Postoperative lower extremity bypass surveillance: beyond ankle arm blood pressures.

Surveillance is essential to the postoperative follow-up of lower extremity bypass grafts. Early, intermediate, and late thrombosis place the patient's limb at risk, so detection of problems before the graft fails is critical. Because contrast angiography is not routinely performed for surveillance, most vascular surgeons rely on history, physical examination, and noninvasive vascular studies (NVS) to assess perfusion to the lower extremity after bypass grafting. These NVS include ankle/brachial waveforms, blood pressures, and indexes before and after exercise. The purpose of this study is to report our findings with duplex color-flow ultrasonography (DCU) to examine lower extremity bypass grafts. According to our protocol, we monitor lower extremity grafts with ankle/brachial Doppler pressures, analogue waveforms, and lower extremity exercise when possible. These NVS are performed by nurses in the vascular laboratory before the patient is discharged from the hospital, at least twice during the first year, and then annually. DCU is also performed at least two times during the first year and then annually. If the study results are abnormal or if the patient has symptoms, testing is usually repeated. When abnormalities persist contrast angiography may be warranted. We have detected anatomic and hemodynamic changes in lower extremity bypasses by use of our protocol. By adding DCU to ankle/brachial blood pressures, we have identified aneurysmal dilation, diffuse atherosclerosis, focal narrowing, arteriovenous fistulas caused by unligated venous branches, retained venous valves, and disease progression proximal or distal to the graft.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of duplex and color Doppler imaging in the operating room.

For years vascular surgeons have used objective methods in the operating room to assess the technical quality of vascular procedures. Black and white (duplex) and color Doppler imaging are critical to the preoperative work-up and postoperative follow-up of many patients. With advancing technology it is possible to adapt these imaging techniques for use in the operating room as well. Anatomic and hemodynamic results can therefore be ascertained before the patient leaves the operating room. Over the past 31 months, vascular surgeons at St. John's Mercy Medical Center (SJMMC) have regularly used duplex and color Doppler imaging in the operating room after carotid thromboendarterectomy and renal artery bypass. A peripheral vascular laboratory nurse is called to the operating room and brings the imaging equipment and videotape recorder. The imaging transducer is draped with a sterile sheath and positioned directly on the vessel. Longitudinal and transverse views are obtained; the presence of intimal flap or turbulent color flow is noted. Sound spectral analysis and peak systolic velocity are obtained in centimeters per second (cm/sec) at various locations proximal and distal to the arteriotomy and within the graft or endarterectomized segment. Results are classified as normal or abnormal. Abnormal findings are further classified as accepted or warranting reexploration. Of 81 carotid scans, 55 (67%) were normal and 26 (33%) abnormal by imaging. Of 28 abnormal sites, 14 (17%) were reexplored and the abnormality repaired. The other 14 abnormalities were accepted. Duplex and color Doppler imaging have proved helpful to surgeons in assessing technical results before the patient leaves the operating room.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproducibility of transcutaneous continuous-wave Doppler testing of the carotid arteries.

Hand-held, continuous-wave Doppler probes, coupled with sound spectral analysis, can successfully predict carotid artery stenosis. Changing either the emitting frequency of the probe, the beam/artery angle of the carotid flow velocity (e.g. cardiac output) may alter the recorded frequency shifts. These effects raise questions as to the efficacy of this technique to serially follow carotid atheroma for progressive stenosis. To test the inherent problems with this methodology, a study of reproducibility was conducted. Two Doppler probes (5 MHz and 8 MHz) were compared at the same sitting in 24 patients; 12 were restudied on two subsequent occasions. Peak systolic frequency was 135% higher with the 8 MHz probe; this was lower than the 160% calculated by substitution for emitting frequency in the Doppler formula. The linear correlation coefficient of the two probes was 0.88. In relationship to established laboratory criteria of a greater than 75% area stenosis, no errors were noted with the 5 MHz probe while four errors were noted with the 8 MHz probe. A serial study variation of peak systolic frequency was noted for both probes; these variations did not cross established criteria levels of a severe stenosis when the 5 MHz probe was used, but did with the 8 MHz probe for two carotids. A standard examining probe is recommended. Angle and cardiac output changes do result in peak systolic frequency variation from test to test, but these were not clinically significant with the 5 MHz probe. Thus, significant changes during follow-up testing should provide an index of evolving carotid stenosis.

Pneumatic compression devices for prophylaxis of deep venous thrombosis (DVT).

A pneumatic compression device was applied to 155 patients with a normal Doppler venous examination who underwent a general surgical procedure of at least 1 hr in duration. One hundred fifty-three patients had neither PE nor DVT clinically or by Doppler studies, one patient had a venographically proven DVT, and one patient had a clinical pulmonary embolism verified by lung scanning. Using clinical and Doppler criteria, the device was effective in the prophylaxis of thromboembolic complications.