A 28-year-old woman is brought to the trauma bay following a stab wound to the left anterior chest at the 4th intercostal space. On arrival: BP 76/48 mmHg, HR 142/min, RR 28/min, JVD present, muffled heart sounds, and diminished breath sounds on the left. A bedside ultrasound shows pericardial fluid. After two large-bore IVs are placed and 1 L of warm crystalloid is running wide open, her BP is 78/50 mmHg and HR remains 142/min. What is the most appropriate immediate intervention?