Infusate bag spike

A double lumen fluid bag spike. In one arrangement the spike 10 comprises a shaft 12 defining a base end 14 and a tip end 16, the shaft having two lumens, a first lumen 22 with at least one first opening 23, and a second lumen 24 with a second opening 25, the openings being separated by a wall 13. The second lumen may comprise a first channel 44 at the base end, and a second channel 46 at the tip end, wherein the first and second channels are fluidly connected at a transition region 48. The second channel has a larger cross-sectional area than the first channel. The at least first opening 23 may be disposed on a sidewall of the shaft. In another arrangement, the spike (410, Fig 9a) comprises first and second lumens (422, 424, Fig 9a) together defining a shaft, and a sliding collar (450, Fig 9a) with first and second apertures (452, 454, Fig 9c), the first apertures sized to slidably retain the first lumen and the second aperture sized to slidably retain the second lumen. A method of priming a medical device using such a bag spike is also taught.