Effects of the stable prostacyclin analogue iloprost on mesenteric blood flow in porcine endotoxic shock

The I-MICRO trial, Ilomedin for treatment of septic shock with persistent microperfusion defects: a double-blind, randomized controlled trial-study protocol for a randomized controlled trial

BACKGROUND

Septic shock remains a significant cause of death in critically ill patients. During septic shock, some patients will retain microcirculatory disorders despite optimal hemodynamic support (i.e., fluid resuscitation, vasopressors, inotropes). Alterations in the microcirculation are a key pathophysiological factor of organ dysfunction and death in septic shock patients. Ilomedin is a prostacyclin analog with vasodilatory effect and anti-thrombotic properties (i.e., inhibition of platelet aggregation) preferentially at the microcirculatory level. We hypothesize that early utilization of intravenous Ilomedin in septic shock patients with clinical persistence of microperfusion disorders would improve the recovery of organ dysfunction.

METHODS

The I-MICRO trial is a multicenter, prospective, randomized, double-blinded, placebo-controlled study. We plan to recruit 236 adult patients with septic shock and persistent microcirculatory disorders (i.e., skin mottling or increased capillary refill time) despite hemodynamic support. Participants will be randomized to receive a 48-h intravenous infusion of either Ilomedin or placebo starting at the earliest 6 h and later 24 h after septic shock. The primary outcome will be the change (delta) of sequential organ failure assessment (SOFA) score between randomization and day 7. Secondary outcomes will include mean SOFA score during the first 7 days after randomization, mortality at day 28 post-randomization, number of ventilation-free survival days in the 28 days post-randomization, number of renal replacement therapy-free survival days in the 28 days post-randomization, number of vasopressor-free survival days in the 28 days post-randomization, and mottling score at day 1 after randomization.

DISCUSSION

The trial aims to provide evidence on the efficacy and safety of Ilomedin in patients with septic shock and persistent microcirculatory disorders.

TRIAL REGISTRATION

NCT NCT03788837 . Registered on 28 December 2018.

Epoprostenol improves mucosal tissue oxygen tension in an acute endotoxemic pig model

The objective of the present study was to determine the effects of increasing dosages of continuously infused epoprostenol (PGI), a prostacyclin analog, on intestinal oxygen supply and jejunal mucosal tissue oxygen tension in an acute endotoxic pig model. Jejunal mucosal tissue PO2, oxygen saturation of jejunal microvascular hemoglobin, and gut microvascular blood flow were investigated. Systemic hemodynamic variables, mesenteric-venous and systemic acid base and blood gas variables, and lactate measurements were recorded. Measurements were performed at baseline, after Escherichia coli LPS administration, and at 20-min intervals during incremental PGI infusion (n = 8; 25, 50, 100, and 200microg x kg x h, respectively); or infusion of an equal amount of isotonic sodium chloride solution (n = 7). LPS infusion led to a significant decrease in mucosal tissue oxygen tension and microvascular hemoglobin oxygen saturation. Epoprostenol infusion led to a significant, dose-dependent increase in cardiac index and systemic oxygen delivery. Mucosal tissue oxygen tension and microvascular hemoglobin oxygen saturation increased after PGI administration and even returned to more-than-baseline values. Continuously infused PGI increased intestinal hemoglobin oxygen saturation and mucosal tissue oxygen tension in a dose-dependent manner mainly due to an increase in villus blood flow in this acute endotoxic pig model.

The effects of activated protein C and prostacyclin on arterial oxygenation and protein leakage in the lung and the gut under endotoxaemia in the rat

BACKGROUND

Based on the anti-adhesive/anti-aggregatory and permeability-reducing properties of activated protein C (APC) and prostacyclin (PGI(2)), we analysed and compared these substances regarding their efficacy in counteracting transcapillary leakage of albumin in the lung and the gut, and in improving arterial oxygenation under a condition of inflammation.

METHODS

The randomized and blinded study was performed on 31 adult male Sprague-Dawley rats. Inflammation was induced by continuous infusion of Escherichia coli endotoxin (lipopolysaccharide, LPS). Six hours after the start of the LPS infusion (240,000 U/kg/h), a simultaneous infusion of saline (control group) or 8 microg/kg/min of human recombinant APC or 2 ng/kg/min of PGI(2) was started and continued for 24 h (n=8 per group). The study also included a sham group. Transcapillary leakage of albumin was measured from the ratio between tissue radioactivity [counts per minute (cpm)/g tissue] and actual amount of radioactivity given (cpm/g body weight of (125)I-albumin). Oxygenation was assessed from arterial and central venous blood samples.

RESULTS

LPS induced albumin leakage in the gut and the lung, and impaired blood oxygenation. In the lung, the leakage was lower in the PGI(2) group than in the APC and the control groups (P<0.05). In the gut, it was lower in the APC and the PGI(2) groups than in the control group (P<0.05). Oxygenation was better in the APC and PGI(2) groups than in the control group.

CONCLUSION

Our data suggest that both APC and low-dose PGI(2) are beneficial in LPS-induced inflammation in the rat, by reducing albumin leakage and improving blood oxygenation.

Prostacyclin in sepsis: A systematic review

According to current literature, infective processes greatly modify both vascular hemodynamics and anti-oxidant properties of affected tissues, causing a change in homeostasis that regulates the correct functioning of all cells responsible for the physiological and metabolic balance of various organs. As a consequence, the response to the infection that has caused the change is also likely to be weaker and, in the case of septic shock, ineffective. In this review, we will take into consideration these mechanisms and then focus on a group of vasodilator drugs (prostacyclin and its analogs) which, though have been used for over 20 years mainly to treat obstructive vascular diseases, have such hemodynamic and anti-inflammatory properties which prevent homeostatic changes. It is obvious that prostacyclin does not definitively have anti-infective characteristics; however, in association with anti-infective drugs (antibiotics, etc.), the effectiveness of the latter appears improved, at least in some circumstances. Similarly, the fact that prostacyclin and its analogs have a cytoprotective effect on the liver and reduce the ischemia-reperfusion damage following liver transplant is not a novelty and evidence that they improve hepatic hemodynamics suggests their use in those pathologies characterized by possible reduced perfusion or ascertained ischemia of the liver.

Negative mesenteric effects of lung recruitment maneuvers in oleic acid lung injury are transient and short lasting

OBJECTIVE

To test the hypothesis that repeated recruitment maneuvers (RMs) have sustained negative effects on mesenteric circulation, metabolism, and oxygenation 60 mins after RMs in pigs with oleic acid lung injury. Further, we aimed to test the hypothesis that an infusion of prostacyclin (PC) at 33 ng.kg.min would attenuate such possible negative mesenteric effects.

DESIGN

Randomized, experimental, controlled study.

SETTING

University hospital animal laboratory.

SUBJECTS

A total of 31 anesthetized, fluid-resuscitated pigs with oleic acid lung injury.

INTERVENTIONS

: Animals were randomized to one of the following four groups: a control group (n = 7) that received no intervention, recruitment group (n = 8) that underwent the RM sequence, a prostacyclin group (n = 8) that received an infusion of PC, and a recruitment-prostacyclin group (n = 8) that received an infusion of PC and concomitant RM sequence.

MEASUREMENTS AND MAIN RESULTS

We measured systemic and mesenteric hemodynamic variables, jejunal mucosal perfusion, mesenteric lactate flux, jejunal tissue oxygen tension, and mesenteric oxygen delivery, uptake, and extraction ratio. Five minutes after RMs, mesenteric oxygen extraction ratio and mesenteric lactate flux were more prominently increased in the recruitment group, giving evidence of worsened mesenteric conditions after RMs. These signs of worsened conditions were further supported by more decreased jejunal tissue oxygen tension and portal vein oxygen saturation in the recruitment group. PC preserved mesenteric oxygenation, as indicated by less of a decrease in portal vein oxygen saturation at the time corresponding to 5 mins after RM and less of a decrease in mesenteric oxygen delivery at the time corresponding to 15 mins after RM. PC preserved mesenteric oxygenation as indicated by less of a decrease in portal vein oxygen saturation at 5 mins after RM and an attenuated increase in mesenteric oxygen extraction ratio at 5 mins after RM. There was a trend toward worsened jejunal mucosal perfusion, although not significant.

CONCLUSIONS

In an oleic acid lung injury model, three repeated RMs did not improve systemic oxygenation or lung mechanics. Negative effects on mesenteric oxygenation and metabolism were transient and short lasting. The intestinal effects of PC during RMs were minor and opposing, showing preserved oxygenation but a trend toward worsened mucosal perfusion.

Splanchnic Hypoperfusion-Directed Therapies in Trauma: A Prospective, Randomized Trial

Splanchnic hypoperfusion as reflected by gastric intramucosal acidosis has been recognized as an important determinant of outcome in shock. A comprehensive splanchnic hypoperfusion-ischemia reperfusion (IRP) protocol was evaluated against conventional shock management protocols in critical trauma patients. The study was a prospective randomized trial comparing three therapeutic approaches to hypoperfusion after severe trauma in 151 trauma patients admitted to the intensive care unit. Group 1 patients received hemodynamic support based on conventional indicators of hypoperfusion. In group 2, resuscitation was further guided by gastric tonometry-derived estimates of splanchnic hypoperfusion and included more invasive hemodynamic monitoring and additional administration of colloid or crystalloid solutions, or inotropic support. Group 3 patients additionally received therapies specifically aimed at optimizing splanchnic perfusion and minimizing oxidant-mediated damage from reperfusion. The three groups were similar based on age, Injury Severity Score, and Acute Physiology and Chronic Health Evaluation II Scores. There were no statistically significant differences in mortality rates, organ dysfunction, ventilator days, or length of stay between any of the interventions. Techniques of optimization of splanchnic perfusion and minimization of oxidant-mediated reperfusion injury evaluated in this study were not advantageous relative to standard resuscitation measures guided by conventional or tonometric measures of hypoperfusion in the therapy of occult and clinical shock in trauma patients.

Opposite effects of prostacyclin on hepatic blood flow and oxygen consumption after burn and sepsis

BACKGROUND

Burn and sepsis are associated with hepatic ischemia and reperfusion injury. This study examines the hypothesis that postburn treatment with the vasodilator prostacyclin would be beneficial for hepatic perfusion and oxygenation.

METHODS

Female pigs (n = 18, 20-25 kg) underwent laparotomy, during which ultrasonic flow probes were placed on the portal vein and the common hepatic artery. Catheters were inserted in the superior mesenteric and left hepatic veins. After 5 days, all animals were anesthetized and 12 of them received 40% total body surface area third-degree burn; 100 microg/kg Escherichia coli lipopolysaccharide (LPS) was intravenously administered 18 hours postburn. Burned animals were randomized to receive a constant infusion of iloprost (20 ng/kg per minute) or an equivalent amount of carrier solution (normal saline). All animals were studied for 42 hours.

RESULTS

Burn caused a 2.5-fold increase in hepatic arterial vascular resistance (HAVR) and a 39% decrease in hepatic arterial blood flow (HABF). Postburn administration of iloprost did not improve the hepatic arterial hemodynamics (1.8-fold increase in HAVR and 38% decrease in HABF). Post-LPS, HABF was significantly reduced to 22% of baseline and HAVR was 15-fold increased (P < 0.05 vs. baseline, ANOVA). In contrast, iloprost-treated animals did not show hepatic arterial vasoconstriction, as both HABF and HAVR remained baseline values during the endotoxic phase (P < 0.05 vs. nontreated group, ANOVA). Postburn iloprost treatment yielded a significant improvement in post-LPS portal venous blood flow (PVBF, 79% of baseline vs. 45% of baseline in nontreated animals, P < 0.05, ANOVA). Portal venous pressure showed 16% and 56% increases after burn and endotoxin, respectively. Portal hypertension did not occur in iloprost-treated animals, as portal venous pressure remained within baseline range (P < 0.05 vs. nontreated group, ANOVA). Burn and endotoxemia resulted in a significant decrease of hepatic oxygen delivery (hDO2, 63% and 12% of baseline, respectively) and hepatic oxygen consumption (hVO2, 61% and 21% of baseline, respectively). Only during the postburn endotoxic phase, iloprost improved hDO2 and hVO2 (140% and 79%, respectively; P < 0.05 vs. nontreated group, ANOVA).

CONCLUSIONS

Postburn prostacyclin treatment appears to have no beneficial effects on hepatic perfusion early postburn. However, during the late postburn endotoxic phase, prostacyclin seems to significantly improve hepatic total blood flow and oxygenation. In addition, prostacyclin treatment attenuated burn- and endotoxin-induced portal hypertension.

Beneficial effect of iloprost on the course of acute taurocholate pancreatitis in rats and its limitation by antecedent acute ethanol intake

The effects of stable prostacyclin analogue iloprost on the trypsinogen activation, labilization of lysosomal membranes, lipolytic enzymes activities, histopathological and ultrastructural changes in the pancreas of rats with severe, taurocholate acute pancreatitis (AP), preceded for 6 h by acute ethanol intake have been investigated. Iloprost (1 microg/kg b.w., i.p.) was applied every 6 hours after inducing of taurocholate AP. The antecedent intragastric 40% ethanol intake (5 g/kg b.w.) increased an index of trypsinogen activation in AP lasting 18 h. Treatment with iloprost prevented this increase in the rats with AP given earlier alcohol, and limited the labilization of lysosomal membranes in nonalcoholized rats with AP. Phospholipase A2 and lipase activities were reduced by iloprost only in the rats not given ethanol. The additional damaging effect of acute ethanol abuse prior to AP could be dependent on augmented activation of trypsinogen. The protective effect of iloprost in AP seems to be dependent on the attenuation of trypsinogen activation, decrease of total potential trypsin and the decrease of lysosomal membranes labilization. Its protective effect could be limited in taurocholate acute pancreatitis preceded by acute ethanol intake as evidenced by the differences in the cathepsin B, phospholipase A2 and lipase activities and by histopathological and ultrastructural examination.

Effect of estradiol administration on splanchnic perfusion after trauma-hemorrhage and sepsis

PURPOSE OF REVIEW

This review focuses on the latest mechanistic understanding of the effects of estradiol on the splanchnic circulation and the possibility of estradiol treatment as an adjunct for the treatment of trauma-hemorrhage and sepsis.

RECENT FINDINGS

Systemic hypotension induced by shock accompanies marked alterations in blood flow to various organs. Decreased splanchnic perfusion is frequently observed after insults, such as severe hemorrhage or sepsis, which leads to the destruction of the intestinal mucosal barrier and hepatic dysfunction. Studies suggest that estradiol acts as a facilitator of the intestinal blood flow via the increased production of nitric oxide, decreased production of vasoconstrictors, attenuated neutrophil adhesion, and decreased formation of oxygen free radicals.

SUMMARY

Trauma-hemorrhage results in decreased circulating blood volume. In contrast, sepsis is an inflammatory state mainly mediated by bacterial products. However, these divergent insults show similar pathophysiologic alterations in terms of the splanchnic circulation. Because estradiol effectively protects the organs from circulatory failure after various adverse circulatory conditions, many studies are being performed to clarify the molecular mechanism of estradiol action with regard to tissue circulation. Estradiol improves the macro- and microcirculation of the splanchnic organs by multiple mechanisms. Nonetheless, it remains unclear which mechanism plays the most important role in the treatment of trauma-hemorrhage and sepsis. Additional studies are required to elucidate the precise mechanism of estradiol action and to determine the usefulness of estradiol treatment for severe hemorrhage and sepsis in patients.

Hemodynamic effects of a prostacyclin analog (iloprost) on portal flow velocity and volume and visceral artery circulation in patients with lower limb arteriopathy

Previous studies demonstrated that iloprost improves the peripheral circulation. In this study, we examined, by Doppler sonography, portal flow velocity (cm/s) and volume (mL/min), and resistance index (RI) of visceral arteries in 23 patients before and after 7 days of iloprost infusion. Statistically significant hemodynamic changes were only seen in portal vein (pre-iloprost vs. post-iloprost treatment mean portal flow velocity and volume values: 23.9 cm/s vs. 29.0 cm/s, p < 0.001 and 1824.6 mL/min vs. 2294.4 mL/min, p < 0.001, respectively). On the other hand, the interlobar renal artery RI, reduced after iloprost treatment in most patients, was not statistically significant; conflicting results were obtained on the hepatic and mesenteric arteries. Our results indicate that iloprost significantly increases portal flow velocity and volume. The understanding of the mechanism through which iloprost plays a role in portal microcirculation could be useful for its new medical indications in liver hemodynamic disorders.

Intravenous iloprost increases mesenteric blood flow in experimental acute nonocclusive mesenteric ischemia

OBJECTIVE

To evaluate the effect of an intravenously administered synthetic epoprostenol analog, iloprost, in nonocclusive acute mesenteric ischemia induced by cardiac tamponade.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

Animal research laboratory at a university medical center.

SUBJECTS

Ten Yorkshire pigs (weight range, 20-25 kg).

INTERVENTIONS

Nonocclusive acute mesenteric ischemia was induced by pericardial tamponade. Pigs were randomized to receive either a low-dose, continuous intravenous infusion of iloprost (0.075 microg/kg/min) or an equivalent volume of normal saline to serve as the control. Infusion of iloprost or saline was continued after pericardial tamponade was reversed.

METHODS

Ten anesthetized and ventilated pigs underwent laparotomy and thoracotomy. A pulmonary artery catheter was inserted, a magnetic flow probe was positioned around the superior mesenteric artery (SMA), and cannulation of the pericardial space was performed. Pericardial tamponade was induced by injecting 5% dextrose in water into the pericardial space until blood flow in the superior mesenteric artery decreased to half of baseline. After 60 mins, animals received either a continuous intravenous infusion of iloprost at 0.075 microg/kg/min (n = 6) or an equal volume of normal saline (n = 4) for 60 mins. Pericardial fluid was then removed, and iloprost or normal saline infusion was continued for another 60 mins.

MEASUREMENTS

Heart rate, blood pressure, cardiac output, oxygen delivery, oxygen consumption, SMA blood flow, ileal Pco2, ileal intramucosal pH, and serum lactate levels of mixed venous blood and mesenteric venous blood were recorded at baseline, after pericardial tamponade was induced, during the iloprost or normal saline infusion with pericardial tamponade, and after removal of pericardial fluid (reperfusion period).

RESULTS

Iloprost infusion increased SMA blood flow by 60% in this model of nonocclusive mesenteric ischemia (from 168 +/- 41 to 269 +/- 76 mL/min; p <.05). The effect of iloprost infusion was more prominent after the tamponade (422 +/- 87 mL/min in the iloprost group vs. 232 +/- 111 mL/min in the control group; p <.05). Increased mesenteric perfusion decreased intestinal mucosal hypercarbia, leading to improvement of intramucosal pH.

Effects of iloprost, a stable prostacyclin analog, on intestinal leukocyte adherence and microvascular blood flow in rat experimental endotoxemia

OBJECTIVE

To investigate the effects of iloprost, a stable prostacyclin analog, on leukocyte adherence in intestinal venules and intestinal microvascular blood flow in experimental endotoxemia.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Experimental laboratory.

SUBJECTS

Twenty-one male Wistar rats weighing 190 +/- 40 g.

INTERVENTIONS

The rats were divided equally into three groups: the first was a control group; the second received endotoxin (20 mg/kg lipopolysaccharide from Escherichia coli O55:B5 intravenously); and the third received endotoxin and intravenous iloprost infusion (2 ng.kg-1.min-1).

MEASUREMENTS AND MAIN RESULTS

The distal small intestine of the animals was examined by using intravital fluorescence videomicroscopy 2 hrs after endotoxin challenge. Leukocytes were stained in vivo by means of rhodamine 6G. Intestinal microvascular blood flow was measured by laser Doppler flowmetry in the terminal ileum. Iloprost treatment significantly attenuated the count of adherent leukocytes in collecting venules (control, 61 +/- 10 n/mm2; lipopolysaccharide, 364 +/- 60 n/mm2; iloprost, 232 +/- 29 n/mm2; p <.05) and in postcapillary venules (control, 96 +/- 14 n/mm2; lipopolysaccharide, 470 +/- 21 n/mm2; iloprost 390 +/- 41 n/mm2; p <.05). Intestinal microvascular blood flow was decreased significantly in the lipopolysaccharide group (-49%), whereas iloprost-treated animals showed no significant difference compared with the control group.

CONCLUSIONS

The study demonstrated that administration of iloprost attenuated leukocyte adherence in postcapillary and collecting intestinal venules and improved intestinal microvascular blood flow. Thus, iloprost treatment may impact endotoxin-induced intestinal injury.

Beneficial effects of low-dose prostacyclin on cat intestinal perfusion during endotoxemia as evaluated with microdialysis and oxygen transport variables

OBJECTIVE

To evaluate the effects of low-dose prostacyclin on intestinal perfusion during endotoxemia.

DESIGN

A randomized, blinded experimental study.

SETTING

A university laboratory.

SUBJECTS

Sixteen anesthetized cats.

INTERVENTIONS

The animals received endotoxin by continuous intravenous infusion (0.5 mg/kg plus 0.5 mg x kg(-1) x hr(-1)) and a continuous volume replacement throughout the experiment. Four hours after the start of endotoxin, the animals were randomized to receive an infusion of either prostacyclin at a dose of 1 ng x kg(-1) x min(-1) (prostacyclin group) or vehicle (control group) during the next 4 hrs.

MEASUREMENTS AND MAIN RESULTS

Intestinal vascular resistance was calculated from systemic arterial pressure, central venous pressure, and superior mesenteric artery blood flow, and intestinal oxygen delivery and uptake were calculated from superior mesenteric artery and vein blood samples and blood flow. Interstitial lactate, pyruvate, glucose, and glycerol in the ileal wall were measured by using microdialysis. There were no differences in baseline values between the groups. Systemic blood pressure decreased initially but recovered and remained stable in both groups. In the control group, intestinal vascular resistance increased from 10.9 +/- 1.0 to 24.7 +/- 5.3 mm Hg x mL x min(-1) x kg(-1) (p <.05) at 8 hrs, and oxygen delivery decreased from 2.6 +/- 0.2 to 1.3 +/- 0.3 mL x min(-1) x kg(-1) (p <.05). Simultaneously, microdialysis lactate increased from 1.6 +/- 0.1 to 3.6 +/- 0.5 mmol/L (p <.05) with concomitant pyruvate increase and unchanged lactate/pyruvate ratio. Blood lactate increased and pH decreased. In the prostacyclin group at 8 hrs, intestinal vascular resistance of 6.9 +/- 0.8 mm Hg x mL x min(-1) x kg(-1) was lower and intestinal oxygen delivery of 3.2 +/- 0.3 was higher (p <.05) than in the control group at 8 hrs. Intestinal oxygen uptake of 0.54 +/- 0.10 mL x min(-1) x kg(-1) was higher than in the control group, in which oxygen uptake was 0.26 +/- 0.04 mL x min(-1) x kg(-1). Lactate, pyruvate, and pH were normalized at 8 hrs in the prostacyclin group.

CONCLUSION

Low-dose prostacyclin has beneficial effects on small intestinal perfusion during endotoxemia in this experimental cat model.

Acute meningococcaemia complicated by late onset gastrointestinal vasculitis

Extra-meningeal and non-cutaneous manifestations of meningococcal infection are well recognized but rare. Herein we report a little recognized complication of meningococcaemia, namely late-onset gastrointestinal vasculitis. In the case presented, the prostacycline analogue iloprost was used in an attempt to minimize incipient digital gangrene ina patient with evidence of protracted immunological phenomena. In addition, diclofenac was used to treat severe arthralgia. Withdrawal of iloprost on day 19 was associated with abdominal pain and peritonism. Laparotomy demonstrated ischaemia and ulceration in the caecum, and histology revealed full thickness mucosal ulceration with a prominent vasculitic process. It is postulated that these findings were immunologically mediated, with possible rebound vasoconstriction following withdrawal of iloprost. It is also possible that NSAID use contributed to the findings via cyto-toxicity to mucosal cells.