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