Kenneth E. McIntyre

Contrast-induced nephrotoxicity: The effects of vasodilator therapy☆

The increasingly frequent use of contrast-enhanced imaging for diagnosis or intervention in patients with peripheral vascular disease has generated concern about the incidence and avoidance of contrast-induced nephrotoxicity (CIN). In this prospective study, we sought to identify those patients at greater risk of developing CIN and to evaluate the efficacy of vasodilator therapy with dopamine in limiting this complication. Baseline serum creatinine (Cr) concentrations were obtained on admission and daily for up to 72 hr after angiography in 222 patients undergoing 232 angiographic procedures. The preangiographic treatment was varied at 2-month intervals for 1 year. All patients received an intravenous infusion of 5% dextrose and 0.45% normal saline at a rate of 75 to 125 ml/hr. During the first interval patients received 12.5 g of 25% mannitol immediately prior to their contrast load, in addition to intravenous fluids. During the next 2-month period the patients were given renal dose dopamine intravenously (3 micrograms/kg/min) commencing the evening before angiography and continued to the next morning. During the latter half of the study the treatment regimens were modified so that the use of mannitol was restricted to patients with diabetes mellitus and dopamine to patients with serum creatinine concentrations of > or = 2 mg/dl. Postangiographic elevation in Cr occurred in 2, 10.4, and 62% of studies in patients with baseline creatinine levels of < or = 1.2 mg/dl, 1.3 to 1.9 mg/dl, and > or = 2.0 mg/dl, respectively. None of the patients receiving dopamine experienced an elevation in creatinine. There was no statistical correlation between age, diabetes, or medication with calcium channel blockers and CIN.(ABSTRACT TRUNCATED AT 250 WORDS)

Timing of carotid endarterectomy after acute stroke

An arbitrary delay of at least 6 weeks before performing carotid endarterectomy after acute stroke has been recommended based on anecdotal reports. This prolonged interval may increase the danger of recurrent neurologic deficit before surgery. From September 1978 to September 1988, carotid endarterectomy was performed on 140 patients at variable intervals after stroke. Eleven patients had temporary stroke, which left 129 patients with neurologic symptoms that persisted for 3 weeks or had a cortical infarct on CT scanning. A prospective therapeutic protocol was applied to 82 patients admitted with acute stroke. They were observed until neurologic recovery reached a plateau, based on clinical observation by a neurologist, before performing angiography and carotid endarterectomy (group I). Forty-seven patients were not seen until after recovery from stroke was established (group II). At initial presentation, the severity of neurologic deficit was classified as mild, moderate, or severe in 31%, 58%, and 11%, respectively. Recovery before operation was registered as complete in 11%, mild residual in 66%, moderate residual in 21%, and severe residual in 2%. Group I patients (n = 82, 64%) were operated on within 6 weeks of stroke and group II (n = 47, 36%) were operated on at varying times after 6 weeks. No significant difference was found in the incidence of cerebrovascular events (1.2% vs 4.2%) and deaths (1.3% vs 2.1%) between groups I and II with respect to the timing of carotid endarterectomy, and no significant difference was found between patients operated on at 2, 4, 6, or more than 6 weeks after stroke.(ABSTRACT TRUNCATED AT 250 WORDS)

Prospective comparison of noninvasive techniques for amputation level selection

This study prospectively compared the following tests for their accuracy in amputation level selection: transcutaneous oxygen, transcutaneous carbon dioxide, transcutaneous oxygen-to-transcutaneous carbon dioxide, foot-to-chest transcutaneous oxygen, intradermal xenon-133, ankle-brachial index, and absolute popliteal artery Doppler systolic pressure. All metabolic parameters had a high degree of statistical accuracy in predicting amputation healing whereas none of the other tests had statistical reliability. Amputation site healing was not affected by the presence of diabetes mellitus nor were the test results for any of the metabolic parameters.

The relevance of arterial wall microbiology to the treatment of prosthetic graft infections: Graft infection vs. arterial infection

One potential, but poorly studied source for intraoperative contamination of vascular grafts is the native artery to which the prosthetic graft is attached. The purpose of this study was to analyze the relationship between arterial wall microbiology and graft infection. Between July 1, 1981, and March 31, 1982, arterial specimens were cultured from 88 (30%) of 298 patients undergoing clean, elective arterial reconstructive procedures. Control cultures were obtained from adjacent adipose or lymph node tissue. Positive cultures were obtained from 38 of 88 (43%) of the arterial walls cultured but from none of the control cultures (0 of 20) (p less than 0.001). The most common organism cultured was Staphylococcus epidermidis (27 of 38; 71%). Our overall graft infection rate since January 1, 1981, is 0.9% (3 of 335). All three graft infections occurred in patients with positive arterial cultures. Arterial and graft cultures were also obtained from 20 patients treated for 22 graft infections over the past 13 years. Organisms recovered included staphylococcal species (36%), enteric organisms (46%), and mixtures of the two (18%). These patients with culture-positive graft infections were divided retrospectively into two groups: those with positive and those with negative arterial cultures. Positive arterial cultures were associated with suture line disruption in 8 of 14 cases (57%), but there were no arterial disruptions in patients with negative cultures (0 of 8) (p less than 0.01). These data document a significant correlation between positive arterial wall cultures and subsequent prosthetic infection and also suggest that infection involving the arterial wall is a major determinant of the morbidity and mortality associated with the treatment of prosthetic graft sepsis.

Shoelace technique for delayed primary closure of fasciotomies

Performing a timely fasciotomy for compartment syndrome prevents ischemic injury to muscles and nerves. Fasciotomy entails incision of the overlying skin and investing fascia of the compartment, relieving pressure and enhancing tissue perfusion. Delayed primary closure is ideal, but because of skin edge retraction, the open wound must either heal secondarily or be closed with a split-thickness skin graft. The shoelace technique involves running a silastic vessel loop through skin staples placed at the skin edge along the initial fasciotomy incision. Daily tightening of the shoelace permits gradual reapproximation of the skin edges while compartment edema resolves. Closure using a simple suture or Steri-strip (3M Surgical Products, St. Paul, Minnesota) is then possible after 5 to 10 days. The shoelace technique allows for gradual primary closure of open fasciotomy wounds, thereby avoiding the morbidity and cost associated with skin graft or secondary closure.

Fibrinolytic treatment of residual thrombus after catheter embolectomy for severe lower limb ischemia

Intraoperative intraarterial fibrinolytic therapy (IIFT) was employed in 28 patients with acute limb ischemia. In 17 patients, significant residual calf thrombus was demonstrated by completion arteriography after standard balloon catheter thromboembolectomy, whereas in 11, pretreatment arteriography was not obtained. With the patient systemically heparinized, a bolus of fibrinolytic agent was instilled into the distal vessels below an inflow occlusion clamp. Among the 17 patients under angiographic control, arteriography was repeated after 30 minutes and a second bolus was injected if significant residual thrombus was still present. Successful lysis was achieved in 88% of these 17 limbs and streptokinase (SK) and urokinase (UK) were equally effective. The dosage of SK varied between 50,000 and 150,000 units (seven patients) and of UK between 35,000 and 150,000 units (21 patients). Serum fibrinogen levels declined significantly after IIFT (t test; p less than 0.05), but the average level remained within the normal range. Major bleeding developed in two patients, both of whom received SK and underwent a concomitant major abdominal vascular procedure, with a severe fall in fibrinogen values to 10 and 17 mg/dl. A minor groin hematoma occurred in one patient treated with UK. There was a significant difference in the incidence of bleeding between SK (2/7) and UK (1/21) (chi 2; p less than 0.05). Compartment syndrome developed in six limbs (21%). Amputation was required in two patients (7%). There was no correlation between prolongation of ischemia time as a result of IIFT and the incidence of compartment syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal aortic aneurysm in the patient undergoing cardiac transplantation

In the past 3 years at our institution 130 patients have undergone cardiac transplantation for ischemic cardiomyopathy in 49 (38%), idiopathic cardiomyopathy in 42 (32%), viral cardiomyopathy in 9 (6.9%), pulmonary hypertension in 8 (6%), and graft atherosclerosis in 2 (1.5%). Routine preoperative abdominal ultrasonography was performed on 98 (75%) of these patients with specific visualization of the abdominal aorta in 93 (95%). Abdominal aortic aneurysms (all infrarenal) were found before operation in four patients and only in the subgroup undergoing transplantation for ischemic heart disease (10.5%). They measured 3.4, 4.5, 3.6, and 3.8 cm before transplantation. Periodic evaluation by ultrasonography was carried out after transplantation during the 3-year period of this study. One aneurysm that was initially 3.6 cm increased to 4.0 cm and ruptured 2 months after transplantation. The patient died despite emergent surgery. Aneurysms in three patients who demonstrated rapid aneurysm expansion after transplantation were successfully repaired at 5, 20, and 33 months after transplantation when the lesions reached 5.5, 5.9, and 4.8 cm. A fifth patient with an initially normal (1.5 cm) aorta developed a symptomatic aneurysm of 4.1 cm, which was repaired uneventfully. The average expansion rate of these aneurysms after transplantation was 0.74 +/- 0.15 cm/year. This experience suggests that aneurysms are limited to patients undergoing transplantation for ischemic heart disease. Ultrasound examination may be appropriate for preoperative screening. Careful aortic surveillance after transplantation is important in patients having transplantation for ischemic cardiomyopathy because of the apparent rapid expansion rate compared to aneurysms in the population not receiving transplants.

Control of infection in the diabetic foot: The role of microbiology, immunopathology, antibiotics, and guillotine amputation ☆

Newer culture techniques have demonstrated that diabetic foot infections are polymicrobial, involving both anaerobic and aerobic bacteria. These infections are characteristically foul-smelling and create immense tissue destruction. Occasionally, despite the absence of clostridial organisms, subcutaneous gas may be present. The importance of adequate surgical debridement has been emphasized. In the event of advancing, unremitting infection involving the foot, ankle guillotine amputation may be a life-saving technique. Finally, the role of host-defense mechanism in diabetes is important. Polymorphonuclear leukocyte chemotaxis and phagocytosis are energy-dependent processes that are deficient in the diabetic. Better diabetic control with maintenance of normal blood sugars and avoidance of ketoacidosis may be the key to prevention of these morbid, lower extremity infections.

Critical carotid artery stenosis: Diagnosis, timing of surgery, and outcome

PURPOSE Patients with critical carotid artery stenoses have been considered to be at high risk for carotid artery occlusion necessitating urgent or emergency endarterectomy once the stenosis is identified. Included in this group of patients are those with carotid string sign or atheromatous pseudoocclusion (APO). This review was conducted to determine the impact of the severity of stenosis including APO on the treatment and outcome of patients undergoing carotid endarterectomy. METHODS The records of 203 consecutive carotid endarterectomies performed in 197 patients were reviewed in detail. Patients were stratified into a critical stenosis group (80% to 99% diameter) and noncritical stenosis group based on noninvasive vascular laboratory and carotid arteriography results. Comparisons were performed of demographic data, atherosclerotic risk factors, carotid artery disease presentation, interval between arteriography and endarterectomy, operative details, and surgical results between the critical and noncritical groups and between patients in the critical group with and without APO. RESULTS Carotid endarterectomies were performed on 91 critical carotid artery stenoses and 112 noncritical stenoses. The groups did not differ significantly with regards to demographics, risk factors, carotid artery disease presentation, mean back pressure, and operative use of shunt or patch closure. For the critical group the interval between arteriography and endarterectomy was 8.63 +/- 2.38 days compared with 9.64 +/- 2.14 days for the noncritical group (mean +/- SEM, p = 0.75). No patient in either group progressed to occlusion in the interval between arteriography and endarterectomy. Perioperative strokes occurred in two patients (2%) in the critical group and four patients (3.6%) in the noncritical group (p = 0.09). Likewise, no significant difference was demonstrated in these variables when comparing patients with critical carotid artery stenosis and APO with those without APO. CONCLUSIONS The presence of a critical carotid artery stenosis including APO did not impact on the treatment or outcome of patients requiring endarterectomy nor did it imply the need for emergency intervention to prevent thrombosis. Surgical intervention can proceed after evaluation and optimization of comorbid conditions without undue concern for interval thrombosis.

Value of radiographs and bone scans in determining the need for therapy in diabetic patients with foot ulcers

Thirty-two diabetic patients with foot ulcers were evaluated. Twenty-five patients had foot radiographs, technetium-99m bone scans, and wound and bone cultures; the remaining seven patients had all the studies except bone scanning. Bone changes compatible with osteitis were present on 15 of 32 foot radiographs (47 percent) and on 16 of 25 bone scans (64 percent). Bacterial growth was present in 27 of 32 wounds (84 percent) and 23 of 32 bone cultures (72 percent). Twelve of 23 patients (52 percent) with positive bone cultures had evidence of bone destruction and periosteal reaction on radiographs. The remaining 11 of 23 patients (48 percent) without radiographic signs of osteitis had bacterial growth from their bone cultures. Bone scans were positive in 12 of 18 patients (67 percent) with positive bone cultures and negative in 6 of 18 positive bone cultures (33 percent). We conclude that neither foot radiographs, technetium-99m bone scans, nor wound cultures should be used as the sole criterion for determining the use of antibiotic therapy or amputation in diabetic patients with foot ulcers.