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Effect of thoracic epidural anaesthesia on ventilation= perfusion distribution and intrathoracic blood volume before and after induction of general anaesthesia
Author(s) -
HACHENBERG T.,
HOLST D.,
EBEL C.,
PFEIFFER B.,
THOMAS H.,
WENDT M.,
HEDENSTIERNA G.
Publication year - 1997
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1997.tb04856.x
Subject(s) - medicine , anesthesia , perfusion , general anaesthesia , blood volume , ventilation (architecture) , volume (thermodynamics) , cardiology , mechanical engineering , engineering , physics , quantum mechanics
Background: Gas exchange is impaired during general anaesthesia due to development of shunt and ventilation‐perfusion mismatching. Thoracic epidural anaesthesia (TEA) may affect the mechanics of the respiratory system, intrathoracic blood volume and possibly ventilation‐perfusion (V A /Q) distribution during general anaesthesia. Methods: V A /Q relationships were analyzed in 24 patients undergoing major abdominal surgery. Intrapulmonary shunt (Qs/ Q T ), perfusion of “low” V A /Q areas, ventilation of “high V A / regions, dead space ventilation and mean distribution of ventilation and perfusion were calculated from the retention/excretion data of six inert gases. Intrathoracic blood volume (ITBV) and pulmonary blood volume (PBV) were determined with a double indicator technique. Recordings were made before and after administration of 8.5±1.5 ml bupivacaine 0.5% (n=12) or 8.3±1.8 ml placebo (n=12) into a thoracic epidural catheter and after induction of general anaesthesia. Results: Before TEA, QS/QT was normal in the bupivacaine group (222%) and the placebo group (23%). TEA covering the dermatomal segments T 12 to T 4 had no effect on V A /Q relationships, ITBV and PBV. After induction of general anaesthesia S/T increased to 84% (bupivacaine group, P < 0.05) and to 72% (placebo group, P < 0.05). ITBV and PBV decreased significantly to the same extent in the bupivacaine group and the placebo group. Conclusions: TEA has no effect on V A /Q distribution, gas exchange and intrathoracic blood volume in the awake state and does not influence development of S/T and V A /Q inequality after induction of general anaesthesia.