Effect of epoprostenol (prostacyclin, PGI2) on cerebral blood flow in man

Elevated prostacyclin biosynthesis in mice impacts memory and anxiety-like behavior

Prostacyclin is an endogenous lipid metabolite with properties of vasodilation and anti-platelet aggregation. While the effects of prostacyclin on the vascular protection have been well-documented, the role of this eicosanoid in the central nervous system has not been extensively studied. Recently, a transgenic mouse containing a hybrid enzyme, of cyclooxygenase-1 linked to prostacyclin synthase, was developed that produces elevated levels of prostacyclin in vivo. The goal of this study was to investigate whether increased prostacyclin biosynthesis could affect behavioral phenotypes in mice. Our results uncovered that elevated levels of prostacyclin broadly affect both cognitive and non-cognitive behaviors, including decreased anxiety-like behavior and improved learning in the fear-conditioning memory test. This study demonstrates that prostacyclin plays an important, but previously unrecognized, role in central nervous system function and behavior.

Prostacyclin and analogues for acute ischaemic stroke

BACKGROUND

Prostacyclin is an agent with a number of effects on platelets, blood vessels and nerve cells which might improve outcome after acute ischaemic stroke. NOTE: This review covers an area where no active research is taking place. It will be updated if relevant information becomes available, e.g. on completion of an appropriate study.

OBJECTIVES

The objective of this review was to assess the effect of prostacyclin or analogues on survival in people with acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched November 2003). For the first version, we also searched EMBASE (1980 to 1999), MEDLINE (1966 to 1999), Science Citation Index (1981 to 1999) and the Ottawa Stroke Trials Registry. We also contacted the manufacturers of prostacyclin and the principal investigators of the identified trials.

SELECTION CRITERIA

Randomised trials comparing prostacyclin or analogues with placebo or control. Trials where people were entered within one week of stroke onset were included.

DATA COLLECTION AND ANALYSIS

Information on the methods of randomisation, blinding, analysis, the number of patients randomised, dose and timing of prostacyclin or analogue, patient withdrawals, the number of deaths occurring in each trial, and trial quality, were collected and assessed.

MAIN RESULTS

Five trials involving 191 people were included. Six early deaths (within four weeks) occurred with prostacyclin, and nine with placebo (odds ratio (OR) 0.63, 95% confidence interval (CI) 0.22 to 1.85). One trial of 32 patients reported late deaths (by 10 to 18 months) in 50% of patients in each group.

REVIEWERS' CONCLUSIONS

Too few patients have been studied in randomised trials to allow conclusions to be drawn about the effect of prostacyclin treatment on survival of people with acute stroke.

Low-dose prostacyclin in treatment of severe brain trauma evaluated with microdialysis and jugular bulb oxygen measurements

BACKGROUND

The endogenous substance prostacyclin is a substance with the potential to improve microcirculation and oxygenation around contusions in the brain following a head trauma by its vasodilatory, antiaggregatory and antiadhesive effects. Microdialysis measurements of local concentrations of selected interstitial substances in the brain, and measurements of venous jugular bulb oxygenation reflecting overall brain oxygenation, might be useful to evaluate possible therapeutic effects of a specific therapy, such as treatment with prostacyclin.

METHODS

This case report study on six patients, of whom five were given prostacyclin, includes cerebral microdialysis measurements of interstitial lactate (n=5), pyruvate (n=3), glycerol (n=5) and glucose (n=4), and is combined with measurements of venous jugular bulb oxygenation in three of the patients. One microdialysis catheter was placed adjacent to a contusion, and in four of the patients another catheter was also placed in the contralateral less injured side for comparison. Low-dose prostacyclin infusion (0.5-1.0 ng kg(-1) min(-1)) was started when lactate concentrations in the more injured side was raised at a constant level for more than 10 h. The study also includes one patient used as control to whom no prostacyclin was given.

RESULTS

Lactate was markedly lower in the less injured than in the more injured area of the brain. During the prostacyclin infusion elevated lactate and lactate/pyruvate ratio were reduced. Elevated glycerol decreased, a low glucose increased and jugular bulb blood oxygenation increased following start of prostacyclin. The control patient showed an increase in lactate and lactate/pyruvate ratio.

CONCLUSION

The microdialysis data combined with the jugular bulb oxygenation data indicated that low-dose prostacyclin exerts effects compatible with improved oxygenation and reduced cell damage in the severely traumatised brain.

Prostacyclin and analogues for acute ischaemic stroke

BACKGROUND

Prostacyclin is an agent with a number of effects on platelets, blood vessels and nerve cells which might improve outcome after acute ischaemic stroke.

OBJECTIVES

The objective of this review was to assess the effect of prostacyclin or analogues on survival in people with acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group trials register (last searched: March 1999), Medline (from 1965), Embase (from 1980) and ISI (from 1981). We contacted drug companies.

SELECTION CRITERIA

Randomised trials comparing prostacyclin or analogues with placebo or control. Trials where people were entered within one week of stroke onset were included.

DATA COLLECTION AND ANALYSIS

Trial quality was assessed.

MAIN RESULTS

Five trials involving 191 people were included. Six early deaths (within four weeks) occurred with prostacyclin and nine with placebo (odds ratio of 0.63, 95% confidence interval 0.22 to 1.85). One trial of 32 patients reported late deaths (by 10 to 18 months) in 50% of patients in each group.

REVIEWER'S CONCLUSIONS

Too few patients have been studied in randomised trials to allow conclusions to be drawn about the effect of prostacyclin treatment on survival of people with acute stroke.

Effects of intravenous administration of prostacyclin on regional blood circulation in awake rats

1. The effects of intravenous infusion of prostacyclin (PGI2, 0.1, 0.2, 0.3 and 1.0 microg kg(-1) min(-1) lasting 5 min) on regional blood flow and regional vascular resistance have been studied in awake rats using the radioactive microsphere method. 2. The control values of blood flow to the heart, kidney, small intestine, hind limb muscle, pericranial skin and brain as well as the corresponding vascular resistance were not modified by an i.v. infusion (0.1 ml min(-1)) of Tris-buffer (the vehicle of PGI2). 3. The i.v. infusion of PGI2 produced graded dose-dependent decreases of MAP (r=0.87, P<0.001; ED20=0.73 [0.13-2.55] microg kg(-1) min(-1)) as well as decreases of vascular resistance in the heart (r=0.83, P<0.001; ED30=0.17 [0.09-0.31] microg kg(-1) min(-1)), pericranial skin (r=0.88, P<0.001; ED30=0.28 [0.18-0.43] microg kg(-1) min(-1)) and small intestine (r=0.74, P<0.001; ED30=0.21 [0.11-0.39] microg kg(-1) min(-1)), which led to dose-related increases of blood flow to these territories. 4. On the contrary, PGI2 increased vascular resistance in skeletal muscle (r=0.73, P<0.001; ED30=0.20 [0.10-0.39] microg kg(-1) min(-1)) with corresponding reductions in blood flow. The low doses reduced renal blood flow but there were no significant changes during the high ones. Cerebral vessels did not dilate during any infusion of PGI2 and cerebral blood flow decreased as MAP fell (r=0.56, P<0.01). 5. We conclude that, in awake rats, the coronary vessels are extremely sensitive to the vasodilating effect of PGI2 and that the mesenteric vessels and those of the pericranial skin are very responsive too. Moreover, autoregulation is inefficient to maintain cerebral blood flow during infusion of PGI2.

Effects of dobutamine and prostacyclin on cerebral blood flow velocity in septic patients

PURPOSE

Both dobutamine and prostacyclin (PGI2) have been used to increase oxygen delivery in septic patients, but their effects on cerebral blood flow have not been well studied.

METHODS

In 10 septic patients with altered mental status, stable hemodynamic status, and normal lactatemia, we investigated the effects of successive infusions of dobutamine at 5 micrograms/kg/min and PGI2 at 5 ng/kg/min on mean blood flow velocity in a middle cerebral artery, using transcranial Doppler flowmetry.

RESULTS

Mean flow velocity increased with dobutamine (from 52 +/- 4 to 62 +/- 6 cm/s, P < .005) but not with PGI2 (from 55 +/- 5 to 57 +/- 5 cm/s, P = not significant). Each substance significantly increased cardiac index. Dobutamine increased arterial pressure from 85 +/- 6 to 91 +/- 5 mm Hg (P < .05), but PGI2 decreased it from 87 +/- 6 to 77 +/- 5 mm Hg (P < .005). With each agent, mean flow velocity was correlated with cardiac index (r = .51, P < .001) but not with arterial pressure. PGI2 reduced PaO2 from 103 +/- 10 to 82 +/- 6 mm Hg (P < .005). Cerebral oxygen delivery (estimated by the product of mean flow velocity and arterial oxygen content) increased by 19% with dobutamine but remained unchanged with PGI2.

CONCLUSIONS

Dobutamine and PGI2 at the administered doses exert different effects on arterial pressure and middle cerebral artery flow velocity in septic patients. According to these data, dobutamine increases cerebral oxygen delivery more than PGI2.

Intravenous prostacyclin in acute nonhemorrhagic stroke: a placebo-controlled double-blind trial

The therapeutic efficacy of prostacyclin in nonhemorrhagic cerebral infarction was assessed in a placebo-controlled double-blind trial. A total of 80 patients with stroke onset within 24 hours were randomized into placebo (37 patients) and prostacyclin (43 patients) groups. Demographic data and risk factors were comparable. Patients in the prostacyclin group received a continuous i.v. infusion of prostacyclin at an average rate of 8.5 ng/kg/min for an average of 64 hours. The placebo group received vehicle only in a similar fashion. During treatment hemodynamic changes were more prominent in the patients receiving prostacyclin and included reduction of systolic and diastolic blood pressure and increase in pulse rate. In contrast there was only a slight (but significant) reduction of diastolic blood pressure in the placebo group. Neurologic deficit scores were determined on admission, at Day 3, and at Weeks 1, 2, and 4. Mean neurologic deficit scores upon entry were comparable in the placebo and prostacyclin groups, and a significant improvement in the score for neurologic deficit was noted in both. The placebo group tended to fare better throughout the study, with a significant difference in neurologic deficit score favoring the placebo group at Week 2 (p = 0.0048). Two patients in the placebo and one in the prostacyclin group died. The only difference in adverse reactions was flushing (6 patients in prostacyclin vs. 0 in placebo group, p less than 0.05). The results of this study suggest a lack of therapeutic efficacy of prostacyclin in a defined population of patients with nonhemorrhagic cerebral infarction.

Effect of indomethacin on cerebral blood flow, carbon dioxide reactivity and the response to epoprostenol (prostacyclin) infusion in man

Cerebral blood flow (CBF) has been measured using a non-invasive Xenon133 clearance technique in six normal subjects after 2 days pretreatment with oral indomethacin at a dose of 100 mg/day. The results were compared with placebo given in a double blind balanced cross-over design. Indomethacin was found to result in a reduction in resting CBF of about 25% but the reactivity of the cerebrovascular circulation to carbon dioxide was preserved at normal levels. Infusions of epoprostenol (prostacyclin, PGI2) at a dose of 5 ng/kg/min resulted in a reduction of CBF of about 10% after placebo but no significant change in CBF after indomethacin. The results suggest that prostaglandins are involved in the maintenance of cerebrovascular tone but not in the mechanism of cerebral vasodilation accompanying hypercapnia. The combination of indomethacin and PGI2 has been proposed as a treatment of cerebral artery spasm and the findings suggest that the combination therapy would not be accompanied by undesirable intracerebral steal.

The effect of intravenous epoprostenol (prostacyclin, PGI2) on cerebral blood flow and cardiac output in man

Epoprostenol (prostacyclin, PGI2) was given intravenously to seven healthy volunteers in a dose of 4 ng kg-1 min-1 over a 30 min period. Diastolic blood pressure fell but there was no change in cardiac output. The mean PGI2 concentration at the end of the infusion was 0.43 ng/ml (1.1 nM) and a significant inhibition of ADP-induced platelet aggregation occurred. Although obvious facial flushing occurred in all subjects and some subjects complained of headache, cerebral blood flow tended to fall. The results do not support the hypothesis that PGI2 acts as a physiological vasodilator involved in the homeostasis of normal cerebral blood flow.