Reflex sympathetic dystrophy--the surgeon's role in management.

It is important for vascular surgeons to be familiar with reflex sympathetic dystrophy because they may be called on to participate in the evaluation and treatment of patients with this syndrome. Over a 3 1/2-year period, 35 patients, initially evaluated by a team of pain experts, were referred for surgical sympathectomy for reflex sympathetic dystrophy. All patients had at least one positive diagnostic sympathetic block before they were considered for surgical sympathectomy. With use of this team approach and careful patient selection, excellent results were obtained in 74%, good results in 17%, and poor results in 9%. Three patients required a repeat cervical sympathectomy after initial surgery failed to relieve their symptoms. One patient required a contralateral lumbar sympathectomy after ipsilateral sympathectomy was unsuccessful. Better results were obtained in patients treated earlier in their course and with extended surgical sympathectomy. Patients not responding to initial sympathectomy should be evaluated for the presence of residual functional sympathetic tissue, and if this is identified, further sympathectomy by an alternate approach appears justified.

Combined thrombectomy and dilation for the treatment of acute lower extremity arterial thrombosis.

Our experience with combined balloon catheter thrombectomy and balloon dilation for the treatment of acute thrombosis is reported. Eighteen patients underwent the combined procedures between 1981 and 1988. Primary thrombectomy and balloon dilation were performed in 14 patients, and additional reconstruction was performed in three patients. The superficial femoral artery was the site of thrombectomy and dilation in 13 patients, and the external iliac artery was the site in the remaining five patients. Successful dilation was accomplished in all patients, with stenotic sites reduced below 30% by angiography, and ankle/brachial indexes increased by 0.15 or more. No operative deaths or complications occurred. Follow-up of superficial femoral artery dilations showed a 90% patency rate continued out to 4 years and a 40% patency rate at 5 years. Combined thrombectomy and interventional catheter therapy may aid in the care of this difficult to treat vascular patient group.

Long-term results of intraoperative balloon dilatation.

A review was conducted of 61 patients who underwent intraoperative balloon dilatation over the past five years. Of the 62 dilatations in this patient group, 80% were performed in conjunction with a reconstructive procedure, and 20% were performed as a primary procedure. Dilatations were performed with the linear extrusion balloon catheter. A 94% rate of followup was achieved, with a mean followup of 16.3 months (range 1-60 months). Life table analysis reveals a 95% initial success rate decreasing to an 81% patency rate by the end of the fifth year for iliac dilatations, a 97% initial and 58% five-year patency rate for superficial femoral dilatations, and an 86% initial and 37% five-year patency rate for popliteal dilatations. 21.3% of the patients died during the followup period. No deaths occurred as a result of intraoperative angioplasty. One arterial rupture occurred, requiring a bypass graft at the same surgery. We conclude that intraoperative balloon dilatation in an adjunctive setting may offer clinical benefits to vascular patients while requiring little additional operative time.

Arterial thromboembolism. A 20-year perspective.

Our experience with 739 patients with lower extremity thromboembolism since the advent of the balloon catheter has led us to several important observations: As the etiology has shifted from rheumatic to atherosclerotic, we treat a more complex group of patients, one fourth of whom have severe, preexisting peripheral occlusive disease. Early diagnosis and treatment is essential to decrease the mortality and morbidity, which has ranged about 25% +/- 10%. Anticoagulation must be continued in the postoperative period, accepting wound hematomas as a fair "trade-off" to prevent recurrent embolus and distal thrombosis in areas inaccessible to the catheter. Postoperative use of heparin "buys time" to further assess marginal results of embolectomy allowing arteriography and careful planning of secondary operations to assure not only a viable but a functional limb. There is little mention in the literature to emphasize this approach, which we think is essential for long-term salvage. Early in the series, patients were treated with heparin or embolectomy alone. There were 161 secondary operations in 135 patients following embolectomy consisting of repeated thromboembolectomy, popliteal exploration, sympathectomy, bypass graft(s), angioplasty, and endarterectomy. Additionally, 44 patients had a direct attack correcting the cardiac source of their embolism. Our overall mortality (12%) and limb salvage (95%) shows marked improvement compared with earlier reports. Therefore, we recommend combined embolectomy and heparin as the primary choice of therapy.

Transluminal angioplasty: a mechanical-pathophysiological correlation of its physical mechanisms.

We quantitatively determined the relative contribution of various factors leading to arterial lumen enlargement during transluminal angioplasty. Mechanical tests were conducted on both normal and atherosclerotic artery necropsy specimens. In our range of dilating pressures (0-3.4 atm or 0-50 lb/in2), content extrusion of fluid from the plaque accounted for 6-12% of the overall lumen area increase, while compaction of the plaque accounted for only 1-1.5%. The majority of the increase, 86.8-93%, was due to plaque and arterial wall disruption. The mechanism of disruption began with shearing of the plaque from the underlying artery at relatively low dilating pressures and continued with longitudinal tearing and stretching of the arterial wall at higher pressures. Diseased arteries dilated significantly more than nondiseased arteries at dilating pressures greater than or equal to 1.36 atm or 20 lb/in2 (P less than .05). In the range of stenoses that were tested (10-50%), the mean dilating pressure required to increase the lumen cross-sectional area by 50% was approximately 1.5 atm or 22 lb/in2.

A physical measurement of the mechanisms of transluminal angioplasty.

We report a quantitative determination of the relative contribution of various factors leading to arterial lumen enlargement during transluminal angioplasty. Mechanical tests were conducted on both normal and atherosclerotic artery necropsy specimens. In the range of dilating pressures tested (0 to 3.4 atm or 0 to 50 lb/in2), content extrusion of fluid from the plaque accounted for 6% to 12% of the overall lumen area increase, while compaction of the plaque accounted for only 1% to 1.5%. Most of the increase (86.8% to 93%) was due to plaque and arterial wall disruption. The mechanism of disruption involved shearing of the plaque from the underlying artery at relatively low dilating pressures, followed by longitudinal tearing in the arterial wall at higher pressures. Diseased arteries were observed to dilate significantly more than nondiseased arteries at dilating pressures greater than or equal to 1.36 atm or 20 lb/in2 (P less than 0.05). In the range of stenoses tested (10% to 50% based on diameter reduction), the mean dilating pressure required to increase the lumen cross-sectional area by 50% was approximately 1.5 atm or 22 lb/in2. Based on these studies, we conclude that balloon dilatation results arise mainly from plaque and arterial wall disruption.

Prognosis of asymptomatic ulcerating carotid lesions.

To determine the proper approach to asymptomatic carotid bifurcation ulcerated plaque (UP), 79 patients with 91 asymptomatic UPs were identified angiographically, and a 96% follow-up was obtained with a mean duration of three years. The cumulative stroke rate by life-table analysis was 1% at seven years. Sixty-three UPs in 55 patients were classified as small, and of these patients, transient ischemic attacks (TIAs) that were appropriate to the lesion developed in three and stroke in one (7% cumulative symptom rate). Twenty-four UPs in 21 patients were classified as large, and a TIA developed in one patient (9%), but no strokes were observed in this group. The cumulative mortality was 17% at three years and 52% at seven years. Life-table curves of several subgroups were compared and showed no significant differences in either stroke rate or mortality between any of these groups. On the basis of these data, and particularly the seven-year stroke rate of 1%, prophylactic carotid endarterectomy is not justified for asymptomatic carotid bifurcation ulcerations.

Hemodynamic response to exercise in the unanesthetized calf with pulseless arterial flow.

In a chronic unanesthetized calf model with a centrifugal pump inserted from left ventricle to aorta, calves were trained to perform treadmill exercise and undergo hemodynamic measurements. Resting hemodynamic changes with pulseless pumping included increases in cardiac output, aortic pressure, and heart rate, with some decrease in systemic vascular assistance. Treadmill exercise was associated with further increases in cardiac output and heart rate, which progressively increased during the 10 days of observation, with little change in mean aortic pressure. Pump autoregulation responded to the decreased systemic vascular resistance associated with exercise by increasing pump output about 15%, at constant pump rotatory speed. These experiments add further evidence regarding the ability of a centrifugal left ventricular assistance system to support the failing heart and to permit moderate degrees of exercise in the intact unanesthetized calf.

Intraosseous infusion: pressure-flow relationship and pharmacokinetics.

In order to quantitatively investigate the usefulness of intraosseous fluid and drug administration as a resuscitative modality, we studied the infusion flow rates of crystalloid solutions obtainable at varying infusion pressures into the bovine tibial medullary cavity and time to initial as well as 90% of maximal effect of intraosseously administered vasoactive drugs. Mean infusion rates +/- SEM (n = 6) at 300, 200, and 100 torr and atmosphere + 81 cm H2O were 41 +/- 2, 32 +/- 1, 27 +/-2, and 10 +/- 1 ml/min, respectively. The mean time (+/- SEM) to initial effect of intraosseous injections (n = 6) of either 0.5 mg epinephrine or 50 mg ephedrine was 17 +/- 3 seconds and mean time to 90% of maximal effect was 45 +/- 5 seconds. These results provide a quantitative basis for resuscitation by fluid and drug administration via the tibial malleolar intraosseous route and suggest that when performed in appropriate situations, the technique may have clinical utility.

Quantitative transcutaneous arterial velocity measurements with Doppler flowmeters.

A controlled in vitro and in vivo comparative evaluation of four Doppler ultrasonic blood velocimeters was performed to evaluate their ability to measure fluid velocity throughout a wide range of flow rates and velocity profiles, during both steady and pulsatile flow. The instruments tested were the Versatone Bidirectional Doppler M-9, the Sonicaid BV380, the Parks 806 B, and the Delalande DUD 400. All instruments responded linearly to velocities of from 5 to 70 cm/s, and were accurate to within 5% through a wide range of in vitro changes in velocity, pulse frequency, and cross-sectional velocity profile. Quantitative velocity measurements and their derivatives are an inexpensive, simple, and useful tool in the evaluation conditions of patients with peripheral vascular disease, and widespread clinical trials of their value are appropriate at this time.

Renin secretion in the chronically perfused pulseless calf. Evidence for failure of stimulation by decreased pulse pressure.

To study the influence of arterial pulse pressure on renin release, a chronic pulseless calf preparation was developed using a centrifugal left ventricular bypass blood pump. After pump implantation and recovery, control measurements of renal vein and arterial plasma renin activity, arterial pressure, and renal artery flow were obtained. The centrifugal bypass pump rate then was increased to capture cardiac output completely, and nine conscious calves were perfused in a nonpulsatile manner (pulse pressure less than 5-10 mm Hg) for 48 hours. Nonpulsatile perfusion was well tolerated and serum sodium, potassium, creatinine, and blood urea nitrogen were unchanged during bypass. Mean arterial pressure remained relatively constant [114 +/- 3 (SE) mm Hg] during bypass, and was not significantly changed from control. Although renal blood flow decreased slightly from control (667 +/- 84 ml/min) during the nonpulsatile perfusion period (555 +/- 73 ml/min), renin secretion did not increase significantly from control (482 +/- 81 ng angiotensin I/ml per hr per min) during the bypass period (531 +/- 99). A diurnal cycle of renin secretin was observed during the pulseless perfusions. These data document the lack of any significant stimulatory influence of decreased pulse pressure on renin secretion in a chronic awake calf model.

A system for restraint and anesthesia in calves.

A mobile calf enclosure was developed which incorporated a hydraulic hoist and sling for the care of calves. This apparatus permitted induction of and emergence from anesthesia in an erect posture, which decreased the risk of aspiration and postoperative pulmonary problems. Fifty-two surgical procedures requiring general anesthesia have been performed on 29 calves during the last 2 years with only one operative death, and calves have been maintained within the enclosure for periods up to 1 month.

Effect of pulseless perfusion on gastrointestinal blood flow and its distribution.

The effect of nonpulsatile (NP) arterial perfusion on gastrointestinal organ blood flow and intraorgan flow distribution was studied in 10 anesthetized (pentobarbital) dogs utilizing the radionuclide-labeled microsphere (15 micrometer) technique. Measurements of flow to the stomach, small intestine, and colon were made during a pulsatile perfusion control period and after 1- and 2-h periods of NP perfusion with a centrifugal left ventricular bypass pump (Medtronic). Total gastric blood flow (0.178 +/- 0.021 ml/min per g) as well as the partitioning of that flow between gastric subsegments such as antrum (17% of total gastric flow), body (83%), and mucosa (73%) was not significantly altered during the 2-h period of NP perfusion (P greater than 0.20). Similarly, flow to the intestine showed significant change during NP perfusion. Under conditions of equivalent hemodynamic states (mean perfusion pressure), nonpulsatile arterial perfusion results in no significant alteration in gastrointestinal blood flow or its intraorgan distribution.

Fallibility of the platelet count and fibrinogen concentration in evaluating circulatory assistance technique--a plea for turnover studies.

Platelet and fibrinogen kinetics were investigated in calves undergoing prolonged extracorporeal left ventricular bypass in which both platelet and fibrinogen concentrations were within or above the normal range. Sequential survival time measurements documented significant continuing destruction of both platelets and fibrinogen during the course of these perfusions, with markedly elevated turnover rates of both components. The ineffectiveness of ASA and Persantine to return these functions to normal suggests that the mechanism of destruction includes trauma from the moving parts of the system, including the rotor and bearing seal, as well as surface-induced injury from the conduits and pump housing. Kinetic studies appear to be an essential requirement in the evaluation of blood destruction and subject tolerance of prolonged circuitry assistance devices.