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Biomedical subjects

I M Mitchell

Publications and source records attributed to I M Mitchell.

At least 19 recordsLinked to original sources
PubMed2001

Atrial transplantation for recurrent cardiac sarcoma.

Cardiac transplantation for sarcomas has met with little success and the surgical treatment remains controversial. We describe the case of a 56-year-old woman who was referred for transplantation after two procedures in which undifferentiated atrial sarcoma was locally excised successfully. The patient underwent atrial homograft transplantation, the first reported to date. Advantages of the procedure include wide atrial resection and no need for immune suppression.

Female↗
PubMed2000

Pericardial mesothelioma: the diagnostic dilemma of misleading images.

A young man with a short history of increasing dyspnea, cough, and ascites was initially diagnosed as having idiopathic constrictive pericarditis and referred for an operation. The procedure revealed an atypical invasive encapsulating disease. Complete resection was impossible, and only partial relief of constriction was achieved. The patient died shortly after. Histology revealed primary mesothelioma of the pericardium. The case illustrates the difficulty in establishing this diagnosis by echocardiography and computed tomography.

Adult↗
PubMed1996

The acute phase response to cardiopulmonary bypass in children.

The endocrine phase of the stress response to cardiopulmonary bypass in children is known to be subtly different from that seen in adults. The aim of this investigation was to determine whether there are similar differences in the acute phase response. Thirteen children were studied (mean age 2.65 years). Each child had congenital heart disease and underwent corrective cardiac surgery. Blood samples taken two days prior to operation and at 6, 9, 12, 24, 48 and 120 hours after were analysed for C-reactive protein, albumin, caeruloplasmin, zinc and copper concentrations. Metal:carrier protein molar ratios were also calculated. Results demonstrate changes which, although similar to those seen in adults, differed both quantitatively and qualitatively. This is explained by the concept of immaturity leading to a generally poor capacity for protein synthesis and a relative inability to respond to altered circumstances.

Acute-Phase Reaction↗
PubMed1995

Effects of dopamine on liver blood flow in children with congenital heart disease.

BACKGROUND: A reduction in liver function is common after cardiac operations, particularly in children with preexisting cardiac failure. The etiology is multifactorial, but the redistribution of organ blood flow that occurs during cardiopulmonary bypass implicates ischemia as one of the principal causes of injury. Dopamine hydrochloride is known to have specific effects on the renal circulation, and the aim of this study was to investigate its effects on hepatic perfusion. METHODS: Eight children with congenital heart disease were studied 6 hours after the end of cardiopulmonary bypass when they were fully rewarmed and hemodynamically stable. Using noninvasive auricular densitometry, we determined the percent disappearance rate of indocyanine green as an index of liver blood flow both before and 1 hour after commencing an infusion of dopamine at 4 micrograms.kg-1.min-1. RESULTS: Results showed an increase of approximately 31% in the percent disappearance rate of indocyanine green with the addition of low-dose dopamine (4 micrograms.kg-1.min-1) (p < 0.01). CONCLUSIONS: Dopamine may have a therapeutic role in increasing hepatic perfusion and minimizing any loss in liver function.

Cardiopulmonary Bypass↗
PubMed1995

Total body water in children with congenital heart disease, before and after cardiac surgery.

The aim of this study was to measure total body water in children with congenital heart disease before and after cardiac surgery and to compare the results of deuterium and 18oxygen dilution methods. Seventeen children (aged 4 to 33 months) were given aliquots of isotopically labeled water 1 week before and 6 hours after cardiac surgery. Isotope equilibration and analysis of the declining enrichment of daily urine samples allowed calculation of the total body water content. Before operation, total body water was significantly elevated (p < 0.001, Wilcoxon test); after operation it fell to approximately normal values. This finding is in contrast to those of previous reports, but may be explained in that the method used for calculation depended on measurements taken over a 7-day period rather than on a single measurement of isotope dilution as used elsewhere. Nevertheless, these results do suggest that surgery can correct the preoperative fluid overload. Comparison of deuterium and 18oxygen dilution methods showed a 2% to 2.5% overestimation of the total body water content with deuterium sampling.

Body Water↗
PubMed1995

Nutritional status of children with congenital heart disease.

OBJECTIVE: To assess the nutritional status of children with congenital heart disease. DESIGN: Six anthropometric, 24 biochemical, and five haematological markers of nutritional wellbeing were measured in children with congenital heart disease. SETTING: The west of Scotland. PATIENTS: 48 children admitted consecutively for surgical correction of congenital heart disease. MAIN OUTCOME MEASURES: Height, weight, and triceps and subscapular skin fold thicknesses were considered abnormal if they were below the third centile compared with standard reference data for age matched British children. Mid-arm circumference and arm muscle circumference were considered abnormal if they fell below the fifth centile compared with standard data. Biochemical and haematological data were compared with age matched and locally validated laboratory normals. RESULTS: A marked degree of undernutrition was evident in all children; 52% had weight less than the third centile, 37% were below the third centile for height, and 12.5% were below the third centile for triceps skin fold thickness and 18.8% for subscapular skin fold thickness. Mid-arm circumference and arm muscle circumference were below the fifth centile in 20.1% and 16.7% of children respectively. Five or more of the 29 biochemical and haematological measurements were abnormal in 83.3% of patients; 10 or more were abnormal in 12.5% of patients. CONCLUSIONS: Children with congenital heart disease are frequently undernourished, irrespective of the nature of cardiac defect and the presence or absence of cyanosis.

Arm↗
PubMed1995

The validation of auricular densitometry for indocyanine green clearance measurement of hepatic blood flow during and after cardiopulmonary bypass in children.

The clinical measurement of hepatic perfusion is complicated by a dual blood supply and the invasive nature of the majority of techniques available. The aim of this study was to validate indocyanine green clearance and noninvasive auricular densitometry as a measure of hepatic perfusion in the context of paediatric cardiac surgery. The effects of different dye concentrations on densitometer recording were assessed in vitro and found to have a linear relationship. Similarly, variations in haematocrit, within the range 21-47%, also had little effect on accuracy. Comparison of densitometry and direct blood sampling with plasma spectrophotometry in six postoperative, normothermic children showed no significant difference between the noninvasive and invasive techniques (r = 0.968; p > 0.05, t-test). Comparison in 10 hypothermic children during cardiopulmonary bypass also showed no significant difference between the two methods, provided that no further cooling or rewarming took place (r = 0.83; p > 0.05, Wilcoxon test). Noninvasive auricular densitometry can, therefore, provide a reliable assessment of hepatic perfusion in children undergoing cardiac surgery.

Cardiopulmonary Bypass↗
PubMed1995

The effects of congenital heart disease and cardiac surgery on liver blood flow in children.

Children with congenital heart disease may have some degree of hepatic impairment, with further impairment developing shortly after surgical correction of the cardiac defect. The redistribution of organ blood flow that occurs during cardiopulmonary bypass implicates ischaemia as one of the principal causes of injury. The aim of this study was to measure liver blood flow in children with congenital heart disease and to determine both the effects of cardiopulmonary bypass and the consequences of corrective surgery. Indocyanine green clearance and auricular densitometry, were used in 31 children. In 83% we demonstrated a reduced liver blood flow, with a mean percentage disappearance rate (PDR) of 12.9% (SEM +/- 1.2). This finding was unrelated to the patient's age, the type of congenital heart defect or the presence or absence of cyanosis. During cardiopulmonary bypass, hepatic perfusion was further reduced in 77% of children, by an average of 67%, out of proportion with the iatrogenic reduction in total body flow. Six hours after surgery, liver blood flow had increased significantly above preoperative levels (p < 0.001; t-test) to approximately normal values with a mean PDR of 20.4% (SEM +/- 1.5).

Cardiopulmonary Bypass↗
PubMed1994

Energy expenditure in children with congenital heart disease, before and after cardiac surgery.

Failure to thrive is a common feature of children with congenital heart disease. Whether this is the result of poor nutrition or an abnormally high basal metabolic rate is unknown, yet the state of nutrition has a profound effect on the metabolic response to injury and strongly influences the outcome of surgical treatment. The aim of this study was therefore to measure the preoperative and postoperative energy requirements of children with congenital heart disease. Eighteen children (aged 4 to 33 months) were given two oral doses of doubly labeled water (H2(18)O and 2H2O), the first 1 week before operation and the second 6 hours after the end of cardiac surgery. By measuring the relative loss of each isotope from the body water pool, we were able to calculate the rate of carbon dioxide production and therefore total energy expenditure. In five patients, energy expenditure was clearly elevated, suggesting that a raised basal metabolic rate is an important factor in the observed failure to thrive in at least a proportion of such children. Postoperatively, energy expenditure fell to values below normal for healthy children (not having an operation), which suggests that the stress of surgery leads to smaller energy requirements than have previously been thought.

Cardiac Surgical Procedures↗
PubMed1993

Bovine internal mammary artery as a conduit for coronary revascularization: long-term results.

Graft patency after coronary artery bypass grafting depends largely on the choice of conduit. Because an increasing number of patients have insufficient or poor-quality autologous material, there is a need for a suitable synthetic graft that is readily available and easy to handle and that has good long-term patency. Early results suggest that the bovine internal mammary artery graft may meet these criteria. We have used a total of 26 such grafts in 18 patients. Postoperative angiography has been performed in 19 grafts in 14 patients, 3 to 23 months after operation; of these grafts, 3 are currently patent (15.8%, compared with 85.7% and 75.0% patency for native internal mammary artery and saphenous vein grafts in the same patients). We report the results of clotting studies and an analysis of lipid status. These patients do not, however, appear to represent any atypical group, either in terms of coagulopathy, native coronary artery size, or the type of vessel disease. Nevertheless, our poor results contrast markedly with the early enthusiasm reported from other centers.

Aged↗
PubMed1992

EEG burst suppression with propofol during cardiopulmonary bypass in children: a study of the haemodynamic, metabolic and endocrine effects.

We have studied the effects of propofol, given to maintain EEG suppression throughout cardiopulmonary bypass (CPB), in 20 children aged 1-15 yr, in a parallel group comparison. Anaesthesia was produced by fentanyl 50 micrograms kg-1, enflurane or halothane and midazolam 0.1 mg kg-1 at the start of CPB. After randomization, 50% of the children also received propofol during CPB. All children were cooled during CPB (25-28 degrees C) and pump flows (non-pulsatile) were 2.4 litre min-1 m-2, reducing to 1.2-1.6 litre min-1 m-2 during hypothermia. Large rates of infusion of propofol were required to maintain EEG suppression, particularly during rewarming. Compared with control, the propofol group showed significant increases in mixed venous oxygen saturation and significant reductions in systemic oxygen uptake and glucose and cortisol concentrations. There were no differences in triiodothyronine and lactate concentrations, mean arterial pressure during CPB and inotrope requirement after CPB, or in recovery times.

Adolescent↗
PubMed1992

The effects of cardiopulmonary bypass on thyroid function in infants weighing less than five kilograms.

Triiodothyronine is an important regulator of cellular metabolism and may have potential use as an inotropic agent. The aim of this study was to determine the effects of cardiopulmonary bypass on thyroid function in infants weighing less than 5 kg. Serial measurements of triiodothyronine, thyroxine, and thyroid-stimulating hormone were made in 10 infants and corrected for the effects of hemodilution. We demonstrated a fall in triiodothyronine and thyroxine levels, with some recovery after 3 to 6 hours. An additional decrease then occurred, reaching a trough at 48 hours (representing a fall of 78% for triiodothyronine and 57% for thyroxine) before hormone levels returned to normal at 5 to 7 days. Thyroid-stimulating hormone concentrations increased and decreased, predating and complementing exactly the changes in triiodothyronine and thyroxine. These results are quantitatively and, for thyroid-stimulating hormone, qualitatively different from those previously reported in adults. In two patients who died, however, and in one who had a particularly difficult postoperative course, no increase in triiodothyronine, thyroxine, or thyroid-stimulating hormone concentrations was found after a trough had been reached at 48 to 72 hours, which suggests abnormal function at the hypothalamopituitary level.

Body Weight↗