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Biomedical subjects

D A Chamberlain

Publications and source records attributed to D A Chamberlain.

At least 73 records · Page 4Linked to original sources
PubMed1982

Ocular changes resulting from therapy with amiodarone.

Amiodarone, a powerful antiarrhythmic agent recently made available in Britain, is known to cause corneal changes, but the clinical implications of this unwanted effect are still controversial. We have made serial observations on 105 patients treated with the drug for periods ranging from 3 months to over 7 years. Corneal abnormalities were detected by slit-lamp examination in 103 patients (98%). These always progressed over several months but subsequently showed a stable pattern which changed only with alteration of dose. The abnormalities regressed and disappeared within 7 months in the 16 patients whose treatment was discontinued for reasons unconnected with ocular changes. No macular changes or permanent sequelae occurred. Ocular symptoms were unusual: 6 patients had reactions in the skin of the eyelids, and 6 others had minor symptoms related to the corneal changes. We do not believe that ophthalmological surveillance is mandatory in asymptomatic patients on long-term amiodarone therapy.

Adult↗
PubMed1982

The effects of amiodarone on thyroid function.

The effects of amiodarone on thyroid function tests in 100 patients treated for 6 weeks to 8 years are reported. One patient became thyrotoxic and 10 developed latent or overt hypothyroidism. Twenty-five patients remained clinically euthyroid throughout, but had free thyroxine indices above the normal range. In these patients with apparently anomalous results, total tri-iodothyronine was normal in 19 cases and low in 1; conversely, free thyroxine was high in all 17 cases in which it was measured. Thyrotrophin releasing hormone (TRH) tests were abnormal in 4 of the 13 patients who had the test. Reverse tri-iodothyronine was significantly raised after 2 weeks amiodarone in 5 healthy subjects, but an equivalent amount of iodine in 9 healthy individuals did not significantly affect any of these tests. We believe that these changes are due in part to inhibition of peripheral conversion of thyroxine to tri-iodothyronine with diversion to reversed tri-iodothyronine. Thyroid function tests should be checked once or twice a year in all patients on maintenance amiodarone. Tests indicating hypothyroidism are likely to be clinically relevant, whereas levels of thyroxine suggesting thyrotoxicosis may be misleading and do not usually imply the need to discontinue treatment with the drug.

Adult↗
PubMed1981

Pulmonary oedema without critical increase in left atrial pressure in acute myocardial infarction.

Twelve patients with acute myocardial infarction and radiological evidence of pulmonary oedema were observed in whom the left atrial pressure, measured indirectly as pulmonary artery end-diastolic pressure, was not critically increased (range 5-12 mm Hg with reference to sternal angle). Eight of the patients had been treated with frusemide, but only six had responded: hence in at least half of the series diuresis could not account for the anomalous finding. Six patients with low cardiac output were given infusions to expand plasma volume. Appreciable increments in mean values for cardiac index (1.6 to 2.0 1/min/m2), stroke index (18 to 23 ml/beat/m2), mean arterial pressure (65 to 86 mm Hg), and pulmonary artery end-diastolic pressure (8 to 15 mm Hg) were recorded. This group, and the remaining six patients with higher cardiac output, survived to leave hospital. Delay in radiographic clearing after a fall of left atrial pressure was a possible explanation for the relatively low pulmonary artery end-diastolic pressures, especially in the patients treated successfully with diuretics. Other mechanisms, such as alterations in pulmonary vascular permeability, might also have contributed to the syndrome. Pulmonary oedema without a critical increase in the left atrial pressure is unusual in acute myocardial infarction but the therapeutic implications are important. Withdrawal;of diuretics may be indicated, and in some cases expansion of plasma volume may lead to striking clinical improvement.

Aged↗
PubMed1981

Comparison of haemodynamic responses to dopamine and salbutamol in severe cardiogenic shock complicating acute myocardial infarction.

Twelve patients with severe persistent cardiogenic shock complicating acute myocardial infarction underwent single crossover treatment with intravenous dopamine and salbutamol to determine the more beneficial therapy. Salbutamol (10 to 40 microgram/min) reduced systemic vascular resistance and progressively increased both cardiac index and stroke index. Heart rate increased from 95 to 104 beats/min. Changes in mean arterial pressure and pulmonary artery end-diastolic pressure were small and insignificant. Dopamine infusion at rates of 200 and 400 micrograms/min also increased cardiac index and stroke index. Systemic vascular resistance fell slightly but mean arterial pressure rose from 57 to 65 mm Hg. Heart rate increased from 95 to 105 beats/min. Changes in pulmonary artery end-diastolic pressure were again small and insignificant. Dopamine infusion at 800 micrograms/min caused an appreciable increase in systemic vascular resistance; a further increment in mean arterial pressure was observed, though cardiac index fell slightly. Heart rate and pulmonary artery end-diastolic pressure rose steeply. Salbutamol, a vasodilator, increased cardiac output in patients with cardiogenic shock complicating acute myocardial infarction but did not influence blood pressure. If correction of hypotension is essential dopamine in low doses may be the preferred agent. Doses of 800 microgram/min, which is within the therapeutic range, worsen other manifestations of left ventricular dysfunction.

Albuterol↗
PubMed1980

Policy for early discharge after acute myocardial infarction.

Simple criteria were used to select a low-risk group of patients after acute myocardial infarction. The criteria depended on the presence or absence of diabetes, pulmonary oedema, serious rhythm disorders, and recurrent cardiac pain. Patients in the low-risk category with a suitable home environment were discharged from hospital after five to seven days (mean 6.2 days); they constituted 47% of the 267 hospital survivors over 18 months. Mortality in the selected patients was 2.4% at six weeks and 7% at one year. Most complications preventing early discharge were identified on the first day. Provisional selection for a short hospital stay was made after two days, and 76% of those judged suitable at 48 hours remained free of complications. Early selection of a low-risk category is justifiable and of practical value, though subsequent events will delay discharge for some patients. All patients who died in hospital or within two weeks after infarction had developed overt complications by the end of the fourth day. The results suggest that a policy of hospital discharge after four days would be justifiable for a low-risk group selected by the present criteria.

Aged↗
PubMed1980

Haemodynamic effects of intravenous morphine in patients with acute myocardial infarction complicated by severe left ventricular failure.

The haemodynamic effects of intravenous morphine sulphate (0.2 mg/kg body weight) were measured in 10 patients with acute myocardial infarction complicated by severe left ventricular failure. Fifteen minutes after morphine injection there was a significant fall in mean heart rate (from 109 to 101 beats/min) and mean systemic arterial pressure (from 80 to 65 mm HG), and a small fall in mean cardiac index (from 2.4 to 2.21/min/m2). Haemodynamic changes at 45 minutes were similar. Neither stroke index nor indirect left ventricular filling pressure (measured as pulmonary artery end-diastolic pressure) were consistently improved 15 or 45 minutes after injection. The useful action of morphine in relieving distressing cardiac dyspnoea is not adequately explained by systemic venous blood pooling. These results suggest that the effects of morphine on the central nervous system are more important.

Aged↗
PubMed1980

Synergistic effects of a combined salbutamol-nitroprusside regimen in acute myocardial infarction and severe left ventricular failure.

The haemodynamic effects of a simultaneous infusion of salbutamol and nitroprusside were measured in 20 patients with acute myocardial infarction and severe left ventricular failure. Six patients also had clinical manifestations of cardiogenic shock. Ten patients received salbutamol first with the subsequent addition of nitroprusside; in the other 10 patients nitroprusside was infused first. Salbutamol was infused at a constant rate of 20 micrograms/min in all patients, while the dose of nitroprusside, which averaged 51.25 micrograms/min, was adjusted to reduce left ventricular filling pressure (measured as pulmonary artery end-diastolic pressure) to approximately 15 mm Hg with reference to sternal angle. Cardiac index increased in all patients from a mean of 1.8 to 2.6 l/min/m2 while pulmonary artery end-diastolic pressure fell significantly from 24 to 16 mm Hg. The adverse effects were small in most patients: heart rate did not increase significantly and systolic arterial pressure fell on average from 112 to 96 mm Hg. Ten of the 20 patients survived to leave hospital. Nitroprusside accounted for most of the fall in filling pressure irrespective of treatment sequence, whereas both drugs contributed to the augmented cardiac output. The haemodynamic benefits of this combined regimen were considerably greater than those achieved by either drug alone. Thus salbutamol and nitroprusside have synergistic effects which influence favourably the two principal manifestations of left ventricular dysfunction after extensive myocardial infarction.

Aged↗
PubMed1980

A flexible signal-averaging system for cardiac waveforms.

The repetitive nature of cardiac waveforms renders them suitable for processing by signal averaging. A flexible system is described, based on a general-purpose digital computer, capable of averaging a variety of cardiac signals in excess of 0.5 microV containing frequency components below a theoretical Nyquist limit of 5 kHz. Important features of the system include real-time processing capability at a high level of interactive control, and the facility to trigger the averaging process accurately from any part of either the data or a synchronous reference waveform. Application of the system to electrocardiographic and phonocardiographic signals at conventional gain has enabled clinically useful records to be obtained in the face of obtrusive environmental noise. The averaging of signals of a similar nature after considerably increased amplification has revealed cardiac activity unseen in conventional records in a total of 81 subjects.

Analog-Digital Conversion↗
PubMed1979

Haemodynamic effects of salbutamol in patients with acute myocardial infarction and severe left ventricular dysfunction.

The haemodynamic effects of salbutamol infusions at rates of 10,20, and 40 micrograms/min were measured in 11 patients with acute myocardial infarction complicated by left ventricular failure. Four patients also had cardiogenic shock. Consistent increases were observed in cardiac outputs at all doses (up to 56% at 40 micrograms/min), while the mean systemic arterial pressure fell slightly (average 5 mm Hg), implying a reduction in peripheral vascular resistance. Changes in right atrial pressure and indirect left atrial pressure (measured as pulmonary artery end-diastolic pressure) were small and not significant. Analysis of data from individual patients showed that the greatest increment in cardiac output was reached at 10 micrograms/min in two cases, 20 microgram/min in three, and 40 micrograms/min in the remaining six. Heart rate at these doses increased by an average of only 10 beats/min. Salbutamol failed to reduce left ventricular filling pressure and cannot be recommended for the treatment of pulmonary oedema in acute myocardial infarction. The increase in cardiac output, however, was considerable, so that the drug may be important in the management of low-output states. This action is probably a result of peripheral arteriolar dilatation (itself a result of beta 2-adrenoreceptor stimulation) and is achieved with little alteration in the principal determinants of myocardial oxygen requirement.

Adult↗
PubMed1979

Hospital resuscitation from ventricular fibrillation in Brighton.

The overall results over three and a half years of the treatment of ventricular fibrillation secondary to ischaemic heart disease in the Royal Sussex County Hospital were reviewed. Records of all patients who were brought to hospital by resuscitation ambulances or who were admitted to the coronary care unit from any source were analysed. Eighty-seven of the 174 patients (50%) who developed ventricular fibrillation were discharged. The survivors included 13 out of 61 patients (21%) in whom fibrillation was secondary to cardiogenic shock or severe left ventricular failure. The presence of resuscitation equipment and nursing staff trained to use it in the general wards and emergency areas ensured a uniformly high success rate throughout the hospital, similar to that achieved in the coronary care unit. Prompt defibrillation in the general wards and the accident and emergency department may improve overall survival.

Adult↗
PubMed1979

1028 neonatal electrocardiograms.

Electrocardiograms were recorded from 1028 (99.4%) of 1034 consecutively born babies on the 1st or 2nd day of life. Abnormalities of cardiac rhythm or conduction were found in 49 (4.8%) babies. 17 babies had single or multiple premature beats during the recordings, and 7 babies showed sudden increases in R-R interval possibly due to sinoatrial node dysfunction. One baby had sinus or junctional bradycardia of less than 80 beats/min. One baby had an incessant reciprocating tachycardia and subsequently required digoxin for heart failure. Continuous 24-hour ECG monitoring in 25 babies with abnormalities of the screening ECG, and 25 babies without such abnormalities, failed to show any additional tachyarrhythmias or bradyarrhythmias warranting treatment. In view of the uncertain clinical significance of many neonatal arrhythmias and cardiac conduction disorders, more information concerning their natural history and relationship to sudden unexpected death in infancy is needed before recommending that neonatal ECG screening be generally adopted.

Arrhythmias, Cardiac↗
PubMed1979

Low voltage electrical activity preceding right atrial depolarisation in man.

Electrical recordings were made in the high right atrium in 28 patients undergoing cardiac catheterisation and in 3 healthy volunteers. After filtering and amplification by 3 to 10 million times, the signals were passed through a signal averaging process in a digital computer. Of the 28 subjects who had technically satisfactory recordings, 23 showed low voltage electrical activity preceding the conventionally-recorded atrial depolarisation. The low voltage activity started 50 to 200 ms before the atrial deflection and was variable in shape. These early signals may be the result of activity in the region of the sinus node.

Arrhythmia, Sinus↗