Assessment of pain during the procedure and at 48 h after the procedure was performed using the visual analog scale (VAS), with a score of 0 indicating no pain and 10 indicating unbearable pain.[8] Complications during and after the procedure were documented using the modified CIRSE (Cardiovascular and Interventional Radiological Society of Europe) classification system and are shown in Table 1.[9]

Table 1.

Grading of the procedure-related complications as per the modified CIRSE classification

Grade		Definition		Interpretation
1a		Complication during procedure, resolved within the same session; intended procedure completed		No additional therapy, no sequelae, no deviation from normal course
1b		Complication during procedure, resolved within the same session; procedure not completed		Technical failure due to a complication
2		Prolonged observation or hospitalization <48 h		No additional therapy; no sequelae
3a		Additional therapy or hospitalization >48 h but <2 weeks		No permanent sequelae
3b		Additional therapy or hospitalization >2 weeks		Reflects higher resource utilization; no permanent sequelae
4		Permanent mild sequelae		Patient remains independent (can resume work/life)
5		Permanent severe sequelae		Requires assistance in daily living or long-term care
6		Death		Procedure-related mortality

CIRSE=Cardiovascular and Interventional Radiological Society of Europe

Complication assessment and reporting

All procedure-related complications were prospectively recorded and classified according to the modified CIRSE classification system.

Complications were categorized based on the following:

Timing

• Intraprocedural (occurring during the procedure)

• Early post-procedural (within 48 h)

• Delayed complications (up to 8-week follow-up).

Severity (CIRSE Grades 1–6)

• Minor complications: Grades 1–2

• Major complications: Grades ≥3.

Attribution

• Procedure-related (directly attributable to catheter insertion)

• Possibly related

• Unrelated (e.g., disease progression).

All complications were independently reviewed and graded based on clinical records, imaging findings, and need for additional intervention. Complication rates were reported as overall incidence, minor vs major complications, and grade-wise distribution. Only complications occurring in technically successful procedures were included in the primary comparison analysis. Transient, self-limiting events (e.g., minor hemorrhagic aspirate not requiring intervention) were classified as Grade 1, while complications requiring additional therapy or prolonged hospitalization were graded accordingly.

Follow-up

The patients were followed up weekly for 8 weeks after the procedure. At each follow-up, the position of the catheter in the pleural cavity was determined with ultrasound or through the assessment of fluid column movement in the drainage bag. The drain output status and the maximum depth of the pleural collection were measured with ultrasound. Catheter-related complications, such as blockage, dislodgement, and pericatheter leak, were also documented, and remedial measures were taken as appropriate and on a case-by-case basis. In the event of any death after the procedure, it was documented as occurring within 30 days after the procedure or >30 days after the procedure.

Operational definition of terms

The operational definition of terms used for this study is summarized in Table 2.

Table 2.

Operational definition of terms used in this study

Term		Definition
Technical success		Successful percutaneous ultrasound-guided placement of the catheter into the pleural fluid collection, as confirmed on ultrasound, and free aspiration of fluid content
Clinical success		Resolution of the clinical and/or laboratory parameter for which the percutaneous drainage of pleural fluid collection was necessitated. For the objective assessment of clinical success, the following definitions were considered: 1. Radiological: >50% reduction in the volume of the collection at 1 week after the intervention. This also applied for malignant pleural effusion, where prolonged catheter indwelling may be required due to the nature of the disease 2. Clinical: Resolution of the chief clinical symptoms that necessitated drainage of the pleural fluid collections 3. In cases with sepsis: Resolution of sepsis is defined as: afebrile status (<38°C for ≥48 h), hemodynamic stability without vasopressors, ≥50% reduction in WBC count or normalization, significant decline in CRP (≥50%), and radiological reduction of pleural collection (≥50% volume) 4. No requirement for escalation (repeat drainage/surgery
Duration of procedure		Time interval from the start of access into the pleural fluid collection using ultrasound guidance to confirmation of the catheter position in the pleural fluid collection using direct visualization with ultrasound and aspiration of fluid. The duration of the procedure in all the cases was measured by an independent observer not involved in the procedure using a digital wall clock in the procedure room.
Number of attempts		A maximum of three attempts was made before switching over to the alternative technique.
Pain assessment (immediately after the procedure and at 48 h after the procedure)		Semiquantitative assessment of the pain felt by the patient using a visual analog scale [ranging from no pain (0) to unbearable pain (10)]
Failure of the technique		Inability to successfully place the catheter under ultrasound guidance into the pleural fluid collection after three consecutive attempts
Failure of the procedure		Inability to successfully place the catheter under ultrasound guidance into the pleural fluid collection after three consecutive attempts of each of the two techniques used sequentially in the same sitting.

WBC=white blood cells, CRP=C-reactive protein

Primary objective

The primary objective of the study was to determine the differences in the technical success rates between the two techniques.

Secondary objectives

1. To determine the differences in clinical success rates between the two techniques

2. To determine the differences in procedure duration between the two techniques

3. To determine the differences in complication rates between the two techniques

Sample size

The sample size for this prospective observational study was determined based on feasibility and anticipated patient recruitment over the study period, rather than through formal hypothesis testing. A total of 94 patients (47 in each group) were included. Previous literature suggests technical success rates of approximately 90–95% for the Seldinger technique and 70–90% for the trocar technique. With this sample size, the study is expected to provide reasonably precise estimates of success rates and complication rates in both groups. Assuming an expected success rate of approximately 90%, a sample size of 47 patients per group yields a 95% confidence interval with a margin of error of approximately ±8–10%, which is considered acceptable for an exploratory comparative analysis. Therefore, the study is adequately powered to detect large, clinically meaningful differences between the two techniques.

Statistical analysis

To account for potential bias in patient selection for drainage of pleural fluid collections using either the direct trocar or the Seldinger technique, a PSM analysis was performed using the nearest-neighbor method (1:1 matching with no replacement). Logistic regression was used to compute propensity scores. SMD was calculated for each covariate before and after PSM. An SMD of <0.1 was considered a threshold for adequate balance. The median and interquartile range (IQR) represent the categorical variables and ordinal variables, while continuous variables are represented by the mean and standard deviation. Statistical significance is maintained at the threshold of P < 0.05. The statistical differences in the categorical variables between the two groups, namely the direct puncture trocar and the Seldinger technique, were determined using the Chi-squared test. The differences in ordinal variables between the two groups were computed using the Mann–Whitney U test. The differences in continuous variables between the two groups were assessed using an independent t-test. The normality of continuous variables was tested with the Kolmogorov–Smirnov test. The statistical analysis was conducted using R 4.5.1 for Windows and the XLSTAT 2025 extension for Microsoft Excel.

RESULTS

This study included 94 patients who underwent percutaneous ultrasound-guided drainage of pleural fluid collections. In each of the two groups, that is, the direct puncture trocar group and the Seldinger group, 47 patients were included for analysis. A summary of the allocation of the patients into each of the groups and the corresponding results is shown in the flow diagram in Figure 1.

Figure 1.

Flow diagram depicting the allocation of cases into the two groups and the summary of corresponding results

Propensity score-matching analysis

PSM was performed using the nearest-neighbor method with 1:1 matching without replacement, with a caliper width of 0.173. A total of 37 matched pairs (n = 74) were obtained, and the c-statistic (area under the curve) was 0.726, suggesting an acceptable discrimination. The SMDs before and after PSM for each of the covariates are shown in Table 3, and the corresponding Love plot is shown in Figure 2.

Table 3.

Balance table showing the standardized mean differences before and after PSM for each of the covariates

Variable		SMD before		SMD after
Age		−0.04		0.03
Gender		−0.13		0.05
Diagnosis		−0.05		−0.06
Side		−0.17		0.0
Max depth		−0.03		0.02
Skin–center distance		0.4		0.16
Intercostal approach		−0.49		−0.19
Anatomical approach		0.04		0.0
Catheter size		−0.17		−0.16
Primary indication		−0.3		−0.04

PSM=propensity score matching, SMD=standardized mean differences

Figure 2.

Love plot showing the distribution of the standardized mean differences (SMDs) before (blue dots) and after (orange dots) propensity score matching

After PSM, most covariates were well matched, with SMDs of <0.1. However, a slight residual imbalance was still noted in three covariates—skin-to-center distance, catheter size, and the site of intercostal approach—where the SMD was slightly above the threshold. However, with a c-statistic of 0.726, the model was deemed acceptable.

Analysis of continuous and normally distributed variables

There were no statistically significant differences in the mean age of the two groups. Furthermore, the mean maximum depth of the fluid collection and the mean distance between the skin surface and the center of the fluid collection were not significantly different between the two groups. The direct puncture trocar technique was found to be significantly faster at achieving successful catheter placement within the fluid collection than the Seldinger technique. Among patients in the direct trocar group, the mean duration of catheter indwelling was 41.3 days as compared with 39.08 days for the Seldinger group, and the difference was not statistically significant. A summary of the statistical analysis of the continuous, normally distributed variables is presented in Table 4.

Table 4.

Summary table showing the differences in the normally distributed continuous variables between the direct puncture trocar and Seldinger groups

Parameter		Direct group (n=47)		Seldinger group (n=47)		P (two-tailed)		Inference
Age (years)		47.7±12.94		48.2±13.41		0.85		Not significant
Maximum depth of fluid collection (cm)		6.34±1.09		6.38±1.40		0.87		Not significant
Distance from skin to center (cm)		4.25±1.07		3.82±1.09		0.06		Not significant
Duration of the procedure (min)		4.30±2.41		7.89±2.12		0.00		Significant
Number of days of catheter indwelling (mean [SD])		41.3±4.2		39.08±13.05		0.22		Not significant

SD=standard deviation

Analysis of categorical variables

There were 26 male patients in the direct group (55.3%) and 27 in the Seldinger group (57.4%); the difference in gender distribution between the groups was not statistically significant. The most common diagnosis in the direct group was empyema (44.7%) and malignant pleural effusion (44.7%), followed by acute pancreatitis (6.38%) and traumatic hemothorax (4.25%). In the Seldinger group, the most common diagnoses were empyema (55.3%), followed by malignant pleural effusion (31.9%), hemothorax (6.4%), and acute pancreatitis (6.4%). The difference between the two groups in terms of diagnosis of the underlying condition was not significant. Breathlessness (48.93%), sepsis (46.8%), and hemothorax (4.25%) were the primary indications for pleural fluid drainage in the direct group. Similarly, breathlessness (51.03%), sepsis (42.5%), and hemothorax (6.38%) were the primary indications for pleural fluid drainage in the Seldinger group. The differences in the primary indication for drainage of pleural fluid between the groups were not significant. Most pleural fluid drainage procedures were performed on the right side (57.4% in the direct group and 53.2% in the Seldinger group; P = 0.17). In most cases, the site of entry into the pleural fluid collection was through the mid-axillary line in both groups (57.4% in the direct group vs 55.3% in the Seldinger group; P = 0.35). In the direct group, pleural fluid drainage was performed through the fifth intercostal space in most of the cases (48.9%), while in the Seldinger group, most of the pleural fluid drainage was performed through the fifth and sixth intercostal spaces (34.04% at each intercostal level). The differences between the group with respect to the intercostal space used for entry into the pleural fluid collection were not significant.

Technical success – Catheter placement within the pleural fluid collection was successful in 91.48% of the cases using the direct puncture trocar technique and 97.87% of the cases using the Seldinger technique. However, the difference was not statistically significant (P = 0.30). In either group, for cases in which successful catheter placement was not possible after three consecutive attempts with a particular technique (direct puncture trocar or Seldinger technique), drainage was performed using the alternative technique or a large-bore intercostal chest tube.

Clinical success: Among patients who underwent successful drainage of the pleural fluid collection using the initial technique chosen by the operator for drainage, clinical success was achieved in 90.09% in the direct puncture trocar group and 89.13% in the Seldinger group; however, the difference did not reach statistical significance (P = 0.50).

Complications (during or immediately after the procedure) were noted in eight patients (18.18%) in the direct group (among technically successful cases) and 12 patients (26.08%) in the Seldinger group (among technically successful cases). In both groups, excluding cases of traumatic hemothorax, hemorrhage within the catheter aspirate after the procedure was the most common complication (13.63% in the direct group and 15.21% in the Seldinger group). In all these cases, the hemorrhage was transient and subsided with expectant observation alone, without the need for any further intervention. The difference in complication rates between the two groups did not reach statistical significance (P = 0.69).

At follow-up, conducted 8 weeks after drainage catheter insertion, no complications were noted in 90.9% of cases in the direct group and 89.13% of patients in the Seldinger group. Dislodgement of the catheter was noted in 4.54% of cases in the direct group and 4.35% of cases in the Seldinger group. These patients were counted as treatment failures and subsequently managed with large-bore intercostal chest tube drainage. Nineteen patients (43.18%) in the direct trocar group had a catheter still in place at 8 weeks of follow-up (15 with malignant pleural effusion and 4 with empyema). In the Seldinger group, 21 patients (45.65%) had an indwelling catheter at 8 weeks of follow-up (17 patients with malignant pleural effusion and 4 with empyema). The difference between the groups in the proportion of patients with an indwelling catheter at 8 weeks of follow-up was not significant. Death within 30 days of catheter placement occurred in one patient in the direct group (2.26%) and two patients in the Seldinger group (4.35%). Death after 30 days of catheter insertion was reported in one patient in the direct group (2.26%) and one patient in the Seldinger group (2.10%). The differences in complication frequency between the groups were not statistically significant (P = 0.95). A summary of differences in categorical variables between the two groups is presented in Table 5.

Table 5.

Summary table showing the differences between the direct puncture trocar and Seldinger groups with respect to the categorical variables

Parameter		Direct group (n=47)		Seldinger group (n=47)		P (two-tailed)		Inference
Gender (N)						0.83		Not significant
• Male • Female		26 21		27 20
Diagnosis (N)						0.62		Not significant
• Empyema • Malignant pleural effusion • Hemothorax • Acute pancreatitis-associated pleural effusion		21 21 02 03		26 15 03 03
Primary indication for pleural fluid drainage (N)						0.85		Not significant
• Sepsis • Breathlessness • Hemothorax		22 23 02		20 24 03
Side of involvement (N)						0.17		Not significant
• Right • Left		27 20		25 22
Anatomical landmark of entry (N)						0.35		Not significant
• Mid-clavicular line • Anterior axillary line • Posterior axillary line • Mid-axillary line		05 04 11 27		02 09 10 26
Intercostal space (N)						0.46		Not significant
• 4th • 5th • 6th • 7th • 8th		05 23 13 04 02		04 16 16 09 02
Technical success (N)						0.30		Not significant
• Yes • No		44 03		46 01
Clinical success (N)						0.50		Not significant
• Yes • No		40/44 (90.90%) 04/44 (9.10%)		41/46 (89.13%) 05/46 (10.87%)
Complications during or immediately after the procedure (N)						0.69		Not significant
• Pneumothorax • Hemorrhagic aspirate • Vasovagal attack • No complication		01/44 (2.27%) 06/44 (13.63%) 01/44 (2.27%) 36/44 (81.81%)		03/46 (6.52%) 07/46 (15.21%) 02/46 (4.34%) 34/46 (73.91%)
Follow-up (N)						0.95		Not significant
• No complication • Catheter dislodgement • Death within 30 days of the procedure • Death >30 days after the procedure		40/44 (90.90%) 02/44 (4.54%) 01/44 (2.26%) 01/44 (2.26%)		41/46 (89.13%) 02/46 (4.35%) 02/46 (4.35%) 01/46 (2.10%)
Proportion of patients with an indwelling catheter at 8 weeks		19/44 (43.18%)		21/46 (45.65%)		0.32		Not significant

Analysis of ordinal variables

The pain score as determined by the VAS immediately after the catheter insertion was found to be significantly higher in the Seldinger group as compared with the direct puncture trocar group (median VAS score of 6 in the Seldinger group [IQR = 3–6] vs median VAS score of 5 in the direct group [IQR = 5–7]; P = 0.003). However, the VAS score difference between the groups was not significant at 48 h after the procedure (median VAS score of 2 in the direct group [IQR = 1–3] vs median VAS score of 2 in the Seldinger group [IQR = 1–2]). There were no significant differences between the groups regarding the grade of complication in the immediate periprocedural period. Additionally, no significant differences were observed between the two groups in terms of catheter size used or the number of attempts required for successful catheter placement within the pleural fluid collections. The findings of the analyses of differences in ordinal variables between the groups are summarized in Table 6.

Table 6.

Summary table showing the differences between the direct puncture trocar and Seldinger groups with respect to the ordinal variables

Parameter		Direct group (n=47)		Seldinger group (n=47)		P (two-tailed)		Inference
Pain score (VAS) immediate [median (interquartile range)]		5 [3,6]		6 [5,7]		0.003		Significant
Pain score (VAS) at 48 h [median (interquartile range)]		2 [1,3]		2 [1,2]		0.81		Not significant
Grade of complication during or immediately after the procedure (median [interquartile range])		0 [0,0]		0 [0,0]		0.60		Not significant
Size of catheter (median [interquartile range])		12 [10,12]		12 [12,14]		0.24		Not significant
Number of attempts (median [interquartile range])		1 [1,1]		1 [1,1]		0.95		Not significant

VAS=visual analog scale

DISCUSSION

The Seldinger technique and the direct puncture trocar technique are the two techniques in vogue for percutaneous catheter insertion into fluid collections and pneumothoraces. While the Seldinger technique has been theoretically considered to be safer for insertion of small-bore drainage catheters into the pleural cavity, probably due to a smaller initial needle puncture and placement of the catheter over the guidewire, there has been apprehension regarding the risk of vascular injury and deeper penetration. However, with image guidance and proper technique, the trocar technique may be safe and much faster in achieving a successful catheter placement.[10] This may be useful in situations where the patient is unstable and cannot tolerate a longer procedure. Only a few studies have compared the two techniques for drainage of chest collections, examining technical and clinical success, periprocedural complication rates, and follow-up complications. In a prospective study by Congedo et al.,[11] the Seldinger technique was used to place a 12-F chest drain in 72 patients, and the trocar technique was used to insert a 12-F chest drain in 45 patients. The study concluded that there were no statistically significant differences between the groups in periprocedural pain, procedure duration, or clinical success in draining pleural effusions. Another retrospective study compared the single-step trocar technique with the modified Seldinger technique in the drainage of pleural fluid. The study included only 38 patients (16.5%) who underwent the modified Seldinger technique, compared with 201 cases (86.5%) who underwent the single-step trocar technique. The authors used the Seldinger technique only after the trocar technique had failed. The authors concluded that the direct trocar technique was faster and easier; however, if the direct technique failed, the Seldinger technique could be a viable alternative for placing the pleural catheters.[7] In the present study, we included consecutive patients who required ultrasound-guided percutaneous catheter drainage of pleural fluid collections for various indications, all performed by a single operator, to negate inter-operator differences and bias. To account for potential bias in patient allocation to one of the two groups (i.e., Seldinger vs direct trocar), a PSM analysis was performed. PSM using logistic regression yielded an acceptable balance across major covariates between the groups. Although three covariates—skin-to-center distance, catheter size, and intercostal space used for the approach—were marginally imbalanced between the groups, subsequent analyses showed no significant difference between the groups for these three covariates. This reflects the limitation of using a non-randomized design in this study. However, because the model showed statistical adequacy (c-statistic of 0.726), this marginal imbalance may not confound the study’s results.

The primary objective of the study was to determine the differences in technical success rates between the two groups. Our data suggest that there was no significant difference in technical success rates between the two techniques for percutaneous pleural catheter placement. There were failures in both groups (although no statistically significant difference was found). In three patients in the direct trocar group, the catheter could not be placed successfully into the pleural fluid collection. In all three cases, the catheter could not be successfully advanced through the intercostal spaces after three consecutive attempts. Subsequently, two of these cases were managed with the Seldinger technique, and one received intercostal chest tube placement; none were included in further analysis in this study. In one patient in the Seldinger group, the guide wire kinked at the skin entry point during the first attempt. In subsequent attempts after replacing the guidewire, the catheter could not be advanced into the collection over the guidewire, despite adequate tract dilatation. This case was further managed with tube thoracostomy. Again, considering clinical success, no significant differences were observed between the groups in achieving the clinical endpoint of resolution of the chief or principal indication warranting drainage of the pleural fluid collection. The direct trocar technique resulted in significantly faster placement of the pleural catheter compared to the Seldinger technique. This is largely due to the inherent nature of the two techniques: Seldinger is a multistep technique, while the direct trocar is a single-step technique.[7,11] More importantly, there were no significant differences between the groups in terms of rates of immediate periprocedural complications as well as delayed complications on follow-up. Our data do not suggest a higher risk of pneumothorax, hemothorax, or vasovagal attack in either group. During the follow-up period of up to 8 weeks after the initial placement of the pleural catheter, no significant differences were noted between the groups in terms of catheter dislodgement rates and mortality (i.e. all-cause mortality within and after 30 days of the procedure). In the direct trocar group, one patient died, and in the Seldinger group, two patients died within 30 days of the intervention. The patient in the direct trocar group had a diagnosis of empyema thoracis and was in septic shock. Death occurred on the sixth day after the intervention due to complications related to sepsis. The death was not attributed to an intervention-related complication. In the Seldinger group, one patient had a diagnosis of acute necrotizing pancreatitis with multi-organ dysfunction syndrome, and the pigtail catheter was placed due to a large left-sided pleural effusion while the patient was in the intensive care unit (ICU). The patient died on the third day after the intervention, likely due to underlying disease progression. Another patient in the Seldinger group was diagnosed with metastatic ovarian carcinoma with pleural deposits. A right-sided pleural catheter was placed for the management of malignant hemorrhagic pleural effusion. The patient died 12 days after placement of the catheter, again due to disease-related complications. In all these cases, death within 30 days of intervention was not attributed to the procedure itself, but rather to the course and complications of the underlying disease. These findings suggest that the complications associated with draining the pleural fluid collection may result from an interplay of various factors; however, complications may occur with both techniques, and any single technique may not necessarily confer a higher risk. It is also pertinent to note that all complications in the immediate post-procedure period were self-limiting and did not require further management in any patient in either group. Another aspect of the study involved assessing periprocedural pain, specifically the immediate post-procedure pain evaluation using the VAS, as well as at 48 h after the procedure. While VAS is a semiquantitative tool for pain assessment, it has been widely used in the literature to assess procedure-related pain. Our study suggests that, in the Seldinger group, patients reported higher VAS scores than in the direct trocar technique group in the immediate post-procedure assessment, whereas there were no significant differences between the groups at 48 h. This may be explained by the use of multiple and serial fascial dilators for dilatation of the drainage tract over the wire, which may lead to a more severe perception of pain in the Seldinger group; subsequently, with adequate analgesia and an adaptive response to pain, the perception of pain may be reduced, and hence, no significant differences were found at 48 h after the procedure.[12]

Strengths of the study

• Prospective design

• Real-world clinical applicability

• PSM analysis

• Pain assessment at two time points

• 8-Week follow-up

• Relevant to bedside pulmonology practice.

Clinical relevance for Indian practice

This study is particularly relevant to Indian settings where:

• Bedside procedures are common.

• Resource optimization is important.

• Procedure duration impacts ICU workflow.

• Pain perception influences patient satisfaction.

• If validated in larger randomized studies, the direct trocar technique may represent a time-efficient alternative without compromising safety.

Limitations

The study is not without limitations. The study included consecutive patients, and no randomization was performed; nevertheless, a PSM analysis was conducted to account for potential bias in patient allocation between the two groups. PSM showed acceptable balance in the covariates between the groups; however, three covariates (skin-to-center distance, catheter size, and intercostal level for the approach) showed slight imbalance (marginally above an SMD threshold of <0.1). This underscores the limitation of non-randomized allocation in this study; nonetheless, we did not find any statistically significant differences for these marginally unbalanced covariates between the groups. Ultimately, a larger randomized study may be more suited to evaluate the influence of these covariates on the clinical and technical success rates between the groups. An operator-defined limit of three attempts was applied to analyze the technique’s failure, as a greater number of attempts might have led to success. Additionally, patients who underwent a switch-over of the technique—initially managed with the direct trocar group and subsequently with the Seldinger technique, and vice versa—were excluded from the analysis. This exclusion was necessary because these cases could have been counted as successful for the subsequent technique, even though the initial placement of the pleural drainage catheter was unsuccessful. However, it is pertinent to note that there was no crossover from the Seldinger technique group to the direct trocar group; therefore, comparing crossover rates between the groups was not feasible. Furthermore, patients who switched to tube thoracostomy were lost to follow-up, and we could not determine their subsequent outcomes. For the same reason, an intention-to-treat analysis was not performed, and results were reported based on a per-protocol analysis. As follow-up data for switch-over cases and cases under alternate management were unavailable, these cases were also excluded from analyses of clinical success rates and complication rates. Finally, in this study, all the procedures were performed by a trained interventional radiologist. There may be a learning curve among physicians who are beginners for both the Seldinger and direct trocar technique, particularly with hand–eye coordination and localization of needle and catheter on ultrasound. This may lead to variable results among different groups of practitioners.

CONCLUSION

The direct puncture trocar technique appears to provide comparable technical and clinical success to the Seldinger technique for ultrasound-guided pleural drainage, with shorter procedural duration and lower immediate pain perception. Larger randomized studies are required to confirm these findings.

Ethical approval

The study was approved by the institutional ethical committee of AIIMS, Bathinda (IEC approval number IEC/AIIMS/BTI/07/73).

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.