Circulatory and respiratory effects of different doses of prostaglandin E1 in man

Mechanistic actions of oxygen and methylxanthines on respiratory neural control and for the treatment of neonatal apnea

Apnea remains one of the most concerning and prevalent respiratory disorders spanning all ages from infants (particularly those born preterm) to adults. Although the pathophysiological consequences of apnea are fairly well described, the neural mechanisms underlying the etiology of the different types of apnea (central, obstructive, and mixed) still remain incompletely understood. From a developmental perspective, however, research into the respiratory neural control system of immature animals has shed light on both central and peripheral neural pathways underlying apnea of prematurity (AOP), a highly prevalent respiratory disorder of preterm infants. Animal studies have also been fundamental in furthering our understanding of how clinical interventions (e.g. pharmacological and mechanical) exert their beneficial effects in the clinical treatment of apnea. Although current clinical interventions such as supplemental O2 and positive pressure respiratory support are critically important for the infant in respiratory distress, they are not fully effective and can also come with unfortunate, unintended (and long-term) side-effects. In this review, we have chosen AOP as one of the most common clinical scenarios involving apnea to highlight the mechanistic basis behind how some of the interventions could be both beneficial and also deleterious to the respiratory neural control system. We have included a section on infants with critical congenital heart diseases (CCHD), in whom apnea can be a clinical concern due to treatment with prostaglandin, and who may benefit from some of the treatments used for AOP.

Cervical spondylotic amyotrophy

Cervical spondylotic amyotrophy is characterized with weakness and wasting of upper limb muscles without sensory or lower limb involvement. Two different mechanisms have been proposed in the pathophysiology of cervical spondylotic amyotrophy. One is selective damage to the ventral root or the anterior horn, and the other is vascular insufficiency to the anterior horn cell. Cervical spondylotic amyotrophy is classified according to the most predominantly affected muscle groups as either proximal-type (scapular, deltoid, and biceps) or distal-type (triceps, forearm, and hand). Although cervical spondylotic amyotrophy always follows a self-limited course, it remains a great challenge for spine surgeons. Treatment of cervical spondylotic amyotrophy includes conservative and operative management. The methods of operative management for cervical spondylotic amyotrophy are still controversial. Anterior decompression and fusion or laminoplasty with or without foraminotomy is undertaken. Surgical outcomes of distal-type patients are inferior to those of proximal-type patients.

Effects of indomethacin on cerebrovascular response to hypercapnea and hypocapnea in breath-hold diving and obstructive sleep apnea

We tested whether breath hold divers (BHD) and obstructive sleep apnea (OSA) subjects had similar middle cerebral artery velocity (MCAV) responses to hypercapnea and hypocapnea. We analyzed changes in MCAV (cm/s) in response to hypocapnea and hyperoxic hypercapnea during placebo or after 90 min of oral indomethacin (100 mg) in BHD (N=7) and OSA (N=7). During control hypercapnea MCAV increased for 54.4% in BHD and 48.4% in OSA. Indomethacin blunted the MCAV increase in response to hypercapnea in BHD (P=0.02), but not in OSA. Indomethacin attenuated the mean arterial pressure response in BHD, but not in OSA. The blunted MCAV responses to hypercapnea with indomethacin in BHD, but not in OSA patients suggests that (a) the normal contribution of local vasodilating mechanisms to the cerebrovascular responses to hypercapnea is absent in OSA patients and (b) exposure to chronic/repeated apneas is not causal per se in limiting the contribution of vasodilating mechanisms to the cerebrovascular responses to hypercapnea in OSA.

Influence of cerebral blood flow on breathing stability

Our previous work showed a diminished cerebral blood flow (CBF) response to changes in Pa(CO(2)) in congestive heart failure patients with central sleep apnea compared with those without apnea. Since the regulation of CBF serves to minimize oscillations in H(+) and Pco(2) at the site of the central chemoreceptors, it may play an important role in maintaining breathing stability. We hypothesized that an attenuated cerebrovascular reactivity to changes in Pa(CO(2)) would narrow the difference between the eupneic Pa(CO(2)) and the apneic threshold Pa(CO(2)) (DeltaPa(CO(2))), known as the CO(2) reserve, thereby making the subjects more susceptible to apnea. Accordingly, in seven normal subjects, we used indomethacin (Indo; 100 mg by mouth) sufficient to reduce the CBF response to CO(2) by approximately 25% below control. The CO(2) reserve was estimated during non-rapid eye movement (NREM) sleep. The apnea threshold was determined, both with and without Indo, in NREM sleep, in a random order using a ventilator in pressure support mode to gradually reduce Pa(CO(2)) until apnea occurred. results: Indo significantly reduced the CO(2) reserve required to produce apnea from 6.3 +/- 0.5 to 4.4 +/- 0.7 mmHg (P = 0.01) and increased the slope of the ventilation decrease in response to hypocapnic inhibition below eupnea (control vs. Indo: 1.06 +/- 0.10 vs. 1.61 +/- 0.27 l x min(-1) x mmHg(-1), P < 0.05). We conclude that reductions in the normal cerebral vascular response to hypocapnia will increase the susceptibility to apneas and breathing instability during sleep.

Influence of cerebrovascular function on the hypercapnic ventilatory response in healthy humans

An important determinant of [H(+)] in the environment of the central chemoreceptors is cerebral blood flow. Accordingly we hypothesized that a reduction of brain perfusion or a reduced cerebrovascular reactivity to CO(2) would lead to hyperventilation and an increased ventilatory responsiveness to CO(2). We used oral indomethacin to reduce the cerebrovascular reactivity to CO(2) and tested the steady-state hypercapnic ventilatory response to CO(2) in nine normal awake human subjects under normoxia and hyperoxia (50% O(2)). Ninety minutes after indomethacin ingestion, cerebral blood flow velocity (CBFV) in the middle cerebral artery decreased to 77 +/- 5% of the initial value and the average slope of CBFV response to hypercapnia was reduced to 31% of control in normoxia (1.92 versus 0.59 cm(-1) s(-1) mmHg(-1), P < 0.05) and 37% of control in hyperoxia (1.58 versus 0.59 cm(-1) s(-1) mmHg(-1), P < 0.05). Concomitantly, indomethacin administration also caused 40-60% increases in the slope of the mean ventilatory response to CO(2) in both normoxia (1.27 +/- 0.31 versus 1.76 +/- 0.37 l min(-1) mmHg(-1), P < 0.05) and hyperoxia (1.08 +/- 0.22 versus 1.79 +/- 0.37 l min(-1) mmHg(-1), P < 0.05). These correlative findings are consistent with the conclusion that cerebrovascular responsiveness to CO(2) is an important determinant of eupnoeic ventilation and of hypercapnic ventilatory responsiveness in humans, primarily via its effects at the level of the central chemoreceptors.

Acute arm paresis with cervical spondylosis: three case reports

BACKGROUND

The mild type of anterior spinal artery syndrome (ASAS) is characterized by motor loss with an absent or insignificant sensory deficit due to a disturbance in the blood supply to the anterior horn of the spinal cord. The clinical symptoms of cervical spondylotic amyotrophy (CSA) are motor loss or atrophy with an absent or insignificant sensory deficit or a long tract sign; however, the pathophysiology has not been clarified.

METHODS

Three patients who suffered from palsy of the deltoid and biceps brachii are presented. Magnetic resonance imaging confirmed the intrinsic cord disease as the cause of the paresis. We measured the central motor conduction time (CMCT) and the latencies of the tendon reflex (T waves) of the biceps and triceps and those of the F waves of the abductor pollicis brevis and abductor digiti minimi before, 2 weeks after, and 3 months after starting intravenous injections of prostaglandin E(1) (PGE(1)).

RESULTS

In these 3 cases, restoration of muscle strength began after starting injection of PGE(1). The electrophysiologic diagnosis revealed a disturbance of the motor conduction, in the CMCT and the latencies of the T waves, in the paretic muscle, which is more severe than that in other muscles. The radiological diagnosis suggested damage in the spinal cord. Improvements in the disturbance of the motor conduction and those of symptoms were parallel.

CONCLUSION

From symptomatologic or radiological viewpoints, it is difficult to differentiate CSA from ASAS with cervical spondylosis. This suggests that there have been patients with ASAS whom we have diagnosed as CSA, and we may add administration of PGE(1) to the treatment for the patients with CSA. The present 3 patients showed improvement of muscle strength after starting injections of PGE(1). Although this improvement was measured by an electrophysiologic method, the mechanisms of PGE(1) require further study.

The heart ofCiona intestinalis: eicosanoid-generating capacity and the effects of precursor fatty acids and eicosanoids on heart rate

Eicosanoids are a group of oxygenated fatty-acid derivatives formed from C20 polyunsaturated fatty acids including arachidonic and eicosapentaenoic acids. In mammals, these compounds have been shown to be key molecules in several physiological processes including regulation of the vascular system. This study determined whether eicosanoids or their precursors are involved in the regulation of heart rate in the sea squirt Ciona intestinalis. Eicosanoid generation by both heart and blood cells was measured. The major lipoxygenase products formed were both derivatives of eicosapentaenoic acid,namely 8- and 12-hydroxyeicosapentaenoic acids (8-HEPE and 12-HEPE). Smaller amounts of 8,15-dihydroxyeicosapentaenoic acid (8,15-diHEPE) were also formed. The cyclo-oxygenase product prostaglandin E was also found in small amounts in the heart. Isolated hearts were exposed either to these fatty acid precursors or to 8-HEPE, 12-HEPE or prostaglandin E3, and the effect on heart rate was recorded. Both eicosapentaenoic and arachidonic acids stimulated the heart rate at concentrations between 50 and 200 μmoll-1. 12-HEPE(5 μmoll-1) and prostaglandin E3 (50μmoll-1) caused a modest increase in heart rate, while 8-HEPE had no significant effects at any of the time periods studied (≤180 min). Overall, the results show that arachidonic and eicosapentaenoic acids have limited effects on heart rate and only at concentrations unlikely to be routinely liberated in vivo. Similarly, the eicosanoids tested had a minor stimulatory activity on heart rate. The potential mechanisms for this stimulation are discussed. Overall, these results suggest that such compounds are of limited importance in regulating the heart and vascular system of sea squirts.

Small dose of prostaglandin E(1) increases cardiac output without altering blood volume

STUDY OBJECTIVE

To investigate the effect of small dose of intravenous (IV) prostaglandin E(1) (PGE(1)) on blood volume (BV) and cardiac output (CO) by pulse dye-densitometry (PDD) in patients administered isoflurane anesthesia.

DESIGN

Prospective, randomized study.

SETTING

University hospital.

PATIENTS

14 ASA physical status I and II adult patients undergoing elective neurosurgery.

INTERVENTIONS

Patients were randomly assigned to either the PGE(1) group (n = 7) or the control group (n = 7). Anesthesia was induced with thiamylal, fentanyl, and vecuronium, and maintained with isoflurane and nitrous oxide. When the cardiovascular system stabilized after craniotomy and incision of the dura mater, we administered a small dose of PGE(1) at a rate of 0.02 microg/kg/min (PGE(1) group) or saline at a rate of 2 mL/min (control group).

MEASUREMENTS AND MAIN RESULTS

Blood volume, CO, and mean transit time (MTT) were measured by PDD before and 60 minutes after the start of administration. At the same timing, mean arterial pressure (MAP), heart rate (HR), and central venous pressure (CVP) were measured, and systemic vascular resistance (SVR), cardiac index (CI), and CO/BV were computed. As for MAP, there was no significant difference within a group and between groups. In the PGE(1) group, significant increases were noted in CI from 2.54 +/- 0.46 to 3.24 +/- 0.83 (mean +/- SD) L/min/m(2) (p < 0.05), in CO/BV from 0.90 +/- 0.24 to 1.19 +/- 0.33 (p < 0.05), and in HR from 65.7 +/- 10.1 to 74.9 +/- 12.1 bpm (p < 0.05), and a significant decrease was observed in MTT from 22.3 +/- 6.5 to 18.2 +/- 5.1 seconds (p < 0.05 ). Cardiac index and CO/BV in the PGE(1) group increased higher than in the control group, while BV, CVP and SVR remained consistent in both groups.

CONCLUSIONS

A small dose of PGE(1), low enough not to provoke hypotension, increased CO without alterations in BV. The increase in CO seemed to be mainly due to an increase in HR.

Neutralization of prostaglandin E1 intravenous solution reduces infusion phlebitis

Previous studies have shown moderate or severe phlebitis at the site of venipuncture in some patients who receiving prostaglandin E1 (PGE1) infusion therapy. Such phlebitis is sometimes severe enough to necessitate the cessation of PGE1 therapy. This study investigated how to continue PGE1 infusion therapy for 3 weeks with tolerable phlebitis. Although a 60 microg dose of PGE1 is usually dissolved in 500 mL of fluid to avoid phlebitis, we used 200 mL to prevent volume overload. This PGE1 solution was neutralized to pH 7.4 with 4 mL of 7% sodium bicarbonate. We examined the frequency and severity of phlebitis among patients who received a 2-h PGE1 infusion twice daily. Eighteen patients who were hospitalized for peripheral vascular disease between June 1998 and May 1999 were studied. All of them were men and their mean age was 63.3 +/- 8.9 years (range: 47-78 years). Fourteen patients had arteriosclerosis obliterans and four had Buerger's disease. When the severity of phlebitis was determined according to Dinley's criteria, two patients (11%) had grade 0, four patients (22%) had grade 1, eleven patients (61%) had grade 2, and one patient (6%) had grade 3 phlebitis. Usually, PGE1 infusion therapy is stopped when phlebitis reaches grade 4 or more, but there were no such cases in this study. We also found that aging was significantly correlated with a decrease in the severity of phlebitis (Spearman's rank correlation test: r = -0.545, p = 0.0193).

Perinatal changes in choroidal 15-hydroxyprostaglandin dehydrogenase: implications for prostaglandin removal from brain

We have previously shown in the sheep fetus at 0.7 and 0.9 gestation that the choroid plexus, unlike brain parenchyma, catabolizes prostaglandins (PGs). Peculiarly, in the choroid plexus, PGE(2) catabolism persists throughout the neonatal period to abate in the adult, while PGF(2alpha) catabolism abates shortly after birth. To explain this differential behavior and elucidate the function of catabolic enzymes, we examined the cellular location and activity of the rate-limiting enzyme for PGE(2) and PGF(2alpha) catabolism, 15-hydroxyprostaglandin dehydrogenase (15-PGDH). Immunofluorescence histochemistry and immunogold electronmicroscopy revealed abundant 15-PGDH expression in the epithelial cytosol close to the brush-border membrane at 0.7 and 0.9 gestation. In contrast, at 5 and 15 days postnatal, 15-PGDH was found throughout the cytosol of stromal fibroblasts. No staining was observed at either location in pregnant adults. PGF(2alpha) catabolism was minimal in the total homogenate and 100000xg supernatant of the fetal choroid plexus at 0.7 and 0.9 gestation, while PGE(2) catabolism was evident at 0.7 gestation only. In contrast, both PGs were catabolized in minced specimens at either age. In conclusion, our study shows immunoreactive 15-PGDH in the choroid plexus from fetal and neonatal, but not pregnant adult, sheep. Results suggest that PGE(2) catabolism is not as critically dependent as that of PGF(2alpha) on tissue integrity and 15-PGDH location. Given the key role being assigned to the choroid plexus in PG removal from brain, we speculate that persistence of PGE(2) catabolism into the early postnatal period protects against central respiratory depression caused by the compound during this susceptible stage of development.

Protective effect of prostaglandin E1 against ischemia/reperfusion-induced liver injury: results of a prospective, randomized study in cirrhotic patients undergoing subsegmentectomy

BACKGROUND/AIMS

The cytoprotective effects of prostaglandin E1 on livers suffering from ischemia/reperfusion injury in the clinical setting are unproved. These effects were examined, focusing on inflammatory cytokine and nitric oxide metabolism.

METHODS

Twenty-four cirrhotic patients with hepatocellular carcinoma undergoing subsegmentectomy under ischemia induced only by Pringle's maneuver were divided into two groups (patients given prostaglandin E1 by injection and untreated controls) and postoperative results were compared. Peripheral blood was taken perioperatively and the plasma aminotransferase, cytokines and nitrate/nitrite levels of the two groups were compared. Two liver specimens were taken from each patient, one before ischemia and the other after hepatectomy, and the levels of inducible nitric oxide synthase and cytokine mRNAs and proteins were analyzed.

RESULTS

Although no apparent differences were recognized in postoperative complications or duration of postoperative hospital stay between the groups, the perioperative plasma aminotransferase level was significantly lower in the prostaglandin E1 group. Significant differences were also seen in interleukin-6 and nitrate plasma levels during the observation period and the interleukin-6 protein levels in the liver supernatants after hepatectomy in the two groups. In contrast, no significant differences were apparent between the interleukin-1 beta and tumor necrosis factor-alpha plasma levels of the two groups. The corrected fluorescence activities of interleukin-6 and inducible nitric oxide synthase mRNAs in the liver after hepatectomy correlated significantly. No interleukin-1 beta or tumor necrosis factor-alpha mRNAs or proteins were detected.

CONCLUSIONS

Prostaglandin E1 exerted hepatoprotective effects on livers suffering from ischemia/reperfusion injury, and interleukin-6 might play an important role in these effects.

Effects of systemic prostaglandin E1 on hepatic amino acid-nitrogen metabolism in patients with cirrhosis

Prostaglandins of the E (PGE) series have long been considered "catabolic" hormones, but recent data suggest that they may be secreted in critically ill patients to counteract stress hormones, stimulating protein synthesis. Their use is under scrutiny to improve hepatic microcirculation and as cytoprotective agents. We tested the effects of PGE1 on hepatic and whole-body nitrogen metabolism in eight patients with cirrhosis. Urea-nitrogen synthesis rate, alpha-amino-nitrogen levels, and nitrogen exchange were measured in the basal, postabsorptive state and in response to continuous alanine infusion, in paired experiments, during superinfusion of PGE1 or saline. Splanchnic and systemic hemodynamics were assessed by echo-Doppler at the beginning and at the end of each experiment. PGE1 produced a rapid fall in plasma amino acids and in urea-nitrogen synthesis rate, as well as a positive nitrogen exchange. The slope of the regression of alpha-amino-nitrogen levels on urea-nitrogen synthesis rate, a measure of liver cell metabolic activity, was not affected, but the regression line was shifted rightward, suggesting a nitrogen-sparing effect of PGE1. Mesenteric artery and portal flow were unchanged, whereas femoral artery flow increased by 30%. Insulin and glucagon levels were not systematically different. We conclude that PGE1 reduces hepatic urea synthesis rate, independent of hormones and/or hepatic flow, possibly acting at the peripheral level on amino acid transport, thus reducing amino acid supply to the liver. The resulting net nitrogen sparing might be the basis for the beneficial effect of PGE1 in clinical hepatology.

Effects of systemic prostaglandin E1 on splanchnic and peripheral haemodynamics in control subjects and in patients with cirrhosis

Prostaglandins of the E series showed metabolic and clinical effects in patients with liver disease; changes in splanchnic haemodynamics might be involved. Blood flow in femoral and mesenteric artery and in the portal vein was measured by echo-Doppler in 10 controls and 14 cirrhotic patients, in response to the systemic infusion of a PGE1 analogue (30 micrograms/h for 2-6 h) or saline, performed in random order. Intraparenchymal resistive and pulsatility indices in the liver, spleen and kidney were also measured. In both groups PGE1 increased femoral artery flow by 40%, irrespective of infusion time. Heart rate increased slightly, whereas mean arterial pressure decreased. There were no changes in mesenteric artery and portal vein flow, as well as in resistance indices. Saline infusion increased femoral artery flow by 4%. PGE1 infusion does not produces significant effects on Doppler-assessed splanchnic hemodynamics in controls and in cirrhotic patients, in spite of significant effects on peripheral circulation.

Effect of TFC-612, a 7-thia prostaglandin E1 derivative, on a peripheral arterial occlusive disease model in rats

TFC-612, methyl 6-[((1R,2S,3R)-3-hydroxy-2-[(1E,3S,5R)-3-hydroxy-5- methyl-1-nonenyl)-5-oxocyclopentyl]-thio]-hexanoate, inhibited the progression of the lesion in a lauric acid-induced peripheral arterial occlusive model at 1.0 mg/kg p.o. or 1.0 microgram/rat/h s.c. in rats. Aspirin (32 mg/kg, p.o.), an anti-platelet drug, did not suppress the lesion growth. On the other hand, ketanserin (10 mg/kg, p.o.), a 5-HT2 antagonist, also inhibited the progression of the lesion. In vitro, TFC-612 inhibited rat platelet aggregation induced by collagen and ADP with IC50 values of 5.4 ng/mL and 9.5 ng/mL, respectively. Aspirin also inhibited collagen-induced aggregation with an IC50 value of 6.3 micrograms/mL, but not ADP-induced aggregation at 180 micrograms/mL. Ketanserin had no effect on either aggregation at 40 micrograms/mL. In ex vivo experiments, aspirin inhibited platelet aggregation induced by collagen at 10 and 32 mg/kg in rats. However, TFC-612 showed significant inhibition only at 10 mg/kg. TFC-612 and ketanserin increased dermal blood flow in the rat paw at 1.0 microgram/kg i.v. and 100 micrograms/kg i.v., respectively. Aspirin had no effect on blood flow at 3.2 mg/kg i.v. These results suggest that the improvement of microcirculation, in addition to anti-platelet action by TFC-612, contributes to its inhibitory effect in a peripheral arterial occlusive model in rats.

Spinal cord blood flow during prostaglandin E1 induced hypotension

To evaluate the effect of prostaglandin E1 (PGE1) induced hypotension on spinal blood flow (SBF) during spinal surgery, SBF was measured under isoflurane anaesthesia by the heat clearance method in 10 patients with spinal tumour. An initial dose of 0.1 microgram/kg/min of PGE1 was administered intravenously after spinal opening and the dose was adjusted to maintain the mean arterial blood pressure (MAP) at about 60 mmHg. PGE1 was discontinued at the completion of the operative produces. After starting PGE1, MAP and rate pressure product (RPP) decreased significantly compared with preinfusion values (P < 0.01), and the hypotensive effect of PGE1 remained constant at 60 min after its discontinuation. Heart rate (HR) did not change throughout the study. SBF showed no change over the course of PGE1 induced hypotension (preinfusion: 47.8 +/- 21.7 ml/100 g/min, at 15 min: 41.2 +/- 16.9 ml/100 g/min, at 30 min: 40.4 +/- 16.8 ml/100 g/min, and at 60 min: 46.1 +/- 16.3 ml/100 g/min, respectively). These results suggest that PGE1 may be a useful drug for hypotensive anaesthesia in surgery for spinal cord tumours because PGE1 maintained SBF.

Epidural blood flow during prostaglandin E1 or trimethaphan induced hypotension

To evaluate the effect of prostaglandin E1 (PGE1) or trimethaphan (TMP) induced hypotension on epidural blood flow (EBF) during spinal surgery, EBF was measured using the heat clearance method in 30 patients who underwent postero-lateral interbody fusion under isoflurane anaesthesia. An initial dose of 0.1 microgram.kg-1.min-1 of PGE1 (15 patients), or 10 micrograms.kg-1.min-1 of TMP (15 patients) was administered intravenously after the dural opening and the dose was adjusted to maintain the mean arterial blood pressure (MAP) at about 60 mmHg. The hypotensive drug was discontinued at the completion of the operative procedure. After starting PGE1 or TMP, MAP and rate pressure product (RPP) decreased significantly compared with preinfusion values (P < 0.01), and the degree of hypotension due to PGE1 remained constant until 60 min after its discontinuation. Heart rate (HR) did not change in either group. EBF did not change during PGE1 infusion whereas in the TMP group, EBF decreased significantly at 30 min and 60 min after the start of TMP (preinfusion: 45.9 +/- 13.9 ml/100 g/min. 30 min: 32.3 +/- 9.9 ml/100 g/min (P < 0.05). 60 min: 30 +/- 7.5 ml/100 g/min (P < 0.05). These results suggest that PGE1 may be preferable to TMP for hypotensive anaesthesia in spinal surgery because TMP decreased EBF.

Epidural blood flow during prostaglandin E1 or trimethaphan induced hypotension

To evaluate the effect of prostaglandin E1 (PGE1) or trimethaphan (TMP) induced hypotension on epidural blood flow (EBF) during spinal surgery, EBF was measured using the heat clearance method in 30 patients who underwent postero-lateral interbody fusion under isoflurane anaesthesia. An initial dose of 0.1 microgram.kg-1.min-1 of PGE1 (15 patients), or 10 micrograms.kg-1.min-1 of TMP (15 patients) was administered intravenously after the dural opening and the dose was adjusted to maintain the mean arterial blood pressure (MAP) at about 60 mmHg. The hypotensive drug was discontinued at the completion of the operative procedure. After starting PGE1 or TMP, MAP and rate pressure product (RPP) decreased significantly compared with preinfusion values (P < 0.01), and the degree of hypotension due to PGE1 remained constant until 60 min after its discontinuation. Heart rate (HR) did not change in either group. EBFF did not change during PGE1 infusion whereas in the TMP group, EBF decreased significantly at 30 and 60 min after the start of TMP (preinfusion: 45.9 +/- 13.9 ml/100g/min. 30 min: 32.3 +/- 9.9 ml/100 g/min (P < 0.05). 60 min: 30 +/- 7.5 ml/100 g/min (P < 0.05)). These results suggest that PGE1 may be preferable to TMP for hypotensive anaesthesia in spinal surgery because TMP decreased EBF.

Vasodilators during cerebral aneurysm surgery

The objective of this review is to review the anaesthetic implications of vasoactive compounds particularly with regard to the cerebral circulation and their clinical importance for the practicing anaesthetist. Material was selected on the basis of validity and application to clinical practice and animal studies were selected only if human studies were lacking. Hypotensive drugs have been used to induce hypotension and in the treatment of intraoperative hypertension during cerebral aneurysm surgery. After subarachnoid haemorrhage, cerebral blood flow is reduced and cerebral vasoreactivity is disturbed which may lead to brain ischaemia. Also, cerebral arterial vasospasm decreases cerebral blood flow, and may lead to delayed ischaemic brain damage which is a major problem after subarachnoid haemorrhage. Recently, the use of induced hypotension has decreased although it is still useful in patients with intraoperative aneurysm rupture, giant cerebral aneurysm, fragile aneurysms and multiple cerebral aneurysms. In this review, a variety of vasodilating agents, prostaglandin E1, sodium nitroprusside, nitroglycerin, trimetaphan, adenosine, calcium antagonists, and inhalational anaesthetics, are discussed for their clinical usefulness. Sodium nitroprusside, nitroglycerin and isoflurane are the drugs of choice for induced hypotension. Prostaglandin E1, nicardipine and nitroglycerin have the advantage that they do not alter carbon dioxide reactivity. Local cerebral blood flow is increased with nitroglycerin, decreased with trimetaphan and unchanged with prostaglandin E1. Intraoperative hypertension is a dangerous complication occurring during cerebral aneurysm surgery, but its treatment in association with subarachnoid haemorrhage is complicated in cases of cerebral arterial vasospasm because fluctuations in cerebral blood flow may be exacerbated. Hypertension should be treated immediately to reduce the risk of rebleeding and intraoperative aneurysmal rupture and the choice of drugs is discussed. Although the use of induced hypotension has declined, the control of arterial blood pressure with vasoactive drugs to reduce the risk of intraoperative cerebral aneurysm rupture is a useful technique. Intraoperative hypertension should be treated immediately but the cerebral vascular effects of each vasodilator should be understood before their use as hypotensive agents.

Intra-operative blood pressure control by prostaglandin E1 in patients with hypertension and ischemic heart disease--a multi-center study

The purpose of this multi-center study was to evaluate the efficacy and safety of prostaglandin E1 (PGE1) administration in achieving deliberate hypotension and in treating intraoperative hypertension for patients with a history of hypertension and ischemic heart disease. PGE1 (0.08 microg.kg(-1).min(-1)) decreased systolic blood pressure from 125 +/- 29 to 106 +/- 22 mmHg (mean +/- SD) in the deliberate hypotension group (n = 158) and from 155 +/- 34 to 125 +/- 32 mmHg in the antihypertension group (n = 55). The heart rate significantly increased from 80 +/- 15 to 85 +/- 18 beats.min(-1) in the deliberate hypotension group, but was not significantly altered in the antihypertension group. The time required to obtain the desired level of blood pressure was approximately 20 min in the deliberate hypotension group. When the infusion was stopped, blood pressure returned approximately to the preinfusion level within about 20 min. No rebound hypertension was observed. PGE1 significantly increased the urine flow in patients who had a low urine flow before PGE1 infusion. Thirteen out of 213 patients (5.6%) had side effects such as excessive hypotension (1%), phlebitis (3%), and unexpected tachycardia (1%), which were alleviated gradually after discontinuation of PGE1 infusion. No dysarrhythmia and further ST segment changes in the electrocardiograms were observed. These findings suggest that PGE1 can be safely used to control arterial blood pressure during surgery in patients having preoperative hypertension and ischemic heart disease.

Carbon dioxide reactivity and local cerebral blood flow during prostaglandin E1- or nitroglycerin-induced hypotension

The aims of this randomized study were to determine the effect of prostaglandin-(PGE1) or nitroglycerin-(TNG) induced hypotension on local cerebral blood flow (LCBF) and carbon dioxide reactivity during isoflurane anaesthesia in 20 patients after subarachnoid haemorrhage (SAH) scheduled for aneurysm clip ligation. Mean arterial blood pressure decreased immediately, after giving either PGE1 or TNG. The LCBF, measured using a thermal gradient blood flowmeter, was unchanged after PGE1, while the LCBF increased after TNG infusion (control; 47.6 + 10.0, 60 min after infusion; 55.1 +/- 6.5 (P < 0.05), before clipping; 55.5 +/- 7.8 (P < 0.05)) but returned to control values after its discontinuation. Carbon dioxide reactivity, calculated from % delta LCBF/delta PaCO2 was unchanged during PGE1- or TNG-induced hypotension (PGE1; 2.13 +/- 0.9, 2.48 +/- 0.68 and 2.31 +/- 0.79%/mmHg for before, during and after hypotension respectively) (TNG; 2.08 +/- 0.68, 2.17 +/- 0.64 and 2.02 +/- 0.69%/mmHg for before, during and after hypotension respectively). Carbon dioxide reactivity correlated with presurgical neurological status (rs = -0.7, -0.648 and -0.458 for before, during and after hypotension respectively) and the initial LCBF (rs = -0.605). These results suggest that both PGE1 and TNG are useful drugs for induced hypotension for cerebral aneurysm surgery, because neither decreased LCBF.

Prostaglandin E1 reduces blood loss during and after resection of lumbar herniated disc

Controlled hypotension was employed during resection of lumbar herniated disc on 10 patients. Prostaglandin E(1) (PG) was used as a hypotensive agent. The systolic blood pressure was lowered less than 100 mmHg in the hypotensive group. The average blood loss during surgery was 95 +/- 41 ml for the hypotensive group compared with 154 +/- 81 ml for the normotensive group ( P < 0.05). The blood loss after surgery was also significantly less in the hypotensive group than in the normotensive group ( P < 0.05). We conclude that PG is an effective hypotensive agent on blood loss during and after surgery.

Prostaglandin E1 enhances hepatic portal venous flow by dilating the portal vascular bed in 70% hepatectomized dog

The effects of portal, hepatic arterial and femoral venous administration of prostaglandin E1 (PGE) on portal venous flow (PVF) and hepatic arterial flow HAF were examined before and after 70% hepatectomy in anesthetized dogs. In the hepatectomized condition, portal venous administration of PGE (0.5 microgram/kg/min) caused an increase in PVF without any change in systemic arterial pressure (SAP). HAF was unchanged following the injection. The portal effect of PGE on PVF was dose-dependent, and a reduction in portal venous resistance was seen. However, the same dose of PGE failed to change PVF under intact liver conditions. Hepatic arterial administration of PGE (0.5 microgram/kg/min) brought no significant change in PVF or HAF, with or without hepatectomy. Femoral venous administration of PGE (0.5 micrograms/kg/min) produced an increase in PVF concomitant with a significant decrease in SAP. HAF showed no change after the injection. A decrease in PVR was seen only in the hepatectomized condition. It is concluded that PGE is potent in increasing PVF in the hepatectomized condition, and the portal vasculature is involved as the site of action.

Local cerebral blood flow with prostaglandin E1 or trimethaphan during cerebral aneurysm clip ligation

This study was performed to examine changes in local cerebral blood flow during hypotensive anaesthesia with either prostaglandin E1 (PGE1) or trimethaphan (TMP). Local cerebral blood flow (LCBF), mean blood pressure (MBP), heart rate (HR), and hourly urine output (UO) were studied in 51 patients undergoing cerebral aneurysm surgery with neuroleptanalgesia (NLA). The incidence of vasospasm after aneurysm surgery, and outcome (Glasgow Outcome Scale) at discharge were evaluated. Measurements of LCBF were made using a thermal gradient blood flow meter. The dose of PGE1 or TMP was adjusted to maintain MBP at about 70 mmHg, and LCBF was studied during and after PGE1 or TMP administration. Hypotensive drugs were discontinued at the completion of aneurysm clipping. After starting PGE1 or TMP, MBP decreased immediately, but HR did not change in either group. The LCBF decreased 30 min after the start of TMP administration and increased immediately after its discontinuation, whereas PGE1 did not affect LCBF. Urine output increased during PGE1 administration but was unchanged during TMP. Neither drug affected surgical outcome or the incidence of vasospasm. These results suggest that PGE1 may be preferable to trimethaphan for hypotensive anaesthesia in cerebral aneurysm surgery because LCBF is maintained.

Measurement of splanchnic circulation in dogs: changes induced by prostaglandin E1

In seven anesthetized dogs the effects of intravenously administered prostaglandin E1 on mesenteric arterial and portal venous blood flows and pancreatic capillary blood flow were measured with a transit-time ultrasonic volume flowmeter and a laser Doppler flowmeter. Basal blood flow of the superior mesenteric artery and of the portal vein were 5.7 +/- 0.6 and 11.2 +/- 1.0 ml/min/kg, respectively. Prostaglandin E1 caused a dose-dependent increase in these blood flows. The maximal effect was observed at a dose of 1.0 microgram/kg, when the superior mesenteric arterial blood flow increased 117.9 +/- 3.2% and the portal venous blood flow increased 99.4 +/- 1.7%. Prostaglandin E1 produced an initial rapid increase, followed by a decrease in pancreatic capillary blood flow. The results indicate that the flowmeters used in the present study are widely available for the study of splanchnic circulation and may have a possibility for clinical application.

PGF2 alpha and breathing pattern in newborn pigs

The effect of PGF2 alpha has been evaluated in 11 unanaesthetized unrestrained piglets and in 3 anaesthetized piglets (2-3 days old) using a barometric-plethysmographic technique. PGF2 alpha (mg 0.25/pig) was administered as aerosol for 5 min. In 3 of the unanaesthetized newborn pigs the effect of PGF2 alpha aerosol has been evaluated after indomethacin (mg 1/Kg i.v.). The vagal dependent activity of the prostaglandin was also evaluated after atropine (mg 0.08/Kg i.m.). Our results show that PGF2 alpha in newborn pigs causes hypoventilation due to a decrease in respiratory rate and to a lengthening in TE. The changes in TE are due to an increase in the incidence and duration of apneic events characterizing the respiratory activity at birth. After indomethacin PGF2 alpha does not change the breathing pattern. Atropine only partially reduces the effects of PGF2 alpha while, after anaesthesia, prostaglandin does not change the breathing pattern. Consequently our results show that PGF2 alpha in newborn animals similar to other prostaglandins acts as a depressant of respiratory activity.

The hemodynamic and metabolic changes in prostaglandin E1-induced hypotension in dogs--a comparative study with trimetaphan-induced hypotension

The hemodynamic and metabolic changes in hypotensive state induced with prostaglandin E1 (PGE1) or trimetaphan (TMT) infusion were investigated in dogs. Mean arterial pressure was decreased by about 50% with 1.58 microg/kg/min of PGE1 or 45 microg/kg/min of TMT. Heart rate, pulmonary capillary wedge pressure and central venous pressure remained virtually unchanged in the two groups. Cardiac output was well maintained in PGE1 group, whereas cardiac output showed the tendency to decline in TMT group. Greater reduction in systemic vascular resistance was seen in PGE1 group than in TMT group. Pulmonary vascular resistance showed no significant change in PGE1 group, whereas it increased significantly in TMT group. Gradual decreases in arterial pH, PaO2 and base excess and slight but significant increase in PaCO2 was observed in PGE1 group, and these abnormalities recovered 30 min after hypotension. Abnormalities in blood gases and acid-base balance were considerably more severe and prolonged in TMT group compared with those in PGE1 group. Blood lactate and pyruvate concentrations showed no significant changes in PGE1 group, whereas substantial elevation was seen in L/P ratio especially 30 min after induction of hypotension in TMT group. Oxygen consumption showed minimal changes in PGE1 group, whereas a significant decrease was observed in TMT group. The conclusions derived from these results are as follows; 1) PGE1 maintained cardiac output better than TMT, probably because of its direct inotropic action on the heart, and of its greater reduction of systemic vascular resistance than TMT. 2) PGE1 seemed to provide the better blood perfusion throughout the body than TMT. 3) PGE1 showed less possibility to produce the metabolic derangement compared with TMT.

Opiate antagonist nalmefene inhibits ethanol-induced flushing in Asians: a preliminary study

Ethanol-induced flushing (EIF) occurs in up to 80% of Asians and is characterized by facial flushing, tachycardia, and increased cardiac output. Since endogenous opiates and prostaglandins may be mediators of flushing syndromes, we attempted to block EIF in four Asian flushers with single doses of either the opiate antagonist nalmefene, or the prostaglandin synthesis inhibitor indomethacin. Nonflushers (2 Caucasian, 2 Asian) and four Asian flushers were given on separate days water, ethanol (0.4 g/kg p.o.), ethanol plus nalmefene (2 mg i.v.), or ethanol plus indomethacin (50 mg p.o.). Ethanol concentrations of flushers and nonflushers were similar. Mean (+/- SEM) plasma acetaldehyde concentrations of flushers (28.2 +/- 11.8 microM) were significantly greater than nonflushers (1.4 +/- 0.5 microM) following ethanol ingestion (p less than 0.001). Ethanol alone always induced a significant rise in facial skin temperature [mean area under the curve (AUC) = 5142 +/- 648 % delta T x min, p less than 0.01] and of pulse (mean AUC = 1622 +/- 120 bpm x min, p less than 0.001) in flushers compared to water ingestion. A single dose of nalmefene (2 mg i.v.) but not indomethacin (50 mg p.o.), reduced the mean (+/- SEM) ethanol-induced rise in facial skin temperature of flushers by 58 +/- 14% (p less than 0.05) without changing plasma acetaldehyde concentrations. These data are preliminary evidence that the opiate antagonist, nalmefene, blocks some of the vascular manifestations of EIF without altering the elevated plasma concentrations of acetaldehyde.

Adverse effects of (15S)-15-methyl-prostaglandin E1 in normal and paraquat-exposed rats

Single, daily injections of approximately 1 mg/kg of (15S)-15-methyl-PGE1 (mPGE1), a PGE1 analog, have been reported to inhibit inflammation and to prolong survival in several animal models of local and systemic inflammation. We examined the effect of this dose of mPGE1 on paraquat toxicity in rats. A significant increase in early mortality was identified in mPGE1-treated rats as early as 3 hr following injection of paraquat and appeared associated with increased respiratory effort. Rats given mPGE1 without paraquat also appeared to increase respiratory effort but did not die. Rats killed at 3 hr following injections demonstrated increased lung weights in both paraquat-injected and control animals receiving mPGE1. Although a neutrophilia was identified in these animals, no significant increase in lung lavage neutrophils or albumin was identified. These data suggest that large intermittent doses of a PGE1 analog may adversely affect the respiratory system of normal and injured animals, and will accelerate mortality following exposure to potentially lethal doses of paraquat.

Cardiac and microcirculatory effects of different doses of prostaglandin E1 in man

A cumulative dose response to intravenous PGE1 was established in 12 healthy volunteers. Systolic time intervals, including pre-ejection period (PEP), the ventricular ejection time (VET) and the RR-interval, were continuously determined, and transcutaneous oxygen pressure (tcpO2) was recorded. RR-intervals fell in a dose dependent manner, reaching a significantly lower level at 128 ng.kg-1.min-1 of PGE1 (basal value 842 ms falling to 756 ms). PEP decreased from 89 ms to 74 ms and the ratio PEP/VET decreased from 35% to 30%, indicating increased myocardial contractility. The maximal increase in tcpO2 was 125% on the calf and 60% on the foot. The peak tcpO2 was observed at an infusion rate of 16 ng.kg-1.min-1 PGE1. A decline in tcpO2 was seen at infusion rates greater than 64 ng.kg-1.min-1 PGE1 indicating a decrease in skin perfusion. The results indicate that the effects of intravenous PGE1 on skin perfusion occur at a lower threshold than the increase in myocardial contractility. A maximal increase in skin perfusion can be achieved with doses of PGE1 devoid of systemic haemodynamic effects.

Effects of prostaglandins on the pulmonary vascular bed of newborn rats with chronic hypoxia

We investigated the effects of prostaglandins (PG) E1, I2 and D2 on the pulmonary vascular bed of newborn rats subjected to chronic hypoxia. Forty seven newborn rats were exposed to chronic hypoxia (10% oxygen) for 23 days and divided into five groups which received PGE1 (N = 10), PGI2 (N = 9), PGD2 (N = 11), placebo (N = 9) or served as controls (N = 8). The PG's were administered by implanting slow release subcutaneous pellets delivering an average daily dose of 1 microgram. Thirteen newborn rats in room air received either placebo or served as controls. All rats were killed after 23 days and heart-lung preparations were perfusion fixed with glutaraldehyde. Appropriate blocks were processed for quantitative morphometry of the pulmonary parenchyma, arteries and arterioles. For analysis the pulmonary vessels were grouped by external diameter, i.e. 30-50 mu and 50-100 mu. External diameter/lumen diameter, an index of medial smooth muscle mass, was 1.39 +/- 0.02 in room air controls, this index of medial muscle mass was significantly increased (p less than 0.01) to 1.53 +/- 0.03 in hypoxic controls and the PGD2 and PGI2 groups. However, the PGE1 group did not have medial hypertrophy evidenced by a medial muscle mass index of 1.34 +/- 0.04, similar to room air controls. These findings suggest that PGE1 may prevent the development of medial hypertrophy that occurs in chronic hypoxia.

The effect of intravenous prostaglandin E1 on ischaemic pain and on leg blood-flow in subjects with peripheral artery disease: a double-blind controlled study

The effect of intravenous PGE1 (15 micrograms/h for 72 h) and saline (placebo) on ischaemic resting pains and the macro- and microcirculation was studied in 16 patients with peripheral artery disease. No significant difference in pain relief was observed between PGE1 and placebo. The calf blood-flow was unchanged during both infusions. Skin temperature in the arteriosclerotic foot, however, increased significantly during PGE1 infusion but not during saline infusion. No significant effects were seen on blood-pressure, fluorescein angiography or vital capillary microscopy of the big toe 1 week or 1 month after the PGE1 and placebo infusions.

Antihypertensive activity and metabolic rate of prostaglandin E1 in surgical patients under general anesthesia

Plasma immunoreactive prostaglandin E (iPGE) levels during PGE1 infusion for controlling systemic blood pressure were investigated. Differences in systemic blood pressure changes between halothane-nitrous oxide-oxygen (GOF) anesthesia groups and a neuroleptanesthesia (NLA) group during infusion in hypertensive surgical patients were compared. Plasma iPGE concentration increased from 200 +/- 30 pg/ml to 408 +/- 55 pg/ml within 5 minutes at the beginning of PGE1 infusion. After the cessation of PGE1 infusion, iPGE levels quickly returned to pre-infusion levels, but blood pressure had not recovered to pre-infusion levels within 30 minutes. Blood pressure was well controlled with PGE1 infusion, but the pressure changes in GOF anesthesia group were significantly larger than those in the NLA group. The results suggest that the long anti-hypertensive action of PGE1 could be effective to control blood pressure in hypertensive surgical patients during and after surgery.

Prostaglandin E1 in suspected ductus dependent cardiac malformation

Fifty two sick neonates with major duct dependent cardiac defects were given short term intravenous infusions of prostaglandin E1 (alprostadil) in doses varying between 0.005 and 0.1 micrograms/kg/minute. The object of the study was to try to achieve an effective but safe regiment that could be instituted as soon as such a diagnosis was suspected. Effective clinical improvement was achieved at each dosage but the incidence of side effects seemed to be dose related, and no serious side effects were noted at a dosage of 0.005 to 0.01 micrograms/kg/minute. It is recommended that a low dosage regimen be started before transfer to a paediatric cardiac centre.

Haemorrheological effects of prostaglandin E1 infusion in Raynaud's syndrome

Eighteen patients with severe Raynaud's syndrome had impaired deformability of erythrocytes, as measured by filtration through 5 micron diameter pores, compared with 19 healthy controls. The patients were given prostaglandin E1 (PGE1) or placebo by intravenous infusion for 72 h to assess the haemorrheological action of PGE1. Contrary to a previous report, PGE1 did not improve erythrocyte filterability. Infusion of PGE1 did, however, evoke an acute phase response with hyperproteinaemia and a leucocytosis and is a potentially important mediator of this stress response in patients with vascular disease.

Comparison of the vasodepressor action of ZK 36 374, a stable prostacyclin derivative, PGI2 and PGE1 with their effect on platelet aggregation and bleeding time in rats

ZK 36 374, a new, chemically stable prostacyclin derivative, was compared with PGE1 and PGI2 with respect to its action on platelet aggregation in vitro, on bleeding time and on arterial blood pressure in conscious rats. The time of occlusion of a hole in a polyethylene (PE) tube of an AV-shunt between the left carotid artery and the right jugular vein by a microthrombus was considered as an index of bleeding time. All three substances inhibited the ADP-induced aggregation of human and rat platelets. In human PRP, ZK 36 374 was 17 times more active than PGE1 and 2 - 5 times as potent as PGI2. In contrast, in rat PRP, PGI2 was 9.2 and 3.4 times as potent as PGE1 and ZK 36 374, respectively. Similar differences in potency were found in the in vivo experiments where these substances given by an intravenous infusion to conscious rats prolonged bleeding time and depressed mean arterial pressure in a dose-dependent manner. ZK 36 374 was also orally active. At oral doses of 1, 2 and 3 mg/kg this new compound caused a dose-dependent prolongation of bleeding time and a fall in arterial blood pressure. In conclusion, the results show that ZK 36 374 is an intravenously and orally active prostacyclin derivative which may be of therapeutic value for occlusive peripheral vascular diseases.

Effects of indomethacin on central, renal and coronary hemodynamics. An experimental study in swine with unilateral ureteral obstruction

The circulatory effects of intravenously administered indomethacin, a potent prostaglandin synthesis inhibitor (0.8 mg/kg bw) were investigated in pigs with unilateral ureteral obstruction. The drug induced a marked but transient increase in systemic arterial pressure (+53%, p less than 0.02) and pulmonary arterial (+81%, p less than 0.02) pressure without any changes in left or right sided filling pressures, cardiac output or heart rate. Coronary blood flow remained unchanged and renal venous blood flow decreased (-26%, p less than 0.02). Renal pelvic pressure decreased (-20%, p less than 0.02). Thus systemic (SVR), pulmonary (PVR) and coronary vascular resistance (CVR) and renal vascular resistance (RVR) on the obstructed side increased (SVR + 73%, p less than 0.02; PVR + 140%, p less than 0.02; CVR + 53%, p less than 0.02 and RVR + 107%, p less than 0.02 respectively). Even if one takes into consideration other factors than ureteral obstruction contributing to these reactions, e.g. low volume load, anaesthesia, surgical trauma and species differences, care is advised in treating patients with coronary artery disease or obstructive lung disease with indomethacin.

Influence of parenteral prostaglandin E1 on lung mechanics in normal man

The effects of an infusion of prostaglandin E1 0.02 microgram/kg/min on lung mechanisms were studied in 10 healthy subjects. No change occurred in total lung volume and its subdivisions, airway resistance or maximal expiratory flow-volume curves. During the infusion, a slight but significant shift to the left of the static pressure-volume curve of the lung was observed, without any significant change in the upstream resistance (RUS), calculated at 70, 60 and 50% of total lung capacity. The loss of elastic recoil pressure without any variation in airway resistance or RUS, suggests that intravenous PGE1 selectively relaxes the contractile elements of the lung parenchyma, perhaps more by its action on the vascular wall than on the tone of the peripheral bronchiolar smooth muscle.

Prostaglandin E1 as a hypotensive drug during general anaesthesia

Hypotension induced by prostaglandin E1 (PGE1) infusion (100-150 ng/kg/minute) during halothane anaesthesia to reduce operative blood loss during mastectomy was investigated. PGE1 decreased systolic arterial pressure approximately 34% from pre-administration values. The duration of induced hypotension was about 75 minutes. When the infusion was stopped, blood pressure returned to within 15% of the control with 15 minutes. Heart rate did not change significantly during PGE1 infusion; the pre-ejection period and left ventricular ejection period were shortened. Renal function during the hypotensive period was well maintained. Blood loss during surgery was significantly decreased. These findings suggest that PGE1 can be used safely to control arterial pressure during surgery.

Comparison of effects of prostaglandin E1 and nitroprusside on pulmonary vascular resistance in children after open-heart surgery

Prostaglandin E1 (PGE1) is a vasodilator. Because the drug is metabolized by lung, we postulated a selective effect on pulmonary vasculature. Twenty-six patients aged 3 months to 16 year (mean, 6.5 years) were studied after repair of atrial septal defect (5), ventricular septal defect (10), tetralogy of Fallot (3), and other lesions (8). Fourteen patients also received nitroprusside. PGE1 (0.1 to 1.0 micrograms/kg/min) or nitroprusside (0.59 to 8.7 micrograms/kg/min) was infused through a central venous catheter until mean pulmonary or mean systemic arteria pressure decreases at least 10%. Prostaglandin E1 and nitroprusside both decreased mean systemic arterial pressure and systemic vascular resistance (P less than 0.05). Although both drugs caused an average decrease in pulmonary arterial pressure and resistance, nitroprusside produced a more consistent response. Side-effects limited the use of PGE1 in 5 patients. PGE1 is an effective vasodilator and has advantages for some patients, but it does not produce selective vasodilation of pulmonary vessels.

Prospects for nutritional control of hypertension

Sodium restriction is not the only nutritional measure likely to prove valuable in the treatment and prevention of hypertension. The hypotensive effects of central adrenergic stimulation can be promoted by supplementary tyrosine, insulin potentiation (as with GTF), and (possibly) high-dose pyridoxine. Insulin potentiators (GTF) and prostaglandin precursors (essential fatty acids) should have direct relaxant effects on vascular muscle. A high potassium, low sodium diet, coenzyme Q, and prevention of cadmium toxicity (as with dietary selenium) may act to offset renally-mediated pressor influences. Functional combinations of these measures might prove to be substantially effective, in which case they would offer considerable advantages over potentially toxic drug therapies.

Central and peripheral circulatory effects and metabolic effects of different prostaglandins given I.V. to man

Cardiac output, heart rate, stroke volume, pressures in the brachial artery, right ventricle and pulmonary artery, forearm blood flow, and arterial concentration of FFA, lactate and glucose were measured in healthy male volunteers during i-v infusion of PGE1, PGE2, PGF2 alpha or 15-methyl PGF2 alpha in increasing doses. In accordance with previous findings PGE1 and PGE2 increased cardiac output by a vasodilating effect in the systemic and pulmonary vascular bed, probably in combination with an inotropic effect on the heart. 15-methyl PGF2 alpha had essentially the same cardiovascular effects as PGF2 alpha. They induced a slight increase in cardiac output due to effects on heart rate, while systemic vascular resistance was unchanged. Forearm vascular resistance increased and pressures in the pulmonary circulation rose, indicating a vasoconstriction in these vascular beds. Glucose concentrations was not affected nor were lactate concentrations, except for a slight decrease of unclear significance in the group receiving 15-methyl PGF2 alpha. FFA increased slowly in the same manner as seen spontaneously in fasting individuals. These data do not indicate direct metabolic effects of the prostaglandins studied when given i-v.

A new concept of lifestyle-related cardiovascular disease: the importance of interactions between cholesterol, essential fatty acids, prostaglandin E1 and thromboxane A2

A proposal to account for the inter-relationships between established risk factors and cardiovascular disease is presented. In this concept, the critical substance is prostaglandin (PG) E1 which is a vasodilator, an inhibitor of platelet aggregation, an inhibitor of cholesterol and collagen biosynthesis and an inhibitor of smooth muscle proliferation. PGE1 biosynthesis is enhanced by the essential fatty acid, linoleic acid, by the platelet aggregating agent thromboxane (TX) A2, by cholesterol and by melatonin. These factors may participate in a negative feedback control loop. As a result of the operation of this loop, any tendency for PGE1 levels to fall is followed by increased cholesterol and TXA2 biosynthesis, and enhanced platelet aggregation, vasoconstriction, smooth muscle proliferation and collagen biosynthesis. Enhancement of PGE1 biosynthesis will have the opposite effects. Factors known to increase PGE1 biosynthesis include essential fatty acids, vitamin C, ethanol, pyridoxine, zinc and probably niacin, all of which are known to have some protective effects against cardiovascular disease. The hypothesis predicts that lowering of cholesterol biosynthesis by any method other than enhanced PGE1 formation, while reducing the risk of cardiovascular disease, will increase the risk of other disorders. The hypothesis suggest new approaches to treatment and new ways of combining existing treatments. Colchicine, which at low concentrations may imitate and action of melatonin, has particularly interesting possibilities. Colchicine and related compounds have already been shown to have potent cholesterol-lowering and anti-atherogenic actions in both humans and animals.