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Biomedical subjects

P C Gordon

Publications and source records attributed to P C Gordon.

At least 37 records · Page 2Linked to original sources
PubMed1996

Intravenous tramadol versus epidural morphine for postthoracotomy pain relief: a placebo-controlled double-blind trial.

Tramadol, an analgesic deriving only part of its effect via opioid agonist activity, might provide postoperative pain relief with minimal risk of respiratory depression. We, therefore, evaluated it for the control of postthoracotomy pain. In this randomized, double-blind study, a single intravenous (IV) bolus dose of 150 mg tramadol (Group T) was compared to epidural morphine administered as an initial 2-mg bolus and subsequent continuous infusion at a rate of 0.2 mg/h (Group M). Patients in each group could receive morphine IV from a patient-controlled analgesia (PCA) device. Pain scores, morphine consumption, arterial blood gases, and vital capacity values were recorded at regular intervals postoperatively until 8:00 AM on the first postoperative day. Both groups obtained adequate pain relief, and there were no between-group differences in pain scores or PCA morphine consumption. Pao2 was significantly higher in Group T at 2 h and Paco2 significantly higher in Group M at 4 h postoperatively. There were no other significant respiratory differences. We conclude that a single dose of 150 mg tramadol given at the end of surgery provided postoperative analgesia equivalent to that provided by this dosage regimen of epidural morphine for the initial postoperative period.

Adult↗
PubMed1995

Lexical and prelexical influences on word segmentation: evidence from priming.

The authors examined the interaction of acoustic and lexical information in lexical access and segmentation. The cross-modal lexical priming technique was used to determine which word meanings listeners access at the offsets of oronyms (e.g., tulips or two lips) presented in connected speech. In Experiment 1, participants showed priming by the meaning of tulips when presented with two lips. In Experiment 2, priming by the meaning of the 2nd word was found in such sequences (e.g., lips in two lips). Finally, Experiment 3 demonstrated that listeners do not show priming by lips when it is pronounced as part of tulips. The results of these experiments show that listeners sometimes access words other than those intended by speakers and may simultaneously access words associated with several parses of ambiguous sequences. Furthermore, the results suggest that acoustic marking of word onsets places constraints on the success of lexical access. To account for these results, the authors propose a new model of lexical access and segmentation.

Humans↗
PubMed1995

Acute and long-term results of coronary stents and atherectomy in women and the elderly.

AIM: To determine the efficacy of new coronary interventions in women and the elderly. PATIENTS AND METHODS: We studied 504 patients who underwent a total of 567 procedures, comprising 275 directional coronary atherectomy and 292 Palmaz-Schatz stents over a 2 1/2 year period; 18% were women and 23% were aged > or = 70 years (elderly). RESULTS: High rates of success were obtained with these procedures in women and the elderly, although the rates were lower in women than in men (89 versus 96%, P = 0.005), and similarly lower in the elderly than in younger patients (91 versus 96%, P = 0.06). In addition to the lower success rates, there was a higher incidence of procedure-related non-Q myocardial infarction and vascular complications in both the women and the elderly, independently. The degree of angiographic restenosis (> or = 50% diameter stenosis), however, was similar in women (36 versus 28% in men, P = 0.22) and in the elderly (28 versus 29% in patients ages < 70 years, P = 0.8). There were no sex-related differences in survival, late myocardial infarction, or repeat revascularization. In the elderly, although the incidence of repeat revascularization was not increased, there was a decrease in late survival (P < 0.001) and an increase in the incidence of late myocardial infarction (P = 0.02), probably reflecting the presence of other co-morbid variables. CONCLUSION: Both directional coronary atherectomy and coronary stenting can be performed safely and effectively in women and the elderly with good long-term clinical results, despite a somewhat lower rate of success and similarly higher rates of acute complications.

Age Factors↗
PubMed1995

Pronominalization and discourse coherence, discourse structure and pronoun interpretation.

Two self-paced reading-time experiments are reported that examine the time course of pronoun interpretation processes based on local discourse structure and on world knowledge. The characterization of local discourse structure is based on recent work on centering, which provides a specific formulation of how the ways in which sentences make reference to common entities determines the coherence of discourse segments and how discourse structure influences interpretation of ambiguous pronouns. The results of the first experiment show that readers generate a default interpretation of a pronoun based on features of local discourse structure, and that that default interpretation is later confirmed or overridden by knowledge-based processes. The results of the second experiment show that local discourse structure continues to influence pronoun interpretation even when the semantic information that ultimately compels interpretation occurs before the pronoun. These results support the view that processes acting on local discourse structure play a powerful role in guiding language comprehension.

Adult↗
PubMed1994

Is 40% to 70% diameter narrowing at the site of previous stenting or directional coronary atherectomy clinically significant?

Traditional binary definitions of coronary restenosis based on 6-month continuous angiographic measurements (e.g., > 50% diameter stenosis) may give confusing results for lesions whose late percent stenosis falls near the arbitrary threshold. To determine the long-term clinical consequences of such lesions, the overall correlation between follow-up percent stenosis and the performance of subsequent ischemia-driven target vessel revascularization (triggered by significant angina or a positive exercise study result, or both) was examined in 443 consecutive lesions treated with directional coronary atherectomy or Palmaz-Schatz coronary stenting. Follow-up angiograms (available in 355 lesions, 82%) were stratified into 3 groups: severe late stenosis (> 70% stenosis, n = 59), moderate late stenosis (40% to 70% stenosis, n = 72), and minimal late stenosis (< 40% stenosis, n = 224). With an average clinical follow-up of 933 +/- 394 days, 92% of lesions in the "severe late stenosis" group were treated with ischemia-driven target vessel revascularization, compared with 0% of the lesions in the "minimal late stenosis" group. Ischemia-driven target vessel revascularization was performed in 38% of patients in the "moderate late stenosis" group. However, patients in this group who did not undergo revascularization (despite the fact that 43% of them had a late stenosis of > 50%) showed a similarly favorable long-term clinical outcome to patients with a minimal late stenosis. These results support a strategy of conservative management for the 20% of patients who have a moderate (40% to 70%) late stenosis after stenting or atherectomy, but do not have evidence of ischemia.

Atherectomy, Coronary↗
PubMed1994

Total intravenous anesthesia using propofol and alfentanil for coronary artery bypass surgery.

Total intravenous anesthesia (TIVA) using alfentanil and propofol was used in 10 patients undergoing coronary artery bypass grafting. In an attempt to diminish unwanted side effects, lower doses were chosen than if either drug had been used alone. Anesthesia was induced with alfentanil, 75 micrograms/kg, followed by a sleep dose of propofol (mean dose 0.5 mg/kg). Maintenance in the precardiopulmonary bypass (CPB) period was achieved by infusions of propofol (6 mg/kg/h) and alfentanil (100 micrograms/kg/h). These were decreased by two thirds on commencement of CPB, and increased to half the initial rate on rewarming to 32 degrees C. Additional boluses of alfentanil were used to control breakthrough hypertension. The mean arterial pressure (MAP) and left ventricular stroke work index (LVSWI) fell significantly on induction. MAP but not LVSWI returned to baseline levels at skin incision. The cardiac index (CI) was maintained. A degree of myocardial depression was suggested by a fall in LVSWI despite maintaining preload, and by the failure of CI to increase in the presence of a reduced SVR. Anesthesia was satisfactory in all but one patient who developed breakthrough hypertension on sternotomy with transient ST segment depression, and awareness after CPB despite a plasma alfentanil concentration of 450 ng/mL. Mean time to wakening was 55 minutes. The study indicated that TIVA using propofol and alfentanil in the dosages described provides satisfactory basal anesthesia for coronary artery bypass surgery in patients with good left ventricular function, but requires additional pharmacologic manipulation, particularly with boluses of alfentanil, to control breakthrough hypertension.

Adult↗
PubMed1994

Cardiogenic shock induced by cocaine in swine with normal coronary arteries.

OBJECTIVE: The aim was to test the hypothesis that acute intravenous cocaine administration can cause coronary microvascular constriction culminating in myocardial ischaemia and cardiogenic shock. METHODS: Systemic haemodynamic variables and coronary blood flow were measured in 14 Yorkshire swine at baseline and following intravenous administration of 1, 3, and 10 mg.kg-1 of cocaine. Epicardial coronary artery diameter was measured from coronary arteriograms and coronary flow velocity was recorded with a Doppler flow wire. RESULTS: Cocaine produced a decrease in mean arterial pressure (65%), cardiac output (80%), and stroke volume (80%), and an increase in pulmonary artery diastolic pressure (60%). Although coronary blood flow decreased by 70%, epicardial coronary cross sectional area decreased by only 37-45%. Pretreatment with prazosin did not abolish the decrease in coronary blood flow. After administration of 10 mg.kg-1 of cocaine, five of 14 animals developed myocardial ischaemia and cardiogenic shock, culminating in ventricular fibrillation and death. CONCLUSIONS: In anaesthetised Yorkshire swine, cumulative intravenous doses of cocaine caused a significant reduction in coronary blood flow resulting in myocardial ischaemia, which cannot be attributed to epicardial vasoconstriction alone. This suggest that cocaine-induced coronary ischaemia may result from microvascular constriction, which is only partially prevented by alpha 1 blockade. In addition, direct toxic effects of cocaine on the myocardium may also contribute to the development of cardiogenic shock.

Animals↗
PubMed1994

High-dose aprotinin in cardiac surgery--a prospective, randomized study.

Fifty patients undergoing primary coronary artery bypass surgery and 50 patients undergoing valve surgery received either high-dose aprotinin (2 million units loading dose, 2 million units added to the CPB prime, and 500,000 units/hr maintenance infusion) or placebo. Mean postoperative blood loss in the first six hours was reduced from 321 ml in the placebo group to 172 ml in the aprotinin group (95% confidence interval (CI) for difference = 95 to 189 ml). Seven patients in the placebo group and 16 patients in the aprotinin group did not require transfusion with homologous blood. This study adds to the growing body of evidence that the administration of high-dose aprotinin reduces blood loss and blood transfusion requirements associated with primary cardiac surgery.

Adolescent↗
PubMed1993

Balloon postdilation can safely improve the results of successful (but suboptimal) directional coronary atherectomy.

This study investigates whether adjunctive balloon angioplasty can be safely used to improve acute results in cases where directional coronary atherectomy alone has provided a successful (but suboptimal) outcome. Between October 1, 1990, and October 1, 1992, directional coronary atherectomy was performed successfully in 198 of 228 lesions. Individual operators believed that most acute results were satisfactory after atherectomy alone (group I, n = 115) with a minimal lumen diameter that increased from 0.82 +/- 0.45 to 3.21 +/- 0.65 mm after atherectomy, for an acute gain in lumen diameter of 2.39 +/- 0.73 mm and a residual stenosis of 6 +/- 13%. In 42% of lesions (group II, n = 83), however, results were considered suboptimal after atherectomy alone, with a minimal lumen diameter that increased from 0.85 +/- 0.45 to 2.83 +/- 0.64 mm, a smaller acute gain of 1.96 +/- 0.72 mm, and a mean residual stenosis of 17 +/- 14% (although all residual stenoses were < 50%, 19% had a residual stenosis > 30%). Adjunctive balloon angioplasty in these group II lesions provided an additional gain of 0.34 +/- 0.38 mm, bringing the total acute gain for group II lesions to 2.32 +/- 0.78 mm and the residual stenosis to 9 +/- 13%, similar to that of group I patients who underwent atherectomy alone. This strategy resulted in a 7 +/- 13% overall residual stenosis for the study population, with no higher incidence of periprocedural complications or adverse late clinical outcomes in group II patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1993

Attentional modulation of the phonetic significance of acoustic cues.

Four experiments addressing the role of attention in phonetic perception are reported. The first experiment shows that the relative importance of two cues to the voicing distinction changes when subjects must perform an arithmetic distractor task at the same time as identifying a speech stimulus. The contribution of voice onset time to phonetic labeling decreases when subjects are distracted, while that of FO onset frequency increases. The second experiment shows a similar pattern for two cues to the distinction between the vowels /i/ (as in "beat") and /I/ (as in "bit"). Under low attention conditions, formant pattern has a smaller effect on phonetic labeling while vowel duration has a larger effect. Together these experiments indicate that careful attention to speech perception is necessary for strong acoustic cues (voice-onset time and formant patterns) to achieve their full impact on phonetic labeling, while weaker acoustic cues (FO onset frequency and vowel duration) achieve their full impact on phonetic labeling without close attention. Experiment 3 shows that this pattern is obtained when the distractor task places little demand on verbal short-term memory. Experiment 4 provides a data set for testing formal models of the role of attention in speech perception. Attention is shown to influence the signal-to-noise ratio in the phonetic encoding of acoustic cues; the sustained phonetic contribution of weak cues without close attention stems from reduced competition from strong cues. This principle is instantiated in a network model in which the role of attention is to reduce noise in the phonetic encoding of acoustic cues. Implications of this work for understanding speech perception and general theories of the role of attention in perception are discussed.

Acoustic Stimulation↗
PubMed1993

Coming to terms with stress: effects of stress location in sentence processing.

The purpose of this research was to determine the role of syllabic stress in language processing during the early on-line processing of speech and later in the representation of a sentence in memory. Experiment 1 used a syllable monitoring task while Experiment 3 used a probe task in which subjects heard a sentence and then were asked to determine whether a probe syllable had occurred in the sentence. In the monitoring task, stressed syllables were detected more rapidly in word-initial position, but unstressed syllables were detected more rapidly in word-final position. Stress facilitation in initial syllables was strongly related to high relative F0, but not to changes in perceived vowel quality as assessed in Experiment 2. This pattern is interpreted as evidence that lexical stress is used on-line to guide lexical access and/or lexical segmentation. The probe task of Experiment 3 showed stress facilitation in both positions, indicating that stress is independently retained in the postperceptual representation of a sentence.

Adolescent↗
PubMed1993

Mechanisms of restenosis and redilation within coronary stents--quantitative angiographic assessment.

OBJECTIVES: This study was designed to assess the relative contributions of intimal hyperplasia and stent compression to the lumen narrowing seen after intracoronary stenting and to determine whether the lumen enlargement produced by angioplasty of in-stent restenosis results primarily from compression or extrusion of intimal hyperplasia through the stent or from additional stent expansion. BACKGROUND: Palmaz-Schatz stent placement outwardly displaces plaque and eliminates elastic vessel recoil to provide a large and smooth lumen. Some degree of late lumen narrowing occurs within each stent and causes significant restenosis (> or = 50% stenosis) in 25% to 30% of treated lesions. It has not been clear, however, whether this narrowing results from stent compression (crush) or from in-stent intimal hyperplasia. Because the Palmaz-Schatz stent has a distinct radiographic shadow, it is possible to determine the late diameter of both the stent and the enclosed vessel lumen to assess the relative contributions of these two processes. METHODS: From cineangiograms, initial (after stenting) and late (follow-up) lumen and stent diameters were examined in 55 patients (59 stents, group I) who had both immediate and 6-month (192 +/- 117 days) angiography. Lumen and stent diameter were also examined before and after dilation in 30 patients (30 stents, group II) who underwent angioplasty of severe in-stent restenosis. RESULTS: Late loss in minimal lumen diameter was 0.99 +/- 0.87 mm for group I despite only a slight (0.03 +/- 0.23-mm) reduction in the corresponding stent diameter. After redilation for in-stent restenosis, the acute gain in minimal lumen diameter was 1.51 +/- 0.82 mm for group II, again without appreciable increase (0.06 +/- 0.20 mm) in stent diameter. CONCLUSIONS: Restenosis after intracoronary Palmaz-Schatz stenting appears to be due predominantly to lumen encroachment by intimal hyperplasia within the stent, with minimal contribution of stent compression. Lumen enlargement after coronary angioplasty of in-stent restenosis appears to be due primarily to compression or extrusion of intimal hyperplasia through the stent, or both, rather than to further stent expansion.

Aged↗