In vivo multiparametric monitoring of brain functions under intracranial hypertension following mannitol administration

Shedding light on mitochondrial function by real time monitoring of NADH fluorescence: I. Basic methodology and animal studies

Normal mitochondrial function in the process of metabolic energy production is a key factor in maintaining cellular activities. Many pathological conditions in animals, as well as in patients, are directly or indirectly related to dysfunction of the mitochondria. Monitoring the mitochondrial activity by measuring the autofluorescence of NADH has been the most practical approach since the 1950s. This review presents the principles and technological aspects, as well as typical results, accumulated in our laboratory since the early 1970s. We were able to apply the fiber-optic-based NADH fluorometry to many organs monitored in vivo under various pathophysiological conditions in animals. These studies were the basis for the development of clinical monitoring devices as presented in accompanying article. The encouraging experimental results in animals stimulated us to apply the same technology in patients after technological adaptations as described in the accompanying article. Our medical device was approved for clinical use by the FDA.

Hypertonic mannitol in mice poisoned by a convulsive dose of soman: antilethal activity without neuroprotection

A convulsive dose of soman induces seizure-related brain damage (SRBD), including cerebral edema (CE) and cell death. In 1993, an American study demonstrated that hypertonic mannitol (Mann) intravenously (i.v.) administered 1 min and 5h post-soman was an effective neuroprotectant in intoxicated rats. Using a similar protocol, we recently failed to reproduce this success in intoxicated mice. In the present study, also performed in mice, the persistence or the amplitude of the osmotic load was increased by reducing the time interval between two injections of Mann or by augmenting the number of injections. Mice were pre-treated with the oxime HI-6 and then intoxicated with a convulsive dose of soman (172 microg/kg). Afterward, they were administered a first i.v. bolus of Mann 20% 1 min post-challenge and a second one either 5, or 2, or 1h after. Additional animals were given either one (1 min post-soman), or two (1 min and 1h post-soman), or three (1 min, 1 and 2h post-soman) series of three injections of Mann at 5 min intervals. Non-intoxicated mice treated with Mann (same protocols as above) and intoxicated mice treated with Mann vehicle (saline) served as controls. At 24h post-intoxication, the survivors were sacrificed and their brains prepared for quantitative histological assessment of cell damage, CE, and ventricle size. Whatever the protocol, Mann had no effect on soman-induced convulsions but did provide considerable antilethal activity. Histologically, Mann did not reduce the cell damage or CE. It even showed a dose-dependent trend toward aggravation of SRBD in some regions and promoted subarachnoid hemorrhages. Conversely, in one of the treatment protocol, it reduced soman-induced enlargement of ventricle size. Although treatment with hypertonic Mann showed some benefit on mortality and ventricle size, it failed to be an effective neuroprotector in soman-intoxicated mice and even increased the detrimental impact of soman at the cerebral level. Therefore, no clear recommendation could be drawn from the present study in view of a possible clinical use of hyperosmolar treatment in the medical management of soman poisoning.

Hyperosmolar treatment of soman-induced brain lesions in mice: evaluation of the effects through diffusion-weighted magnetic resonance imaging and through histology

PURPOSE

A convulsive dose of soman induces seizure-related brain damage (SRBD), including cerebral edema (CE) and neuronal loss. In the present study on soman-intoxicated mice, we applied diffusion-weighted magnetic resonance imaging (DW-MRI) and quantitative histology, and we measured brain water content to investigate the antiedematous and neuroprotective efficacies of two hyperosmolar treatments: mannitol (Mann) and hypertonic saline (HTS).

METHODS

Mice intoxicated with soman (172 microg/kg after a protective pretreatment) were administered 1 min and 5-h post-challenge an i.v. bolus of saline, of Mann or of HTS. 1 day later, mice were examined with DW-MRI and then sacrificed for brain histology. Additional animals were intoxicated and treated similarly for the measurement of the brain water content (dry/wet weight method).

RESULTS

In intoxicated controls, a significant decrease of the apparent diffusion coefficient (ADC), numerous damaged (eosinophilic) cells, high edema scores, and a significant increase in brain water content were detected 24-h post-challenge in sensitive brain structures. These soman-induced changes were not significantly modified by treatment with Mann or HTS.

CONCLUSIONS

Treatment with hyperosmolar solutions did not reduce the effects of soman on ADC, on cell damage and on CE. Therefore, despite similar treatment protocols, the prominent protection by Mann that was previously demonstrated by others in poisoned rats, was not reproduced in our murine model.

An integrated model of thermodynamic–hemodynamic–pharmacokinetic system and its application on decoupling control of intracranial temperature and pressure in brain hypothermia treatment

Brain hypothermia treatment (BHT) is an intensive care characterized by simultaneous managements of various vital signs, such as intracranial temperature (ICT) and pressure (ICP), of the severe neuropatient. Medical treatments including therapeutic ambient cooling and diuresis are separately carried out based on the experience of the medical staff involved in the clinical management of various pathophysiological processes, such as thermodynamics, hemodynamics and pharmacokinetics. However, no special attention has been paid to the interactions among these subsystems in therapeutic hypothermia because of the lack of theoretical knowledge. Therefore, quantitative analyses using an integrated model of various physiological processes and their interactions are of pressing need. In the present paper, we propose a general compartmental model to describe the pathophysiological processes of the three aforementioned dynamics, on account of the dynamical analogy of temperature, pressure and concentration. The model is verified by the agreement of model-based simulation results with clinical evidence. Based on responses of the integrated model to various stimuli, a transfer function matrix is identified to linearly approximate the characteristic interrelationships between medical treatments (ambient cooling and diuresis) and the vital signs (ICT and ICP). Then a controller that decouples ambient cooling and diuresis is proposed for efficient management of ICT and ICP, enhancement of hypothermic decompression and reduction of diuretic dosage. Decoupling control simulation indicates that ICT and ICP of the integrated model, representing a patient under BHT, can be simultaneously regulated by a single PID controller for ambient cooling and another for diuresis. The proposed decoupler effectively establishes hypothermic decompression, reduces the dosage of diuretic and improves ICP management. Theoretical analyses of the integrated model and decoupling control of ICT and ICP provide insights into the intensive care of various pathophysiological processes in patients undergoing BHT.