The effect of pericardial insulation on hypothermic phrenic nerve injury during open-heart surgery.

Phrenic nerve injury was evaluated prospectively in 133 patients undergoing open-heart surgery using iced saline slush for topical hypothermia. In the control group of 70 patients no attempt was made to shield the phrenic nerves from direct exposure to ice. Phrenic nerve damage occurred in 73% of these patients, as assessed by persistent diaphragm paralysis evident on inspiratory chest roentgenogram. In 2 patients the paralysis was bilateral. In the second group of 63 patients a pericardial insulation pad was used to prevent contact of the iced slush to the phrenic nerve. Diaphragm paralysis was observed in 17% of these patients. This difference was highly significant (p less than .001). Diaphragm paralysis in the control group was clinically significant; life-threatening respiratory complications developed in 7 patients (14%), frequently resulting in multiple reintubations, tracheostomy, and prolonged mechanical ventilation. In addition, 4 patients with phrenic nerve injury exhibited a clinical syndrome consistent with gastric ileus, which may possibly represent hypothermic injury to the thoracic vagi. The likelihood of phrenic nerve injury when iced saline slush is used for topical myocardial cooling and the possibility of developing serious respiratory disability would support the routine use of pericardial insulation when this method of hypothermia is used.