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Biomedical subjects

A C Roberts

Publications and source records attributed to A C Roberts.

At least 73 records · Page 4Linked to original sources
PubMed1995

Postangiographic femoral artery pseudoaneurysms: further experience with US-guided compression repair.

PURPOSE: To assess the efficacy of ultrasound-guided compression repair (UGCR) in postcatheterization femoral artery pseudoaneurysms. MATERIALS AND METHODS: One hundred thirty-three patients with pseudoaneurysms were considered for UGCR. Patients underwent compression with duplex and color Doppler ultrasound. Immediate and long-term successes were evaluated. RESULTS: Seven patients were not candidates for UGCR. UGCR was technically possible in 117 of the 126 patients who were candidates. UGCR was successful in 109 patients. The failure rate was significantly higher in patients who were receiving anticoagulant medication (P < .001). Pseudoaneurysm size, age, and structure (simple vs multiloculated) had no bearing on success or failure. The time required for successful compression was not related to treatment with anticoagulants but was related to pseudoaneurysm structure. Complications included one case of a distal embolus and two episodes of hypotension. CONCLUSION: UGCR is a simple and expedient method for the treatment of postcatheterization femoral artery pseudoaneurysms.

Aneurysm, False↗
PubMed1995

Hand ischemia in patients with hemodialysis access grafts: angiographic diagnosis and treatment.

PURPOSE: To determine the cause of symptoms and efficacy of transcatheter therapy in a series of patients with dialysis grafts and hand pain referred for arteriography. MATERIALS AND METHODS: Thirteen patients with 14 hemodialysis grafts underwent arteriography for possible hand ischemia. The sites of proximal graft anastomosis were the distal radial artery (n = 6) and the mid- to distal brachial artery (n = 6). Transcatheter therapy was performed via the graft or by antegrade brachical puncture. RESULTS: The cause of symptoms was ischemia from obstructive arterial disease in seven cases (three with superimposed steal), graft steal alone in three, ischemic monomelic neuropathy in two, and carpal tunnel syndrome in two. Five arterial stenoses were treated with angioplasty, with improvement or resolution of symptoms in four patients. CONCLUSION: In this group, symptoms were usually the result of inflow or outflow arterial disease, alone or in combination with graft steal. Transcatheter therapy (angioplasty or embolization) is effective in selected cases.

Adult↗
PubMed1995

Pulse-spray pharmacomechanical thrombolysis of thrombosed hemodialysis access grafts: long-term experience and comparison of original and current techniques.

OBJECTIVE: Pulse-spray pharmacomechanical thrombolysis is an evolving method for the treatment of vascular occlusions in which a highly concentrated fibrinolytic agent is injected as a high-pressure spray directly into thrombus. The purpose of this retrospective study was to analyze our long-term experience with this technique for the treatment of clotted hemodialysis grafts and to compare the efficacy and safety of the original and current methods. SUBJECTS AND METHODS: Over 6 years, 284 cases of dialysis graft thrombosis were considered suitable for treatment with pulse-spray thrombolysis. The original technique involved the injection of highly concentrated urokinase directly into a clot through two crisscross catheters with multiple side holes. The current technique includes early fragmentation of residual clot with a balloon catheter, intrathrombic injection of heparin, mechanical treatment of a lysis-resistant clot at the arterial anastomosis, and routine administration of aspirin. After thrombolysis, underlying obstructions were treated with balloon angioplasty, atherectomy, or stents. The technical success, immediate clinical success, and frequency of complications for the entire population were analyzed. In addition, the results for 36 cases treated with the original technique were compared with the results for 37 recent cases treated with the current technique. RESULTS: Of 284 cases considered suitable for treatment, thrombolysis was not done in eight cases because the venous anastomosis could not be crossed. Thrombolysis was discontinued in two cases because of extravasation of contrast material. The technical success for all grafts considered for treatment was 96%; 92% of treated grafts remained patent for at least 24 hr. Major complications occurred in 1% of cases, and minor complications occurred in 9% of cases. The clinical efficacies of the original and current techniques were 86% and 92%, respectively. The mean thrombolytic agent infusion time was reduced from 44 +/- 20 min to 23 +/- 13 min (p < .001). The overall procedure time for the recently treated subgroup was 67 +/- 26 min. There was no significant difference in the frequencies of major and minor complications between the treatment subgroups. CONCLUSION: Pulse-spray pharmacomechanical thrombolysis is a reliable, rapid, and safe method for recanalization of occluded dialysis grafts. The current technique has been proven as safe and effective as the original technique but offers the advantage of a significant reduction in the time required for the infusion of thrombolytic agent.

Anastomosis, Surgical↗
PubMed1994

Is thrombolysis of occluded popliteal and tibial bypass grafts worthwhile?

PURPOSE: We analyzed the short- and long-term results for patients undergoing thrombolysis of occluded infrainguinal bypass grafts at our institution over a 62-month period. METHODS: Thirty-one patients with 40 episodes of graft thrombosis in 33 grafts managed by thrombolysis were retrospectively reviewed. The effects of graft age, material, and anatomy, symptoms, treatment, anticoagulation, and occlusion duration were evaluated for impact on patency after thrombolysis. Dose and duration of therapy with use of the technique of pulse-spray thrombolysis was assessed. RESULTS: Thrombolysis successfully reestablished patency in 92% of grafts treated. Mean lysis time and urokinase dose were 118 minutes and 607,000 units, respectively. Responsible lesions were identified and treated by angioplasty or surgery in 35 of 37 cases. The patency rate after thrombolysis was 28% at 30 months, and the secondary patency rate was 46% at 18 months. Duration of occlusion, symptoms, treatment, graft anatomy, and prior graft revision did not impact on patency. Mean secondary patency was 21.5 months in grafts in place over 1 year and 7.0 months in grafts in place for less than 1 year. Mean secondary patency was 23.8 months in polytetrafluoroethylene grafts and 8.4 months in vein grafts. The limb salvage rate was 84% at 30 months, and the patient survival rate was 84% at 42 months. CONCLUSIONS: Pulse-spray thrombolysis is effective in rapidly recanalizing thrombosed infrainguinal grafts. Grafts failing in the first year after placement should generally be replaced, reserving thrombolysis and revision for grafts greater than 1 year old. Vein grafts tolerate thrombosis less well than synthetic conduits and have decreased long-term patency.

Adult↗
PubMed1994

Overdilation of the Wallstent to optimize portal decompression during transjugular intrahepatic portosystemic shunt placement.

PURPOSE: To optimize shunt size with overdilation of the Wallstent during creation of a transjugular intrahepatic portosystemic shunt (TIPS). MATERIALS AND METHODS: A TIPS was created in 25 patients with variceal bleeding (n = 22) or intractable ascites (n = 3). All shunts were created with one or more Wallstents that were dilated with an 8- or 10-mm balloon. In 11 patients with inadequate portal decompression or persistent filling of varices, shunts were overdilated with a 12-mm balloon. RESULTS: Mean portosystemic pressure gradient fell from 18.0 mm Hg +/- 6.4 (standard deviation) to 6.8 mm Hg +/- 2.8 after shunt placement. In 11 patients in which shunts were overdilated, the mean gradient fell from 12.7 mm Hg +/- 5.6 after 10-mm dilation to 6.9 mm Hg +/- 2.8 (P = .01) after 12-mm dilation. In six, variceal filling occurred after 10-mm dilation but diminished or ceased after overdilation. Stent disruption did not occur. New or worsened encephalopathy occurred in four of 14 patients with 10-mm and six of 11 patients with 12-mm shunt dilation and responded to medical therapy in all but two. CONCLUSION: Overdilation of the Wallstent during TIPS placement is effective and safe in patients with inadequate portal decompression after 10-mm shunt dilation.

Adult↗
PubMed1994

Beta-adrenergic blockade does not prevent the lactate response to exercise after acclimatization to high altitude.

We examined the extent to which epinephrine influences blood lactate adjustments to exercise during both acute (AC) and chronic (CH) high-altitude exposure. Eleven male sea level residents were divided into a control group (n = 5) receiving a placebo or a drug group (n = 6) receiving 240 mg/day of propranolol. All subjects were studied at rest and during 45 min of submaximal exercise (approximately 50% of sea level maximal O2 uptake) at sea level (SL) and within 4 h of exposure to and after 3 wk residence at 4,300 m (summit of Pikes Peak). Blood samples were collected from the femoral artery for epinephrine and lactate concentration. Exercising blood lactate concentration was significantly different across all altitude conditions such that AC > CH > SL (P < 0.05). For a given arterial O2 saturation, mean exercising blood lactates were lower for the beta-blocked group compared with controls; however, both groups demonstrated similar patterns across all conditions. Epinephrine levels during exercise followed a similar pattern to that of lactate, averaging 0.67, 0.43, and 0.29 ng/ml for AC, CH, and SL, respectively. The correlation between lactate and epinephrine was 0.93 and 0.84 for control and beta-blocked subjects, respectively. Whereas during exercise epinephrine was consistently higher for the beta-blocked group than controls, this difference was only significant during CH exposure. The epinephrine response was related to the extent of hypoxia in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1994

6-Hydroxydopamine lesions of the prefrontal cortex in monkeys enhance performance on an analog of the Wisconsin Card Sort Test: possible interactions with subcortical dopamine.

The effects of 6-hydroxydopamine lesions of the prefrontal cortex in monkeys were investigated on two cognitive tests of prefrontal function, spatial delayed response, and attentional set shifting. The latter test provided a componential analysis of the Wisconsin Card Sort Test, a commonly used clinical test of frontal lobe function in man. Acquisition of a visual compound discrimination requiring a shift of attention from one dimension to another (extradimensional shift), for example, shapes to lines, was significantly improved. This enhancement was behaviorally specific in that there were no effects on acquisition of a discrimination that required the continued maintenance of an attentional set toward one particular dimension (intradimensional shift), nor any effects on a series of visual or spatial discrimination reversals that involved the repeated shifting of responding between two exemplars from the same dimension. In contrast, spatial delayed response performance was impaired, in agreement with previous results. Neurochemical measures showed a marked depletion of dopamine limited to the prefrontal cortex and a smaller loss of prefrontal noradrenaline. This was accompanied by a long-term adaptive change in the striatum such that extracellular dopamine in the caudate nucleus, as measured by in vivo microdialysis, was elevated in response to potassium stimulation as long as 18 months postsurgery. It is proposed that attentional set shifting is mediated by a balanced interaction between prefrontal and striatal dopamine, and that elevated dopamine contributes to the improvement in attentional set-shifting ability. This interpretation is consistent with the impairment in attentional set-shifting ability observed in patients with Parkinson's disease or with damage to the frontal lobes using the same test as used here for infrahuman primates.

Animals↗
PubMed1993

Selective management of iatrogenic femoral artery injuries.

Increased femoral artery catheterization for therapy and diagnosis has resulted in a concomitant increase in iatrogenic femoral artery injuries. A 33-month experience at two affiliated institutions was reviewed to evaluate the results of a selective approach to management of these complications. During this period, 9576 femoral artery catheterizations were performed. Eighty-nine femoral artery injuries were treated surgically or by ultrasound-guided compression therapy. Cardiac catheterization procedures predominated and 61% of patients were anticoagulated. Thirty-eight cases were treated surgically: 14 pseudoaneurysms, 16 hematomas, 6 arteriovenous fistulas, 2 thromboses. Local anesthesia was used in 28 cases (74%). Arterial repair was required in 34 cases, with control being achieved below the inguinal ligament in 33 cases (97%). Punctures were found in the superficial femoral or profunda femoral rather than the common femoral artery in 17 of 38 cases (44%, P < 0.001 compared with the ultrasound group). There were two deaths (5.3%), six wound infections (16%), and no limb loss. Ultrasound-guided compression was preferentially used for stable or slowly expanding pseudoaneurysms. Cases with large hematomas causing skin ischemia were treated surgically. The pseudoaneurysms ranged from 2 to 7 cm in diameter. This technique was effective in 46 of 51 cases (90%). A single thromboembolic complication was treated by thrombolysis. There were no late recurrences. We conclude that (1) iatrogenic femoral artery injuries are associated with postcatheterization anticoagulation and punctures not located in the common femoral artery; (2) injuries requiring surgery can usually be treated under local anesthesia with infrainguinal arterial control; (3) ultrasound-guided compression is an effective method for treating iatrogenic pseudoaneurysms not associated with large hematomas.

Aneurysm↗
PubMed1993

Pulse-spray pharmacomechanical thrombolysis for treatment of thrombosed dialysis access grafts.

The results of pulse-spray pharmacomechanical thrombolysis (PSPMT) of 209 thrombosed hemodialysis grafts were reviewed. In PSPMT, concentrated urokinase is injected forcefully through catheters with multiple tiny sideholes or sideslits. Catheters placed in a crisscross fashion cover the entire clot simultaneously. This therapy was successful in treating patients with thrombosed grafts. Of the 200 grafts with complete therapy, 197 grafts (99%) were patent at the end of the procedure. Mean time for pulsed-spray lysis was 40 minutes. Etiologies for graft thrombosis were anastomotic venous outflow stenosis, stenosis of the venous outflow away from the anastomosis, arterial stenosis, intragraft stenosis, pseudoaneurysms, and no identifiable cause in a small percentage. There were 16 complications, 8 of which required additional therapy or potentially compromised the graft. These results suggest that pharmacomechanical thrombolysis and angioplasty provide rapid, consistent, and safe recanalization of thrombosed hemodialysis grafts and represent an additional therapeutic approach to graft management.

Angioplasty, Balloon↗
PubMed1993

Overtraining affects male reproductive status.

OBJECTIVE: To substantiate the hypothesis that strenuous exercise disrupts the hypothalamic-pituitary-gonadal axis in men. DESIGN: Longitudinal study. SETTING: Normal human volunteers in an academic research environment. PATIENTS: Five endurance-trained men (maximum oxygen consumption 65.4 +/- 3.6 mL/kg per minute [means +/- SEM]) with normal spermatogenic and hormonal profiles. INTERVENTIONS: Semen and blood samples were collected bimonthly before, immediately after, and 3 months after overtraining, which was defined as twice the previous average weekly training volume with unchanged intensity. MAIN OUTCOME MEASURE: Testosterone, cortisol, and sperm concentration. RESULTS: Basal T levels decreased to 5.37 +/- 67 ng/mL from 8.68 +/- 93 ng/mL (conversion factor to SI unit, 3.47) immediately after overtraining and basal cortisol levels increased to 215.3 +/- 31 ng/mL from 145.7 +/- 27 ng/mL (conversion factor to SI unit, 2.76). This inverse relationship was highly correlated (r = -0.92). Both cortisol and T levels returned to pretraining values 3 months after resumption of previous training volume. Sperm count (91 +/- 23.3 x 10(6)) decreased significantly by 43% immediately after overtraining (52 +/- 6.8 x 10(6)) and by 52% 3 months after overtraining (44.5 +/- 20 x 10(6)). However, all values remained within normal range and would not be expected to affect fertility. CONCLUSIONS: Our results indicate that overtraining reduces T levels, which is highly correlated with an increase in levels of cortisol and possibly a subsequent decrease in sperm concentration 74 days later.

Adult↗
PubMed1993

Contrasting mechanisms of impaired attentional set-shifting in patients with frontal lobe damage or Parkinson's disease.

Tests which assess the ability to shift cognitive set modelled after the Wisconsin Card Sorting Test are particularly sensitive to impairments in patients with Parkinson's disease as well as in patients with frontal lobe damage. However, the underlying mechanisms responsible for the similar deficits observed in the two patient groups are not well understood and may not be identical. For example, an apparent deficit in set-shifting ability may reflect either an impairment in the ability to shift from a perceptual dimension which has previously commanded attention (i.e. 'perseveration'), or in the ability to shift to an alternative perceptual dimension which has previously been irrelevant (i.e. 'learned irrelevance'). In this study, the performance of both medicated and non-medicated patients with Parkinson's disease were compared with a group of neurosurgical patients with localized excisions of the frontal lobes on a novel task designed to assess the relative contribution of 'perseveration' and 'learned irrelevance' to impaired set-shifting ability. Patients with frontal lobe damage were worse than controls in their ability to shift attention from a previously relevant stimulus dimension. Medicated patients with Parkinson's disease were worse at shifting to a previously irrelevant dimension. In contrast to both groups, nonmedicated patients with Parkinson's disease were impaired in both conditions. These results suggest that the gross set-shifting deficits reported in both frontal lobe patients and patients with Parkinson's disease may involve fundamentally different, though related, cognitive processes, and that these may be differentially affected by medication. Specifically, L-dopa therapy may protect Parkinson's disease patients from preservation of attention to a formerly relevant stimulus dimension.

Aged↗
PubMed1993

Occluded peripheral arteries and bypass grafts: lytic stagnation as an end point for pulse-spray pharmacomechanical thrombolysis.

Angiographic demonstration of luminal narrowing during pulse-spray pharmacomechanical thrombolysis (PSPMT) may reflect residual lysable clot, organized thrombus, platelet-rich clot, atherosclerosis, neointimal hyperplasia, or functional narrowing. The authors evaluated the efficacy and safety of lytic stagnation (initial rapid lysis followed by insubstantial further lysis with additional treatment) as an end point for PSPMT. Lytic stagnation was evaluated with serial angiography in 16 arterial and five bypass graft occlusions. Substantial lysis occurred after administration of mean doses of 512,000 units +/- 182,000 of urokinase or 5.3 mg +/- 2.0 of tissue-type plasminogen activator. Additional treatment with either of those agents produced minimal or no further change in the appearance of residual disease. Recanalization was successful in all patients after angioplasty. Distal emboli were noted in four cases, in three of which angioplasty of large intraluminal filling defects had been performed. The authors conclude that lytic stagnation is a reliable and safe end point for PSPMT in the absence of large intraluminal filling defects.

Adult↗
PubMed1992

A specific form of cognitive rigidity following excitotoxic lesions of the basal forebrain in marmosets.

The effects of N-methyl-D-aspartate-induced lesions of the basal forebrain were studied on performance of a series of visual discrimination tests that examined a range of cognitive functions in the marmoset. These included the ability to attend to the various dimensional properties of stimuli and to use just one of these properties in order to solve a discrimination (intra-dimensional shift); to switch attention from one dimension to another (extra-dimensional shift); to learn the reinforcement value of specific exemplars within a dimension (new learning); and to relearn their reinforcement value following reversal of the reward contingencies (serial reversals). Lesions of the basal forebrain did not impair the ability either to attend selectively to the dimensional properties of the stimuli or to switch attention from one dimension to the other. However, the lesion did affect various aspects of associative learning including a transient impairment of new learning and a marked disruption of serial reversal learning. The reversal deficit could be characterised as a tendency to perseverate on the previously correct stimulus and as a failure to to show the formation of a reversal learning set. In addition, the lesion prevented disruption of performance of a well-learned discrimination when novel exemplars from the irrelevant dimension were introduced (probe test). It is suggested that the functional effects of the basal forebrain lesion reflect impaired learning of stimulus-reward associations and behavioural rigidity. The finding, however, that there was no effect of the lesion on attentional set-shifting suggests that any loss of inhibitory control was specific to the level of stimulus-response or stimulus-reward associations, inhibitory control at the level of attentional selection remaining intact. The similarity of the effects of damage to the basal forebrain to those seen following damage to the orbitofrontal cortex and the amygdala are discussed in the context of the close anatomical and functional relationships that exist among these three structures.

Animals↗
PubMed1992

Venous imaging and inferior vena cava filters.

Thromboembolic disease is a major complication in many hospitalized patients. Imaging of deep venous thrombosis is important for making the diagnosis. After establishing the diagnosis, a decision must be made regarding anticoagulation. If the patient can not be anticoagulated, placement of an inferior vena cava filter is indicated. This paper discusses some of the latest information available on a variety of filters. However, a long-term multicenter study is needed to determine the effectiveness and safety of the available filters. A new approach to percutaneous insertion of central venous catheters is also discussed.

Catheterization, Central Venous↗
PubMed1991

Extra-dimensional versus intra-dimensional set shifting performance following frontal lobe excisions, temporal lobe excisions or amygdalo-hippocampectomy in man.

Attentional "set" shifting was assessed in a group of 20 neurosurgical patients with localized excisions of the frontal lobes, a group of 20 patients with unilateral temporal lobe lesions and a group of 11 patients who had undergone amygdalo-hippocampus removal. These three patient groups were compared with groups of both young (age-matched) and elderly normal control volunteers on a computerized test of visual discrimination learning involving both an intra- and an extra-dimensional shift. The frontal lobe group were selectively impaired in their ability to shift response set to a previously irrelevant dimension but not to shift attention to new exemplars of a previously relevant dimension. A similar pattern was observed in the elderly group of normal control volunteers. By comparison, both the temporal lobe patients and the amygdalo-hippocampectomy patients were unimpaired in their ability to perform either shift, although both groups had significantly prolonged selection latencies at the extra-dimensional shift stage of the task. These data are compared to previous findings from patients with idiopathic Parkinson's disease and are discussed in terms of a specific attentional set shifting deficit following frontal lobe damage.

Adult↗