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Biomedical subjects

J M Porter

Publications and source records attributed to J M Porter.

At least 199 records · Page 11Linked to original sources
PubMed1990

The effects of cooling on human saphenous vein reactivity to adrenergic agonists.

Human saphenous veins were obtained at surgery and assayed immediately (n = 10). The veins were cut into rings, suspended in organ chambers, and connected to force transducers for the recording of isometric tension. One ring served as control whereas others were treated with the alpha 1-adrenoceptor antagonist prazosin (3 X 10(-7) mol/L), or the alpha 2-adrenoceptor antagonist rauwolscine (10(-7) mol/L). In quiescent rings cooling from 37 degrees C to 24 degrees C had no significant effect. Norepinephrine (10(-8)-10(-5) mol/L) caused concentration-dependent contractions with an EC20 (-log concentration of norepinephrine required to induce contractions 20% of maximal) = 6.97 +/- 0.10. The contractions were inhibited by prazosin (EC20 = 5.89 +/- 0.17, p less than 0.001) and rauwolscine (ED20 = 5.78 +/- 0.11, p less than 0.001). In control rings cooling potentiated contractions evoked at concentrations of norepinephrine below 10(-6) mol/L and inhibited those at higher concentrations. In rings treated with alpha-antagonists cooling depressed the maximal contractile responses. Contractions to the alpha 1-agonist, phenylephrine (10(-7)-10(-4) mol/L), were inhibited by cooling, whereas those to the alpha 2-specific agonist B-HT 920 (10(-7)-10(-4) mol/L) showed a pattern similar to that seen with norepinephrine. The data indicate that the human saphenous vein possesses both alpha 1- and alpha 2-adrenoceptors postjunctionally, and that both contribute to contractile responses. Cold augments saphenous vein reactivity to norepinephrine by an apparent increase in the responsiveness of alpha 2-adrenoceptors to agonists. The relationship between temperature and adrenoceptor responsiveness may be of pivotal importance in defining the mechanism of cold-induced vasospasm.

Cold Temperature↗
PubMed1990

Vascular surgery residency training curriculum.

The decision to establish a vascular surgery residency confers significant obligations on the institution, the program director, and the faculty. An optimal vascular residency training program must be carefully structured both organizationally and educationally. The Residency Review Committee for Surgery has developed a generally complete and well-reasoned group of requirements for the vascular residency. Nonetheless the program director has considerable latitude in shaping the residency to accommodate these requirements. Our institutional approach to the structure and content of vascular surgery residency training is presented herein.

Accreditation↗
PubMed1990

Clinical results of axillobifemoral bypass using externally supported polytetrafluoroethylene.

Seventy-six axillobifemoral grafts with externally supported polytetrafluoroethylene prostheses were performed since 1983. The indications for operation were absolute (aortic sepsis) in 20 (26%) patients and relative (excessive operative risk or technical difficulty) in 56 (74%) patients. The life-table primary patency for these operations at 4 years follow-up (mean follow-up, 2 years, 4 months) was 85%. We conclude that the patency results achieved in this patient series are sufficiently satisfactory to warrant use of axillobifemoral grafts in an expanded number of patients with high operative risk and need for bypass of aortoiliac occlusive disease.

Aged↗
PubMed1990

Can prosthetic graft infection be avoided? If not, how do we treat it?

Most arterial prosthetic graft infections can be prevented although a few will inevitably still occur. Maintaining a high index of suspicion for graft infection permits prompt diagnosis which provides the opportunity for early surgical management and improved potential for a good result. Aortic graft infection is best managed with extra-anatomical prosthetic bypass through clean tissue followed by graft excision. Results with this surgical approach are improving. Recently, authors advocating in situ grafting for graft enteric fistula as well as others recommending nonresectional therapy for localized prosthetic graft infections, have obtained encouraging results comparable to the best series of more standard excisional therapy. Because prosthetic graft infection remains a difficult surgical problem, any potentially useful management innovations warrant serious consideration and analysis with extended follow-up.

Anti-Bacterial Agents↗
PubMed1990

The importance of routine surveillance of distal bypass grafts with duplex scanning: a study of 379 reversed vein grafts.

To assess the utility of routine duplex surveillance, 379 infrainguinal reversed vein grafts performed at two independent teaching hospitals were prospectively entered into a surveillance protocol from March 1986 through August 1989. An average of 3.2 postoperative duplex graft flow velocity (GFV) measurements per graft was obtained during a mean follow-up interval of 21 1/2 months. Only 2.1% of 280 grafts with GFV measurements greater than 45 cm/sec failed within 6 months of a normal surveillance examination. GFV measurements less than 45 cm/sec in 99 grafts led to arteriography in 75 grafts, identifying 50 stenotic lesions in 48 bypasses (12.6% of series). Inflow lesions were present in 5%, outflow stenoses in 2%, and intrinsic graft stenoses in only 6% of bypasses. Only 29% of grafts identified as failing by duplex scan were associated with a reduction in ankle-brachial index of greater than 0.15. Secondary reconstructions were performed in 48 grafts based on detection of a reduced GFV measurement; all such reconstructions are patent after a mean follow-up of 5 months. Duplex surveillance is more reliable in identification of failing vein grafts than is determination of ankle-brachial index.

Adult↗
PubMed1990

Treatment of failed lower extremity bypass grafts with new autogenous vein bypass grafting.

During the last 9 years we performed 111 bypass procedures for lower extremity ischemia, which occurred after failed infrainguinal bypass grafting. An all autogenous reversed vein bypass was achieved in 103 of 111 operations (93%). Five-year primary and secondary patency of bypasses placed as treatment for one or more failed prior bypass(es) was 57% and 71%, respectively, as compared to 80% and 83%, respectively, for 5-year primary and secondary patency of simultaneously placed first time leg bypasses. Five-year limb salvage for bypass procedures performed as treatment for failed bypass was 90%, which was identical to that achieved for first time bypasses.

Aged↗
PubMed1990

Late complications after femoral artery catheterization in children less than five years of age.

Fifty-eight children who underwent diagnostic femoral artery catheterization before 5 years of age, from 5 to 14 years before the study, were randomly selected from approximately 300 surviving patients undergoing diagnostic femoral artery catheterization at our institution during the interval. Each patient underwent vascular laboratory segmental pressure and waveform examination and arterial duplex scanning, as well as lower extremity bone length radiographs, which were considered positive if the catheterized leg was greater than or equal to 1.5 cm shorter than the opposite leg. Thirteen children who had only venous catheterization served as controls. No arterial abnormalities were present in the control patients (mean ankle/brachial index, 1.01). Arterial occlusion was present in both limbs of five patients who had bilateral diagnostic femoral artery catheterization and in 14 limbs of 51 patients who had unilateral diagnostic femoral artery catheterization. Thus arterial occlusion was present in 33% of patients (19 of 58) and in 37% of limbs (24 of 65). The mean ankle/brachial index in the catheterized limbs was 0.79. Leg growth retardation was present in four limbs (8%) of 51 children undergoing unilateral diagnostic femoral artery catheterization and in one (8%) control patient. The inverse relationship between ankle/brachial index and leg growth retardation was significant (R = 0.47, p less than 0.0005). Only one patient had symptoms of arterial occlusion (claudication), and one patient had symptoms of leg growth retardation (gait disturbance). We conclude that arterial occlusion is common after diagnostic femoral artery catheterization in children less than 5 years of age, but that excellent collateral supply prevents leg growth retardation and/or symptomatic arterial insufficiency in most children.(ABSTRACT TRUNCATED AT 250 WORDS)

Arterial Occlusive Diseases↗
PubMed1989

Analysis of risk factors for myocardial infarction following carotid endarterectomy.

A 4-year experience with 249 consecutive carotid endarter-ectomies performed on 224 patients is reviewed for incidence of perioperative (30-day) myocardial infarction and early survival (mean follow-up, 21 months). Except in cases of unstable angina, coronary arterial disease was evaluated only by routine history, physical examination, and electrocardiogram. By these criteria, 73% of patients had evidence of coronary arterial disease. Patients underwent carotid endarterectomy after appropriate medical management and stabilization of coronary disease symptoms (angina and/or congestive heart failure). One (0.4%) fatal and nine (3.6%) nonfatal perioperative myocardial infarctions Early survival of patients with active symptoms of coronary disease who did not undergo coronary bypass was similar to those patients with preceding or subsequent coronary bypass. The results of this review suggest routine clinical evaluation for coronary arterial disease is sufficient in the large majority of cases prior to carotid endarterectomy. Considering the reported high mortality of coronary bypass among vascular surgical patients, it appears that an aggressive program screening for cardiac surgical candidates either by coronary arteriography or radionuclide studies prior to carotid endarterectomy is not warranted.

Arteriosclerosis↗
PubMed1989

Role of revascularization to treat chronic nonhealing fractures in ischemic limbs.

The contribution of chronic limb ischemia to long-term nonunion of a lower extremity fracture was suggested in a single published case report from our group 13 years ago. We have since encountered three additional patients with nonunited lower extremity fractures occurring in limbs with arterial ischemia. In each of these four patients limb revascularization was undertaken in an effort to stimulate healing of the fracture. These patients had chronic (mean 6 months) nonunion of tibial (three) or femur (one) fractures associated with severe lower extremity ischemia (ankle/brachial index m = 0.33; range 0.24 to 0.5). All patients had histories of chronic lower extremity ischemia before the fracture (ischemic rest pain, 2; claudication, 2). All patients underwent angiography followed by lower extremity revascularization. Restoration of normal arterial supply to the fracture site was followed by healing of the fracture in all patients. To our knowledge, this represents the first reported series of patients undergoing elective limb revascularization to stimulate healing of the fracture. Widespread appreciation of this relationship by orthopedic surgeons may be of considerable clinical importance.

Aged↗
PubMed1989

Epithelioid hemangioendothelioma of the external iliac vein: a primary vascular tumor presenting as traumatic venous obstruction.

A 32-year-old man employed as a laborer presented with the signs and symptoms of iliofemoral venous obstruction of 1 months' duration. Results of initial phlebography from the ankle to the femoral area were normal. No iliac vein anatomy was seen. This led to a group of tests directed toward neuromuscular function, which were unrewarding. On referral to our institution a noninvasive venous vascular laboratory examination was performed, which clearly indicated iliac vein obstruction/stenosis, with a normally patent distal venous system. Subsequent repeat phlebography, including direct femoral vein injection, visualized a mass lesion partially occluding the iliac vein. This lesion was treated with primary excision and segmental venous replacement with an interposition graft of autogeneous internal jugular vein. The excised lesion proved to be an epithelioid hemangioendothelioma of the iliac vein.

Adult↗
PubMed1989

Change in hepatic gene expression after shock/resuscitation.

In response to specific stresses, such as a heat pulse or the sequence of hypoxia-reoxygenation, each isolated cell (prokaryotic and eukaryotic) that has been studied characteristically alters gene expression to synthesize a set of proteins (heat-shock proteins) that are important for intracellular homeostasis. To determine whether a corresponding response occurs within parenchymal cells in vivo when subjected to the complex stress of circulatory shock, liver biopsy specimens were obtained from a swine model of cardiogenic shock before and after shock/resuscitation. With use of complementary DNA prepared from post-shock/resuscitation messenger RNA, a library was constructed and screened for differential gene expression. Of 32/4000 clones initially screened as positive for induction after shock/resuscitation, six were confirmed positive by Northern blot analysis. The nucleotide sequences of two of these six have been determined, and one has been unambiguously identified as metallothionein.

Animals↗
PubMed1988

Limb salvage in end-stage renal disease (ESRD). Comparison of modern results in patients with and without ESRD.

We reviewed our experience with femoral-popliteal-tibial reversed vein bypasses performed for limb salvage in 226 patients without and 19 patients with end-stage renal disease (ESRD). While 18-month primary patency rates were comparable (85% and 89%), limb salvage was significantly lower (76% vs 95%) in patients with ESRD. Five amputations in the ESRD group were required for nonhealing, large foot ulcers in diabetic patients despite patent arterial bypass while only five of 13 amputations in patients without ESRD were required in the presence of patent grafts. The need for major amputation despite patent bypass in diabetic patients with ESRD who have extensive foot gangrene or ischemic ulceration occurs sufficiently often that we recommend primary amputation be considered in these patients without regard to possible vascular reconstruction.

Aged↗
PubMed1988

Treatment of infected abdominal aneurysms by extraanatomic bypass, aneurysm excision, and drainage.

Five patients with infected abdominal aortoiliac aneurysms were treated. The diagnosis was made preoperatively based upon fever, leukocytosis, positive blood culture findings, and presence of an aneurysm in all five patients. Two patients had salmonella species, two had staphylococcus species, and one had bacteroides species cultured from the blood and aneurysm contents. All patients were treated with appropriate antibiotics and a single operative procedure consisting of preliminary extraanatomic bypass followed by complete aneurysm excision and posterior drainage of the retroperitoneum. There were no operative deaths and no instances of aortic stump disruption, persistent retroperitoneal sepsis, or graft thrombosis. All patients were alive and well on last follow-up 15 months to 5 years postoperatively.

Aneurysm, Infected↗
PubMed1988

Vascular laboratory prediction of pedal pressure following femoropopliteal bypass.

This study examines the hypothesis that postoperative ankle-brachial pressure index (postop ABI) can be accurately predicted using noninvasive preoperative segmental leg pressure measurements. Seventy-three patients who underwent successful reverse autogenous vein femoropopliteal bypass and who had pre- and postoperative segmental leg pressure measurements were examined. Predicted postop ABI was estimated using the following formula: Postop ABI = 1 + (Preop ABI) - (Preop BKI). (BKI = below-knee brachial pressure index). Using this formula, 56 out of 73 (81%) patients had a measured postop ABI +/- 20% of predicted postop ABI. Five out of 73 (7%) patients had postop ABI less than 80% predicted, while 12 out of 73 (16%) patients had postop ABI greater than 120% of predicted. All patients with postop ABI greater than 120% of predicted had apparent tibial artery occlusive disease as indicated by preoperative gradients (BKI-ABI) greater than 0.15.

Anastomosis, Surgical↗