KBSIM/FLUIDTHERAPY: a system for optimized design of fluid resuscitation in trauma.

An application of the KBSIM (Knowledge-Based SIMulation) system to the improved design of fluid resuscitation is described. The system integrates knowledge from three domains, viz. the pathophysiology of traumatized patients represented in a quantitative biodynamic model, the heuristics of fluid resuscitation of such patients as represented in 'production rules', and some 'metaknowledge' reflected in the design of a multi-window user interface. This technique of combining numerical simulation with symbolic reasoning has obvious advantages during the design process and in training, by giving the user a possibility to evaluate his measures by direct feedback from the system. This feature of the system to assist in evaluation of alternative resuscitation procedures should also be useful as a means for decision support.

Computer simulation of fluid resuscitation in trauma. First pragmatic validation in thermal injury.

A comprehensive pathophysiologic model has been designed to describe the fluid shifts and hemodynamics in connection with fluid therapy for patients who have had trauma. The model is used to simulate treatment of a patient with burn injury, and these results are compared with measured physiologic and biochemical variables. Various formulas for resuscitation of patients with thermal injuries are also simulated to illustrate the potential use of the "patient simulator" for designing fluid resuscitation programs.

Computer simulation of fluid resuscitation in trauma. I. Description of an extensive pathophysiological model and its first validation.

Computer-based 'patient simulators' are of a potential value in diagnosis, monitoring and therapy of the severely ill patient with trauma. An extensive pathophysiological model is described and documented in full detail. The model makes it possible to calculate and predict clinically important state variables on the basis of fluid input and fluid losses. Sample runs are presented for illustrations in hemorrhage, fluid and salt loading.

Potential use of computer simulation in treatment of burns with special regard to oedema formation.

The potential usefulness of computer-based 'patient-simulators' in burn care is discussed and illustrated in the special case of oedema formation in three patients with severe thermal injuries. The present model was derived from a model by Wiederhielm (1978), and modified to be applicable to thermal injuries. The model seems to describe accurately the oedema formation as well as the distribution and composition of local and general oedema. Following thermal injuries the general oedema is characterized by typical disturbances in the circulatory state variables such as capillary pressure and plasma colloid osmotic pressure. The net water flow is increased because of an increase in filtration rate and a decrease in reabsorption rate. The resulting interstitial oedema leads to dilution of the free water proteins and a decrease in interstitial colloid osmotic pressure. The elevation of interstitial pressure leads to an increase in lymph flow. The local oedema is caused by changes in both the circulatory system and the interstitial space. There is an increase in both water and protein net flows. The latter is due to increased protein leakage to the interstitium. This results in an interstitial oedema with a higher protein concentration in free water than in general oedema. Because of the higher protein concentration in free water, the interstitial colloid osmotic pressure is at all times larger than the corresponding pressure in general oedema. In all three patients the general shape of the simulated and measured oedema curve were the same, but with minor differences in numerical values. It is interesting to note that the general oedema was larger than the local oedema in all three extensively burned patients. The results from the present investigation indicate the importance of monitoring either the total plasma protein concentration or the plasma colloid osmotic pressure and small vein pressure for guidance of a proper fluid resuscitation. The steady state 'oedema vs. venous pressure'-diagram obtained may also be used for evaluating the dynamic effects on general oedema formation due to changes in venous pressure and plasma protein concentration. It thus turned out that for a typical thermal injury with a decreased small vein pressure a continuous colloid infusion is to be preferred instead of an intermittent model of administration.

Energy, fat and nitrogen balance in healthy newborn infants during the first week after birth.

There are limited data in the literature concerning the energy, fat and nitrogen balances in healthy newborn infants of normal weight. For this reason, five healthy newborn infants were studied during the first week after birth. Balance studies on energy, fat, nitrogen, dry matter and water were performed. Oxygen consumption was determined by an open method. The weight decrease the first days was explained by a deficit of water and energy intake. Weight gain was seen when the water intake was 80-100 ml/kg/day and the energy intake 200-300 kJ/kg/day. A linear relation was found between the total evaporative water losses and ambient vapour pressure. The mean resting metabolic rate was 174 kJ/kg/day with the range 144-200 kJ/kg/day. With higher activity the metabolic rate increased 20-45%. Positive balances of nitrogen and fat were obtained when the intakes exceeded 150 and 275 mg/kg/day, respectively.

Failure of bacterial growth inhibition by amniotic fluid.

The bactericidal properties of amniotic fluid normally protect fetuses from late gestational infections by bacteria. Recently, such infections were found responsible for nearly a third of the perinatal deaths in Addis Ababa, Ethiopia. This prompted an analysis of the antimicrobial activity of amniotic fluid in patients in that city. The antimicrobial activity of fluid from 53 women, collected at term, was measured by a semiquantitative plate-count technique. Only one of the fluid samples was bactericidal, 12 were bacteriostatic, and 40 were noninhibitory to bacterial growth.