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Continuous positive pressure ventilation during epidural blockade--effects on cardiac output distribution
P Elowsson1, K Norlén, S Jakobson
1Department of Anaesthesiology and Intensive Care, Uppsala University Hospital, Sweden.
Acta Anaesthesiologica Scandinavica
|January 11, 2001
Summary
Epidural blockade alters regional blood flow during mechanical ventilation. While vital organ perfusion remains stable, skeletal muscle blood flow decreases, and adrenal perfusion is abolished, impacting the body's response to ventilation changes.
Area of Science:
- Physiology
- Anesthesiology
- Cardiovascular Research
Background:
- Continuous positive pressure ventilation (CPPV) can decrease cardiac output (CO).
- The body typically redistributes blood flow to vital organs when CO falls during CPPV.
- The effect of epidural blockade on this compensatory mechanism is not well understood.
Purpose of the Study:
- To investigate whether epidural blockade modifies the regional blood flow adaptation during CPPV.
- To assess the impact of thoracic (Thep) and lumbar (Lep) epidural blockade on hemodynamics and organ perfusion.
Main Methods:
- Regional blood flows were measured using the microsphere technique in anesthetized pigs.
- Animals underwent spontaneous breathing and CPPV (8 cm H2O) before and after epidural blockade (lidocaine) at thoracic or lumbar levels.
- Hemodynamic parameters and organ-specific blood flow were analyzed.
Main Results:
- Epidural blockade, especially thoracic, significantly decreased mean arterial pressure and CO during CPPV.
- Relative perfusion to the central nervous system, heart, and kidneys remained stable.
- Adrenal perfusion was abolished, and skeletal muscle perfusion decreased with epidural blockade.
Conclusions:
- Locally mediated vasoregulation in vital organs overrides sympathetic blockade effects from epidural anesthesia.
- Thoracic epidural blockade impairs the ability to respond to hemodynamic changes induced by CPPV, likely due to cardiac sympathetic nervous system blockade.
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