Locating veins for venipuncture - using mesomorphic liquid crystals applied to skin overlying the vein

摘要

In a new procedure for venipuncture on the human body, a layer is applied to the skin the area over a vein, the layer being in heat-exchange with the skin. It contains an enantiotropic cholesterol deriv. with a liq. crystal phase which undergoes a colour change in the mesomorphic phase at a temp. taken up by the skin as a result of the venous blood flow. After application of the layer, the skin in the area in question is warmed by the venous blood flow, and the colour change in the mesomorphic phase takes place. An instrument for venipuncture is then applied to the skin at a position indicated by the colour change to be the site of a vein. A new liq. crystal prepn. for use in the procedure contains an enantiotropic cholesterol deriv. as the substance with a liq. crystal phase. At least two oil-soluble dyes are dissolved in the substance in a total concn. of 0.01-1% (based on the total prepn. wt., the dyes reflecting light of different wavelengths in the range 400-700 nm but practically absorb light of all wavelengths. A simple method used e.g. when obtaining blood samples or giving intravenous injections or infusions. The prepsn. can be used for other purposes where it is necessary to locate veins or peripheral vessels.