Single and multiple sample needle assembly with vein entry indicator

A needle assembly for collecting one or more liquid samples from a source for subsequent discharge into evacuated containers, comprising

• (a) a housing having a forward end and a rearward end;
• (b) a sample collection chamber in said housing;
• (c) a first access opening in said forward end in liquid flow communication with said chamber;
• (d) a first cannula extending outwardly from said first access opening for insertion into said source;
• (e) a second access opening in said rearward end in flow communication with said chamber;
• the improvement characterized by
• (f) a second cannula positioned in said second access opening and extending into said chamber to a point spaced from said first access opening;
• (g) said second cannula having a first and a second spaced apart opening therein in the part thereof extending into said chamber, said spaced apart openings providing flow communication between said chamber and the lumen of said second cannula;
• and
• (h) a gas permeable, liquid impermeable annular porous plug positioned for reciprocation in said chamber along said second cannula from a first position in which said first opening is covered by said porous plug and said second opening is uncovered, to a second position in which said first opening is uncovered;
• (i) whereby when said first cannula engages said source, liquid enters said chamber by forcing any gas therein through said porous plug, and out said second cannula through said first and second openings, and when said second cannula comes into contact with an evacuated container, said porous plug moves toward said second access opening under the influence of a pressure differential on either side thereof, uncovering said first opening and forcing residual air out said second opening on the side of said plug facing said rearward end, to that liquid in said chamber passes through said second cannula to said evacuated container.