Influence of Plasma and Cerebrospinal Fluid Levels of Endothelin-1 and No in Reducing Cerebral Vasospasm after Subarachnoid Hemorrhage During Treatment with Mild Hypothermia, in a Dog Model

Hypothermia on the first day of ICU admission leads to increased in-hospital mortality in patients with subarachnoid hemorrhage

The relationship between early spontaneous hypothermia and adverse clinical outcomes in patients with subarachnoid hemorrhage (SAH) has not been paid much attention. We designed this retrospective cohort study to determine this relationship by analyzing the association between the lowest body temperature (T-lowest) on the first day of ICU admission and in-hospital mortality. In this study, 550 participants with non-traumatic SAH were chosen from the Medical Information Mart for Intensive Care (MIMIC)-IV database. Multivariate Cox regression analysis showed that T-lowest was nonlinearity correlated with in-hospital mortality (HR = 0.72, 95% CI: 0.59-0.86, p < 0.001). We divided the T-lowest into quartile groups. In comparison to reference group Q1 (31.30-36.06 ℃), group Q3 (36.56-36.72 ℃) had a 50% lower risk of death in the hospital (HR: 0.5, 95% CI: 0.28-0.87, p = 0.014). We further confirmed the curve-like relationship between T-lowest and in-hospital mortality using restricted cubic splines. The mortality is lowest when the T-lowest is close to 36.5 °C, and the risk of death is increased when the temperature is lower or higher than that. Our study demonstrates that in-hospital mortality is associated with T-lowest. Patients with non-traumatic SAH are at increased risk of death if their body temperature on the first day of ICU admission is too low.

Role of scalp hypothermia in patients undergoing minimally invasive evacuation of hypertensive cerebral hemorrhage

Objective

Hypertensive intracerebral hemorrhage (HICH) is one of the common multiple diseases in neurology. Patients with severe HICH have high risk of disability and poor prognosis.

Methods

In order to explore the clinical effect of mild hypothermia combined with micro-traumatic evacuation of cerebral hemorrhage in the treatment of severe HICH, 136 patients with severe HICH were selected and divided into control group and study group using random number table method, 68 each group. The control group was treated with micro-traumatic evacuation of cerebral hemorrhage on the basis of conventional symptomatic treatment, while the study group was treated with mild hypothermia combined with micro-traumatic evacuation of cerebral hemorrhage on the basis of conventional symptomatic treatment. After treatment, the two groups were followed up for eight weeks.

Results

The overall effective rate, residual hematoma volume, rebleeding rate, National Institute of Health stroke scale (NIHSS) score, Barthel index score and incidence of adverse reactions after treatment were observed and compared. The overall effective rate of the study group was 89.7%, which was significantly higher than that of the control group (67.6%). The mortality rate of the study group was 3.0%, which was significantly lower than that of the control group (14.7%, P<0.05). The residual hematoma volume and rebleeding rate of the study group were significantly lower than those of the control group (P<0.05). Before treatment, the NIHSS score and Barthel index score of the two groups had no significant differences (P>0.05). After treatment, they were improved, and the improvement of the study group was more significant (P<0.05). The incidence of adverse reactions in the study group was 10.0%, which was significantly lower than that in the control group (36.0%, P<0.05).

Conclusion

Mild hypothermia in combination with micro-traumatic evacuation of cerebral hemorrhage has significant clinical effect in the treatment of severe HICH. It can significantly improve neurological function and quality of life, causing few adverse reactions. Its clinical application value is high.

Targeted Temperature Management in Brain Injured Patients

Evidence from animal models indicates that lowering temperature by a few degrees can produce substantial neuroprotection. In humans, hypothermia has been found to be neuroprotective with a significant impact on mortality and long-term functional outcome only in cardiac arrest and neonatal hypoxic-ischemic encephalopathy. Clinical trials have explored the potential role of maintaining normothermia and treating fever in critically ill brain injured patients. This review concentrates on basic concepts to understand the physiologic interactions of thermoregulation, effects of thermal modulation in critically ill patients, proposed mechanisms of action of temperature modulation, and practical aspects of targeted temperature management.

Targeted Temperature Management in Brain Injured Patients

Evidence from animal models indicates that lowering temperature by a few degrees can produce substantial neuroprotection. In humans, hypothermia has been found to be neuroprotective with a significant impact on mortality and long-term functional outcome only in cardiac arrest and neonatal hypoxic-ischemic encephalopathy. Clinical trials have explored the potential role of maintaining normothermia and treating fever in critically ill brain injured patients. This review concentrates on basic concepts to understand the physiologic interactions of thermoregulation, effects of thermal modulation in critically ill patients, proposed mechanisms of action of temperature modulation, and practical aspects of targeted temperature management.

Intraoperative Targeted Temperature Management in Acute Brain and Spinal Cord Injury

Acute brain and spinal cord injuries affect hundreds of thousands of people worldwide. Though advances in pre-hospital and emergency and neurocritical care have improved the survival of some to these devastating diseases, very few clinical trials of potential neuro-protective strategies have produced promising results. Medical therapies such as targeted temperature management (TTM) have been trialed in traumatic brain injury (TBI), spinal cord injury (SCI), acute ischemic stroke (AIS), subarachnoid hemorrhage (SAH), and intracranial hemorrhage (ICH), but in no study has a meaningful effect on outcome been demonstrated. To this end, patient selection for potential neuro-protective therapies such as TTM may be the most important factor to effectively demonstrate efficacy in clinical trials. The use of TTM as a strategy to treat and prevent secondary neuronal damage in the intraoperative setting is an area of ongoing investigation. In this review we will discuss recent and ongoing studies that address the role of TTM in combination with surgical approaches for different types of brain injury.

Encephalic hemodynamic phases in subarachnoid hemorrhage: how to improve the protective effect in patient prognoses

Subarachnoid hemorrhage is frequently associated with poor prognoses. Three different hemodynamic phases were identified during subarachnoid hemorrhage: oligemia, hyperemia, and vasospasm. Each phase is associated with brain metabolic changes. In this review, we correlated the hemodynamic phases with brain metabolism and potential treatment options in the hopes of improving patient prognoses.

Therapeutic hypothermia reduces middle cerebral artery flow velocity in patients with severe aneurysmal subarachnoid hemorrhage

BACKGROUND

Transcranial Doppler (TCD) is widely used to detect and follow up cerebral vasospasm after subarachnoid hemorrhage (SAH). Therapeutic hypothermia might influence blood flow velocities assessed by TCD. The aim of the study was to evaluate the effect of hypothermia on Doppler blood flow velocity after SAH.

METHODS

In 20 patients treated with hypothermia (33°) due to refractory intracranial hypertension or delayed cerebral ischemia (DCI), mean flow velocity of the middle cerebral artery (MFV(MCA)) was assessed by TCD. Thirteen patients were treated with combined hypothermia and barbiturate coma and seven with hypothermia alone. MFV(MCA) was obtained within 24 h before and after induction of hypothermia as well as before and after rewarming.

RESULTS

Hypothermia was induced on average 5 days after SAH (range 1-12) and maintained for 144 h (range 29-270). After hypothermia induction, MFV(MCA) decreased from 113.7 ± 49.0 to 93.8 ± 44.7 cm/s (p = 0.001). The decrease was independent of SAH-related complications and barbiturate coma. MFV(MCA) further decreased by 28.2 cm/s between early and late hypothermia (p < 0.001). This second decrease was observed in patients with DCI (p < 0.001), but not in patients with intracranial hypertension (p = 0.715). Compared to late hypothermia, MFV(MCA) remained unchanged after rewarming (65.6 ± 32.1 vs 70.3 ± 36.8 cm/s; p = 0.219). However, patients treated with hypothermia alone showed an increase in MFV(MCA) after rewarming (p = 0.016).

CONCLUSION

Therapeutic hypothermia after SAH decreases Doppler blood flow velocity in both intracranial hypertension and DCI cases. The results can be the effect of hypothermia-related mechanisms or resolving cerebral vasospasm during prolonged hypothermia.

Nitric oxide in cerebral vasospasm: theories, measurement, and treatment

In recent decades, a large body of research has focused on the role of nitric oxide (NO) in the development of cerebral vasospasm (CV) following subarachnoid hemorrhage (SAH). Literature searches were therefore conducted regarding the role of NO in cerebral vasospasm, specifically focusing on NO donors, reactive nitrogen species, and peroxynitrite in manifestation of vasospasm. Based off the assessment of available evidence, two competing theories are reviewed regarding the role of NO in vasospasm. One school of thought describes a deficiency in NO due to scavenging by hemoglobin in the cisternal space, leading to an NO signaling deficit and vasospastic collapse. A second hypothesis focuses on the dysfunction of nitric oxide synthase, an enzyme that synthesizes NO, and subsequent generation of reactive nitrogen species. Both theories have strong experimental evidence behind them and hold promise for translation into clinical practice. Furthermore, NO donors show definitive promise for preventing vasospasm at the angiographic and clinical level. However, NO augmentation may also cause systemic hypotension and worsen vasospasm due to oxidative distress. Recent evidence indicates that targeting NOS dysfunction, for example, through erythropoietin or statin administration, also shows promise at preventing vasospasm and neurotoxicity. Ultimately, the role of NO in neurovascular disease is complex. Neither of these theories is mutually exclusive, and both should be considered for future research directions and treatment strategies.

Cerebral hemodynamics: concepts of clinical importance

Cerebral hemodynamics and metabolism are frequently impaired in a wide range of neurological diseases, including traumatic brain injury and stroke, with several pathophysiological mechanisms of injury. The resultant uncoupling of cerebral blood flow and metabolism can trigger secondary brain lesions, particularly in early phases, consequently worsening the patient's outcome. Cerebral blood flow regulation is influenced by blood gas content, blood viscosity, body temperature, cardiac output, altitude, cerebrovascular autoregulation, and neurovascular coupling, mediated by chemical agents such as nitric oxide (NO), carbon monoxide (CO), eicosanoid products, oxygen-derived free radicals, endothelins, K+, H+, and adenosine. A better understanding of these factors is valuable for the management of neurocritical care patients. The assessment of both cerebral hemodynamics and metabolism in the acute phase of neurocritical care conditions may contribute to a more effective planning of therapeutic strategies for reducing secondary brain lesions. In this review, the authors have discussed concepts of cerebral hemodynamics, considering aspects of clinical importance.