title: Needle modifications for invasive fetal procedures.
abstract: OBJECTIVE
  To investigate the effect of needle size and siliconization on fetal blood sampling, transfusion, and electrocardiography.
  
  
  METHODS
  Standard needles were modified by increasing the internal (but not the external) diameter and either siliconization of the bore or external Teflon coating. The siliconized needles were subjected to a series of flow experiments with either blood or saline at various driving pressures, and assessed in clinical use during fetal transfusion and fetal blood sampling. The Teflon-coated needles were used for fetal transfusion to try and facilitate the fetal electrocardiogram (ECG).
  
  
  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 siliconized needles were free of clots, whereas 50% of the post-transfusion samples with the standard needle had clots present. Similarly, samples taken for fetal platelet count were free of platelet clumping and clots with siliconized needles, but not with standard needles. Fetal ECG recordings were recorded successfully when Teflon-coated needles were used to access the fetal circulation via the intrahepatic vein.
  
  
  CONCLUSIONS
  Modifications to standard needles improved blood flow and reduced the activation of coagulation during both fetal intravascular transfusion and platelet count measurement. Direct fetal ECG recording was facilitated by Teflon coating the external surface of the needle, insulating the fetal signal from maternal electrical signals.
authors.affiliation: Institute of Obstetrics and Gynaecology, Royal Postgraduate Medical School, University of London, Queen Charlotte's & Chelsea Hospital, United Kingdom.
authors.forename: C R
authors.initials: CR
authors.lastname: Welch
authors.forename: D G
authors.initials: DG
authors.lastname: Talbert
authors.forename: R M
authors.initials: RM
authors.lastname: Warwick
authors.forename: E A
authors.initials: EA
authors.lastname: Letsky
authors.forename: C H
authors.initials: CH
authors.lastname: Rodeck
mesh_terms: D001805:Blood Transfusion, Intrauterine / Q000295:instrumentation*; D004562:Electrocardiography / Q000295:instrumentation*; D004867:Equipment Design; D005312:Fetal Blood / Q000502:physiology; D005318:Fetal Heart / Q000502:physiology; D006801:Humans; D009339:Needles; D011138:Polytetrafluoroethylene; D012828:Silicones
chemical_list: D012828:Silicones; D011138:Polytetrafluoroethylene