Reactive microglia and invading macrophages, which appear in brain damaged by stroke or trauma, secrete neuron-killing factors. This release of cytotoxic substances is a delayed process and is not detected until inflammatory cells reach a peak of reactivity by the second day after injury. Proximity to the site of injury and density of mononuclear phagocytes determine in part the amount of neurotoxic activity released by injured tissues. Moreover, drugs that suppress the accumulation of reactive microglia and macrophages also reduce tissue production of neuron poisons. Neurotoxins released by brain inflammatory cells or extracted directly from inflamed tissues are heat-stable, protease-resistant molecules < 500 daltons with actions blocked by N-methyl-D-aspartate (NMDA) receptor antagonists. These molecules are distinguished from free radical intermediates, bind to cation exchange resins, lack carboxyl moieties, and are separated from excitatory amino acids including glutamate or aspartate and from the NMDA receptor-mediated toxin quinolinic acid by ion exchange and reverse phase chromatography. Our data suggest that an unrecognized class of neuron-killing molecules produced by inflammatory cells mediate the delayed neuronal loss associated with stroke and trauma.

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In this study, we evaluate a preload-based Starling-like controller for implantable rotary blood pumps (IRBPs) using left ventricular end-diastolic pressure (PLVED) as the feedback variable. Simulations are conducted using a validated mathematical model. The controller emulates the response of the natural left ventricle (LV) to changes in PLVED. We report the performance of the preload-based Starling-like controller in comparison with our recently designed pulsatility controller and constant speed operation. In handling the transition from a baseline state to test states, which include vigorous exercise, blood loss and a major reduction in the LV contractility (LVC), the preload controller outperformed pulsatility control and constant speed operation in all three test scenarios. In exercise, preload-control achieved an increase of 54% in mean pump flow () with minimum loading on the LV, while pulsatility control achieved only a 5% increase in flow and a decrease in mean pump speed. In a hemorrhage scenario, the preload control maintained the greatest safety margin against LV suction. PLVED for the preload controller was 4.9 mmHg, compared with 0.4 mmHg for the pulsatility controller and 0.2 mmHg for the constant speed mode. This was associated with an adequate mean arterial pressure (MAP) of 84 mmHg. In transition to low LVC, for preload control remained constant at 5.22 L/min with a PLVED of 8.0 mmHg. With regards to pulsatility control, fell to the nonviable level of 2.4 L/min with an associated PLVED of 16 mmHg and a MAP of 55 mmHg. Consequently, pulsatility control was deemed inferior to constant speed mode with a PLVED of 11 mmHg and a of 5.13 L/min in low LVC scenario. We conclude that pulsatility control imposes a danger to the patient in the severely reduced LVC scenario, which can be overcome by using a preload-based Starling-like control approach.

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