Detection of outflow obstruction in chronic venous insufficiency

PURPOSE

This study compares three different modes for measuring hemodynamically significant outflow obstruction in chronic venous insufficiency: (1) arm-foot venous pressure differential combined with foot venous pressure elevation to reactive hyperemia, (2) outflow fraction determination with plethysmography, and (3) calculation of resistance from simultaneously obtained foot venous pressure and calf volume curves.

METHODS

The three techniques were compared in 15 normal limbs and 19 limbs with documented previous deep venous thrombosis. Outflow fraction and resistance were also measured after reactive hyperemia was induced.

RESULTS

The arm-foot venous pressure measurements delineated patients with grades 1 through 4 obstruction (Raju's grading). Resistance calculations correlated well with this grading except in patients with severe grade 4 obstruction, in whom low resistance was found. Outflow fraction determinations had marked overlapping between the different obstruction grades, substantially decreasing sensitivity to detect hemodynamically important outflow obstructions. No correlation with the resistance calculations was shown. Inducing reactive hyperemia did not alleviate these findings. The failure of the outflow fraction and resistance methods to detect significant obstruction is probably attributable to the use of plethysmographic techniques for volume measurement, which appears to give false-negative results as a result of a regional volume shift within the lower limb.

CONCLUSIONS

The combination of the arm-foot vein pressure differential and the foot vein pressure elevation after reactive hyperemia seems to be the only reliable test currently available for detecting and grading global chronic obstruction.

A rational approach to detection of significant reflux with duplex Doppler scanning and air plethysmography

PURPOSE

Several techniques are currently available for the detection of venous reflux. We have attempted to determine the relative value and accuracy of available techniques to develop a logical strategy of investigation in reflux venous insufficiency.

METHODS

The morphologic distribution of venous incompetence (erect duplex and descending venography); the results of ambulatory venous pressure measurement, venous refilling time, the Valsalva test, and air-plethysmography (venous refilling index, VFI); and the clinical severity were described in 118 consecutive limbs. In an attempt to validate the tests, results were correlated with the clinical severity classification (class 0, n = 34; class 1, n = 42; class 2, n = 11; class 3, n = 31) and with a standardized quantification of reflux (multisegment score) as seen on standing duplex Doppler scanning with rapid deflation cuffs.

RESULTS

Twenty-nine percent of limbs with severe venous disease (class 2/3) had pure deep insufficiency, only 6% had pure superficial disease, and the remainder had a combination. A history of previous thrombosis and the presence of posterior tibial vein incompetence were markedly common with ulcer disease (84% and 42%, respectively). The duplex Doppler multisegment score correlated strongly with clinical severity classification (r = 0.97). The venous refilling time and VFI had the highest sensitivity in identifying severe venous disease (class 2/3), and the ambulatory venous pressure had excellent specificity.

CONCLUSIONS

For noninvasive determination of reflux, the combination of VFI and duplex scanning not only localized reflux but also separated severe clinical vein disease from mild, with high sensitivity and specificity. Air plethysmography may also provide valuable information regarding calf muscle pump and outflow obstruction.

Observations on the calf venous pump mechanism: determinants of postexercise pressure

PURPOSE

We investigated the factors determining postexercise pressure and the relationship of venous valve closure and venous column segmentation to ambulatory venous pressure changes.

METHODS

Valve closure and venous segmentation were observed during dynamic ascending phlebography in 40 nonrefluxive limbs and by duplex imaging in 25 normal limbs in healthy volunteers. Simultaneous volume (air plethysmography) and pressure studies during calf exercise were also carried out. Some studies used a simple mechanical model comprised of a collapsible latex tube ("calf pump") and a graduated "popliteal" valve.

RESULTS

The femoropopliteal venous column above the popliteal valve remains unsegmented and continuous during ambulatory venous pressure changes in response to calf muscle contraction. Therefore ambulatory venous pressure changes cannot be explained purely on the basis of hydrostatic column pressure changes. Postexercise pressure appears to be determined by a complex set of factors: (1) physical segmentation of the venous column below the popliteal valve (i.e., tibial valve closure); (2) tube collapse below the closed valve, which further aids in the breakup of the hydrostatic column pressure and dampens the effect of any reflux through or around the closed valve; (3) ejection fraction, which influences the degree of tube collapse; and (4) the interaction of the resultant pressure forces with the wall properties of the venous pump.

CONCLUSIONS

The mechanism of ambulatory venous pressure reduction is complex and multifactorial. The importance of venous wall characteristics as a determinant of postexercise pressure has not been previously appreciated. Changes in venous wall property after a thrombotic process, for example, could conceivably influence ambulatory venous pressure and recovery time in the absence of reflux.

A comparison between descending phlebography and duplex Doppler investigation in the evaluation of reflux in chronic venous insufficiency: a challenge to phlebography as the "gold standard"

To evaluate venous reflux in 56 lower limbs of 32 consecutive patients, hemodynamic tests, ascending and descending phlebography, and supine and erect quantitative duplex scanning were performed and the clinical severity was classified (class 0 = 15, class 1 = 19, class 2 = 8, and class 3 = 14). Of the 56 lower limbs, 22 (40%) had severe swelling and hyperpigmentation with or without ulcer (classes 2 and 3). Adequacy of the clinical severity classification was supported by the hemodynamic results. Radiologic and ultrasound findings were described by axial grading, multilevel/multisystem point, and multisegment scoring systems. Applying these evaluation systems, the phlebographic and scan results correlated poorly. There was no relationship between the radiologically obtained average reflux grade or points and the clinical severity. An erect quantitative duplex Doppler test assessed by the multisegment scoring system correlated best with the severity classification. The predictive value of this test to diagnose severe reflux leading to severe symptoms (classes 2 and 3) was 77% compared with 35% to 44% for descending phlebography. The study suggests that erect quantitative segmental duplex Doppler reflects the degree and distribution of venous reflux more accurately than does descending venography.

Outpatient vascular access surgery: impact of a dialysis unit-based surgical facility

The present report describes a novel approach to vascular access surgery based on the philosophy that a readily available operating room, staffed by nurses familiar with the unique problems of dialysis patients and their therapy, would reduce dialysis delays and maintain the quality of surgical care. Based on a 28-month experience with more than 1,000 access cases, we conclude that a traditional surgical setting is not necessary for either quality access graft placement or the management of access complications.

Venous obstruction: an analysis of one hundred thirty-seven cases with hemodynamic, venographic, and clinical correlations

One hundred thirty-seven limbs with venous obstruction were analyzed. The arm/foot venous pressure differential and reactive hyperemia tests were found to be useful techniques to diagnose and grade venous obstruction. Traditional techniques including venography and ambulatory venous pressure are inferior in this regard. The newer techniques have provided newer insights in venous obstruction which are detailed herein. The hand-held Doppler was surprisingly very sensitive in grade I as well as in more severe forms of obstruction. Neither anatomic locale of obstruction nor its extent determined hemodynamic severity. Extensive proximal lesions could be hemodynamically mild, and conversely distal crural obstructions and single segment lesions could be hemodynamically severe. Phlebographic appearance was a poor index of collateralization. The paradoxical venous pressure response to the reactive hyperemia test in grade IV obstruction was found to be due to suppression or delay of the reactive hyperemia response itself in the presence of severe venous obstruction. The pain of venous claudication may be related to this phenomenon. Skin ulceration in the presence of venous obstruction was related to the associated reflux rather than the hemodynamic severity of the obstruction itself. The Linton procedure was found to be useful in treating such skin ulcerations. After perforator disruption, obstruction did not become hemodynamically worse, but reflux as measured by the Valsalva test improved with ulcer healing. The improvement in reflux related to Valsalva offers for the first time a hemodynamic rationale for the Linton procedure.

Hemodynamic basis of stasis ulceration--a hypothesis

Approximately 25% of patients with stasis ulceration have normal or below normal ambulatory venous pressures. A reflux index was calculated by multiplying postexercise pressures by Valsalva-induced foot venous pressure elevation. In patients with stasis ulceration, reflux index was found to have an excellent negative predictive value with a clear discriminant line between normal limbs and those with ulcers. Increasing incidence of stasis ulceration was demonstrated with increasing reflux index value. Even when ambulatory venous pressure was within the normal range, the index was found to be abnormal in ulcerated limbs because Valsalva-induced foot venous pressure was elevated in these limbs. Conversely, some patients with stasis ulceration and normal Valsalva foot venous pressure elevation were found to have abnormal ambulatory venous pressure values, yielding an elevated reflux index. Preliminary analysis indicates that reflux index may be a better predictor of surgical outcome after valve reconstruction procedures than either ambulatory venous pressure or Valsalva-induced foot venous pressure elevation. The concept of reflux index is a hypothesis that attempts to explain inconsistencies observed in implicating ambulatory venous hypertension as the sole determinant of venous reflux.

Host immunosuppression following orthotopic bowel allotransplantation in rats using low-dose cyclosporine

This study shows that Le rats bearing total bowel allografts treated with CyA (5 mg/kg for 14 days) demonstrated within one month immunological unresponsiveness to donor and third-party alloantigens as determined by MLR responses. Assays performed in long-term survivors (greater than 100 days) showed a continued depressed MLR response to antigen-specific (BN) alloantigens. The response to third-party (ACI) alloantigens was not significantly depressed. After the long-term bowel recipients rejected donor skin grafts, the MLR responses were increased over control, but the transplanted bowel remained intact.

Tension pneumopericardium as a complication of single-lung transplantation

Tension pneumopericardium is distinctly uncommon in the adult population. We present a case of tension pneumopericardium as a complication of lung transplantation in a 54-year-old woman with thromboembolic pulmonary hypertension who underwent single-lung transplantation.

Evaluation of methods for detecting venous reflux. Perspectives in venous insufficiency

Using 793 limbs with nonobstructive venous reflux, we evaluated a number of techniques used for the assessment of venous reflux. The venous Doppler examination was found to be a reliable screening tool with excellent sensitivity and good specificity. Photoplethysmography was 97% sensitive in patients with ambulatory venous hypertension; however, in milder forms of reflux, it was less sensitive. The major drawback of photoplethysmography was the large number of false-positive results obtained. Ambulatory venous pressure measurement and another pressure-based technique, Valsalva-induced foot venous pressure measurement, defined overlapping but different normal and abnormal limbs. Descending venography, when performed as described by Kistner et al, was found to be a reliable tool to assess reflux with more than a 90% sensitivity. The horizontal technique of performing descending venography and nucleotide descending venographies had unacceptably low sensitivity and were abandoned. Features of venous reflux as outlined by these modern technical tools are described.

A prospective randomized evaluation of chronic peritoneal catheters. Insertion site and intraperitoneal segment

The insertion site (midline or through the lateral rectus muscle) and type of chronic dialysis catheter (straight or spiral intraperitoneal segment) were evaluated in a prospective randomized trial. Dialysis catheter complications and catheter survival were the endpoints of evaluation. Eighty-five first catheters were evaluated. Neither race, gender, renal diagnosis, type of catheter, nor insertion site was a determinant of dialysis catheter survival. Overall median catheter survival was 308 days. There were 40 catheter complications (70%, n = 28) that occurred during the first 61 days following insertion. Median time to the first complication occurring within the first 61 days was 3 days. Late catheter removals were due to peritonitis episodes that failed to resolve. Complications are frequent with peritoneal dialysis catheters, and care of the peritoneal dialysis catheters requires constant vigilance.

Single- and double-lung transplantation. Problems and possible solutions

There is a resurgence of interest in single- and double-lung transplantation for end-stage disease. An experience with six double-lung and three single-lung transplants is reported. The lungs were procured from a distance of up to 600 miles and the heart was shared with another team for transplantation in seven of nine instances. The operative mortality rate was 33%. Early transplant infections of donor origin were lethal. Late transplant pneumonitis was well tolerated and recovery was the rule. Three of nine cases had significant tracheal suture line stenosis and were managed conservatively. A technique of bronchial artery implantation using a conduit tailored from donor aorta is described. Transplant rejection was easily diagnosed and treated. Other notable complications included occasional massive pleural fluid loss, temporary space problem, and a delay in the 'resetting' of chemoreceptors resulting in moderate post-transplant hypercarbia accompanied by episodes in which the patient felt hypoxemic despite the maintenance of excellent levels of blood gases. A comprehensive rehabilitation program begun before operation is essential for success.

Use of saturation mutagenesis to localize probable functional domains in the NahR protein, a LysR-type transcription activator

The NahR protein of the Pseudomonas naphthalene degradation plasmid NAH7 encodes a 300-residue transcription activator which is very similar to the NodD transcription activator of Rhizobium and other proteins in the LysR activator family. NahR binds to conserved sequences upstream (nucleotides -80 to -47) of the nah and sal promoters and activates transcription of genes for naphthalene catabolism in response to the inducer salicylate. Transformation of an Escherichia coli gal deletion strain (containing a sal promoter-galK fusion plasmid) with hydroxylamine-treated nahR DNA and selection on galactose/salicylate plates allowed isolation of 30 unique activation-deficient nahR alleles which fell into two classes: class I, defective in both activation and specific binding to the NahR activation site of the sal promoter; and class II, defective in activation, but with wild-type DNA binding activity. DNA sequence analysis showed that the amino acid substitutions eliminating DNA binding activity were mostly clustered in an NH2-terminal helix-turn-helix motif (residues 23-45) or a COOH-terminal domain (residues 239-291). Similar analysis of class II mutants identified a domain (residues 126-206) possibly involved in inducer binding and/or transcription activation functions. The partial trans-dominance of many mutant alleles and the size of NahR-specific DNA binding activity measured by gel filtration suggest that the active NahR protein may be a tetramer.

Chronic venous insufficiency: assessment with descending venography

Six hundred forty-four legs were examined by means of descending venography in patients with chronic venous insufficiency. Three patient positions (supine, 30 degrees semierect, and 60 degrees semierect) were used with a standard angiographic technique. Patients were also studied during either normal respiration or a Valsalva maneuver. The deep venous valvular system was incompetent more often than the superficial (saphenous) venous system. Positive venograms revealed that reflux occurred into the deep venous system alone in 82%, the superficial venous system alone in only 2%, and a combination of deep and superficial systems in 16%. The authors conclude that descending venography is best performed at the more physiologic 60 degrees semierect position and with the Valsalva maneuver, which enables evaluation of the competence of valves in the closed position.

A tribute to the late Dr. Ryo Shimazu: a chronic bowel allograft model in the rat

A chronic model of bowel allotransplantation is described. End-to-end microvascular anastomosis between superior mesenteric vessels was utilized. The recipient splenic vein was preserved to avoid postoperative pancreatitis. Euro-Collins solution was used to flush the vasculature in the lumen of the transplant. Low-dose cyclosporine was used for immunosuppression. With experience, 89% long-term survival was achieved.

Organ preservation injury in small bowel transplantation

Histological features of preservation injury were studied in a dog model of total small bowel transplantation. It was remarkable that substantial microscopic injury was evident during cold ischemia, unlike in other organ systems. This was early in onset and was related to the duration of cold storage. There was further progression of injury during reperfusion, as expected. Nevertheless, the small bowel was noted to have substantial ability to recover from this storage- and reperfusion-related injury. Histological features of damage and recovery are described in detail.

Experimental small-bowel transplantation: alternative strategies for graft prolongation

Alternative combined immunosuppressive therapy was tested in canine orthotopic bowel transplantation. Despite sporadic long-term survival, cyclosporine is still questionably effective. Triple-drug therapy (cyclosporine, azathioprine, and prednisone) combined with antilymphocyte serum or with a short segment graft was effective in reducing the early postoperative mortality due to acute rejection but did not alter the long-term survival rate. There was no apparent relationship between the serum cyclosporine levels and survival. The long-term survivors (longer than 100 days) maintained relatively low serum trough levels of cyclosporine. These suggest that orthotopic bowel transplantation in the dog, and probably in the human as well, requires improved immunosuppressive regimens.

99mTc penile scan: an investigative modality in priapism

A 99mTc penile scan was performed in 9 patients with priapism. The technique of the procedure is described. Penile scan is an easily obtainable modality that can differentiate between high- and low-flow forms of priapism. We believe that these scintigraphic findings facilitate management of priapism.

Dating the early pregnancy by sequential appearance of embryonic structures

A total of 97 transvaginal scans were performed from 4 to 12 weeks' gestation in normal and accurately dated gestations. The sequential appearance of six structures were examined: (1) the gestational sac only was present during week 4; (2) the yolk sac appeared in week 5; (3) the fetal pole with detectable heart motion was first seen in week 6; (4) the single unpartitioned ventricle in the brain marked week 7; (5) the falx cerebri appeared during week 9; and (6) the appearance and the disappearance of the physiologic midgut herniation were seen in week 8 and week 11, respectively. Inasmuch as the time in gestation at which these structures appear characterizes the gestational age more than any measurement at this age, we propose a practical method to determine the correct gestational age in early first-trimester pregnancy.