Modified Doppler flowmetry in the splanchnic circulation

A Novel Technique to Measure Splanchnic Transit Time Using Microbubble Ultrasound

OBJECTIVE

The objective of this study was to measure splanchnic transit time by intravenous injection of a microbubble.

MATERIALS AND METHODS

Ten volunteers were examined before and after eating. After Doppler indices of splanchnic circulation were obtained, the superior mesenteric artery (SMA) and vein (SMV) were simultaneously interrogated using power Doppler ultrasound after intravenous injection of a microbubble. Contrast arrival in the SMA and subsequently the SMV was recorded and splanchnic transit time calculated from differences in the time-intensity curves.

RESULTS

Splanchnic transit time decreased significantly after eating (mean 11 vs. 6.9 seconds; P = 0.007), reflecting splanchnic hemodynamics. Between-subject variability attributable to repeated measurements was least for the SMA resistive index (17%) but 56% for the new index, suggesting poor reproducibility.

CONCLUSION

Splanchnic transit time may be measured by microbubble injection but is subject to considerable measurement error. Newer microbubbles and imaging methods may allow more reproducible measurements.

Influence of food composition on splanchnic blood flow during digestion in unsedated normal dogs: a Doppler study

The effect of dietary components in gastrointestinal blood flow was investigated non-invasively in dogs. Doppler ultrasound (US) waveform analysis of the celiac artery (CA) and the cranial mesenteric artery (CMA) of eight healthy dogs was performed both in the fasting state and at 20, 40, 60 and 90 min after feeding maintenance, high protein, high carbohydrate and high fat diets. Resistive index (RI), pulsatility index (PI) and the percentage differences between measurements were calculated. In fasted dogs, the CA showed significantly (p<0.05) lower resistance than the CMA. With all diets, post-prandial RI and PI values decreased significantly in both vessels (CA: RI=-12-13%; PI=-25-29%; CMA: RI=-13-15%; PI=-27-29% [p<0.05]), and in all cases significantly earlier in the CA than in the CMA (p<0.05). With all diets except high fat the maximum decrease in RI and PI was reached in the CA at 40 min and in the CMA at 60 min. High fat diets were unique in that the maximum decrease in RI and PI in the CMA occurred earlier (at 20 min) and values were slower to return to normal (p<0.05). We conclude that Doppler US can be used in dogs to quantify significant differences in the response of splanchnic blood flow to different dietary components.

Inter-observer and intra-observer variability in hepatology

OBJECTIVES

A determination of the inter-observer variability is an important step before determining diagnostic accuracy and requires a specific methodology and statistical tests. The aim of this study was to report the results, characteristics and methodological quality of agreement studies performed in hepatology.

METHODS

A search of published studies yielded 42 that could be used in this evaluation: three were clinical studies, 11 were in the field of endoscopy, 12 in histopathology and 16 in radiology. The studies were described with a grid of 28 items and evaluated with a quality score (QUAS; maximum, 35) including 22 items.

RESULTS

The following agreement level was noted: intra-observer > inter-observer > inter-centre. The following signs had good agreement. Endoscopy: size and red signs of oesophageal varices; histopathology: cirrhosis, fibrosis and steatosis; Doppler: mean portal vein and superior mesenteric artery velocities, hepatic artery area and perfusion indexes. Frequent methodological weaknesses were noted. The real agreement (such as the kappa index excluding chance), and the prevalence of signs and biases were rarely assessed. Standardized observations (67% of the studies), blind assessment (48%), simultaneous observations (7%), and the recording technique were not frequently used. The mean QUAS was 13 +/- 6 with 17 +/- 4 in histopathology versus 11 +/- 6 in radiology (P < 0.05). Using multiple regression, four variables independently predicted the QUAS with R2 = 0.77: adapted tests, multiple observations, intra-class correlation coefficient and agreement proportion.

CONCLUSIONS

Methodology was often insufficient. Agreement is often measured under biased conditions. Some areas were not or were rarely studied, e.g., biology and ultrasound. The agreement and QUAS were often poor, suggesting the need for studies with improved observation and methodological quality of agreement.

Splanchnic blood flow and oxygen uptake during cardiopulmonary bypass

OBJECTIVE

To measure splanchnic blood flow (SBF) with 2 indicator dilution techniques during and after cardiopulmonary bypass (CPB), to compare the results with transesophageal echocardiography Doppler-measured right hepatic vein (RHV) flow, and to study gastric tonometry data in the same patients.

DESIGN

Single-arm prospective study.

SETTING

University hospital operating room and intensive care unit.

PARTICIPANTS

Ten adult patients undergoing cardiac surgery.

INTERVENTIONS

SBF was measured using constant rate infusion of indocyanine green dye and low-dose ethanol from induction of anesthesia until end of hypothermic CPB. The infusion of ethanol was continued, and SBF was measured postoperatively at 2, 3, and 4 hours after CPB. Simultaneously, RHV flow, splanchnic oxygen delivery and uptake, and gastric mucosal pH were calculated.

MEASUREMENTS AND MAIN RESULTS

SBF, RHV flow, and gastric mucosal pH remained unchanged during the study period. SBF measured with indocyanine green was 765 +/- 88 (SEM) mL/min after induction of anesthesia. SBF before CPB measured with ethanol was 985 +/- 218 mL/min. There was no significant difference between the methods. RHV flow was 450 +/- 87 mL/min after induction of anesthesia. There was no correlation between individual values of RHV flow and SBF. Splanchnic oxygen uptake was 52 +/- 7.8 mL/min after induction of anesthesia and decreased to 28 +/- 2.6 mL/min during CPB. Gastric mucosal pH was 7.32 +/- 0.02 after induction of anesthesia and showed no correlation to SBF or to splanchnic oxygen uptake.

CONCLUSION

SBF did not decrease during CPB. SBF could be measured with ethanol with reasonable accuracy. Transesophageal echocardiography assessment of RHV flow was not suitable to quantify SBF in the individual patient, but could be used to follow relative changes.

Hepatic arterial blood flow in large hepatocellular carcinoma with or without portal vein thrombosis: assessment by transcutaneous duplex Doppler sonography

BACKGROUND

As liver cirrhosis progresses, the portal venous blood (PVBF) flow decreases, accompanied by an increase in hepatic arterial blood flow. Large hepatocellular carcinoma is a hypervascular tumour with a rapid growth, which seems to require an increase of the tumoral arterial blood flow. Furthermore, hepatocellular carcinoma is frequently associated with portal vein thrombosis, which subsequently impedes portal blood supply.

METHODS

The purpose of our study was to estimate alterations in the hepatic arterial blood flow in large hepatocellular carcinomas occurring in liver cirrhosis, in comparison with liver cirrhosis and controls. Liver blood flow measurements were determined by duplex Doppler sonography in 47 patients with large hepatocellular carcinomas (13 with portal vein thrombosis and 34 without this thrombosis), 42 liver cirrhosis patients and 30 controls. The Doppler perfusion index was calculated as the ratio of hepatic arterial blood flow to total hepatic blood flow.

RESULTS

The patients with liver cirrhosis had a significant increase of hepatic arterial blood flow as compared to controls (P < 0.001), accompanied by a significant reduction in PVBF (P < 0.005). As a result, the Doppler perfusion index was increased in patients with liver cirrhosis as compared to controls (P < 0.001). The hepatic arterial blood flow was increased in patients with hepatocellular carcinoma but without portal vein thrombosis as compared to the cirrhotic patients (P < 0.001), with a significant reduction of PVBF (P < 0.001). Hepatic arterial blood flow was also increased in patients with both hepatocellular carcinoma and portal vein thrombosis as compared to the patients without this thrombosis (P < 0.001).

CONCLUSION

These results suggest that in large hepatocellular carcinomas there is a decreased PVBF, accompanied by an increased hepatic arterial blood flow. The hepatic arterial buffer response seems to be active in hepatocellular carcinomas and maintains liver perfusion to adequate levels.

[Hepatosplenic schistosomiasis portal hypertension: effect of esophagogastric devascularization with splenectomy on the diameter and mean flow velocity in the portal system (ultra-sonographic Doppler]

BACKGROUND

Esophagogastric devascularization with splenectomy has been used for the treatment of upper digestive bleeding due to esophagic varices in hepatoportal mansoni's schistosomic portal hypertension. Nevertheless, early portal thrombosis has hampered this surgical technique (13.3% and 53.2%), compromising the good results on the hemorrhagic side. Supposing that portal circulatory changes, due to the surgical treatment, may play an important role in this kind of complication, our objective was to identify the hemodynamic facilitating factors. Portal hemodynamic aspects, identified by ultra-sonographic Doppler study, from two groups of patients: non-operated upon and splenectomized with esophagogastric devascularization in late post-operatory phase (in excess of 6 moths), with portal hypertension due to mansoni hepatoesplenic portal hypertension and in similar clinical conditions, were compared.

METHOD

Fifty eight ambulatorial patients were studied, all had portal hypertension caused by mansoni's hepatosplenic schistosomiasis and previous bouts of digestive bleeding. They were divided in two groups: A--29 followed clinically/endoscopically, and group B--29 previously submitted to esophagogastric devascularization with splenectomy. In all was measured the diameter and mean flow velocity in the portal vein and its right and left branches by ultra-sonographic Doppler study. The results were submitted to statistical analysis for inter- and intra-group comparison.

RESULTS

Group A (non-operated): the portal vein diameter was greater than the right and left branches (10.6 +/- 2.9, 8.0 +/- 1.8, 9.1 +/- 2.6 cm), the mean flow velocities in the portal vein and its branches were similar (15.62 +/- 6.17, 14.92 +/- 5.33, 16.12 +/- 4.18 cm/seg). Group B (operated): the diameter and mean flow velocity in all vessels were reduced (8.8 +/- 1.7, 5.2 +/- 1.2, 7.5 +/- 2.2 cm/12.53 +/- 2.60, 8.86 +/- 1.75, 9.69 +/- 3.75 cm/seg).

CONCLUSIONS

After esophagogastric devascularization with splenectomy, there was a reduction of the diameter and mean flow velocity in the portal vein, its right and left branches.

Effect of cisapride on portal haemodynamics in patients with liver cirrhosis using duplex Doppler ultrasonography

PURPOSE

Cisapride, a benzimide derivative, is a gastrointestinal prokinetic agent without dopamine-antagonistic or cholinomimetic effects. This study aims at assessing the effect of cisapride oral administration on portal flow in patients with advanced post hepatitic cirrhosis using duplex Doppler ultrasound (US).

METHODS

A total of 12 patients with post-hepatitic liver cirrhosis were included in the study. Duplex Doppler sonographic examinations were performed before and after treatment. The subjects received 10 mg cisapride before starting the measurement procedure and then three times a day for 2 days. Portal haemodynamics including vessel diameters (mm), mean flow velocities (cm/s), blood flows (ml/min) were investigated.

RESULTS

Mean portal vein diameters, mean portal flow velocity and portal blood flow volume showed decreases of 18.6, 22.1 and 43.6% (P<0.001), respectively. After cisapride administration the portal vein diameter did not change in two patients and the portal vein velocity did not change in three patients. No significant change was found in systolic blood pressure, diastolic blood pressure or pulse rate after the administration of cisapride.

CONCLUSION

In this study, it was demonstrated that oral administration of cisapride results in a significant reduction of portal blood flow but there were no changes in heart rate or systolic pressure in patients with cirrhosis of the liver.

Hepatic arterial blood flow velocities: assessment by transcutaneous and intravascular Doppler sonography

BACKGROUND/AIMS

Doppler sonography has been used to assess hepatic arterial perfusion in a number of published reports. However, adequate validation studies are available for neither the transcutaneous nor the intravascular Doppler approach. The aim of this comparative study was to assess hepatic arterial perfusion with both methods.

METHODS

In 15 patients the right hepatic artery was examined with intravascular and transcutaneous Doppler sonography after calibration of Doppler devices in vitro with a thread model. The measurements were performed simultaneously in five and separately within 24 h in 10 patients.

RESULTS

In vitro, the correlations between the velocities of the thread and the velocities as determined by intravascular (r=1.0, p<0.001) and transcutaneous Doppler sonography (r=1.0, p<0.001) were excellent. In vivo, the best correlation was found for systolic peak velocities (intravascular: 58.5+/-18.1 cm/s, mean+/-standard deviation, transcutaneous: 58.2+/-25.2 cm/s, r=0.63, p=0.01). Although lower mean (intravascular: 26.5+/-7.7 cm/s, transcutaneous: 32.5+/-14.4 cm/s) and end-diastolic velocities (intravascular: 11.5+/-4.0 cm/s, transcutaneous: 18.4+/-8.6 cm/s) were found with intravascular compared to transcutaneous Doppler sonography, significant correlations were demonstrable between results obtained by both methods (r=0.63, p=0.01 for mean and r=0.57, p=0.025 for diastolic velocities). Similarly, the calculated resistive (intravascular: 0.79+/-0.07, transcutaneous: 0.68+/-0.06, r=0.65, p=0.009) and pulsatility indices (intravascular: 1.78+/-0.47, transcutaneous: 1.26+/-0.25, r=0.55, p=0.034) were somewhat higher using the intravascular device, but correlated well with the numbers obtained by the transcutaneous approach.

CONCLUSIONS

The data suggest that with use of different Doppler devices, systolic velocities are the most suitable parameter for Doppler assessment of hepatic arterial perfusion.

Mesenteric blood flow is related to disease activity and risk of relapse in Crohn's disease: a prospective follow-up study

OBJECTIVE

The diagnostic significance of increased splanchnic blood flow in Crohn's disease is unclear. This prospective study was therefore undertaken to define the role of Doppler sonography in the assessment of disease activity and in the prediction of early relapse.

METHODS

Splanchnic flowmetry was performed in 59 patients with Crohn's disease and 20 healthy volunteers during fasting and 30 min after ingestion of a standardized meal. Twenty-one patients measured during the active state and in clinical remission were followed-up for 6 months. Hemodynamic parameters of the superior and inferior mesenteric arteries and the portal vein were related to clinical (Crohn's disease activity index [CDAI]), laboratory (C-reactive protein), and endoscopic (Crohn's Disease Endoscopic Index of Severity) parameters of disease activity.

RESULTS

The postprandial mean velocity of the superior mesenteric artery correlated closest with clinical activity (CDAI, p < 0.005) and C-reactive protein (p < 0.01), but was unrelated to endoscopic activity. All patients in remission after 6 months (9/9) showed an increase in postprandial pulsatility index of the superior mesenteric artery, compared with an initial measurement during active disease (+28%). In contrast, the majority of patients with later relapse or surgery (11/12) had decreased pulsatility index during initial remission (-20%). The positive predictive value of this index for maintenance of remission was 0.82.

CONCLUSIONS

Postprandial flow measurements in the superior mesenteric artery are closely related to clinical but not endoscopic disease activity in patients with Crohn's disease. The repeated measurement of the postprandial pulsatility index allows estimation of the risk of recurrence.

Hepatic arterial flow volume and reserve in patients with cirrhosis: use of intra-arterial Doppler and adenosine infusion

BACKGROUND & AIMS

In cirrhosis, liver blood flow becomes increasingly dependent on the hepatic artery. The aim of this study was to investigate hepatic arterial blood flow volume and resistance and hepatic arterial flow reserve in relation to liver function and systemic hemodynamic alterations in patients with cirrhosis.

METHODS

In 38 patients with cirrhosis, liver function, cardiac output, and systemic vascular resistance were studied, and hepatic arterial blood flow velocity, flow volume, and pulsatility index at baseline and during intra-arterial administration of adenosine (2-40 microg. min-1. kg body wt-1) were assessed by angiography combined with intravascular Doppler flowmetry.

RESULTS

Hepatic arterial flow velocity was 21 +/- 11, 31 +/- 17, and 41 +/- 27 cm/s; flow volume was 266 +/- 246, 342 +/- 289, and 417 +/- 220 mL/min; and pulsatility index was 2.2 +/- 0.7, 1.7 +/- 0.6, and 1.5 +/- 0.5 in Child-Pugh classes A, B, and C, respectively (differences not statistically significant). Adenosine-induced changes in these parameters were more marked in Child-Pugh class A (68 +/- 15 cm/s, 1246 +/- 486 mL/min, and -1.14 +/- 0.5) than in class C (45 +/- 23, P < 0.05; 704 +/- 492, P = 0.02; and -0.58 +/- 0.38, P < 0.05). Using analysis of variance, cardiac index, systemic vascular resistance, and ascites, but not Child-Pugh class, were related to baseline values and adenosine-induced changes.

CONCLUSIONS

Adenosine is a potent dilator of the hepatic artery in humans. The data suggest that hepatic arterial blood flow and adenosine-dependent flow reserve in patients with cirrhosis are under systemic hemodynamic or neurohormonal control.

The postprandial portal flow is related to the severity of portal hypertension and liver cirrhosis

BACKGROUND/AIMS

Diminished postprandial portal hyperemia has been demonstrated by echo-Doppler flowmetry in patients with liver cirrhosis, but its diagnostic role is unclear. This prospective study was therefore undertaken in patients with varying severity of portal hypertension and degree of liver cirrhosis.

METHODS

Portal flowmetry was performed in 66 patients with cirrhosis and 20 healthy volunteers during fasting and 30 min after ingestion of a standardized meal. Hemodynamic parameters were related to the degree of esophageal varices, variceal bleeding, portal hypertensive gastropathy and Child-Pugh score.

RESULTS

The postprandial portal blood velocity increment was low in patients with esophageal varices of any degree (22-24%), compared to patients without varices (49%, p<0.01) and healthy controls (65%, p<0.001), but was not different in patients with or without variceal bleeding (22% vs. 20%). In contrast, the congestion index (CI; ratio of portal vein cross-sectional area and portal blood velocity) pre-/postprandial decreased in the bleeding group only (CI pre/ CI post 1.30+/-0.23 (no bleeding) vs. 0.86+/-0.29 (bleeding); p<0.01). Portal hypertensive gastropathy was not related to any of the portal flow parameters. The portal blood velocity increment was comparable in controls (65%) and patients with Child-Pugh class A cirrhosis (56%), but lower in patients with class B (32%) and class C cirrhosis (15%, p<0.05 vs. class A). Also, there was no postprandial decrease in congestion index in patients with the most severe cirrhosis (p<0.01 class C vs. class A and B).

CONCLUSIONS

The postprandial rise in portal flow is inversely related to the severity of portal hypertension and liver cirrhosis, and may be a valuable parameter with respect to the risk of variceal bleeding.

Superior mesenteric artery blood flow in children with celiac disease

BACKGROUND

Knowledge of splanchinic hemodynamics in celiac disease is scarce. The hemodynamic parameters of the superior mesenteric artery were evaluated by duplex Doppler ultrasonography in children with celiac disease to show whether histomorphologic changes in small bowel mucosa led to any alteration in splanchinic blood flow.

METHODS

The hemodynamic parameters of the superior mesenteric artery were evaluated by Doppler ultrasonography in 23 children with celiac disease. Ten patients were studied at the time of diagnosis. The remaining 13 children were studied after complete clinical and histologic recovery induced by gluten-free diet. Additionally, 9 patients out of 13 who were on a gluten-free diet for about 2 years were given gluten challenge, and superior mesenteric artery blood flow was measured after the challenge. The results were compared with those of healthy children.

RESULTS

Peak systolic velocity of the superior mesenteric artery was higher in untreated celiac patients than in healthy controls and treated celiac patients. Peak systolic velocity of the superior mesenteric artery in the treated group of children was close to that of control subjects, implying that successful treatment with gluten-free diet improves hemodynamic changes. The comparison of Doppler ultrasonographic measurements of the challenge group before and after the gluten challenge revealed that the peak systolic velocity, resistive index, and blood flow of the superior mesenteric artery were changed significantly.

CONCLUSIONS

The pathophysiologic events in small bowel mucosa during the active phase of celiac disease induce some hemodynamic changes that can be detected noninvasively by duplex Doppler ultrasonography.

Effect of verapamil on portal and splanchnic hemodynamics in patients with advanced posthepatitic cirrhosis using duplex Doppler ultrasound

PURPOSE

To assess the effect of verapamil (80 mg) oral administration on portal and splanchnic hemodynamics in patients with advanced posthepatitic cirrhosis using duplex Doppler ultrasound (US).

METHODS

Fourteen patients with post-hepatitic liver cirrhosis were included in the study. Duplex Doppler sonographic examinations were performed before, and 2-3 h after, 80 mg verapamil oral administration. Portal and splanchnic hemodynamics including vessel diameters (mm), mean flow velocities (cm/s), blood flows (ml/min), Doppler indices such as pulsatility and resistive indices (PI and RI), were investigated before and after verapamil administration.

RESULTS

After verapamil administration; diameter of portal vein, splenic vein, and superior mesenteric artery (SMA) showed increase of 8%, 10%, and 7% (P < 0.05 to < 0.001), respectively. Increases of 20%, 38%, and 47% were found in blood flows (P < 0.05 to < 0.0001) with respect to the above vessels. Decreases of 17%, 10%, 11%, and 7% were found in SMA PI, SMA RI, splenic artery (SA) PI, and SA RI, respectively (P < 0.05 to < 0.0001).

CONCLUSIONS

Verapamil appears to have splanchnic, portal, splenic, portocollateral and probably intrahepatic vasodilator effects in patients with advanced posthepatitic liver cirrhosis. Verapamil should be further investigated in the treatment of patients with advanced liver cirrhosis with prospective studies measuring portal and wedged hepatic pressure.

A comparison of Doppler flowmetry with conventional assessment of acute changes in hepatic blood flow

The validity and clinical relevance of Doppler flowmetry in measuring changes in regional blood flow are uncertain. In the present study we compared changes induced ketanserin in regional splanchnic blood flow as measured by Doppler flowmetry with changes in conventionally measured systemic and in hepatic haemodynamic indices estimated pharmacokinetically using indocyanine green. Fourteen patients with alcoholic cirrhosis and portal hypertension were evaluated. On multivariate analyses, significant associations were noted for only three indices: changes in estimated hepatic blood flow were predicted jointly by changes in flow in the main and right portal veins and hepatic artery (R2 = 0.80); changes in intrahepatic shunting (indocyanine green extraction) were predicted by changes in flow in the main and right portal veins (R2 = 0.55); and changes in sinusoidal perfusion (indocyanine green clearance) were significantly predicted by changes in main portal vein flow alone (R2 = 0.76). These data support the validity of Doppler flowmetry in quantifying change in regional blood flow, but highlight the limitations in its clinical application and interpretation. The association of changes in main portal vein flow with changes in sinusoidal perfusion has clinical potential but requires confirmation using other modulating drugs.