Obtaining blood samples for anti-factor Xa quantification through umbilical artery catheters

Area of Science:

• Neonatal Medicine
• Pharmacology
• Clinical Chemistry

Background:

• Neonates treated with low-molecular-weight heparin require regular monitoring of anti-factor Xa (anti-FXa) levels.
• Conventional monitoring involves repeated venipunctures, which can be invasive for neonates.
• Blood samples from umbilical artery catheters (UACs) are typically unsuitable due to heparin contamination from infusates.

Purpose of the Study:

• To evaluate a modified method for collecting blood samples for anti-FXa monitoring from UACs in neonates receiving heparin.
• To reduce the need for repeated venipunctures by utilizing UACs for blood sampling.

Main Methods:

• A novel blood drawing port, free of heparinized fluids, was integrated into the UAC system.
• Neonates with UACs were randomized to collect samples after clearing 0.5 ml, 3.0 ml, or 4.0 ml of fluid.
• The presence of heparin contamination in the collected samples was assessed.

Main Results:

• Twelve neonates with UACs completed the study without adverse events.
• Heparin contamination (anti-FXa levels ≥ 0.1 U/ml) occurred in 66% of samples with 0.5 ml clearance, 16% with 3.0 ml clearance, and 8% with 4.0 ml clearance.
• Significant reductions in contamination were observed with 3.0 ml and 4.0 ml clearance compared to 0.5 ml (p = 0.0026 and p = 0.0006, respectively).

Conclusions:

• Blood samples for anti-FXa monitoring can be reliably obtained from UACs, even with concurrent heparinized infusions.
• A dedicated, non-heparinized sampling port and a line-clearing volume of at least 4.0 ml are crucial for minimizing contamination.
• This modified UAC sampling technique, with an acceptable 8% contamination rate, offers a viable alternative to repeated venipunctures in neonates.