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Biomedical subjects

D J Ewing

Publications and source records attributed to D J Ewing.

At least 91 records · Page 5Linked to original sources
PubMed1981

Cardiac autonomic neuropathy in diabetes: comparison of measures of R-R interval variation.

Five different methods of analysing R-R interval (heart rate) variation were compared, using a computer technique, in 61 diabetics with a wide range of responses to autonomic function testing. Two methods differentiated best between the diabetics with and without autonomic damage: (1) the standard deviation of the mean R-R interval recorded for 5 min during quiet breathing with the subject either sitting or standing; (2) the difference between the maximum and minimum heart rates recorded over 1 min during deep breathing at six breaths per minute, again with the subject either sitting or standing. For routine clinical usage we conclude that recording the heart rate for 1 min on an ECG, while the subject sits and breaths deeply at six breaths per minute, and then measuring the difference between the maximum and minimum heart rate, is the most practical method currently available. For research purposes either this method or the standard deviation method during quiet breathing for 5 min, should be used.

Adult↗
PubMed1981

Reduced airway vagal tone in diabetic patients with autonomic neuropathy.

1. Forced expiratory flow rates and specific airways conductance were measured before and after the inhalation of the atropine-like drug ipratropium bromide in 11 diabetic patients with autonomic neuropathy and a control group of 11 diabetic patients without autonomic neuropathy. Respiratory muscle function was assessed by recording maximal inspiratory and expiratory mouth pressures. 2. There was no difference between the two groups of diabetic patients in airway calibre before ipratropium bromide or in maximal mouth pressures. 3. Bronchodilatation after ipratropium bromide was greater in the control group than in the autonomic neuropathy group of patients. 4. It is concluded that, despite the lack of clinical evidence of respiratory involvement, patients with diabetic autonomic neuropathy have reduced airway vagal tone.

Adolescent↗
PubMed1980

Autonomic mechanisms in the initial heart rate response to standing.

Autonomic mechanisms underlying the initial heart rate response to standing were analyzed in nine normal subjects. The normal pattern of response was altered by atropine to a small and gradual R-R interval shortening over 30 beats, with no rebound R-R interval lengthening. With additional propranolol, R-R interval shortening was even less and confined to the first 15-20 beats, whereas propranolol alone did not affect the normal response pattern, showing that this is under vagal control with increased cardiac sympathetic activity occurring only if the vagus is blocked. The response was reproducible in 23 normal subjects. Heart rate variation during quiet standing was almost completely abolished by atropine, but unaffected by propranolol, confirming that it is also under vagal control. In four normal subjects no rebound R-R interval lengthening occurred during either "fast" or "slow" tilt, whereas it was present during both "slow" and "fast" standing. The rebound R-R interval lengthening is determined by the muscular activity involved in standing up, rather than by the speed of the maneuver.

Adult↗
PubMed1980

Assessment of cardiovascular effects in diabetic autonomic neuropathy and prognostic implications.

Cardiovascular effects of diabetic autonomic neuropathy include postural hypotension, resting tachycardia, and, possibly, painless myocardial infarction. Involvement of cardiovascular reflexes in diabetes can be assessed using simple noninvasive tests: the Valsalva maneuver, beat-to-beat heart rate variation, the heart rate response to standing, postural fall in blood pressure, and the sustained handgrip test. Tests of parasympathetic function appear to be abnormal more frequently and earlier in cardiac autonomic involvement, whereas sympathetic damage usually occurs later and is associated with clinical symptoms. When test results are abnormal, in association with symptoms suggestive of autonomic neuropathy, the prognosis is grave. Some sudden deaths that occur may be due to abnormal autonomic reflexes.

Autonomic Nervous System↗
PubMed1980

Gastric emptying in diabetic autonomic neuropathy.

Gastric emptying was studied in 12 diabetic patients, six with and six without objective evidence of autonomic neuropathy and in 20 nondiabetic controls, using a double isotope scintiscanning technique which differentiated between solid and liquid emptying. Three patients with autonomic neuropathy exhibited gastric stasis, although this was detected by conventional radiology in only one. Neither the patients with stasis nor those without exhibited abnormally rapid early gastric emptying. In patients without stasis, the normal differentiation between solid and liquid emptying was impaired, suggesting an abnormality of antral peristalsis not attributable to vagal denervation. Both intravenous and oral metoclopramide produced symptomatic improvement in two patients with gastric stasis and restored their gastric emptying to normal.

Adult↗
PubMed1980

The natural history of diabetic autonomic neuropathy.

Seventy-three diabetics (62 males and 11 females) who complained of symptoms suggestive of autonomic neuropathy were followed prospectively for up to five years. Thirty patients presented with impotence alone, while the other 43 presented with one or more of the following: postural hypotension, intermittent diarrhoea, hypoglycaemic unawareness, sweating abnormalities and gastric fullness. Most subjects with impotence alone had normal autonomic function tests (responses to the Valsalva manoeuvre and sustained handgrip) whereas the majority with other symptoms had abnormal tests. Twenty-six subjects (20 males and six females) died during the follow-up period. Of the 33 with initially normal autonomic function tests, five (15 per cent) died, whereas of the 40 with initially abnormal tests, 21 (53 per cent) died. Diabetics with symptoms of autonomic neuropathy and abnormal autonomic function tests, had a calculated mortality rate after two-and-a-half years of 44 per cent and after five years of 56 per cent. Half the deaths in those with abnormal tests were from renal failure, and the remainder were either sudden and unexpected, or from other causes which may have been associated with the autonomic neuropathy. Autonomic function testing repeated during the follow-up period showed that some normal tests later became abnormal, but once tests were abnormal, they usually remained abnormal. A number of subjects with impotence alone developed other features of autonomic neuropathy and abnormal tests during the follow up period. Symptoms of autonomic neuropathy, particularly postural hypotension, gastric symptoms and hypoglycaemic unawareness, together with abnormal autonomic function tests, carry a very poor prognosis. Diarrhoea and importence, on their own, cannot be relied on as symptoms of autonomic neuropathy. Autonomic function testing using simple cardiovascular reflexes give a good guide to the prognosis of diabetic autonomic neuropathy.

Adult↗
PubMed1979

Diabetic autonomic neuropathy.

This review attempts to outline the present understanding of diabetic autonomic neuropathy. The clinical features have been increasinly recognised but knowledge of the localization and morphology of the lesions and their pathogenesis remains fragmentary. A metabolic causation as postulated in somatic nerves accords best with clinical observations. Most bodily systems, particularly the cardiovascular, gastrointestinal and urogenital, are involved with added disturbances of thermoregulatory function and pupillary reflexes. Possible effects on neuroendocrine and peptidergic secretion and respiratory control await definition. Current interest centres around the development of a new generation of tests of autonomic nerve function that are simple, non-invasive, reproducible and allow precision in diagnosis and accurate quantitation. Most are based on cardiovascular reflexes and abnormality in them is assumed to reflect autonomic damage elsewhere. Probably no single test suffices and a battery of tests reflecting both parasympathetic and sympathetic function is preferable. Little is known of the natural history. The prevalence may be greater than previously suspected and although symptoms are mild in the majority, a few develop florid features. The relation of control and duration of diabetes to the onset and progression of autonomic neuropathy is not clearly established. Once tests of autonomic function become abnormal they usually remain abnormal. Symptomatic autonomic neuropathy carries a greatly increased mortality rate possibly due to indirect mechanisms such as renal failure and direct mechanisms such as cardio-resiratory arrest. Improved treatment of some of the more disabling symptoms has been possible in recent years.

Autonomic Nervous System↗
PubMed1979

Non-invasive assessment of left ventricular response to Valsalva manoeuvre in normal and diabetic subjects using praecordial accelerocardiography.

The left ventricular response to the Valsalva manoeuvre was studied in 5 normal subjects (group 1), 6 diabetics without autonomic neuropathy (group 2), and 5 diabetics with autonomic neuropathy (group 3), using the maximum amplitude of the praecordial accelerocardiogram (DE) as a noninvasive index of left ventricular performance. During the Valsalva manoeuvre DE decreased in all 3 groups. In groups 1 and 2, DE increased significantly above the control value after release of the manoveuvre (DE overshoot) but this did not occur in group 3. It is suggested that the overshoot of DE in groups 1 and 2 reflects an increase in left ventricular contractility after release of the Valsalva manoeuvre and the absence of an overshoot in DE in the patients with autonomic neuropathy is the result of loss of cardiac adrenergic innervation. The ability to detect an abnormal cardiovascular response to the Valsalva manoeuvre using the non-invasive technique of praecordial accelerocardiography may be of practical value in the assessment of left ventricular function.

Adult↗
PubMed1979

Mononeuropathy in diabetes mellitus.

Fifty-one diabetic patients with mononeuropathies wereoneuropathy were studied to examine possible etiological factors, to determine the relationship with other diabetic complications, and to correlate with the presence and severity of background peripheral and autonomic neuropathy. The median, ulnar, and lateral popliteal nerves were most commonly affected and cranial neuropathy was relatively uncommon. When bilateral involvement of the same nerve was excluded, multiple mononeuropathies were found in only five patients. Median and ulnar mononeuropathy were gradual in onset and affected the dominant limb whereas other types of mononeuropathies were acute in onset with no predilection for either side. No consistent relationship was shown between the onset of mononeuropathy and age, sex, diabetic treatment, duration of diabetes, diabetic control, or other diabetic complications. In particular, there was no significant background peripheral and autonomic neuropathy, as assessed clinically and by objective tests, in almost one-half of the patients studied. It is concluded that diabetic mononeuropathy may occur independently of peripheral and autonomic neuropathy. It is possible, however, that a minimal degree of background damage, known to be present in all diabetic patients, may render them more susceptible than the general population to the various factors causing mononeuropathy.

Abducens Nerve↗
PubMed1978

Immediate heart-rate response to standing: simple test for autonomic neuropathy in diabetes.

The immediate heart-rate response to standing was measured in 22 normal controls and 25 patients with diabetes, 15 of whom had autonomic neuropathy. The response in the controls and patients without autonomic neuropathy was characteristic and consistent, with tachycardia maximal at around the 15th beat and relative bradycardia maximal at around the 30th beat. The diabetics with autonomic neuropathy, however, showed a flat response. In three controls the response was abolished with intravenous atropine but not with propranolol, showing that it is mediated through the vagus. A simplified test using routine ECGs and measuring the R-R interval at beats 15 and 30 with a ruler is easily performed as an outpatient procedure and may be used as a measure of autonomic function in diabetes.

Adult↗