ABSTRACT
Two cases of bilateral phrenic nerve paralysis were reported. The first case was a 51-year-old male who underwent mitral valve replacement for mitral valve regurgitation. Upon extubation he was noted to have the paradoxical breathing pattern associated with bilateral phrenic nerve paralysis. He was treated conservatively, keeping him in a sitting position without reintubation or tracheostomy. The patient recovered from the paradoxical breathing pattern by the tenth post-operative day. The second patient was a 66-year-old male who underwent mitral valve replacement and CABG for mitral valve regurgitation and angina pectoris. Upon extubation this patient was also noted to have a paradoxical breathing pattern. Conservative treatment was initiated. This patient suffered from sudden apneic episode followed by cardiac arrest on 17th post-operative day. Cardio-pulmonary resuscitation was successful, however, the patient was noted to have extensive ischemic brain damage after resuscitation. The patient died approximately one year later from respiratory failure. Generally speaking, the cause of phrenic nerve paralysis after cardiac surgery is cold injury from ice slush used for topical cardiac cooling. However, direct mechanical injury to the right phrenic nerve might result from the proximity of the right phrenic nerve to the left atrial suture line of a mitral valve replacement.