OBTAINING samples of venous blood from small infants presents a problem even to the experienced pediatrician. A method providing least trauma for baby and doctor is always desired. A simple technique for obtaining samples of venous blood from premature and small infants was described by Banus in 1957. A modification of his technique has been adopted in the present technique which employs simpler equipment and easily allows obtaining volumes of blood from 5 to 10 ml. EQUIPMENT (Figs. Ia and Ib) Polyethylene catheter with attached No. 23-gauge needle (modified Murphy-Gardner set). Plastic needle-adapter. No. 20-22 gauge needle. Hemostat. Vacuum test tube. PROCEDURE The polyethylene catheter is connected to [See Fig. 1a,1b in Source Pdf] the plastic needle-adapter and the latter to a No. 20-22 gauge needle (Fig. lb). The catheter is clamped with the hemostat, which will maintain a good vacuum, and the needle inserted through the center of the rubber plug of the vacuum-containing test tube. A scalp vein is entered against the blood flow. As this is done the blood will flow several millimeters into the catheter. The hemostat is then released, permitting blood to flow through the polyethylene catheter into the test tube by means of the vacuum existing in the system. The polyethylene catheter and needle may be rinsed with heparin before assembling, in order to prevent clotting when large volumes of blood are required. Scalp veins are preferred to other peripheral veins, because the needle can be held firmly while in such a superficial vein, assuring a good flow of blood. COMMENT This technique has several distinct advantages over the more commonly used methods of venipuncture. Minimal equipment, which for the most part is inexpensive and disposable, is needed. There is less trauma to the infant than by standard procedures for blood-letting. With very little experience the technique can be performed with facility. Because suction is evenly controlled, the plasma obtained is usually free of hemolysis. There is almost no exposure to air with this system, so that blood for determination of carbon dioxide can be collected with accuracy, providing oil is added to the tube immediately after collecting the blood. The polyethylene catheter can be clamped during the procedure, and the collecting tubes can be changed, should both clotted and non-coagulated specimens be desired.
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