Carotid body tumors: the role of preoperative embolization.

Resection of carotid body tumors (neck paragangliomas) carries inherent risks of injury to the cranial nerves and other structures as well excessive blood loss. Preoperative embolization has been used to lessen the morbidity in tumors that are larger than 2 cm in diameter. Two female patients presented for treatment with large asymptomatic carotid body tumors-one 4 cm and one 5 cm in diameter. Both patients had preoperative angiography the day before surgery that revealed the feeding arterial vessels so that successful embolization could be accomplished with gel. Success was judged by diminution of the angiographic blush. Both patients had an uneventful surgical excision the following day with the carotid body tumors being able to be resected periadventitially without damage to either the external or internal carotid artery. The cranial nerves were preserved in both patients and blood loss was only 200 cc in both cases. We conclude that preoperative embolization is an important adjunct in treating patients with large carotid body tumors. The surgical exploration proceeds much smoother, the blood loss is minimal, and patients have minimal morbidity.

Screening and preoperative imaging of candidates for carotid endarterectomy.

Randomized clinical trials have provided us with clinical guidelines regarding the indications for performing carotid endarterectomy in patients who have symptomatic and asymptomatic disease. Logically, any patient with a history of transient ischemic attacks, amaurosis fugax, or stroke should be evaluated for extracranial carotid artery occlusive disease. In asymptomatic patients, however, carotid artery surveillance may be helpful in identifying those at risk before neurological events. Patients at particularly high risk include those identified with (1) manifestations of systemic atherosclerotic disease (peripheral vascular disease, coronary artery disease, renovascular disease); (2) presence of a carotid bruit; (3) advanced age (> 65 years); and (4) ABI less than 0.7. Duplex ultrasonography remains the best and most widely used noninvasive screening method, but its accuracy is highly technologist dependent. A high-quality duplex study may, in itself, be adequate to determine whether the severity of extracranial carotid occlusive disease warrants surgical intervention. Catheter-based arteriography may be used as an adjunct to validate duplex results, but its invasive nature and risk of complications has popularized alternative imaging methods. Of these, magnetic resonance angiography (MRA) and spiral computed tomographic angiography (CTA) show excellent promise as noninvasive imaging techniques for the evaluation of extracranial carotid artery occlusive disease.

Effect of lung volume reduction surgery in a rabbit model of bullous lung disease.

Clinical use of staple lung volume reduction surgery (LVRS) has proliferated for treatment of emphysema despite limited data regarding efficacy or optimal techniques. Recent studies in animal models of obstructive lung disease describe the decrease in lung compliance and increase in airway support as mechanisms of an improvement in pulmonary functions analogous to human data. We describe contrasting results in an animal model of bullous lung disease with a mixed but predominantly restrictive pattern of lung disease. Mixed restrictive and bullous lung disease was induced in 17 New Zealand white rabbits with i.v. Sephadex beads and endotracheally instilled carrageenan. Unilateral stapled lung volume reduction surgery was performed at 5 weeks postinduction of emphysema on the right lower lobe by lateral thoracotomy using a pediatric stapler. Static trans-pleural pressures were measured at 60, 40, and 20 cm3 inflation at preinduction (baseline), pre- and postoperatively, and 1 week postoperatively in anesthetized animals. Lungs were then harvested en bloc and examined histopathologically. The effects of volume reduction surgery on static lung compliance, lung conductance, and forced expiratory flows (FEF) were assessed. Five weeks after induction of lung disease, the animals had no significant change in static compliance and forced expiratory volume in 0.5 s (FEV0.5) or lung conductance compared to baseline. Immediately following LVRS, the animals showed a significant decrease in static compliance, FEV0.5, and conductance. One week postoperatively, compliance increased to approximately baseline levels along with a slight increase in FEFs and conductance toward preoperative levels. Histology examination revealed restrictive and bullous lung disease. Thus, we have demonstrated the feasibility of using an animal model for evaluation of volume reduction therapy for restrictive-obstructive lung disease. Physiologically, this model showed decrease conductance and decreased forced expiratory flows following lung volume reduction despite increased recoil. This is in contrast to increased conductance and flows seen in humans with severe emphysema following surgery and suggests that current criteria excluding patients with a significant restrictive component to their lung disease from LVRS surgery may be justified.

Effect of lung volume reduction surgery on pulmonary diffusion capacity in a rabbit model of emphysema.

BACKGROUND: While there is renewed interest in lung volume reduction surgery (LVRS) for treatment of emphysema, many aspects of the operation such as patient selection and surgical end points of excision are uncertain. We studied the effects of LVRS on measured lung volumes and diffusion capacity in an animal model to investigate optimal resection volumes. METHODS: Emphysema was induced in 32 New Zealand white (NZW) rabbits using aerosolized elastase. Helium dilution lung volumes and single breath DLCO were measured concurrently at baseline, following induction of emphysema (preop), and 1 week postoperatively (postop) following LVRS. Bilateral upper and middle lobe stapled lung resections were performed through midline sternotomies with excision of variable amounts of lung tissue from 1.8 to 5.8 g. RESULTS: FRC increased following induction of emphysema and decreased postoperatively. DLCO improved with increasing lung tissue resection up to 3 g of tissue and then decreased as even greater amounts were removed (r = 0.54). CONCLUSIONS: Measured lung volumes increase with development of emphysema and appropriately decrease in response to LVRS in this rabbit model. DLCO improves with moderate resection but then decreases with excessive excision of lung quantities and may help define one physiologic operative end point. In this rabbit model, excision of approximately 30% of lung volume was optimal and prevented further decrease in diffusion capacity.

An animal model for lung volume reduction therapy of pulmonary emphysema.

Stapled lung volume reduction surgery (LVRS) has recently been described for treatment of emphysema. Many questions arise regarding physiologic mechanisms of response from surgical treatment of emphysema. The objective of this study was to develop an animal model for the study of lung volume reduction surgery in diffuse heterogeneous emphysema. We hypothesized that elastic recoil would increase, static respiratory system compliance would decrease, and expiratory flows would increase after lung volume reduction surgery in animals with emphysema. In the study, emphysema was induced in 31 New Zealand White rabbits (3-5 kg) with endotracheally aerosalized porcine elastase (10,000-12,000 U). Lateral thoracotomies were performed 4-6 weeks postinduction under general anesthesia and mechanical ventilatory support. Stapled volume reduction was performed on the right lower lobe using a standard multirow pediatric stapler (U.S. Surgical). Pulmonary function tests were performed at baseline (preinduction), before stapling LVRS (postemphysema induction), immediately post stapling LVRS, and 1 week poststapling. Static respiratory system compliance, flow, conductance and forced expiratory flows, and peak flows at 20 and 40 cm3 of exhaled volume were analyzed. Animals were sacrificed 1 week poststapling, and bilateral lungs were harvested for histopathology. Diffuse but heterogeneous pulmonary emphysema was seen in these animals treated with high-dose aerosolized elastase. Static compliance increased, while expiratory flows and conductance decreased after induction of emphysema. Immediately post stapled volume reduction therapy, animals had decreased static compliance. By 1 week following surgery, animals showed increased forced expiratory flows and decreased expiratory resistance, although compliance was similar to preoperative levels. In conclusion, we describe initial results in an animal model of obstructive emphysema suitable for the study of lung volume reduction surgery. Changes in pulmonary function indicate that unilateral lower lobe LVRS increases airway conductance in the rabbits. Findings from LVRS studies in animal models such as this may help explain clinical improvement following LVRS in humans.

Local treatment of prosthetic vascular graft infection with multivesicular liposome-encapsulated amikacin.

BACKGROUND: Contaminated surgical fields limit the use of prosthetic vascular grafts. We studied the efficacy of sustained-release amikacin applied locally to contaminated grafts in the prevention of infectious complications. MATERIALS AND METHODS: Thirty-one New Zealand white rabbits underwent placement of a polytetrafluoroethylene (PTFE) interposition graft in a 1-cm segment of the descending aorta. The surgical field was infected with application of 10(5) to 10(8) Staphylococcus aureus organisms suspended in normal saline solution. Nineteen rabbits underwent contaminated aortic graft placement without treatment. Twelve rabbits were treated with local application of 2.5 ml of amikacin encapsulated in lipid particle-based sustained-release dosage form. Rabbits were observed for 2 weeks and then evaluated for the presence of graft infection. RESULTS: Seventy-five percent of the treated rabbits survived without evidence of graft infection or systemic sepsis versus 37% in the untreated group (P < 0.04). Cultures verified the absence of organisms in all surviving rabbits without clinical infection. CONCLUSIONS: Sustained-release lipid particle-encapsulated amikacin applied to contaminated PTFE grafts increased survival and decreased postoperative graft infections. Adjunctive use of local, delayed-release antibiotics in contaminated vascular beds may allow wider clinical use of prosthetic grafts.

Factors related to outcome in blunt intestinal injuries requiring operation.

Associated factors related to outcome following blunt intestinal trauma requiring operative therapy were retrospectively reviewed in all trauma patients admitted to one Level I trauma center. Over 4.5 years, 7598 trauma patients were evaluated, with 62 patients having sustained 92 blunt intestinal injuries requiring operative intervention. Mean age was 34.5 years; mean Injury Severity Score was 22. Mechanism of injury was motor vehicle accident in 50 (81%), with 80 per cent being drivers. Associated intra-abdominal injuries occurred in 46 (74%) patients. Extra-abdominal injuries occurred in 56 patients (90%). Thirty-one patients suffered 82 complications or 2.6 complications per patient (comp/pt). Mortality from operative blunt trauma was associated with admission blood pressure < or = 90 mm Hg (57 vs 13%; P < 0.05), age > or = 24 years (26 vs 0%; P < 0.05), and Injury Severity Score > or = 35 (70 vs 8%; P < 0.05). Morbidity was associated with age > or = 24 years (1.5 vs 0.7 comp/pt; P < 0.05) and delay in operative therapy > or = 24 hours (3.3 vs 1.1 comp/pt; P < 0.05). Overall mortality was 18 per cent.

Lung volume reduction surgery for emphysema.

There has been dramatic resurgence of interest in surgical treatment of emphysema, particularly "lung volume reduction" procedures. Recent studies have demonstrated improvements in pulmonary function, lung mechanics, exercise tolerance, and quality of life in selected patients following volume reduction procedures. However, considerable uncertainty remains regarding overall benefit, optimal patient selection, operative techniques, and duration of response. This summarizes current approaches to lung volume reduction surgery, available clinical outcome information, selection criteria, and physiologic mechanisms of response, and discusses the potential role for surgical volume reduction in treatment of emphysema. Recent data appear to support the efficacy of bilateral staple lung volume reduction surgery in patients with severe symptomatic heterogeneously distributed emphysema. Further studies will be needed to determine relative value of different operative techniques and benefit in patients with other clinical presentations.