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Biomedical subjects

D Silver

Publications and source records attributed to D Silver.

At least 73 records · Page 4Linked to original sources
PubMed1990

Children's understanding of private keys in referential communication.

A private key is a referential utterance used to inform selectively. The ambiguity of the utterance conceals meaning from nonselected audience members. The purpose of this study was to examine three aspects of children's understanding of the use of private keys. Experiment 1 concerned children's sensitivity to information in the context of utterance (i.e., the common ground). Experiment 2 examined appreciation of audience design and the speaker's intent. Experiments 3, 4, and 5 explored some reasons for children's problems in understanding private keys. The results show that even first graders are sensitive to common ground information and the speaker's intent. However, audience design is troublesome even for second graders in some situations, probably because they fail to assess the knowledge of the audience members. Private keys are important theoretically because they represent an aspect of referential communication involving the uses of ambiguous utterances that have been ignored by developmental researchers.

Attention↗
PubMed1990

The relation between item identification difficulty and elaborative conceptual processing for children and adults.

The four experiments concerned the relation between the difficulty of item identification processes, elaborative conceptual processing, and developmental differences in cued recall. Elaborative conceptual processing was manipulated by asking related ("How many are related?"), category ("How many are vehicles?"), and analytic ("How many usually carry freight?") orienting questions about four-word stimuli in which the words were categorically related (Bus-Airplane-Car-Train). The measures of elaborative processing were the speed and accuracy of question answers. Cued recall for the targets (Train) was assessed for one-word (Bus) or two-word (Bus-Airplane) cues, which were varied to determine if elaborative processing affected cue discriminability or constructability, or both. The difficulty of item identification was varied in several ways. In Experiment 1, the graphemic information was degraded in the acquisition stimuli, or the retrieval cues, or the stimulus words were intact. In Experiments 2 and 3, acquisition presentation time was varied and the stimuli were read by the experimenter or the subject. Experiment 4 featured pictures to determine generalizability. The results showed that elaborative conceptual processing facilitates recall. Most important, item identification processes limit elaborative conceptual processing for both words and pictures, and more for children than for college students.

Adolescent↗
PubMed1990

Heparin-induced thrombocytopenia in patients who undergo open heart surgery.

To determine whether heparin-dependent antiplatelet antibodies (HAAb) have an effect on morbidity and/or mortality rates, we reviewed the cases of 3438 patients who underwent open heart surgery from 1981 to 1989. Forty-six patients (1.3%) had HAAb. The patients were divided into two groups: those patients who were known to have HAAb before surgery (group I) and those patients who were diagnosed with HAAb after surgery (group II). Group I patients (n = 5) were pretreated with platelet-inhibiting drugs before reexposure to heparin during cardiopulmonary bypass and were maintained with strict abstinence from heparin afterward. Their lowest observed platelet counts ranged from 42,000/mm3 to 89,000/mm3 (median, 63,00/mm3). Thromboembolic complications did not occur, and all patients survived. Group II patients (n = 41) who were diagnosed to have HAAb after surgery had not been pretreated with platelet-inhibiting drugs before surgery. Lowest platelet counts ranged from 11,000/mm3 to 128,000/mm3 (median, 42,000/mm3). Bleeding complications occurred in 21 patients (51%), and thromboembolic complications occurred in 13 patients (32%). Hospital mortality in group II patients was 37%. Late recognition of HAAb was associated with an increase in morbidity and mortality rates. Thromboembolic complications of HAAb, which had been diagnosed before surgery, were eliminated, and bleeding was reduced by pretreatment with platelet-inhibiting drugs and strict abstinence from heparin after surgery.

Acute Kidney Injury↗
PubMed1990

Concept availability in the causal inferences of children and adults.

What supplies the concepts in causal inferences in story comprehension? This question was examined in 5 experiments. Elementary school children and college students listened to stories containing a "premise" sentence describing a character's intent in initiating a series of actions, followed by an unexpected "outcome." After each story, the subjects were asked inference questions about the reason for the outcome (Experiments 1-4) or asked to explain the outcome (Experiment 5). In the various experiments, the availability of object concepts for an inference was manipulated by providing 0 or 2 clues preceding the outcome, additional filler information that diluted the clue information, a mention of an object in the premise or no mention, and an object title for each story or no title. The results suggested that the availability of an object concept in sentences prior to the outcome was a critical determinant of whether an object inference occurred, especially for children. Given availability, the thematic prominence of the object influences whether the object will be used in an inference.

Adolescent↗
PubMed1989

Reexposure to heparin of patients with heparin-associated antibodies.

Four patients with heparin-associated antiplatelet antibodies who were not receiving platelet function-inhibiting agents received heparin during surgery, angiography, or hemodialysis. Three of the four patients had complications that were attributed to heparin-induced platelet aggregation. The complications included a superficial femoral artery thrombosis, a thrombotic stroke after a carotid endarterectomy, and recurring thrombosis of a graft inserted for dialysis. Nine patients received aspirin (325 mg b.i.d.) or dipyridamole (Persantine) (200 to 300 mg daily) before reexposure to 5000 to 12,000 units of heparin during 11 vascular procedures. The procedures included two carotid endarterectomies, three aortofemoral bypasses, one femoropopliteal bypass, two femorotibial in situ saphenous vein bypasses, one iliofemoral thrombectomy, one bilateral iliac artery angioplasty, and one axillobifemoral bypass. Platelet counts averaged 173,000/mm3 before heparin reexposure, fell to an average of 86,000/mm3 within 24 hours of heparin reexposure, and returned to normal within 48 hours after the reexposure. None of these patients had a thromboembolic or hemorrhagic complication. Patients with heparin-associated antiplatelet antibodies are at risk for developing thrombocytopenia and thromboembolic complications on reexposure to heparin. The platelet function-inhibiting agents, aspirin and Persantine, protect the patients from the thromboembolic complications but not the thrombocytopenia associated with limited heparin reexposure.

Angiography↗
PubMed1989

Transaxillary or supraclavicular decompression for the thoracic outlet syndrome. A comparison of the risks and benefits.

The difficult exposure with the transaxillary resection of the first rib (TAR) prompted an analysis of the TAR versus the supraclavicular approach (SCR) for decompressing the thoracic outlet in patients with thoracic outlet syndrome (TOS). Thirty-seven patients underwent 30 TAR and 15 underwent SCR for TOS. The operating time was similar for the two groups. Mean blood loss was 61 cc for the SCR group and 218 cc for the TAR group. There was one complication in the SCR group, a urinary tract infection, whereas the TAR group had 21 complications including pneumothorax (13), laceration of subclavian vessel (3), winged scapula (3), pleural effusion (1), and wound infection (1). Postoperative hospitalization averaged 3 and 5 days, respectively, for the SCR and TAR patients. All SCR patients and all but one TAR patient were improved or asymptomatic immediately postoperatively. Ninety-three per cent and 81 per cent, respectively, of SCR and TAR patients were improved at 2 months, whereas 100 per cent and 83 per cent, respectively, remained improved at a mean follow-up of 3 years. The significantly fewer complications, decreased blood loss and shorter postoperative hospitalization, noted in the SCR patients supports this approach as the preferred form of management for TOS.

Adult↗
PubMed1989

Thrombocytopenia associated with heparin-coated catheters in patients with heparin-associated antiplatelet antibodies.

Thrombocytopenia was associated with the presence of heparin-coated pulmonary artery catheters in 12 patients with heparin-associated antiplatelet antibodies. The thrombocytopenia persisted so long as the heparin-coated catheters were in place, even when all other sources of heparin were discontinued. The high morbidity and mortality associated with heparin-induced thrombocytopenia mandates that heparin administration cease and that all heparin-coated catheters be removed from patients with heparin-associated antiplatelet antibodies.

Aged↗
PubMed1988

Surgical management of refractory venous stasis ulceration.

A 15-year experience with 27 patients, 20 to 75 years of age, with refractory venous stasis ulcers is presented. All patients had been managed with support hose, elevation, elastic wraps, Unna's paste boots, and graduated compression stockings. Because of multiple recurrences of their ulcers, the patients were offered surgical treatment to reduce the venous hypertension in the areas of ulceration. The 27 patients had 32 modified Linton procedures. Five had bilateral procedures. At the time of operation, 18 limbs had medial malleolar ulcers, five had bimalleolar ulcers, four had lateral ulcers, three had posterior ulcers, and two patients were free of ulcer. Medial incisions were used in 20 limbs, lateral incisions in six, medial and lateral incisions in three, and midposterior incisions in three. Split-thickness skin grafts were placed on six limbs the day of surgery and on 22 limbs 4 to 7 days later. Postoperative complications included deep venous thrombosis in two, partial flap necrosis in three, and cellulitis of the lower leg in three patients. Follow-up has ranged from 6 months to 10 years. During the most recent clinic visits, 21 limbs were completely healed, whereas six limbs had a recurrence of the ulcer. Five patients have been lost to follow-up. The good long-term results in 78% of the cases indicate that patients with recurrent venous stasis ulcers may receive lasting benefit from modified Linton procedures.

Adult↗
PubMed1988

Heparin-coated catheters and heparin-induced thrombocytopenia.

Ten patients with heparin-coated pulmonary artery catheters had heparin-induced thrombocytopenia, which persisted after all other sources of heparin were discontinued. The thrombocytopenia occurred in approximately 0.4% of the patients receiving heparin-coated catheters and remitted when the catheters were removed. The platelet counts averaged 59,000/mm3 at the time of the diagnosis and recovered to an average of 143,000/mm3 by 3 days (range 2 to 4 days) after removal of the heparin-coated catheters. One patient required a second catheter 31 days after the first catheter had been removed. When the second heparin-coated catheter was inserted, the platelet count decreased from 307,000/mm3 to 102,000/mm3 in 4 days. Segments of heparin-coated pulmonary artery catheters were placed in platelet-rich plasma and incubated with serum from patients with known heparin-associated antiplatelet antibodies or with serum from volunteers with no exposure to heparin. The heparin-coated catheters induced platelet aggregation in all samples containing serum from patients with heparin-induced thrombocytopenia. However, platelet aggregation did not occur when the catheters were incubated with the serum of the volunteers. Non-heparin-coated catheters failed to produce platelet aggregation when incubated with either sera. The high mortality and morbidity rates associated with heparin-induced thrombocytopenia mandate that afflicted patients receive no more heparin, at least until the heparin-associated antiplatelet antibodies are no longer detectable. Patients with heparin-coated catheters who have thrombocytopenia should be tested for the presence of heparin-associated antiplatelet antibodies. If heparin-induced thrombocytopenia is confirmed, the catheters must be removed if the thrombocytopenia is to be reversed and complication avoided.

Aged↗
PubMed1988

Lower extremity edema from bladder compression of the iliac veins.

Two elderly men were referred to our vascular clinic for the management of bilateral lower extremity edema of 2 to 3 months' duration. Their evaluation included phlebograms, which demonstrated external compression of their iliac veins. CT scans of the pelvis suggested that large bladders caused the compression. Each patient had mild symptoms of prostatism. Transurethral resection of the prostate was recommended to and accepted by each patient. Decompression of the bladder was accompanied by complete relief of the lower extremity venostasis in both patients. Review of the literature yielded only eight similar cases of this unusual cause of lower extremity edema.

Aged↗
PubMed1988

Aneurysms and pseudoaneurysms of the superficial temporal artery caused by trauma.

Superficial temporal artery (STA) aneurysms as a result of trauma represent less than 1% of reported aneurysms. During the past 200 years only the type of trauma and the preferred treatment have significantly changed. Patients are generally young men with a recent history of blunt head trauma. They may complain of a mass, headache, or other vague symptoms. Neurologic defects are rare; however, if a neurologic deficit exists, the physician should consider either arteriography or a head CT scan to search for intracranial pathologic conditions. In most cases the diagnosis may be made by obtaining a complete history and physical examination. The treatment of choice is ligation and resection, which may be accomplished with the patient under local or general anesthesia. In rare instances, arteriography with selective embolization may be useful when the traumatic aneurysm is complicated by severe facial trauma. Three cases of STA aneurysms are presented. The history, pathophysiology, origin, presentation, diagnosis, differential diagnosis, and treatment of STA aneurysms are reviewed.

Adolescent↗
PubMed1988

Some determinants of individual differences in the behaviour of children of parentally deprived parents.

Parents who had been placed in an orphanage as children rated the behaviour of all their children who were between the ages of 6-18 years on a children's behaviour survey instrument. All families were intact and the parents had not requested professional help for marital problems. A significant number of relationships were found between parental background variables and higher reported levels of conflict with siblings and with parents, dependent-unassertive behaviour, and undemandingness in the children. Although sampling difficulties preclude generalization, the results suggest that repercussion of events in the lives of the first and second generation that are usually pathogenic may be seen in the third generation, even when the second generation may not be grossly adversely affected. These events most frequently related to individual differences in the third generation in the area of undercontrol of aggression directed toward parents and siblings.

Adaptation, Psychological↗
PubMed1988

Psychopathic adaptations in the vulnerable patient.

The purpose of this paper is to discuss the fluidity of symptoms that a group of psychiatric patients presents during the passage of time. Although clinically recognizable and worthy of attention, this fluctuation makes the illness difficult to conceptualize under a definitive diagnostic category. Such a dilemma is very familiar to the hospital psychiatrist. The authors present a case to illustrate the fluidity of symptoms manifested by a patient throughout the course of her illness. Awareness of the changing clinical presentations may alert us both to reformulate the patient on an ongoing basis, and to identify the different intervention needs at various points in time.

Adaptation, Psychological↗
PubMed1988

Should prophylactic anticonvulsants be administered to patients with newly-diagnosed cerebral metastases? A retrospective analysis.

We analyzed a retrospective series of 195 patients with documented intracerebral metastases (ICM) to assess the frequency of late seizure development and the impact of prophylactic anticonvulsants. Eighteen percent of the patients presented with seizures. Of the remaining patients, 40% received prophylactic anticonvulsants (diphenylhydantoin [DPH] in greater than 90%). Ten percent developed late seizures at an interval from the diagnosis of ICM ranging from 1 to 59 weeks. No patient with a posterior fossa lesion developed seizure; conversely, patients with evidence on initial examination of cerebral hemispheric dysfunction had a higher incidence of late seizure development. The incidence of seizure was virtually identical in patients who received DPH compared with those in whom it was withheld, although two thirds of patients who developed seizure while on DPH had a serum anticonvulsant level that was subtherapeutic. Based on the above findings and until prospective data become available, we recommend that anticonvulsants be withheld in newly-diagnosed patients with ICM until the first seizure.

Adult↗
PubMed1987

Reliability of continuous-wave Doppler probes.

Small-diameter, thin-walled latex tubes, through which a blood-simulating agent (0.1% suspension of simethicone in 0.9% sodium chloride) flowed at controlled rates, were embedded at varying depths in a tissue-mimicking matrix of powered graphite suspended in 4% agar. A continuous-wave (CW) Doppler probe was mounted at a 45-degree angle to the flow and passed transversely over the tube by a motorized drive mechanism at a rate of 0.42 mm/sec. Flow rates through the tubes were monitored with electromagnetic flow probes. The maximum depth from which quantitatively reliable signals could be obtained was 1.2 cm for 10 MHz probes and 3.3 cm for 5 MHz probes. Qualitative detection of flow was possible to a depth of 3.1 cm for 10 MHz probes and 7.0 cm for 5 MHz probes. The distances from the tube center for obtaining quantitatively reliable signals were limited to +/- 0.9 mm with a 10 MHz probe and +/- 1.8 mm with a 5 MHz probe. Qualitatively useful signals could be detected +/- 2.9 mm from the beam center by the 10 MHz probes and +/- 4.4 mm by the 5 MHz probes indicating a need for cautious interpretation as an interfering signal might be generated by any vessel within that range. Twenty percent of the randomly tested CW probes were considered unsuitable for use in quantitating blood flow, which underscores the importance of probe characterization before use.

Blood Flow Velocity↗
PubMed1987

The heparin-induced thrombocytopenia syndrome: an update.

One hundred sixty-nine patients with heparin-induced thrombocytopenia are reported and compared with the 62 patients reported in 1983. Prompt recognition of heparin-induced thrombocytopenia and immediate cessation of heparin administration lowered the complication and death rates from 61% (38/62) to 22.5% (38/169) and from 23% (14/62) to 12% (21/169), respectively. Platlet count and duration of heparin administration were not useful in predicting the outcome of the heparin-induced thrombocytopenia syndrome. Patients who received heparin in therapeutic doses were at higher risk for developing complications than were patients receiving lower doses of heparin. Platelet aggregation tests became negative as early as 7 days after discontinuation of heparin but persisted as long as 28 months. Heparin reexposure (2 days to 34 months after positive aggregation studies) was uneventful in 13 of 15 patients, whereas two patients suffered devastating thrombotic complications. Five patients continued to receive heparin despite positive platelet aggregation tests. The serious complications suffered by two of these five patients illustrate the necessity to discontinue heparin as soon as the diagnosis of heparin-induced thrombocytopenia is established.

Adolescent↗