A haemodynamic evaluation of the femoro-femoral cross-over bypass

The femoro-femoral cross-over bypass has become a popular choice for the management of unilateral iliac artery disease, being used in preference to aorto-femoral or extraperitoneal ilio-femoral bypasses. It is a relatively minor procedure and associated with a small incidence of side effects, the main one being the risk of development of a steal of blood from the donor limb by the bypass. Although this problem has been widely discussed, haemodynamic studies have been limited by the use of indirect measurements of blood flow, such as ankle systolic pressures or by the use of electromagnetic flowmetry at the time of surgery. No study employing volumetric blood flow measurements to identify and quantify blood steal in the postoperative patient has been reported to date. With aims of studying the haemodynamic effects of a femoro-femoral cross-over bypass on the circulation in both the recipient and donor limbs, and of identifying preoperatively, problems likely to lead to haemodynamic problems or to graft failure, the present study of 31 patients undergoing femoro-femoral bypass was undertaken. The patients, 18 of whom had rest pain and 13 intermittent claudication, were studied preoperatively using arteriography and a non-invasive assessment. At 3 months from the operation, all received a clinical assessment and a further non-invasive assessment, including a measurement of blood volume flow. Flow measurements were made in the bypass at rest and during a reactive hyperaemia test. In addition, flow measurements were made in the donor limb below the bypass origin at rest and during hyperaemic testing of the recipient limb in order to assess any steal effect the bypass might cause to the donor limb circulation. All 31 patients were improved by surgery, but five developed donor limb claudication which was attributed to steal in three cases. Resting blood flow in the bypasses, 161 (65-282)ml/min [median (range)], rose by 116% (5-428%) to 300 (82-1114)ml/min after hyperaemic testing. Simultaneously, bypass hyperaemia caused a fall in donor limb blood flow of 32% (0-74%). Of the preoperative non-invasive tests, only donor femoral artery pulse rise time was related to the later development of objective evidence of steal. Successful Gruntzig dilatation of four major stenoses resulted in a satisfactory outcome.     

Venous bypass for surgical resection of renal carcinoma invading the vena cava: a new approach

A new technique is described which facilitates the surgical removal of renal carcinoma from the inferior vena cava. The use of cardiopulmonary bypass with or without cardiac arrest has been advocated but with this procedure only the inferior vena cava is bypassed, using femoral and right atrial cannulation, assisted by a closed system electromagnetic centrifugal pump. In appropriate cases this less complex technique allows prolonged access to the inferior vena cava whilst providing equal protection from pulmonary embolisation and tumour dissemination; it also reduces morbidity, operating time, difficulty and cost when compared with cardiopulmonary bypass.     

Electromagnetic blood flowmetry in small vessel surgery. An experimental study.

The aim of this work was to study problems in microvascular flowmetry. Special emphasis was placed on the meticulous preparation of the vessel wall in order to improve zero-line stability and on the problems related to the calibration of small electromagnetic flow probes. Electromagnetic flow probes with an inner diameter of 2, 1.5 and 1 nm were used for studies on zero-line drifting and for calibration procedures in a series of rats and rabbits. Principles and tools derived from microvascular surgery, including the binocular microscope, were employed in the preparation of the vessel wall and in the application of the probes. The results obtained indicate an improvement in flow uptake and in zero-line stability following this procedure. Precalibration of small flow probes using laboratory animals should be considered if calibration is not feasible at the time of the flow measurement. Use of the microsurgical technique for vessel preparation is recommended.     

Single-cannula venovenous bypass for respiratory membrane lung support

Clinical use of a single cannula would make extracorporeal membrane oxygenation simpler and less aggressive. It would probably limit the occurrence of the complications of currently used techniques (double-cannula, venoarterial, or venovenous bypass). In this experimental study an original system is described that is composed of a single cannula, an alternating clamp, and a nonocclusive roller pump, the characteristics of which permit its use as a venous reservoir. To overcome the limitations of the oxygenation in any venovenous bypass, we used the method of "apneic oxygenation" through the natural lungs, which we previously proved efficient in infants and children. The optimal setting of the alternative clamp was first tested in vitro to obtain the maximal flow in the circuit and the minimal amount of recirculation. The single-cannula bypass then was compared with a two-cannula circuit regarding the efficiency of carbon dioxide removal and the hemodynamic consequences. At less than 50% of the maximal speed of the pump, flows were equivalent in both types of circuits. The efficiency of carbon dioxide removal was only slightly decreased by the use of a single cannula (30 +/- 2 ml/min versus 36 +/- 2 ml/min with two cannulas). This could easily be offset by increasing the gas flow/blood flow ratio in the oxygenator. Arterial carbon dioxide tension was maintained at normal levels in both types of circuits. Hemodynamic condition was only slightly affected by the alternative flow of the bypass. This system of single-cannula membrane lung support thus seems to be adequate for clinical use.     

Reliability of intraoperative flow measurements to determine early graft patency with simultaneous introduction of a new method for distal coronary artery run-off capacity

Intraoperative measurements of blood flow were made in 44 patients in whom a total of 112 venous bypass grafts were inserted. Blood flow through the graft was measured by a standard electromagnetic device as well as by a new method, consisting of a roller pump run-off system. At an average of 5 months after operation all patients underwent control coronaro-angiography. Overall patency-rate was 86.6%. Using the standard method mean flow in the patent grafts was 78 ml/min and 39 ml/min in the occluded grafts. Using the new run-off method mean flow in the patent grafts was 142 ml/min and 78 ml/min in the occluded grafts. It is concluded that measuring distal coronary artery run-off capacity provides a reliable index for predicting patency rate. For several reasons roller-pump run-off measurement has advantages over the generally used electromagnetic measurements.     

Postoperative Blood Flow Measurements In Man By The Use Of Implanted Electromagnetic Probes

Intra- as well as postoperatively the blood flow through in situ bypass vein grafts in the thigh were studied by the use of implanted electromagnetic flow probes. The quantities of blood flow found at intra-operative measurements was a good indication on the postoperative blood flow within the individual case. The effect of exercise, papaverine injection and postural changes were also studied.     

Usefulness of sequential bypass technique in arterial reconstruction

Although sequential bypass grafting has been recommended for surgical treatment of lower limb ischemia in patients with complex multisegmental arterial occlusion, hemodynamic evaluation of the sequential bypass procedure remains to be resolved. The present study was undertaken to evaluate the sequential bypass operation to assess its usefulness from the standpoint of hemodynamics. A model was made simulating a sequential bypass in the mongrel dogs, and blood flow through the sequential bypass graft much more increased than through the standard one, measured by an electromagnetic flowmeter. By flow visualization in a glass tube model, type of flow separation and stagnation region in case of a side-to-side anastomosis was similar to those in case of an end-to-side one. The stagnation area at the anastomotic site was widened when the vascular resistance increased in the ramified vessel which corresponded to the host distal artery. It was considered reasonable to blockade the retrograde blood flow through the anastomotic site by ligating the host artery proximal to the anastomotic point when the retrograde blood perfusion was unnecessary. Clinical results of 21 cases with the sequential bypass grafting were presented and the usefulness of the technique was discussed from a hemodynamic viewpoint.     

Improvement in blood flow through a critical arterial stenosis by defibrination with ancrod.

Using electromagnetic flow probes, cardiac output and hind limb blood flow were measured in dogs in which one hind limb had been rendered ischemic. Four dogs served as controls; seven were defibrinated by intravenous infusion of ancrod, 1 unit/kg, over a 30-minute period. In both groups, hematocrit readings remained constant, but cardiac output fell (this was attributed to barbiturate anesthesia), as did flow in the normal hind limb. In the controls after three hours, flow in the ischemic hind limb had decreased by 34%, but in the treated animals it had increased by 20%. The difference was statistically significant (P less than .001). The selective increase in blood flow in the ischemic limb may be explained by the greater reduction in blood viscosity at low shear rates achieved by defibrination.     

The use of electromagnetic flow measurements for detection of early stenosis in aortocoronary bypass grafts

The value of electromagnetic flow measurements for the detection of graft stenosis during aortocoronary bypass and subsequent prevention of early closure by reimplantation of the graft was assessed. Postoperative angiograms were studied in 102 grafts in 55 patients in whom flow was measured during operation. Patients with recurrent angina or insufficient improvement after operation were selected to include many early occluded grafts; 30 grafts became occluded within six months. Applying a criterion of acceptable specificity based on flow pattern analysis, only 6 grafts were found to be abnormal immediately after implantation. It appears that in most instances, early closure is caused by a process of scar tissue formation which takes several months to develop completely. As a rule, the graft is patent after implantation and flow pattern analysis has nothing to offer. The value of flow pattern analysis during operation for the prevention of early closure is limited, and its value for the prediction of long-term prognosis of the grafts remains to be evaluated.     

Laparoscopic Gastric Bypass, Roux en-Y - 500 Patients: Technique and Results, with 3-60 month follow-up

Background:The authors have performed the laparoscopic gastric bypass since 1993 and perform about one-half of bariatric cases laparoscopically. Since our initial report, several groups throughout the world have preformed the gastric bypass laparoscopically, with various modifications. Method: Prospectively, we followed and recorded the results of our laparoscopic patients. A detailed pre- and post-operative analysis of the patient's co-morbidities is performed as well as complete weight and laboratory data evaluation. Results:With > 80% follow-up, we found an excess weight loss of about 80% by the first year. This degree of loss is well sustained. Over 95% of the significant pre-operative co-morbidities are controlled. Conclusion: The laparoscopic gastric bypass has been refined over 5 years of use. Though we have not changed the basic operation as we originally described, others have modified the various anastomotic techniques. The weight loss results are very good to excellent, with patients now out to "long-term" follow-up. Resolution of the co-morbidities is documented. The operation has an adequate track record to show effectiveness, and training programs should be established to maximize safety.     

A new technique for double lung transplantation. "The bilateral single lung transplantation". Apropos of ten operations]

The technique of enbloc double lung transplantation described by the Toronto team, with cardiopulmonary bypass, cardioplegia, and tracheal suture is complicated by problems of tracheal anastomosis for its authors. Single lung transplantation has a more straight forward postoperative course and bronchial complications are moderate. We present a new technique of lung transplantation, the "bilateral single lung transplantation". It consists, via a single anterior horizontal incision, of successively performing two single lung transplantations without bypass. This operation has been performed ten times since November 1989. As expected, bronchial healing has been excellent.     

Electromagnetic measurement of the arterial blood flow in the femoropopliteal region.

To determine the blood flow in healthy femoral arteries electromagnetic measurements were made on common femoral, superficial femoral and profunda femoris artery in 20 patients during operation for varicose veins. The values obtained were 239 ml/min, 134 ml/min, and 104 ml/min respectively. These registrations were compared with those achieved during reconstructive arterial surgery. It was found that the average basal flow values from corresponding arteries were rather similar. The flow values registered from femoropopliteal bypass grafts were identical with the flow values from the superficial femoral artery of varicose patients. The papaverine response of the common femoral artery flow was tested in 7 varicose patients. The average increase was 250%. None of the average responses from various arteries during arterial reconstructive surgery reached this value. The papaverine responses in femoropopliteal bypass grafts were closely correlated with the arteriographically estimated outflow potential. The flow values both at rest and during vasodilatation showed a great range in all vessels measured.     

Transcutaneous quantitation of arterial flow with ultrasound

Arterial blood flow was measured in dogs simultaneously with electromagnetic flow probes and with ultrasonic "flow probes." The ultrasonic probes were used to determine transcutaneously the mean velocity of arterial flow and the cross-sectional area of the blood vessel. A 10 MHz probe was used for blood vessels 1 cm deep or less, while a 5 MHz probe was used for vessels between 1.0 and 2.5 cm deep. The correlation coefficient between the flow calculated with the ultrasound method and the flow measured with the electromagnetic flow probes was 0.966, p less than 0.01. Blood flow was also measured intraoperatively in five patients. There was a correlation coefficient of 0.999, p less than 0.01, between the flow obtained with the ultrasound method and that determined simultaneously by the electromagnetic flow probes. The coefficient of determination for the regression of electromagnetic-determined flow on ultrasound-determined flow was 0.99. Thus, accurate transcutaneous determination of blood flow is possible with slightly modified ultrasound equipment.     

Second generation shock wave lithotripsy: experience with the lithostar

Summary Extracorporeal shock wave lithotripsy (ESWL) has been in clinical use for more than 5 years. Several devices commonly designated second generation lithotriptors are now under experimental or clinical trials. A multifunctional lithotriptor unit developed in cooperation with the Siemens Company in Germany is described, which utilizes an electromagnetic mode of shock wave generation along with local coupling to the patient. The results of 795 treatments are presented. The prototype has been in operation since March 1986. Adjuvant endourological measures, all of which have been performed on the same table, include insertion of double-J stents and ureteral catheters prior to ESWL in 27% of all treatments. Shock wave lithotripsy alone has been performed successfully under local anesthesia or a combination of parenteral analgesia and sedation. Results of treatment have been uniformly satisfying.     

In favor of the Y-graft for aortocoronary bypass.

The technique of multiple coronary artery bypass grafting has included separate conduits, snake grafts, and Y-grafts. Against the Y-graft have been reports of lesser patency and several theoretical objections. The theory is discussed and a laboratory model presented which demonstrates a flow difference of 2 ml/5 sec or less between Y-grafts and single grafts. In conjunction with this, 171 patients having aortocoronary bypass were analyzed and showed a combined one-year graft patency of 77% with no significant difference between single grafts and Y-grafts. It is concluded that the technical simplicity of Y-grafts is advantageous and that, if the operation is performed within the guidelines set forth, revascularization with Y-grafts is an acceptable method.     

Clinical investigation on the adjunctive method in the surgery of thoracic aortic aneurysms--comparison of the temporary bypass and partial extracorporeal bypass]

Since 1980, two different operative strategies were employed during resection to provide distal aortic perfusion by temporary bypass (Group "TB", 39 patients) or partial extracorporeal bypass (Group "PEC", 39 patients) in the operation for the thoracic descending aortic aneurysms or the dissecting aortic aneurysms with DeBakey type III. No significant differences were found in the patient population or the operative procedures between two groups. Mean bypass flow in Group "PEC" was 1850 +/- 70 (ml/min), which is significantly higher than in Group "TB" (1000 +/- 240 ml/min). However, there were no significant differences in the distal aortic pressure between two groups, which was due to administration of vasodilators. Platelet counts in Group "PEC" were significantly lower in the postoperative courses, probably caused by the use of roller pumps or suckers. The incidence of the postoperative renal dysfunction was almost the same in two groups. Cardiac functions during temporary bypass were suppressed by the aortic cross-clamping, therefore, it is necessary to evaluate the cardiac function preoperatively in employing this method. Partial extracorporeal bypass has the disadvantages of the requirement for full heparinization, but it can be indicated to almost all cases, even to the patients with poor cardiac function. It also has the advantage to maintain the distal perfusion in the unexpected intraoperative situations. The method of distal aortic perfusion should be determined by patient-related and disease-related factors.     

Measurement of blood flow rates in the lower extremities with use of a nuclear magnetic resonance based instrument

Direct, noninvasive measurement of pulsatile blood flow to the human extremity is now possible by means of a flow measurement instrument that is based on the principles of nuclear magnetic resonance. The instrument uses a physically independent calibration module as a primary calibration standard. Volumetric calibration of this module indicates that it is precise and accurate over the range of 0 to 100 ml/min. The calibration module is used, in turn, to calibrate an electromagnetic flow sensor that is incorporated into the instrumentation. The calibration module and the electromagnetic sensor were found to be linearly related over the range of 5 to 100 ml/min, with a regression correlation coefficient of 0.996. The calibrated electromagnetic flow sensor is used as a secondary standard for calibration of the nuclear magnetic resonance sensor. Blood flow measurements, obtained by use of this method, agree closely with those obtained by plethysmographic methods. They differ from the plethysmographic results in that magnetic resonance flows will distinguish between the at-rest blood flow in the normal extremity and the flows seen in the extremity (also at rest) with claudication. Based on the results obtained from studying a limited number of limbs with a high degree of ischemia, the method will not distinguish the limb with ischemia from the limb with claudication. Limitations of the method and refinements required to make the method clinically useful are discussed.     

Concomitant coronary artery revascularization and right pneumonectomy without cardiopulmonary bypass

Combined coronary artery bypass grafting (CABG) and pneumonectomy has a high morbidity and mortality rate, especially when the right lung has to be removed. A patient is described who underwent a CABG operation through a midline sternotomy without the use of cardiopulmonary bypass (CPB), and a right pneumonectomy through a right lateral thoracotomy in one operative session. To our knowledge, this is the first case in which this operative strategy was employed. CABG operations without the use of CPB might put concomitant lung surgery in a new perspective.     

Reduction of coronary flow in the native circulation after bypass. Observations in a hydraulic model of the cardiovascular system.

The effects of aorta-coronary bypass upon flow in the native coronary artery were investigated in a hydraulic model of the cardiovascular system. An aorta-coronary bypass with a diameter identical to the coronary artery was used, since a graft diameter-to-coronary diameter ratio of one has been described as optimal. Stenoses of increasing severity were created in the simulated coronary artery. Aorta-coronary bypass eliminated the pressure gradients across the stenotic coronary segments. This caused a 50% reduction of flow in the normal or mildly stenotic native coronary artery. A higher percentage reduction of flow occurred in the bypassed artery when it was severely stenotic. Such a reduction of flow in patients may accelerate the atherosclerotic-thrombotic process and contribute to the high prevalence of occlusion of natural vessels following bypass. This disadvantageous hydraulic circumstance should be considered, particularly when bypass of mildly stenotic vessels is contemplated.     

Coronary Artery Bypass Grafting: Simplification and Refinement of Surgical Technique

Recent advances in technique and myocardial preservation that I have used in performing the coronary bypass operation are described. Rigid adherence to basic microsuture technique and use of hypothermic hyperosmolar cardioplegic solution and wide-field optical magnification have been responsible for improving graft patency rates and markedly reducing operative mortality during the past six years. With these techniques, hospital mortality has been 0.6% (3 deaths) in the last 500 consecutive coronary bypass operations.