Hemodynamic Characters Of Patients With Obstructive Jaundice In Sevoflurane Anesthesia And Vascular Reactivity Of Isolated Thoracic Aorta Rings In Cholestatic Rats

Hepatobiliary disease is often characterized by cholestasis, the suppression or stoppage of bile flow. The most common cause of cholestasis is extrahepatic obstruction of biliary tract (obstructive jaundice). Pathologic entities causing obstruction include calculus, stricture, or tumor in or near the common hepatic duct.Obstructive jaundice is a common clinical syndrome leading to the damage of not only the liver but also other organs, which contributes to multiorgan pathological changes and multisystem deficits especially the circulation system. Obstructive jaundice causes decreased heart rate and output, depressed cardiac contractility and vascular hyporeactivity to vasoactive agents, resulting in high perioperative risk.To definite the perioperative changes of hemodynamics of obstructive jaundice patients and give them a more stable anesthesia procedure, the first part of this study is clinical research. After receiving approval from our local ethics committee, informed consent was obtained from each patient undergoing elective surgery for hepatobiliary disease with identified obstructive symptom. A pulmonary artery balloon flow catheter (Swan-ganz catheter) was passed through an introducer sheath placed in the right internal jugular vein and blood pressure was measured using a radial artery cannula before anesthesia in the operating room. Then patients were inducted by sevoflurane with a semiclosed-circuit anesthetic machine followed by i.v. administration of fentanyl and rocuronium. After tracheal intubation, anaesthesia was maintained with sevoflurane exclusively. Circulation monitoring including arterial blood pressure (ABP), cardiac output (CO), cardiac index (CI), pulmonary arterial wedge pressure (PAWP), pulmonary arterial pressure (PAP), central venous pressure (CVP) and heart rate (HR) was applied and systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) were then calculated preoperatively and at the time of MAC value of 1.0 or 1.5. Previous studies on hemodynamics of obstructive jaundice cases usually focused on global circulation system and cardiac function rather than the vascular damage. Here, we pay close attention to the vascular function in the second part. In rat models of cholestasis caused by bile duct resection, the effect of high K+ concentration, norepinephrine (NE), phenylephrine (PE) and sodium nitroprusside (SNP) on vascular tension of isolated thoracic aorta rings was determined at 3d, 7d and 14d after surgery. Ultrastructure of Thoracic aorta vascular smooth muscle cells and endothelial cells was studied by transmission electron microscopy, and Western Blot was applied to determine the expression of Alpha1D-adrenergic receptors (α1D–AR) protein. Through these assays we try to know the hemodynamic characters of obstructive jaundice patients in sevoflurane anesthesia land the vascular mechanism involved, which will be beneficial for our clinical work.Methods:Part one: Hemodynamic Characters of Patients with Obstructive Jaundice in Sevoflurane AnesthesiaForty patients with obstructive jaundice (serum total bilirubin >100μmol/L) caused by neoplasm of the bile duct or the head of the pancreas were included in the study. Twenty nonjaundiced patients who suffered chronic cholecystitis or liver hemangioma served as controls. All patients were classified as American Society of Anesthesiologists (ASA) physical status 1 or 2, and were between the ages of 40 to 60 yr.Each patient was interviewed and evaluated preoperatively, and informed consent was obtained. monitored with electrocardiography, pulse oximetry, nasopharyngeal temperature and invasive blood pressure measurement. Basic monitoring including ECG and SpO2 was started after patients entering the operation room. A Swan-ganz catheter was passed through an introducer sheath placed in the right internal jugular vein and blood pressure was measured using a radial artery cannula under local anesthesia. Intravenous access was established and the transfusion rate was controlled at 30 drops per minute. 10 minutes later, hemodynamic parameters were determined. CO was measured with thermodilution method for 3 times and the averages of 3 measurements were then calculated.Part two: Vasoconstrictor and Vasodilator Reactivity of Isolated Thoracic Aorta Rings in Cholestatic RatsMale SD rats weighed 200-220 were used. Rats were divided into bile duct ligation (BDL) group and sham group randomly. The thoracic aorta were isolated at 3d, 7d and 14d after surgery and the vasoactivity to the increased potassium, NE, PE and SNP was tested. The ultrastrature of thoracic aorta rings and the expression ofα1D–AR protein were assessed by transmission electron microscopy and western Blot respectively.After the establishment of rat models, diet, hair and the color of skin were observed. The body weight and mortality were determined at different time point and the gross appearance of vital organs was recorded. The serum bilirubin of rats was measured by auto biochemistry machine. For the vasoconstrictor reactivity, the thoracic aorta rings were stimulated with 60mmol/L K+ solution and the max constriction is teriggered. Then we performed a dose-response curve to increasing doses of PE and NE. For the vasodilator reactivity, the thoracic aorta rings were stimulated with NE 10-6mmol/L and the constriction value is defined as 100%. Different doses of SNP were administered and the relaxation of thoracic aorta rings was ministered, then a dose-response curve was obtained. For morphological analysis, the thoracic aortas were fixed with formaldehyde followed by washing in PBS. Then the samples tissue was postfixed in 1% OsO4, dehydrated via ethanol series, infiltrated by propylene oxide and embedded in Epon812. Ultra-thin sections were cut on ultramicrotome, counter-stained with uranyl acetate and lead citrate, then examined in the electron microscope. For western blot analysis, Frozen aortic tissue was used to detect the expression ofα1D–AR. Values are presented as mean±sD. One-way ANOVA was used for analysis of variance between the groups using SPSS 11.0 for Windows. P<0.05 was considered statistically significant.Results:Part one: Hemodynamic Characters of Patients with Obstructive Jaundice in Sevoflurane Anesthesia1. General state of health showed no differences in age, height, weight and surface area (P>0.05) between the two groups. The levels of bile acid and bilirubin in jaundice group are increased when compared with non-jaundice group. The ECG monitoring and SpO2 showed no significant difference between these two groups.2. The hemodynamic data indicated that, ABPm, HR, SVR, CI and CO significantly decreased (P < 0.01) in jaundice group compared to non-jaundice group. In addition PAWP of jaundice group is also reduced when compared with non-jaundice group. Other parameters did not differ significantly in the two groups.3. Compared with baseline, ABPm, PAPm, SV, SI, CO and CI of jaundice group at the time of MAC 1.0 and 1.5 end tidal decreased dramatically (P<0.01) in the period of sevoflurane anesthesia. HR and CVP showed significant decrease at MAC 1.5 end tidal (P<0.05), and no differences at 1.0 end tidal. PAWP and SVR did not differ at the procedure. In non-jaundice group, ABPm, CO and CI decreased significantly at MAC 1.0 and 1.5 end tidal (P<0.01) compared with baseline. HR showed significant decrease at MAC 1.5 end tidal (P<0.05).4. Compared with non-jaundice group, jaundice group showed elevated reduce percentage of ABPm, PAPm, CO and CI at MAC 1.0 end tidal in the anesthesia period (P<0.01). The reduced percentage of SV and SI of jaundice group showed significant increase compared to non-jaundice group. At MAC 1.5 end tidal, jaundice group showed significant elevated reduce percentage of PAPm, ABPm and CI (P<0.01 vs. P<0.05 vs. P<0.05). However, compared with non-jaundice group, reduce percentage of SVR in jaundice group at the time of MAC 1.0 and 1.5 end tidal decreased dramatically (P<0.01).Part two: Vasoconstrictor and Vasodilator Reactivity of Isolated Thoracic Aorta Rings in Cholestatic Rats1. General state of rats. 7d BDL group and 14d BDL group each have one rat died of bile leak. The yellow urine was observed at 24h after surgery. 3-4 days later, the skin turn to yellow and poor appetite, decreased weight and activity were observed. 1-2 weeks later, the ligated bile duct distended ascidially and the diameter reached 0.8-1.2cm. Leonine fluid could be drawn out from the bile duct with odour. As the obstruction syndrome lasted, the ascitic fluid increased and the liver displayed diffused intumescence in yellow brown. The isolated thoracic aorta appeared to be light yellow stained, and the elasticity seemed to be weaken.2. Serum bilirubin of jaundice group increased significantly compared to the non-jaundiced group (P < 0.01). The bilirubin of 3d group elevated dramatically when compared with 7d group and 14d group, but there was no difference between the latter two groups.3. Vasoconstrictor reactivity. The constriction amplitude of thoracic aorta rings in BDL group reduced significantly (P<0.01) after three times of 60mmol/L K+ solution stimulation compared to sham group at all time points. However, there were no differences in BDL subgroups. The vasoconstrictor responses of thoracic aorta rings strengthened as the concentration of NE and PE increased in a dose-dependent manner. However, 10-6mmol/L NE triggered the peek constriction and the reaction decreased when NE increased further. The constriction amplitude of thoracic aorta rings in BDL reduced significantly at all the time points compared to the sham group (P<0.01). There were no differences (P>0.05) in BDL subgroups in small doses while 3d BDL group showed increased constriction compared with 7d and 14d BDL group (P<0.05). No significant differences were found among sham subgroups (P>0.05).4. Vasodilator reactivity. The thoracic aorta rings were stimulated with NE 10-6mmol/L and the constriction value is defined as 100%. Different doses of SNP were given and the constriction responses of thoracic aorta rings were reduced. The reduce percentage of BDL group was greater than the sham group, but no differences were observed among different time points of BDL group or sham group.5. Ultrastructure of the thoracic aorta. The electronmicroscopy of the aortic endothelial cells of sham rats showed normal structure of the endothelial gap and tight junctions. In the endothelial cells of BDL 3d group, fractured microvillus, lightly expanded endoplasmic reticulum, loosened mitochondria ground substance, thickened mitochondrial crista and small vacuolus in endochylema were observed. There were no obvious changes of vascular smooth muscle cells. In BDL 7d group, endothelial cells showed space areas and canals in endochylema, lighted ground substance, extended gap to vascular smooth muscle, expanded endoplasmic reticulum, lighted mitochondria ground substance, partly disappeared mitochondrial crista and vacuolus-like changes. Vascular smooth muscle cells displayed widened nucleus distance, edged chromatin, disappeared mitochondrial crista and space areas in endochylema. In BDL 14d group, part amotic of endothelial cells, irregular nucleus, collected chromatin, gaps between nucleus and endochylema, apoptotic body, large vacuolus, expanded endoplasmic reticulum, swelling mitochondria and disappeared mitochondrial crista were observed. Vascular smooth muscle cells showed wide basement membrane, light ground substance and large vacuolus in endochylema.6. The expression ofα1D–AR in the thoracic aorta of BDL group reduced significantly compared to sham group. The BDL 3d group showed increased expression when compared with BDL 7d group and BDL 14d group and there were no difference between the latter two groups.Conclusion:The hemodynamic parameters including HR, SVR, CO and ABP reduced in patients with obstructive jaundice before anesthesia and the change extent increased in sevoflurane anesthesia compared to non-jaundice patients. In animal experiments, the vasoconstrictor reactivity of isolated thoracic aorta of obstructive jaundice rats decreased while the vasodilator reactivity increased compared to sham operated rats. Electron microscopy revealed the damaged ultrastucture of thoracic aorta especially in the endothelial cells. The expression ofα1D–AR in the thoracic aorta of BDL group reduced significantly compared to sham group. These data suggested a potential vascular mechanism underlying the effect of cholestasis on circulatory function during inhaled anesthesia.