Pre-slit injection site and tapered cannula

A blood sampling system for withdrawing blood from a patient, comprising:

• (a) tubing adapted to be connected at one end to the patient in fluid communication with the patient's vascular system and at the other end to a fluid supply;
• (b) a reservoir assembly connected in-line to said tubing between the patient end and the fluid supply end, comprising a flow through reservoir housing having inner walls defining an interior chamber for holding fluid, a first port in fluid communication with said interior chamber connected to said tubing leading to the fluid supply, a second port in fluid communication with said interior chamber connected to said tubing leading to the patient, a retractable plunger disposed within said reservoir housing, said plunger formed in a complementary configuration to said interior chamber and adapted to traverse said chamber, and a sealing member disposed about said plunger in slidable sealing engagement with said inner walls of said interior chamber, said plunger adapted to be slidably retracted within said interior chamber to create negative pressure within said chamber, said negative pressure being effective to draw fluid from said tubing into said chamber for temporarily storing said fluid in said chamber and to draw blood from said patient into said tubing, said plunger adapted to be slidably projected toward said ports for reintroducing said stored fluid into said tubing;
• and
• (c) a sampling site connected in-line to said tubing between the patient end and said reservoir assembly, said sampling site comprising a flow through sampling site housing having a first port connected to said tubing leading to the reservoir assembly and a second port connected to said tubing leading to the patient, thereby defining a fluid channel through said sampling site housing, means defining an access aperture in said sampling site housing in communication with said fluid channel, and flexible means carried by said sampling site housing for sealing said access aperture, said means having a resealable opening therein such that a blunt cannula can be sealingly inserted through said opening and placed in fluid flow communication with said channel to withdraw blood from said tubing and such that said blunt cannula can be removed therefrom with said flexible means interacting with said sampling site housing so as to reseal said resealable opening;
• (d) said blunt cannula comprising an elongated member with a fluid flow channel extending generally axially therewithin and through a distal end of said member, said elongated member being generally cylindrically along a substantial portion of its length and terminating in a generally tapered distal end portion having a blunt end edge.

A method for withdrawing a blood sample from a patient line which is in communication with the patient's vascular system at one end and connected to a fluid supply at the other end, comprising the steps of:

• (a) disposing a reservoir assembly in said patient line between said fluid supply end and the patient end of said line;
• (b) disposing a sampling site in said patient line between said reservoir assembly and the patient end of said line, said sampling site comprising a flow through housing having a first port leading to the reservoir assembly and a second port leading to the patient, thereby defining a fluid channel through said housing, means defining an access aperture in said housing in communication with said fluid channel, and flexible means carried by said housing for sealing said access aperture, said means having a resealable opening therein such that a blunt cannula can be sealingly inserted through said opening and placed in fluid flow communication with said channel and can be removed therefrom with said flexible means interacting with said housing so as to reseal said resealable opening;
• (c) disabling fluid flow from the fluid supply to said reservoir assembly;
• (d) drawing fluid contained in said patient line into said reservoir assembly, said drawing being effective to draw blood from the patient into said patient line;
• (e) inserting said blunt cannula through said resealable opening of said sampling site to withdraw blood from said patient line;
• and
• (f) removing said blunt cannula from said sampling site, said flexible means of said sampling site thereby interacting with said sampling site housing so as to reseal said resealable opening.