The invention provides surgical needles with a porous distal portion from which
a liquid injectate will weep or ooze multidirectionally under injection pressure
while the porous distal portion of the needle is inserted into a body surface.
The porous distal portion of the needle can be fabricated from a porous carbon,
metal, ceramic or polymer and preferably has a decreasing gradient of impedance
to fluid flowing to the point of the needle to compensate for the falling off of
injection pressure as fluid moves towards the point, thereby ensuring uniform weeping
of the injectate along the injection course. The needle is adapted for attachment
to a catheter or syringe. In another embodiment, a surgical assemblage is provided
wherein a porous distal portion having similar fluid flow characteristics is located
along the distal end of a catheter, and a needle point is attached to the distal
end of the catheter (e.g., a steerable catheter) for piercing tissue. A guidance
catheter can be used to direct the invention devices to a remote internal injection
site. The invention devices and methods can be used to inject fluids (including
those containing nucleic acids for gene therapy) into interior body walls or tissue,
such as a beating heart, without substantial loss of fluid and without substantial
damage to tissue caused by injectate.