Measurement Of Splanchnic Blood Flow Research Articles

The influence of the gastrointestinal tract and the liver on cystatin C serum concentrations

Objective. The purpose of this study in humans was to examine the influence of the gastrointestinal tract and liver on the serum concentrations of cystatin C. Methods. Eighteen healthy volunteers and 28 patients suspected of having chronic intestinal ischemia underwent catheterization of the abdominal aorta and the central hepatic vein. Blood samples were taken simultaneously from the abdominal aorta and the central hepatic vein 60, 90 and 120 minutes after the start of the investigation. After the first blood sample, a standard liquid meal was ingested. Measurement of splanchnic blood flow was performed using the Fick principle with constant infusion of 99mTc-Bridatec®. Angiography was performed at the end of the investigation. Results. The splanchnic blood flow increased significantly postprandially in the healthy volunteers and in the patients with normal angiography by 0.613–0.698 L/min and increased non- significantly in the patients with abnormal angiography (n = 5) by 0.135 L/min on average. ANOVA and the Bonferroni's multiple comparison test showed no significant difference between the means of cystatin C, creatinine or urea in the samples taken 60, 90 and 120 minutes after the start of the investigation in the abdominal aorta and the hepatic vein in the healthy volunteers or in the patients suspected of chronic intestinal ischemia with normal angiography. Conclusion. There was no indication of hepatic elimination of cystatin C, creatinine or urea. The serum concentrations of cystatin C, creatinine and urea in the central hepatic vein and the abdominal aorta were independent of the splanchnic blood flow.

The effect of insulin and glucagon on splanchnic oxygen consumption.

The purpose of these experiments was to measure the influence of insulin and glucagon on the splanchnic oxygen consumption. Two experiments were performed. In one experiment, the influence of hyperinsulinaemia was investigated in six healthy subjects, who were studied during a euglycaemic hyperinsulinaemic clamp. In another experiment, the influence of glucagon was investigated in seven healthy subjects, who were studied twice during a pancreatic islet clamp with either supplementation of insulin and glucagon, or of insulin alone. In both situations the measurements were performed during euglycaemia. Splanchnic oxygen consumption and net substrate balances were studied by the arterio-hepatic venous catheterisation technique and measurement of splanchnic blood flow in all experiments. During the euglycaemic hyperinsulinaemic clamp, the splanchnic blood flow increased significantly and the splanchnic oxygen consumption decreased by about 20%, while the net splanchnic glucose output reversed to a net uptake. In the pancreatic islet clamp experiments there was a significant difference between the net splanchnic glucose outputs whether glucagon and insulin or only insulin was supplemented. In spite of this, the splanchnic oxygen consumption decreased by about 20% in both situations, i.e. independent of glucagon supplementation. In both experiments there was a pronounced inhibition of lipolysis, which led to decreased fatty acids availability to the liver. This resulted in a concomitant decrease in hepatic ketone body formation. This decrease could account for about 30% of the decrease in splanchnic oxygen consumption. The reduction in splanchnic oxygen consumption can be explained by decreased ketogenesis, decreased protein synthesis and changes in splanchnic fuel selection, while changes in the rate of gluconeogenesis does not seem to play a significant role.

Variability of splanchnic blood flow measurements in patients with sepsis – physiology, pathophysiology or measurement errors?

Impaired tissue oxygenation, especially in the splanchnic region, may play a central role both in the pathogenesis of multiple organ dysfunction and in the development of complications in various groups of intensive care patients [1, 2]. In severe inflammation such as SIRS, septic infection, and septic shock, the metabolic demand for oxygen in the splanchnic region is increase [3, 4, 5]. This is explanied in part by and increased hepatic metabolism [6, 7]. In patients with normal or hyperdynamic hemodynamics, but the increase in oxygen consumption is disproportionate to the increase in blood flow.

Variability of splanchnic blood flow measurements using MR velocity mapping under fasting and post-prandial conditions - comparison with echo-Doppler

Background/Aims: The aim was to study the reproducibility of magnetic resonance velocity mapping, when measuring portal vein and superior mesenteric artery blood flow, under fasting and post-prandial conditions. Magnetic resonance flow measurements for the portal vein were compared with echo-Doppler measurements in the right portal vein. Methods: Eight healthy volunteers were studied on two occasions, separated by 1 week. Blood flow in the portal vein and superior mesenteric artery was measured repeatedly under basal fasting conditions. On one occasion measurements were also made after a meal. Every magnetic resonance measurement was followed by an echo-Doppler measurement in the right portal vein. Correlations between flow values were calculated using Pearson's r. Variability components were assessed using ANOVA. Results: Intra-individual variability was approximately 7% for portal vein flow measurements using magnetic resonance velocity mapping. This variability did not increase after 1 h, 1 week and after a meal. Values of flow measured in the portal vein and superior mesenteric artery using magnetic resonance velocity mapping correlated well ( r=0.80, p<0.001). Fasting portal flow as measured with magnetic resonance velocity mapping was 1.2 l/min (range 0.96-1.6 l/min). Variability in echo-Doppler measurements was comparable to the variability of magnetic resonance velocity mapping, and flow measurements obtained with the two techniques correlated well ( r=0.74; p<0.001). Conclusions: Magnetic resonance velocity mapping accurately measures blood flow in the portal vein with low variability and should be preferred when absolute flow values are necessary. Echo-Doppler measurement of the right portal vein has a low variability and can be used to study changes in flow.

Is infection and septic shock caused by a global oxygen deficiency? An overview in 2 parts. 1: Infection and correlation between DO2 and VO2

A global hypoxia resulting in an oxygen debt is assumed to be present in patients who suffer from the different stages and degrees of sepsis including septic shock and ARDS. As a consequence, the therapeutic concept of optimal values for cardiac output and oxygen delivery for these patients was proposed. This article reviews the literature with the objective of determining whether investigations dealing with oxygen delivery and consumption and with the plasma lactate concentration support the idea of the global hypoxia in septic patients. The finding of a pathologic oxygen supply dependency and an increase in plasma lactate concentration were taken as evidence for a global hypoxia. Between 1983 and 1991, oxygen supply dependency in septic patients was reported in an increasing number of publications. The increase in plasma lactate concentration was interpreted as lactic acidosis without presentation of plasma pH values and taken as evidence of global hypoxia and oxygen debt. From 1989 on, the number of publications that failed to show oxygen supply dependency even in the presence of an increased plasma lactate concentration increased. The problem in the method of determination of oxygen supply dependency became evident. Deducing both oxygen consumption and oxygen delivery from cardiac output from a common shared variable subject to measurement error may produce errors in the calculation of the regression between oxygen delivery and consumption. Oxygen supply dependency was not demonstrated in most investigations in which oxygen delivery and consumption were measured independently of each other. No decrease in mortality could be shown in prospective randomized studies for patients with sepsis and septic shock who were treated according to the concept of the optimal values. The lactate plasma concentration was below 5 mmol/l in most studies, which represents the borderline value for a clinically significant lactic acidosis. The term acidosis is not justified without a decrease in plasma pH or a decrease in the bicarbonate plasma concentration. An increased lactate plasma concentration can be merely the result of a hypermetabolism which is often found in septic patients. There is no proven evidence for global tissue hypoxia in septic patients from the investigations of oxygen delivery and consumption. This is also true for patients in septic shock after plasma volume expansion. The dogmatic proposal to increase cardiac output and oxygen delivery to certain levels cannot be sustained. However, regional hypoperfusion (e.g., of the splanchnic vascular bed) cannot be excluded. New approaches like gastric mucosal tonometry, measurement of splanchnic blood flow, and determination of regional metabolism are currently under investigation.

Estimation of splanchnic blood flow by the Fick principle in man and problems in the use of indocyanine green

Measurement of splanchnic blood flow is necessary to evaluate the effect of therapeutic interventions on splanchnic tissue perfusion. Systemic indocyanine green (ICG) clearance has been used to estimate splanchnic blood flow, but the results may be compromised by altered hepatic dye extraction. We evaluated the applicability of simultaneous estimation of splanchnic and femoral blood flow by dye dilution and regional blood sampling in intensive care patients. 240 simultaneous determinations of regional blood flow were conducted in different patient groups (cardiac surgery, ARDS, pancreatitis, septic shock, preoperative controls). The measurement protocol consists of catheterizations of hepatic vein, femoral artery and vein and primed constant infusion of two different ICG preparations. The method was used successfully in a wide variety of patients. Steady-state dye concentration and sufficient dye extraction was achieved in each group of patients. The coefficient of variation of splanchnic blood flow estimation was 7 +/- 1% and of femoral blood flow estimation 6 +/- 0%. There was a great intra- and interindividual variation of ICG extraction. Use of dobutamine modified the extraction in most patients but did not lessen the performance of the method. ICG extraction was markedly lower and the coefficient of variation of both femoral and splanchnic blood flow markedly higher with propylene glycol-dissolved ICG preparation as compared with the freeze-dried. The prerequisites for the method of primed, constant infusion of indocyanine green with hepatic vein catheterization are achieved in intensive care patients. The results of splanchnic blood flow estimations based on techniques with peripheral blood sampling should be interpreted with caution, and the use of ICG clearance as a flow-related indicator without the measurement of ICG extraction cannot be justified because of the great variability of dye extraction. Certain indocyanine green preparations may greatly modify the results of the regional blood flow determinations.

Use of para-amino hippuric acid to measure blood flows through portal-drained-viscera, liver and hindquarters in sheep

SUMMARYThe objectives of this study were (i) to evaluate a new surgical procedure to catheterize hepatic vessels as well as the posterior aorta and vena cava, (ii) to test a modification of a downstream dilution technique in order to measure blood flows through splanchnic tissues and hindquarters in rapid succession, and (iii) to improve the reliability of splanchnic blood flow measurements using paraamino hippuric acid (PAH). Ten adult ewes were used. The transhepatic surgical approach used proved successful; it was relatively easy to set up and a good recovery of hepatic functions was obtained. The attempt to measure splanchnic and hindquarters blood flow in rapid succession by alternating the sites of PAH infusion was unsuccessful, probably because of transient modifications in infusion rates due to different blood pressures in veins and arteries. Indeed, arterial PAH concentrations changed with infusion site. Finally, a better reproducibility of splanchnic blood flow measurements was obtained in sheep, fed every 3 h, by infusing the required amount of PAH partly via the mesenteric vein and partly via a ruminal vein.

Echo-Doppler measurement of splanchnic blood flow in control and cirrhotic subjects.

Blood flow in the splanchnic veins was studied in cirrhotics and matched controls by means of a system that combines a mechanical sector scanner with a pulsed Doppler. The measurements were validated in an in vitro model. Echo-doppler studies could be carried out reproducibly in only approximately two-thirds of cases because of poor echo transmission or incomplete cooperation. Portal blood velocity was significantly reduced in cirrhotics (10.5 +/- 0.6 cm/s versus 16.0 +/- 0.5 in controls; p less than 0.001), but portal blood flow was normal because of enlarged portal caliber. A complete hemodynamic evaluation of the splenic and superior mesenteric veins was possible in only a few subjects. In selected patients the technique may prove relevant in the study of hemodynamic effects of drugs and surgery on portal blood flow.