After liftoff during a helicopter emergency medical service (HEMS) flight with a patient on board, the pilot of the HEMS helicopter brought it in to a 1 to 2 foot hover and was preparing to make a right pedal turn into the wind, when a cover from a wheeled fire extinguisher, was blown airborne by the main rotor wash and ingested into the tail rotor (fenestron) of the helicopter. The helicopter lost tail rotor authority and began to spin clockwise. The pilot lowered the collective and the helicopter rotated approximately 150 degrees, then impacted the ground and continued to rotate another 20 to 30 degrees, for a total of 170 to180 degree turn, and came to rest. Examination of the helicopter by a Federal Aviation Administration inspector revealed damage to the landing gear skid tubes, fenestron composite housing, and the forward cross tube gimbal which had pushed up into a composite non-structural area of the fuselage. It was discovered, that the wheeled fire extinguisher that the cover had blown off of, had been inspected for serviceability just four days prior to the accident.