Jens Otto Clemmesen

Splanchnic and leg exchange of amino acids and ammonia in acute liver failure

BACKGROUND & AIMS In patients with acute liver failure, hyperammonemia is associated with cerebral herniation. We examined the splanchnic and leg exchange of amino acids, urea, and ammonia in such patients. METHODS Bedside liver vein catheterization was used in 22 patients after development of hepatic encephalopathy grades III-IV. Femoral venous blood was sampled in 7 of these patients. RESULTS Arterial amino acid concentration (8.1 +/- 4.1 mmol/L) was increased 4-fold above normal. Glutamine (2.4 +/- 1.8 mmol/L) and alanine (0.57 +/- 0.35 mmol/L) were by far the predominant amino acids exchanged in the splanchnic and leg circulation. In the splanchnic circulation, there was a net uptake of glutamine (241 +/- 353 micromol/min) and ammonia and alanine were released in an almost 1:1 stoichiometry (r(2) = 0.47; P < 0.001). In the leg, ammonia and alanine were removed and glutamine released. The leg ammonia concentration difference was correlated to that of glutamine (r(2) = 0.80; P = 0.008) and alanine (r(2) = 0.67; P = 0.03). CONCLUSIONS Splanchnic metabolism of glutamine in combination with decreased hepatic function was responsible for the splanchnic release of ammonia and alanine. These processes were reversed in skeletal muscle. Stimulation of skeletal muscle metabolism of ammonia could be a important target for future treatment of patients with acute liver failure.

Mesenteric, coeliac and splanchnic blood flow in humans during exercise

1 Exercise reduces splanchnic blood flow, but the mesenteric contribution to this response is uncertain. 2 In nineteen humans, superior mesenteric and coeliac artery flows were determined by duplex ultrasonography during fasting and postprandial submaximal cycling and compared with the splanchnic blood flow as assessed by the Indocyanine Green dye‐elimination technique. 3 Cycling increased arterial pressure, heart rate and cardiac output, while it reduced total vascular resistance. These responses were not altered in the postprandial state. During fasting, cycling increased mesenteric, coeliac and splanchnic resistances by 76, 165 and 126%, respectively, and it reduced corresponding blood flows by 32, 50 and 43% (by 0.18 ± 0.04, 0.42 ± 0.03 and 0.60 ± 0.04 l min−1). Postprandially, mesenteric and splanchnic vascular resistances decreased, thereby elevating regional blood flow, while the coeliac circulation was not influenced. Postprandial cycling did not influence the mesenteric resistance significantly, but its blood flow decreased by 22% (0.46 ± 0.28 l min−1). Coeliac and splanchnic resistance increased by 150 and 63%, respectively, and the corresponding regional blood flow decreased by 51 and 31% (0.49 ± 0.07 and 0.96 ± 0.28 l min−1). Splanchnic blood flow values assessed by duplex ultrasound and by dye‐elimination techniques were correlated (r= 0.70; P < 0.01). 4 During submaximal exercise in humans, splanchnic resistance increases and blood flow is reduced following a 50% reduction in the hepato‐splenic and a 25% reduction in the mesenteric blood flow.

High-volume plasma exchange in patients with acute liver failure: An open randomised controlled trial.

BACKGROUND & AIMS Acute liver failure (ALF) often results in cardiovascular instability, renal failure, brain oedema and death either due to irreversible shock, cerebral herniation or development of multiple organ failure. High-volume plasma exchange (HVP), defined as exchange of 8-12 or 15% of ideal body weight with fresh frozen plasma in case series improves systemic, cerebral and splanchnic parameters. METHODS In this prospective, randomised, controlled, multicentre trial we randomly assigned 182 patients with ALF to receive either standard medical therapy (SMT; 90 patients) or SMT plus HVP for three days (92 patients). The baseline characteristics of the groups were similar. The primary endpoint was liver transplantation-free survival during hospital stay. Secondary-endpoints included survival after liver transplantation with or without HVP with intention-to-treat analysis. A proof-of-principle study evaluating the effect of HVP on the immune cell function was also undertaken. RESULTS For the entire patient population, overall hospital survival was 58.7% for patients treated with HVP vs. 47.8% for the control group (hazard ratio (HR), with stratification for liver transplantation: 0.56; 95% confidence interval (CI), 0.36-0.86; p=0.0083). HVP prior to transplantation did not improve survival compared with patients who received SMT alone (CI 0.37 to 3.98; p=0.75). The incidence of severe adverse events was similar in the two groups. Systemic inflammatory response syndrome (SIRS) and sequential organ failure assessment (SOFA) scores fell in the treated group compared to control group, over the study period (p<0.001). CONCLUSIONS Treatment with HVP improves outcome in patients with ALF by increasing liver transplant-free survival. This is attributable to attenuation of innate immune activation and amelioration of multi-organ dysfunction.

Effects of high-volume plasmapheresis on ammonia, urea, and amino acids in patients with acute liver failure.

OBJECTIVE:In acute liver failure (ALF), urea production is severely impaired, and detoxification of ammonia by glutamine synthesis plays an important protective role. The aim of this study was to examine the effects of therapeutic high-volume plasmapheresis (HVP) on arterial concentrations and splanchnic exchange rates of ammonia, urea, and amino acids—in particular, glutamine.METHODS:A quantity of 8 L of plasma was exchanged over the course of 7 h in 11 patients with ALF after development of hepatic encephalopathy grade III–IV. Splanchnic exchange rates of ammonia, urea, and amino acids were measured by use of liver vein catheterization.RESULTS:HVP removed ammonia and glutamine at a rate of 1 μmol/min and 27 μmol/min, respectively. Arterial ammonia decreased from 160 ± 65 to 114 ± 50 μmol/L (p < 0.001). In contrast, arterial glutamine was only minimally changed from 1791 ± 1655 to 1764 ± 1875 μmol/L (NS). This implied that the rate of systemic glutamine synthesis was increased by 27 μmol/min. Splanchnic exchange rates (before vs after HVP) were as follows: for ammonia, −93 ± 101 versus− 70 ± 80 μmol/min (NS); urea-nitrogen, 0.08 ± 1.64 versus− 0.31 ± 0.45 mmol/min (NS); alanine, −73 ± 151 versus 12 ± 83 μmol/min (p < 0.05); and glutamine: 132 ± 246 versus 186 ± 285 μmol/min (NS), with negative values denoting release.Conclusions:Arterial ammonia decreased during HVP in patients with ALF. The data suggest that this effect of HVP could be explained by increased hepatic urea synthesis and possibly by increased glutamine synthesis in muscle tissue.

Cerebral blood flow, oxygen metabolism and transcranial Doppler sonography during high-volume plasmapheresis in fulminant hepatic failure.

Objective: The effect of high-volume plasmapheresis on hepatic encephalopathy, cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) was investigated in patients with fulminant hepatic failure (FHF). Methods: Twelve consecutive patients (8 women, 4 men, median age 34 years (range 19–51)) were studied before and after high-volume plasmapheresis with 10–16 litres fresh frozen plasma, while PaCO2 and body temperature were maintained at 30 (23–34) mmHg and 37.6°C (36.6–38.4), respectively. Blood samples from the internal jugular vein and a radial artery allowed calculation of the cerebral arteriovenous oxygen difference (AVDO2) and oxygen extraction (AVDO2 divided by arterial oxygen content). CBF was determined by a xenon-133 clearance method in eight patients and CMRO2 calculated as AVDO2 times CBF. Cerebral perfusion pressure (CPP) was determined as the difference between mean arterial and subdural pressures in eight patients. Results: High-volume plasmapheresis was initiated 22 (6–168) h after the development of hepatic encephalopathy and 11 patients had grade 4 encephalopathy. Following high-volume plasmapheresis the grade of encephalopathy improved in four patients. The CBF increased from a median of 31 (16–86) to 45 (18–97) ml/100 g/min and as oxygen extraction remained unchanged (32 (9–41) vs. 29 (7–39)%), CMRO2 increased from 1.24 (0.96–1.82) to 1.86 (1.00–2.07) ml/100 g/min (P<0.05). The CPP increased from 62 (19–76) to 92 (50–105) mmHg (P<0.01), whereas the intracranial pressure remained unchanged (19 (3–45) vs. 11 (5–33) mmHg). No statistical difference was found between the relative changes in the above parameters in survivors compared to non-survivors. Conclusion: Although the clinical status did not improve in all patients, both CBF and CMRO2 increased after high-volume plasmapheresis. The alleviation of brain oxygen metabolism by high-volume plasmapheresis may reflect partial removal of neuroinhibitory plasma factors.

Splanchnic metabolism of fuel substrates in acute liver failure

BACKGROUND/AIMS This study aimed to characterize the exchange of fuel substrates in the splanchnic circulation in acute liver failure. METHODS Liver vein catheterization was used in 22 patients with acute liver failure after development of hepatic encephalopathy grade III-IV Healthy controls, patients with cirrhosis and patients with acute on chronic liver disease were also studied. RESULTS In acute liver failure there was splanchnic removal of glucose (0.21+/-0.44 mmol/min), release of lactate (0.34+/-0.37 mmol/min), pyruvate (0.08+/-0.06 mmol/min) and ketone bodies (0.04+/-0.02 mmol/min), while extraction of amino acids and free fatty acids was insignificant. In the acute liver failure group, a normal hepatic venous oxygen saturation (0.69+/-0.12) and normal pyruvate/lactate ratio suggested absence of hypoxia even though the acetoacetate/beta-hydroxybutyrate ratio was decreased. Only in the acute liver failure group did the measured splanchnic oxygen content difference exceed what could be accounted for even by hypothesizing complete oxidation of all extracted blood-borne fuel substrates; oxidation of endogenous substrates may be quantitatively important in this condition. CONCLUSION Acute liver failure was associated with a state of accelerated glycolysis in the splanchnic region, leading to release of lactate in the absence of splanchnic hypoxia.

Haemodynamic changes after high-volume plasmapheresis in patients with chronic and acute liver failure

Objective: To evaluate the haemodynamic changes during treatment with highvolume plasmapheresis in patients with chronic liver failure compared to patients with acute liver failure. Methods: Haemodynamic measurements were performed with a Swan‐Ganz catheter and thermodilution technique. High‐volume plasmapheresis (mean plasma exchange of 8.6 litres) was performed in 11 patients with chronic and 16 patients with acute liver failure. Results: In patients with chronic liver failure, systemic vascular resistance index was unaltered: 1193 ± 494 dynscm‐5m2 before treatment versus 1180±399 dynscm‐5m2 after. Mean arterial pressure increased from 69±11 mmHg to 78±13 mmHg (P<0.05) and cardiac output increased from 8.1 ±2.4l/min to 8.9±2.4 l/min (P<0.05) during highvolume plasmapheresis. In patients with acute liver failure, systemic vascular resistance index increased from 1154±628 dyns cm‐5m2 to 1614±738dynscm‐5m2 (P<0.001). In this group mean arterial pressure increased from 78±16mmHg to 95±10mmHg (P< 0.001) and cardiac output decreased from 9.6±3.7l/min to 8.2±2.9 l/min (P<0.01). Conclusion: The hyperkinetic circulation in chronic and acute patients was differently affected by high‐volume plasmapheresis. We suggest that in chronic liver failure both portosystemic shunting and chronic peripheral vasodilation may contribute to the hyperkinetic syndrome, whereas in acute liver failure a humoral factor which can be removed by high‐volume plasmapheresis is a main contributor.

Glucagon-to-insulin ratio is pivotal for splanchnic regulation of FGF-21 in humans.

Background & aims Fibroblast growth factor 21 (FGF-21) is a liver-derived metabolic regulator induced by energy deprivation. However, its regulation in humans is incompletely understood. We addressed the origin and regulation of FGF-21 secretion in humans. Methods By determination of arterial-to-venous differences over the liver and the leg during exercise, we evaluated the organ-specific secretion of FGF-21 in humans. By four different infusion models manipulating circulating glucagon and insulin, we addressed the interaction of these hormones on FGF-21 secretion in humans. Results We demonstrate that the splanchnic circulation secretes FGF-21 at rest and that it is rapidly enhanced during exercise. In contrast, the leg does not contribute to the systemic levels of FGF-21. To unravel the mechanisms underlying the regulation of exercise-induced hepatic release of FGF-21, we manipulated circulating glucagon and insulin. These studies demonstrated that in humans glucagon stimulates splanchnic FGF-21 secretion whereas insulin has an inhibitory effect. Conclusions Collectively, our data reveal that 1) in humans, the splanchnic bed contributes to the systemic FGF-21 levels during rest and exercise; 2) under normo-physiological conditions FGF-21 is not released from the leg; 3) a dynamic interaction of glucagon-to-insulin ratio regulates FGF-21 secretion in humans.

Circulating Follistatin Is Liver-Derived and Regulated by the Glucagon-to-Insulin Ratio

CONTEXT Follistatin is a plasma protein recently reported to increase under conditions with negative energy balance, such as exercise and fasting in humans. Currently, the perception is that circulating follistatin is a result of para/autocrine actions from various tissues. The large and acute increase in circulating follistatin in response to exercise suggests that it may function as an endocrine signal. OBJECTIVE We assessed origin and regulation of circulating follistatin in humans. DESIGN/INTERVENTIONS First, we assessed arterial-to-venous difference of follistatin over the splanchnic bed at rest and during exercise in healthy humans. To evaluate the regulation of plasma follistatin we manipulated glucagon-to-insulin ratio in humans at rest as well as in cultured hepatocytes. Finally, the impact of follistatin on human islets of Langerhans was assessed. RESULTS We demonstrate that in humans the liver is a major contributor to circulating follistatin both at rest and during exercise. Glucagon increases and insulin inhibits follistatin secretion both in vivo and in vitro, mediated via the secondary messenger cAMP in the hepatocyte. Short-term follistatin treatment reduced glucagon secretion from islets of Langerhans, whereas long-term follistatin treatment prevented apoptosis and induced proliferation of rat β cells. CONCLUSIONS In conclusion, in humans, the liver secretes follistatin at rest and during exercise, and the glucagon-to-insulin ratio is a key determinant of circulating follistatin levels. Circulating follistatin may be a marker of the glucagon-to-insulin tone on the liver.

The Effect of Increasing Blood Pressure with Dopamine on Systemic, Splanchnic, and Lower Extremity Hemodynamics in Patients with Acute Liver Failure

BACKGROUND Arterial hypotension occurs frequently in patients with acute liver failure (ALF). Treatment with epinephrine and norepinephrine in patients with ALF has been associated with a decrease in whole-body (systemic) oxygen consumption. We aimed to investigate the effect of increasing blood pressure with dopamine on whole-body (systemic), splanchnic, and lower extremity hemodynamics and oxygen consumption in patients with acute liver failure and hepatic encephalopathy grade III or IV. METHODS In seven patients with ALF cardiac output (CO) was measured with the thermodilution technique, and hepatic blood flow (HBF) was estimated with infusion of sorbitol as test compound, liver vein catheterization, and calculations on the basis of Ficks principle. Lower-extremity blood flow was measured with strain-gauge plethysmography. RESULTS During infusion of dopamine (5 +/- 2 microg kg(-1) min(-1)) mean arterial pressure (MAP) increased from 68 +/- 5 to 85 +/- 8 mmHg. CO increased from 6.8 +/- 0.8 to 9.0 +/- 2.4 l/min (P < 0.05), systemic oxygen delivery from 45 +/- 7 to 63 +/- 19 mmol/min (P < 0.05), systemic oxygen consumption from 10.2 +/- 2.0 to 11.5 +/- 3.3 mmol/min (NS). HBF increased from 2.2 +/- 0.7 to 2.7 +/- 1.0 l/ min (P < 0.05), splanchnic oxygen delivery from 14.4 +/- 5.3 to 18.5 +/- 7.2 mmol/min (P < 0.01), and splanchnic oxygen consumption decreased from 3.9 +/- 1.1 to 2.9 +/- 0.6 mmol/min (P < 0.05). No significant changes in lower extremity flow and oxygenation variables were found. CONCLUSIONS The use of dopamine in patients with ALF to increase MAP was associated with increases in systemic and splanchnic oxygen delivery. A concomitant decrease in splanchnic oxygen consumption was observed.