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Biomedical subjects

J M Porter

Publications and source records attributed to J M Porter.

At least 91 records · Page 5Linked to original sources
PubMed1997

Recommended standards for reports dealing with lower extremity ischemia: revised version.

Recommended standards for analyzing and reporting on lower extremity ischemia were first published by the Journal of Vascular Surgery in 1986 after approval by the Joint Council of The Society for Vascular Surgery and the North American Chapter of the International Society for Cardiovascular Surgery. Many of these standards have been accepted and are used in the current literature on peripheral arterial occlusive disease. With the passage of time, some oversights, aspects that require clarification, and better modifications have been recognized. This report attempts to correct these shortcomings while reinforcing those recommendations that have proven satisfactory. Explanatory comments are added to facilitate understanding and application. This version is intended to replace the original version.

Acute Disease↗
PubMed1997

Pulmonary embolism is associated with the combination of isolated calf vein thrombosis and respiratory symptoms.

PURPOSE: Overall prevalence of pulmonary embolism (PE) in patients with deep venous thrombosis (DVT) isolated to calf veins is low. However, the prevalence of PE in the subgroup of patients with respiratory symptoms and isolated calf vein thrombosis (CVT) is unknown. Such information is important in determining whether patients with CVT only and respiratory symptoms should undergo evaluation for PE. The purpose of this study was to determine the prevalence of PE in patients with respiratory symptoms and isolated CVT. METHODS: From 1992 through 1994, all patients assessed by duplex scanning for lower extremity DVT were reviewed, and those found to have isolated CVT and lower extremity or respiratory symptoms were identified. Patients who had respiratory symptoms or later developed respiratory symptoms in addition to lower extremity symptoms underwent pulmonary angiography or ventilation/perfusion (V/Q) scanning. Positive results on pulmonary arteriograms or "high probability" V/Q scans were considered diagnostic of PE. RESULTS: There were 105 patients with isolated CVT and symptoms. Twenty-six patients had respiratory symptoms; nine (35%) had PE and two died. Seventy-nine patients had only lower extremity complaints; five later developed respiratory symptoms. All five had PE and none had progression of CVT on repeat duplex scanning. Neither age, gender, prior DVT/PE, obesity, pregnancy, medication, known malignancy, smoking, recent surgery, or trauma predicted PE. CONCLUSIONS: Patients with respiratory symptoms and duplex diagnosed isolated CVT have a high prevalence of PE and require pulmonary angiographic or V/Q scanning to rule out PE.

Adult↗
PubMed1997

Functional outcome after infrainguinal bypass for limb salvage.

PURPOSE: Functional outcome after infrainguinal bypass (IB) has recently been assessed with global health status questionnaires but not by criteria specific to the objectives of IB (i.e., maintenance of independent living and ambulation). Preoperative and postoperative living situation and ambulatory status were evaluated in patients who underwent IB for limb salvage (LS) indications. METHODS: For patients in whom IB was performed for LS from January 1980 to July 1995, living situation (independent or dependent) and ambulatory status were assessed before the onset of the need for LS surgery and 6 months after surgery. The importance of risk factors (age, sex, diabetes, heart disease, hypertension, renal insufficiency or failure, previous leg bypass, indication for surgery, postoperative morbidity, graft patency) was assessed by multivariate analysis. RESULTS: IB for LS was performed in 513 patients. Before the development of the indication for LS surgery, 92% lived independently and 91% were ambulatory. The operative mortality rate was 2.7%. At 6 months, 86% were alive and the assisted primary graft patency rate was 92%. Ninety-nine percent of survivors who lived independently before developing the need for LS surgery remained independent 6 months after surgery, and 97% of those who were ambulatory before developing the need for LS surgery were ambulatory 6 months after surgery. Only one of 25 survivors (4%) who were not living independently before surgery achieved independent living 6 months after surgery. Twenty-one percent of nonambulatory patients (6 of 29) became ambulatory. Multivariate analysis confirmed the importance of preoperative living situation and ambulatory status in predicting outcome at 6 months (p < 0.0001). Amputation and loss of primary patency were predictive of poor ambulatory status at 6 months (p < 0.0001, p = 0.025, respectively). The overall 5-year survival rate was 48.1%. CONCLUSIONS: Preoperative independence and ambulation best predict postoperative independence and ambulation after IB for LS indications. IB procedures performed for limb salvage have a low operative mortality rate and maintain independent living and ambulation in 99% and 97% of patients, respectively. Poor overall long-term outcome and survival in LS patients results from intercurrent illness and not from IB.

Activities of Daily Living↗
PubMed1997

Homocysteinemia as a risk factor for atherosclerosis: a review.

In industrialized nations, the leading cause of death and disability is atherosclerosis. Despite a widespread research effort spanning decades, there remains no clearly defined cause or cure for this disease that directly or indirectly affects the lives of almost all individuals in the western world. Autopsy findings show atherosclerosis to some degree in nearly all aged people, suggesting it should be regarded as a normal aging process as well as a disease. Any investigation of atherosclerosis etiology therefore requires a distinction between atherosclerosis normally observed with aging, and pathologic atherosclerosis causing disease and/or death. Atherosclerosis is most appropriately regarded as a disease when associated with both rapid progression and clinical symptoms. Widely accepted risk factors for atherosclerotic disease include advanced age, diabetes, tobacco use, arterial hypertension, hypercholesterolemia, hypertriglyceridemia, decreased high-density lipoprotein, some hypercoaguable states, sedentary life-style, and elevated plasma homocysteine. The study of lipid metabolism has dominated research into atherosclerosis etiology for decades, although now it is widely recognized that a large number of people with symptomatic atherosclerotic disease have no detectable evidence of abnormal lipid metabolism. Elevation in plasma homocysteine has also been widely studied as an independent risk factor for atherosclerosis. A description of the metabolism of homocysteine, its relationship to vascular disease, evidence supporting its role as an independent risk factor for atherosclerotic vascular disease, and the potential role of treatment will form the basis for this review.

Arteriosclerosis↗
PubMed1997

Extending the horizons of "damage control" in unstable trauma patients beyond the abdomen and gastrointestinal tract.

"Damage control" has become an accepted technique for the treatment of patients with exsanguinating injuries to the abdomen. We describe a case where the damage control philosophy was applied outside the confines of the abdominal cavity, a gunshot wound to the groin, and in which a temporary intraluminal shunt was used to maintain distal perfusion while the acidosis and coagulopathy were corrected in the intensive care unit. Successful vascular reconstruction was later completed with polytetrafluoroethylene.

Adult↗
PubMed1997

Diagnostic and therapeutic laparoscopy for penetrating abdominal trauma: a multicenter experience.

BACKGROUND: Considerable skepticism still exists about the role of diagnostic laparoscopy in the evaluation of penetrating abdominal trauma. The reported experience with therapeutic laparoscopy has been limited. METHODS: Retrospective analysis of a collective experience from three large urban trauma centers with 510 patients (316 stab wounds, 194 gunshot wounds) who were hemodynamically stable and had no urgent indications for celiotomy. RESULTS: Laparotomy was avoided in 277 of the 510 patients (54.3%) either because of nonpenetration or insignificant findings on laparoscopy. All were discharged uneventfully after a mean hospital stay of 1.7 days. Twenty-six had successful therapeutic procedures on laparoscopy (diaphragmatic repair in 16 patients, cholecystectomy in 1 patient, hepatic repair in 6 patients, and closure of gastrotomy in 3 patients) with uneventful recovery. In the remaining 203 patients, laparotomy was therapeutic in 155. Fifty-two patients had nontherapeutic celiotomy for exclusion of bowel injuries or as mandatory laparotomy for penetrating gunshot wounds (19.7%). The overall incidence of nontherapeutic laparotomy was 10.2%. Complications from laparoscopy were minimal (10 of 510) and minor. CONCLUSIONS: Laparoscopy has an important diagnostic role in stable patients with penetrating abdominal trauma. In carefully selected patients, therapeutic laparoscopy is practical, feasible, and offers all the advantages of minimally invasive surgery.

Abdominal Injuries↗
PubMed1997

Inferior vena cava injuries: noninvasive follow-up of venorrhaphy.

BACKGROUND AND METHODS: Recent reports have documented a reduced mortality from injuries to the inferior vena cava (IVC). Few reports, however, have addressed the follow-up of the repaired IVC. From January of 1984 to December of 1995, we prospectively collected data on all patients with IVC injuries at Lincoln Medical and Mental Health Center, an urban Level I trauma center. RESULTS: There were 81 patients with IVC injuries: 60 gunshot wounds, 17 stab wounds, and four blunt injuries. Overall, 45 patients survived (56%). Excluding those who arrived without vital signs and those who did not have emergency department thoracotomies, the survival was 68%. Of the survivors, 38 patients received lateral venorrhaphy, and seven patients underwent ligation. Of the 38 survivors with lateral venorrhaphy, 30 patients (79%) underwent noninvasive follow-up: 13 patients by sonography, 11 patients by computed tomographic scan, and six patients by both modalities. The IVC was visualized in 28 patients (93%) and was found to be patent in 24 (86%). There were four thromboses documented noninvasively, with three cases being confirmed by contrast venorrhaphy. All three resolved with systemic anticoagulation. CONCLUSIONS: We conclude that sonography and computed tomographic scan provide reliable noninvasive evaluation of the repaired IVC. We recommend that all patients with an IVC injury, which has been repaired, undergo evaluation for patency before discharge.

Adult↗
PubMed1997

Reperfusion decreases myogenic reactivity and alters middle cerebral artery function after focal cerebral ischemia in rats.

BACKGROUND AND PURPOSE: After focal cerebral ischemia, the function of cerebral arteries is critical to maintain cerebrovascular resistance and minimize damage to ischemic brain regions during reperfusion. In this study we examined the contractile function of isolated and pressurized middle cerebral arteries (MCAs) after 2 hours of occlusion with either 1 to 2 minutes or 24 hours of reperfusion using the intraluminal suture model of transient focal ischemia in rats. METHODS: MCAs were dissected after 2 hours of occlusion with either 1 to 2 minutes (OCC, n = 8) or 24 hours (RPF, n = 5) of reperfusion and compared with those of controls that did not have surgery (n = 5). Isolated MCAs were mounted on two glass cannulas in an arteriograph chamber that allowed control over transmural pressure (TMP) and measurement of lumen diameter. Responses to changes in TMP (including myogenic reactivity, basal tone, and passive distensibility) and sensitivity to serotonin and acetylcholine were compared. RESULTS: Increasing TMP from 25 to 75 mm Hg caused vasoconstriction and development of tone that was similar in control and OCC arteries: percent tone was 33 +/- 5% versus 25 +/- 7% (P > .05). In contrast, tone was severely diminished in RPF MCAs after 24 hours of reperfusion: percent tone = 8 +/- 4% (P < .01). Sensitivity to serotonin was reduced in OCC arteries, increasing the EC50 value from 0.04 +/- 0.1 to 0.11 +/- 0.02 mumol/L (P < .05); after 24 hours of reperfusion, sensitivity of RPF MCAs was similar to control. Vasodilation to 10.0 mumol/L acetylcholine was significantly impaired only in RPF arteries: percent increased lumen diameter was 19 +/- 3% (control) and 13 +/- 4% (OCC, P > .05) versus 9 +/- 2% (RPF, P < .01). Passively, OCC MCAs were more distensible, which was reversed after 24 hours of reperfusion; RPF vessels had distensibility similar to that of control arteries but thicker arterial walls. CONCLUSIONS: Abnormal structure and function of MCAs occur after 2 hours of ischemia, with diminished myogenic reactivity and tone associated with longer reperfusion.

Animals↗
PubMed1997

High glucose concentrations dilate cerebral arteries and diminish myogenic tone through an endothelial mechanism.

BACKGROUND AND PURPOSE: Diabetes is associated with cerebrovascular disease and impaired autoregulation of cerebral blood flow. The purpose of this study was to determine the effect of acute glucose exposure on basal tone and myogenic reactivity of isolated rat cerebral arteries. METHODS: Posterior cerebral arteries (PCAs, n = 38) were dissected from male Wistar rats and mounted on glass cannulas in a system that allowed control of transmural pressure (TMP) and measurement of lumen diameter. Arteries were exposed to various concentrations of glucose, and the amount of basal tone and reactivity to TMP was measured. The effect of elevated glucose on cerebral endothelial modulation of basal tone was determined by mechanical denudation and the use of inhibitors of both nitric oxide and prostaglandin synthesis. RESULTS: Arteries exposed to 44 versus 5.5 mmol/L glucose developed significantly less intrinsic tone (percent tone, 2 +/- 1% versus 28 +/- 2%; P < .01) and responded passively to increases in TMP. Preexisting tone present in 5.5 mmol/L glucose was eliminated on exposure to 44 mmol/L glucose, which decreased tone from 30 +/- 5% to 5 +/- 4% (P < .01). Glucose-induced dilations were concentration dependent such that half-maximal responses were obtained at 25 +/- 2 mmol/L. Endothelial removal abolished this effect, and the amount of tone was similar in 5.5 versus 44 mmol/L glucose (percent tone, 46 +/- 6% versus 49 +/- 5%; P > .05), as did inhibition of nitric oxide production with 0.3 mmol/L nitro-L-arginine (percent tone, 52 +/- 4% versus 46 +/- 3%; P > .05); however, blockade of the cyclooxygenase pathway with indomethacin (10(-5) mmol/L) only partially inhibited the dilation to glucose (percent tone, 32 +/- 3% in 5.5 mmol/L versus 12.4 +/- 3% in 44 mmol/L; P < .01). CONCLUSIONS: Acute glucose exposure dilates arteries with intrinsic tone and impairs cerebrovascular reactivity to TMP via an endothelium-mediated mechanism that involves nitric oxide and prostaglandins.

Animals↗
PubMed1997

Unwillingness to lie supine? a sign of pericardial tamponade.

The stable patient with an occult cardiac injury can represent a diagnostic dilemma. The trauma surgeon must maintain a high index of suspicion for cardiac injury with precordial penetrating trauma. Herein are reported two cases of stable patients with penetrating precordial trauma who refused to lie supine because of difficulty breathing, preferring to sit upright, who eventually had positive pericardial windows and sternotomies for repair of cardiac injuries. The presence of this clinical finding, unwillingness to lie supine, should make the trauma surgeon highly suspicious of a cardiac injury and to proceed quickly to echocardiography or, preferably, to subxiphoid pericardial window to rule out cardiac injury.

Adolescent↗
PubMed1996

Peroneal bypass is equivalent to inframalleolar bypass for ischemic pedal gangrene.

OBJECTIVE: To determine if peroneal bypass is a suitable alternative to inframalleolar bypass in patients with ischemic pedal gangrene. DESIGN: Review of a prospectively acquired vascular registry. SETTING: University practice limited to vascular surgery. PATIENTS: Patients with chronic lower-extremity ischemia and pedal gangrene evaluated between 1985 and 1995 in whom the only options for arterial reconstruction were bypass to the peroneal or an inframalleolar artery. INTERVENTIONS: Peroneal or inframalleolar reverse vein bypass. MAIN OUTCOME MEASURES: Time to healing and lifetable analyses of survival, primary patency, and limb salvage. RESULTS: Eighty-three peroneal and 46 pedal bypasses were performed for ischemic foot gangrene. The groups were equivalent for sex, diabetes mellitus, heart disease, hypertension, renal failure, hypercoagulable states, previous ipsilateral bypass, smoking, and preoperative ankle-brachial indices. Patients with inframalleolar bypass were younger than patients with peroneal bypass (63.9 vs 71.6 years, P = .005) and had higher postoperative ankle-brachial indices (1.02 vs 0.91, P = .004). However, 3-year survival rates (69.1% inframalleolar vs 60.0% peroneal, P = .35), limb salvage rates at 2 years (70.3% vs 85.8%, P = .10), and time to wound healing (19.7 vs 21.6 weeks, P = .66) were equivalent. CONCLUSION: Peroneal and inframalleolar bypass for ischemic pedal gangrene have equivalent intermediate-term survival, limb salvage, and wound healing. Surgeons should not feel obliged to perform inframalleolar bypass for pedal gangrene if peroneal bypass is possible.

Aged↗
PubMed1996

Upper extremity thromboembolism after axillary-axillary bypass grafting.

Two patients experienced upper extremity thromboembolism after axillary-axillary bypass grafting (AxAG) for symptomatic subclavian artery stenosis. The first patient, a 67-year-old male, presented with left upper extremity thromboembolism 3 years after AxAG with 8 mm externally support PTFE. An arteriogram revealed a patent AxAG, thrombus in the proximal left subclavian arterial stump just distal to its occlusion, and multiple digital artery emboli. The patient was treated with warfarin for 8 months, with resolution of symptoms. The second patient, a 57-year-old male, occluded his AxAG (8 mm knitted Dacron) with minimal return of symptoms. Non-operative treatment was elected and 4 years later the patient presented with right upper extremity (donor side) thromboembolism. Arteriography revealed occlusion of the AxAG, radial artery, and digital arteries of the index, long and ring fingers. Thrombolytic therapy of the right arm was undertaken with minimal improvement. Subsequent detachment of the AxAG and placement of an interposition reversed saphenous vein graft was performed. Both patients continue to be asymptomatic during follow-up of 4.7 and 2.0 years, respectively.

Aged↗
PubMed1996

Long-term outcome of Raynaud's syndrome in a prospectively analyzed patient cohort.

PURPOSE: Knowledge of the long-term clinical outcome of Raynaud's syndrome (RS), essential both for patient counselling and formulation of optimal therapeutic recommendations, is conspicuously deficient in current medical literature. We have prospectively monitored 1039 patients with RS, 118 (11.4%) for more than 10 years to determine whether initial characterization was able to predict outcome. METHODS: At initial presentation, patients were divided into four groups on the basis of vascular laboratory and serologic testing results: vasospastic, serologically positive (spast,sero+) and negative (spast,sero-) and obstructive, serologically positive (obst,sero+) and negative (obst,sero-). RESULTS: Connective tissue disease (CTD) was present initially in 48.6% of patients with spast,sero+ results and 72.9% of patients with obst,sero+ results. Of the remaining patients in these groups, progression to CTD during follow-up occurred in 16.4% of patients with spast,sero+ results and 30.4% of patients with obst,sero+ results. In the > 10-year follow-up group, progression to CTD occurred in 81.8% of patients in the obst,sero+ group. Progression to CTD occurred in 2.0% of patients in the spast,sero-group and 8.5% of patients in the obst,sero- group. Digital ulcers occurred in 15.5% of patients in the spast,sero+ group, 5.2% of patients in the spast,sero- group, 55.6% of patients in the obst,sero+ group, and 48.2% of patients in the obst,sero- group. Digital or phalangeal amputations were required in 1.4%, 1.6%, 11.6%, and 19.0% of these patients, respectively. CONCLUSIONS: The long-term outcome of patients with RS can be predicted by initial serologic studies and separation into vasospastic and obstructive categories. Initial serologic positivity strongly predicts the development of CTD. Initial vascular laboratory classification of obstructive RS strongly predicts digital ulcerations, which occurred in half of these patients regardless of initial serologic study results. Amputations were required in 10% to 20% of patients with obstructive RS. These occurrences did not increase with increased duration of disease. Ulcerations and amputations were rare in patients initially with vasospastic RS.

Adult↗
PubMed1996

Prospective comparison of infrainguinal bypass grafting in patients with and without antiphospholipid antibodies.

PURPOSE: The antiphospholipid antibodies (APL)-anticardiolipin antibodies (ACL) and lupus anticoagulant (LA)-are widely believed to be associated with decreased lower extremity bypass graft patency rates. To date, no prospective cohort study has confirmed this assumption. A prospective comparison of the result of infrainguinal revascularization procedures performed since 1990 in patients with and without APL forms the basis of this report. METHODS: Patients who underwent elective infrainguinal bypass procedures from 1990 to 1994 were evaluated for hypercoagulable states (ACL, LA, protein C, protein S, and antithrombin III). Patient data were prospectively entered in a computerized vascular registry, and postoperative follow-up was maintained for life. Graft patency, limb salvage, and patient survival rates were calculated by life-table methods. RESULTS: Three hundred twenty-seven lower extremity bypass grafting procedures were performed in 262 patients. APLs were present in 83 patients (32%); 70 patients (84%) had ACLs only, 11 patients (13%) had LA only, and two patients (3%) had both ACLs and LA. There was no significant difference between APL-positive and APL-negative patients with respect to demographics, associated medical conditions, indication for operations, and type of procedures performed. More patients who had APLs had warfarin treatment after surgery (43% vs 24%, p = 0.002). Life table 4-year primary patency rates showed minimal difference (APL-positive, 43%; APL-negative, 59%; p = 0.087), and no significant difference was noted in assisted primary patency rates (APL positive, 72%; APL negative, 73%; p = NS), limb salvage rates (APL positive, 79%; APL negative, 88%; p = NS), and patient survival rates (APL positive, 67%; APL negative, 66%; p = NS). CONCLUSIONS: APLs were found in a surprising one third of the patients who underwent leg bypass grafting procedures. The majority of APLs identified were ACLs (87%). There was minimal difference in graft primary patency rates, and no difference in assisted primary patency, limb salvage, and survival rates between patients with and without APLs who underwent leg bypass grafting procedures. The extreme morbidity rate associated with APLs in previous reports is not confirmed by this prospective study. APLs should not be regarded as a contraindication to indicated leg bypass grafting procedures.

Aged↗
PubMed1996

Improving selection of patients with less than 60% asymptomatic internal carotid artery stenosis for follow-up carotid artery duplex scanning.

PURPOSE: The Asymptomatic Carotid Atherosclerosis Study (ACAS) indicated significant benefit from endarterectomy compared with medical therapy for patients with 60% to 99% asymptomatic internal carotid artery (ICA) stenoses. To date, optimal selection of patients for vascular laboratory follow-up to determine progression from < 60% to > or = 60% asymptomatic ICA stenosis is unknown. To determine which patients with < 60% asymptomatic ICA stenoses are at greatest risk for short-term progression to > or = 60% without symptoms, we reviewed vascular laboratory results and clinical risk factors of consecutive patients who were prospectively observed in a study of atherosclerosis progression. METHODS: Carotid duplex studies were obtained every 6 months and were reviewed for progression from < 60% to > or = 60% asymptomatic ICA stenosis by using criteria that were developed and reported by our laboratory. Clinical risk factors and velocities from initial duplex scans were analyzed for association with progression from < 60% to > or = 60% ICA stenoses without symptoms. RESULTS: Two hundred sixty-three patients (mean age, 66 years) with 434 asymptomatic < 60% ICA stenoses were prospectively observed for a mean of 20 months, with a mean of four examinations per patient. Seventeen patients (6.5%) and 18 ICAs (4%) progressed without symptoms to > or = 60% ICA stenoses at a mean of 18 months. Clinical risk factors associated with progression to > or = 60% asymptomatic ICA stenosis included elevated systolic blood pressure and decreased ankle-brachial index (p = 0.05). The mean initial ICA peak systolic velocity (PSV) in ICAs that progressed to > or = 60% asymptomatic stenoses was 180 cm/sec, compared with 104 cm/sec in asymptomatic ICAs that did not progress to > or = 60% (p = 0.0003). Thirty-one percent of asymptomatic ICAs that had initial PSVs of 175 cm/sec or greater progressed to > or = 60% stenosis, whereas only 1.8% that had initial PSVs less than 175 cm/sec progressed to > or = 60% asymptomatic stenoses (p < 0.001). The life-table-determined rate of freedom from progression to > or = 60% stenosis was 94% at 4 years for asymptomatic ICA lesions that had initial PSVs less than 175 cm/sec, compared with 14% at 3 years for lesions that had initial PSVs > or = 175 cm/sec. CONCLUSIONS: Early progression from < 60% asymptomatic ICA stenoses to > or = 60% asymptomatic ICA stenoses occurs infrequently. Patients who are at the greatest risk of early progression without symptoms to an ACAS-positive lesion can be identified from the ICA PSV at their initial duplex examination. Early vascular laboratory follow-up of asymptomatic ICA stenoses may be limited to a relatively small group.

Aged↗
PubMed1996

Endothelial function and adrenergic reactivity in human type-II diabetic resistance arteries.

PURPOSE: This study was performed to examine the role of the vascular endothelium in modulating arterial reactivity to adrenergic vasoconstriction in subcutaneous arteries from patients with type II diabetes. METHODS: Small subcutaneous arteries (inner diameter = 90 to 180 microns) from control subjects (n = 22) and patients with diabetes (n = 18) were dissected from skin biopsies obtained at surgery and mounted on a specialized arteriograph that allowed for continuous measurement of lumen diameter under controlled pressure. The sensitivity to norepinephrine was compared in arteries that were either intact, denuded of endothelium, or intact and exposed to N omega-nitro-L-arginine (L-NNA), an inhibitor of nitric oxide synthesis. Stimulated release of nitric oxide by acetylcholine and smooth muscle cell responses to sodium nitroprusside were also evaluated in diabetic and control arteries. RESULTS: Sensitivity to norepinephrine was augmented in diabetic arteries and the amount of agonist necessary to contract the vessels 50% of maximum (EC50) decreased from 0.35 +/- 0.05 mumol/L in the control arteries to 0.16 +/- 0.06 mumol/L in the diabetic arteries (p < 0.05). Both endothelial removal and blockade of nitric oxide synthesis increased sensitivity to norepinephrine in control arteries (EC50 denuded = 0.14 +/- 0.03 mumol/L and EC50 L-NNA = 0.14 +/- 0.04 mumol/L; p < 0.01) but failed to augment sensitivity in diabetic arteries (EC50 denuded = 0.17 +/- 0.05 mumol/L and EC50 L-NNA = 0.15 +/- 0.04 mumol/L; p > 0.05). Stimulated release of nitric oxide by acetylcholine was increased in the diabetic arteries: EC50 control = 0.04 +/- 0.01 mumol/L versus EC50 diabetic = 0.009 +/- 0.001 mumol/L (p < 0.05). Sensitivity of vascular smooth muscle to sodium nitroprusside was similar in both nondiabetic and diabetic arteries. CONCLUSIONS: The endothelium mitigates adrenergic reactivity in control arteries, which is lacking in diabetic arteries and results in enhanced reactivity to norepinephrine; increased sensitivity of diabetic arteries to acetylcholine, however, indicates a possible alteration at the receptor level.

Acetylcholine↗