Search PubMed⌕ Search

Biomedical subjects

D J Doyle

Publications and source records attributed to D J Doyle.

At least 127 records · Page 7Linked to original sources
PubMed1985

An evaluation of suloctidil in the prevention of deep vein thrombosis in neurosurgical patients.

Suloctidil (200 mg t.i.d.) was compared with placebo in a randomized, double-blind trial to assess its value in preventing deep venous thrombosis (DVT) in high-risk neurosurgical patients, comprising 136 patients with brain or spinal tumour, head or spinal injury, or subarachnoid or intracranial hemorrhage. 125I fibrinogen leg scanning and impedance plethysmography were performed for up to 14 days to detect DVT. The two groups were also evenly balanced for DVT risk factors. Seventeen of 68 patients (25%) (95% confidence interval, 15-35%) treated with suloctidil and 12 of 68 patients (21%) (95% confidence interval, 11-32%) treated with placebo developed deep venous thrombosis. This observed difference in outcomes is not statistically significant (X2 = 1.096; p = 0.30). The estimated 95% confidence interval for the true difference in the incidence of DVT between suloctidil-treated and placebo-treated patients ranges from an 11% benefit in favour of suloctidil to an 18% benefit in favour of placebo. Major deep vein thrombosis occurred in two patients on suloctidil and three patients in the placebo group; there were no fatal pulmonary emboli during the 14-day study period, during which time four patients in each group died of non-thromboembolic complications. There was no observed difference in hemorrhagic complications. Long-term outcomes at three-months follow-up were similar between the two treatment groups. It is concluded that there is no real evidence that suloctidil (200 mg t.i.d.) is an effective regimen for the prevention of DVT in high-risk neurosurgical patients.

Brain Neoplasms↗
PubMed1983

The polarity histogram in relation to the average evoked potential.

It is shown analytically that the polarity histogram (PH) and the average evoked potential (AEP) are linearly related under certain conditions. The relative merits of the two approaches are compared both analytically and by statistical simulation. In general, the PH is a biased estimator of the evoked potential and is less efficient than the AEP, which is unbiased. The PH is more robust against artifact, but this advantage vanishes when conventional artifact rejection is used. The detection of an EP using the PH is problematic. The polarity histogram offers little advantage over signal averaging under typical clinical recording conditions.

Electroencephalography↗
PubMed1983

Pulmonary angiography, ventilation lung scanning, and venography for clinically suspected pulmonary embolism with abnormal perfusion lung scan.

Inherent contradictions in current diagnostic recommendations for pulmonary embolism have created considerable confusion and controversy. To resolve these contradictions, we did a prospective study of ventilation-perfusion scanning, pulmonary angiography, and venography in consecutive patients with clinically suspected pulmonary embolism and abnormal perfusion scans. Ventilation scanning increased the probability of pulmonary embolism in patients with large perfusion defects and ventilation mismatch, but a ventilation-perfusion match was not helpful in ruling out pulmonary embolism. Small perfusion defects with mismatch had neither sufficiently high nor low probability to be of diagnostic value. The observed frequency of proximal vein thrombosis (19% to 51%) and its association with the range of ventilation-perfusion defects have important implications for management of pulmonary embolism. Pulmonary angiography is required in combination with venography in most patients with perfusion abnormalities because the probability of pulmonary embolism is neither sufficiently high nor low to confirm or exclude pulmonary embolism.

Adolescent↗
PubMed1982

Platelet function in coronary artery disease: effects of coronary surgery and sulfinpyrazone.

Platelet survival and plasma concentrations of beta thromboglobulin and platelet factor 4 were measured in 44 patients before and 6 months after coronary artery bypass grafting. Postoperatively, patients were randomized to receive sulfinpyrazone, 800 mg/day, or placebo. Preoperatively, platelet survival was significantly shorter than normal, and plasma concentrations of both platelet-specific proteins were significantly elevated. Postoperatively, all three indexes of platelet function tended to become normal, but these changes were statistically significant only in patients treated with sulfinpyrazone. Postoperative exercise testing correlated significantly with plasma concentrations of beta thromboglobulin and platelet factor 4 measured preoperative and postoperative. These results are consistent with reports of the effects of sulfinpyrazine on platelet involvement in other conditions, and suggest that the drug reduces platelet activation and inhibits actual destruction. The results also show a relationship between abnormalities of platelet function and an index of postoperative myocardial ischemia.

Angina Pectoris↗
PubMed1981

Bessel filtering of brain stem auditory evoked potentials.

It has been shown previously that conventional high-pass filtering of the brain stem auditory evoked potential (BAEP) results in significant wave form distortion. This distortion can be drastically reduced by using digital filters with zero-phase properties, but this approach requires the use of a digital computer. The Bessel filter is an approximation to a linear phase characteristic, and has the advantage that it may be implemented using analog circuitry. We have considered its use as an alternative-to-digital zero-phase filtering. For the low-pass case, the Bessel phase characteristic is approximately linear throughout the pass band. However, for the high-pass case there is significant phase non-linearity extending well into the pass band. Typical Bessel high-pass filters seriously distort the BAEP wave form; thus, these filters are not an acceptable alternative to the zero-phase digital approach.

Adult↗
PubMed1981

Analogue and digital filtering of auditory brainstem responses.

Auditory brainstem responses (ABRs) to monaural 70 dB nHL clicks in normal adults were recorded with wide bandwidth and stored digitally. Using digital to analogue conversion with expanded time, the ABRs were input to a variable band-pass filter. The order of averaging and filtering was unimportant. Low-pass effects were unremarkable. High-pass filtering in the commonly used range 20 Hz to 500 Hz produced severe waveform distortion, causing emergence of artifactual peaks, amplitude increase and decrease, absolute latency decrease and interpeak interval changes. Digital high-pass filtering gave identical results. The distortion increased with the filter order. Using a zero phase characteristic drastically reduced ABR distortion and abolished latency changes except for poorly resolved peaks. Butterworth and boxcar filter moduli gave identical results. At common high-pass frequencies, filter phase distortion dominated the mean square error in ABR estimation. Off-line digital filtering of ABR is both practicable and desirable, especially for facilitating inter-laboratory pooling of data.

Acoustic Stimulation↗
PubMed1981

Digital inverse filtering of distorted auditory brainstem responses.

Analogue filtering of source data can cause severe distortion of ABR waveform, primarily due to filter phase non-linearity. This distortion contributes to incompatibility between laboratories. Digital zero-phase filtering of the average ABR obtained with wide bandwidth gives much less distortion, but can cause difficulties with data acquisition protocols. We have investigated digital phase-correction of distorted average ABRs recorded with conventional filters. The method is successful and feasible. It is also possible to digitally recover the ABRs that would have been obtained with wider recording bandwidths, or with different filter orders. This approach can be used for conversion of ABR waveforms to a standard low-distortion filter condition, or to convert between conventional filter conditions used in different laboratories.

Acoustics↗
PubMed1980

Plasma concentrations of platelet-specific proteins correlated with platelet survival.

Relationships between 51Cr platelet survival and plasma concentrations of beta-thromboglobulin (betaTG) and platelet factor 4 (PF4) were analyzed in 91 studies of patients with coronary artery disease. betaTG was significantly correlated with platelet life-span, turnover, and the number of hits in the multiple hit model. PF4 was significantly correlated with life-span and turnover. The most significant relationship involving platelet-specific protein concentrations and life-span estimates was between betaTG and life-span estimated using the multiple hit model (r = -0.39, p less than 0.001). There was a high correlation between betaTG and PF4 (r = 0.62, p less than 0.001), and no improvement could be obtained by combining the measurements of the two proteins in any regression with life-span or turnover. The results indicate that the patients with the shortest platelet survival time in this group tended to have the highest plasma concentration of betaTG and PF4 and thus probably increased in vivo release of betaTG and PF4. They strengthen the claim that these platelet-specific proteins may be indicators of platelet involvement in disease.

Blood Platelets↗
PubMed1978

Plasma levels of platelet factor 4 measured by radioimmunoassay.

A radioimmunoassay has been developed to measure platelet factor 4 (PF4) in biological fluids both in vitro and in vivo. The assay has been shown to be highly specific for PF4 and has a sensitivity of 0.08 ng/assay tube and 1.6 ng/ml of plasma. The preparation of plasma for the measurement of in vivo levels of PF4 requires the use of an anticoagulant containing EDTA, theophylline and prostaglandin E1, the immediate cooling of the blood and high speed or prolonged centrifugation to reduce platelet contamination. Plasma levels of PF4 are normally between 4 and 24 ng/ml with a median of 7.4 ng/ml. Plasma PF4 levels are markedly increased during cardiopulmonary bypass surgery with shortened 51Cr-labelled platelet survival times and during arterial thrombosis. However, despite similarly shortened platelet survival times, the level of PF4 is normal in immune thrombocytopenia. Elevations of plasma PF4 levels are found following surgery, acute myocardial infarction and frequently during acute infections and in inflammatory states. On the contrary, normal levels are usual in disseminated malignancy, in severe hepatic and renal disease and in chronic arterial disease. The measurement of PF4 is a useful addition to the study of platelet pathophysiology. It is apparent, however, that raised levels are by no means specific for thromboembolic disease and similarly platelet destruction is not invariably associated with abnormally increased plasma PF4 levels.

Adult↗
PubMedDate not supplied

Ketamine induction and monoamine oxidase inhibitors.

A 42-year-old woman taking tranylcypromine, a monoamine oxidase (MAO) inhibitor, was hypovolemic from a ruptured ectopic pregnancy and required an emergency laparotomy. Anesthetic induction with ketamine, an agent with sympathomimetic properties, was used because of her hypovolemia, despite theoretical concerns of precipitating an adrenergic crisis. The patient's hemodynamic course remained unchanged with induction and intubation, and with further fluid and blood administration, satisfactory hemodynamic conditions were obtained. This report is believed to be the first to describe the use of ketamine in a patient taking MAO inhibitors.

Adult↗