Biomedical subjects
Publications and source records attributed to S A Malone.
A senior registrar 'shadowed' a district general manager and a unit general manager for one week each as a management training exercise. The three principal participants describe the exercise from their different perspectives. Consequent issues and the value of such 'shadowing' as a mode of training are discussed.
The effects of 1 hour of mild and moderate reductions in coronary blood flow on myocardial high-energy phosphate levels were evaluated. Thirty anesthetized pigs were instrumented with left anterior descending arterial and venous catheters, crystals for instantaneous wall thickness, and a fluid-filled occluder. Measurement of myocardial blood flow was performed with microspheres, and a series of myocardial biopsies also was performed. In 10 pigs, overall coronary blood flow was lowered by 22%, with a fall in subendocardial-to-subepicardial flow ratio from 1.11 to 0.54 and in wall thickening from 33% to 15%. Subendocardial flow fell 48%. Coronary blood flow and thickening were constant during 1 hour of ischemia. Phosphocreatine (mumol/g wet wt) in the subendocardial third of the ischemic zone fell from 7.6 to 3.8 at 5 minutes of ischemia (p less than 0.005 versus control) and returned to normal (7.9) at 60 minutes (p = NS), despite ongoing ischemia. Subendocardial ATP (mumol/g wet wt) fell slowly from 4.3 and leveled off at 2.1 at 60 minutes of ischemia (p less than 0.001 versus control). Similar regeneration of phosphocreatine was found in seven additional pigs, with a 43% transmural reduction in coronary blood flow and a 66% reduction in subendocardial flow. No significant changes in ATP and phosphocreatine were noted in two different control groups (n = 13 pigs). The regeneration of phosphocreatine despite ongoing ischemia and low ATP levels was not related to changes in myocardial oxygen demand or consumption, or in regional function during the period of ischemia. This may reflect 1) a successful downregulation of the energy needs of the ischemic myocardium to maintain cell viability, or 2) a metabolic abnormality in the ability of the cells to produce ATP primarily or by use of phosphocreatine.
To explore the relation between myocardial and vascular injury in the generation of the no-reflow phenomenon, the pressure-flow relation during maximal vasodilation after coronary artery reperfusion was studied in the open-chest porcine model. During both endogenous and maximal vasodilation with intracoronary adenosine, pressure-flow (P/Q) plots were constructed before and after 20-minute (n = 9) or 40-minute (n = 17) circumflex artery occlusions. Decreases in circumflex vascular bed conductance were represented by downward shifts in P/Q plot regression lines. No significant change occurred in P/Q line slope or pressure at zero flow 30 minutes after release of the 20-minute occlusion, and no infarction was found. After release of the 40-minute occlusion, a small but insignificant decrease in P/Q line slope occurred during endogenous vasodilation. However, during maximal vasodilation, a significant (p less than 0.01) decrease in P/Q line slope was present during reperfusion compared with preocclusion corresponding to a decrease in vasodilatory reserve (P/Q line slope = 1.52 +/- 0.14 ml/min/mm Hg preocclusion vs. 1.03 +/- 0.13 at 15 minutes reperfusion). Pretreatment with aspirin did not prevent this decrease in vascular conductance during maximal vasodilation. Total circumflex, as well as subendocardial, midmyocardial, and subepicardial blood flows, was measured with radioactive microspheres. There was a good correlation between the extent of infarction measured by triphenyltetrazolium chloride staining and the decrease in vascular conductance during maximal vasodilation for all three myocardial layers as well as for the total circumflex vascular bed. Hence, the degree of no-reflow correlates closely with the extent of infarction during maximal vasodilation (but not during endogenous vasodilation) and is not altered by aspirin therapy.
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Pretransfusion blood samples were routinely tested for ABO group, Rh type, and the presence of unexpected red blood cell antibodies. Patients who had unexpected red blood cell antibodies received transfusions of blood that was crossmatched using an immediate spin test, a 37 degrees C incubation step, and an indirect antiglobulin test. Patients who did not have unexpected red blood cell antibodies received transfusions with blood that was crossmatched by an immediate spin crossmatch only. Because the average immediate spin crossmatch required only 3.25 minutes to be performed, crossmatches were not done for patients without unexpected antibodies until blood was actually requested to be issued for transfusion. During the first 8 1/2 months this protocol was used, 27,742 crossmatches were performed and 46,959 unnecessary crossmatches were avoided, thus reducing direct costs by at least +49,300. This protocol also allowed for optimal blood inventory control and minimized the outdating of units of blood to only 0.19%.