Ultrasonic pulsed Doppler duplex system determination of portal hemodynamic changes in portal hypertension

Ultrasonic pulsed Doppler duplex system was used to observe the portal hemodynamic changes before and after shunting or nonshunting operations. The results of preoperative measurements revealed significant increases of blood flow volumes of portal and splenic veins in portal hypertension subjects, and a positive correlation was obtained in the subjects with portal hypertension. Postoperative results showed significant reduction of portal blood flow volume more after shunting than the nonshunting operations. The etiology of portal hypertension and the causes of portal hemodynamic changes due to operations were discussed.     

Validity of ultrasonic duplex system for measurement of the portal blood flow in patients with liver disease

The validity of an ultrasonic duplex system for assessment of portal blood flow was clinically investigated. The maximum portal blood flow velocity was measured using this system (X) in ten patients with liver disease, and data obtained were compared on patients simultaneously undergoing cineangiographic mapping of Lipiodol droplets released into the portal vein through an indwelling catheter (Y). A linear correlation between X and Y was statistically significant (r = 0.970, n = 13). The ultrasonic duplex system proved reliable for a quantitative assessment of portal hemodynamics.     

Validity of ultrasonic duplex system for measurement of the portal blood flow in patients with liver disease

The validity of an ultrasonic duplex system for assessment of portal blood flow was clinically investigated. The maximum portal blood flow velocity was measured using this system (X) in ten patients with liver disease, and data obtained were compared on patients simultaneously undergoing cineangiographic mapping of Lipiodol droplets released into the portal vein through an indwelling catheter (Y). A linear correlation between X and Y was statistically significant (r=0.970, n=13). The ultrasonic duplex system proved reliable for a quantitative assessment of portal hemodynamics.     

The effect of decreased portal blood flow on the biliary system

A disturbance in the regional portal blood flow adjacent to the dilated bile duct in the liver is often observed in patients with hepatolithiasis. The effects of this disturbed portal blood flow on the biliary system, with or without cholangitis, were therefore investigated. Young rabbits were divided into the following four groups; (1) controls that had a laparotomy only (n = 3), (2) those that had a ligation of the portal branch of the right posterior lobe (RP lobe) (PL) (n = 10), (3) those that had tubing inserted into the bile duct through the duodenal papilla (BS) (n = 10), and (4) PL + BS (n = 10). Despite marked atrophy of the RP lobe, no distinct changes were seen in the biliary systems of groups 1 or 2. In groups 3 and 4, however, infiltration of inflammatory cells and glandular proliferation in the wall of the markedly dilated extrahepatic bile duct (proliferative cholangitis (PC), characteristic to hepatolithiasis) were seen. Findings of PC were also noted in the intrahepatic bile duct of the atrophied RP lobes of these 2 groups. The incidence of PC was 20 per cent in group 3 and 60 per cent in group 4, respectively, but the PC of the intrahepatic bile ducts in group 3 was more localized than in group 4. Goblet cell metaplasia was seen in the epithelial cells of PC. Bacteriologically, bile samples were aseptic in groups 1 and 2, however, samples of bile from groups 3 and 4 were all contaminated with Escherichia coli or Streptococcus Faecalis. The biliary contents of phospholipids, total cholesterol and total bile acid were significantly decreased in groups 3 and 4, when compared with groups 1 and 2. In conclusion, a disturbance in portal blood flow, accompanied by cholangitis and segmental liver atrophy, may play an important role in the clinical course of hepatolithiasis.     

The effect of decreased portal blood flow on the biliary system

A disturbance in the regional portal blood flow adjacent to the dilated bile duct in the liver is often observed in patients with hepatolithiasis. The effects of this disturbed portal blood flow on the biliary system, with or without cholangitis, were therefore investigated. Young rabbits were divided into the following four groups; (1) controls that had a laparotomy only (n=3), (2) those that had a ligation of the portal branch of the right posterior lobe (RP lobe) (PL) (n=10), (3) those that had tubing inserted into the bile duct through the duodenal papilla (BS) (n=10), and (4) PL+BS (n=10). Despite marked atrophy of the RP lobe, no distinct changes were seen in the biliary systems of groups 1 or 2. In groups 3 and 4, however, infiltration of inflammatory cells and glandular proliferation in the wall of the markedly dilated extrahepatic bile duct (proliferative cholangitis (PC), characteristic to hepatolithiasis) were seen. Findings of PC were also noted in the intrahepatic bile duct of the atrophied RP lobes of these 2 groups. The incidence of PC was 20 per cent in group 3 and 60 per cent in group 4, respectively, but the PC of the intrahepatic bile ducts in group 3 was more localized than in group 4. Goblet cell metaplasia was seen in the epithelial cells of PC. Bacteriologically, bile samples were aseptic in groups 1 and 2, however, samples of bile from groups 3 and 4 were all contaminated withEscherichia coli orStreptococcus Faecalis. The biliary contents of phospholipids, total cholesterol and total bile acid were significantly decreased in groups 3 and 4, when compared with groups 1 and 2. In conclusion, a disturbance in portal blood flow, accompanied by cholangitis and segmental liver atrophy, may play an important role in the clinical course of hepatolithiasis.     

Influence of respiration and portal pressure on transabdominal duplex Doppler ultrasound measurement of portal blood flow: a porcine model for experimental studies

Transabdominal duplex Doppler ultrasonography (TDDU) is commonly used for measuring hepatic blood flow (HBF) in clinical practice. Flow velocity and the cross-sectional area (CSA) of vessels are obtained separately and used to compute blood flow. Respiration and changes in portal pressure are known to cause variations in the CSA of the portal vein, but the impact of these parameters on TDDU measurement of portal blood flow is unclear. Eight Yorkshire pigs (20.7-25.1 kg) were used for the study. TDDU determination of portal blood flow was carried out using CSA of the portal vein obtained at inspiration (maximal) and at expiration (minimal) for computation, and the differences obtained were compared. Determination of HBF was carried out simultaneously on the same animals using diisopropyliminodiacetic acid (DISIDA) clearance. A physiological increase in portal pressure was then created by 50% hepatectomy and TDDU measurement similarly carried out on the second postoperative day. Computing portal blood flow in the intact liver using maximal and minimal CSA gave rise to a mean difference of 7.0 ml kg(-1) min(-1) (P < 0.001). A significant correlation was obtained between HBF and portal flow computed from maximal CSA (Pearson's correlation = 0.85, P < 0.033). The respiratory index of the portal vein (maximal CSA/minimal CSA) decreased from 1.5 to 1.2 after hepatectomy, which also caused a 90% increase in portal pressure. Respiration and portal pressure thus significantly impact on TDDU determination of HBF, and in this porcine model, computation using maximal CS more accurately reflects HBF.     

Echocardiographic assessment of coronary blood flow velocity during controlled hypotensive anesthesia with nitroglycerin

OBJECTIVE: To determine the effect of nitroglycerin on coronary blood flow velocity during controlled hypotensive anesthesia in humans. DESIGN: Internally controlled prospective study. SETTING: Single university hospital. PARTICIPANTS: Twenty American Society of Anesthesiologists class I and II patients undergoing general anesthesia for surgical resection of a malignancy. INTERVENTIONS: General anesthesia was induced with thiopental, fentanyl, and succinylcholine and maintained with isoflurane and vecuronium. Transesophageal echocardiography was used to evaluate left ventricular wall motion and blood flow velocity in the left anterior descending coronary artery. Intravenous nitroglycerin was used to reduce systolic arterial pressure to 60 to 70 mmHg. Intravenous albumin 5% was administered to maintain pulmonary capillary wedge pressure >5 mmHg. MEASUREMENTS AND MAIN RESULTS: The left anterior descending coronary artery was visualized clearly in 16 of 20 patients. At a mean nitroglycerin dose of 16+/-14 microg/kg/min, peak diastolic left anterior descending flow velocity increased significantly from 32.5+/-10.3 cm/sec to 44.7+/-14.6 cm/sec (p = 0.0103). None of the patients developed any ST-segment changes. CONCLUSIONS: During nitroglycerin-induced hypotensive anesthesia, coronary blood flow as assessed by peak diastolic left anterior descending flow velocity is preserved or increased in most patients. Increases in left anterior descending flow velocity are predictably achieved only at nitroglycerin doses >5 microg/kg/min. Intraoperative transesophageal echocardiography is useful in monitoring coronary flow velocity responses to controlled hypotensive anesthesia.     

Measurement of mesenteric blood flow by duplex scanning

Ultrasonic imaging combined with a pulsed Doppler unit (duplex scanning) allows the noninvasive assessment of blood flow of the superior mesenteric artery. The changes in mesenteric blood flow associated with a standardized (1000 kcal) food load were measured and the results were compared with blood flow of the left common carotid artery. Twenty healthy subjects (aged 30.1 +/- 5 years) were studied fasting (12.4 +/- 2.6 hours' duration) and six times with a 15-minute interval after the test meal. The diameters of the superior mesenteric artery (0.60 +/- 0.09 mm) and of the common carotid artery (0.61 +/- 0.05 mm) were measured from the B-mode image. The Doppler frequency spectra were used to determine peak systolic, late systolic, and end-diastolic velocity and to compute the mean velocity. Although the flow parameters of the common carotid artery were virtually unaffected by food intake, a steep increase in mesenteric blood flow velocity and volume flow was observed. At rest, blood flow through the mesenteric artery was 6.3 +/- 2.6 ml/sec and 9.5 +/- 2.1 ml/sec in the carotid artery. After the test meal, mesenteric artery blood flow increased significantly (p less than 0.0001) and reached maximal hyperemia (20.3 +/- 7.4 ml/sec) after 45 minutes. The measurement of mesenteric blood flow before and after a test meal characterizes intestinal hemodynamics and should be suitable to evaluate ischemic disease and other disorders that lead to changes of mesenteric blood flow.     

Azygos venous blood flow in portal hypertension

Azygos venous blood flow estimated by the continuous thermodilution method was measured in 48 patients with portal hypertension. In patients with cirrhosis, azygos venous blood flow was 326 +/- 139ml/min (mean SD) and was significantly higher than in patients without portal hypertension (163 +/- 61ml/min). In patients with idiopathic portal hypertension and extrahepatic portal obstruction, azygos venous blood flow was 411 +/- 227ml/min and 328 +/- 85ml/min respectively. Azygos venous blood flow was significantly correlated with the hepatic venous pressure gradient but neither with cardiac output nor with size of esophageal varices. In eleven cirrhotic patients, azygos venous blood flow and other hemodynamic parameters were measured before and after the nonshunting operation of esophageal transection, splenectomy and esophagogastric devascularization. Azygos venous blood flow and hepatic venous pressure gradient were significantly reduced after operation. On the other hand, cardiac output did not change significantly after surgical procedure. Relatively high postoperative azygos venous blood flow indicates its important role in the postoperative collateral circulation.     

The effects of propofol on cerebral blood flow in correlation to cerebral blood flow velocity in dogs

This study correlates the effects of propofol on cerebral blood flow (CBF) and middle cerebral artery blood flow velocity in dogs. CBF was measured using radioactive microspheres. Cerebral oxygen consumption (CMRO2) was measured with each CBF determination. Blood flow velocity was measured through a transtemporal window using a pulsed 8 MHz transcranial Doppler ultrasound system (TCD). Electroencephalogram (EEG) was continuously recorded over both cerebral hemispheres. Cardiac output (CO) was measured using an electromagnetic flow probe placed on the pulmonary artery. Baseline measures were made in all dogs (n = 11) with 0.7% isoflurane end tidal and 50% N2O in O2. There were two treatment groups. In group 1 (n = 6), propofol (0.8 mg/kg/min) was infused and a second measurement made at induction of EEG burst suppression (12 +/- 2 min). CBF and CMRO2 decreased by 70% and mean blood flow velocity decreased by 60%. Blood pressure, heart rate, and CO did not change. Propofol infusion was discontinued and all parameters were measured following recovery of EEG to baseline activity (48 +/- 9 min). CBF and blood flow velocity increased 35 and 25%, respectively, and CMRO2 increased by 32% during this period. A second propofol infusion (0.8 mg/kg/min) was started and all cerebral and systemic hemodynamic parameters were again determined at induction of EEG burst suppression (12 +/- 2 min). CBF decreased 35% and blood flow velocity decreased 25% to levels seen during the first propofol infusion. Over the entire study, changes in CBF correlated with changes in blood flow velocity (r = 0.86, p < 0.05). In group 2 (n = 5), four control measures were made at the same time intervals as in group 1. Baseline CBF and blood flow velocity were lower in group 2 compared to group 1 but these measures did not change over time. Our results show that propofol produces marked decreases in CBF in dogs and that these changes are closely correlated with CBF velocity.     

Renal transplant blood flow evaluation by ultrasonic duplex scanning

The transplant blood flow was measured renal transplantation by ultrasonic duplex scanner composed of pulsed Doppler flowmeter and real-time B-mode linear scanner in 32 patients. The blood flow information could be obtained from anywhere of interest within the renal transplant. Then blood flow in 3 regions including renal hilum, central echoes and renal parenchyma were measured. The parenchymal peripheral blood flow was not always similar to the hilar central blood flow. Parenchymal blood flow was the most correlated with graft function and decreased remarkably during acute rejection episode. This method enabled detection of occurrence of acute rejection in the course of post-cadaver transplant ATN. Prolongation of delta t (acceleration time) in Doppler spectrogram from parenchyma was also reliable evidence for the deterioration of graft function. Ultrasonic duplex scanning is a useful method in managing post-transplantation patients because intrarenal hemodynamics can be evaluated by this method.     

Hepatofugal portal blood flow in hepatic cirrhosis.

A variety of indirect techniques has been claimed to provide evidence of spontaneous reversal of portal blood flow in hepatic cirrhosis but the existence of the phenomenon has been doubted by some who do not accept the validity of the indirect evidence. There are few reports of the demonstration of hepatofugal portal flow by selective hepatic arteriography, which is the only acceptable technique. We report three patients with histologically confirmed cirrhosis in whom hepatofugal portal blood flow was unequivocally demonstrated by arteriography, in whom no surgical portosystemic shunt had been performed and in whom there was no evidence of the Budd-Chiari Syndrome or hepatoma, situations accepted as associated with reversed portal blood flow. Theoretical considerations suggest that shunt surgery for bleeding esophageal varices should not be ruled out on the grounds of hepatofugal portal flow. However, end-to-side portacaval anastomosis and distal splenorenal shunt might predispose to the early redevelopment of esophageal varices when reversed portal flow is present. Side-to-side portacaval and conventional splenorenal shunts might be preferable in having less effect on hepatic parenchyma perfusion than when orthograde portal flow in the case.     

Auxiliary canine hepatic transplantation without portal blood flow

Auxiliary liver transplantation for acute reversible hepatic failure has been suggested as a way to provide temporary hepatic support. The major technical difficulty in such an operation is providing portal blood flow, although it is unclear if this is necessary for short-term function of such a graft. Three groups of five dogs each underwent common duct ligation and cholecystectomy. One week later all animals underwent an end-to-side portocaval shunt. In Group I dogs only a "sham" transplant was done while those in Group II also received an auxiliary hepatic graft without portal blood flow which had been perfused with iced Collins solution and immediately grafted. Group III received similar auxiliary hepatic grafts with 22 hours of cold ischemia time. Reductions in mean total serum bilirubin values to near normal, usually lasting for one week (Group I, 12.02 mg% +/- 1.23 SEM vs. Group II, 3.58 mg% +/- 0.52 SEM, p = 0.01) were observed. Although several livers stored for 22 hours demonstrated function, there was considerable evidence of ischemic injury.     

Influence of aortic blood flow velocity on changes of middle cerebral artery blood flow velocity during isoflurane and sevoflurane anaesthesia

BACKGROUND AND OBJECTIVE: We studied the influence of systemic (aortic) blood flow velocity on changes of cerebral blood flow velocity under isoflurane or sevoflurane anaesthesia. METHODS: Forty patients (age: isoflurane 24-62 years; sevoflurane 24-61 years; ASA I-III) requiring general anaesthesia undergoing routine spinal surgery were randomly assigned to either group. Cerebral blood flow velocity was measured in the middle cerebral artery by transcranial Doppler sonography (depth: 50-60 mm). Systemic blood flow velocity was determined by transthoracic Doppler sonography at the aortic valve. Heart rate, arterial pressure, arterial oxygen saturation and body temperature were monitored. After standardized anaesthesia induction (propofol, remifentanil, vecuronium) sevoflurane or isoflurane were used as single agent anaesthetics. Cerebral blood flow velocity and systemic blood flow velocity were measured in the awake patient (baseline) and repeated 5 min after reaching a steady state of inspiratory and end-expiratory concentrations of 0.75, 1.00, and 1.25 mean alveolar concentrations of either anaesthetic. To calculate the influence of systemic blood flow velocity on cerebral blood flow velocity, we defined the cerebral-systemic blood flow velocity index (CSvI). CSvI of 100% indicates a 1:1 relationship of changes of cerebral blood flow velocity and systemic blood flow velocity. RESULTS: Isoflurane and sevoflurane reduced both cerebral blood flow velocity and systemic blood flow velocity. The CSvI decreased significantly at all three concentrations vs. 100% (isoflurane/sevoflurane: 0.75 MAC: 85 +/- 25%/81 +/- 23%, 1.0 MAC: 79 +/- 19%/74 +/- 16%, 1.25 MAC: 71 +/- 16%/79 +/- 21%; [mean +/- SD] P = 0.0001). CONCLUSIONS: The reduction of the CSvI vs. 100% indicates a direct reduction of cerebral blood flow velocity caused by isoflurane/sevoflurane, independently of systemic blood flow velocity.