This will be a Prospective, randomized, open- label, parallel-group, center trial, which will include 80 of Children which will be admitted at Pediatric Intensive Care Unit (PICU) of Menoufia university Hospital from August 2026 to Mars 2027.

Aim of the study will be:

1. Compare the incidence of clinically significant catheter-related complications (catheter occlusion requiring intervention or catheter-related thrombosis) within 14 days after CVL insertion between children receiving prophylactic anticoagulation and those receiving standard care.
2. Compare time-to- first catheter occlusion.
3. Compare rate of catheter-related bloodstream infection (CLABSI) within 30 days.
4. Compare number of catheter manipulations and unplanned catheter removals.
5. Compare major and minor bleeding events.
6. Assess catheter dwell time and need for thrombolysis or therapeutic anticoagulation.

The study population will be divided into two groups:

1. Enoxaparin Group (Anticoagulation Arm):

   This group will receive prophylactic anticoagulation with enoxaparin in accordance with institutional guidelines for prophylactic anticoagulation in Pediatric patients.

2. Usual Care Group (Control Arm):

This group will receive standard care without prophylactic anticoagulation.

All patients in this study will be subjected to:

A- Demographic and clinical data Collection:

• Patient demographics: age, sex, body mass index (BMI) and the primary diagnosis.
• CVC characteristics: type of line, number of lumens, catheter size, site and laterality, and date of insertion and removal.
• Thrombotic events: date of thrombus detection, affected blood vessel (confirmed by Doppler ultrasound), and anticoagulation details (type, dose, and duration. (
• Anticoagulant use: agent used (e.g., LMWH), initiation timing and monitoring. B- Full clinical examination will be done including vital signs (HR, RR, BP, temperature) for each child.

C- Investigations will be done including the following:

Laboratory Analysis: CBC, Platelet counts at baseline, day 3-5, for monitoring heparin- related thrombocytopenia, CRP, Electrolytes, Blood culture, Urea, creatinine, ALT, AST and D-dimer level.

Radiological: Ultrasound of catheterized vessel if clinical suspicion of thrombosis; consider scheduled ultrasound on day 7 and 14.

Intervention and Monitoring

Enoxaparin Group (Intervention Arm):

• Children randomized to receive enoxaparin will be administered enoxaparin subcutaneously every 12 hours, with dosing based on age and weight as follows:

  1. 0.75mg/kg for children ≤2 months old.
  2. 0.5 mg/kg (maximum 30 mg) for children >2 months old.

• Doses will be adjusted for obesity and renal insufficiency as needed.

• The first dose will be given within 24 hours of CVC insertion. The dose will be adjusted to achieve a target anti-Xa level of 0.2-0.5 IU/mL.

• Anti-Xa levels will be measured locally 4-6 hours after every third dose, and dosing will be adjusted accordingly until the target range is reached. Once therapeutic range is achieved, anti-Xa monitoring will be performed weekly.

• Enoxaparin will be discontinued in the event of a clinically significant bleeding episode. It will be resumed 24 hours after correction of any coagulopathy, as confirmed by clinical and laboratory parameters.

Usual Care Group (Control Arm):

Children randomized to usual care will not receive anticoagulation. Standard CVC care procedures will be followed according to PICU protocols.

Monitoring for Thrombosis and Bleeding

1. All children will undergo daily clinical monitoring for signs of bleeding.

2. To evaluate catheter-related thrombosis, ultrasound imaging of the vein proximal and distal to the CVC insertion site.

3. To assess coagulation profile and thrombotic risk, blood samples will be drawn at the following time points:

   1. On the day of CVC insertion
   2. The day after insertion
   3. Day 4 after insertion

Inclusion Criteria:

1)- All Children requiring a newly placed central venous line (peripherally inserted central catheter [PICC], or non-tunneled central venous catheter) for clinical care.

Exclusion Criteria:

1. - Known major congenital bleeding diathesis or platelet count <50,000/µL at time of insertion.
2. - Already on therapeutic anticoagulation for another indication.
3. - Known heparin allergy or history of heparin-induced thrombocytopenia.
4. - Use of dialysis catheters (study focuses on standard CVCs/PICCs).