BJA Advance Access originally published online on July 26, 2004
British Journal of Anaesthesia 2004 93(4):552-559; doi:10.1093/bja/aeh235
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© The Board of Management and Trustees of the British Journal of Anaesthesia 2004
Effects of thoracic epidural anaesthesia on microvascular gastric mucosal oxygenation in physiological and compromised circulatory conditions in dogs
1 Department of Anaesthesiology, University Hospital of Düsseldorf, Germany. 2 Department of Experimental Anaesthesia, Campus Virchow-Klinikum, Charité, Berlin, Germany
* Corresponding author. E-mail: schwartelothar{at}aol.com
Background. The effects of thoracic epidural anaesthesia (TEA) on gastric mucosal microvascular haemoglobin oxygenation (µHbO2) are unclear. At the splanchnic level, reduction of sympathetic tone may promote vasodilation and increase µHbO2. However, these splanchnic effects are counteracted by systemic effects of TEA (e.g., decreased cardiac output (CO) and mean arterial pressure (MAP)), thus making the net effect on µHbO2 difficult to predict. In this respect, effects of TEA on µHbO2 may differ between physiological and compromised circulatory conditions, and additionally may depend on adequate fluid resuscitation. Furthermore, TEA may alter the relationship between regional µHbO2 and systemic oxygen-transport (DO2).
Methods. Chronically instrumented dogs (flow probes for CO measurement) were anaesthetized, their lungs ventilated and randomly received TEA with lidocaine (n=6) or epidural saline (controls, n=6). Animals were studied under physiological and compromised circulatory conditions (PEEP 10 cm H2O), both with and without fluid resuscitation. We measured gastric mucosal µHbO2 by reflectance spectrophotometry, systemic DO2, and systemic haemodynamics (CO, MAP).
Results. Under physiological conditions, TEA preserved µHbO2 (47 (3)% and 49 (5)%, mean (SEM)) despite significantly decreasing DO2 (11.3 (0.8) to 10.0 (0.7) ml kg–1 min–1) and MAP (66 (2) to 59 (3) mm Hg). However, during compromised circulatory conditions, TEA aggravated the reduction in µHbO2 (to 32 (1)%), DO2 (to 6.7 (0.8) ml kg–1 min–1) and MAP (to 52 (4) mm Hg), compared with controls. During TEA, fluid resuscitation completely restored these variables. TEA preserved the correlation between µHbO2 and DO2, compared with controls.
Conclusions. TEA maintains µHbO2 under physiological conditions, but aggravates the reduction of µHbO2 induced by cardiocirculatory depression, thereby preserving the relationship between gastric mucosal and systemic oxygenation.
Presented in part at the German Anaesthesia Congress 2003 (April 9–12, Munich, Germany) and the European Society of Intensive Care Congress 2003 (October 5–8, Amsterdam, The Netherlands).