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Biomedical subjects

N McIntosh

Publications and source records attributed to N McIntosh.

At least 109 records · Page 6Linked to original sources
PubMed1989

Bone mineralisation in preterm infants measured by dual energy radiographic densitometry.

Dual energy radiographic densitometry was used to follow postnatal changes in the bone mineral content of the radii of 15 infants of less than 30 weeks' gestation. The system permitted bone mineral content to be measured with minimal disturbance to the infants in their incubators. Mean bone mineral content at birth was 2.4 mg/mm shaft length, decreasing to 1.9 mg/mm at 6 weeks of age, before starting to rise. Mineralisation was poor compared with that of a fetus at an equivalent postconceptual age. Mean intakes of calcium and phosphate were considerably less than the intrauterine accumulation of these minerals and it is postulated that this was the main cause of the poor mineralisation. Radiographic densitometry is both accurate and precise and has advantages over photon absorptiometry in that it can be used to measure bone mineral in infants who are not only preterm, but also ill enough to require intensive care.

Aging↗
PubMed1989

Prognostic significance of programmed ventricular stimulation in survivors of acute myocardial infarction.

The prognostic significance of the response to programmed ventricular stimulation was studied in 75 stable survivors of acute myocardial infarction. Programmed ventricular stimulation induced sustained ventricular arrhythmias in 33 (44%) patients and did not induce these arrhythmias in 42 (56%) patients. During a mean follow up of 18 months, four patients died suddenly and three developed spontaneous sustained ventricular tachycardia. The occurrence of arrhythmic events was not significantly different in patients with inducible sustained arrhythmias and those without, but such events were predicted by the presence of mild congestive heart failure. Although the inducibility of sustained ventricular tachycardia (but not ventricular fibrillation) seemed to identify a high risk subset with an arrhythmic event rate of 21% compared with 5.5% in others, it had a low sensitivity (57%) and a low positive predictive accuracy (21%) for arrhythmic events. Programmed ventricular stimulation is not helpful in identifying a subset of patients at high risk after an uncomplicated acute myocardial infarction.

Arrhythmias, Cardiac↗
PubMed1988

Resistance to isosorbide dinitrate in patients with severe chronic heart failure: incidence and attempt at hemodynamic prediction.

Oral isosorbide dinitrate has been widely used to lower elevated left ventricular filling pressure in patients with chronic heart failure. Although the recommended dose of this drug is 40 mg every 6 h, failure to respond to this dose has been observed in many patients with heart failure. In the present study the incidence of resistance to isosorbide dinitrate was evaluated and an attempt was made to identify baseline hemodynamic predictors for this phenomenon in 50 patients with severe chronic heart failure due to left ventricular systolic dysfunction (mean left ventricular ejection fraction 0.23 +/- 0.08). Twenty-seven (54%) of the 50 patients responded to 40 mg of isosorbide dinitrate (greater than 20% decrease in mean pulmonary artery wedge pressure sustained greater than or equal to 1 h) and 23 patients (46%) failed to respond. Nonresponders to 40 mg of isosorbide dinitrate had a significantly higher baseline right atrial pressure than did responders (14 +/- 5 versus 10 +/- 6 mm Hg, p less than 0.02). In addition, all 7 patients with a baseline right atrial pressure of less than 7 mm Hg and 12 of 14 patients with a baseline right atrial pressure less than 10 mm Hg responded to 40 mg. No significant differences were noted between responders and nonresponders in any other baseline hemodynamic or clinical variables, or in peak isosorbide dinitrate serum levels (32 +/- 19 ng/ml in nonresponders versus 44 +/- 36 ng/ml in responders). Of the 23 nonresponders to 40 mg, 22 received a higher dose (80 to 120 mg).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Clinical issues.

Explore the source record for details and available documents.

Humans↗
PubMed1988

Blood counts in extremely low birthweight infants.

White blood, neutrophil, and platelet counts were higher in 101 infants with appropriate weight for gestational age than in 42 infants who were small for gestational age. The recognised postnatal rise in counts was seen in the infants of appropriate weight, but in the infants who were small for gestational age the counts fell for the first three days.

Blood Cell Count↗
PubMed1988

Dry lung syndrome after oligohydramnios.

We studied four infants whose mothers had had leaks of amniotic fluid for varying periods before birth. Three were associated with compression deformities. Oxygenation was achieved only by overriding the pressure limit safety devices on the resuscitation apparatus and ventilating after birth with high inflation pressures. In all cases the ventilation pressures had to be further increased for 12 hours but rapid improvement followed on the second day so that all four were spontaneously breathing air after a few days. It is postulated that collapse of the airways resulted from oligohydramnios, and that the resulting 'dry lungs' would only respond to high inflation pressures.

Amniotic Fluid↗
PubMed1987

Hemodynamic and volumetric effects of venodilation with nitroglycerin in chronic mitral regurgitation.

To evaluate the potential value of nitrate therapy in patients with chronic mitral regurgitation, the hemodynamic and angiographic effects of intravenous nitroglycerin were studied in 10 such patients. Nitroglycerin infusion, titrated to reduce mean pulmonary artery wedge pressure at least 20%, resulted in a significant reduction in mean blood pressure (from 91 +/- 12 to 77 +/- 13 mm Hg, p less than 0.0001), mean right atrial pressure (12 +/- 6 to 7 +/- 4 mm Hg, p less than 0.001), left ventricular end-diastolic pressure (22 +/- 7 to 13 +/- 5 mm Hg, p less than 0.0001) and peak V wave of indirect left atrial pressure (34 +/- 9 to 20 +/- 10 mm Hg, p less than 0.001). Changes in systemic vascular resistance (1,986 +/- 468 vs 1,582 +/- 534 dynes s cm-5) and forward stroke volume (39 +/- 14 vs 45 +/- 8 ml) were not statistically significant. Angiographic data showed a decrease in both end-diastolic and end-systolic left ventricular volumes (248 +/- 51 to 216 +/- 54 ml, p = 0.06 and 127 +/- 69 to 99 +/- 48 ml, p less than 0.05, respectively) and an improvement in ejection fraction, from 0.52 +/- 0.15 to 0.55 +/- 0.15 (p less than 0.05). There was no significant change in the group values for mitral regurgitant volume and fraction (from 85 +/- 32 to 72 +/- 32 ml and 67 +/- 10 to 64 +/- 5%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Central and renal hemodynamic effects and hormonal response to diltiazem in severe congestive heart failure.

The central and renal hemodynamic effects and the hormonal response to single doses of 60 mg and 90 mg of diltiazem were evaluated in 10 patients with severe chronic left ventricular (LV) systolic dysfunction (ejection fraction 0.22 +/- 0.08). Diltiazem administration resulted in only mild and mostly statistically insignificant changes. After 60 mg, only heart rate (from 86 +/- 10 beats/min at baseline to 79 +/- 14 beats/min at 4 hours) and pulmonary vascular resistance (from 231 +/- 108 to 165 +/- 74 dynes s cm-5 at 4 hours) changed significantly. Administration of 90 mg of diltiazem resulted in no significant change in any of the measured or calculated central hemodynamic variables. Individual data, however, revealed an increase stroke volume index in 3 patients but a decrease in 1 patient and a persistent increase in mean pulmonary artery wedge pressure in another patient. These hemodynamic changes were not associated with symptomatic deterioration in any of the patients. Both renal blood flow and glomerular filtration rate were impaired at baseline on both days and did not show a significant change 1, 2 and 4 hours after diltiazem administration. Similarly, no significant change was noted after either diltiazem dose in plasma catecholamine levels and renin concentration. In conclusion, administration of 60 to 90 mg of diltiazem in patients with severe chronic LV systolic dysfunction results in only mild and mostly insignificant acute effects on central and renal hemodynamics, plasma hormonal levels and patient clinical status.

Diltiazem↗
PubMed1987

Radiological rickets in extremely low birthweight infants.

Forty-eight infants of birthweight less than 1000 g who survived for more than 28 days, had wrist X-rays to prospectively determine the incidence of radiological rickets. Twelve infants (25%) had normal X-rays throughout, 10 infants (21%) showed osteopenia and 26 infants (54%) had classical changes of rickets of which 8 (17% of the total) had spontaneous fractures. There was poor correlation between peak values of serum alkaline phosphatase and the radiological changes.

Alkaline Phosphatase↗
PubMed1987

Preterm blood counts vary with sampling site.

In preterm babies both haemoglobin and total neutrophil count values from capillary sites are significantly and variably higher than those from simultaneous arterial samples. Comparing simultaneous venous and arterial samples, the mean haemoglobin was slightly higher but the total neutrophil counts were similar.

Arteries↗
PubMed1987

Incidence of early tolerance to hemodynamic effects of continuous infusion of nitroglycerin in patients with coronary artery disease and heart failure.

Sustained therapy with nitroglycerin (NTG) has been reported to provoke the development of early tolerance. Because continuous intravenous NTG infusion is commonly used in patients with coronary artery disease and heart failure, we evaluated the incidence of early tolerance developed within the first 24 hr of therapy in 31 responders to NTG. After documentation of response to NTG, defined as a 10 mm Hg or greater or a 30% or greater reduction in mean pulmonary arterial wedge pressure (PAWP), 16 patients were blindly, randomly assigned to receive placebo and 15 patients were continued on same-dose NTG. Both groups showed an identical fall in PAWP at peak NTG titration (11 +/- 4 mm Hg). Discontinuation of NTG in the placebo group resulted in a rapid increase in PAWP to levels not significantly different from baseline (19 +/- 5 mm Hg at 2 hr vs 23 +/- 6 mm Hg at baseline; p = NS). In the NTG group, PAWP fell from 27 +/- 9 to 14 +/- 7 mm Hg, was 16 +/- 9 mm Hg at 2 hr (p less than .05 vs baseline), and continued to be significantly lower than baseline for 8 hr; however, due to attenuation of effect, PAWP values at 12, 20, and 24 hr were not significantly different from placebo or baseline values.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

Effects of intravenously infused Fluosol-DA 20% in rats.

Rats were injected with a fractionated 50 ml/kg dose of Fluosol-DA 20% with and without exposure to 100% oxygen. Animals were killed at 24, 43, 92, and 183 days post-treatment and samples taken for hematological, hepatic enzyme, histological, and perfluorochemical analyses. There were no significant differences in hemograms or hepatic enzyme findings between treatment and control groups. Differences in organ weights and histology were a result of perfluorochemical (PFC) accumulation in the tissues of treated animals. All changes were reversible. There were no effects from breathing high oxygen levels in either treatment or control animals.

Animals↗
PubMed1986

A clinical trial of Fluosol DA 20% in advanced squamous cell carcinoma of the head and neck.

Fluosol DA 20% (Fluosol) enhances the response of several rodent tumors to radiation and oxygen. This is a Phase I/II study of Fluosol and oxygen breathing in the radiation treatment of advanced squamous cell carcinoma of the head and neck. Fifteen patients with Stage III/IV tumors entered and completed this trial. Patients received 1.8 Gy/fraction to 45 Gy, at which time the spinal cord was shielded and gross disease was carried to 68-72 Gy. 8 ml/kg (11 patients) or 9 ml/kg (4 patients) Fluosol was infused prior to the first fraction each week for the first 5 weeks. All patients inspired 100% oxygen before and during the initial 25 fractions. The infusions were well-tolerated. Four acute reactions that responded to diphenhydramine or steroids were observed in the 75 infusions. 8/15 patients exhibited liver function abnormalities of 2-3X normal which fell after therapy was discontinued. Normal mucosal reactions were enhanced despite the 1.8 Gy fraction size. 10/15 patients required at least one treatment break: the mean dose achieved before the break was 35 Gy. Tumor clearance was also accelerated. Thirteen patients had primary tumor clearance, but one had a local recurrence. Ten had primary and nodal clearance and 2/3 with nodal persistence had salvage surgery with fibrosis only at pathologic review. One patient, locally controlled, developed distant metastases. Thus, 10/15 patients are NED, but followup time is short.

Carcinoma, Squamous Cell↗