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The influence of thoracic epidural anesthesia on liver hemodynamics in patients under general anesthesia.

BACKGROUND AND OBJECTIVE
Hepatic hypoperfusion is regarded as an important factor in the pathophysiology of perioperative liver injury. Although thoracic epidural anesthesia is a widely used technique, limited data are available about the effects on hepatic blood flow with blockade restricted to thoracic segments in humans. The main objective of the present study was to investigate the effects of thoracic epidural anesthesia on hepatic blood flow under general anesthesia in humans.


MATERIAL AND METHODS
In 40 patients under general anesthesia, we assessed hepatic blood flow using plasma disappearance rate of indocyanine green (PDRICG) as a simple noninvasive method before and after induction of thoracic epidural anesthesia. The epidural catheter was inserted at the Th7/8 or Th8/9, and 1% lidocaine at a mean (range) dose of 8 (6-10) mL was injected. Ephedrine bolus was given to patients who demonstrated a decrease in mean arterial blood pressure below 60 mm Hg after induction of thoracic epidural anesthesia (TEA-E group). Other patients did not receive any catecholamines during the study period (TEA group). Ten patients who did not undergo TEA served as controls (control group).


RESULTS
In 7 patients, administration of ephedrine was necessary to avoid a decrease in mean arterial blood pressure below 60 mm Hg. Thus, the TEA-E group consisted of 7 patients and TEA group of 33. In the TEA group, thoracic epidural anesthesia was associated with a mean 2.3% min(-1) decrease in PDRICG (P<0.05). In the TEA-E group, all seven patients showed a 2.2% min(-1) decrease in PDRICG (P<0.05). Patients in the control group showed a mean 1.1% min(-1) increase in PDRICG (P<0.05). In contrast to hepatic blood flow, cardiac output was not affected by thoracic epidural anesthesia.


CONCLUSIONS
In humans, thoracic epidural anesthesia is associated with a decrease in hepatic blood flow. Thoracic epidural anesthesia combined with ephedrine bolus was found to result in further decrease in hepatic blood flow.