Thoracic sympathetic block reduces respiratory system compliance.
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.
Benseñor
Fábio Ely Martins
FE
Anesthesia Department, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil. bensenor@ajato.com.br
Vieira
Joaquim Edson
JE
Auler Júnior
José Otávio Costa
JO
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
D002045:Bupivacaine