Biomedical subjects

M W Webster

Publications and source records attributed to M W Webster.

At least 109 records · Page 6Linked to original sources

PubMed1987

Relief of nonhemispheric symptoms in low flow states by anterior circulation revascularization: a physiologic approach.

Operative intervention remains controversial for patients with transient nonhemispheric symptoms with occlusive disease of both the anterior and posterior cerebral circulations. In addition to the standard evaluation of these patients, we have used stable xenon-enhanced computed tomographic mapping of cerebral blood flow (Xe/CT CBF). This relatively new and potentially widely available CBF methodology, by measuring approximately 30,000 CBF values within each of three CT levels, provides a readily interpretable means of evaluating extremes of hemodynamic compromise within any or all vascular territories. In the past 30 months, Xe/CT CBF studies in 300 patients with occlusive vascular disease have identified nine patients with global low flow and nonhemispheric symptoms (vertigo, lightheadedness, and/or blurred vision). Blood pressures determined by ocular pneumoplethysmography of Gee were markedly abnormal with reduced ocular/brachial ratios. Each patient had a combination of both segmental carotid and vertebrobasilar occlusive disease. Each patient had a flow-augmenting procedure performed on the anterior circulation in an attempt to improve global flow: carotid endarterectomy (two patients), subclavian-external carotid bypass (one patient), and superficial temporal artery-middle cerebral artery bypass (six patients). In each case disabling transient symptoms were relieved. There were no operative deaths, but one stroke occurred, probably as a result of a brief period of postoperative hypotension. Postoperative Xe/CT CBF studies show a long-term improved global CBF in all patients.

Brain↗

PubMed1987

Limb sparing operations for sarcomas of the extremities involving critical arterial circulation.

Seven patients underwent resection of a sarcoma of the extremity requiring excision of a vital artery and revascularization. These included osteosarcoma of the pubis, osteosarcoma of the distal femur, undifferentiated sarcoma of the thigh, liposarcoma of the thigh, liposarcoma of the popliteal space, chondrosarcoma of the proximal tibia and rhabdomyosarcoma of the thumb. Preoperative evaluation included computed tomographic scan, magnetic resonance imaging and angiography. Operation involved excision of the iliac artery in one instance, femoral artery in three, popliteal artery in two instances and radial artery in one. Wide local resection including revascularization was undertaken when the tumor could be resected with the artery but separated from the nerve and it was a low grade malignant disease or the patient refused amputation for a high grade malignant disease. In five patients, the tumor margins were adequate. One patient with an osteosarcoma of the pubis with distant disease had a palliative resection and one patient had positive margins but refused amputation. Coverage of the soft tissue and vascular grafts was achieved using a distant pedicle flap in two patients. Amputation was avoided and each patient remained ambulatory. Five patients remained free of disease with patent grafts at six months to six years of follow-up study. One patient died of late myocardial infarction and one who underwent palliative resection died eight months later of metastatic disease. Involvement of the major arterial circulation does not preclude adequate resection of sarcomas of the extremity with limb salvage.

Adult↗

PubMed1986

Repositioning catheters in surgically drained abscesses.

Primary percutaneous drainage of intraabdominal abscesses under local anesthesia is an accepted method of treatment, with low morbidity and mortality. This technique was extended to patients with recurrent or secondary abscesses after initial primary surgical drainage. Four patients had abscesses drained operatively but were reevaluated several weeks later for recurrent fever. Sinography demonstrated an inadequately drained abscess cavity. Under fluoroscopic control and using local anesthesia, new drains were inserted and repositioned to provide better drainage. Resolution of the abscess cavity was documented radiographically, with improvement in the patients' clinical status.

Abdomen↗

PubMed1986

TcPO2 values in limb ischemia: effects of blood flow and arterial oxygen tension.

Transcutaneous oxygen tension (TcPO2) is determined by blood flow and arterial oxygen tension (PaO2) and has been advocated as a measurement of tissue perfusion in peripheral vascular disease. The purpose of this study was to define the relationship between regional blood flow, PaO2, and TcPO2. TcPO2 sensors were placed on the skin of the anterior tibial regions of the hind limbs of 15 dogs. After occluding collateral blood flow, an external flow probe was placed around the femoral artery and an adjustable clamp was used to produce graded ischemia. Progressive reductions in blood flow were correlated with TcPO2 values at inspired oxygen concentrations (FiO2) of 0.21, 0.50, and 1.00. TcPO2 measured at room air decreased nonlinearly in relation to flow with a marked drop occurring below 20% of baseline flow. TcPO2 measured at increased FiO2 was dependent primarily on PaO2 at flow rates greater than 50% of baseline. With reduction in flow below 25% of baseline, TcPO2 was dependent solely on flow and was not augmented by increases in PaO2. The data suggest that TcPO2 can accurately reflect changes in blood flow to an extremity when flow is severely restricted.

Animals↗

PubMed1986

Combined spironolactone and converting-enzyme inhibitor therapy for refractory heart failure.

Three cases are described of severe congestive heart failure which failed to respond to digitalis, high doses of loop diuretics, and converting-enzyme inhibitors. The addition of spironolactone produced a substantial diuresis associated with clinical and radiological improvement in each case. Although a reversible deterioration in renal function was observed, this drug combination represents a therapeutic option in end-stage heart failure.

Adult↗

PubMed1986

General surgery in adult hemophiliacs.

From 1976 to 1984, 23 operations were performed on 22 patients with hemophilia (18 patients with factor VIII and four with factor IX deficiency). Elective procedures included resection of abdominal aortic aneurysm, liver transplantation, vagotomy/pyloroplasty, insertion of Mousseau-Barbin tube, colectomy, cholecystectomy, inguinal herniorrhaphy (four patients), colonoscopy/polypectomy, mediastinoscopy, arteriovenous fistula for dialysis, anal fistulectomy, and miscellaneous skin and soft-tissue procedures (five patients). Emergency operations were appendectomy (two patients), repair of bleeding liver biopsy site, and repair of an incarcerated inguinal hernia. There were two deaths (9%) within 30 days of operation, neither directly caused by the coagulopathy. Four patients had bleeding after surgery, which was treated with additional cryoprecipitate or factor concentrate. There were no nonhemorrhagic complications. Before operation, appropriate replacement therapy with factor VIII concentrate, cryoprecipitate, or fresh-frozen plasma was provided. Coagulation factor levels were measured before operation and monitored daily after operation. Generally, factor levels were raised to at least 1.0 U/ml and maintained at greater than 0.5 U/ml for 7 to 14 days after operation. However, when patients were treated with fresh-frozen plasma, plasma exchange was performed and factor levels of approximately 0.35 U/ml were achieved before surgery. We conclude that operations in patients with hemophilia can be accomplished safely with careful monitoring of coagulation factor levels and appropriate replacement therapy.

Adolescent↗

PubMed1986

Cerebral blood flow measured by xenon-enhanced computed tomography as a guide to management of patients with cerebrovascular disease.

CT scanning performed before and sequentially during the inhalation of stable xenon (32%), coupled with end-tidal xenon measurements, has made possible the routine construction of regional cerebral blood flow (rCBF) maps with resolution that approximates that of the CT scanner. The capability of obtaining quantitative flow maps with direct anatomic correlation is now available with a commercial package of hardware and software adapted to the General Electric 9800 scanner. The ability to distinguish between normal and reduced rCBF in specific vascular territories has proved useful in the management of cerebrovascular disease. Specific clinical dilemmas that have been addressed with rCBF information from xenon-enhanced CT scanning include the following: In the patient with asymptomatic occlusive disease, is normal rCBF preserved? Is there adequate collateral flow? Are cerebrovascular symptoms a result of emboli or chronic regional low flow? In the patient with complex multivessel occlusive disease, which revascularization procedure is indicated first? Did operation improve rCBF? Should a further procedure be added? May a diffusely diseased but patent artery, which is the source of emboli, be sacrificed safely without compromising rCBF? On the basis of experience with 155 patients, the management and understanding of cerebrovascular disease has been aided substantially by the incorporation of rCBF mapping by xenon-enhanced CT scan in the evaluation of these patients.

Aged↗

PubMed1986

Streptokinase in the treatment of subclavian vein thrombosis.

During the past 2 years, streptokinase has been used to treat subclavian or axillary vein thrombosis in seven patients of whom two were considered "effort" thromboses and five resulted from use of a central venous catheter. All patients had venography performed before treatment to document the thrombosis, and venography was repeated after streptokinase therapy to determine the status of clot dissolution. Streptokinase was given either systemically or in a lowered dose locally, with low-dose therapy chosen whenever a catheter could be threaded up to the clot through an antecubital vein. Although all seven patients had resolution of their clinical symptoms, only one had complete dissolution of the thrombus. The failure of streptokinase to completely dissolve the thrombus suggests that, although apparent clinical improvement can be achieved after streptokinase infusion, treatment of the underlying cause, whenever possible, may be necessary if complete resolution of the thrombus is to occur.

Adult↗

PubMed1986

Recognition and treatment of arterial insufficiency from cafergot.

Cafergot is a combination of ergotamine tartrate and caffeine and may cause symptoms of peripheral vascular insufficiency. Iatrogenic ergotism should be suspected in any patient exhibiting ischemic symptoms while receiving this medication. Progression to fulminant necrosis and gangrene can occur. Two cases are presented and the management reviewed. This effect of ergotamine tartrate and caffeine may be an idiosyncratic hypersensitivity reaction with therapeutic doses or may result from excessive medication. Iatrogenic ergotism occurs most often in women in their mid-thirties with migraine syndrome. By alpha-adrenergic agonism, as well as by possible interactions with prostaglandins, calcium, and serotonin, ergotamine causes vasoconstriction of both arteries and veins. The angiographic pattern of spasm, collateral formation, and intravascular thrombi is typical. Treatment of ergotism depends on the severity of the symptoms and the possibility of gangrene. Discontinuation of ergotamine, cigarette smoking, and caffeine may be all that is necessary in most patients. Nitroprusside is the drug of choice in the treatment of acute vascular insufficiency from ergotism, but in a less urgent situation, prazosin has also been effective. Intra-arterial balloon dilatation has also been helpful. Other forms of therapy have been supportive and the results inconsistent. Cafergot should be used with extreme caution in patients with renal or hepatic failure, peripheral vascular disease, or pregnancy. Relative contraindications include hypertension, ischemic heart disease, and Raynaud's phenomenon.

Adult↗

PubMed1986

The syndrome of spontaneous iliac arteriovenous fistula: a distinct clinical and pathophysiologic entity.

While the development of a spontaneous iliac arteriovenous fistula is an uncommon complication of arteriosclerotic aneurysmal disease, its association with a distinct clinical syndrome allows timely operative intervention for this potentially life-threatening event. A review of cases reported in the literature reveals a triad of symptoms consistently associated with the presence of a spontaneous iliac arteriovenous fistula: high-output cardiac failure of precipitous onset, a pulsatile abdominal mass accompanied by a thrill and bruit, and unilateral lower-extremity ischemia or venous engorgement. Survival may be anticipated if an aggressive diagnostic and operative approach is employed.

Aged↗

PubMed1985

Effect of enalapril on ventricular arrhythmias in congestive heart failure.

Twenty-four-hour Holter electrocardiographic recordings were used to measure the effects of a converting-enzyme inhibitor, enalapril, given for 12 weeks, on the frequency of cardiac arrhythmias in 10 patients with congestive heart failure (New York Heart Association functional class II to III) receiving maintenance therapy with digoxin and furosemide. Nine patients were given placebo, and both study groups were conducted in a double-blind, parallel manner. The placebo group had no change in the frequency of arrhythmias, whereas enalapril-treated patients showed a significant decrease in the frequency of premature ventricular complexes, ventricular couplets and ventricular tachycardia. A minor, nonsignificant reduction in atrial premature complexes was seen in patients who received enalapril. Compared with placebo patients, those who received enalapril had an increase in plasma potassium levels of 0.33 mmol/liter, a decrease in plasma digoxin, and decreases in pulmonary artery wedge, mean pulmonary artery and right atrial pressures. However, none of these indexes were correlated with the concomitant decline in cardiac arrhythmias. It is concluded that enalapril reduces the frequency of ventricular arrhythmias in congestive heart failure, although the underlying mechanisms are not known.

Adult↗

PubMed1985

Renal, haemodynamic, and hormonal effects of human alpha atrial natriuretic peptide in healthy volunteers.

The effects of atrial natriuretic peptide (ANP) were investigated in six healthy male volunteers taking a constant diet (120 mmol sodium and 60 mmol potassium daily). They were given an intravenous bolus of 100 micrograms human alpha-ANP on one day or placebo on another day 1-3 weeks apart in a double-blind randomised study. After ANP, urinary sodium excretion increased four-fold, and urine volume, calcium, magnesium, and phosphorus excretion doubled within 30 min of the injection. ANP induced an immediate fall in arterial pressure, followed by a longer vasodepressor phase which exceeded the duration of the effect on electrolyte excretion. There were no significant changes in plasma renin activity, aldosterone, antidiuretic hormone, or noradrenaline when compared with placebo.

Atrial Natriuretic Factor↗

PubMed1985

Late sequelae of gastric acid injury.

The late sequelae of gastric acid injury follow a predictable pattern and often require operative correction. Pyloric and antral stenoses are the most commonly cited late complications of acid ingestion. Other late sequelae include intractable pain, achlorhydria, protein-losing gastroenteropathy, duodenal atonicity, radiographic abnormalities, mucosal metaplasia, and gastric carcinoma. Resection of the injured gastric segment appears to provide the most favorable long-term result. Diligent patient follow-up is required to ensure adequate restoration of gastrointestinal function and to correct late-appearing complications. The distinction between the expected sites of gastrointestinal injury in acid versus alkali ingestion has become less clear with the recent introduction of readily available concentrated liquid household alkaline products, and the incidence of late gastric sequelae of caustic injuries has increased accordingly.

Adult↗

PubMed1985

EEG changes during carotid endarterectomy: drug effect and embolism.

Clinical neurological status and the electroencephalogram (EEG) were monitored during right carotid endarterectomy under regional anaesthesia in a patient who had suffered two prior cerebral infarctions. No change in EEG or clinical status was seen with occlusion of the carotid artery, but generalized encephalopathic changes were seen after a small dose of narcotic given before carotid occlusion. Bihemispheric changes in EEG and neurological status occurred upon release of carotid occlusion. This case demonstrates three important points. First, EEG changes can be seen with sedative or anaesthetic agents in patients who have previously suffered brain injury. Second, temporary neural dysfunction may be seen remote from the site of a localized injury to the brain--a phenomenon known as diaschisis. Finally, this report reiterates the observation that the risk of injury to the brain during carotid endarterectomy is not limited to the period of possible ischaemia during occlusion of the carotid artery.

Aged↗

PubMed1985

Effects of enalapril on clinical status, biochemistry, exercise performance and haemodynamics in heart failure.

The effects of enalapril on clinical well-being, treadmill exercise performance, haemodynamic measurements, hormone levels, and plasma biochemistry in patients with moderate heart failure, were assessed in a 12-week placebo-controlled, double-blind study. Maintenance frusemide and digoxin treatment was continued throughout the study. Compared with placebo, enalapril treatment improved clinical status and increased exercise capacity. The most obvious haemodynamic change was a fall in pulmonary artery wedge pressure and pulmonary artery pressure. Enalapril-induced increases in left-ventricular ejection fraction and cardiac index, and falls in systemic arterial pressure, were small. Of the hormone indices measured, plasma renin activity rose 4-fold, angiotensin II and aldosterone fell slightly, and plasma catecholamines were unaltered by enalapril. Plasma potassium increased on average by 0.3 mmol/L during enalapril therapy. No adverse clinical or biochemical effects were observed. Enalapril has a sustained beneficial action in patients with moderate heart failure.

Adult↗

PubMed1985

General surgical complications in heart and heart-lung transplantation.

One hundred forty-three patients underwent cardiac transplantation from 1980 to 1985; 122 received a heart, 19 received a heart-lung, and two received a heart-liver transplant. All patients received immunosuppression with prednisone and cyclosporine. General surgical complications have developed since transplantation in 40 patients (28%). Of these, 17 patients have required surgery: exploratory laparotomy (10 patients), inguinal or ventral herniorrhaphy (two patients), repair of false aneurysm of the femoral artery (two patients), repair of lymphocele of the groin (two patients), and incision and drainage of a perirectal abscess (one patient). Of the 10 patients who required laparotomy, three underwent sigmoid resection for a perforated sigmoid diverticulum (all survived), two underwent small bowel resection for perforation (both died), two had free intraperitoneal air with no site of perforation found (one died), one underwent a cholecystostomy and one a cholecystectomy for acute calculous cholecystitis (one died), and one underwent an elective pyloroplasty for gastric outlet obstruction secondary to vagus nerve injury during heart-lung transplantation and survived. All patients who underwent elective surgery survived. Six patients died without operation and at autopsy were found to have unrecognized general surgical complications including pancreatitis (three patients), cecal ulceration with sepsis (two patients), and jejunal perforation secondary to peritoneal dialysis (one patient). Eleven other patients had severe abdominal pain and five had gastrointestinal hemorrhage not requiring operation. Proper management of these patients includes early and aggressive diagnosis of conditions requiring operative intervention, strict attention to surgical technique, and careful titration of dose of immunosuppressive drugs. The 28% incidence of general surgical complications associated with heart and heart-lung transplantation emphasizes the role of the general surgeon in the management of these complex patients.

Adolescent↗

PubMed1985

Salvage of exposed arteriovenous hemodialysis fistulas.

Arteriovenous fistulas constructed with an interposed segment of expanded polytetrafluoroethylene (PTFE) have been used successfully for long-term hemodialysis, but ultimately these fistulas may fail because of graft thrombosis, infection, or pseudoaneurysm. A PTFE graft may become exposed from skin necrosis at an area of repeated puncture for hemodialysis or from wound breakdown at a site of thrombectomy. Removal of an exposed PTFE graft has heretofore been considered inevitable, especially if a suture line is involved, because of the risk of hemorrhage and infection. We describe coverage of an exposed graft by a simple full-thickness skin flap that is locally rotated and report the successful salvage of five fistulas by this technique. Thus the concept that an exposed graft is infected and must be removed may not always be correct.

Arteriovenous Shunt, Surgical↗

PubMed1984

Arterial complications of total knee replacement.

Arterial complications of total knee replacement are rare but may be more frequently encountered as the number of replacement arthroplasties increases. An arterial injury may occur on either an acute or chronic basis, leading to ischemia of the lower extremity. The mechanism of injury may be analogous to that encountered in the popliteal artery entrapment syndrome, but may also result from disruptive forces applied to calcified atherosclerotic vessels by the pneumatic tourniquet or during intraoperative manipulation. A thorough preoperative vascular evaluation should be routinely performed in patients with evidence of coexisting peripheral arterial disease, and baseline Doppler segmental pressures should be obtained. Early detection of an arterial injury may prevent the serious consequences that might otherwise occur.

Arterial Occlusive Diseases↗