The effects of thoracic epidural anesthesia on hepatic perfusion and oxygenation in healthy pigs during general anesthesia and surgical stress.

Perioperative liver injury due to decreased perfusion may be an underlying mechanism behind the development of systemic inflammatory response syndrome. We designed this animal study to assess whether thoracic epidural anesthesia (TEA) impairs liver oxygenation due to induced hypotension. After ethical approval, 19 anesthetized and acutely instrumented pigs were randomly assigned to 3 groups (control and TEA alone versus TEA plus volume loading). Bupivacaine 0.5% 0.75 mL per segment was injected into the epidural space, aiming for a T5 to T12 block. After baseline values were obtained, measurements were repeated 60 and 120 min after epidural injection. TEA was associated with decreased mean arterial blood pressure but no change in total hepatic blood flow. Oxygen delivery to the liver and oxygen uptake remained unchanged. Liver tissue oxygen partial pressure did not decrease. The plasma indocyanine green disappearance rate remained stable. Volume loading before TEA did not relevantly affect total hepatic blood flow; it even decreased oxygen supply to the liver by hemodilution. We conclude that, despite decreased mean arterial blood pressure, TEA did not affect liver oxygenation. There was no clinically relevant effect of volume loading on total hepatic perfusion.