A canine model of controlled thrombotic vascular occlusion.

The authors developed a reproducible canine model of arterial thrombotic occlusion. Operative isolation and occlusion of the external iliac arteries (EIA) were combined with balloon de-endothelialization and thrombin injection to induce bilateral thrombosis in 13 dogs. After three to nine days, 26 of 26 vessels contained isolated, discrete thrombi. Arterial blood flow reconstituted at the superficial/deep femoral artery bifurcation in 100% of cases, which limited the distal extent of thrombosis. Arterial dimensions measured intraoperatively showed thrombus volumes to be (mean +/- SD) 1332.1 +/- 243.1 mm3 (right) and 1335.9 +/- 246.8 mm3 (left). A 2-mm hot tip probe powered by an Argon laser was used to recanalize the occlusion in four vessels. Thrombo-ablation volumes accomplished by a single pass of the laser probe averaged 172 +/- 19.7 mm3 per vessel yielding thrombo-ablation energies between 2.6 and 3.5 J/mm3. Quantification of thrombi and simultaneous monitoring of both occluded segments by aortography as well as the large size of the EIA are advantages of this model, which is recommended for studies of thrombotic vascular occlusive disease.

Thermodynamic correlates of hot tip laser angioplasty.

Surface temperatures of normal human cadaver arteries and polytetrofluoroethylene grafts were measured in vitro using thermography to assess vascular wall heating from the metal-capped ("hot tip") laser probe. Laser pulse duration, vessel diameter, blood flow, and saline infusion were varied; power from an Argon laser was constant at 10 watts. The surface temperatures resulting in perforation were 76.2 +/- 2.2 degrees C for arteries and 90.4 +/- 2.1 degrees C for grafts. Blood flow provided an effective heat sink reducing artery and graft wall peak temperatures from 10 watt/5 sec pulses by 12.2 +/- 1.7 and 14.1 +/- 6.1 degrees C at 100 mL/min, and by 16.3 +/- 2.4 and 22.4 +/- 4.9 degrees C at 500 mL/min, respectively. In the occluded conduit, inflow of saline proximal to the probe tip reduced peak temperatures (degrees C) from 10 watt/5 sec pulses as follows: 14.0 +/- 3.2 (artery) and 23.2 +/- 8.5 (graft) at 50 mL/min, and 19.0 +/- 0.6 (artery) and 26.6 +/- 8.5 (graft) at 100 mL/min. Radial heating by the hot tip probe can cause thermal perforation. Blood flow or saline infusion modifies nontarget heating and may offer significant protection to the vasculature.

Vagal schwannoma.

A patient with a benign encapsulated intrathoracic vagal schwannoma is presented and the literature is reviewed. The right paratracheal tumor was identified incidentally on a chest film and excised using a right thoracotomy. Although rare, vagal schwannomas should be considered for any mediastinal mass along the vagus nerves especially when the paratracheal tumor produces minimal or no respiratory symptoms suggesting a slow-growing, encapsulated process.

Complications of acute diverticulitis of the colon: improved early diagnosis with computerized tomography.

We have evaluated the diagnostic role of computerized tomography in 42 patients suspected clinically of having a complication of acute diverticulitis (abscess, colovesical fistula, or both). Diverticular abscesses were confirmed at operation in 10 patients. All 10 patients were diagnosed preoperatively on computerized tomography by the triad of diverticula, a segmentally thickened colon, and extravisceral fluid collection with (6 patients) or without (4 patients) associated gas. Contrast enema study suggested the presence of a diverticular abscess in only two of eight patients studied. Colovesical fistulas were confirmed in 12 patients. Eleven of 12 were diagnosed preoperatively on computerized tomography by the triad of air in the bladder, thickened colon adjacent to an area of thickened bladder, and the presence of colonic diverticula. Contrast enema examinations demonstrated the fistula in only three of eight patients studied. The remaining 20 patients proved to have uncomplicated acute diverticulitis. Findings on computerized tomography included the presence of a segmentally thickened colon with diverticula but without the findings of an abscess or a colovesical fistula. Computerized tomography correctly visualized acute diverticular complications in 21 of 22 patients and it excluded an abscess or fistula in all 20 patients with uncomplicated acute diverticulitis who were suspected of having a diverticular complication. Computerized tomography is the most sensitive and specific test for diagnosing complications of acute diverticulitis. It should be an early consideration in patients with suspected diverticular abscesses or fistulas so that appropriate therapy is not delayed.

The changing spectrum of splenic abscess.

Thirteen cases of splenic abscess were reviewed retrospectively from pathologic and medical records from 1978 through 1986. Splenic abscess is uncommon, but the diagnosis has been made more frequently in recent years due to the increasing number of living immunosuppressed patients and to the use of more sophisticated radiologic diagnostic techniques. Five patients had a solitary abscess (SA) and eight had multiple abscesses (MA). Seventy-five percent of the patients with MA were immunosuppressed, most had no symptoms from the splenic abscess, and none died. Only one patient (with SA) died, a mortality of 10% overall. Previously the mortality has been 40 to 70%. The decreased mortality may in part be attributable to the more rapid diagnosis (3.8 days for SA, 1.8 days for MA) of the splenic abscess, prompting early treatment. Improved radiologic studies reduce the time to diagnosis and thereby improve the prognosis. Computed tomography (CT) was diagnostic for splenic abscess in 4 of 7 patients and suggestive of abscess in the other 3. Computed tomography was the diagnostic modality of choice in suspected splenic abscess, as it provided more information than the other radiologic studies used.

Nontraumatic focal lesions of the spleen: assessment of imaging and clinical evaluation.

Fifty-nine cases of nontraumatic splenic disease were reviewed to evaluate the roles of clinical findings, computed tomography, ultrasound, and radionuclide scanning in diagnosis and management. Patient groups included lymphoma (30 patients), infarct (11 patients), abscess (9 patients), cyst (5 patients), hemangioma (3 patients), and hamartoma (1 patient). In no case were clinical findings alone sufficient to diagnose a splenic lesion. Clinical and laboratory manifestations were nonspecific in all groups. Moreover, no radiologic study reliably diagnosed splenic lymphoma or leukemia. All other focal splenic lesions were consistently diagnosed noninvasively. Cross-sectional imaging was more useful than radioisotope scanning, and often provided adjunctive diagnosis of extrasplenic pathology. The superior detail, spatial resolution, and sensitivity of computed tomography made it the single most valuable diagnostic modality.

Standard of care for hand trauma: Where should we be going?

Emergency Medical Treatment and Active Labor Act, an unfunded mandate for emergency hospital physician coverage, combined with falling reimbursement and escalating medico-legal risk, has resulted in declining enthusiasm for specialty coverage to emergency rooms. In a South West Florida community of 150,000, limited hand surgeons necessitated modification of acute on-call duties for hand trauma, whereby the hospital emergency room personnel performed evaluation and wound management with telephonic consultation followed by referral and definitive care in the outpatient setting by the hand surgeon. The policy for hand care, triage, management, and transfer is reviewed, as well as the first year experience with this highly efficient management methodology for urgent and emergent hand problems. In establishing a county-wide standard of care, emergency rooms and hand surgeons are coordinated to deliver excellent care by treatment protocol.

Multiple-scattering effects on infrared scattering measurements used to characterize droplet size and volume fraction distributions in diesel sprays.

We quantify the maximum error due to multiple-scattering effects for an infrared scattering droplet izing technique. Errors in Sauter mean diameters (SMDs) and liquid volume fractions were estimated lased on experimentally determined polarization properties of the scattered light. Light that is multiply scattered from spherical particles becomes randomly polarized, whereas singly scattered light from a spherical particle contains no cross-polarization scattering component. Therefore measurement of the cross-polarization component (in this case parallel) of the scattering signal is a measure of the multiply scattered light. A ratio of parallel to perpendicular polarized scattered light was experimentally determined and used to calculate an error due to multiple scattering. The infrared scattering measurements and polarization measurements used to quantify the multiple-scattering errors were applied to a typical diesel spray that was injected into three different background conditions: a room ambient condition; a room-temperature, high-pressure condition; and a combusting condition. Droplet SMD, liquid volume fraction, and multiple-scattering errors were determined for a number of locations within the spray; results indicate that the combusting case is negligibly affected by multiple scattering. However, the room ambient case exhibited notable errors due to multiple scattering near the centerline of the spray, and the high-pressure case demonstrated susceptibility to multiple scattering throughout all regions investigated. It is important to note, however, that multiple-scattering errors in many cases translate into relatively small effects on the reported droplet sizes.

Analysis of solid phase debris from laser angioplasty: potential risks of atheroembolism.

Laser energy can vaporize biologic tissues, and this unique method of ablation has been considered for the disobstruction of the occlusive lesion in atherosclerotic disease. To assess the potential embolic sequelae from laser angioplasty, solid phase debris (SPD) was analyzed. Specimens of human cadaver aorta were subjected to standardized argon laser injury, and SPD was quantified by weight in four types of ablated tissue: normal aortic intima, fatty streaks, fibrous plaque, and calcified plaque (CP). The debris by weight of tissue ablated was significantly higher for CP (p less than 0.05), measuring 7.9%, whereas normal aortic intima, fatty streaks, and fibrous plaque yielded 3.2%, 2.7%, and 3.7%, respectively. Likewise, the amount of debris liberated per unit volume of albated tissue was greatest for CP averaging 156 mg/cc. Light and scanning electron microscopy of SPD revealed carbonized tissue particles up to 350 mumol from all classes and cholesterol crystals up to 250 mumol from CP. SPD from CP was infused into renal arteries of rats at two dosages, 4 and 16 mg, to observe effects on end-organ tissue. At 10 days, all kidneys demonstrated focal ischemic atrophy and recovering acute tubular necrosis in a dose-dependent fashion (p less than 0.05). Control rats showed no disease. Kidneys embolized with SPD also displayed foreign body granulomas (9 of 12), periarterial inflammation (11 of 12), and cortical wedge infarcts (10 of 12). Argon laser energy that ablates tissue predominantly by thermal mechanisms liquified or vaporized 96% to 97% of noncalcified atheromatous material. Laser ablation of CP, however, liberated significantly more SPD.(ABSTRACT TRUNCATED AT 250 WORDS)