Skin stress and blood flow in sitting paraplegic patients.

Sitting paraplegic subjects, tested on a hard seat at a location 2 to 3cm lateral to the ischial tuberosities, develop roughly the same median pressure values (range 52 to 60mmHg) as groups of normal subjects and hospitalized geriatric patients. However, median paraplegic and hospitalized geriatric shear values are roughly three times median normal values. Median rates of pulsatile skin blood flow volumes for sitting paraplegic subjects, while roughly equal to those of hospitalized geriatric subjects, are only one third those of comparable normal subjects.

Comparison of continuous and interrupted suture techniques in microvascular anastomosis.

A comparison of the continuous and the interrupted suture techniques, ten procedures each, was performed upon dogs using high frequency pulsed Doppler ultrasonography to monitor blood velocity. No statistically significant differences in the blood velocity profile were found between the two techniques. The pulsatility of the vessels after anastomosis was similar for both techniques. At follow-up examination, mean being 13 weeks, the patency rate was 100 per cent as demonstrated arteriographically for both the continuous and the interrupted techniques with statistically no significant difference in the blood velocity profile. The speed and the ease of completing a continuous anastomosis and its lack of significant hemodynamic differences compared with the interrupted technique speak well for the preferential use of the continuous suture technique.

Technique of venous impedance plethysmography for quantification of venous reflux.

A study was conducted applying a technique of venous impedance plethysmography for the quantitation of venous reflux to a group of 20 normal persons and five patients with postphlebitic limbs. Results demonstrate a significantly higher reflux refilling rate for those patients with postphlebitic limbs compared with the refilling rate for those in the normal group. It is believed that this technique is a valuable diagnostic tool for detecting venous reflux caused by valve incompetence and that it provides an indication of progression of venous insufficiency in the patient.

Skin blood flow in seated geriatric patients.

A hard seat was equipped with devices sensing arteriolar pulsatile blood flow volume rate, externally developed pressure, and shear, all taken in lateral proximity to the ischial tuberosities of sitting subjects. Tests of 14 geriatric hospitalized patients and 9 healthy young men indicated the following: (1) No young healthy man demonstrated blood flow occlusion at pressure values less than 120mmHg. Of the geriatric hospitalized subjects, 2 occluded at less than 20mmHg. (2) Average shear values developed by the geriatric hospitalized group were 3 times that of the young healthy group. (3) Average pressure values demonstrated by the geriatric hospitalized subjects were roughly equal to those of the younger subjects (roughly 70mmHg). (4) Tipping the seat backwards through 20 degrees produced major benefits to the hospitalized geriatric group in terms of increased blood flow, lessened pressure, and lower shear. The young, healthy group experienced some increase in blood flow with no significant change in sitting reactions when tested in a tipped attitude.

Noninvasive flowmetry in vascular surgery: use of a noninvasive electromagnetic flowmeter.

Using an in vitro model, the measurements made using a noninvasive electromagnetic flowmeter have been validated using standard square wave electromagnetic flowmetry. Clinically, the noninvasive electromagnetic flowmeter provides information as to the functional significance of vascular occlusive disease that is not available through other techniques, gives an accurate, quantitative measurement of the peak pulsatile blood flow through a limb, thus providing an index of tissue perfusion and therefore, the degree of involvement of the disease in the peripheral vascular system.

Noninvasive evaluation of peripheral arterial disease in the geriatric patient.

A progressive increase in the incidence of peripheral arterial occlusive disease is being observed in today's steadily aging population. In recent years, a number of simple noninvasive vascular techniques have become available for the diagnosis of peripheral arterial occlusive disease. These techniques provide the physician with physiologic information about the patient's peripheral circulation which permits discrimination between complaints compatible with the aging process and those indicative of an underlying disease state. This article reviews the noninvasive vascular diagnostic techniques that the authors found useful in evaluating the geriatric patient. These include oculoplethysmography. Doppler ultrasound, photoplethysmography, arterial impedance plethysmography, and electromagnetic flowmetry.

Noninvasive detection and prevention of deep-vein thrombosis in the geriatric patient.

Noninvasive methods for the early detection of, and prevention of deep-vein thrombosis can significantly reduce postoperative morbidity and mortality in the elderly due to venous thromboembolism. The technique of venous impedance plethysmography provides a rapid means of assessing the patency of the venous system by detecting changes in venous volume and maximum venous outflow, thus providing for early detection of deep-vein thrombosis. Prevention of deep-vein thrombosis can be accomplished through use of external intermittent pneumatic compression. This technique prevents venous stasis and stimulates the natural fibrinolytic activity of the vein-wall endothelium.

Use of noninvasive electromagnetic flowmetry in the assessment of peripheral arterial disease.

The need for noninvasive techniques capable of quantitating peripheral arterial insufficiency is becoming increasingly obvious. We have shown the technique of noninvasive elctromagnetic flowmetry to be capable of distinguishing three relatively discrete clinical zones by quantitating the peak pulsatile flow of blood through the thigh and calf. The obtained peak pulsatile flow values were in close agreement with ischemic index values previously reported as grading the degree of ischemia in a patient. In certain patients, the noninvasive electromagnetic flowmeter has yielded information not readily available from Doppler systolic pressure measurements. With the noninvasive technique of electromagnetic flowmetry and Doppler ultrasound, it is possible to confirm and quantitate patient complaints, follow disease progression and document improvement following arterial reconstructive operations. The noninvasive electromagnetic flowmeter has also been shown to be invaluable in the selection of the operative procedure by providing information about arterial run-on, run-in and run-off.

Monitoring of heparin therapy with thromboelastography.

The technique of thromboelastography was used to monitor the administration of heparin to patients with diagnosed deep vein thrombosis. The thromboelastograph uses a mechanical optical system to provide a continuous dynamic measure of the coagulation process. It has been found to be a highly sensitive device for the detection of response to heparin thus allowing a more precise administration of heparin frequently leading to a reduction in the dosage to maintain the coagulation process of the patient within therapeutic range. This allows a more individualized approach to the patient on anticoagulation therapy.

Intraoperative assessment of intestinal viability with Doppler ultrasound.

Following preliminary experimental animal studies showing Doppler ultrasound to be reliable in predicting intestinal viability and to correlate well with subserosal thermistor thermometry measurements, the Doppler technique has been used clinically for intraoperative intestinal viability assessment in colon-esophageal bypasses and colonic resections. Our clinical experience has shown Doppler ultrasound to be far superior to traditional predictive criteria. The presence of good Doppler sounds confirms adequate collateral pulsatile blood flow ensuring viability of the intestinal segment, whereas the absence of Doppler sounds indicates the need for appropriate revascularization. Based on the reliability of Doppler ultrasound, its simple technique and its relative inexpensiveness, we recommend the routine use of Doppler ultrasound for the evaluation of the quality and adequacy of intestinal blood flow in predicting the viability of a segment of the intestine.

Noninvasive hemodynamic evaluation in selection of amputation level.

Various noninvasive techniques of hemodynamic evaluation have been used to determine the optimal level of amputation. Noninvasively obtained measurements of pressure and blood flow in the lower extremity have been found to be reliable in predicting the probable healing of an amputation. In patients with severely calcified noncompressible arteries, noninvasive electromagnetic flowmeter measurements of peak pulsatile flow provide a more accurate indication of the vascular status of the patient than do blood pressure measurements which, in such patients, frequently exceed 300 millimeters of mercury. Skin thermistor thermometry does not appear to be applicable in patients with extensive severe ischemia of the leg. The need for a reliable method of determining the lowest possible level of amputation is well recognized. Such factors as wound edge bleeding and clinical judgment too often lead to above the knee amputation when, frequently, a more distal amputation could have been possible. Our experience has shown that noninvasive techniques for hemodynamic evaluation are a valuable aid to clinical judgment in determining accurately the lowest level for successful limb amputation.

Shear vs pressure as causative factors in skin blood flow occlusion.

An instrument was developed to measure the external pressure, shear, and pulsatile arteriolar blood flow existent at a given portion of the anatomy. Application of this device to the thenar eminence of 4 healthy subjects showed that externally applied pressure was approximately twice as effective as shear in reducing pulsatile arteriolar blood flow. The combination of pressure plus shear was found particularly effective in promoting blood flow occlusion. At a sufficiently high level of shear (roughly 100 g/cm2) the pressure necessary to produce occlusion was half that required when little shear was present.

Management of severe ischemia of the foot secondary to occlusive vascular disease.

One hundred patients, 111 limbs, with gangrene of the lower extremity were initially treated with lumbar sympathectomy. Lumbar sympathectomy appears to be most beneficial in the management of gangrene of the toe with a limb salvage rate of 75 per cent. The best results were seen when only one toe, not the big toe, was involved. Limb salvage dropped to 38 per cent for gangrene of the foot, and with gangrene of the leg, lumbar sympathectomy had no affect. The presence of diabetes had no affect on limb salvage for gangrene of the toe but did have an apparent affect on limb salvage for gangrene of the foot. Sympathectomy appeared to aid in stump healing, with 77 per cent of the amputations done not requiring revision to a higher level. Results of our experience appear to indicate that, for patients presenting with gangrene of the toes or forefoot who are not candidates for reconstructive arterial procedures, lumbar sympathectomy as an initial operative procedure should be given serious consideration.

Assessment of the healing potentials of ulcers of the skin by photoplethysmography.

An objective method of assessing the healing potentials of skin ulcers would eliminate the long waiting period necessary for visual evidence of healing or nonhealing to appear. This would permit the continued conservative treatment for healing ulcers and prompt surgical interventions for those ulcers which are nonhealing. In this preliminary study, the cutaneous blood flow immediately around the ulcer site was studied using the photoplethysmograph. Vigorous cutaneous blood flow shown by good pulsatile wave forms on the photoplethysmograph is shown to be indicative of an ongoing healing process in which spontaneous healing of the ulcer can be predicted. Ulcers with nonpulsatile wave forms fail to heal with conservative management. One patient with nonpulsatile wave forms at the ulcer site showed improvement and eventual healing of the ulcer after undergoing a lumbar sympathectomy. Thus, nonpulsatile blood flow shown by poor wave forms on the photoplethysmograph would suggest early surgical intervention. This method may also aid in determining the extent of surgical excision of the ischemic scar tissue surrounding the chronic skin ulcer.

Evaluation of modified human umbilical vein as an arterial substitute in femoropopliteal reconstructive surgical procedures.

Modified human umbilical vein allografts tanned with glutaraldehyde and encased in a polyester mesh were used as arterial substitutes in 13 femoropopliteal reconstructive procedures. A cumulative patency rate of 91 per cent has been obtained for the two year follow-up period. Two grafts were lost due to patient death from myocardial infarction. The grafts were determined to be patent at the time of death, and no death was in any way associated with the graft material. One graft occluded immediately postoperatively due to the absence of any significant distal runoff to the arteries of the calf. There has been no incidence of aneurysmal formation, and based upon our previous experience with bovine artery heterograft, the modified human umbilical vein appears to be superior in this respect. Modified human umbilical vein allograft is superior to autogenous saphenous vein in that it is immediately available, valveless, branchless and may be specially constructed as to diameter and length. We have found the allograft to be flexible, easy to handle and suture, and of sufficient length, elasticity and compliance. Our cumulative patency rate for the two year follow-up period compares favorably with that of previously reported uses of autogenous saphenous vein in femoropopliteal arterial reconstruction. Those results show the modified human umbilical vein allograft to be well deserving as an alternative to autogenous saphenous vein in femoropopliteal arterial reconstructive procedures.