NEEDLE MODIFICATIONS FOR INVASIVE FETAL PROCEDURES

Objective: To investigate the effect of needle size and siliconization on fetal blood sampling, transfusion, and electrocardiography. Method s: Standard needles were modified by increasing the internal (but not the external) diameter and either siliconization of the bore or extern al Tenon coating. The siliconized needles were subjected to a series o f flow experiments with either blood or saline at various driving pres sures, and assessed in clinical use during fetal transfusion and fetal blood sampling. The Teflon-coated needles were used for fetal transfu sion to try and facilitate the fetal electrocardiogram (EGG). Results: Under conditions simulating fetal transfusion, the siliconized needle allowed a 93% increase in flow rate compared to the standard needle ( P < .05). Samples obtained after fetal transfusion with the siliconize d needles were free of clots, whereas 50% of the post-transfusion samp les with the standard needle had clots present. Similarly, samples tak en for fetal platelet count were free of platelet clumping and clots w ith siliconized needles, but not with standard needles. Fetal ECG reco rdings were recorded successfully when Teflon-coated needles were used to access the fetal circulation via the intrahepatic vein. Conclusion s: Modifications to standard needles improved blood now and reduced th e activation of coagulation during bath fetal intravascular transfusio n and platelet count measurement. Direct fetal ECG recording was facil itated by Tenon coating the external surface of the needle, insulating the fetal signal from maternal electrical signals.