Effects of plasma on PGI2 release from prolonged perfused canine veins

Prostacyclin release from endothelial cells in culture appears increased by the presence of plasma, but occurrence of a similar phenomenon in intact vessels has not been established. In the present investigation release of 6-keto-PGF1 alpha, the stable breakdown product of prostacyclin, was quantitated from canine veins perfused ex vivo for 15 minute periods, using three different perfusates: 1) Hank's balanced salt solution (HBSS), 2) 20% platelet poor plasma (PPP) derived from heparinized blood, in HBSS, and 3) 20% PPP in HBSS with added arachidonic acid (AA). No differences in initial 6-keto-PGF1 alpha release existed among the three perfusates. However, PPP and PPP + AA solutions were associated with lesser declines in release, than occurred with HBSS alone, these differences being statistically significant after 60 min of perfusion (p less than 0.05). When PPP derived from heparinized and citrated blood rather than from only heparinized blood was used, there was a significantly lower release of prostacyclin (p less than 0.05). The latter may be due to citrate binding of calcium. These data indicate that autologous plasma does not alter initial prostacyclin release from freshly harvested canine veins, but that it weakens the decline in release usually following prolonged periods of perfusion.

Small-caliber polyurethane and polytetrafluoroethylene grafts: a comparative study in a canine aortoiliac model

In vivo stability of a new small-caliber polyurethane graft (n8) was assessed in a canine aortoiliac model and compared to that of a conventional expanded polytetrafluoroethylene (ePTFE) graft (n8). Six months following implantation, marked aneurysmal dilatation to 230 +/- 80% (mean +/- SD) of the original diameter occurred in polyurethane grafts, while dilatation to 110 +/- 8% of the original diameter occurred in ePTFE grafts (p less than 0.005). Interval patency was 75% for each graft type. Luminal thrombus affected 59% of polyurethane graft surfaces compared to 22% of ePTFE graft surfaces (p less than 0.01). Qualitative examination of representative sections of polyurethane conduits demonstrated thick inner capsules with numerous small islands of graft material surrounded by macrophages and bands of mature fibrous tissue, in contrast to the thinner neointima and limited anastomotic pannus ingrowth observed in ePTFE grafts.

Artery, periarterial adipose tissue, and blood microbiology during vascular reconstructive surgery: perioperative and early postoperative observations

The presence and clinical significance of bacteria in the arterial wall, periarterial adipose tissue, and blood samples acquired during elective vascular operations were assessed in this study. Specimens were obtained from a random series of 84 patients (56 men, 28 women) undergoing 75 primary and 9 secondary arterial reconstructions. Operations performed most frequently included abdominal aortic aneurysmectomy (42), aortofemoral bypass reconstruction (15), and lower extremity bypass surgery for occlusive disease (7). Perioperative antibiotics were administered to all but one patient. A sample of artery, adjacent adipose tissue, and blood were obtained for microbial analysis during the vascular anastomosis or arteriotomy. This yielded a total of 152 artery, 139 adipose tissue, and 129 blood samples for study. Each specimen was divided and placed in blood agar plates, thioglycolate broth, and brain-heart infusion broth. Tissues yielding growth of the same organism(s) in two or more different media were considered positive for the presence of bacteria. Bacteria were present in at least one of the three tissues studied in 32/84 patients (38%). The frequency of positive cultures in primary (29/75, 39%) and secondary procedures (3/9, 33%) were similar. One positive culture site occurred in 26/32 (81%) patients, two positive culture sites existed in 5/32 (16%) patients, and three positive sites were found in 1/22 (3%) patients. Eighteen individual artery (18/152, 12%) and 19 adipose tissue samples (19/139, 14%) harbored bacteria, whereas only two blood cultures were positive (2/129, 2%). Organisms identified included coagulase-negative staphylococci (71%), gamma-streptococci (7%), diphtheroids (7%), Micrococcus (5%), alpha-streptococci (5%), Staphylococcus aureus (2%), and Pseudomonas picketti (2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Reversal of depressed oxygen consumption accompanying in vivo protamine sulphate-heparin interactions by the prostacyclin analogue, iloprost

Oxygen consumption (VO2) is known to be depressed 50 to 60% during protamine sulphate reversal of heparin anticoagulation. Accompanying this event are systemic hypotension, pulmonary artery hypertension and thrombocytopaenia. The effect of a pro-stacyclin analogue, iloprost, on protamine-induced changes in VO2 was assessed in this investigation. Three groups of anaesthetised adult mongrel dogs were studied: Group I--control subjects received i.v. normal saline infusions (n = 10); Group II--subjects received low-dose i.v. iloprost infusions (25-50 ng/kg/min) over 30 min (n = 7); and Group III--subjects received high-dose i.v. iloprost infusions (175 ng/kg/min) over 30 min (n = 7). All dogs initially received sodium heparin, 150 IU/kg i.v. Protamine sulphate, 1.5 mg/kg i.v., was subsequently administered over 10 s following the first 20 min of saline or iloprost infusion. Continuous measurements included: mixed venous (SvO2) and arterial (SaO2) oxygen saturation, arterial blood pressure, pulmonary artery pressure, heart rate and carotid artery flow (CaQ). Thermodilution cardiac output (CO) allowed calculation of VO2. Platelet counts were performed before and 3 min after protamine infusion. The VO2 declines in Group II and III subjects compared to Group I controls were markedly less. Maximum VO2 declines in Group I control dogs of -38.2 +/- 26.7% and Group II dogs of -34.1 +/- 36.8% at 75 to 90 s post-reversal contrasted to -2.9 +/- 31.9% in Group III animals at the same time interval. VO2 increases occurred 3 to 10 min after protamine exposure in Group III animals, as did attenuation of systemic hypotensive and pulmonary hypertensive responses in this group.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative potency of pipecuronium bromide and pancuronium bromide

Cumulative dose-response curves were constructed to determine the comparative potency of pipecuronium and pancuronium. From these, the ED50 and ED95 values were calculated. These were 24.96 micrograms kg-1 and 44.96 micrograms kg-1, respectively, for pipecuronium and 30.42 micrograms kg-1 and 61.12 micrograms kg-1, respectively, for pancuronium.

Prostanoid release from ex vivo perfused canine arteries and veins: effects of prolonged perfusion, intermittent perfusion, as well as exposure to exogenous arachidonic acid, thrombin and bradykinin

Regulation of prostanoid release from ex vivo perfused vessel segments is not fully understood. A series of perfusion experiments were performed with canine arteries and veins to define certain regulatory phenomena. Arteries were perfused with pulsatile flow of 90 ml/min at a pressure of 100 mmHg, and veins with nonpulsatile flow of 90 ml/min at a pressure of 7 mmHg. Segments were perfused with Hanks' balanced salt solution for five 15-min periods with the perfusate exchanged after each study period. With onset of perfusion, there was an initial burst of prostacyclin release to 127 +/- 40 pg/mm2, declining to 32 +/- 10 pg/mm2 after 60 minutes (p less than 0.005). If perfusion continued for 5.5 hours, there was a stable release period between 1 and 3 hours, followed by a very slow decline. At that time addition of arachidonic acid (AA) increased prostacyclin release six-fold (p less than 0.01). Vessels perfused for 1 hour and then rested for another hour, responded to reperfusion at the second onset of flow with a two-fold increase in prostacyclin release (p less than 0.01). Vessels perfused with thrombin, bradykinin or AA (either added to each perfusate or only to the last perfusate) exhibited greater prostacyclin release than did control segments. Release of thromboxane steadily declined with time in all parts of the study, and only increased with the addition of AA to the perfusate.(ABSTRACT TRUNCATED AT 250 WORDS)

A prospective study of clinically and endoscopically documented colonic ischemia in 100 patients undergoing aortic reconstructive surgery with aggressive colonic and direct pelvic revascularization, compared with historic controls

Clinically and endoscopically proved ischemia of the colon complicates elective aortic reconstruction in 1% to 2% and 6% to 7% of cases, respectively. Operative mortality exceeds 60% when transmural infarction occurs. A prospective study of colonic ischemia was undertaken in 100 male patients (mean age, 62.4 +/- 7.9 years) undergoing operation for aortic aneurysms (58) or aortoiliac occlusive disease (42). Conventional aortic surgery was undertaken in 88 patients, and in 12 patients adjunctive procedures to enhance colonic perfusion were performed 14 times, including IMA reimplantation (8), direct bypass to the internal iliac artery (4), and anastomosis of an aortofemoral bypass limb to adjacent common iliac artery (2). Colonoscopy was performed within 24 to 48 hours of aortic reconstruction. Three patients had endoscopic evidence of colonic ischemia. Transmural infarction did not develop in any patient, and bowel resections or diverting colostomies were not necessary. Three patients died, none manifesting colonic ischemia. The 12% utilization of adjunctive procedures to enhance blood flow in the colon was substantially greater than the 4% frequency of an earlier experience from our institution in which nearly half of the 5.7% operative mortality was attributed to colonic infarction. Attention to factors contributing to ischemia of the colon, and more frequent adjunctive revascularization of the colon, may lessen this complication of aortic reconstructive surgery.

Chronic gastric ischemia. A cause of abdominal pain or bleeding identified from the presence of gastric mucosal acidosis

Acidosis in gastric mucosa (pHi less than 7.32) was evaluated as a diagnostic test for gastric ischemia, using 80 asymptomatic subjects as controls. Mucosal acidosis was found in 6 patients with abdominal pain and 1 with gastrointestinal bleeding. Three had occlusive disease of 2 or more visceral arteries, 3 had occlusive disease of the celiac axis alone, and 1 had an occluded portal vein. One patient had infarcted gut. The abnormal pHi (7.10 +/- 0.11, mean +/- SD) in those with pain was returned to normal levels (7.43 +/- 0.08, p = 0.0003) and the symptoms relieved by revascularization. The abnormal pHi (6.84 +/- .04) in the patient who bled was restored to normal levels (7.48 +/- .03, t = 9.69, p less than .0001) and the bleeding stopped by a central splenorenal shunt. Measurements of pHi in gastrointestinal mucosa may be used as an objective test for evaluating patients suspected of having chronic gastrointestinal ischemia.

Protamine-induced reductions of endothelial cell ATP

Protamine, a polycationic protein used to reverse heparin anticoagulation, is frequently associated with decreased oxygen consumption, systemic hypotension, pulmonary artery hypertension, and bradycardia. This investigation examines the hypothesis that these events reflect toxic effects of protamine on endothelial cells. Cultured bovine pulmonary artery endothelium was exposed to protamine (12.5 to 500 micrograms/ml, corresponding to clinical doses 0.75 to 30 mg/kg), either alone (n = 6) or 3 minutes after exposure to heparin, 0.1 IU/microgram protamine (n = 6). ATP was measured 1 to 180 minutes after protamine by a luciferase-luciferin assay and cell viability determined by trypan blue exclusion. Ultrastructure was assessed by transmission electron microscopy. Polylysine, 25 micrograms/ml, a cytotoxic polycationic agent, was also studied. Dose-dependent reductions in ATP (range, -11% to -51%) and ATP per viable cell (up to -41%) occurred. Decreases in ATP did not occur until after 30 minutes with protamine alone, compared with differences as early as 1 minute after protamine with prior heparin. Progressive mitochondrial injury was noted evident by swollen cristae, vacuolization, and eventual disruption. Polylysine caused similar changes. Protamine decreases endothelial cell ATP and prior heparin exposure accelerates this effect. The toxicity may reside in the positive charges on these molecules and mitochondrial damage may account for reductions in cellular ATP and systemic oxygen consumption.

Effects of duration of acetylsalicylic acid administration on patency and anastomotic hyperplasia of ePTFE grafts

Effects of duration of acetylsalicylic acid (ASA) administration on the patency and development of distal anastomotic intimal hyperplasia (DAIH) of endothelial cell (EC) seeded and unseeded prosthetic aortoiliac grafts were studied in a canine model. ASA, 5 gr po qd, was administered to dogs 1 day prior to placement of bilateral, 12 to 17 cm long, 5 mm inside diameter expanded polytetrafluoroethylene (ePTFE) aortoiliac grafts and continued for 2 wk (Group 1, n = 12 dogs) or 16 wk (Group 2, n = 12 dogs). Six dogs in each group received autologous EC seeded grafts, while the others received unseeded grafts. Prosthesis patency was assessed weekly. At the conclusion of the study, DAIH was measured on serial sections using a computer-linked digitizer. The 16 wk patency for Group 1 grafts was 67%, while that for Group 2 grafts was 88% (p less than 0.09). Luminal narrowing due to DAIH was not significantly different between Groups 1 and 2 (7.7 +/- 8.3% [means +/- SD] and 9.0 +/- 7.8% respectively). EC seeding improved the 16 wk combined patency from 62 to 92% (p less than 0.02). A more complete luminal endothelial cell lining was correlated with reduced DAIH (r = -0.4, p less than 0.05). Chronic ASA administration prevented graft thrombosis between 2 and 4 wk postimplantation in this study but was not associated with decreased DAIH.

Recombinant gene expression in vivo within endothelial cells of the arterial wall

A technique for the transfer of endothelial cells and expression of recombinant genes in vivo could allow the introduction of proteins of therapeutic value in the management of cardiovascular diseases. Porcine endothelial cells expressing recombinant beta-galactosidase from a murine amphotropic retroviral vector were introduced with a catheter into denuded iliofemoral arteries of syngeneic animals. Arterial segments explanted 2 to 4 weeks later contained endothelial cells expressing beta-galactosidase, an indication that they were successfully implanted on the vessel wall.

Decreased oxygen consumption as a toxic manifestation of protamine sulfate reversal of heparin anticoagulation

Protamine sulfate has been observed to interfere with the control of isolated mitochondrial respiration in vitro. This study was designed to determine if oxygen consumption changes in intact animals occur in vivo during protamine administration. Oxygen consumption was assessed in seven dogs anticoagulated with heparin (150 IU/kg) and reversed 30 minutes later with protamine sulfate (1.5 mg/kg). Oxygen saturations measured included arterial (SaO2 arterial), mixed venous (SvO2 systemic), jugular (SvO2 jugular), portal (SvO2 portal), and coronary (SvO2 coronary). Cardiac output (CO) and carotid artery flow determinations allowed calculation of systemic oxygen consumption (VO2 systemic) and cerebral oxygen consumption VO2 cerebral. Hemodynamic measurements included arterial blood pressure (BP), pulmonary artery systolic and diastolic pressures (PAS, PAD), and heart rate (HR). Protamine sulfate administration resulted in hypotension (delta BP -64 mm Hg), pulmonary hypertension (delta PAS + 13 mm Hg, delta PAD + 11 mm Hg), and bradycardia (delta HR -30). Shortly after protamine administration, CO fell 54% and carotid artery flow fell more than 50%, yet declines in SvO2 systemic and SvO2 jugular were not observed. In fact these parameters increased 3% and 2%, respectively. VO2 systemic fell 55% and VO2 cerebral fell 57%. Similarly, SvO2 portal and SvO2 coronary increased 6% and 9%, respectively. Significant correlations existed between changes in VO2 systemic and BP (r = 0.05, p less than 0.001), HR (r = 0.3, p less than 0.01, PAD (r = -0.3, p less than 0.05, and CO (r = 0.8, p less than 0.001). Impaired oxygen utilization was most evident during the first 5 minutes after protamine administration. This investigation, for the first time, establishes that protamine sulfate decreases in vivo oxygen consumption, a finding that may account for certain of the drug's adverse side effects.

Effect of preexcisional heparin anticoagulation on excised canine vein and artery prostanoid production

The effect of heparin, administered prior to vessel dissection and excision, on the luminal release of prostanoids from an excised vessel was assessed. Eight adult mongrel dogs underwent removal of the jugular vein and carotid artery on one side, followed by intravenous administration of heparin sodium (150 IU/kg) and subsequent removal of these same vessels from the contralateral neck. The excised vessels were perfused in an ex vivo system with Hanks' balanced salt solution for five consecutive 15-min periods. Prostacyclin release (measured as 6-keto-PGF1 alpha) and thromboxane A2 (measured as thromboxane B2) release into the perfusate were quantitated by radioimmunoassay. Vessel segments were studied with and without first period thrombin stimulation (2 U/ml) and with arachidonic acid (4 micrograms/ml) stimulation during the last perfusion period. Vein segments following heparin administration exhibited greater prostacyclin production than veins not exposed to heparin. This effect did not occur in arteries. Heparin did not influence thromboxane A2 release. Luminal endothelial cell coverage was not affected by the presence or absence of heparin. Thus heparin anticoagulation prior to dissection and excision of a vein, may enhance early preservation of its endothelial cell function as evident by increased luminal release of prostacyclin.

Arterial 6-keto-PGF1 alpha and TxB2 release in ex vivo perfused canine vessels: effects of pulserate, pulsatility, altered pressure and flow rate

Certain experimental conditions are known to influence the release of prostacyclin and thromboxane from the vessel wall. The specific effects of altered pulsatility, pressure, and flow rate on intraluminal release of 6-keto-PGF1 alpha and thromboxane B2 were assessed in canine arteries perfused ex vivo for five 15 min periods with arachidonic acid (AA) added during the last period. Control arteries were perfused at 100 mmHg with pulsatile flow of 90 ml/min. Experimental arteries were perfused at 7, 50 and 200 mmHg with pulsatile flow of 90 ml/min, and at 100 mmHg pressure with pulsatile flow of 20, 60, 130 and 180 ml/min, as well as at 100 mmHg with 90 ml/min nonpulsatile flow. Perfusion pump rates of 44 and 96 beats/min were also assessed. The lowest perfusion pressure, 7 mmHg, resulted in a lesser initial release of prostacyclin compared to higher pressures, and there was a tendency to a higher release of prostacyclin with increasing pressures. There was also a tendency for a lesser response to AA in arteries perfused at 200 mmHg, perhaps due to endothelial cell damage. Nonpulsatile flow was associated with a decreased initial release of prostacyclin, and diminished release following addition of AA when compared to pulsatile flow. Altered flow rate elicited no difference in prostacyclin release, although there was a tendency towards a lesser release when perfused at 20 ml/min compared to 130 ml/min or 180 ml/min. Thromboxane release was decreased by nonpulsatile flow but was otherwise unaffected by the experimental conditions tested. It is concluded that pulsatility enhances release of prostacyclin from arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of thromboxane synthetase inhibition on patency and anastomotic hyperplasia of vascular grafts

The efficacy of a thromboxane synthetase inhibitor (U-63,557A, Upjohn) in promoting early patency and inhibiting anastomotic intimal hyperplasia in ePTFE grafts was compared to that of acetylsalicylic acid (ASA) in a canine model. Animals were started on ASA 5 gr po qd (Group I, n = 12) or U-63,557A 10 mg/kg po bid (Group II, n = 12) 1 day before placement of bilateral 5-mm-i.d., 13- to 16.5-cm-long ePTFE aortoiliac grafts and continued on the medication for the 16-week study. Six dogs in each group received autologous endothelial cell-seeded grafts, while the other six received unseeded grafts. Patency was determined weekly by assessment of femoral pulses. At the conclusion of the study anastomotic intimal hyperplasia was measured on serial sections through the distal anastomosis using a computer-linked digitizer. In Group I the patencies of seeded and unseeded grafts were not significantly different, being 100 and 83%, respectively. Furthermore, luminal narrowing due to intimal hyperplasia was not significantly different being 9.1 +/- 7.6% (chi +/- SD) in seeded grafts and 8.8 +/- 8.1% in unseeded grafts. On the other hand, in Group II the seeded grafts had significantly improved patency when compared to the unseeded grafts (83% vs 33%, P less than 0.05) and less luminal narrowing (11.4 +/- 11.1% vs 21.9 +/- 19.5%, P less than 0.01). Although U-63,557A administration promoted patency of unseeded grafts compared to no antiplatelet medication (0% patency), it was significantly less effective than ASA in improving patency (P less than 0.05) and inhibiting luminal narrowing (P less than 0.01).

Platelet reactivity in human aortic grafts: a prospective, randomized midterm study of platelet adherence and release products in Dacron and polytetrafluoroethylene conduits

Platelet-related phenomena at the blood-surface interface of randomly placed knitted Dacron (n = 6) and polytetrafluoroethylene (ePTFE) (n = 6) interposition aortic grafts were studied in patients undergoing abdominal aortic aneurysmectomy. Luminal accumulation of platelets was assessed by infusing indium-111-oxine (400 microCi) labeled autologous platelets and imaging grafts at 1 week, 3 months, and 6 months after surgery. Image analysis included an indium ratio technique (comparing aortic graft radioactivity to that of an iliac artery) and a red blood cell technetium subtraction technique (excluding blood pool radioactivity from graft radioactivity, with the heart or iliac artery serving as reference regions). Plasma levels of beta-thromboglobulin and platelet factor 4 were correlated with platelet accumulations on the aortic prostheses. Differences in graft radioactivity or platelet-release products were not evident 1 week after surgery. Three months after implantation, Dacron and ePTFE conduits exhibited 87% and 47% (p less than 0.05) more radioactivity with the indium ratio technique than the iliac artery. Similarly, increased Dacron compared with ePTFE graft radioactivity was noted using technetium subtraction techniques: 71% vs 30% with a heart reference and 26% vs 11% with an iliac artery reference, respectively. Increases in graft radioactivity correlated with increases in both plasma beta-thromboglobulin and platelet factor 4 at 3 months (r = 0.6 to 0.9; p less than 0.05 to 0.001 depending on the imaging technique used). At 6 months, differences did not persist. In fact, technetium subtraction techniques suggested less Dacron conduit reactivity. It is speculated that differences in platelet accumulation and activation associated with different graft substrates may prove clinically important.

Complement depletion and persistent hemodynamic-hematologic responses in protamine-heparin reactions

Hypotension, bradycardia, pulmonary artery hypertension, neutropenia, and thrombocytopenia have been suspected to be due to complement activation following protamine reversal of heparin. This investigation examined these phenomena in complement-depleted animals. Eight dogs received intraperitoneal naja n. naja cobra venom factor (CVF), 20 U/kg, 48 and 24 hr prior to anticoagulation with sodium heparin, 150 IU/kg, and reversal 30 min later with protamine sulfate, 1.5 mg/kg. Decomplementation was confirmed in all dogs. Systemic blood pressure (BP), pulse (HR), pulmonary artery systolic and diastolic pressures, (PAS, PAD), cardiac output (CO), platelet count (PTC), and white blood count (WBC) with differential were monitored. The maximal mean changes for the entire group were BP, -43 mm Hg; HR, -16; PAS, +6 mm Hg; PAD, +3 mm Hg; CO, -27%; PTC, -49%; and WBC, -48%. These hemodynamic and hematologic responses, occurring in the face of CVF-induced decomplementation, support the conclusion that complement components C3 and C5-C9 are not influential factors contributing to these protamine-heparin-induced events.

Anticoagulant effects of protamine sulfate in a canine model

Protamine sulfate is considered a weak anticoagulant, yet little is known concerning the mechanism of this effect or its relation to prior heparin exposure. This investigation defined the influence of increasing doses of protamine, with and without prior heparin anticoagulation, on the activated clotting time (ACT), thrombin clotting time (TCT), prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen level, platelet count, and platelet aggregation to ADP in dogs (n = 8). Four doses of intravenous protamine sulfate (1.5, 3.0, 6.0, and 15.0 mg/kg) were studied in each animal, with at least 5 days between individual studies. Four dogs received heparin, 150 IU/kg 10 min prior to protamine sulfate administration, and four dogs received protamine sulfate alone. Protamine sulfate caused anticoagulation, both in the presence and absence of heparin, with significant changes occurring in the ACT, PTT, platelet count, and platelet aggregation. Relevant changes did not occur in the TCT, PT, or fibrinogen levels. Platelet effects were capable of causing bleeding with standard or excess use of protamine sulfate, especially if platelet numbers were already decreased, as might occur in surgical procedures where thrombocytopenia commonly accompanies major blood loss and replacement. The ACT, reflecting both the coagulation cascade and platelet function, was the test most profoundly affected by protamine overdosage, and therefore may be misleading as a measure of protamine reversal of heparin. The TCT, which is sensitive to heparin anticoagulation but not protamine-induced anticoagulation, should be more accurate in differentiating inadequate heparin reversal from the effects of excess protamine.

Comparison of static incubation versus physiologic perfusion techniques for quantitation of luminal release of prostacyclin and thromboxane in canine arteries and veins

Intraluminal release of 6-keto-PGF1 alpha and TxB2 in ex vivo canine arteries and veins was assessed during five consecutive 15-min periods using static incubation and physiologic perfusion techniques. Arterial segments were perfused with 90 ml/min pulsatile flow at 100 mm Hg and vein segments with 90 ml/min nonpulsatile flow at 7 mm Hg. During the final 15-min period vessels were stimulated with arachidonic acid (AAS). Perfusion of vein segments caused a higher release of 6-keto-PGF1 alpha during the first 30 min (P less than 0.05) and following AAS (P less than 0.05) than did static incubation. Perfused arterial segments exhibited a higher release than did incubated segments of 6-keto-PGF1 alpha for 45 min (P less than 0.01) as well as following AAS (P less than 0.01). TxB2 release was higher during the entire observation period in perfused arteries and veins compared to incubated vessels (P less than 0.01 and less than 0.05, respectively). There was no correlation between the amounts of 6-keto-PGF1 alpha or TxB2 released when comparing values obtained by one technique to values obtained by the other (P greater than 0.1). These data suggest that flow related shear stress alters vascular prostanoid production, and that such should be accounted for when interpreting results of studies on prostacyclin and thromboxane release from intact vessels.

Endothelial cell seeding of expanded polytetrafluoroethylene vena cava conduits: effects on luminal production of prostacyclin, platelet adherence, and fibrinogen accumulation

The blood-surface interface of 12 mm ID x 5 cm ePTFE vena cava conduits, unseeded (n = 8) and seeded (n = 8) with enzymatically derived autologous endothelial cells, was studied in a canine model at 4 and 12 weeks after graft implantation. Acetylsalicylic acid (325 mg each day) and Coumadin (prothrombin time 1.4 to 1.7 times the control value) were administered preoperatively and continued 4 weeks postoperatively. Platelets labeled with 111In and 125I-labeled fibrinogen were administered 24 hours before graft removal. Luminal platelet adherence, expressed as 10(6) platelets/cm2 of graft surface, was 8.9 +/- 5.6 vs. 56.4 +/- 8.0 (p less than 0.008) and 4.0 +/- 0.9 vs. 12.4 +/- 2.3 (p less than 0.005) in seeded vs. unseeded grafts at 4 and 12 weeks, respectively. Luminal fibrinogen deposition, expressed in micrograms per square centimeter of graft surface, was 11.8 +/- 2.2 vs. 32.0 +/- 2.0 (p less than 0.06) and 6.1 +/- 2.4 vs. 12.4 +/- 6.3 (p less than 0.005) in seeded vs. unseeded grafts at 4 and 12 weeks, respectively. Cumulative 4- and 12-week luminal production of 6-keto-PGF1 alpha from seeded and unseeded grafts represented 11% and 5%, respectively, of that produced from the native iliac vein. Luminal endothelial cell coverage was 71% +/- 22% vs. 33% +/- 9% and 79% +/- 8% vs. 55% +/- 8% (p less than 0.05) in seeded and unseeded grafts at 4 and 12 weeks, respectively. Although endothelialization was not complete in seeded vena cava grafts, it is clear that seeded prostheses exhibited improved thromboresistance compared with unseeded conduits.

Lack of effect of dihydroergotamine on endothelial and smooth muscle cell proliferation and endothelial cell prostanoid production

The most important effect of dihydroergotamine is venoconstriction, but certain metabolic effects and changes in vessel prostanoid activity have also been suggested. In this study endothelial cell production of 6-keto PGF1 alpha and TxB2 was quantitated in vitro. No evidence of altered prostanoid production was noted after incubation with dihydroergotamine (exposure ranging from 5 x 10(-3) to 5 x 10(-7) g/l). Similarly, no effect of dihydroergotamine on the growth rates of endothelial cells or smooth muscle cells in vitro was documented.

The effect of protamine sulfate on platelet function

The adverse effects of protamine sulfate, used to neutralize the anticoagulant action of heparin, include systemic hypotension, pulmonary artery hypertension, thrombocytopenia and leukopenia. For further evaluation of protamine's mechanism of action, a three-part investigation was performed. In part I platelet-rich plasma (PRP) was prepared from canine blood samples (n = 6) taken before and 2 minutes after injection of protamine. In part II human PRP (n = 5) was preincubated with protamine or distilled water. Adenosine diphosphate-induced aggregation of protamine-treated platelets was unchanged, but thrombin-induced aggregation was inhibited in both canine and human preparations (p less than 0.05). In part III thrombocytopenia was produced in splenectomized dogs (n = 5), using microporous filters, to 4.5-8.4% of the initial platelet count. Protamine reversal of the heparinization caused hypotension (maximally -29 mmHg 90 s after protamine), but not pulmonary arterial hypertension. Leukopenia developed before additional thrombocytopenia appeared. Protamine-platelet interaction inhibits thrombin-induced platelet aggregation. Platelets may play an important role in the pulmonary pressure rise during protamine reversal, but do not mediate the systemic hypotension.