Biomedical subjects

J B Towne

Publications and source records attributed to J B Towne.

At least 109 records · Page 6Linked to original sources

PubMed1987

Durability of the in situ saphenous vein arterial bypass: a comparison of primary and secondary patency.

The use of the saphenous vein in situ is associated with unique problems that decrease primary graft patency (patency uninterrupted by revision). During the past 5 years, we have performed 192 in situ saphenous vein bypasses in 182 patients, including 61 to the popliteal artery, 128 to infrapopliteal arteries, and three to isolated popliteal artery segments. The operative indications were critical limb ischemia in 178 cases (93%), popliteal aneurysm in eight cases (4%), and disabling claudication in six cases (3%). A progressive decline in primary patency occurred after operation. The primary patency rate at 36 months was only 48% for femoropopliteal bypasses and was 58% for femorotibial bypasses. In contrast, the secondary patency rate (patency maintained by thrombectomy, thrombolysis, or revision) at 36 months was 89% and 80% for femoropopliteal and femorotibial bypasses, respectively. The improved secondary patency was due to postoperative surveillance of graft hemodynamics and the success of graft revision. Problems unique to the in situ technique (incomplete valve incision, residual arteriovenous fistula, graft torsion and entrapment) accounted for 58% of early (less than 30 days) graft revisions and 52% of late revisions. The use of Doppler spectral analysis at operation and duplex scanning after operation can locate unsuspected technical errors and identify grafts with low flow at increased risk for failure. The primary patency of the in situ bypass mandates objective assessment of valve incision sites at operation and a protocol of postoperative surveillance to identify grafts that require revision. Early surgical intervention of hemodynamically abnormal but patent in situ bypasses is rewarded by excellent secondary patency.

Adult↗

PubMed1987

The microbiology of explanted vascular prostheses.

The incidence of bacterial colonization and the microflora of prosthetic vascular graft material explanted from 44 patients undergoing graft revision was determined. Graft material for culture was obtained from aortofemoral or femoropopliteal vascular prostheses without signs of infection but requiring revision for femoral anastomotic aneurysm (n = 21) or thrombosis (n = 26). Explanted graft material was placed in tryptic soy broth and ultrasonically oscillated to disrupt the adherent graft surface biofilm, which is a technique that increases the recovery of microorganisms compared with standard microbiologic culture methods. Microorganisms were isolated from 90% (19/21) of grafts associated with anastomotic aneurysms and 69% (18/26) of thrombosed grafts. Staphylococcus epidermidis was the prevalent organism recovered and accounted for 69% of the isolates. Slime production, a growth characteristic of S. epidermidis associated with prosthetic device infection in humans, was demonstrated by 87% (13/15) of strains isolated from grafts with pseudoaneurysms compared with 33% (4/12) of strains isolated from occluded grafts (p less than 0.01). Despite the high incidence (79%) of colonization of vascular prostheses, no patient developed wound or graft infection after graft replacement and perioperative antibiotic administration. Low-virulent microorganisms, such as S. epidermidis, can colonize vascular prostheses and not provoke signs of graft infection. The high recovery rate of slime-producing S. epidermidis strains from grafts with anastomotic aneurysms and the adherence-mediated growth of these bacteria on biomaterials suggest this late graft complication is the sequelae of a bacteria-laden biofilm infection.

Aneurysm↗

PubMed1987

The influence of sepsis and ischemia on the natural history of the diabetic foot.

One hundred seventeen diabetic patients with lesions involving 174 extremities were reviewed to evaluate the natural history of the problem and specifically those factors that influence its course both acutely and chronically. The extremities of diabetic patients with foot lesions can be categorized based on severity of infection and presence of ischemia. Half of these patients developed lesions in the contralateral extremity either concurrently (synchronous) (7%) or later (metachronous) (43%). Major amputation was required in 59 of the 174 extremities evaluated (34%). In patients with metachronous lesions, unilateral amputations were required in 28 per cent of patients and bilateral amputations in 26 per cent. Limb salvage by revascularization required 1.4 operations per extremity, carried 2 per cent operative mortality and was successful in 66 per cent. Although 24 per cent of these patients died within 5 years of the initial presentation of their foot lesions, these data suggest that limb salvage attempts are reasonably successful and relatively safe. The combination of extremity sepsis and ischemia in the diabetic adversely effects the survival of both the extremity and the patient.

Amputation, Surgical↗

PubMed1986

Mucin production by Staphylococcus epidermidis. A virulence factor promoting adherence to vascular grafts.

The production of an exopolysaccharide (mucin) by some Staphylococcus epidermidis strains facilitates bacterial adhesion to prosthetic vascular grafts and may play an important role in adherence-mediated growth. An in vitro model was developed to measure the differential adherence of mucin-producing (RP-12) and nonmucin-producing (SP-2) S epidermidis strains onto expanded polytef and velour knitted Dacron graft material. After incubation in a 10(7)/mL suspension of organisms, graft specimens were repeatedly washed to remove nonadherent organisms and then sonicated to dislodge adherent organisms. Bacterial adherence was calculated from a quantitative culture of the sonication effluent. Both S epidermidis strains adhered in ten to 100 times greater numbers to the knitted Dacron graft material than to expanded polytef. The production of an exopolysaccharide by the RP-12 strain significantly increased adherence to both graft types compared with the SP-2 strain. The increased adherence of the RP-12 strain was inhibited by adding D-mannosamine to the inoculum. The in vitro model developed is well suited for further study of the mechanisms by which bacteria adhere to and colonize vascular grafts.

Adhesiveness↗

PubMed1986

Intraoperative assessment of in situ saphenous vein arterial grafts using pulsed Doppler spectral analysis.

Errors in anastomotic construction, retained competent valves, and arteriovenous fistulas can cause both early and delayed failure of in situ saphenous vein arterial grafts. Pulsed Doppler spectral analysis of midstream flow was compared with arteriography in 50 consecutive in situ saphenous vein bypasses for the detection of unsuspected technical error. Based on spectral changes in the velocity waveform indicating flow disturbance, intact valve cusps could be distinguished from arteriovenous fistulas, and technically unsatisfactory anastomoses were identified. Competent valve cusps were identified in nine (5%) of 180 valve-incision sites, and six anastomoses (6%) were judged unsatisfactory. The presence of severe flow disturbance was always associated with an anatomic defect on arteriography. Incision of missed valve cusps and anastomotic revisions corrected associated flow disturbances. Doppler flow analysis readily located high-flow arteriovenous fistulas, thereby reducing operative time and the need for multiple arteriograms. The high sensitivity of this method (no false-negative assessments) makes it an ideal screening test, resulting in the selective use of operative arteriography.

Angiography↗

PubMed1986

Profundaplasty: its role in limb salvage.

The concept of the profunda artery as a collateral system is very useful in determining which patients may benefit from profundaplasty. When hemodynamic profunda stenosis is associated with combined aortoiliac and superficial femoral artery occlusive disease, profundaplasty as an adjunct to an arterial inflow procedure is highly successful. It is most efficacious when performed for disabling intermittent claudication and less successful for limb salvage indications. When isolated profundaplasty is performed for limb salvage, it may be an appropriate first procedure to heal ischemic ulcers and relieve rest pain. Ischemic gangrene is less frequently resolved and may require distal bypass. However, if the PPCI is low and/or the arteriographic appearance of the profunda system is favorable, then isolated profundaplasty may be successful. When limb salvage is precluded by extensive pedal necrosis or end-stage arterial disease, profundaplasty may provide effective perfusion of the knee joint so that a more functional below-knee amputation may be performed.

Amputation, Surgical↗

PubMed1986

Six-year prospective multicenter randomized comparison of autologous saphenous vein and expanded polytetrafluoroethylene grafts in infrainguinal arterial reconstructions.

Autologous saphenous vein (ASV) and polytetrafluoroethylene (PTFE) grafts were compared in 845 infrainguinal bypass operations, 485 to the popliteal artery and 360 to infrapopliteal arteries. Life-table primary patency rates for randomized PTFE grafts to the popliteal artery paralleled those for randomized ASV grafts to the same level for 2 years and then became significantly different (4-year patency rate of 68% +/- 8% [SE] for ASV vs. 47% +/- 9% for PTFE, p less than 0.025). Four-year patency differences for randomized above-knee grafts were not statistically significant (61% +/- 12% for ASV vs. 38% +/- 13% for PTFE, p greater than 0.25) but were for randomized below-knee grafts (76% +/- 9% for ASV vs. 54% +/- 11% for PTFE, p less than 0.05). Four-year limb salvage rates after bypasses to the popliteal artery to control critical ischemia did not differ for the two types of randomized grafts (75% +/- 10% for ASV vs. 70% +/- 10% for PTFE, p greater than 0.25). Although primary patency rates for randomized and obligatory PTFE grafts to the popliteal artery were significantly different (p less than 0.025), 4-year limb salvage rates were not (70% +/- 10% vs. 68% +/- 20%, p greater than 0.25). Primary patency rates at 4 years for infrapopliteal bypasses with randomized ASV were significantly better than those with randomized PTFE (49% +/- 10% vs. 12% +/- 7%, p less than 0.001). Limb salvage rates at 3 1/2 years for infrapopliteal bypasses with both randomized grafts (57% +/- 10% for ASV and 61% +/- 10% for PTFE) were better than those for obligatory infrapopliteal PTFE grafts (38% +/- 11%, p less than 0.01). These results fail to support the routine preferential use of PTFE grafts for either femoropopliteal or more distal bypasses. However, this graft may be used preferentially in selected poor-risk patients for femoropopliteal bypasses, particularly those that do not cross the knee. Although every effort should be made to use ASV for infrapopliteal bypasses, a PTFE distal bypass is a better option than a primary major amputation.

Actuarial Analysis↗

PubMed1986

Bacterial adherence to vascular prostheses. A determinant of graft infectivity.

An in vitro model was developed to quantitatively measure bacterial adherence to the surface of prosthetic vascular graft material. Four strains of bacteria (Staphylococcus aureus, nonmucin-producing S. epidermidis [SP-2], mucin-producing S. epidermidis [RP-12], and Escherichia coli) were used to inoculate expanded polytetrafluoroethylene (ePTFE), woven Dacron, and velour knitted Dacron graft material. After graft specimens were incubated in a 10(7) suspension of bacteria, they were washed to remove nonadherent organisms and ultrasonically oscillated to dislodge adherent organisms. Quantitative culture of the sonication effluent was used to calculate bacterial adherence, expressed as the number of colony-forming units found in each square centimeter of graft material per 10(7) inoculum. All bacterial strains had a greater affinity to velour knitted Dacron graft than to ePTFE (p less than 0.025). E. coli and S. aureus adhered to velour knitted Dacron in greater numbers than to woven Dacron (p less than 0.04). The production of extracellular polysaccharide (mucin) by the RP-12 strain significantly increased adherence to both EPTFE and Dacron grafts compared with the other three bacterial strains tested (p less than 0.04). Although E. coli was less adherent to ePTFE than nonmucin-producing staphylococcal strains (S. aureus and SP-2), no difference in adherence to knitted or woven Dacron graft material was demonstrated. The differential adherence of bacteria to prosthetic vascular grafts pays an important role in the pathogenesis of graft sepsis and determines relative graft infectivity. The in vitro model developed is well suited for further study of the mechanisms by which bacteria adhere to and colonize vascular grafts.

Adhesiveness↗

PubMed1986

Multiple paradoxical emboli.

We report a case of multiple paradoxical emboli involving the common carotid, right subclavian, right renal, celiac, and superior mesenteric arteries. Paradoxical embolus is an uncommon but important cause of acute arterial occlusion. Successful management requires prompt recognition, prevention of further embolization, and treatment directed toward relief of the acute arterial occlusion.

Adult↗

PubMed1985

Classification of carotid bifurcation disease using quantitative Doppler spectrum analysis.

Spectrum analysis of continuous-wave Doppler recordings from the region of the carotid bifurcation was used to classify the degree of stenosis in the internal (ICA) and external (ECA) carotid arteries. Measurements of systolic peak frequency, end-diastolic frequency, and the degree of spectral broadening were used to define five ICA disease categories: 0% to 15% diameter reduction (DR), 16% to 49% DR, 50% to 80% DR, greater than 80% DR, and occlusion. The results were compared to contrast arteriography in 122 patients (243 arteries). The agreement with angiography in classifying ICA stenosis was 82%. Doppler spectrum analysis identified 96% of hemodynamically significant disease (greater than 50% DR) in the ICA and ECA and 97% of ICA occlusions. Attention to the common carotid artery waveform and the ICA diastolic frequency improved the accuracy of predicting greater than 80% DR and occlusion of the ICA. Noninvasive classification of carotid bifurcation disease is useful in clinical decision making to select the angiographic technique most likely to accurately define disease morphology and to follow up patients for disease progression.

Aged↗

PubMed1985

Endarterectomized superficial femoral artery as an arterial patch.

Eighty-six patients underwent 90 profundaplasties for lower extremity ischemia using endarterectomized superficial femoral artery (ESFA) or vein as an arterial patch. Standard length profundaplasty was performed in 60 limbs and extended profundaplasty in 28. Seventy-two were performed for limb salvage and 18 for severe claudication. Fifty-four limbs underwent inflow reconstruction and profundaplasty, while 36 others had profundaplasty alone. Three-year cumulative patency rates were employed to compare the type of autogenous patch material to the profundaplasty length, operative indications, and procedures. In all groups, ESFA performed as well as vein. Endarterectomized superficial femoral artery patch angioplasty provides comparable long-term results to vein patch in patients undergoing profundaplasty, and demonstrates its durability as a vascular patch in situations where autogenous tissue is required or preferred while preserving the saphenous vein for later use.

Adult↗

PubMed1985

Isolated profundaplasty for limb salvage.

Fifty-four patients underwent 56 profundaplasties for limb salvage. All had stenosis greater than 50% in diameter of the deep femoral artery and associated superficial femoral artery occlusive disease. After profundaplasty, ischemic ulcers healed in 9 of 17 (53%) patients. Rest pain was relieved in 6 of 19 (32%) and areas of ischemic necrosis healed in 7 of 20 (35%). Cumulative patency of the deep femoral artery was 49% at 3 years but fell to 21% at 5 years, whereas cumulative limb salvage was 49% and 36%, respectively. Eleven of the required 28 amputations were performed in the immediate postoperative period. Profundaplasty was used to lower the amputation level and preserve the knee joint in six patients. The other five early amputations occurred in severely ischemic limbs without distal vessels suitable for bypass. The profundaplasty remained patent in all 19 patients who underwent below-knee amputation and 16 (84%) became ambulatory with a prosthesis. Hemodynamic data provided by determination of the profundapopliteal collateral index predicted limb salvage in 10 of 11 (91%) of limbs when the index value was less than or equal to 0.19. Other clinical criteria, such as preoperative ankle-brachial index and the presence of diabetes mellitus, had no predictive value. Isolated profundaplasty for limb salvage is an effective first procedure for selected patients and provides a reasonable alternative to primary amputation or high-risk distal bypass. When amputation is inevitable, effective perfusion of the profunda femoris artery is essential for preservation of the knee joint and results in a high degree of functional rehabilitation.

Aged↗

PubMed1985

Lessons learned in adopting the in situ saphenous vein bypass.

A 3-year experience with in situ saphenous vein bypasses was analyzed to evaluate the suitability of the conduit, the effect on vein utilization rate, the ease of valve ablation, the incidence of persistent arteriovenous (AV) fistula, the duration of the operation, and the nature of the learning curve to become adept at this technique. From 1981 through 1983, 74 patients underwent 55 femoral-tibial and 23 femoral-popliteal in situ saphenous vein bypasses. The operative indications were threatened limb loss in 76 (97%) and disabling claudication in 2 (3%); 35 of 74 patients (48%) were diabetic. In the last year pulsed Doppler spectrum analysis was added to arteriography for intraoperative graft assessment. For 55 femoral-tibial grafts measured by life-table patency rates at 30 days, only one femoral-popliteal graft failed (1 1/2 years). Complete vein utilization was accomplished in 91% of the bypasses attempted. In 41 of the 78 (51%) grafts, vein diameter was 3.5 mm or less. Operative time decreased with experience. Pulsed Doppler spectral analysis has proved useful for intraoperative graft evaluation. The in situ saphenous vein has become the conduit of choice for infrageniculate bypass.

Adult↗

PubMed1985

A low flow velocity predicts failure of femoropopliteal and femorotibial bypass grafts.

The prognostic value of Doppler-derived blood flow velocity measurements for predicting the patency of femoropopliteal and femorotibial bypass grafts was analyzed. Peak systolic and end-diastolic blood flow velocities were measured in 42 femorotibial, 24 femoropopliteal, and three femoropopliteal (isolated segment) in situ saphenous vein bypasses at operation and serially in the postoperative period. At operation peak systolic flow velocity was greater (p less than 0.01) in femoropopliteal grafts (90 +/- 22 cm/sec) compared with femorotibial grafts (68 +/- 19 cm/sec) and isolated segment femoropopliteal (58 +/- 16 cm/sec) grafts. Diastolic forward flow, indicative of low outflow resistance, was present in all successful grafts at operation and in the immediate postoperative period, but decreased thereafter. Early graft occlusion was associated with a low peak systolic flow velocity (less than 40 cm/sec) and absent diastolic forward flow. Postoperative decrease in peak systolic velocity to less than 45 cm/sec identified grafts with impending failure due to intrinsic graft lesions or progression of atherosclerosis. A low blood flow velocity threatens graft patency and should prompt an angiographic evaluation to identify correctable graft lesions or an outflow tract suitable for sequential grafting for the purpose of augmenting flow velocity.

Adult↗

PubMed1984

Aortofemoral graft infection due to Staphylococcus epidermidis.

A ten-year review of aortofemoral graft infection documented Staphylococcus epidermidis as the infecting organism in 18 (60%) of 30 cases. Diagnosis of such infection required a high index of suspicion because of its late postoperative appearance (mean interval of 41 months) and the inability to identify a microorganism at operation by routine wound culture or Gram's stain. Clinical findings suggesting graft infection included multiple anastomotic aneurysms (18 patients), perigraft exudate (16 patients), a draining groin mass (five patients), and aortoduodenal fistulas (two patients). Due to the low concentration and virulence of the organism, aerobic culture of the prosthetic fabric in broth media provided the optimum method of confirming the S epidermidis infection. Total graft excision with immediate vascular reconstruction was the preferred treatment method and resulted in a mortality and major amputation rate of 11%.

Aneurysm↗

PubMed1984

Acute limb ischemia following aortic reconstruction. A preventable cause of increased mortality.

Acute limb ischemia following aortic reconstruction is primarily related to intraoperative technical errors and is associated with significantly increased mortality. Elective aortic reconstruction was performed on 262 patients between 1975 and 1981. Surgical indications were aneurysm in 84 patients (32%), occlusive disease in 125 (48%), and both of these in 53 (20%). Acute limb ischemia developed postoperatively in 27 patients (10.3%); it was noted at the conclusion of the operation in five (19%) of them and within the first 48 hours in 22 (81%). The mortality was greater in the combined aneurysm and occlusive disease group than in the aneurysm-only and occlusive disease-only groups, primarily because of an increased incidence of myocardial disease in the combined group. Postoperative limb ischemia was mainly a result of technical error and resulted in increased mortality in all groups.

Aged↗

PubMed1984

Effect of circumferential pneumatic compression devices on digital flow.

We reviewed the effects of circumferential pneumatic compression suits (CPCS) when applied to normal and ischemic limbs without prior application of prehospital orthopedic traction devices beneath the garment. The digital arterial toe pressures of 11 normal and six claudicating limbs were measured with the trouser applied and the limbs pressurized to 40, 60, 80, and 100 mm Hg. In addition, normal limbs had the Hare traction device and the Sager splint applied prior to application of the trouser and retesting of the digital arterial flow. We conclude that CPCS prevents flow into the limbs, and this may potentiate the development of compartment syndromes in the previously traumatized or ischemic limbs. Normal limbs with traction devices already applied may be at a higher risk for compartment syndromes, and we suggest that patients with fractured limbs who are in need of CPCS not have the traction device applied.

Blood Pressure↗

PubMed1984

Effect of primary renal disease in patients with renovascular insufficiency.

The effect of laboratory evidence of renal parenchymal abnormality on the results of renal revascularization in 83 patients with renovascular hypertension was determined. Primary renal disease (PRD) was defined as an abnormal urinalysis (proteinuria, hematuria, or casts) in the absence of urinary infection, or decreased renal function (elevated serum creatinine level greater than 1.5 mg/dl and/or decreased creatinine clearance). All patients were hypertensive on medical therapy preoperatively. Patients were defined as cured if postoperative diastolic blood pressure (BP) was less than 90 mm Hg on no medication and improved if BP less than 90 mm Hg on medication. Sixty-six patients (80%) were cured or improved following revascularization. Of 45 patients (63%) with evidence of PRD preoperatively, 28 (62%) were cured or improved compared with 33 patients without PRD, of whom all (100%) were cured or improved (p less than 0.001). Each of five patients with transplant renal artery stenosis had two operations; four were cured or improved. The serum creatinine level was elevated preoperatively in 37 cases. Eighteen of the 37 (49%) improved to within normal limits following operation. Fifteen patients had simultaneous bilateral renal artery revascularization, and 12 (80%) were cured or improved. Fourteen patients (17%) had concomitant vascular procedures: aortobifemoral bypass (seven), abdominal aneurysm resection (five), femoral endarterectomy (one), and aortoiliac bypass (one). Twelve of these 15 patients had PRD, and 8 of the 12 (67%) were cured or improved. Only one death occurred in the perioperative period. Thirty-eight patients (46%) had been treated for hypertension for more than 12 months before referral.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗