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Biomedical subjects

D A Watson

Publications and source records attributed to D A Watson.

At least 73 records · Page 4Linked to original sources
PubMed1980

Physical training after heart valve replacement.

A controlled trial was undertaken to examine the efficacy of physical training in patients recovering from the replacement of a single heart valve. Patients were allocated to a test or control group two weeks after operation. Each patient performed a submaximal exercise test at entry, and 12 and 24 weeks after this test. The Canadian Air Force exercise programme was undertaken by the test group, while the control group continued normal activities for the 24 weeks between the first and last exercise group. A regression line of submaximal heart rate on oxygen consumption was calculated from the data of each exercise test in each patient. Alterations in this line were used as an "index" of changes in "cardiorespiratory fitness". The individual results showed a consistent improvement in "cardiorespiratory fitness" over the first 12 weeks in both groups. Only patients in the test group continued to improve between 12 and 24 weeks. Thus the exercise programme modified the recovery of "cardiorespiratory fitness" after operation. Results in patients who developed clinical complications, and were excluded from the trial, predicted a deteriorating clinical condition. This finding suggested that sequential exercise tests are of value after cardiac surgery.

Adolescent↗
PubMed1980

Chronic haemolysis after Lillehei-Kaster valve replacement. Comparison with the findings after Björk-shiley and Starr-Edwards mitral valve replacement.

Nineteen female and sixteen male patients who have had their heart valves replaced with Lillehei-Kaster valves were investigated for haemolysis four to 18 months after operation. Investigation included serum lactic dehydrogenase, serum haptoglobins, and urine haemosiderin. Red cells survival, using autologous red cells labelled with 51Cr, was measured in 12 patients. No patient showed manifest anaemia. The serum lactic dehydrogenase levels were raised in 66% of the mitral valve patients, 81% of the aortic valve patients, and in all the double valve patients. The serum haptoglobins were decreased in 66% of mitral patients, 68% of aortic valve patients, and in 75% of the double valve patients. All the 12 patients studied had lower than normal red cell survivals. No correlation was found between the incidence of haemolysis and the size of the valve. In isolated mitral valve replacement 66% showed compensated haemolysis compared with 42% in Björk-Shiley valves (p less than 0.05), 85% in Starr-Edwards valves (composite seat) (p less than 0.01), and none in frame-mounted irradiated homografts (previous study) (p less than 0.001).

Female↗
PubMed1979

I. Development of an in vitro model of myocardial cooling: a study of the effect of cardiac size on cooling rate.

A physical model for the study of local cardiac hypothermia was developed using excised animal hearts. The validity of the model was established by showing close similarity between cooling curves of dog hearts in vivo and in the model. The model was then used to compare the cooling rates of three groups of excised hearts using cold saline irrigation. Groups 1, 2, and 3 had mean left ventricular weights of 166, 379, and 1,429 gm, respectively, and mean left ventricular wall thicknesses of 1.5, 2.0, and 3.1 cm, respectively. For the same 10 degrees C temperature fall, Group 1 took 25 +/- 2.8 minutes, Group 2 took 54 +/- 9.2 minutes, and Group 3 took 117 +/- 21 minutes. To avoid slow cooling and consequent ischemic damage in the hypertrophic ventricle, it may be desirable to initiate cooling using coronary perfusion with cold blood or cold cardioplegic solutions.

Animals↗
PubMed1979

II. Interference with local myocardial cooling by heat gain during aortic cross-clamping.

We have used a physical model of the thermal conditions of open-heart surgery to study sources of heat input to the heart during local cardiac cooling. Pulmonary and systemic venous return entering the cardiac chambers were the most important sources of heat to the hypothermic heart. In 5 excised hearts, venous return of 100 ml per minute or more entering the left atrium and left ventricle increased mean septal temperature significantly from 8 +/- 1 degrees C to 16 +/- 1 degree C (p less than 0.01). When venous return passed through the right side of the heart and then the left side, it increased mean septal temperature significantly from 7 +/- 0.5 degrees C to 23 +/- 1 degree C (p less than 0.001). Conduction of heat through the pericardium, heat radiation from standard operating room lights, and heat uptake from room air had relatively minor effect and produced no significant increase in myocardial temperature provided all surfaces of the ventricles were irrigated with cold saline. The hypothermic heart can be isolated from heat input by individual caval cannulation, low bypass perfusion rate, systemic cooling to 30 degrees C, and irrigating all surfaces of the ventricles with cold saline.

Animals↗
PubMed1979

III. Local cardiac hypothermia: experimental comparison of Shumway's technique and perfusion cooling.

A model of the thermal conditions of the heart during ischemic arrest was used to study the efficiency of Shumway's technique of topical hypothermia. Cooling was improved by increasing the flow of cold saline to 350 ml per minute, reducing the saline temperature, lifting the posterior left ventricular wall away from the pericardium, and irrigating the left ventricular cavity. Perfusing the coronary circulation with cold fluid cooled the heart eight times faster than did surface irrigations by Shumway's technique.

Animals↗
PubMed1979

The interaction of varying doses of dipyridamole and acetyl salicylic acid on the inhibition of platelet functions and their effect on bleeding time.

1 In normal volunteers maximum reductions in platelet functions, collagen aggregation, adhesion and PF4 availability, were achieved using combined doses of 50 mg three times daily dipyridamole + 180 mg ASA or 75 mg three times daily dipyridamole + 120 mg ASA daily. 2 These doses did not prolong the bleeding time. 3 A synergistic effect has been demonstrated with 25 mg dipyridamole three times daily and 60 mg ASA. 4 At higher doses the effects on platelet functions were additive up to the maximal response. 5 The effect of low doses of ASA on platelet function was cumulative. 6 As lower doses of ASA in the combination studied inhibit platelet functions maximally without altering the bleeding time and probably without inhibiting prostacyclin, we suggest that these combinations of dipyridamole and ASA merit consideration in future clinical trials.

Adult↗
PubMed1979

Levamisole and surgery in bronchial carcinoma patients: increase in deaths from cardiorespiratory failure.

Life table analysis of early entry to this randomised blind trial of 318 patients has shown a significantly poorer survival for resected lung cancer patients treated with levamisole for three days before operation and three days a fortnight thereafter than for placebo-treated controls. This excess was largely due to deaths that had been attributed to operation or other causes (non-cancer deaths), most occurring in the six weeks after operation. In the 99 resected patients treated with levamisole there was a 15% excess of deaths in this category, compared with the placebo-treated controls. Extensive analysis excluded maldistribution of patients between the groups as a cause of this difference. Many more died in respiratory distress, mostly without clear cause, in the levamisole group. Antibody (lgG) reacting with myocardial sarcolemma or sarcoplasm was found in the only serum samples available for testing which were drawn from patients during the syndrome. The findings are in keeping with a primary effect on the heart, possibly involving an autoimmune mechanism. The effect has not been noted in other trials.

Adenocarcinoma↗
PubMed1979

Heparin administration during extracorporeal circulation: heparin rebound and postoperative bleeding.

The individual variations in heparin dose response and heparin activity decay have indicated limitations of the protocols based on body surface area and weight of the patients. In the present study the heparin levels and simpler clotting tests were monitored in a consecutive series of 71 patients undergoing standard cardiac operations. The clotting tests used were the Celite activated clotting time (Celite ACT) and the whole blood activated recalcification time (BART). Forty-four patients received a loading dose of heparin, 3 mg. per kilogram, a maintenance dose of heparin, 1.5 mg. per kilogram per hour, and 6 mg. of protamine sulfate per kilogram at the termination of extracorporeal circulation (ECC) (Protocol I). Twenty-seven patients received a similar initial dose, but the maintenance dose of heparin and the dosage of protamine sulfate were administered according to the measured heparin levels (Protocol II). A significant difference was seen in the measured heparin levels (p less than 0.01, Celite ACT (p less than 0.01), and BART (p less than 0.01) in patients on Protocols I and II. Ten of the 24 patients on Protocol I and none on Protocol II showed heparin rebound phenomenon, and blood loss in patients on Protocol I was significantly greater than that in patients on Protocol II. The study clearly demonstrates that our protocol of heparin administration and control with simpler tests ensures safe hypocoagulation during ECC and efficient reversal at the end, with minimal postoperative blood loss.

Adolescent↗
PubMed1978

Height and weight gain after total correction of Fallot's tetralogy.

In a consecutive series of 100 cases of Fallot's tetralogy undergoing total correction, the mean birthweight was found to be just below the 50th centile. Blalock-Taussig or Waterston shunts were performed in 45 patients. Before their shunt operations a significant number of patients had become retarded in height and weight development but after the shunt operations many patients showed accelerated height and weight gain. Of the 73 patients followed up 2 years after correction, 23 had experienced accelerated development in both weight and height, but 11 patients remained on or below the 3rd centile for weight and height. In terms of the age at shunting, the oxygen saturation immediately before total correction, the age at total correction, the number of ventriculotomy patch repairs, and the post-correction ventricular pressure ratios, no significant difference could be detected between those 23 patients who had undergone accelerated development and those 11 who had remained retarded. More shunts, particularly of the Waterston type, were performed in the retarded group.

Adolescent↗
PubMed1977

The effect of dipyridamole on platelet function: correlation with blood levels in man.

1 The effect on platelet functions of dipyridamole (a pyrimido-pyrimidine compound) was compared with a control group of patients taking warfarin. 2 Adhesion, aggregation and platelet factor 4 availability showed a significant decrease in the dypyridamole group. 3 Aggregation and platelet factor 4 showed a significant correlation with blood dipyridamole level. 4 Adhesion, aggregation and platelet factor 4 were reduced below the lower limit of normal at blood dipyridamole levels above 3.5 micronmol/1.

Blood Platelets↗
PubMed1976

Chronic hemolysis following mitral valve replacement. A comparative study of the Björk-Shiley, composite-seat Starr-Edwards, and frame-mounted aortic homograft valves.

Hemolysis was assessed in 86 patients after mitral valve replacement. Twenty-four patients had mitral valve replacement with a Björk-Shiley valve, 32 patients with a Starr-Edwards composite-seat valve, and 30 patients with an irradiated frame-mounted aortic homograft valve. Hemolysis was determined by red cell survival and autologous 51Cr-tagged red cells, LDH, serum haptoglobin, hemosiderinuria, reticulocyte count, red cell fragment count, and hemoglobin estimation. The degree of hemolysis was classified as mild, moderate, or severe. Thirty-five per cent (nine of 24) of the Björk-Shiley group showed mild hemolysis, whereas 85 per cent (28 of 32) of the Starr-Edwards group had evidence of hemolysis-of these, a third were mild and the rest moderate. The homograft series did not show any comparable evidence of hemolysis. Statistical analysis of the parameters of the study comparing homograft with Björk-Shiley valves showed no significant difference except in red cell survival, which showed a highly significant difference (p less than 0.001). Comparing homograft with Starr-Edwards valves, all parameters showed highly significant differences (p less than 0.001).

Anemia, Hemolytic↗
PubMed1975

Light and electron microscopy studies on homograft and heterograft heart valves.

Light and electron microscopical changes were studied in 23 valvular homografts and six pig aortic heterografts, which had been inserted into patients for lengths of time varying from three days to 54 months. Prior to insertion, eleven of the homografts had been sterilised by beta-propriolactone and freeze-dried, the other twelve had been sterilised by gamma-radiation. The morphological changes in the freeze-dried group were characterised by moderate to severe structural changes including gross vacuolation, fibrinoid degeneration and calcification in the absence of any significant cellular events. It is concluded that the structural changes were due to physico-chemical degradation of the collagen due to improper preservation of the graft, prior to insertion. The morphological changes in the homografts treated with gamma-radiation were fewer and less severe in that there was less vacuolation of the matrix, less fibrinoid degeneration and no examples of calcification. Clear-cut examples of graft regeneration were never observed in either group, but the significance of minor cellular infiltrates in two of the gamma-irradiated grafts is discussed in terms of abortive regeneration. The heterografts showed moderate to intense cellularity, predominantly of macrophages. It is postulated that graft rejection phenomena are responsible for the graft failure in this group.

Animals↗
PubMed1975

Growth hormone and blood-glucose concentrations during cardiopulmonary bypass.

Plasma growth hormone (plasma GH) and blood-glucose concentrations were measured in 23 patients undergoing open heart surgery with moderate hypothermia. A significant increase in blood-glucose concentration occurred with sternotomy and increased during bypass, partly as a result of the exogenous glucose load from the perfusate. Following bypass, the blood-glucose remained above the pre-anaesthetic concentration, and this elevation persisted into the period following surgery. Plasma GH also increased with surgery and remained elevated during perfusion. The highest concentrations occurred following bypass when normal temperature had been regained .

Adult↗