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Biomedical subjects

M B Freeman

Publications and source records attributed to M B Freeman.

At least 37 records · Page 2Linked to original sources
PubMed1997

Concomitant orthopedic and vascular injuries as predictors for limb loss in blunt lower extremity trauma.

Lower extremity trauma with concomitant orthopedic and vascular injury is associated with a high degree of limb loss. Despite successful arterial repair, many patients will ultimately require amputations. The effect of associated orthopedic injuries on limb loss in patients with lower extremity arterial injuries is investigated. From 1989 to 1994, 52 infrainguinal arterial injuries were identified among 365 vascular trauma patients. Clinical determinants were retrospectively assessed for the ability to predict postoperative amputations. Femoral artery injuries were present in 23 patients, with 53 per cent the result of blunt trauma. The incidence of lower extremity fractures was 53 per cent (60% open). Seventy-nine per cent of femoral artery injuries were repaired with saphenous vein grafts. Popliteal artery injuries were present in 13 patients, with 77 per cent the result of blunt trauma. The incidence of lower extremity fractures and posterior knee dislocations was 85 per cent (73% open) and 38 per cent, respectively. Ninety-two per cent of injuries were repaired with saphenous vein grafts. Tibial artery injuries were present in 16 patients, with 44 per cent the result of blunt trauma. The incidence of lower extremity fractures was 81 per cent (46% open). Twenty-five per cent of tibial artery injuries were treated with arterial repair, and 31 per cent with arterial ligation. Fourteen above-knee (AKA) and two below-knee amputations were performed. Amputation rates were 26.1 per cent (three AKAs) for femoral, 53.8 per cent (seven AKAs) for popliteal, and 38 per cent (four AKAs, two below-knee amputations) for tibial artery injuries. At the popliteal and femoral locations, greater than two long-bone fractures was predictive of amputation. For tibial arteries, one-vessel (n = 10), two-vessel (n = 3), and three-vessel (n = 3) injuries were associated with 20, 33, and 100 per cent amputations rates, respectively. Blunt injury, pulseless extremity, need for arterial repair (rather than ligation or no therapy), increasing number of injured tibial vessels, and multiple long-bone fractures were predictors of amputation (P < 0.05). Distal vascular injuries combined with complex orthopedic fractures are more likely to result in limb loss. Two or more long-bone fractures is predictive of amputation at all three locations.

Amputation, Surgical↗
PubMed1997

The role of platelet-derived growth factor in intraluminal stented graft healing.

BACKGROUND: Intraluminally placed polytetrafluoroethylene grafts are associated with enhanced graft endothelialization and diminished intimal hyperplasia when compared with interposition grafts. This study determined the role of platelet-derived growth factor in intraluminal graft healing. STUDY DESIGN: Thirty dogs underwent infrarenal abdominal aorta polytetrafluoroethylene interposition (control, n = 15) or intraluminal stented (n = 15) grafting. Grafts were explanted at 1, 3, and 6 weeks. The percent of graft area endothelialization and intima to media height ratios were calculated. By using protein electrophoresis and the Western blot technique, platelet-derived growth factor, identified by immunolabeling with anti-platelet-derived growth factor antibody, was isolated from proximal, mid-, and distal graft regions and was quantified using densitometry. RESULTS: Graft area endothelialization was 0 +/- 3.3 percent, 2.3 +/- 3.3 percent, and 19.0 +/- 3.3 percent for 1-, 3-, and 6-week controls; and 4.7 +/- 3.7 percent, 30.5 +/- 3.3 percent, and 86.8 +/- 3.3 percent for 1-, 3-, and 6-week stented grafts. Endothelialization was greater in stented grafts at 3 and 6 weeks (p < .01). Proximal anastomosis intima to media height ratios were 1.61 +/- 0.15, 1.54 +/- 0.14, and 1.48 +/- 0.15 for 1-, 3-, and 6-week control grafts, and 0.42 +/- 0.18, 0.41 +/- 0.15, and 0.47 +/- 0.14 for 1-, 3-, and 6-week stented grafts. Similar intima to media height ratio values were present at the distal anastomosis. Lower intima to media height ratios were observed in all stented grafts (p < .01). The platelet-derived growth factor content at 1-, 3-, and 6-weeks was lower in all stented grafts when compared with controls. The content of platelet-derived growth factor was greatest in 3-week controls, with a significant difference noted in the mid-graft region (p < .05). The content of platelet-derived growth factor remained stable in all stented graft regions over 6 weeks. An inverse correlation between stented graft platelet-derived growth factor content and endothelialization (r = -0.43) and a positive correlation with proximal anastomotic intimal hyperplasia (r = 0.73) were identified. CONCLUSIONS: Lower platelet-derived growth factor content is associated with decreased intimal hyperplasia and improved healing in intra-arterial polytetrafluoroethylene grafts.

Animals↗
PubMed1997

Predictors of survival after inferior vena cava injuries.

In patients with inferior vena cava (IVC) injuries, predictors of survival are investigated. From 1987 to 1995, 27 IVC injuries were identified among 514 patients with vascular trauma. The ability of clinical determinants to predict survival were retrospectively assessed. IVC injuries occurred in 7 females and 20 males (mean age, 27.7 +/- 2.5 years) from both blunt (n = 14) and penetrating (n = 13) trauma. The mean revised trauma score was 10.2 +/- 0.6. Injuries were treated by primary repair (n = 22), ligation (n = 4), or prosthetic grafting (n = 1). Thirteen patients died (48%), 10 within 12 hours of admission. Suprahepatic (n = 2), retrohepatic (n = 12), suprarenal (n = 1), and infrarenal (n = 12) injuries were associated with 100, 67, 100, and 20 per cent mortality, respectively. Blood transfusions (16 +/- 4 vs 23 +/- 4 units), coagulation factor replacement (7 +/- 2 vs 7 +/- 2 units), and electrolyte solution use (8.6 +/- 1.4 vs 9.6 +/- 1.4 L) were similar among survivors and nonsurvivors. Four complications [venous hypertension (n = 2), IVC thrombosis (n = 1), and pulmonary embolus (n = 1)] occurred in the 14 survivors (28.6%). Blunt injury, revised trauma score, free perforation, injury location, intraoperative hypotension, and blood loss were predictive of mortality. IVC injuries remain extremely lethal, and improved survival is associated with infrarenal penetrating injuries and a contained hematoma.

Adult↗
PubMed1996

Effect of endoluminal PTFE graft placement on cell proliferation, PDGF secretion, and intimal hyperplasia.

To determine the effects of intraluminal placement on peri-anastomotic intimal hyperplasia and platelet derived growth factor (PDGF) secretion in polytetrafluoroethylene (PTFE) grafts. Infrarenal aortic PTFE grafts were placed in 30 dogs as either interposition (n = 12) or intraluminal stented (n = 18) grafts. Grafts were explanted at 4 and 8 weeks. At each anastomosis, intima to media height ratios (IMHR) were calculated, and smooth muscle (Actin), proliferating (PCNA), and PDGF secreting cell content determined using cell-specific immunohistochemical stains. At the proximal anastomosis, control and stented graft IMHRs were 1.01 +/- 0.16 vs 0.59 +/- 0.18 in 4-week and 1.42 +/- 0.16 vs 0.50 +/- 0.14 in 8-week specimens. Similar IMHR values were present for the distal anastomosis. Peri-anastomotic PCNA cell counts were greater in control grafts at both 4 and 8 weeks. Stented grafts were associated with diminished IMHR and PCNA+ content at both 4 and 8 weeks (P < 0.05). PDGF+ content was similar among control and stented grafts at 4 weeks, while lower in stented grafts at 8 weeks (P < 0.05). At the distal anastomosis, a correlation between PDGF secretion and Actin+ cell content was observed in control grafts at 4 (r = 0.74) and 8 (r = -0.56) weeks. Cell proliferation was associated with PDGF content in 4-week intraluminal and 8-week control grafts (P < 0.05). Changes in IMHR were not the result of differential PDGF secretion. Intraluminal location attenuates intimal hyperplasia in PTFE grafts. The reduced intimal hyperplasia and improved healing of endoluminal grafts could not be attributed to lower PDGF content alone.

Actins↗
PubMed1996

Effect of anesthetic technique on cardiac morbidity following carotid artery surgery.

PURPOSE: To investigate the effect of anesthetic technique on cardiac morbidity after carotid artery surgery. PATIENTS AND METHODS: From 1991 to 1994, 266 consecutive carotid endarterectomies were performed under local/regional (n=140) or general anesthesia (n=126). The effects of anesthetic technique on postoperative adverse cardiac events were assessed retrospectively. RESULTS: Preoperative cardiac testing was performed in all patients undergoing general or local/regional anesthesia. Medical characteristics were similar among patients in both groups. Forty-seven adverse cardiac events (4 myocardial infarction, 9 congestive heart failure, 7 angina, and 27 new ventricular dysrhythmias) occurred postoperatively in 38 patients (14.3%). There were no deaths. The relative risks of general anesthesia for dysrhythmias, myocardial infarction, angina, congestive heart failure, and total adverse cardiac events were 2.22, 0.37, 0.83, 1.38, and 1.5, respectively. The only statistically significant differential was the increased risk of postoperative dysrhythmias after general anesthesia (P<0.03). CONCLUSIONS: Major cardiac morbidity following carotid endarterectomy is independent of anesthetic technique.

Aged↗
PubMed1996

Healing characteristics of intraarterial stented grafts: effect of intraluminal position on prosthetic graft healing.

BACKGROUND: The purpose of this study was to investigate the effect of complete intraluminal placement on prosthetic graft healing. METHODS: Thirty dogs underwent infrarenal abdominal aorta polytetrafluoroethylene interposition (12) or intraluminal stented (18) grafting. Grafts were removed at 4 and 8 weeks. Length of endothelial ingrowth and intima to media height ratios (IMHRs) were calculated. Perianastomotic endothelial (CD31+, factor VIII [FVIII+]), smooth muscle (actin+), macrophage (CD44+), and proliferating (PCNA+) cell content was determined. RESULTS: In control grafts mean proximal and distal anastomotic endothelial cell ingrowth was 0.42 +/- 0.06 and 0.47 +/- 0.08 cm at 4 weeks and 1.10 +/- 0.24 and 0.94 +/- 0.17 cm at 8 weeks. In intraluminal grafts mean proximal and distal anastomotic endothelial cell ingrowth was 1.57 +/- 0.09 and 1.54 +/- 0.12 cm at 4 weeks and 1.88 +/- 0.06 and 2.11 +/- 0.25 cm at 8 weeks. Endothelial ingrowth was greater in all stented grafts (p < 0.001). Mean proximal anastomosis IMHRs were 1.01 +/- 0.16 for 4-week and 1.42 +/- 0.16 for 8-week control grafts and 0.59 +/- 0.18 for 4-week and 0.50 +/- 0.14 for 8-week stented grafts. Similar IMHR values were present at the distal anastomosis. Lower IMHRs were observed in stented grafts (p < 0.05). Content of CD44+, PCNA+, and FVIII+ cells were reduced both proximally and distally in 4-week stented grafts (p < 0.05). Distal content of CD31+ and actin+ cells was greater in 4-week stented grafts (p < 0.05). At 8 weeks CD44+ cell content decreased in controls (p < 0.05). CONCLUSIONS: Intraluminal location enhances prosthetic graft reendothelialization and attenuates intimal thickening.

Animals↗
PubMed1996

Vascular endothelial growth factor and heparin in a biologic glue promotes human aortic endothelial cell proliferation with aortic smooth muscle cell inhibition.

BACKGROUND: Incomplete luminal endothelialization may contribute to small diameter vascular graft failure. Vascular endothelial growth factor (VEGF) can be used to stimulate endothelialization without provoking smooth muscle cell (SMC) proliferation. Heparin and VEGF in a fibrin glue (FG) were investigated for their ability to promote selective human aortic endothelial cell (HAEC) proliferation and human aortic smooth muscle cell (HASMC) inhibition. METHODS: HAECs and HASMCs were seeded on FG containing VEGF (2.5, 10, 30, 100 ng/ml) or VEGF and heparin (5, 50, 500 units/ml). Proliferation assays were performed with tritiated thymidine on days 1 and 3. Results were analyzed by ANOVA, with p < or = 0.05 significant. RESULTS: HAEC proliferation on FG with 10, 30, and 100 ng/ml VEGF was significantly greater than FG alone at days 1 and 3. The addition of 50 units/ml heparin to VEGF significantly increased HAEC proliferation to greater than FG with VEGF alone at day 1. Human aortic SMC proliferation was not stimulated by the addition of VEGF. The addition of 5, 50, and 500 units/ml heparin significantly inhibited HASMC proliferation regardless of VEGF concentration. DISCUSSION: VEGF at 10 ng/ml combined with heparin at 50 units/ml exhibited maximal stimulation of HAECs with inhibition of HASMCs. VEGF and heparin in a biologic glue may improve patency by selectively promoting HAEC proliferation without HASMC growth on synthetic vascular bypass grafts.

Adhesives↗
PubMed1996

Aquatic risk assessment of a polycarboxylate dispersant polymer used in laundry detergents.

Polycarboxylates enhance detergent soil removal properties and prevent encrustation of calcium salts on fabrics during washing. Laundry wastewater typically reaches wastewater treatment plants, which then discharge into aquatic environments. The yearly average concentration of a 4500 molecular weight (MW) sodium acrylate homopolymer reaching U.S. wastewater treatment plants will be approximately 0.7 mg/L. Publications showing the low to moderate acute aquatic toxicity of polycarboxylates are readily available. However, there are no published evaluations that estimate wastewater removal and characterize the probability of exceedance of acceptable chronic aquatic exposure. WW-TREAT can be used to estimate removal during wastewater treatment and PG-GRIDS can be applied to characterize risk for exceedance in wastewater treatment plant outfalls. After adjustments for the MW distribution of the homopolymer, WW-TREAT predicted that 6.5% will be removed in primary treatment plants and 60% will be removed in combined primary and activated sludge treatment plants. These estimates are consistent with wastewater fate tests, but underestimate homopolymer removal when homopolymer precipitation is included. Acceptable levels of chronic outfall (receiving water) exposure were based on aquatic toxicity testing in algae, fish, and Daphnia magna. PG-GRIDS predicted that no unreasonable risk for exceedance of acceptable chronic exposure will occur in the outfalls of U.S. wastewater plants. Future development of wastewater treatment models should consider polymer MW distribution and precipitation as factors that may alter removal of materials from wastewater.

Acrylates↗
PubMed1996

High-dose chemotherapy followed by autologous hematopoietic rescue for Hodgkin's disease patients following first relapse after chemotherapy.

BACKGROUND: The best results of conventional-dose salvage chemotherapy for Hodgkin's disease have been reported after first relapse. We evaluated the results of high-dose chemotherapy and autologous hematopoietic rescue for Hodgkin's disease patients who had relapsed from an initial chemotherapy-induced complete remission. PATIENTS AND METHODS: Eighty-five patients received high-dose cyclophosphamide, carmustine, and etoposide (CBV) followed by autologous bone marrow or peripheral blood stem cell transplantation. RESULTS: Actuarial survival at five years was 51%, and failure-free survival was 40%. Failure-free survival at five years was 90% for patients who received no conventional-dose salvage chemotherapy prior to CBV. Failure-free survival of patients treated initially with a four-drug regimen was not significantly different than patients treated with seven/eight-drug regimens. CONCLUSION: These results appear to be better than those reported for conventional-dose salvage chemotherapy. High-dose therapy followed by autologous bone marrow or peripheral blood stem cell transplantation should be considered for any patient with relapsed Hodgkin's disease, regardless of the length of initial remission, or type of initial chemotherapy. Certain patients, especially those with minimal disease, may benefit by proceeding directly to transplantation after relapse, without first receiving conventional-dose salvage chemotherapy.

Adolescent↗
PubMed1996

Effects of azathioprine withdrawal in kidney recipients with stable function two years after transplant.

To assess the effects of azathioprine withdrawal, renal recipients with grafts > 2 yr function (103 study patients) were tapered off azathioprine over a 1-yr period and compared to 69 patients 2 yr after transplant who were not tapered (controls). Of the 103 study patients, 16 (15%) were living-donor transplants and 87 were cadaveric. Of the 69 control patients, 9 (13%) were living related transplants and 60 were cadaveric. The mean HLA match for those tapered was 3.3 Ag and 3.1 Ag for those remaining on azathioprine. Two study patients restarted azathioprine on their own. Age, sex, and cause of renal failure in both groups was similar. Of the 101 study patients remaining, 9 (8.8%) returned to dialysis due to biopsy proven chronic rejection. There were no acute rejection episodes. Six of the 69 control patients (8.7%) also returned to dialysis for the same reason. Of the 92 patients who have completed the taper, 85 have been off azathioprine for six or more months. There was not a significant difference between the mean 12- and 24-month creatinine levels of the study patients (1.6 mg%, 1.7 mg%) and those of the controls (1.5 mg%, 1.8 mg%). The mean 12- and 24-month hematocritis of patients tapered (41.3%, 40.8%) were comparable with patients not tapered (42.3%, 42.8%). Of interest, the mean hematocritis of both study and control patients rose from 28.9% and 33.5%, respectively, to 41.3% and 42.3% 1 yr following entry into the study. The mean 12- and 24-month white blood counts of those tapered (8.9, 8.7) did not differ significantly from those continued on azathioprine (8.8, 8.8). In stable renal transplant patients on triple drug immunosuppression for at least 2 yr, azathioprine can be discontinued, in a tapered protocol, without an increased risk of graft loss or compromise of renal function.

Azathioprine↗
PubMed1995

Vertebrobasilar syndrome associated with subclavian origin of the right internal carotid artery.

A case of absence of the right common carotid artery with origin of the external carotid artery from the innominate artery and origin of the internal carotid artery from the right subclavian artery proximal to the right vertebral artery is presented. Atherosclerotic occlusion at the origin of the right subclavian artery and occlusion of the left internal carotid artery resulted in a vertebrobasilar syndrome. Blood flow from the right external carotid reconstituted the right vertebral artery via muscular collateral vessels, moving first retrograde to the subclavian artery and then antegrade through the right internal carotid artery. Symptoms were successfully relieved by transposition of the internal carotid to the external carotid artery. This is the second reported case in the literature and the first to be observed in a clinical setting. The anomaly can easily be explained by embryonic persistence of the right ductus caroticus associated with involution of the right third aortic arch.

Arterial Occlusive Diseases↗
PubMed1994

Jugular venous bypass for subclavian vein obstruction.

Symptoms of chronic subclavian occlusion including swelling and pain may be disabling. In the case presented a patient with disabling symptoms 18 years after ligation of the right subclavian vein during resection of a chest wall tumor is successfully treated with a single-anastomosis internal jugular venous bypass.

Adult↗
PubMed1990

Factors affecting patency of venous allografts in miniature swine.

In immunologically defined National Institutes of Health miniswine, a segment of internal jugular vein was anastomosed to the carotid artery as an interposition graft. Patency of swine major histocompatibility complex matched, one haplotype mismatched, and complete mismatched veins was 9.8, 6.3, and 3.0 weeks respectively (p = 0.009). More than 90% of mismatched and 20% of matched allografts developed a positive crossmatch before occlusion (p = 0.006). The mixed lymphocyte response did not predict graft occlusion. Treatment of 10 swine with cyclosporine (10 mg/kg/day) did not significantly improve patency for one haplotype mismatched grafts. In haplotype mismatched veins, cryopreserved grafts occluded more rapidly than noncryopreserved grafts: mean 2.4 versus 6.3 weeks, respectively (p = 0.002). In all cryopreserved vein grafts, alloantibody appeared at or after graft occlusion rather than before occlusion as seen with fresh allografts (p = 0.046). The mean patency of cryopreserved versus fresh autografts was 3.3 and greater than 32 weeks, respectively (p = 0.004). In summary, these results indicate that (1) allograft patency is related to the degree of swine major histocompatibility complex match and development of cytotoxic alloantibodies; (2) moderate-dose cyclosporine does not prolong allograft patency nor suppress development of antibody; (3) cryopreservation may accelerate graft occlusion through nonimmunologic mechanisms.

Animals↗
PubMed1988

Transluminal repair of large intrarenal arteriovenous fistulas.

Renal arteriovenous fistulas may be treated with radiological embolization or surgical ablation. Although recent reports in the literature have proposed embolization as the treatment of choice for renal arteriovenous fistulas, this form of therapy can be associated with significant morbidity in large arteriovenous communications. We report 3 cases of a large intrarenal arteriovenous fistula treated by transparenchymal repair. This technique offers an excellent method of obliterating the fistula without sacrificing the renal parenchyma.

Arteriovenous Fistula↗
PubMed1988

Renal autotransplantation: an alternative to standard renal revascularization procedures.

From January 1978 through December 1987, 22 patients underwent 23 renal autotransplantation procedures for the treatment of renovascular hypertension through the retroperitoneal approach. The causes of the renal artery stenosis were as follows: atherosclerosis (15), fibromuscular dysplasia (6), and Takayasu's arteritis (1). Indications for renal autotransplantation were as follow: disease extending into the renal artery branches (10), stenosis of multiple renal arteries (6), atherosclerotic aorta in high-risk patients (4), and stenosis of renal artery in children (2). The mean preoperative blood pressure of 205 +/- 6/109 +/- 3 mm Hg decreased significantly to 139 +/- 4/77 +/- 2 mm Hg (p less than 0.001). The serum creatinine decreased significantly from a mean preoperative level of 2.2 +/- 0.8 mg/dl to a mean postoperative level of 1.4 +/- 0.4 mg/dl (p less than 0.05). Eleven patients with preoperative renal dysfunction had a significant decrease in the serum creatinine from a mean preoperative level of 3.4 +/- 0.3 mg/dl to a mean postoperative level of 1.9 +/- 0.2 mg/dl (p less than 0.001). One operative death occurred as a result of myocardial infarction. There were three postoperative complications, none of which affected the ultimate result in blood pressure or renal function. This experience demonstrates that in selected patients, renal autotransplantation is an excellent alternative in the surgical treatment of renovascular hypertension.

Adolescent↗
PubMed1988

The association of in vitro arachidonic acid responsiveness and plasma thromboxane levels with early platelet deposition on the luminal surface of small-diameter grafts.

The response of canine platelets to arachidonic acid (AA) stimulation was studied as a predictor of thrombotic potential. Fifty mongrel dogs underwent in vitro platelet aggregation studies with adenosine diphosphate (ADP), collagen, and AA used as inducing agents. Thirty-two dogs were selected on the basis of their response to AA stimulation. Platelet aggregation in response to AA stimulation occurred in 16 (responders) and 16 showed no aggregatory response (nonresponders). The animals were divided into four groups. Group I received no antiplatelet agents (control); group II received U-63,557A, a specific thromboxane synthetase inhibitor (TSI); group III received aspirin; and group IV received aspirin and TSI. Polytetrafluoroethylene grafts were implanted in the carotid and femoral arteries of the dogs in all four groups. Plasma thromboxane (TxB2) levels were drawn before drug treatment and 4 weeks after surgery. Platelet deposition on the luminal surface of the implanted grafts was studied in vivo with a technique that uses both 111In-labeled platelets and 99mTc-labeled red blood cells and was expressed as percentage of indium excess (%IE). Group I (control) dogs whose platelets aggregated in response to AA stimulation had significantly higher 24-hour platelet deposition (%IE) on the luminal surface of implanted grafts (p less than 0.02), lower 4-week graft patency (p less than 0.002), and higher plasma TxB2 levels (p less than 0.01) than those dogs whose platelets did not aggregate. In contrast to the results of AA stimulation, neither ADP nor collagen responsiveness was discriminatory for the thrombotic potential of canine arteries as measured by 24-hour platelet deposition (%IE), 4-week graft patency, or plasma TxB2 levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗