Incidence and Characteristics of Catheter-Related Thrombosis in Patients With Temporary Femoral Dialysis Catheters: A Prospective Observational Study

Introduction

Extracorporeal treatments, such as renal replacement therapy and plasmapheresis, play critical roles in patient management within the intensive care unit (ICU). Temporary dialysis catheters inserted via the femoral vein are widely used for this purpose due to their ease of placement and rapid application. However, femoral vein catheterization is associated with both thrombotic and infectious complications [1].

Catheter-related thrombosis (CRT) is a serious complication associated with increased morbidity and mortality, particularly in patients with renal failure. Thrombosis can lead to the loss of vascular access and may result in potentially life-threatening embolic events, including pulmonary embolism. CRT can be classified as intrinsic, when the thrombus forms within or immediately around the catheter, or extrinsic, when it develops in the adjacent vessel wall due to endothelial injury or altered blood flow. In some cases, catheter-induced thrombi may propagate, causing complete occlusion of the central vein and resulting in deep vein thrombosis (DVT) [2].

Doppler ultrasonography (DUSG) is a noninvasive, inexpensive, accessible, and rapid diagnostic method with high accuracy for detecting CRT in anatomically accessible regions. The presence of symptoms consistent with thrombosis in patients with catheters aids diagnosis; however, the diagnostic performance of DUSG decreases in deeper central veins [3].

The reported thrombosis rate for short-term central venous catheters placed via the femoral vein is zero [4]. However, the rate for temporary femoral dialysis catheters – which have larger diameters – remains unclear. This study aimed to determine the incidence of catheter-related DVT in patients with temporary femoral vein dialysis catheters used for extracorporeal treatments and to evaluate the effect of catheter diameter on thrombosis development.

Material and Methods

STATISTICAL ANALYSIS:

No formal sample size calculation was performed for this study; the cohort was established according to case availability. The Shapiro-Wilk test was used to assess whether continuous variables followed a normal distribution. Continuous variables were expressed as mean±standard deviation or median (range), as appropriate. Categorical variables were presented as number (percentage). Depending on the distribution, the independent-samples t-test or the Mann-Whitney U test was utilized to compare continuous variables between groups. Fisher’s exact chi-square test or the Fisher-Freeman-Halton test was used to compare categorical variables. Statistical analyses were performed using IBM SPSS Statistics for Windows, Version 21.0 (IBM Corp., Armonk, NY, USA). P-values <0.05 were considered statistically significant.

Results

During the study period, 262 patients were admitted to the ICU. Temporary dialysis catheters were inserted via the femoral vein in 37 patients (n=31, continuous renal replacement therapy; n=6, plasmapheresis). Four patients in the thrombosis group and 8 patients in the non-thrombosis group died during their ICU stay.

Reasons for ICU admission and comorbidities were comparable between groups. The mean APACHE II score of the study cohort was 25.4±7.5. Due to the small number of patients with malignancy, subgroup statistical analysis was not feasible. The body mass index of patients with DVT was below 30 kg/m2, and there was no statistically significant difference between the 2 groups. Similarly, no significant differences were observed between groups with respect to smoking history, prior DVT, mortality, or illness severity scores (P>0.05) (Table 1).

Among the patients, CRT was identified in 13.5% within the first 7 to 10 days and in 18.9% during the entire ICU stay. The mean catheter dwell time was 8.5 days (range, 6–17). DUSG detected DVT in 5 patients within the first 7 to 10 days and in 2 of 17 patients who were evaluated immediately before catheter removal at discharge; all cases of DVT were present on the catheterized side. Although the DUSG protocol was generally followed, early catheter removal or patient discharge occasionally led to deviations from the planned imaging schedule. In 5 asymptomatic patients with DVT, the LMWH dose was increased. Catheters remained functional and were used without complications during extracorporeal treatment. All patients with DVT were asymptomatic; they showed no evidence of leg swelling, pain, perfusion disturbance, discoloration, or temperature change, and no catheter dysfunction was detected.

No significant differences were observed in vessel diameter measurements between patients who developed thrombosis and those who did not during the first 10 days, in either the anteroposterior or transverse dimensions (P>0.05) (Table 2, Figure 1).

Discussion

According to the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines, the femoral vein is considered the second-line option for dialysis catheter placement in patients with acute kidney injury [5]. In the AKIKI and RENAL studies, femoral access was selected in 53% and 67% of cases, respectively, particularly among patients with more severe illness [6,7]. This approach allows faster and easier insertion than jugular or subclavian access; it leads to fewer complications and requires less procedural expertise [7,8]. These characteristics make femoral access suitable for urgent extracorporeal therapies such as dialysis and plasmapheresis [7]. In nonemergency situations, however, alternative access sites are preferred for improved patient comfort and mobility. Although our study excluded patients with jugular or subclavian catheters, the high mean APACHE II score (25.41±7.49) among those with femoral catheters reflected the severity of their condition.

Thrombosis remains an important complication of catheter use. Symptomatic CRT occurs in approximately 0.5% of patients with jugular or femoral dialysis catheters [7]. In our study, all cases were asymptomatic, and no clinical signs of thrombosis were observed. Although some patients were sedated or intubated, the 2 conscious patients reported no symptoms. DUSG is a preferred noninvasive diagnostic method with high sensitivity in accessible venous segments. Köksoy et al. reported a sensitivity of 94% and specificity of 96% for DUSG in diagnosing CRT; absence of respiratory variation showed the highest sensitivity, and lack of blood flow demonstrated the highest specificity [9]. However, DUSG is less effective for evaluating proximal veins, such as the iliac or brachiocephalic segments. In our cohort, the incidence of catheter-related DVT was 13.5% within the first 10 days, suggesting that screening is beneficial even in the absence of clinical symptoms.

According to Virchow’s triad, thrombus formation results from blood stasis, endothelial injury, and hypercoagulability [10]. Catheter-induced endothelial damage, caused by mechanical contact and turbulent flow beyond the catheter tip, may contribute to thrombosis. Polyurethane, the material used in temporary catheters, is more thrombogenic than silicone and may promote fibrin sheath formation. In our unit, all patients received identical 11.5-Fr polyurethane catheters, ensuring uniformity in material and size. Although catheters measuring 12 to 16 Fr are generally recommended for extracorporeal systems to optimize blood flow, the 11.5-Fr catheters used in our cohort provided sufficient flow. The results of previous studies have suggested that smaller vessel diameter increases thrombosis risk with peripherally inserted catheters; however, in our cohort, femoral vein diameter did not significantly differ between patients with and without thrombosis [11,12]. These catheters, approximately 3.8 mm in diameter, provided adequate flow in adult patients but may increase the likelihood of catheter dysfunction due to intrinsic thrombosis. Although the catheters were not examined for intraluminal thrombus after removal, no catheter dysfunction was observed in patients with thrombosis.

Although no DVT was detected in 2 patients during the first 10 days, asymptomatic femoral vein thrombosis was identified by DUSG at discharge, suggesting that DVT risk persists even after catheter removal, likely due to endothelial injury. In our cohort, the overall incidence of DVT associated with temporary femoral dialysis catheters was 18.9% despite standard LMWH prophylaxis;2 patients also received antiplatelet agents (clopidogrel or aspirin). This incidence aligns with previously reported rates of 6.6% to 25% for femoral access and exceeds the rates reported for subclavian catheters (3–10%). Consistent with the findings of Herrington et al., our results indicate that anticoagulation alone may not completely prevent thrombosis in dialysis catheters [13]. The relatively high incidence observed may be attributable to the short catheter dwell time (mean, 8.5 days), the severity of illness among our patients, and the exclusive use of catheters for extracorporeal therapies, which may have minimized mechanical and infusion-related complications. Collectively, these results underscore the potential benefit of routine DUSG screening in critically ill patients.

In patients with end-stage renal disease, D-dimer has low specificity for diagnosing DVT or CRT [14]. Because most patients in this cohort had renal failure (31 of 37 receiving continuous renal replacement therapy) and D-dimer testing was not performed concurrently with DUSG, its diagnostic value in this context was limited.

Venous thromboembolism occurs in 9% to 33% of critically ill patients, and catheters represent a recognized risk factor [10]. Although none of our patients exhibited clinical signs of venous thromboembolism, 4 of 7 patients with catheter-related DVT died; these deaths were not directly related to thromboembolic events. Overall mortality exceeded 50% in both groups, and no significant difference was observed. Given its cost-effectiveness and noninvasive nature, bedside DUSG may serve as a valuable screening tool for ICU patients with femoral catheters, even in the absence of symptoms [15].

This study had some limitations. The absence of a comparator group with nonfemoral catheter sites limits generalizability. Moreover, intraluminal catheter thrombosis was not evaluated in patients with early DVT, but the absence of catheter dysfunction suggests limited clinical relevance. DUSG was performed only within the first 10 days, during which 2 asymptomatic thrombotic events were identified; imaging beyond this period may yield additional insights. Furthermore, the small sample size (n=37), influenced by COVID-19-related exclusions and ICU constraints, reduced the ability to detect uncommon complications. Although essential variables such as age, body mass index, APACHE II score, and catheter dwell time were recorded, additional laboratory markers – including D-dimer and extended coagulation profiles – were not obtained due to pandemic-related limitations, representing another limitation of this study. Notably, ultrasound guidance was not consistently utilized during catheter insertion, which may have increased the risk of endothelial injury. Additionally, DUSG has limited ability to detect iliac vein thrombosis, potentially leading to underestimation of proximal thrombotic events. Advanced imaging modalities may be useful for high-risk patients in future investigations.

Conclusions

Asymptomatic CRT was detected in nearly 20% of ICU patients with femoral dialysis catheters, a rate that warrants clinical attention. Although no significant differences in risk factors were identified between groups, routine DUSG screening in patients with femoral catheterization – particularly those with additional risk factors – appears justified. Early detection of thrombosis through such screening may enable timely intervention, reducing the risk of catheter dysfunction and thromboembolic complications.