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Biomedical subjects

D B Morgan

Publications and source records attributed to D B Morgan.

At least 19 recordsLinked to original sources
PubMed1990

Effect of continuous intra-aortic balloon inflation in canine open chest cardiopulmonary resuscitation.

In a canine model of open chest CPR, the effect of continuous intra-aortic balloon (IAB) inflation on cerebral and myocardial perfusion was investigated utilizing hemodynamic and radioactive microsphere techniques of assessing regional blood flow. Compared to deflation, IAB inflation augmented the following variables, expressed as percentage of prearrest control: aortic systolic (50% to 71%) and aortic diastolic (40% to 58%) pressures during 30-sec inflations; and epicardial blood flow (BF) (44% to 57%), mesocardial BF (40% to 56%), endocardial BF (36% to 50%), carotid BF (32% to 51%), and cerebral BF (67% to 88%) during inflations of greater than 150 sec. IAB inflation had no effect on right atrial pressure; thus, estimated cerebral and myocardial perfusion gradients were augmented. IAB inflation may prove to be a beneficial adjunct to open chest CPR.

Animals↗
PubMed1990

Vasopressin and plasma volume response to submaximal and maximal exercise in man.

Plasma arginine vasopressin (PAVP), plasma volume loss (PVL) and blood lactic acid (LA) responses to submaximal exercise were examined in 16 normal, healthy individuals. Subjects volunteered to participate in three experiments conducted at the same time of day (9 am) with 7 days intervening between tests. Venous blood was removed before and immediately after 15 min exercise at 40% and 70% VO2max, and before and after 100% VO2max which lasted for 14.3 +/- 1.4 mins (mean +/- SD). The resting mean values of PAVP were similar on the three testing occasions (p greater than 0.05). PAVP rose significantly (p less than 0.05) to all exercise treatments and exhibited an exercise-intensity related response. Similarly, PVL (calculated from changes in haematocrit) and LA responses to exercise were increased with increasing workload. No direct relationship was found between PAVP changes and PVL or LA responses to submaximal exercise (p greater than 0.05). These results suggest that (a) PAVP levels increase to exercise with a response related to exercise intensity; (b) the stimuli generated directly or indirectly to exercise may be one of many factors causing an increase in PAVP.

Adult↗
PubMed1979

Potassium depletion and tissue loss in chronic heart-disease.

Weight-loss, total body-potassium, and total body-nitrogen were measured in 12 men and 15 women with severe chronic heart-disease. Compared with age-matched healthy controls, the men had lost an average of 13 kg in weight, 915 mmol of potassium, and 354 g of nitrogen, whereas the women had lost 5.6 kg of weight, 327 mmol of potassium, and 66 g of nitrogen. Although the potassium/nitrogen ratio in the lost tissue is not precisely known, the loss of nitrogen indicates that most of the potassium loss in men is due to tissue loss and that there is little fall in the intracellular concentration of potassium in either the men or the women.

Body Weight↗
PubMed1979

Renal function after long-term treatment with lithium.

Daily urine volumes, plasma creatinine concentrations, and creatinine clearance were measured in 106 patients with unipolar and bipolar affective disorders attending a "lithium" clinic. Urine volumes exceeded 3.51 in only six patients, plasma creatinine concentrations exceeded 150 mumol/1 (1.7 mg/100 ml) in only five, and creatinine clearance was below 50 ml/min in 16. Renal function was assessed by measuring creatinine clearance and renal tubular function, including response to 20 hours of water deprivation, in a representative sample of 30 patients from the lithium clinic and 30 psychiatric patients matched for age and sex who were taking other psychotropic drugs. Creatinine clearance and tubular function, including urine osmolality after water deprivation, were not significantly different between the two groups. Urinary excretion of arginine vasopressin (AVP), however, was much greater in the lithium-treated patients, who therefore had a diminished tubular responsiveness to AVP. The findings do not support suggestions that long-term lithium treatment results in seriously impaired renal function, renal damage, and polyuria. Compared with other series, however, the patients were being maintained with low serum lithium concentrations, which apparently area as effective prophylactically as higher concentrations.

Adult↗
PubMed1979

Clinical effects of vitamin C in elderly inpatients with low blood-vitamin-C levels.

The effect of oral vitamin C has been examined in elderly long-stay inpatients known to have low levels of vitamin C in their plasma and leucocytes. 1 g of vitamin C given daily for 28 days was shown to be associated with slight, but significant, clinical improvement and weight-gain when compared with placebo therapy.

Activities of Daily Living↗
PubMed1979

Interpretation of serum total calcium: effects of adjustment for albumin concentration on frequency of abnormal values and on detection of change in the individual.

Serum total calcium was measured in 1693 patients during a four-month period. We examined the effects of adjustment for albumin concentration on the interpretation of single measurements of serum total calcium and on the variation of series of measurements in individual patients. Markedly abnormal total calcium concentrations--2.75 mmol/l (11.0 mg/100 ml) or more, or 2.00 mmol/l (8.0 mg/100 ml) or less--were found in 115 patients, but only 24 (21%) remained markedly abnormal after adjustment for albumin. Three patients, two with malignant disease and one with primary hyperparathyroidism, had significant hypercalcaemia which was masked by hypoalbuminaemia. The serum total calcium measured on a subsequent occasion had changed 0.15 mmol/l (0.6 mg/100 ml) or more in 60 patients, but after adjustment for albumin this number was reduced to 27 (45%). The within-person standard deviation for serum total calcium was calculated in 26 patients with normal mean adjusted calcium concentrations who had had six or more sequential measurements. The mean standard deviation was 0.148 mmol/1 (0.59 mg/100 ml) and, after adjustment for albumin, this was reduced to 0.100 mmol/1 (0.40 mg/100 ml). We conclude that adjustment of serum total calcium concentration for albumin is essential to detect abnormal values and to assess changes in a value.

Blood Protein Disorders↗
PubMed1979

The cause of the raised plasma urea of acute heart failure.

The concentrations of urea, urate, phosphate and creatinine were measured in the plasma of 30 consecutive patients admitted acutely with heart failure. On admission, 20 had a raised plasma urea, 21 had a raised plasma urate, but only 6 had a raised plasma phosphate and only 6 had a raised plasma creatinine. A further 9 of the patients developed a raised plasma urea after admission. The increase in plasma urea present on admission was greater than expected for the fall in GFR (as indicated by the increase in plasma creatinine). The results for plasma and urine taken together suggest that a major cause of the raised plasma urea was an increased urea production rather than a reduced glomerular filtration rate. There was no obvious relationship between plasma urea and clinical features, or diuretic therapy.

Acute Disease↗
PubMed1979

The nitrogen to creatinine ratio in untimed samples of urine as an index of protein catabolism after surgery.

The loss of nitrogen after surgery is said to be related to body size as well as to the magnitude of the metabolic effects of surgery. Urine nitrogen should be 'corrected' for body size before it can be taken as a guide to the severity of surgery in the individual. Twenty-three patients were studied after elective abdominal surgery of moderate severity, when they were having only 3 litres of dextrose saline daily. The 24-hr urine nitrogen excretion (mean of days 3 and 4) was correlated with 3 indices of body size, body weight (r = 0.614), fat-free mass (r = 0.743) and 24-hr creatinine excretion (r = 0.780). Nitrogen excretion was corrected for body size by calculating the ratio of nitrogen to each index. For each index the s.d. of this corrected nitrogen excretion at the mean value of the index was less than the s.d. of the uncorrected data. The nitrogen : creatinine ratio in an untimed urine sample was closely related to the ration in the 24-hr urine (r = 0.914). These results demonstrate that nitrogen excretion after surgery is related to body size and can be corrected for body size by calculating the nitrogen : creatinine ratio in an untimed urine.

Body Weight↗
PubMed1979

Hypertension and hyperkalaemia responding to bendrofluazide.

A 33-year-old man is described with hyperkalaemia, hypertension and acidosis. The blood pressure was 160 to 200 mmHg systolic and 90 to 110 mmHg diastolic and the plasma potassium was between 6.0 and 7.0 mmole per litre. There was no renal disease and creatinine clearance was 103 ml per minute. Plasma renin activity was low and plasma aldosterone was at the lower limit of normal. Sodium deprivation or oral frusemide had little effect on blood pressure, plasma potassium, renin, aldosterone or arginine vasopressin. However, bendrofluazide caused a rapid fall of blood pressure and plasma potassium, and rise of plasma renin, aldosterone and plasma arginine vasopressin. Hypertension and hyperkalaemia is rare in the absence of renal failure. Four similar patients reported previously are reviewed. We suggest that our patient, and perhaps some of those reported earlier had primary abnormality of renal tubular function with impaired secretion of potassium and excessive tubular reabsorption of sodium. The plasma renin activity could be due to volume expansion and the low plasma aldosterone was probably caused by the antagonistic effects of low renin depressing synthesis and hyperkalaemia increasing it. A minor similar tubular abnormality might be the explanation in some of the patients with essential hypertension who have low plasma renin activity.

Adult↗
PubMed1978

Severe hyponatraemia. A study of 17 patients.

17 patients with severe hyponatraemia (none had cardiac failure or had lately had an operation) all had excessively high plasma-antidiuretic hormone (A.D.H.). Only 13 had features typical of the syndrome of inappropriate secretion of A.D.H. (S.I.A.D.H.). Plasma-A.D.H. was not related to either plasma-sodium or diagnosis. There were as many patients with chest infection as with carcinoma of the lung. Plasma-sodium and plasma-A.D.H. returned rapidly towards normal in the patients with chest infection or volume depletion but these concentrations corrected much more slowly in patients with carcinoma of the lung. The increase in plasma-sodium in patients with chest infection was too rapid to be produced by water-deprivation treatment and was due to return of plasma-A.D.H. to normal. The term S.I.A.D.H. implies an understanding of pathophysiology that does not exist. As a diagnosis it does not help in management or prognosis. A simpler, more descriptive terminology such as "hyponatraemia with carcinoma of the lung" would be more useful and less confusing in the clinical situation.

Aged↗
PubMed1978

Muscle chemistry of critically ill surgical patients and the effects of a course of intravenous nutrition.

The water, electrolyte and nitrogen contents of muscle were measured in 15 critically ill surgical patients before and after a course (approximately 2 weeks) of intravenous nutrition and in 8 normal individuals. The muscle from the surgical patients contained a significantly increased ratio of water to fat-free dry weight (P less than 0.01) due to an increase in the proportion of extracellular to intracellular water, and this was not corrected by intravenous nutrition. These changes could be due to an accumulation of extracellular fluid alone or to a loss of cell cytoplasm or a loss of whole muscle fibres. Intracellular chemistry was normal in the ill surgical patients and was not changed by intravenous nutrition.

Adult↗
PubMed1978

Blood lactate and pyruvate levels in diabetic patients treated with biguanides with and without sulphonylureas.

Blood lactate and pyruvate were measured two to three hours after breakfast in 153 patients with maturity-onset (type 2) diabetes. Blood lactate was raised in 56% of all patients taking phenformin and in 35% of all patients taking metformin, while 75% and 35% respectively had raised pyruvate. Mean blood lactate level was raised at 2.2 mmol/1 (range 0.2-4.4 mmol/1) in the patients on phenformin and 1.7 mmol/1 (range 0.2-4.3 mmol/1) in those on metformin, with mean blood pyruvate levels of 0.122 mmol/1 (range 0.050-0.215 mmol/1) and 0.111 mmol/1 (range 0.038-0.259 mmol/1) respectively. In patients treated with a sulphonylurea drug alone mean blood lactate and pyruvate levels were not increased and were no different in those receiving sulphonylurea therapy in addition to a biguanide from those receiving a biguanide alone. Blood lactate did not correlate with any clinical or biochemical measurement in any of the treatment groups except for a correlation with serum creatinine in those patients taking metformin alone. The finding of raised blood lactate levels in diabetic patients treated with metformin suggests that this drug should be prescribed with caution.

Adolescent↗