The efficacy of the new SCD Response Compression System in the prevention of venous stasis

AbstractObjective: The current commercially available sequential intermittent pneumatic compression device used for the prevention of deep venous thrombosis has a constant cycle of 11 seconds’ compression and 60 seconds’ deflation. This deflation period ensures that the veins are filled before the subsequent cycle begins. It has been suggested that in some positions (eg, semirecumbent or sitting) and with different patients (eg, those with venous reflux), refilling of the veins may occur much earlier than 60 seconds, and thus a more frequent cycle may be more effective in expelling blood proximally. The aim of the study was to test the effectiveness of a new sequential compression system (the SCD Response Compression System), which has the ability to detect the change in the venous volume and to respond by initiating the subsequent cycle when the veins are substantially full. Methods: In an open controlled trial at an academic vascular laboratory, the SCD Response Compression System was tested against the existing SCD Sequel Compression System in 12 healthy volunteers who were in supine, semirecumbent, and sitting positions. The refilling time sensed by the device was compared with that determined from recordings of femoral vein flow velocity by the use of duplex ultrasound scan. The total volume of blood expelled per hour during compression was compared with that produced by the existing SCD system in the same volunteers and positions. Results: The refilling time determined automatically by the SCD Response Compression System varied from 24 to 60 seconds in the subjects tested, demonstrating individual patient variation. The refilling time (mean ± SD) in the sitting position was 40.6 ± 10.0 seconds, which was significantly longer (P <.001) than that measured in the supine and semirecumbent positions, 33.8 ± 4.1 and 35.6 ± 4.9 seconds, respectively. There was a linear relationship between the duplex scan–derived refill time (mean of 6 readings per leg) and the SCD Response device–derived refill time (r = 0.85, P <.001). The total volume of blood (mean ± SD) expelled per hour by the existing SCD Sequel device in the supine, semirecumbent, and sitting positions was 2.23 ± 0.90 L/h, 2.47 ± 0.86 L/h, and 3.28 ± 1.24 L/h, respectively. The SCD Response device increased the volume expelled to 3.92 ± 1.60 L/h or a 76% increase (P =.001) in the supine position, to 3.93 ± 1.55 L/h or a 59% increase (P =.001) in the semirecumbent position, and to 3.97 ± 1.42 L/h or a 21% increase (P =.026) in the sitting position. Conclusions: By achieving more appropriately timed compression cycles over time, the new SCD Response System is effective in preventing venous stasis by means of a new method that improves on the clinically documented effectiveness of the existing SCD system. Further studies testing its potential for improved efficacy in preventing deep venous thrombosis are justified. (J Vasc Surg 2000;32:932-40.

Improved hemodynamic effectiveness and associated clinical correlations of a new intermittent pneumatic compression system in patients with chronic venous insufficiency

AbstractPurpose: A new intermittent pneumatic compression device (SCD Response System) has recently been shown in healthy volunteers to have the ability to detect the postcompression refilling of the calf veins and to respond by initiating the subsequent cycle when these veins are full. This has proven to be more effective in expelling blood proximally than the conventional intermittent pneumatic compression device (SCD Sequel System). The aim of this study was to test the influence of venous disease on the postcompression refill time detected by means of the SCD Response and the effectiveness of the new system in expelling blood in patients who have venous reflux caused by post-thrombotic syndrome or varicose veins. Methods: This open, controlled trial was conducted in an academic vascular unit with 10 patients who had post-thrombotic syndrome and 10 patients who had varicose veins. The new SCD Response System was tested against the existing SCD Sequel System in both legs in the supine, semirecumbent, and sitting positions. The refilling time sensed by means of the device was correlated with the venous filling index by using air plethysmography. The total volume of blood expelled per hour during compression was compared with that expelled by the SCD Sequel System in the same volunteers and in the same positions. Results: An inverse association was found between the mean postcompression refilling time in the sitting position and the venous filling index of the apparently healthy or less severely affected leg (r = –0.52, P =.019), the refill time being significantly shorter in patients with advanced venous disease. The SCD Response System increased the volume expelled per hour in the post-thrombotic leg, when compared with the SCD Sequel System, by 109.9% (P =.005) in the supine position, by 85.1% (P =.009) in the semirecumbent position, and by 40.2% (P =.005) in the sitting position. The corresponding results in the more severely affected leg in patients with varicose veins were 71.9% (P =.005) in the supine position, 77.9% (P =.005) in the semirecumbent position, and 55.7% (P =.013) in the sitting position. Similar improved results were also found in the contralateral leg in both groups. Conclusions: The deflation settings of the new SCD Response System are able to be adjusted selectively, correlating with the physiological severity of chronic venous insufficiency. By achieving more frequent compression cycles, the new system is more effective than the current one in expelling blood proximally, confirming our earlier findings in healthy volunteers. Further studies testing a possible improved efficacy in preventing deep venous thrombosis in this high-risk group are justified. (J Vasc Surg 2001;33:915-22.

Mobile carotid plaques: The natural history of two asymptomatic and non-operated cases

AbstractWe Studied Two Cases Of Mobile Internal Carotid Artery Lesions In Symptom-FREE Patients. Both Cases Were Diagnosed By Means Of Routine Carotid Duplex Ultrasound Scanning, And Neither Patient Was Operated On. With Medical Therapy With Oral Anticoagulants, The Two Lesions Spontaneously Disappeared Without Any Clinical Sequel, And No Evidence Of Infarcts Was Shown By Means Of Repeated Computed Tomography Brain Scans. After Uneventful 2- And 3-YEAR Follow-UP Periods, There Was No Evidence Of Recurrence. This Is The First Published Data On Asymptomatic Mobile Carotid Lesions And Their Natural History That Shows A Benign Course In A Long-TERM Follow-UP Period. We Suggest That A Non-SURGICAL Approach May Be Considered Selectively In High-RISK Symptom-FREE Patients Who Have Mobile And Floating Internal Carotid Artery Lesions. (J Vasc Surg 1999;30:357-62.