PHRENIC-NERVE DYSFUNCTION AFTER CARDIAC OPERATIONS - ELECTROPHYSIOLOGIC EVALUATION OF RISK-FACTORS

Background and study objective: Phrenic nerve injury may occur after c ardiac surgery; however, its cause has not been extensively investigat ed with electrophysiology, The purpose of this study was to determine by electrophysiologic means the importance of various possible risk fa ctors in the development of phrenic nerve dysfunction after cardiac su rgical operations. Design: A prospective study was conducted, Setting: A tertiary teaching hospital pro tided the background for the stud. P atients: Sixty-three cardiac surgery patients on whom surgical operati ons were performed by the same surgical team constituted the study gro up. Mean (+/-SD) age and ejection fraction were 63+/-5 years and 50+/- 10%, respectively. Interventions: Measurement of phrenic nerve conduct ion latency time after transcutaneous stimulation preoperatively and a t 23 h and 7 and 30 days postoperatively. Results: Thirteen patients h ad abnormal phrenic nerve function postsurgery, 12 on the left side an d one bilaterally, Logistic regression anal)sis revealed that among th e potential risk factors investigated, use of ice slush for myocardial preservation was the only independent risk factor related to phrenic nerve dysfunction (p=0.01), carrying an 8-fold higher incidence for th is complication, In contrast, age, ejection fraction of the left ventr icle, operative/bypass/aortic cross-clamp time, left internal mammary artery use, and diabetes mellitus were not found to be associated with phrenic neuropathy. The postoperative outcome of patients who receive d ice slush compared with that of those who had cold saline solution d id not differ in terms of early morbidity and mortality, Conclusion: A mong the risk factors investigated, only the use of ice slush was sign ificantly associated with postoperative phrenic nerve dysfunction. The refore, ice should be avoided in cardiac surgery, since it does not se em to provide additional myocardial protection.