The invention pertains to hardware and methods for direct injection, into the left ventricle of the heart of a patient or animal in cardiac arrest or in incipient cardiac arrest—using a 14-18 gauge cannula typically equipped with a retractable trocar—of an adequate amount of chilled saline or cryoprotective solution to create flow of chilled blood through the two carotid arteries, the two vertebral arteries, and the brain, to cool the brain or other vital organs. Generally, enough saline or cryoprotective solution is injected under high enough pressure to create a 30% baseline common carotid blood flow. The cannula arrangement with coordinated sharpened-tip retractable trocar, together with its surrounding flexible and rigid shield(s), diaphragm and stopcock(s), provides a sterile, self-sealing system suitable for use either in “the field” or in a hospital setting.