The invention provides an apparatus for preparing a fluid for a medical procedure by mixing of at least one medicament in the form of powder with water, the medicament is held in a vessel which defines a bottom, a side wall, and a top opening which is closed by an membrane for sealing the inside of the vessel. The apparatus includes an opener for opening the membrane of the vessel. The opener includes a holder for vertically holding the vessel to downwardly orient the opening; a cutter, provided beneath the opening of the vessel held by the holder, for partially cutting the membrane along the periphery of the opening; a mechanism for vertically moving the holder toward the cutter so that the cutting edge of the cutter pierces to partially separate the membrane from the periphery of the opening whereby the medicament in the vessel falls from the vessel; a receiving member, in the form of a mesh provided beneath the cutter, for receiving all of the medicament from the vessel; and a nozzle for directing water from the source of water in the form of a spray to the medicament received by the receiving member to dissolve the medicament into the water directed to the medicament.