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PART 6 — MISCELLANEOUS
Large studies have documented the feasibility and advantages of intraoperative visceral duplex scan- ning. Hansen and associates applied sonography to 800 renal bypasses, using a velocity of 200 cm/s as an indication to revise. Sensitivity was 86% and specificity was 100%.19,20 Seventy-five percent of these reconstructions are performed in patients with some degree of renal insufficiency, underlining the advantages of avoiding contrast material. The con- sequences of failure in mesenteric revascularization are so catastrophic that intraoperative assessment is a natural adjunct to the procedure. In a study from the Mayo Clinic, 68 visceral reconstructions were monitored with intraoperative duplex scanning. A normal scan was predictive of long-term patency, and an abnormal study was associated with early reintervention, graft failure, and death.21 Their nor- mal criteria includes a PSV 􏰁200 cm/s for the celiac
SUMMARY
artery and a PSV 􏰁275 cm/s for the superior mes- enteric artery, a Vr 􏰂 2.0, and no technical defects (such as vessel narrowing, a thrombus, a dissection, or an intimal flap).
PROCEDURES FOR VENOUS DISEASE
Although arterial reconstructions have received great attention with regard to operative monitoring with duplex sonography, venous interventions are done much more commonly, and duplex scanning is no less useful in this important area. Along with map- ping varicose or incompetent veins, sonography is used for monitoring during endovenous laser therapy (EVLT). Sonographic localization for central venous catheterization has also become the standard of care. These applications of ultrasound with venous proce- dures are reviewed in other chapters within this text.
Success in vascular reconstructions is dependent on excellent preoperative imaging, careful operative planning, technical perfection in the operating room, and careful surveillance and follow-up. Intraoperative duplex sonography offers a unique oppor- tunity to maximize the technical outcomes of surgical revascularization. It requires a commitment to excellence and a team approach, which relies heavily on the interaction of the surgeon and the sonographer or vascular technologist. Applying these techniques will continue to improve the care of vascular patients.
Critical Thinking Questions
1. You are asked to bring equipment down to the operating room to assist with an intraoperative ultrasound on a patient undergoing a carotid endarterectomy. You have multiple ultrasound systems in your department. Which do you select and why?
2. In the operating room, the surgeon has the ultrasound transducer directly over the site of a completed carotid endarterectomy. In one area, there is a strong acoustic shadow and no image of the vessel. The surgeon moves the transducer slightly distally, and a normal carotid artery image is obtained. What is a likely explanation of this artifact?
REFERENCES
1. Barnes RW, Nix ML, Wingo JP, et al. Recurrent versus residual carotid stenosis. Incidence detected by Doppler ultrasound. Ann Surg. 1986;203:652–660.
2. Donaldson MC, Ivarsson BL, Mannick JA, et al. Impact of completion angiography on opera- tive conduct and results of carotid endarterectomy. Ann Surg. 1993;217:682–687.
3. Zannetti S, Cao P, DeRango P, et al. Intraoperative assessment of technical perfection in carotid endarterectomy: a prospective analysis of 1305 completion procedures. Eur J Vasc Endovasc Surg. 1999;18:52–58.