Table 1.
Animal studies evaluating macrohemodynamics and liver microhemodynamics
| Subjects | Ref. | Year | Title | Type of study | Scenario | No. subjects | Sensory blockade | Surrogate measure of splanchnic flow | Findings |
| Monkeys | Sivarajan et al[2] | 1976 | Systemic and regional blood flow during epidural anesthesia without epinephrine in the rhesus monkey | Prospective randomized | Anesthetized animals, epidural catheter placed L1-L2 | 9 (4 low epidural aneshtesia - level T10 vs 5 high epidural anesthesia - level T1) | higher level T10 or T1 | Radioactive microspheres and direct invasive monitoring of cardiac output | Low epidural - no difference in blood flow to major organs, while T1 epidural ↓ blood flow to liver, pancreas and gut (hepatic artery, portal vein) |
| Dogs | Meissner et al[4] | 1999 | Limited upper thoracic epidural block and splanchnic perfusion in dogs | Prospective observational | Induction of upper thoracic epidural in awake and anesthetized dogs and measurements of splanchinc perfusion | 13 (6 anesthetized, 7 no) | T1-T5 | Coloured microspheres injected in the aorta and then collected from tissue samples after autopsy | High TEA had no effect on sympathetic activity and splanchnic blood flow, nor in the awake nor anesthetized state. Propofol anaestehsia increased liver perfusion |
| Rabbits | Ai et al[6] | 2001 | Epidural anesthesia retards intestinal acidosis and reduces portal vein endotoxin concentrations during progressive hypoxia in rabbits | Prospective randomized | Progressive hypoxia in anesthetized animals | 18 (9 TEA/Lidocaine vs 9 TEA/NaCl 0.9%) | insertion point T12-L1 and 3-4 cm advancement | Portal blood flow, portal oxygen extraction ratio, portal pH, portal Lactate, intramucosal pH (pHi) of the ileum, portal endotoxin | pHi and pHart significantly higher and portal Endotoxin and Lactate significantly lower in TEA/Lido group. No diifferences in portal blood flow |
| Pigs | Vagts et al[5] | 2003 | The effects of thoracic epidural anesthesia on hepatic perfusion and oxygenation in healthy pigs during general anesthesia and surgical stress | Prospective randomized | Anesthetized and acutely instrumented pigs, assigned to 3 groups: control vs TEA plus basic fluid (BF) vs TEA plus VL | 19 (3 CTRL; 8 TEA alone; 8 TEA + VL) | T5 to T12 | Hepatic blood flow using ultrasonic transit-time perivascular flowprobes around the hepatic artery and portal vein; multiwire surface electrode placed onto the liver to measure tissue surface PO2; PDR-icg | Despite a decrease in MAP, TEA had no effect on total hepatic blood flow, liver DO2 and VO2. Liver tissue PO2 did not decrease. Lactate uptake and PDR-icg remained unchanged. Volume loading did not show any benefit with regard to hepatic perfusion, oxygenation, and function |
| Rats | Shäper et al[3] | 2010 | TEA attenuates endotoxin induced impairment of gastro intestinal organ perfusion | Prospective randomized | Sepsis model through infusion of LPS, evaluation of regional flow at 30', 60', 120' | 18 (9 TEA vs 9 sham) | T4-T11 (methilen blue spread) | Fluorecent microspheres withdrawal technique, then evaluation of microspheres in brain, heart, ileopsoas muscle, liver pancreas gut segments; determination plasma cathecolamines | TEA ↑ blood flow to GIT organs under LPS effect |
| Studies evaluating liver micro hemodynamics | |||||||||
| Rats | Freise et al[17] | 2009 | Hepatic effects of TEA in experimental severe acute pancreatitis | Prospective randomized blinded image analysis | Animal model of acute pancreatitis induced by taurocholate injection or sham lesion | 28 (7 sham + sham, 7 sham + TEA, 7 pancreat + sham, 7 pancreat + TEA) an additional 22 animals were assigned to the three group to asses hepatic apoptosis | catheter tip placed T6 | Intravital microscopy of liver left lobe, cell adehesion to sinusoid wall (rollers and stickers), apoptosis of cells by Fas-L pathway | TEA ↑ diameter of sinusoids in pancreatitis, TEA ↓ the number of parenchymal apoptotic cells in pancreatitis (Fas-L pathway), TEA does not have much influence in sham groups |
| Rats | Freise et al[18] | 2009 | TEA reduces sepsis related hepatic hyperperfusion and reduces leucocyte adehesion in septic rats | Prospective randomized blinded image analysis | Sepsis model induced with cecal ligation and perforation | 24 (8 sham + sham, 8 sepsis + sham, 8 sepsis + TEA); another 21 animals were assessed for liver failure and hemodynamics | catheter tip placed T6 | Intravital microscopy of liver left lobe, cell adehesion to sinusoid and venules, serum transaminase activity, TNFα activity | TEA ↓ sinusoid dilation in sepsis by probably restoring hepatic arterial buffer response. TEA ↓ temporary adhesion to sinusoid wall but did not affect permanent adhesion. TEA did not affect transaminase or TNF activity. No differences in hemodynamics |
↑: Increase; ↓: Decrease; VL: Volume loading; TEA: Thoracic epidural anesthesia; CTRL: Control; MAP: Mean arterial pressure; PDRICG: Plasma disappearance rate of Indocyanine Green; LPS: Lipopolysaccharide; GIT: Gastrointestinal tract; HR: Heart rate; PEEP: Positive end expiratory pressure; HES: Hydroxethyl starch; PCO2: Carbon dioxide partial pressure; LEA: Lumbar epidural anesthesia; ERCP: Endoscopic retrograde cholangiopancreatography.