title: Electrophysiologic evaluation of phrenic nerve and diaphragm function after coronary bypass surgery: prospective study of diabetes and other risk factors.
abstract: OBJECTIVE
  Phrenic neuropathy after coronary artery bypass grafting has been related to various risk factors with conflicting results. The aim of this study was to assess the incidence, characteristics, and clinical consequences of phrenic neuropathy and the influence of diabetes and other risk factors.
  
  
  METHODS
  We conducted an observational, prospective study of parallel groups including 94 consecutive patients subjected to coronary artery bypass grafting, half of them with diabetes and associated polyneuropathy. Electrophysiologic study of phrenic nerve conduction as the reference method, chest radiography, diaphragm ultrasound, and functional respiratory tests were performed 24 to 48 hours before and 7 days after surgery. In those patients showing phrenic neuropathy, explorations were repeated, including needle diaphragmatic electromyography, at 1, 3, 6, 9, 12, 18, and 24 months or until recovery.
  
  
  RESULTS
  Fifteen of the 94 patients (16%) had phrenic neuropathy, 9 in the left side, 3 on the right, and 3 bilateral. Nine (60%) of the affected patients had diabetes, but diabetes did not represent a greater risk of neuropathy (relative risk 1.5, 95% confidence interval 0.6-3.9). Multivariate analysis showed no association of phrenic nerve injury with age, sex, ejection fraction, diabetes, use of internal thoracic artery, or number of grafts as risk factors. Phrenic neuropathy did not result in greater morbidity, and most patients recovered in less than 1 year.
  
  
  CONCLUSIONS
  None of the risk factors studied, including diabetes, influenced the appearance of phrenic neuropathy, thus indicating a role for nerve damage during surgery. Low morbidity and relatively rapid recovery were observed.
authors.affiliation: Department of Clinical Neurophysiology, Ribera Hospital, Alzira, Valencia, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Merino-Ramirez
authors.forename: Gustavo
authors.initials: G
authors.lastname: Juan
authors.forename: Mercedes
authors.initials: M
authors.lastname: Ramón
authors.forename: Julio
authors.initials: J
authors.lastname: Cortijo
authors.forename: Elena
authors.initials: E
authors.lastname: Rubio
authors.forename: Anastasio
authors.initials: A
authors.lastname: Montero
authors.forename: Esteban J
authors.initials: EJ
authors.lastname: Morcillo
mesh_terms: D001026:Coronary Artery Bypass / Q000009:adverse effects*; D048909:Diabetes Complications / Q000209:etiology* / Q000503:physiopathology*; D003920:Diabetes Mellitus / Q000503:physiopathology*; D003964:Diaphragm / Q000502:physiology*; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010523:Peripheral Nervous System Diseases / Q000209:etiology* / Q000503:physiopathology*; D010791:Phrenic Nerve / Q000502:physiology*; D011446:Prospective Studies; D012307:Risk Factors