S100B protein in conscious carbon monoxide-poisoned rats treated with normobaric or hyperbaric oxygen

S-100β in predicting the need of hyperbaric oxygen in CO-induced delayed neurological sequels

BACKGROUND

Delayed neurological sequels (DNS) have been described after carbon monoxide (CO) poisoning. There is a need to find a new prognostic marker to guide the use of hyperbaric oxygen (HBO) therapy.

AIM

To evaluate serum S-100β level in patients presenting with acute CO poisoning as an indicator of poisoning severity and predictor of DNS occurrence and HBO need in those patients.

METHODS

This prospective cohort study included patients with acute CO poisoning. On admission, carboxyhemoglobin (COHb) and S-100β levels were measured. Patients were followed up for 6 months for signs of DNS.

RESULTS

Out of 50 patients, 6 only developed DNS. The mean of S-100β levels was significantly higher in patients with severe poisoning and those with DNS. Receiver operating characteristic curve analysis revealed that S-100β had an area under the curve 0. 871; at a cutoff value ≥ 0.67 µg/L, its sensitivity and specificity were 100% and 77.3%, respectively. The sensitivity of S-100β was significantly higher than that of COHb, while its specificity and overall accuracy were significantly higher than those of HBO criteria.

CONCLUSION

Serum S-100β level on admission could be a marker of poisoning severity and a predictor of CO-induced DNS development that guides the use of HBO therapy.

Hyperbaric oxygen preserves neurotrophic activity of carbon monoxide-exposed astrocytes

In astrocytes, carbon monoxide (CO) poisoning causes oxidative stress and mitochondrial dysfunction accompanied by caspase and calpain activation. Impairment in astrocyte function can be time-dependently reduced by hyperbaric (3bar) oxygen (HBO). Due to the central role of astrocytes in maintaining neuronal function by offering neurotrophic support we investigated the hypothesis that HBO therapy may exert beneficial effect on acute CO poisoning-induced impairment in intrinsic neurotrophic activity. Exposure to 3000ppm CO in air followed by 24-72h of normoxia caused a progressive decline of gene expression, synthesis and secretion of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) to different extent. 1h treatment with 100% oxygen disclosed a pressure- and time-dependent efficacy in preserving astrocytic neurotrophic support. The beneficial effect was most evident when the astrocytes were exposed to HBO 1-5h after exposure to CO. The results further support an active role of hyperbaric, not normobaric, oxygenation in reducing dysfunction of astrocytes after acute CO poisoning. By preserving endogenous neurotrophic activity HBO therapy might promote neuronal protection and thus prevent the occurrence of late neuropsychological sequelae.

The effectiveness of oxygen therapy in carbon monoxide poisoning is pressure- and time-dependent: a study on cultured astrocytes

Carbon monoxide (CO) poisoning causes neuronal and glial apoptosis that can result in delayed neurological symptoms. The damage of brain cells can be prevented by oxygen therapy. Based on the central role of astrocytes in maintaining neuronal function and viability we investigated the toxic effects of 3000ppm CO in air followed by 24h of normoxia and evaluated the possible protective influence of 100% normobaric oxygen or 100% oxygen at a pressure of 3bar (hyperbaric) against CO poisoning in these cells. CO/normoxia caused a progressive decline of viability, increase in reactive oxygen species and decline of mitochondrial membrane potential and intracellular ATP levels in cultured rat astrocytes. Increased caspase-9, caspase-8 and calpain activity converged in activation of caspase-3/7. 1h treatment with oxygen disclosed pressure- and time-dependent efficacy in restoring astrocytic mitochondrial function and the prevention of apoptosis. The protective effect was most evident when the astrocytes were exposed to hyperbaric oxygen, but not normobaric oxygen, 1-5h after exposure to CO.

Carbon monoxide poisoning in the 21st century

The world has experienced some very large shifts in the epidemiology of carbon monoxide poisoning, but it remains one of the most important toxicological global causes of morbidity and mortality. The diagnosis can be quickly confirmed with blood gases (pulse oximeters lack both sensitivity and specificity). Several strong predictors for serious neurological sequelae (prolonged loss of consciousness and elevated S100B) and reduced life expectancy (elevated troponin) are now reasonably well established. Despite this clearly defined high-risk group and extensive research into the pathophysiology, there has been little translation into better treatment. Much of the pathophysiological research has focused on hyperbaric oxygen. Yet it is apparent that clinical trials show little evidence for benefit from hyperbaric oxygen, and the most recent even raises the possibility of harm for repeated courses. More logical and promising potential antidotes have been under-researched, although recently both animal and small human studies suggest that erythropoietin may reduce S100B and prevent neurological sequelae. Major breakthroughs are likely to require further research on this and other treatments that may inhibit post-hypoxic inflammatory responses and apoptosis.

The role of heart-type fatty acid-binding protein in the evaluation of carbon monoxide poisoning in rats

Acute carbon monoxide (CO) poisoning can cause early and persistent damages in tissues sensitive to hypoxia. This study investigated serum heart-type fatty acid-binding protein (H-FABP) levels as a biomarker of acute CO poisoning in rats. The rats were exposed to a mixture of either 3000 (group A) or 5000 (group B) parts per million (ppm) CO in air, or to ambient air (group C, control group). Blood samples were taken just before, immediately after and 6 hours after the exposure, and serum H-FABP and troponin-I levels were measured. The consciousness level was evaluated just after the exposure. The survival rate was monitored for 7 days. Serum H-FABP levels increased just after the CO exposure in both groups A and B. Additionally, H-FABP level was higher in group B than in group A, immediately after the exposure. However, serum troponin-I levels only increased at 6 hours after the CO exposure in groups A and B. Consciousness and survival rates in group B were lower than that in group A. Our results suggest that H-FABP might have potential to be an early and quantitative parameter of clinical severity and prognosis in CO poisoning.

Elevated serum S100B protein and neuron-specific enolase levels in carbon monoxide poisoning

OBJECTIVE

Carbon monoxide (CO) poisoning causes cerebral and generalized hypoxia. This study aimed to assess the possible use of serum glial marker S100B protein and neuron-specific enolase (NSE) as biochemical markers of hypoxic brain damage in acute CO poisoning.

METHODS

Patients with acute CO poisoning admitted to the ED of 2 training hospitals (Ankara, Turkey) were included in this cross-sectional study. Serum levels of S100B and NSE were measured on admission. The patients were divided into 2 groups (unconscious and conscious). Twenty healthy adults were included in the study to serve as controls.

RESULTS

A total of 70 patients poisoned by CO (mean age +/- SD, 36.6 +/- 16.3 years; 64.3% women) were enrolled. Although S100B concentrations were higher in patients than in the control group (P = .018), no significant difference was determined between patient and control groups with respect to NSE concentrations (P = .801). A positive correlation was noted between levels of S100B and NSE (r = 0.388; P = .001). The S100B and NSE values were higher in unconscious patients than in the control group (P = .002 and P = .013, respectively). Furthermore, S100B and NSE values were higher in unconscious vs unconscious patients (P = .047 and P = .005, respectively).

CONCLUSION

Elevated serum S100B and NSE levels were associated with loss of consciousness in CO poisoning in this series of patients. Serum S100B and NSE may be useful markers in the assessment of clinical status in CO poisoning.