A young motorist suffered injuries in a major road traffic accident. He was diagnosed to have a fracture of the left femur and left humerus. He was also having fractures of multiple ribs anteriorly on both the sides. In the examination, the blood pressure was 80/ 60 mm Hg. and heart rate was 140/minute. The patient was agitated, restless, and tachypneic. Jugular veins were distended. Air entry was adequate in both the lung fields. Heart sounds were barely audible. Femoral pulses were weakly palpable but distally no pulsation could be felt. On a priority basis, the immediate intervention would be -