Increases in spinal fluid osmolarity induced by mannitol

Untargeted Metabolite Profiling of Adipose Tissue in Rats Exposed to Mepiquat

Mepiquat (Mep) is a contaminant produced by Maillard reaction with reducing sugar, free lysine and an alkylating agent under typical roasting conditions, particularly in the range of 200-240 °C. It has been reported that exposure to Mep is harmful to rats. However, its metabolic mechanism is still not clear. In this study, untargeted metabolomics was used to reveal the effect of Mep on the metabolic profile of adipose tissue in Sprague-Dawley rats. Twenty-six differential metabolites were screened out. Eight major perturbed metabolic pathways were found, which were linoleic acid metabolism, Phenylalanine, tyrosine, and tryptophan biosynthesis, phenylalanine metabolism, arachidonic acid metabolism, Glycine, serine, and threonine metabolism, glycerolipid metabolism, Alanine, aspartate, and glutamate metabolism, and glyoxylate and dicarboxylic acid metabolism. This study lays a solid foundation for clarifying the toxic mechanism of Mep.

Comparison of Intracranial Pressure Measurements Before and After Hypertonic Saline or Mannitol Treatment in Children With Severe Traumatic Brain Injury

IMPORTANCE

Hyperosmolar agents are cornerstone therapies for pediatric severe traumatic brain injury. Guideline recommendations for 3% hypertonic saline (HTS) are based on limited numbers of patients, and no study to date has supported a recommendation for mannitol.

OBJECTIVES

To characterize current use of hyperosmolar agents in pediatric severe traumatic brain injury and assess whether HTS or mannitol is associated with greater decreases in intracranial pressure (ICP) and/or increases in cerebral perfusion pressure (CPP).

DESIGN, SETTING, AND PARTICIPANTS

In this comparative effectiveness research study, 1018 children were screened and 18 were excluded; 787 children received some form of hyperosmolar therapy during the ICP-directed phase of care, with 521 receiving a bolus. Three of these children were excluded because they had received only bolus administration of both HTS and mannitol in the same hour, leaving 518 children (at 44 clinical sites in 8 countries) for analysis. The study was conducted from February 1, 2014, to September 31, 2017, with follow-up for 1 week after injury. Final analysis was performed July 20, 2021.

INTERVENTIONS

Boluses of HTS and mannitol were administered.

MAIN OUTCOMES AND MEASURES

Data on ICP and CPP were collected before and after medication administration. Statistical methods included linear mixed models and corrections for potential confounding variables to compare the 2 treatments.

RESULTS

A total of 518 children (mean [SD] age, 7.6 [5.4] years; 336 [64.9%] male; 274 [52.9%] White) were included. Participants' mean (SD) Glasgow Coma Scale score was 5.2 (1.8). Bolus HTS was observed to decrease ICP and increase CPP (mean [SD] ICP, 1.03 [6.77] mm Hg; P < .001; mean [SD] CPP, 1.25 [12.47] mm Hg; P < .001), whereas mannitol was observed to increase CPP (mean [SD] CPP, 1.20 [11.43] mm Hg; P = .009). In the primary outcome, HTS was associated with a greater reduction in ICP compared with mannitol (unadjusted β, -0.85; 95% CI, -1.53 to -0.19), but no association was seen after adjustments (adjusted β, -0.53; 95% CI, -1.32 to 0.25; P = .18). No differences in CPP were observed. When ICP was greater than 20 mm Hg, greater than 25 mm Hg, or greater than 30 mm Hg, HTS outperformed mannitol for each threshold in observed ICP reduction (>20 mm Hg: unadjusted β, -2.51; 95% CI, -3.86 to -1.15, P < .001; >25 mm Hg: unadjusted β, -3.88; 95% CI, -5.69 to -2.06, P < .001; >30 mm Hg: unadjusted β, -4.07; 95% CI, -6.35 to -1.79, P < .001), with results remaining significant for ICP greater than 25 mm Hg in adjusted analysis.

CONCLUSIONS AND RELEVANCE

In this comparative effectiveness research study, bolus HTS was associated with lower ICP and higher CPP, whereas mannitol was associated only with higher CPP. After adjustment for confounders, both therapies showed no association with ICP and CPP. During ICP crises, HTS was associated with better performance than mannitol.

SHMT1 siRNA-Loaded hyperosmotic nanochains for blood-brain/tumor barrier post-transmigration therapy

The near-perivascular accumulation in solid tumors and short-lived span in circulation, derails even the most competent nanoparticles (NPs) from achieving their maximum therapeutic potential. Moreover, delivering them across the blood brain/tumor barrier (BBB/BTB) is further challenging to sought anticancer effect. To address these key challenges, we designed a linearly aligned nucleic acid-complexed polydixylitol-based polymeric nanochains (X-NCs), with inherent hyperosmotic properties enabling transmigration of the BBB/BTB and navigation through deeper regions of the brain tumor. The high aspect ratio adds shape-dependent functional aspects to parent particles by providing effective payload increment and nuclear factor of activated T cells-5 (NFAT5)-mediated cellular uptake. Therefore, serine hydroxymethyltransferase 1 (SHMT1) siRNA-loaded nanochains not only demonstrated to transmigrate the BTB, but also resulted in remarkably reducing the tumor size to 97% in the glioblastoma xenograft brain tumor mouse models. Our study illustrates how the hyperosmotic nanochains with high aspect ratio and aligned structure can accelerate a therapeutic effect in aggressive brain tumors post-transmigration of the BBB/BTB by utilizing an NFAT5 mode of uptake mechanism.

Mannitol decreases neocortical epileptiform activity during early brain development via cotransport of chloride and water

Seizures and brain injury lead to water and Cl^- accumulation in neurons. The increase in intraneuronal Cl^- concentration ([Cl^-]_i) depolarizes the GABA_A reversal potential (E_GABA) and worsens seizure activity. Neocortical neuronal membranes have a low water permeability due to the lack of aquaporins necessary to move free water. Instead, neurons use cotransport of ions including Cl^- to move water. Thus, increasing the extracellular osmolarity during seizures should result in an outward movement of water and salt, reducing [Cl^-]_i and improving GABA_A receptor-mediated inhibition. We tested the effects of hyperosmotic therapy with a clinically relevant dose of mannitol (20 mM) on epileptiform activity, spontaneous multiunit activity, spontaneous inhibitory post-synaptic currents (sIPSCs), [Cl^-]_i, and neuronal volume in layer IV/V of the developing neocortex of C57BL/6 and Clomeleon mice. Using electrophysiological techniques and multiphoton imaging in acute brain slices (post-natal day 7-12) and organotypic neocortical slice cultures (post-natal day 14), we observed that mannitol: 1) decreased epileptiform activity, 2) decreased neuronal volume and [Cl^-]_i through CCCs, 3) decreased spontaneous multi-unit activity frequency but not amplitude, and 4) restored the anticonvulsant efficacy of the GABA_A receptor modulator diazepam. Increasing extracellular osmolarity by 20 mOsm with hypertonic saline did not decrease epileptiform activity. We conclude that an increase in extracellular osmolarity by mannitol mediates the efflux of [Cl^-]_i and water through CCCs, which results in a decrease in epileptiform activity and enhances benzodiazepine actions in the developing neocortex in vitro. Novel treatments aimed to decrease neuronal volume may concomitantly decrease [Cl^-]_i and improve seizure control.

Efficacy of different hypertonic solutes in the treatment of refractory intracranial hypertension in severe head injury patients: A comparative study of 2ml/kg 7.5% hypertonic saline and 2ml/kg 20% mannitol

A prospective, randomized study to evaluate the clinical benefit of increasing the osmotic load of the hypertonic solution administered for the treatment of refractory intracranial hypertension episodes in patients with severe head injury. 25 patients with severe head injury and persistent coma, admitted in a Neurocritical Care Unit of a Tertiary Care Hospital, who required infusions of osmotic agents to treat episodes of intracranial hypertension resistant to well defined standard modes of therapy were randomly allocated to one of the two groups to receive isovolume infusions of either 7.5% hypertonic saline solution; HS [2400 mOsm/kg H2O] or 20% mannitol [1160 mOsm/kg of H2O] given 2ml/kg of either solution, i.e. 331.5 +/− 35.4 mOsm of hypertonic saline or 174.2 +/− 18 mOsm of mannitol per infusion. The variables recorded in the study were the duration and number of episodes of intracranial hypertension per day during the study period, which was stopped after the last episode of intracranial hypertension was recorded from intracranial pressure recording or after the allocated treatment failure. Patients of HS group were monitored for 7 +/− 6 days and those in the mannitol group for 8 +/− 5 days [p=NS]. The rate of failure for each treatment was also evaluated which was defined as the persistence of intracranial hypertension despite the two successive infusions of the same osmotic agent. The mean number of osmotic solute infusions was 3.4 +/− 4.5 in the HS group and 3.8 +/− 5.1 in mannitol group p=NS]. The mean number [7.1+/-2.9 vs. 14.6+/−3.4] of episodes of intracranial hypertension per day and the duration of such episode [62.6+/−28.1 vs. 93.4+/−37.2 min] was also significantly lower in the HS group [p<0.05]. The numbers of treatment failures were significantly lower in HS group: 1 out of 14 patients vs. 6 out of 11 patients [p<0.01]. In this study we have found that in patients with severe head injury requiring treatment with hypertonic solute for refractory intracranial hypertension, 2ml/kg body weight of 7.5% HS [356 +/− 14 mOsm] was more effective than giving 2ml/kg 20% mannitol [178 +/− 11mOsm]. Within the limitations of present study, the collected data suggest that giving 2ml/kg HS solution is an effective and safe initial treatment for intracranial hypertension episodes in head injury patients when there is indication of osmotherapy.

Urinary gas chromatography mass spectrometry metabolomics in asphyxiated newborns undergoing hypothermia: from the birth to the first month of life

BACKGROUND

Perinatal asphyxia is a severe clinical condition affecting around four million newborns worldwide. It consists of an impaired gas exchange leading to three biochemical components: hypoxemia, hypercapnia and metabolic acidosis.

METHODS

The aim of this longitudinal experimental study was to identify the urine metabolome of newborns with perinatal asphyxia and to follow changes in urine metabolic profile over time. Twelve babies with perinatal asphyxia were included in this study; three babies died on the eighth day of life. Total-body cooling for 72 hours was carried out in all the newborns. Urine samples were collected in each baby at birth, after 48 hours during hypothermia, after the end of the therapeutic treatment (72 hours), after 1 week of life, and finally after 1 month of life. Urine metabolome at birth was considered the reference against which to compare metabolic profiles in subsequent samples. Quantitative metabolic profiling in urine samples was measured by gas chromatography mass spectrometry (GC-MS). The statistical approach was conducted by using the multivariate analysis by means of principal component analysis (PCA) and orthogonal partial least square discriminant analysis (OPLS-DA). Pathway analysis was also performed.

RESULTS

The most important metabolites depicting each time collection point were identified and compared each other. At birth before starting therapeutic hypothermia (TH), urine metabolic profiles of the three babies died after 7 days of life were closely comparable each other and significantly different from those in survivors.

CONCLUSIONS

In conclusion, a plethora of data have been extracted by comparing the urine metabolome at birth with those observed at each time point collection. The modifications over time in metabolites composition and concentration, mainly originated from the depletion of cellular energy and homeostasis, seems to constitute a fingerprint of perinatal asphyxia.

Hyperosmotic polydixylitol for crossing the blood brain barrier and efficient nucleic acid delivery

Here, we introduce a polydixylitol based highly osmotic polymer that not only transmigrates the BBB by intra-arterial infusion of osmotic polyol but also triggers cellular uptake via modulation of caveolae mediated endocytosis.

Differential disruption of blood-brain barrier in severe traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a significant cause of death and disability in young adults, but not much is known about the incidence and characteristics of blood-brain barrier (BBB) dysfunction in this group. In this proof of concept study, we sought to quantify the incidence of BBB dysfunction (defined as a cerebrospinal fluid (CSF)-plasma albumin quotient of ≥0.007) and examine the relationship between plasma and CSF levels of proteins and electrolytes, in patients with severe TBI.

METHODS

We recruited 30 patients, all of whom were receiving hypertonic 20 % saline infusion for intracranial hypertension and had external ventricular drains in situ. Simultaneous CSF and blood samples were obtained. Biochemical testing was performed for sodium, osmolality, potassium, glucose, albumin, immunoglobulin-G, and total protein.

RESULTS

Eleven patients (37 %) showed evidence of impairment of passive BBB function, with a CSF-plasma albumin quotient of ≥0.007. There were strong positive correlations seen among CSF-plasma albumin quotient and CSF-plasma immunoglobulin-G quotient and CSF-plasma total protein quotient (r = 0.967, P < 0.001 and r = 0.995, P < 0.001, respectively). We also found a higher maximum intracranial pressure (24 vs. 21 mmHg, P = 0.029) and a trend toward increased mortality (27 vs. 11 %, P = 0.33) in patients with BBB disruption.

CONCLUSIONS

In summary, passive BBB dysfunction is common in patients with severe TBI, and may have important implications for effectiveness of osmotherapy and long-term outcomes. Also, our results suggest that the CSF-plasma total protein quotient, a measurement which is readily available, can be used instead of the CSF-plasma albumin quotient for evaluating BBB dysfunction.

3D differentiation of neural stem cells in macroporous photopolymerizable hydrogel scaffolds

Neural stem/progenitor cells (NSPCs) are the stem cell of the adult central nervous system (CNS). These cells are able to differentiate into the major cell types found in the CNS (neurons, oligodendrocytes, astrocytes), thus NSPCs are the mechanism by which the adult CNS could potentially regenerate after injury or disorder. Microenviromental factors are critical for guiding NSPC differentiation and are thus important for neural tissue engineering. In this study, D-mannitol crystals were mixed with photocrosslinkable methacrylamide chitosan (MAC) as a porogen to enhance pore size during hydrogel formation. D-mannitol was admixed to MAC at 5, 10 and 20 wt% D-mannitol per total initial hydrogel weight. D-mannitol crystals were observed to dissolve and leave the scaffold within 1 hr. Quantification of resulting average pore sizes showed that D-mannitol addition resulted in larger average pore size (5 wt%, 4060±160 µm(2), 10 wt%, 6330±1160 µm(2), 20 wt%, 7600±1550 µm(2)) compared with controls (0 wt%, 3150±220 µm(2)). Oxygen diffusion studies demonstrated that larger average pore area resulted in enhanced oxygen diffusion through scaffolds. Finally, the differentiation responses of NSPCs to phenotypic differentiation conditions were studied for neurons, astrocytes and oligodendrocytes in hydrogels of varied porosity over 14 d. Quantification of total cell numbers at day 7 and 14, showed that cell numbers decreased with increased porosity and over the length of the culture. At day 14 immunohistochemistry quantification for primary cell types demonstrated significant differentiation to the desired cells types, and that total percentages of each cell type was greatest when scaffolds were more porous. These results suggest that larger pore sizes in MAC hydrogels effectively promote NSPC 3D differentiation.

Hypertonic saline and its effect on intracranial pressure, cerebral perfusion pressure, and brain tissue oxygen

OBJECTIVE

Hypertonic saline is emerging as a potentially effective single osmotic agent for control of acute elevations in intracranial pressure (ICP) caused by severe traumatic brain injury. This study examines its effect on ICP, cerebral perfusion pressure (CPP), and brain tissue oxygen tension (PbtO2).

METHODS

Twenty-five consecutive patients with severe traumatic brain injury who were treated with 23.4% NaCl for elevated ICP were evaluated. Bolt catheter probes were placed in the noninjured hemisphere, and hourly ICP, mean arterial pressure, CPP, and PbtO2 values were recorded. Thirty milliliters of 23.4% NaCl was infused over 15 minutes for intracranial hypertension, defined as ICP greater than 20 mm Hg. Twenty-one male patients and 4 female patients aged 16 to 64 years were included. The mean presenting Glasgow Coma Scale score was 5.7.

RESULTS

Mean pretreatment values included an ICP level of 25.9 mm Hg and a PbtO2 value of 32 mm Hg. The posttreatment ICP level was decreased by a mean of 8.3 mm Hg (P < 0.0001), and there was an improvement in PbtO2 of 3.1 mm Hg (P < 0.01). ICP of more than 31 mm Hg decreased by 14.2 mm Hg. Pretreatment CPP values of less than 70 mm Hg increased by a mean of 6 mm Hg (P < 0.0001). No complications occurred from this treatment, with the exception of electrolyte and chemistry abnormalities. At 6 months postinjury, the mortality rate was 28%, with 48% of patients achieving a favorable outcome by the dichotomized Glasgow Outcome Scale.

CONCLUSION

Hypertonic saline as a single osmotic agent decreased ICP while improving CPP and PbtO2 in patients with severe traumatic brain injury. Patients with higher baseline ICP and lower CPP levels responded to hypertonic saline more significantly.

Does serum osmolarity change as a result of the reflex neuroprotective mechanism of cerebral osmo-regulation after minor head trauma?

OBJECTIVE

It is well known that changes in cerebral hemodynamics occur after traumatic brain injury (TBI). Osmo-regulation in the brain is important for maintaining a constant milieu in the central nervous system. Nevertheless, to our knowledge, early osmolarity changes after minor head injury have not been studied until now.

METHODS

In this study, serum osmolarity was measured in 99 patients with minor head trauma. As a control group, blood samples were drawn from 99 patients who had a minor trauma in an extremity. Serum osmolarity was estimated using a fully automatic biochemical autoanalyzer within the first 3 hours after the trauma.

RESULTS

The mean serum osmolarity levels were 286.08+/-10.17 mOsm/L in the study group and 290.94+/-5.65 mOsm/L in the control group (p<0.001). However, after age adjustment between the study and control groups, this statistical significance was found to be valid only for patients over 30 years of age.

CONCLUSION

It was noted that serum osmolarity levels decrease in the first 3 hours following minor head trauma in patients over 30 years of age. Further studies into this area could provide guidance for the management/treatment of elderly patients.

Moderate and severe traumatic brain injury in adults

Traumatic brain injury (TBI) is a major health and socioeconomic problem that affects all societies. In recent years, patterns of injury have been changing, with more injuries, particularly contusions, occurring in older patients. Blast injuries have been identified as a novel entity with specific characteristics. Traditional approaches to the classification of clinical severity are the subject of debate owing to the widespread policy of early sedation and ventilation in more severely injured patients, and are being supplemented with structural and functional neuroimaging. Basic science research has greatly advanced our knowledge of the mechanisms involved in secondary damage, creating opportunities for medical intervention and targeted therapies; however, translating this research into patient benefit remains a challenge. Clinical management has become much more structured and evidence based since the publication of guidelines covering many aspects of care. In this Review, we summarise new developments and current knowledge and controversies, focusing on moderate and severe TBI in adults. Suggestions are provided for the way forward, with an emphasis on epidemiological monitoring, trauma organisation, and approaches to management.

Cochlear implant and inner ear malformation. Proposal for an hyperosmolar therapy at surgery

The objective of this retrospective study is to evaluate the efficiency of hyperosmolar therapy for cerebrum spinal fluid (CSF) leakage in cochlear implant (CI) surgery in children with inner ear malformations. Between 1991 and 2006, 490 cochlear implantations were performed in Armand Trousseau Children's Hospital. Thirty-seven patients (7.5%) had inner ear malformation. They were classified as isolated enlargement of the vestibular aqueduct (EVA) (18 cases), incomplete partition (IP) (11 cases), common cavity (CC) (1 case) and variable canal and vestibular malformations (VSCC) (7 cases). A hyperosmolar protocol was applied during surgery to 13 patients after 2003 (Gp) to be compared to the 24 patients without treatment previously to this date (G0). Mean age at implant CI was 8.1 years (1-20 years), mean follow up was 3.9 years (1 month-15 years). Per operative observations were collected for all patients with an empiric method of evaluation of the leakage. A grading using five steps ranged from Grade 0 (no leak) to Grade 4 (gusher). Grading, complications and perceptive results in closed and open set word (Lafon lists) at respectively preoperatively, at 3 and 24 months were gathered and compared between the two groups. Important per operative leak was observed (Grade 4) in 24.3% cases (9/37) of Grade 4, 88.8% of them in G0 (8/9). In 66.6% cases there was a severe dysplasia (CC or IP) (6/9), to be compared to the 21.4% of cases of severe dysplasia with Grade<3 (6/28) (p=0.02). Grade 4 was seen in 45% cases of IP (5/11); it represented 33.3% of the IP in Gp (1/3), and 50% of the IP in G0 (4/8) (p>0.05). Grade 4 was seen in 16.6% cases of EVA (3/18); there were no Grade 4 observed in Gp (0/10), and 37.5% cases of EVA in G0 (3/8) (p=0.04). Grade 4 was observed in 100% case in CC in the G0 (1/1). Severe complications were misplacement of the electrode in one case (G0), persistent leakage in one case (G0) and meningitis in one case (Gp). Vertigo was observed in 29.7% of cases (11/37) in this population, 72.7% of them in G0 (8/11). Vertigo was associated to severe dysplasia in 75% cases in G0 (6/8), and to EVA in all cases in Gp. In G0, mean perceptive scores showed for G0, preoperatively and at 3 months, respectively, 1.3% and 50.6% in closed set word (CSW), and 65.9% in open set words at 2 years. In Gp mean perceptive scores showed preoperatively and at 3 months, respectively 6.1% and 69.8% in CSW, and 81% in open set words at 2 years. The differences between the two groups are not significant (p>0.05). Osmotherapy is known to be effective for cerebral oedema and regularly used in neurological surgery. In inner ear malformation, gusher at surgery is directly related to the intra-cerebral pressure (ICP). Corresponding to neurosurgical practice, the mainstay of our protocol rests on hyperosmolar treatment, to reduce the ICP the time of the surgery. Our results suggest that this treatment is effective for a better control of leakage at cochleostomy on EVA, and could be effective on more severe malformations. No severe complication related to surgery was seen in Gp. Its good tolerance could allow its use in most patients with inner ear malformation. Vertigo was a frequent complication. The possibility of vertigo depends on the initial vestibular status and on the course of the surgery. The protocol could protect the vestibular function, lowering the pressure and quantity of the liquid issue. The treatment does not seem to influence the perceptive results.

Formula for use of mannitol in patients with intracerebral haemorrhage and high intracranial pressure

BACKGROUND AND OBJECTIVE

Although mannitol has been widely used in hospitals to treat patients with high intracranial pressure (ICP) secondary to intracerebral haemorrhage (ICH), no universal agreement has been reached regarding the optimal dosage of this agent for achieving appropriate intracranial decompression. The aim of this study was to investigate the effects of different mannitol dosages on ICP and the effects of other factors, such as sex, age, haemorrhage location and haematoma volume, on the ICP-lowering effect of mannitol. The data obtained were then used to construct a formula for estimating the total dosage of mannitol required to reduce ICP in individual patients with ICH.

PATIENTS AND METHODS

A total of 72 patients with ICH and elevated ICP monitored in our intensive care unit were included in this study. Patients with ICH who had hypoxaemia (arterial oxygen saturation <90%), severe functional disturbances of the liver or kidney, acidosis or pathological changes in the visual conducting pathway were not included in this study. Each patient received 20% intravenous mannitol 125 mL every 4, 6 or 8 hours per day to treat elevated ICP, with ICP levels being measured before administration of mannitol and at least three times per day during administration of the drug. When the ICP reached a fixed level, the dosage of mannitol was gradually reduced. The total dosage of mannitol used to reduce the ICP from the highest value to the fixed value was calculated. Data on the patients' sex, age, haemorrhage location and haematoma volume were also obtained. Multivariate regression analysis of the results enabled development of a formula for use of mannitol in patients with ICH and elevated ICP.

RESULTS

Use of mannitol significantly decreased ICP in all patients. The effect of mannitol on ICP reduction was dose-dependent during the period of ICP reduction (p < 0.05) but not after the ICP had reached a fixed level; this limited effectiveness of mannitol when its dosage reaches a certain level was termed 'mannitol saturation dosage'. The reduction in ICP with mannitol was not statistically significantly affected by the patient's sex or age, but was significantly correlated with both haemorrhage location and haematoma volume (p < 0.05). The reduction in ICP with mannitol was greater in patients with supratentorial ICH compared with those with infratentorial ICH (p < 0.0001).

CONCLUSION

The total mannitol dosage required for individual patients with ICH and elevated ICP can be calculated by considering the location of the haemorrhage, the volume of the haematoma and the pretreated ICP reading. To this end, the following formula was derived in the study: Total dosage of mannitol (mL of 20% mannitol) = (x + 31.17900 x y - 3.39853 x z - 244.47590)/0.00752, where x = the pretreated ICP (mmH(2)O), y = the haemorrhage location (supratentorial ICH: y = 0, infratentorial ICH: y = 1) and z = the volume of haematoma (mL). Use of this formula in the clinical setting should help reduce the possibility of adverse effects resulting from administration of excessive dosages of mannitol.

[Management of severe traumatic brain injury]

Severe brain injuries, most often occurring in young subjects, are a major source of lost work years. These injuries are medical and surgical emergencies. Prehospital management of severe brain injuries requires intubation and mechanical ventilation aimed at normal arterial carbon dioxide pressure. Signs of transtentorial herniation: Uni- or bilateral mydriasis requires immediate perfusion of 20% mannitol or hypertonic sodium chloride. Neurological disorders after head injury justify emergency cerebral computed tomography. The presence of a mass syndrome or signs of transtentorial herniation are in principle indications for surgery. Specialized hospital management is essential. In the case of refractory intracranial hypertension, the cerebral perfusion pressure and osmotherapy should be adapted to the volume of the cerebral contusion. The use of deep hypothermia and barbiturates should be minimized as much as possible. Magnetic resonance imaging makes it possible to identify the cerebral lesions.

Effects of Mannitol Bolus Administration on Intracranial Pressure, Cerebral Extracellular Metabolites, and Tissue Oxygenation in Severely Head-Injured Patients

BACKGROUND

Osmotic agents are widely used to lower elevated intracranial pressure (ICP). However, little data are available regarding cerebral oxygenation and metabolism in the traumatized brains studied under clinical conditions. The present prospective, open-labeled clinical study was designed to investigate whether administration of mannitol, with the aim of reducing moderate intracranial hypertension, improves cerebral metabolism and oxygenation in patients after severe traumatic brain injury (TBI).

METHODS

Multimodal cerebral monitoring (MCM), consisting of intraparenchymal ICP, tissue oxygenation (ptiO2), and micro dialysis measurements was initiated in six male TBI patients (mean age 45 years; Glasgow Coma Scale score <9). A total of 14 mannitol boli (20%, 0.5g/kg, 20 minutes infusion time) were administered to treat ICP exceeding 20 mm Hg (2.7 kPa). Temporal alterations determined by MCM after mannitol infusions were recorded for 120 minutes. Microdialysates were assayed immediately for extracellular glucose, lactate, pyruvate, and glutamate concentrations.

RESULTS

Elevated ICP was successfully treated in all cases. This effect was maximal 40 minutes after start of infusion (25 +/- 6 mm Hg [3.3 +/- 0.8 kPa] to 17 +/- 3 mm Hg [2.3 +/- 0.4 kPa], p < 0.05) and lasted up to 100 minutes. Cerebral ptiO2 remained unaffected (21 +/- 5 mm Hg [2.8 +/- 0.7 kPa] to 23 +/- 6 mm Hg [3.1 +/- 0.8 kPa], n.s.). Microdialysate concentrations of all analytes rose unspecifically by 10% to 40% from baseline, reaching maximum concentrations 40 to 60 minutes after start of the infusion.

CONCLUSIONS

Mannitol efficiently reduces increased ICP. At an ICP of up to 30 mm Hg [4 kPa] it does not affect cerebral oxygenation. Unspecific increases of extracellular fluid metabolites can be explained by transient osmotic dehydration. Additional mechanisms, such as increased cerebral perfusion and blood volume, might explain an accelerated return to baseline.

Hypertonic saline (7.2%) in 6% hydroxyethyl starch reduces intracranial pressure and improves hemodynamics in a placebo-controlled study involving stable patients with subarachnoid hemorrhage*

OBJECTIVE

To compare the effects of a bolus infusion of hypertonic saline hydroxyethyl starch with the effects of normal saline (placebo) on intracranial pressure (ICP) and cerebral perfusion pressure in patients with spontaneous subarachnoid hemorrhage.

DESIGN AND SETTING

Prospective, randomized, single-blinded, placebo-controlled study in a university hospital.

PATIENTS

A total of 22 mechanically ventilated patients with spontaneous subarachnoid hemorrhage with stable ICP between 10 and 20 mm Hg.

INTERVENTIONS

During the course of 30 mins, 2 mL/kg of either 7.2% saline in 6% hydroxyethyl starch 200/0.5 (HSS) or of normal saline was infused. The effects were observed for another 180 mins.

MEASUREMENTS AND MAIN RESULTS

Mean change in ICP after intervention (DeltaICP) calculated from the average of all observations was -3.3 (sd 2.6) mm Hg in the HSS group vs. -0.3 (sd 1.3) mm Hg in the normal saline group. Mean difference between the groups (HSS - normal saline) was -3.0 mm Hg (95% confidence interval, -4.9 to -1.1; p = .004). Mean peak change after HSS was -5.6 (range, -0.8 to -12.2) mm Hg after 64 (range, 40 to 115) mins. Mean difference in cerebral perfusion pressure change between the groups (HSS - normal saline) was 5.4 mm Hg (95% confidence interval, 2.2 to 8.6; p = .002), and mean difference in cardiac index change, measured as the area under the curve for the whole study period, corresponded to 0.2 L.min.m (95% confidence interval, 0.03 to 0.4; p = .025).

CONCLUSIONS

In this placebo-controlled study involving spontaneous subarachnoid hemorrhage patients with normal to moderately increased ICP, 2 mL/kg HSS reduced ICP and increased cerebral perfusion pressure significantly. Maximum effect was reached at twice the infusion time of 30 mins. There were also beneficial hemodynamic effects with increased cardiac index in the HSS group.

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.