Early Transient Mild Hypothermia Attenuates Neurologic Deficits and Brain Damage After Experimental Subarachnoid Hemorrhage in Rats

Targeted Temperature Management for Severe Subarachnoid Hemorrhage Using Endovascular and Surface Cooling Systems: A Nonrandomized Interventional Study Using Historical Control

BACKGROUND

Although targeted temperature management (TTM) may mitigate brain injury for severe subarachnoid hemorrhage (SAH), rebound fever correlates with poor outcomes.

OBJECTIVE

To study the effect of endovascular TTM after rewarming from initial surface cooling during a high-risk period for delayed cerebral ischemia.

METHODS

We studied patients with World Federation of Neurological Surgeons grade V SAH before and after the introduction of endovascular TTM. Both groups (36 patients each) were treated with TTM at 34 °C with conventional surface cooling immediately after SAH diagnosis, together with emergency aneurysm repair. When rewarmed to 36 °C, around 7 days later, the study group underwent TTM at 36 to 38 °C for 7 days with an endovascular cooling system. The control group was treated with antipyretics.

RESULTS

Sex, age, Glasgow Coma Scale score, modified Fisher computed tomography classification, aneurysm location, and treatment methods were not different between the study and control groups. Differences were detected in the incidence of fever >38 °C (13 vs 26 patients, P = .0021), duration of fever >38 °C (4.1 vs 18.8 hours, P = .0021), incidence of vasospasm-related cerebral infarction (17% vs 42%, P = .037), and the likelihood of excellent outcomes (0 and 1 on a modified Rankin Scale) at 6 months (42% vs 17%, P = .037). In endovascular TTM, shivering occurred more frequently in patients with better outcomes, requiring aggressive treatment to avoid fever.

CONCLUSION

Endovascular TTM at 36 to 38 °C after surface cooling was feasible and safely performed in patients with severe SAH. Combined TTM for 2 weeks was associated with a lower incidence of vasospasm-related infarction and may improve outcomes.

Diagnosis and Treatment of Unruptured Intracranial Aneurysms and Aneurysmal Subarachnoid Hemorrhage

Unruptured intracranial aneurysms (UIAs) are commonly acquired vascular lesions that form an outpouching of the arterial wall due to wall thinning. The prevalence of UIAs in the general population is 3.2%. In contrast, an intracranial aneurysm may be manifested after rupture with classic presentation of a thunderclap headache suggesting aneurysmal subarachnoid hemorrhage (SAH). Previous consensus suggests that although small intracranial aneurysms (<7 mm) are less susceptible to rupture, aneurysms larger than 7 mm should be treated on a case-by-case basis with consideration of additional risk factors of aneurysmal growth and rupture. However, this distinction is outdated. The PHASES score, which comprises data pooled from several prospective studies, provides precise estimates by considering not only the aneurysm size but also other variables, such as the aneurysm location. The International Study of Unruptured Intracranial Aneurysms is the largest observational study on the natural history of UIAs, providing the foundation to the current guidelines for the management of UIAs. Although SAH accounts for only 3% of all stroke subtypes, it is associated with considerable burden of morbidity and mortality. The initial management is focused on stabilizing the patient in the intensive care unit with close hemodynamic and serial neurologic monitoring with endovascular or open surgical aneurysm treatment to prevent rebleeding. Since the results of the International Subarachnoid Aneurysm Trial, treatment of aneurysmal SAH has shifted from surgical clipping to endovascular coiling, which demonstrated higher odds of survival free of disability at 1 year after SAH. Nonetheless, aneurysmal SAH remains a public health hazard and is associated with high rates of disability and death.

Neuroprotective Strategies in Aneurysmal Subarachnoid Hemorrhage (aSAH)

Aneurysmal subarachnoid hemorrhage (aSAH) remains a disease with high mortality and morbidity. Since treating vasospasm has not inevitably led to an improvement in outcome, the actual emphasis is on finding neuroprotective therapies in the early phase following aSAH to prevent secondary brain injury in the later phase of disease. Within the early phase, neuroinflammation, thromboinflammation, disturbances in brain metabolism and early neuroprotective therapies directed against delayed cerebral ischemia (DCI) came into focus. Herein, the role of neuroinflammation, thromboinflammation and metabolism in aSAH is depicted. Potential neuroprotective strategies regarding neuroinflammation target microglia activation, metalloproteases, autophagy and the pathway via Toll-like receptor 4 (TLR4), high mobility group box 1 (HMGB1), NF-κB and finally the release of cytokines like TNFα or IL-1. Following the link to thromboinflammation, potential neuroprotective therapies try to target microthrombus formation, platelets and platelet receptors as well as clot clearance and immune cell infiltration. Potential neuroprotective strategies regarding metabolism try to re-balance the mismatch of energy need and supply following aSAH, for example, in restoring fuel to the TCA cycle or bypassing distinct energy pathways. Overall, this review addresses current neuroprotective strategies in aSAH, hopefully leading to future translational therapy options to prevent secondary brain injury.

[Effect of mild hypothermia on behaviors of rats with intracerebral hemorrhage and the possible mechanism]

OBJECTIVE

To explore the effect of mild hypothermia on inflammatory response and angiogenesis in brain tissues of rats with intracerebral hemorrhage (ICH) and its possible mechanism for improving behavioral deficits of the rats After ICH.

METHODS

A total of 120 healthy male SD rats were randomly divided into sham operation group, ICH group and mild hypothermia group. Rat models of ICH were established in the latter two groups by stereotactic injection of autogenous blood in the brain, and the rats in the sham operation group received injection of normal saline in the same manner. At 15 min after modeling, the rats in hypothermia group were subjected to mild hypothermia (30-32 ℃) for 8 h followed by rewarming (37-38 ℃); the body temperature was maintained at 37-38 ℃ in the other two groups. At 2, 4, 7, 14 and 21 days after the treatment, Longa scoring, balance beam scoring and Berderson scoring were used to evaluate the behavioral deficits of the rats. Immunohistochemical staining was used to detect the protein expressions of tumor necrosis factor-α (TNF-α) and nuclear factor-κB (NF-κB) in the brain tissue of the rats, and the mRNA expressions of α subunit of hypoxia-inducible factor 1 (HIF1-α) and vascular endothelial growth factor (VEGF) were detected using RT- PCR.

RESULTS

At 2, 4, 7, 14 and 21 days after the treatment, the behavioral scores of the rats were significantly higher in ICH group and mild induced hypothermia group than in the sham operation group (P < 0.05 or 0.01). The protein expressions of TNF-α and NF-κB and mRNA expressions of HIF1-α and VEGF were significantly higher in ICH group and mild hypothermia group than in the sham operation group (P < 0.01). The behavioral scores were significantly lower in mild hypothermia group than in ICH group (P < 0.05), and the protein expressions of TNF-α and NF-κB were lower and the mRNA expressions of HIF1- α and VEGF were higher in mild hypothermia group than in ICH group (P < 0.05 or 0.01).

CONCLUSIONS

Mild hypothermia can improve behavioral deficits in rats with ICH possibly by antagonizing brain inflammation and promoting angiogenesis.

The Effect of Prophylactic Hypothermia on Neurophysiological and Functional Measures in the Setting of Iatrogenic Spinal Cord Impact Injury

BACKGROUND

Iatrogenic spinal cord injury (iSCI) during spinal corrective surgery can result in devastating complications, such as paraplegia or paraparesis. Perioperatively, iSCI often occurs as a direct injury during spinal cord instrumentation placement. Currently, treatment of iSCI remains limited to posttraumatic hypothermia, which has demonstrated some value in recent clinical trials. Here we report the outcomes of preinjury hypothermia initiated preprocedurally and maintained for a considerable time after iSCI.

METHODS

Twenty-six female Sprague-Dawley rats were assigned at random to either a normothermic group (36 °C) or a hypothermic group (32 °C) and then underwent a laminectomy procedure at the T8 level. Each group was further divided at random to receive a 200-kdyn force contusive spinal cord injury or a sham impact. Hypothermic rats were then rewarmed after 2 hours of hypothermic treatment. Behavioral scores, temperature profiles, weights, and somatosensory evoked potentials were obtained at baseline and at specified time points after the procedure.

RESULTS

The median survival was 42 days for the iSCI hypothermic group and 11 days for the iSCI normothermic group (hazard ratio, 3.82; 95% confidence interval, 1.52-9.57). The probability of survival was significantly higher in the iSCI hypothermic group compared with the iSCI normothermic group (χ² = 4.18; P = 0.040). The hypothermic group exhibited a higher Basso, Beattie and Bresnahan (BBB) locomotor rating scale score (17 vs. 14; P < 0.01), lower normalized latencies (1.06 ± 0.16 seconds vs. 1.34 ± 0.17 seconds; P = 0.04), and higher peak-to-peak amplitudes (0.32 ± 0.10 μV vs. 0.12 ± 0.09 μV; P = 0.005).

CONCLUSIONS

The use of prophylactic hypothermia before iSCI was significantly associated with an increased survival rate, higher BBB scores, and improved neurophysiological measures.

Acute reaction of arterial blood vessels after experimental subarachnoid hemorrhage - An in vivo microscopic study

Subarachnoid hemorrhage (SAH) results in a rapid decrease of cerebral perfusion. While cerebral perfusion pressure (CPP) may quickly recover, a sustained decrease of cerebral blood flow (CBF) has been observed. Acute vasospasm has been concluded from this mismatch. This study was conducted to visualize and investigate immediate vascular reactions during and after experimental SAH. Male Sprague-Dawley rats were subjected to SAH by the endovascular filament model (n = 7) or served as controls (n = 4). Videomicroscopy was performed via a cranial window. Regions of interest were defined in areas covered by videomicroscopy and arterial diameters measured at defined time-points from 15 min before until 3 h after SAH. Local CBF was monitored over the opposite hemisphere by laser-Doppler flowmetry. Local CBF showed a typical decrease immediately after vessel perforation followed by an incomplete recovery in the 3 h thereafter. Videomicroscopy demonstrated a sharp decrease of the arterial diameter in the first minutes after SAH. In some animals, SAH was followed by a complete disappearance of arterial vessel filling. In the following minutes, arterial filling reappeared or improved, respectively. All animals subjected to SAH showed significant vasospasm in subarachnoid arteries. This is the first study to visualize acute vascular reactions during and immediately after SAH. Although the cranial window technique only covers a part of the cerebral vasculature, it covers cerebral vessels rather distant from the site of endovascular perforation. Therefore, it is likely that acute vasospasm observed in the monitored areas reflects a global vascular reaction.

Aggf1 attenuates neuroinflammation and BBB disruption via PI3K/Akt/NF-κB pathway after subarachnoid hemorrhage in rats

Background

Neuroinflammation and blood-brain barrier (BBB) disruption are two critical mechanisms of subarachnoid hemorrhage (SAH)-induced brain injury, which are closely related to patient prognosis. Recently, angiogenic factor with G-patch and FHA domain 1 (Aggf1) was shown to inhibit inflammatory effect and preserve vascular integrity in non-nervous system diseases. This study aimed to determine whether Aggf1 could attenuate neuroinflammation and preserve BBB integrity after experimental SAH, as well as the underlying mechanisms of its protective roles.

Methods

Two hundred forty-nine male Sprague-Dawley rats were subjected to the endovascular perforation model of SAH. Recombinant human Aggf1 (rh-Aggf1) was administered intravenously via tail vein injection at 1 h after SAH induction. To investigate the underlying neuroprotection mechanism, Aggf1 small interfering RNA (Aggf1 siRNA) and PI3K-specific inhibitor LY294002 were administered through intracerebroventricular (i.c.v.) before SAH induction. SAH grade, neurological score, brain water content, BBB permeability, Western blot, and immunohistochemistry were performed.

Results

Expression of endogenous Aggf1 was markedly increased after SAH. Aggf1 was primarily expressed in endothelial cells and astrocytes, as well as microglia after SAH. Administration of rh-Aggf1 significantly reduced brain water content and BBB permeability, decreased the numbers of infiltrating neutrophils, and activated microglia in the ipsilateral cerebral cortex following SAH. Furthermore, rh-Aggf1 treatment improved both short- and long-term neurological functions after SAH. Meanwhile, exogenous rh-Aggf1 significantly increased the expression of PI3K, p-Akt, VE-cadherin, Occludin, and Claudin-5, as well as decreased the expression of p-NF-κB p65, albumin, myeloperoxidase (MPO), TNF-α, and IL-1β. Conversely, knockdown of endogenous Aggf1 aggravated BBB breakdown, inflammatory response and neurological impairments at 24 h after SAH. Additionally, the protective roles of rh-Aggf1 were abolished by LY294002.

Conclusions

Taken together, exogenous Aggf1 treatment attenuated neuroinflammation and BBB disruption, improved neurological deficits after SAH in rats, at least in part through the PI3K/Akt/NF-κB pathway.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1211-8) contains supplementary material, which is available to authorized users.