Thromboxane release after reperfusion of chronically ischemic limbs in patients.

We hypothesized that chronic ischemia of peripheral vascular disease would lead to increased thromboxane A2 (TxA2) and decreased prostacyclin (PGI2) production and surgical correction of the ischemia would stabilize TxA2 and PGI2 at normal levels. TxA2 and PGI2 concentrations were determined in 22 patients before, during, and after arterial reconstruction for limb salvage and in 10 control subjects. Control samples and preoperative patient samples had no detectable TxA2 or PGI2 (less than 26 pg/ml). Five minutes after reperfusion TxA2 increased (TxA2 = 76.27 +/- 48.9 pg/ml, mean +/- SEM) and persisted at 1 day (TxA2 = 190.1 +/- 80.1 pg/ml), 2 days (TxA2 = 224.7 +/- 131.7 pg/ml), 5 days (TxA2 = 334.8 +/- 272.8 pg/ml), and 7 days postoperatively (TxA2 = 256.6 +/- 149.0 pg/ml). Elevated TxA2 production was not associated with chronic ischemia of peripheral vascular disease. Reperfusion of the severely ischemic limb caused significant TxA2 release.

Retroperitoneal approach to the Warren shunt.

The Warren shunt, despite its recognized attributes, has several major obstacles to gaining widespread acceptance in the surgical community. These include its technical difficulty and the increased incidence of postoperative ascites. We have begun using a retroperitoneal approach for the performance of this procedure, which we believe is technically easier and may lessen postoperative ascites. In addition, blood loss, the need for ventilatory support and intensive care, and the occurrence of postoperative ileus have all been reduced in our experience. Herein, we have reported the details of this approach and discussed its major advantages over the classic transperitoneal approach to the distal splenorenal shunt.

Optimal management of tibial arterial trauma.

In an attempt to define optimal management, we have studied the outcome of 29 isolated tibial arterial injuries during the past 4 years. Twenty-five patients suffered blunt and four had penetrating trauma. Twenty-seven patients had preoperative arteriography which showed at least one interrupted tibial artery. In nine patients, immediate and successful reconstruction was done. Since the foot was viable in 20 patients, immediate reconstruction was not carried out in spite of the diagnosis of tibial arterial injury. Three of 20 underwent primary amputation. Fifteen of the remaining 17 patients required further angiographic evaluation for arterial reconstructions 2 to 12 months later for nonhealing of wounds, malunion of fractures, and soft-tissue defects. Delayed reconstructions were generally more complex. In 13 patients both viable and functional feet were eventually achieved. Bypass with autogenous vein was mandatory for success. Our experience has shown that most tibial arterial trauma will require immediate repair for success. Delayed repair was more difficult and was associated with substantial limb loss.

Management of pediatric visceral arterial and aortic coarctation.

Two unusual pediatric vascular problems have been managed surgically. The first patient is a five-and-a half-year old girl who presented with renal artery stenosis and aneurysm and renovascular hypertension. This was treated by excision of the aneurysm and reimplantation of the right renal artery. The second patient is a two-year old girl with atresia of the abdominal aorta, superior mesenteric artery (SMA) and both renal arteries. She was treated by PTFE patch graft angioplasty of the aorta, SMA reimplantation and bilateral aorto-renal autogenous saphenous vein bypass.

Intra-operative and post-operative flow in the in-situ saphenous vein bypass.

We have attempted to further define the hemodynamic properties of the arterialized in-situ saphenous vein. The natural taper of the vein and the presence of arteriovenous fistulas are two unique factors associated with this conduit. Utilizing intra-operative electromagnetic flowmeter (EF) measurements and post-operative duplex ultrasound scanning (DUS), we have studied the natural history of these conduits from the time of their arterialization. The EF mean arterial blood flow in 71 in-situ bypasses was 100.8 cc/ml, range 25-200. No significant correlation was found between these measurements and angiographic runoff, vein diameter, pre- or post-operative Ankle/Brachial Index (ABI) and site of distal anastomosis. Three immediate failures requiring revisions were not predicted by EF flow measurements. Using the unique combination of Doppler ultrasound measurement and real time imaging, afforded by the DUS, fistula flow was determined. These studies showed that terminal bypass segment blood flow is not significantly affected by cutaneous fistula interruption. We found that duplex ultrasound scanning is a useful tool ideally suited to the study of the arterialized saphenous vein in-situ. One of its main advantages is the ability to accurately localize the site and hemodynamic significance of any arteriovenous fistulas.

Duplex scanning of the internal carotid artery: an assessment of cerebral blood flow.

Duplex ultrasound scanning (B-mode imaging and pulsed Doppler shift analysis) was used to measure internal carotid artery blood flow (ICBF) in 20 volunteers. The effect of changes in end tidal CO2 on cerebral blood flow was measured. When corrected to a PCO2, of 40 torr (5.32 kPa) internal carotid artery blood flow was 286 +/- 16 ml min-1 (mean +/- s.e.m.). Specific CO2 reactivity (the change in flow per torr change in CO2) was 8.16 +/- 0.69 ml min-1 torr-1 which was equivalent to 2.0 +/- 0.1 per cent of the flow at 40 torr per torr change in CO2 (percentage CO2 reactivity). The mean value and the CO2 reactivity compare favourably with previously reported measurements by other techniques. These data suggest that the non-invasive measurement of internal carotid artery blood flow by Doppler ultrasound scanning is an assessment of cerebral blood flow that can be used to study both normal and pathological changes within the cerebral circulation.

The influence of anesthetic choice on carotid endarterectomy outcome.

This study compared the technique of general and regional cervical block anesthesia for carotid endarterectomy. Three hundred sixty-eight patients undergoing 399 carotid endarterectomies were administered one of these alternative anesthetics as selected preoperatively by each patient and his or her physician. In 242 cases general anesthesia was used. The other 157 cases were done under regional cervical block anesthesia. Perioperative mortality was 1.0%. Nonfatal strokes occurred in 1.25%. There were significantly more strokes in the general anesthesia group. Perioperative blood pressure was unstable for a significantly longer period of time after general anesthesia (mean, 24.6 hours) as compared with regional cervical block anesthesia (mean, 2.1 hours). Furthermore, vasoactive drugs were required for significantly longer periods of time in the general anesthesia group.

Evaluation of fiberoptic dermofluorometry as a means of clinically assessing tissue perfusion.

Fiberoptic dermofluorometry (FDF) transcutaneously measures fluorescence, following an intravenous injection of sodium fluorescein (NaFl), which is transmitted along a fiberoptic bundle to a photomultiplier tube and converted into dermofluorescence units (DFU). In five normal subjects studied, the plasma concentration of NaFl peaked at 5-15 minutes before decaying with first order kinetics and corresponding dermofluorescence (DF) rose to a peak between 10-20 minutes before decaying. Peak DF in the head and neck was significantly higher (P less than .001) compared to other skin sites which were similar. Application to patients (n = 16) undergoing successful lower limb revascularization showed a significant (P less than 0.01) improvement in perfusion at the foot level only. The reproducibility of FDF was poor when studied on the control limbs. We conclude that FDF does not, at present, constitute a valid measure of skin perfusion.

Extraperitoneal aortic bypass with exclusion of the intact infra-renal aortic aneurysm: the in-situ management of aortic aneurysms. A preliminary report.

Transabdominal aortic aneurysmorraphy with graft replacement is the generally accepted and most widely applied surgical approach in the treatment of infra-renal abdominal aortic aneurysm with a mortality rate of 2-5%. The alternative, retroperitoneal exposure of the aorta, although utilized for the first reported repair of an AAA by Dubost and championed by Rob, Stipa and Shaw, Helsby and Moosa and more recently by Williams et al., offers superior exposure and decreased post-operative morbidity. Despite these advantages, it is not commonly used by most vascular surgeons for the surgical management of aortic aneurysms. We have treated 35 patients using an extended retroperitoneal approach in which the aneurysm was treated by division of the infra-renal aorta, an end-to-end proximal anastomosis with an aortic bypass, and over-sewing of the aneurysm. In this group of patients, we found less post-operative physiological disturbances and a reduced requirement for blood transfusion. These data suggest that this method of retroperitoneal exclusion and bypass is generally applicable and is of particular value in the obese and/or the higher risk, medically disadvantaged patient.

Visceral aortic aneurysm in a 4 1/2-year-old child: an unusual complication of umbilical artery catheterization.

A 4 1/2-year-old girl had a 2.2 cm in diameter abdominal aortic pseudoaneurysm extending from above the celiac artery to 4 cm above the aortic bifurcation. This lesion developed after umbilical artery catheterization in the neonatal period, which also resulted in thrombosis of the right renal artery and renal atrophy. Patch graft angioplasty with polytetrafluoroethylene (Gore-Tex) was performed after excision of the aneurysm via a retroperitoneal approach.

Perioperative hypertension in patients undergoing carotid endarterectomy: shorter duration under regional block anesthesia.

Two alternative anesthetic techniques for use during carotid endarterectomy were studied in a series of 424 procedures. A total of 248 were performed in patients under general anesthesia and 176 patients received regional block anesthesia. Perioperative instability of blood pressure was noted in 108 patients. Hypertension was noted in 17.7% of those under general anesthesia vs 20.5% of those under regional block anesthesia. Intravenous vasodilator agents were used for 19.62 hr (+/- 4.33) in the general anesthesia group vs 1.4 hr (+/- 0.44) in the regional block anesthesia group (p less than .02). Perioperative hypertension correlated best with uncontrolled preoperative hypertension. Under regional block anesthesia the incidence of shunting was 4.5%. The 1 month operative mortality for the entire carotid series was 1.2% (5/424). There were three stroke-related deaths. In addition, two nonfatal major strokes and two minor strokes occurred in patients who received general anesthesia vs one nonfatal major stroke in a patient who received regional block anesthesia.

Initial experience comparing B-mode imaging and venography of the saphenous vein before in situ bypass.

Preoperative saphenous vein assessment was performed using both venography and B-mode scanning. Fifty patients underwent preoperative assessment, and the results were compared with the intraoperative findings. Both venography and B-mode imaging were equally accurate at determining the dominant saphenous system, but B-mode imaging missed five thigh double systems that were shown on venography. Neither venography nor B-mode imaging were good predictors of actual vein size at most sites in the leg, with the exception of B-mode assessment below the knee, where there was a positive correlation with intraoperative vein size (r = 0.80; p less than 0.01). In our study, B-mode scanning was consistently more reliable in determining vein presence and continuity than venography, which gave nine false-negative results. Finally, B-mode imaging allows the marking of a saphenous vein map on the patient's leg preoperatively as a guide to bypass surgery.

Distal in situ vein bypass torsion--a technique to avoid it.

One of the stated advantages of the in situ bypass is that twists or torsion along the vein are automatically prevented by the technique. Unfortunately, this is not strictly true because the distal mobilized end of the vein, which is being anastomosed to the outflow tract, is quite prone to twists of 180 to 360 degrees after its arterialization. This torsion may result in either immediate cessation of flow or later formation of an anastomotic stenosis. We describe a technique that, when used, should eliminate all such problems.

Effects of isovolemic hemodilution on abdominal aortic aneurysmectomy in high risk patients.

Intraoperative isovolemic hemodilution might increase blood flow and tissue oxygenation in the periphery but there is concern that acute anemia may have deleterious effects on myocardium in patients with coronary artery disease. This study investigates the effects of intraoperative isovolemic hemodilution on morbidity, mortality and hemodynamics in 32 patients with significant cardiovascular disease undergoing elective abdominal aortic aneurysmectomy. The average hematocrit was lowered intraoperatively from 43% to 31% by withdrawing blood and replacing volumes with 1:3 Ringer's lactate. In ten patients myocardial function was evaluated during aortic cross-clamping and declamping in the face of hemodilution. There were two deaths: one myocardial infarction and one multiple organ failure. Aortic cross clamping did not change heart rate, vascular pressures (VP), vascular resistance (SVR), cardiac output (CO), and left ventricular stroke work (LVSW). Following declamping, VP, CO and LVSW decreased and SVR increased momentarily (p less than 0.05), but the myocardial function did not change. Isovolemic hemodilution had no apparent adverse effects on morbidity, mortality and cardiovascular performance in these patients.

Transcutaneous flow measurements in in-situ bypasses: an assessment of duplex scanning.

Measurement of laminar flow using an ultrasound scanner was shown to have a high degree of correlation with quantified timed flows (r = 0.98, p less than or equal to .001). Sixty-one in-situ bypasses had flow assessed both proximally and distally. Mean fistula flow (proximal-distal flows) for time periods 1-8 weeks, 3 to 8, and 9+ months were 108, 85, and 16mls respectively. Distal bypass flow remained constant despite a significant decrease in fistula flow between the later time periods (p less than or equal to .001) (unpaired t-test). There was no evidence from the study that proximal flow through fistulas of varying resistances adversely affected the distal bypass flow.

The anatomy of the greater saphenous venous system.

To define surgical anatomy, a prospective study of the greater saphenous venous system in 385 instances in 331 patients was carried out with the use of prebypass phlebography (either pre- or intraoperative). The phlebographic interpretations were confirmed during the operative procedures and from the completion angiogram. These details were recorded and analyzed by a specific computer program. These data consisted of a number of superficial branches, perforators, the identification of valve leaflets, sinuses, and the size and position of the main venous trunk both in the thigh and in the calf. The study showed that a single trunk was present in the thigh in 65% of patients and in the calf in 45%. The remainder were variants of double systems. In two thirds of patients who had complete double systems, the larger system was used for in situ bypass but the rest required the use of parts of both systems. Phlebography was accurate in the depiction of the anatomic variations (93%), double systems, cross connections, and perforator branches (87%). However, the number of competent valves could not be accurately determined (accuracy, 68%). The diameter of the vein was frequently underestimated (in 80% by 1.1 +/- 0.4 mm) and hence could not be used as an index of vein adequacy. After phlebography, four patients had transient rises in serum creatinine levels and one had an iatrogenic thrombosis of a distal segment. This study suggests that the precise anatomy of the greater saphenous venous system should be determined preoperatively by phlebography since this information is valuable for proper surgical planning before vein is used as a graft or for in situ bypass in the lower extremity.