Biomedical subjects
C W Bryan-Brown
Publications and source records attributed to C W Bryan-Brown.
Regulations and critical care.
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An open door policy in ICU.
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"The colouring substance of blood.".
Over a century ago, Stokes wrote on the oxidation and reduction of "the colouring substance of the blood." The mechanisms that govern the binding of oxygen to hemoglobin have been defined in even greater detail and higher orders of accuracy, even to the ends of the oxyhemoglobin dissociation curve. The Bohr effect has ceased to be a reduction in the affinity of hemoglobin for oxygen due to an increasing hydrogen ion concentration and according to a mere logarithmic equilibration constant. The constant has become a variable, subject to the interactions of temperature, carbon dioxide, organic phosphate, and ionic concentrations. This interdependence of so many variables has rendered the once inaccurate, but precise prediction of the effect of tht, well beyond the means of the average physician managing the treatment of a sick patient.
Extracorporeal membrane oxygenation for massive pulmonary thromboembolism.
This study was undertaken to determine whether extracorporeal membrane oxygenation (ECMO) could modify the effects of massive lethal thromboembolism and prevent death. Twenty anesthetized dogs were prepared for venoarterial perfusion with a demand pump and membrane lung and were perfused slowly for 1 1/2 hours to lessen homologous blood shock; 1 ml per kilogram of 24-hour-old tantalum-impregnated thrombus was injected intravenously. The dogs had profound systemic hypotension with an elevated mean pulmonary artery pressure (62.9 +/-4.5 mm Hg) immediately after embolization. Control animals generally died within 15 minutes. Four of the 10 ECMO-supported animals lived for six days, at which time they were restudied and killed. Not only can ECMO maintain an animal that would otherwise die quickly of massive pulmonary thromboembolism, but such support, even though temporary, can greatly improve the chances of survival.
Aspiration pneumonia in the intensive care unit.
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Blood clots labeled with powdered tantalum for experimental pulmonary emboli.
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Cardiorespiratory response to a new isoquinoline derivative in critically III patients.
NC 7197, a new N-substituted tetrahydroisoquinoline derivative, was given in doses of 0.2 mg/kg body weight on 26 occasions to a series of 23 critically ill postoperative and posttraumatic patients who had been in moderate or severe degrees of shock. This agent was observed to improve pressure-flow and oxygen-transport variables, including increases in cardiac index, mean arterial pressure, central venous pressure, both left and right ventricular stroke work, central blood volume, systemic vascular resistance, oxygen availability, arteriovenous oxygen content difference, and oxygen consumption, and decreases in mean transit time and pulmonary vascular resistance. Previous studies on critically ill patients have suggested that these are the most commonly desired therapeutic actions for this type of patient. The agent has pronounced inotropic effect with minimal chronotropic effects, but with higher doses, chronotropic effects as well as alpha blocking effects may occur. The optimal effects may be obtained by adjusting the dose to an appropriate therapeutic range. It is concluded that, in the dose used, this agent produced both alpha and beta adrenergic actions in critically ill patients.
Massive swelling of the head and neck.
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Nutritional aspects of body water dislocations in postoperative and depleted patients.
Measurements of plasma volume with 125I human serum albumin, extracellular water (ECW) with 82Br-minus, and total body water (TBW) with 3-H2O were made on 16 postoperative patients, 15 depleted patients, and three control subjects. Intracellular water (ICW) was calculated as the difference between TBW and ECW. The observed findings for the series as a whole showed no change in blood volume, an increase of 3.7 I in ECW, and a decrease of 1.5 I in ICW as compared to predicted values based on current weight. Compared to predicted values based on normal (pre-illness) weight, the observed body weight decreased 16% and ICW decreased 22%; this suggests that body weight consistently under-estimates the extent of nutritional depletion. Severe depletion seen in postoperative patients indicates that frequently earlier use of total parenteral nutrition would be beneficial. ICW was found to be the most reliable single index of moderate or severe nutritional depletion; errors in estimating normal values interfere with its use in mild depletion. The ratio of ECW:TBW best reflects distortion of body water composition; it is largely independent of weight, and is a more sensitive index than absolute values of ICW. Repeat measurements of body composition were made on 9 patients given total parenteral nutrition for an average period of 18 days. On the average, there was an ECW decrease of 1.8 I, a body weight increase of 2 kg, and an ICW increase of 3.2 I after parenteral nutrition. The increased ICW represents the repletion of half of the average initial deficit of 6.1 The initial ratio of ECW:TBW of 0.58 was reduced to 0.50, returning it about three-quarters of the way to the expected normal value of 0.48. Intravenous administration of 5% glucose as sole source of calories may be a factor in distortion of body water compartments.
Plasma expansion in surgical patients with high central venous pressure (CVP); the relationship of blood volume to hematocrit, CVP, pulmonary wedge pressure, and cardiorespiratory changes.
There was no correlation of blood volume measurements with central venous pressure (CVP) or hematocrit determinations and only minimal suggestive trends with wedge pressure in a large series of postoperative patients; the lack of correlations emphasize the unreliability of venous pressure and hematocrit determinations to predict blood volume alterations. To evaluate the physiological problems, to define optimal therapeutic goals, and to measure therapeutic effectiveness of volume loading with an oncotically active agent, we measured the hemodynamic and oxygen transport responses to 500 ml. of 5 percent albumin given over 1 hour in 22 patients with CVP greater than 15 cm. H2O. The patients were separated into two groups according to the CVP response to volume therapy. The CVP decreased in 14 (64 percent) of these patients (Group 1), but it increased slightly but not significantly in eight (36 percent) patients (Group 2). In Group 1 patients, there was increased flow, improvement of tissue perfusion as reflected by increased oxygen consumption, and augmentation of the ventricular function. In Group 2 there were slight increases in mean flow, mean pulmonary arterial pressure, and mean transit time and slightly decreased pulmonary vascular resistance; there was appreciable improvement in left ventricular function without significant deterioration of right ventricular function. The high initial central venous pressure is not a reliable index of either hypervolemia or cardiac failure in critically ill patients. It is concluded that a trial of volume loading with an oncotically active agent with frequent auscultation of the chest and careful observation of the CVP trends will give the maximum diagnostic as well as therapeutic information.
The influence of parenteral nutrition on the course of acute renal failure.
The influence of hypertonic glucose with and without added amino acids was studied in 129 consecutive postoperative patients with acute renal failure. The addition of amino acids was associated with lower mortality and morbidity rates in the patients who received dialysis as well as in those who did not. There was no significant differences in the blood urea nitrogen levels of the two groups. The incidence of hyperkalemia and the rise in plasma osmolality were less in the group given adequate calories and amino acids.
Tissue blood flow and oxygen transport in critically ill patients.
The theoretical and practical solutions to the problems of increasing oxygen transport are well understood. Unfortunately the quantitation of hypoxia, both as an absolute deficit and as a precise method of prognosis is not yet available. This may well be because regional hypoxia in a vital tissue cannot be mirrored in a total body measurement. In the low-flow state, oxygen delivery can be maintained by redistribution of cardiac output, reduction of oxygen uptake by ischemic tissue by reducing work load, by increasing oxygenation of the blood, or by decreasing the affinity of oxygen for hemoglobin. The latter provides for more oxygen to be delivered by a given amount of oxyhemoglobin before the tension falls to deleterious regions (about 20 torr). There is some evidence that pharmacologic doses of methylprednisolone may be beneficial in this respect.
Aggressive approach to intravenous feeding of the critically ill patient.
Intravenous nutrition has become a necessary part of comprehensive critical care. The guidelines that surround the technique render it both safe and effective, but are not always practical in the patient with sepsis or multisystem failure who has a shortage of sites for catheter insertion. After an 8 year experience in a multidisciplinary ICU in which 40 per cent of patients admitted are fed parenterally, modified techniques have been developed so a more aggressive and liberal approach can be used for treating acutely ill patients. Additional crystalloid fluids and medications can be administered through the TPN catheter, high calorie levels can be used initially, and TPN can be stopped abruptly and insulin dosages as high as 28 U. per hour administered safely. When critically ill patients undergo major surgery TPN may be continued. This is made possible by a well oriented and well trained staff, competent to both follow and act on the results of very close monitoring in a special care area with efficient stat laboratory backing. Complication rates have to be kept low by rigorous supervision of both catheter insertion and aftercare. This has made frequent catheter changes a practical safety measure. Management and monitoring protocols are presented. The well established protocols for the management of TPN are adhered to for the routine support of nutrition.
A less invasive approach to monitoring acute respiratory failure.
In a general ICU with a predominant surgical census, patients with acute respiratory failure can usually be treated on a clinical assessment and a minimum of invasive monitoring. An algorithm was used to manage the ventilatory support and weaning. When it failed (15% of the time), the patients' functional diagnoses were questioned and more advanced monitoring was used. The algorithm led to expeditious weaning of patients who did not need mechanical support and to a reduction of invasive monitoring.
The clinically valuable variable.
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Postoperative nutritional failure and chronic cerebral edema in neurosurgical patients.
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