[Phrenic nerve injury following coronary artery bypass surgery: its clinical implication and management]

The hospital records of 80 patients undergoing coronary artery bypass surgery, including 19 patients using the "isolation pad", were reviewed to examine the prevalence of the phrenic nerve injury (PNI). All patients received ice slush for topical cooling during operation. The degree of the elevated diaphragm was evaluated objectively by "Diaphragmatic Elevation Index, DEI" calculated from the plain chest roentgenogram taken before and after the operation. Sixty-one patients without using the isolation pad were subdivided into 3 groups, mild (35), moderate (15), and severe (11) according to the degree of the elevated diaphragm, and compared along with those using the isolation pad. All groups could not be distinguished by clinical course. The degree of left diaphragmatic elevation was significantly high compared with that of right, but recovered significantly at discharge except 2 patients. Pulmonary complication was highly associated with the "severe" groups. Because PNI is often transient and of little clinical significance, it is sometimes neglected. But considering the high frequency of the development of pulmonary complication, proper protective measure should be undertaken. Utilization of the isolation pad was effective means in terms of protection of phrenic nerve.