Gail P. Sandager

Mesenteric flow velocity variations as a function of angle of insonation

This study was designed to quantitate variations in duplex ultrasound arterial flow velocities (cm/sec) in the common carotid artery and the superior mesenteric artery that were produced by changes in the angle of pulsed Doppler insonation. Duplex scanning was used to measure peak systolic flow velocity and mean velocity at angles from 30 degrees to 80 degrees; individual measurements were made at 10-degree increments in both the common carotid artery and the superior mesenteric artery in normal subjects. Peak systolic velocity in the common carotid artery varied from 86 cm/sec at 30 degrees to 168 m/sec at 80 degrees. Over the same transducer angle variation mean velocity ranged from 28 to 53 cm/sec. Similar changes in the superior mesenteric artery flow velocities were observed by varying the angle of insonation, where peak systolic velocity varied from 108 cm/sec (30 degrees) to 280 cm/sec (80 degrees), and mean velocity ranged from 29 cm/sec (30 degrees) to 71 cm/sec (80 degrees). Measurements taken from 70 to 80 degrees produced the most dramatic deviation from those taken at 60 degrees. In the common carotid artery the 70- and 80-degree angles produced 14% and 59% increases, respectively, in peak systolic velocity and 16% and 63% increases, respectively, in mean velocity. In the superior mesenteric artery 70-degree and 80-degree angles produced 16% and 120% increases, respectively, in peak systolic velocity and 17% and 111% increases, respectively, in mean velocity. At 80 degrees the percent increases in measured flow velocities for the superior mesenteric artery were significantly greater than those for the common carotid artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Venous hemodynamics during impulse foot pumping

PURPOSE This study was designed to measure the effect of intermittent pneumatic compression of the plantar venous plexus on popliteal vein (PV) and common femoral vein (CFV) velocities measured by duplex ultrasound scanning. METHODS Thirty lower limbs in 15 healthy volunteers had venous duplex scanning measurement of PV and CFV velocities before and during foot pumping with an arteriovenous impulse foot pump system. Venous velocities were measured at two pump pressure settings (100 mm Hg, 200 mm Hg) and during two pump impulse durations (short = 1 second, normal = 3 seconds). All limbs were examined with the subjects in the supine position, and then measurements were repeated with subjects in the 15-degree reverse Trendelenburg position. The mean maximum venous velocity (MVV) produced by foot pumping was compared with resting venous velocity at each anatomic location and for each technologic variable. RESULTS Impulse foot pumping produced a statistically significant increase in MVV in both the PV and the CFV compared with resting velocities. This significant increase was observed for both pressure settings and both impulse durations, and no differences produced by these two individual variables could be detected. The increase in MVV produced by foot pumping was similar for limbs in the supine position and those examined in the reverse Trendelenburg position. The percentage increase in MVV produced by foot pumping was significantly higher in the PV than in the CFV. CONCLUSIONS Intermittent pneumatic compression of the plantar venous plexus produces measurable increases in venous outflow from the lower limbs of normal subjects. This study seems to justify further evaluation of the effectiveness of this technique for mechanical deep venous thrombosis prophylaxis in selected high-risk patient groups.

Duplex ultrasound insertion of inferior vena cava filters in multitrauma patients

BACKGROUND Techniques for placement of inferior vena cava (IVC) filters have undergone continued evolution from open surgical exposure of the venous insertion site to percutaneous insertion in most cases today. However, the required transport either to an operating room or interventional suite can be complex and potentially hazardous for the multiply injured trauma patient who may require ventilator support, controlled intravenous infusions, or skeletal immobilization. Increased experience with color-flow duplex scanning for routine IVC imaging and portability of ultrasound equipment have suggested the usefulness of duplex-guided IVC filter insertion (DGFI) in critically ill trauma and intensive care unit (ICU) patients. METHODS A total of 25 multitrauma/ICU patients were considered for DGIF. Screening color-flow duplex scans were performed on all patients, and obesity or bowel gas prevented ultrasound imaging in 2 cases, leaving 23 patients suitable for DGFI. In each case, the IVC was imaged in the transverse and longitudinal planes. The right renal artery was identified as it passed posterior to the IVC and was used as a landmark of the infrarenal segment of the IVC. All procedures were performed at the bedside in a monitored ICU setting using percutaneous placement of titanium Greenfield filters. Duplex scanning after insertion was used to document proper placement, and circumferential engagement of the filter struts in the IVC wall. An abdominal radiograph was also obtained in each case to confirm proper filter location. Duplex ultrasound imaging was repeated within 1 week of insertion to assess IVC and insertion site patency. RESULTS DGFI was successful in all cases. The filter was deployed at a suprarenal level in one case, as was recognized at the time of postprocedural scanning. Three patients died as a result of their injuries but there were no pulmonary embolism deaths. Repeat duplex scanning was obtained in 17 patients, and revealed no case of IVC or insertion site thrombosis. CONCLUSIONS Vena caval interruption can be safely performed under ultrasound guidance in a monitored, ICU environment. In selected multiply injured trauma patients, this will reduce the risk, complexity and cost of transport for these critically ill patients. DGFI also reduces procedural costs compared with an operating room or interventional suite, and eliminates intravenous contrast exposure. Preprocedural scanning is essential to identify patients suitable for DGFI, and careful attention must be paid to the known ultrasonographic anatomical landmarks.

Can intrarenal duplex waveform analysis predict successful renal artery revascularizaion

PURPOSE No currently available noninvasive test can preoperatively predict a successful outcome to renal revascularization. Resistance measurements from the renal parenchyma obtained with duplex sonography reflect the magnitude of intraparenchymal disease, and patients with extensive intrarenal disease may respond less favorably to revascularization. To address this question, we reviewed our (primarily) operative experience in patients undergoing renal artery revascularization, and compared the blood pressure (BP) and renal function response with resistance measurements obtained from the kidney both before and after revascularization. METHODS During a 56-month period, 31 consecutive renal artery revascularizations (25 surgical and 6 percutaneous angioplasties) were performed in 23 patients (21 atherosclerotic, 2 fibromuscular dysplasia). Duplex sonography was performed in each patient before and after revascularization, and parenchymal diastolic/systolic (d/s) ratios were calculated. BP and renal function response to intervention were compared with measurements of intrarenal flow patterns before and after revascularization. RESULTS Mean parenchymal peak systolic velocity was significantly higher after repair in all patients (pre-repair: 19.5 +/- 1.3, postrepair: 27.2 +/- 1.7; P < .0001). Despite this, there were no statistical differences between preoperative and postoperative parenchymal d/s ratios. A favorable (cured or improved) BP response was seen in 81% (17 of 21) of revascularizations performed for hypertension. Among these successes, parenchymal d/s ratios were in the normal range (ie, > or = 0.30) both before and after repair (mean prerepair: 0.34 +/- 0.03, mean postrepair: 0.31 +/- 0.03; not significant). In 4 patients in which BP failed to improve after intervention, the d/s ratio was abnormal before surgery (< 0.3), and remained so after revascularization (mean preoperative d/s ratio: 0.18 +/- 0.04, mean postoperative d/s ratio: 0.11 +/- 0.04; P = .003). Mean preoperative parenchymal d/s ratios were significantly higher in all patients with a successful BP response when compared with failures (P = .048). Similarly, among patients with single artery repairs, mean preoperative d/s ratios approached significance in successes vs. failures (success: 0.40 +/- 0.03, failure: 0.21 +/- 0.03; P = .054). A decrease in serum creatinine greater than or equal to 20% was seen in 8 of 18 patients (44%) with ischemic nephropathy. These patients also had normal d/s ratios preoperatively (mean 0.39 +/- 0.04), whereas the 10 patients who failed to improve had significantly lower ratios (mean 0.24 +/- 0.03; P = .041). Kidney length did not correlate with d/s ratio. CONCLUSION Although we do not believe that duplex sonographic measurement of intrarenal flow patterns alone is an accurate means of assessing main renal artery occlusive disease, the resistive indices seem to reflect the magnitude of intraparenchymal disease, and thus may provide important prognostic information for patients undergoing surgical revascularization. Our data suggest that a preoperative d/s ratio below 0.3 correlates with clinical failure relative to BP and renal function responses.

Duplex Scanning for Assessment of Mesenteric Ischemia

The accurate diagnosis of mesenteric arterial occlusive disease has in the past required invasive examination, primarily arteriography. Recent innovations in duplex ultrasound scan technology have for the first time provided a method for the noninvasive assessment of the splanchnic circulation in man. Mesenteric duplex scanning has been used successfully to measure postprandial changes in celiac and superior mesenteric arterial blood flow as well as changes in visceral flow produced by other pharmacologic stimuli.

Prosthetic replacement of the inferior vena cava after resection of a pheochromocytoma

A 52-year-old man had an extensive right adrenal pheochromocytoma with invasion of the pararenal inferior vena cava (IVC). Tumor resection required en bloc resection of the infrahepatic IVC. The right kidney was not involved with tumor. Reconstruction of the IVC was performed with an externally supported, expanded polytetrafluoroethylene graft with reimplantation of the right renal veins into the prosthesis. Postoperative patency of the IVC graft and renal veins was confirmed by venacavography and color-flow duplex scanning. This latter technique has been used to document interval patency of the IVC graft 3, 6, and 12 months after surgery.

Salvage of renal allograft function and lower extremity venous patency with thrombolytic therapy: Case report and review of the literature

Five months after a cadaveric renal transplants a 69-year-old man was admitted with caval, iliac, and renal allograft vein thrombosis that occurred in the setting of a previously placed caval filter. The patients urine output and renal function deteriorated rapidly. Thrombolytic therapy with urokinase was begun, and lysis of the thrombus occurred in 72 hours. The patients renal function returned to baseline, and the transplant was salvaged. Moreover lower extremity venous patency and valvular function were maintained. We report the case and review the literature on thrombolytic therapy for renal allograft vein and lower extremity deep venous thrombosis.