title: Thoracic sympathetic block reduces respiratory system compliance.
abstract: OBJECTIVE
  Thoracic epidural anesthesia (TEA) following thoracic surgery presents known analgesic and respiratory benefits. However, intraoperative thoracic sympathetic block may trigger airway hyperreactivity. This study weighed up these beneficial and undesirable effects on intraoperative respiratory mechanics.
  
  
  METHODS
  Randomized, double-blind clinical study at a tertiary public hospital.
  
  
  METHODS
  Nineteen patients scheduled for partial lung resection were distributed using a random number table into groups receiving active TEA (15 ml 0.5% bupivacaine, n = 9) or placebo (15 ml 0.9% saline, n = 10) solutions that also contained 1:200,000 epinephrine and 2 mg morphine. Under general anesthesia, flows and airway and esophageal pressures were recorded. Pressure-volume curves, lower inflection points (LIP), resistance and compliance at 10 ml/kg tidal volume were established for respiratory system, chest wall and lungs. Students t test was performed, including confidence intervals (CI).
  
  
  RESULTS
  Bupivacaine rose 5 +/- 1 dermatomes upwards and 6 +/- 1 downwards. LIP was higher in the bupivacaine group (6.2 +/- 2.3 versus 3.6 +/- 0.6 cmH2O, p = 0.016, CI = -3.4 to -1.8). Respiratory system and lung compliance were higher in the placebo group (respectively 73.3 +/- 10.6 versus 51.9 +/- 15.5, p = 0.003, CI = 19.1 to 23.7; 127.2 +/- 31.7 versus 70.2 +/- 23.1 ml/cmH2O, p < 0.001, CI = 61 to 53). Resistance and chest wall compliance showed no difference.
  
  
  CONCLUSIONS
  TEA decreased respiratory system compliance by reducing its lung component. Resistance was unaffected. Under TEA, positive end-expiratory pressure and recruitment maneuvers are advisable.
authors.affiliation: Anesthesia Department, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil. bensenor@ajato.com.br
authors.forename: Fábio Ely Martins
authors.initials: FE
authors.lastname: Benseñor
authors.forename: Joaquim Edson
authors.initials: JE
authors.lastname: Vieira
authors.forename: José Otávio Costa
authors.initials: JO
authors.lastname: Auler Júnior
mesh_terms: D000328:Adult; D000399:Air Pressure; D000403:Airway Resistance / Q000187:drug effects / Q000502:physiology; D000767:Anesthesia, Epidural; D001340:Autonomic Nerve Block / Q000009:adverse effects*; D002045:Bupivacaine / Q000008:administration & dosage / Q000009:adverse effects*; D004311:Double-Blind Method; D004947:Esophagus / Q000187:drug effects / Q000502:physiology; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000187:drug effects / Q000502:physiology / Q000601:surgery; D008170:Lung Compliance / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D011175:Positive-Pressure Respiration; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D013990:Tidal Volume / Q000187:drug effects / Q000502:physiology
chemical_list: D002045:Bupivacaine