Local saline infusion into ischemic territory induces regional brain cooling and neuroprotection in rats with transient middle cerebral artery occlusion

Hypothermic neuroprotection by targeted cold autologous blood transfusion in a non-human primate stroke model

Over decades, nearly all attempts to translate the benefits of therapeutic hypothermia in stroke models of lower-order species to stroke patients have failed. Potentially overlooked reasons may be biological gaps between different species and the mismatched initiation of therapeutic hypothermia in translational studies. Here, we introduce a novel strategy of selective therapeutic hypothermia in a non-human primate ischemia-reperfusion model, in which autologous blood was cooled ex vivo and the cool blood transfusion was administered at the middle cerebral artery just after the onset of reperfusion. Cold autologous blood cooled the targeted brain rapidly to below 34 °C while the rectal temperature remained around 36 °C with the assistance of a heat blanket during a 2-h hypothermic process. Therapeutic hypothermia or extracorporeal-circulation related complications were not observed. Cold autologous blood treatment reduced infarct sizes, preserved white matter integrity, and improved functional outcomes. Together, our results suggest that therapeutic hypothermia, induced by cold autologous blood transfusion, was achieved in a feasible, swift, and safe way in a non-human primate model of stroke. More importantly, this novel hypothermic approach conferred neuroprotection in a clinically relevant model of ischemic stroke due to reduced brain damage and improved neurofunction. This study reveals an underappreciated potential for this novel hypothermic modality for acute ischemic stroke in the era of effective reperfusion.

Therapeutic hypothermia for stroke: Unique challenges at the bedside

Therapeutic hypothermia has shown promise as a means to improving neurological outcomes at several neurological conditions. At the clinical level, it has been shown to improve outcomes in comatose survivors of cardiac arrest and in neonatal hypoxic ischemic encephalopathy, but has yet to be convincingly demonstrated in stroke. While numerous preclinical studies have shown benefit in stroke models, translating this to the clinical level has proven challenging. Major obstacles include cooling patients with typical stroke who are awake and breathing spontaneously but often have significant comorbidities. Solutions around these problems include selective brain cooling and cooling to lesser depths or avoiding hyperthermia. This review will cover the mechanisms of protection by therapeutic hypothermia, as well as recent progress made in selective brain cooling and the neuroprotective effects of only slightly lowering brain temperature. Therapeutic hypothermia for stroke has been shown to be feasible, but has yet to be definitively proven effective. There is clearly much work to be undertaken in this area.

The intra-arterial selective cooling infusion system: A mathematical temperature analysis and in vitro experiments for acute ischemic stroke therapy

Introduction

The neuroprotection of acute ischemic stroke patients can be achieved by intra‐arterial selective cooling infusion using cold saline, which can decrease brain temperature without influencing the body core temperature. This approach can lead to high burdens on the heart and decreased hematocrit in the scenario of loading a high amount of liquid for longtime usage. Therefore, autologous blood is utilized as perfusate to circumvent those side effects.

Methods

In this study, a prototype instrument with an autologous blood cooling system was developed and further evaluated by a mathematical model for brain temperature estimation.

Results

Hypothermia could be achieved due to the adequate cooling capacity of the prototype system, which could provide the lowest cooling temperature into the blood vessel of 10.5°C at 25 rpm (209.7 ± 0.8 ml/min). And, the core body temperature did not alter significantly (−0.7 ~ −0.2°C) after 1‐h perfusion. The cooling rate and temperature distributions of the brain were analyzed, which showed a 2°C decrease within the initial 5 min infusion by 44 ml/min and 13.7°C perfusate.

Conclusion

This prototype instrument system could safely cool simulated blood in vitro and reperfuse it to the target cerebral blood vessel. This technique could promote the clinical application of an autologous blood perfusion system for stroke therapy.

Updates on Selective Brain Hypothermia: Studies From Bench Work to Clinical Trials

Thrombectomy or thrombolysis are the current standards of care for acute ischemic stroke (AIS), however, due to time constraints regarding operations and a multitude of contraindications, AIS remains one of the leading causes of death and chronic disability worldwide. In recent years, therapeutic hypothermia has been explored as an adjuvant therapy for AIS treatment and has shown potential to improve outcomes in patients with AIS. In particular, selective therapeutic hypothermia has shown to markedly reduce infarct volumes and have neuroprotective effects, while also minimizing many systemic side effects seen with systemic therapeutic hypothermia. Both preclinical and clinical trials have demonstrated that selective therapeutic hypothermia is a safe and feasible therapy for patients who have suffered an AIS. In this review, we summarize the current update on selective hypothermia through major studies that have been conducted in rodents, large animals, and clinical trials, and briefly discuss the prospects of selective hypothermic research. We hope this review helps facilitate the exploration of other possible adjuvant treatment modalities in the neuroprotection of ischemic stroke, whether upon symptom onset or after vascular recanalization.

Postcooling But Not Precooling Benefits Motor Recovery by Suppressing Cell Death After Surgical Spinal Cord Injury in Rats

BACKGROUND

Surgical spinal cord injury (SSCI) is often inevitable in patients with intramedullary lesions. Although regional hypothermia (RH) has been demonstrated neuroprotective, the value of priming RH in SSCI has never been studied. Herein, the authors investigated the impact of pre- and post-RH on neurologic recovery in a clinically relevant model.

METHODS

An SSCI model was established at T10. RH was conducted by focal 4oC saline perfusion; room temperature (RT) saline was used as controls. Animals were randomized into 6 groups: SHAM-RT/RH, Pre-RT/RH, and Post-RT/RH. Motor and sensory functions were evaluated using the Basso, Beattie, and Bresnahan rating scale and Plantar test 2 weeks after surgery. TUNEL assay and Fluoro-Jade C staining were conducted to examine the cell death, and the alterations of apoptotic markers including total and cleaved casepase 3, Bcl-2, and Bax, as well as the pyroptotic proteins including NLRP3, ASC, and caspase 1, were determined.

RESULTS

RH perfusion successfully created an intramedullary hypothermia approximately at 24oC, while RT controls remained above 30oC. Animals receiving postinjury RH had the least cell death and the best motor performance, while pre-RH showed the most dead cells and worst hind limb movements. Immunoblotting depicted that post-RH suppressed both apoptotic and pyroptotic death as the cleaved/total caspase 3, Bcl-2/Bax ratio, and NLRP3/ASC/caspase 1 signaling were inhibited. Priming cooling, on the contrary, elevated pyroptosis and did not affect apoptosis significantly.

CONCLUSIONS

Priming RH before surgical incision could not be supported as it caused excessive cell death. In contrast, instant introduction of RH is beneficial in rescuing neurologic function.

Phenotype Shifting in Astrocytes Account for Benefits of Intra-Arterial Selective Cooling Infusion in Hypertensive Rats of Ischemic Stroke

The translational failure of neuroprotective therapies in stroke may be influenced by the mismatch of existing comorbidities between animal models and patients. Previous studies found that single-target neuroprotective agents reduced infarction in Sprague-Dawley but not in spontaneously hypertensive rats. It is of great interest to explore whether multi-target neuroprotectants and stroke models with comorbidities should be used in further translational researches. Ischemic stroke was induced in normotensive or hypertensive rats by 90- or 120-min middle cerebral artery occlusion (MCAO) and reperfusion. Intra-Arterial Selective Cooling Infusion (IA-SCI) was started at the onset of reperfusion for 30 minutes. Acute neurological deficits, infarct volumes, gene expression and markers of A1-like and A2-like astrocytes were evaluated. In further analysis, TNFα and IL-1α were administrated intracerebroventricularly, phenotype shifting of astrocytes and infarct volumes were assessed. Normobaric oxygen treatment, as a negative control, was also assessed in hypertensive rats. IA-SCI led to similar benefits in normotensive rats with 120-min MCAO and hypertensive rats with both 90-min and 120-min MCAO, including mitigated functional deficit and reduced infarct volumes. IA-SCI shifted astrocyte phenotypes partly by downregulating A1-like astrocytes and upregulating A2-like astrocytes in both RNA and protein levels. Upregulated A1-type astrocyte markers levels, induced by intracerebroventricular injection of TNFα and IL-1α, were closely related to increased infarct volumes in hypertensive rats, despite receiving IA-SCI treatment. In addition, infarct volumes and A1/A2-like genes were not affected by normobaric oxygen treatment. IA-SCI reduced infarction in both normotensive and hypertensive rats. Our results demonstrated the neuroprotective effects of IA-SCI in hypertensive rats may be related with phenotype shifting of astrocytes.

Selective therapeutic cooling: To maximize benefits and minimize side effects related to hypothermia

Selective therapeutic cooling is a promising technique for reducing final infarct volume and improving outcomes in ischemic stroke, especially as research regarding brain reperfusion continues to be explored. A recent study provided promising results on the safety and feasibility of selective therapeutic hypothermia via a closed-loop cooling catheter system for intra-carotid blood cooling in an ovine stroke model, but they failed to find efficacy of this method in this model. It is a major step forward from bench to bed side, but enhancing benefits of selective therapeutic cooling may need to take into account a more targeted induction of brain hypothermia and should mitigate potential side effects related to inducing hypothermia.

Selective intra-carotid blood cooling in acute ischemic stroke: A safety and feasibility study in an ovine stroke model

Selective therapeutic hypothermia (TH) showed promising preclinical results as a neuroprotective strategy in acute ischemic stroke. We aimed to assess safety and feasibility of an intracarotid cooling catheter conceived for fast and selective brain cooling during endovascular thrombectomy in an ovine stroke model.Transient middle cerebral artery occlusion (MCAO, 3 h) was performed in 20 sheep. In the hypothermia group (n = 10), selective TH was initiated 20 minutes before recanalization, and was maintained for another 3 h. In the normothermia control group (n = 10), a standard 8 French catheter was used instead. Primary endpoints were intranasal cooling performance (feasibility) plus vessel patency assessed by digital subtraction angiography and carotid artery wall integrity (histopathology, both safety). Secondary endpoints were neurological outcome and infarct volumes.Computed tomography perfusion demonstrated MCA territory hypoperfusion during MCAO in both groups. Intranasal temperature decreased by 1.1 °C/3.1 °C after 10/60 minutes in the TH group and 0.3 °C/0.4 °C in the normothermia group (p < 0.001). Carotid artery and branching vessel patency as well as carotid wall integrity was indifferent between groups. Infarct volumes (p = 0.74) and neurological outcome (p = 0.82) were similar in both groups.Selective TH was feasible and safe. However, a larger number of subjects might be required to demonstrate efficacy.

Neuroprotective effect of magnesium supplementation on cerebral ischemic diseases

Ischemic encephalopathy is associated with a high mortality and rate of disability. The most common type of ischemic encephalopathy, ischemic stroke, is the second leading cause of death in the world. At present, the main treatment for ischemic stroke is to reopen blocked blood vessels. However, despite revascularization, many patients are not able to achieve good functional results. At the same time, the strict time window (<4.5 h) of thrombolytic therapy limits clinical application. Therefore, it is important to explore effective neuroprotective drugs for the treatment of ischemic stroke. Magnesium is a natural calcium antagonist, which exerts neuroprotective effects through various mechanisms. However, while most basic studies have shown that magnesium supplementation can help treat cerebral ischemia, intravenous magnesium supplementation in large clinical trials has failed to improve prognosis of ischemic patients. Therefore, we review the basic and clinical studies of magnesium supplementation for cerebral ischemia. According to the route of administration, treatment can be divided into intraperitoneal magnesium supplementation, intravenous magnesium supplementation, arterial magnesium supplementation and intracranial magnesium supplementation. We also summarized the potential influencing factors of magnesium ion intervention in cerebral ischemia injury. Finally, in combination with influencing factors derived from basic research, this article proposes three future research directions, including magnesium supplementation into the circulatory system combined with magnesium supplementation in the lateral ventricle, magnesium supplementation in the lateral ventricle combined with hypothermia therapy, and lateral ventricle magnesium supplementation combined with intracarotid magnesium supplementation combined with selective hypothermia.

A Clinical Test for a Newly Developed Direct Brain Cooling System for the Injured Brain and Pattern of Cortical Brainwaves in Cooling, Noncooling, and Dead Brain

To ensure the direct delivery of therapeutic hypothermia at a selected constant temperature to the injured brain, a newly innovated direct brain cooling system was constructed. The practicality, effectiveness, and safety of this system were clinically tested in our initial series of 14 patients with severe head injuries. The patients were randomized into two groups: direct brain cooling at 32°C and the control group. All of them received intracranial pressure (ICP), focal brain oxygenation, brain temperature, and direct cortical brainwave monitoring. The direct brain cooling group did better in the Extended Glasgow Outcome Scale at the time of discharge and at 6 months after trauma. This could be owing to a trend in the monitored parameters; reduction in ICP, increment in cerebral perfusion pressure, optimal brain redox regulation, near-normal brain temperature, and lessening of epileptic-like brainwave activities are likely the reasons for better outcomes in the cooling group. Finally, this study depicts interesting cortical brainwaves during a transition time from being alive to dead. It is believed that the demonstrated cortical brainwaves follow the principles of quantum physics.

Neuroprotective Effects of Early Hypothermia Induced by Phenothiazines and DHC in Ischemic Stroke

METHODS

Adult male Sprague Dawley rats were studied in 4 groups: (1) sham; (2) stroke; (3) stroke treated with pharmacological hypothermia before reperfusion (interischemia hypothermia); and (4) stroke treated with pharmacological hypothermia after reperfusion is initiated (inter-reperfusion hypothermia). The combination of chlorpromazine and promethazine with dihydrocapsaicin (DHC) was used to induce hypothermia. To compare the neuroprotective effects of drug-induced hypothermia between the interischemia and inter-reperfusion groups, brain damage was evaluated using infarct volume and neurological deficits at 24 h reperfusion. In addition, mRNA expressions of NADPH oxidase (NOX) subunits (gp91phox, p67phox, p47phox, and p22phox) and glucose transporter subtypes (GLUT1 and GLUT3) were determined by real-time PCR at 6 and 24 h reperfusion. ROS production was measured by flow cytometry assay at the same time points.

RESULTS

In both hypothermia groups, the cerebral infarct volumes and neurological deficits were reduced in the ischemic rats. At 6 and 24 h reperfusion, ROS production and the expressions of NOX subunits and glucose transporter subtypes were also significantly reduced in both hypothermia groups as compared to the ischemic group. While there were no statistically significant differences between the two hypothermia groups at 6 h reperfusion, brain damage was significantly further decreased by interischemia hypothermia at 24 h.

CONCLUSION

Both interischemia and inter-reperfusion pharmacological hypothermia treatments play a role in neuroprotection after stroke. Interischemia hypothermia treatment may be better able to induce stronger neuroprotection after ischemic stroke. This study provides a new avenue and reference for stronger neuroprotective hypothermia before vascular recanalization in stroke patients.

A Systematic Review and Meta-Analysis of Animal Studies Testing Intra-Arterial Chilled Infusates After Ischemic Stroke

Background: As not all ischemic stroke patients benefit from currently available treatments, there is considerable need for neuroprotective co-therapies. Therapeutic hypothermia is one such co-therapy, but numerous issues have hampered its clinical use (e.g., pneumonia risk with whole-body cooling). Some problems may be avoided with brain-specific methods, such as intra-arterial selective cooling infusion (IA-SCI) into the arteries supplying the ischemic tissue. Objective: Our research question was about the efficacy of IA-SCI in animal middle cerebral artery occlusion models. We hypothesized that IA-SCI would be beneficial, but translationally-relevant study elements may be missing (e.g., aged animals). Methods: We completed a systematic review of the PubMed database following the PRISMA guidelines on May 21, 2020 for animal studies that administered IA-SCI in the peri-reperfusion period and assessed infarct volume, behavior (primary meta-analytic endpoints), edema, or blood-brain barrier injury (secondary endpoints). Our search terms included: "focal ischemia" and related terms, "IA-SCI" and related terms, and "animal" and related terms. Nineteen studies met inclusion criteria. We adapted a methodological quality scale from 0 to 12 for experimental design assessment (e.g., use of blinding/randomization, a priori sample size calculations). Results: Studies were relatively homogenous (e.g., all studies used young, healthy animals). Some experimental design elements, such as blinding, were common whereas others, such as sample size calculations, were infrequent (median methodological quality score: 5; range: 2-7). Our analyses revealed that IA-SCI provides benefit on all endpoints (mean normalized infarct volume reduction = 23.67%; 95% CI: 19.21-28.12; mean normalized behavioral improvement = 35.56%; 95% CI: 25.91-45.20; mean standardized edema reduction = 0.95; 95% CI: 0.56-1.34). Unfortunately, blood-brain barrier assessments were uncommon and could not be analyzed. However, there was substantial statistical heterogeneity and relatively few studies. Therefore, exploration of heterogeneity via meta-regression using saline infusion parameters, study quality, and ischemic duration was inconclusive. Conclusion: Despite convincing evidence of benefit in ischemic stroke models, additional studies are required to determine the scope of benefit, especially when considering additional elements (e.g., dosing characteristics). As there is interest in using this treatment alongside current ischemic stroke therapies, more relevant animal studies will be critical to inform patient studies.

Intra-arterial Cold Saline Infusion in Stroke: Historical Evolution and Future Prospects

Acute ischemic stroke (AIS) is a perpetual threat to life and functionality due to its high morbidity and mortality. In the past several decades, therapeutic hypothermia has garnered interest as an effective neuroprotective method in the setting of AIS. However, traditional hypothermic methods have been criticized for their low cooling efficiency and side effects. Intra-arterial cold saline infusion (IA-CSI), as a novel hypothermic method, not only minimizes these side effects, but is also perfectly integrated with widely accepted recanalization modalities in AIS, thereby serving as a promising prospect for clinical translation. In this article, we review the historical development of IA-CSI, summarize major studies of IA-CSI in rodents, large animals, and humans to date, and suggest insight into future development prospects in the field of AIS. We hope that this article will provide inspiration for the future application of hypothermia in AIS patients.

Selective intra-arterial brain cooling improves long-term outcomes in a non-human primate model of embolic stroke: Efficacy depending on reperfusion status

Nearly all stroke neuroprotection modalities, including selective intra-arterial cooling (SI-AC), have failed to be translated from bench to bed side. Potentially overlooked reasons may be biological gaps, inadequate attention to reperfusion states and mismatched attention to neurological benefits. To advance stroke translation, we describe a novel thrombus-based stroke model in adult rhesus macaques. Intra-arterial thrombolysis with tissue plasminogen activator leads to three clinically relevant outcomes - complete, partial, and no recanalization based on digital subtraction angiography. We also find reperfusion as a prerequisite for SI-AC-induced benefits, in which models with complete or partial reperfusion exhibit significantly reduced infarct volumes, mitigated neurological deficits, improved upper limb motor dysfunction in both acute and chronic stages; however, no further neuroprotection is observed in those without reperfusion. In summary, we discover reperfusion as a crucial regulator of SI-AC-induced neuroprotection and provide insights of long-term functional benefits in behavior and imaging levels. Our findings could be important not only for the translational prerequisite and potential molecular targets, but also for this thrombus-thrombolysis model in monkeys as a powerful tool for further translational stroke studies.

Infusion of Cold Saline into the Carotid Artery Does Not Affect Outcome After Intrastriatal Hemorrhage

Localized brain hypothermia (HYPO) can be achieved by infusing cold saline into the carotid artery of animals and patients. Studies suggest that HYPO improves behavioral and histological outcomes in focal ischemia models. Given that ischemic stroke and intracerebral hemorrhage (ICH) share pathophysiological overlap, we tested whether cold saline infusion is safe and neuroprotective when given during collagenase-induced ICH. Eighty-five adult male Sprague-Dawley rats were used. Experiment 1 investigated brain and body temperature changes associated with a cold saline infusion paradigm that was scaled from patients according to brain weight and blood volume (3 mL/20-minute infusion). Experiment 2 determined whether HYPO aggravated bleeding volume. Experiment 3 investigated if cerebral edema or elemental concentrations were altered by HYPO. We also collected core body temperature and activity data through telemetry. Experiment 4 investigated whether behavioral outcomes (e.g., skilled reaching) and tissue loss were influenced by HYPO. Our HYPO protocol decreased the ipsilateral striatal temperature by ∼0.20°C (p < 0.001), with no other effects. HYPO did not affect hematoma volume (p = 0.64), cerebral edema (p = 0.34), or elemental concentrations (p = 0.49) at 24 hours post-ICH. Although ICH caused persistent behavioral impairments, HYPO did not improve behavioral outcomes (measured by a neurological deficit scale, cylinder, and the staircase test; p > 0.05 for all). Brain tissue loss was not different between groups on day 28 post-ICH (p = 0.90). Although cold saline infusion appears to be safe in the acute post-ICH period, there was no evidence that this therapy improved outcome. However, our treatment protocol was relatively mild and additional interventions might help improve efficacy. Finally, our findings may also speak to the safety of this cooling approach in focal ischemia where hemorrhagic transformation is a risk; future studies on this issue are needed.

Hypothermic neuroprotection against acute ischemic stroke: The 2019 update

Acute ischemic stroke is a leading cause of death and disability worldwide. Therapeutic hypothermia has long been considered as one of the most robust neuroprotective strategies. Although the neuroprotective effects of hypothermia have only been confirmed in patients with global cerebral ischemia after cardiac arrest and in neonatal hypoxic ischemic encephalopathy, establishing standardized protocols and strictly controlling the key parameters may extend its application in other brain injuries, such as acute ischemic stroke. In this review, we discuss the potential neuroprotective effects of hypothermia, its drawbacks evidenced in previous studies, and its potential clinical application for acute ischemic stroke especially in the era of reperfusion. Based on the different conditions between bench and bedside settings, we demonstrate the importance of vascular recanalization for neuroprotection of hypothermia by analyzing numerous literatures regarding hypothermia in focal cerebral ischemia. Then, we make a thorough analysis of key parameters of hypothermia and introduce novel hypothermic therapies. We advocate in favor of the process of clinical translation of intra-arterial selective cooling infusion in the era of reperfusion and provide insights into the prospects of hypothermia in acute ischemic stroke.

New Endovascular Approach for Hypothermia With Intrajugular Cooling and Neuroprotective Effect in Ischemic Stroke

Background and Purpose—

Induction of hypothermia as a stroke therapy has been limited by logistical challenges. This study was designed to determine the hypothermic and neuroprotective efficacy of infusing cold saline directly into the internal jugular (IJ) vein and compare the effects of IJ hypothermia to those achieved by intracarotid artery hypothermia in an ischemic stroke model.

Methods—

The right middle cerebral artery was occluded in rats using an intraluminal filament. Immediately following reperfusion, hypothermia was achieved by infusing isotonic saline through microcatheter into the right IJ or right intracarotid over 30 minutes. Infarct sizes, neurological deficits, blood-brain barrier damage, edema volume, blood-brain barrier associated molecules (MMP-9 [matrix metallopeptidase 9] and AQP-4 [aquaporin 4]), and apoptosis-associated proteins (Bcl-2 and cleaved Caspase-3) were measured.

Results—

We found that both IJ- and intracarotid-based infusion cooled the brain robustly with a minimal effect on rectal temperatures. This brain cooling led to significantly reduced infarct volumes at 24 hours after reperfusion, as well as decreased expression of the proapoptotic protein cleaved Caspase-3 and increased expression of the antiapoptotic protein Bcl-2. Intracarotid and IJ cooling also aided in blood-brain barrier maintenance, as shown by decreased edema volumes, reduced Evans Blue leakage, and decreased expression of edema-facilitating proteins (MMP-9 and AQP-4). Both cooling methods then translated to preserved neurological function as determined by multiple functional tests over a 28-day observation period. Most importantly, the cooling and neuroprotective efficacy of IJ cooling was comparable to intracarotid cooling by almost every metric evaluated.

Conclusions—

Compared with intracarotid infusion, IJ infusion conferred a similar degree of hypothermia and neuroprotection following ischemic stroke. Given the ease of establishing vascular access via the internal jugular vein and the powerful neuroprotection that hypothermia provides, IJ brain cooling could be used as a promising hypothermia-induction modality going forward.

Evidence and opportunities of hypothermia in acute ischemic stroke: Clinical trials of systemic versus selective hypothermia

Stroke is the second leading cause of death globally and the third leading cause disability. Acute ischemic stroke (AIS), resulting from occlusion of major vessels in the brain, accounts for approximately 87% of strokes. Despite this large majority, current treatment options for AIS are severely limited and available to only a small percentage of patients. Therapeutic hypothermia (TH) has been widely used for neuroprotection in the setting of global ischemia postcardiac arrest, and recent evidence suggests that hypothermia may be the neuroprotective agent that stroke patients desperately need. Several clinical trials using systemic or selective cooling for TH have been published, reporting the safety and feasibility of these methods. Here, we summarize the major clinical trials of TH for AIS and provide recommendations for future studies.

Selective retrograde cerebral cooling in complete cerebral circulatory arrest

BACKGROUND AND PURPOSE:

Cerebral hypothermia is a known neuroprotectant with promising applications in the treatment of ischemic events. Although systemic cooling is standard in post-cardiac arrest care, the deleterious effects of whole-body cooling have precluded it from translation into a viable treatment option for acute ischemic stroke (AIS). Selective cerebral cooling has been proposed as a method to minimize these risks while granting the neuroprotection of therapeutic hypothermia in AIS.

METHODS:

In a porcine model (n = 3), the efficacy of selective retrograde cerebral cooling through the internal jugular vein was evaluated in the setting of complete cerebral circulatory arrest. Furthermore, a novel endovascular device and cooling system enabling selective retrograde cerebral cooling were studied in a normothermic perfused cadaver.

RESULTS AND CONCLUSION:

Neurologic assessment of animals receiving this therapy reflected substantial neuroprotection in animals undergoing both 15 min and 30 min of otherwise catastrophic complete cerebral circulatory arrest. The novel endovascular device and cooling system were validated in human anatomy, demonstrating successful cerebral cooling, and feasibility of this mechanism of selective retrograde cerebral cooling.

Neuroprotection by mesenchymal stem cell (MSC) administration is enhanced by local cooling infusion (LCI) in ischemia

OBJECTIVE

The present study aimed to determine if hypothermia augments the neuroprotection conferred by MSC administration by providing a conducive micro-environment.

METHODS

Sprague-Dawley rats were subjected to 1.5 h middle cerebral artery occlusion (MCAO) followed by 6 or 24 h of reperfusion for molecular analyses, as well as 1, 14 and 28 days for brain infarction or functional outcomes. Rats were treated with either MSC (1 × 10⁵), LCI (cold saline, 0.6 ml/min, 5 min) or both. Brain damage was determined by Infarct volume and neurological deficits. Long-term functional outcomes were evaluated using foot-fault and Rota-rod testing. Human neural SHSY5Y cells were investigated in vitro using 2 h oxygen-glucose deprivation (OGD) followed by MSC with or without hypothermia (HT) (34 °C, 4 h). Mitochondrial transfer was assessed by confocal microscope, and cell damage was determined by cell viability, ATP, and ROS level. Protein levels of IL-1β, BAX, Bcl-2, VEGF and Miro1 were measured by Western blot following 6 h and 24 h of reperfusion and reoxygenation.

RESULTS

MSC, LCI, and LCI + MSC significantly reduced infarct volume and deficit scores. Combination therapy of LCI + MSC precipitated better long-term functional outcomes than monotherapy. Upregulation of Miro1 in the combination group increased mitochondrial transfer and lead to a greater increase in neuronal cell viability and ATP, as well as a decrease in ROS. Further, combination therapy significantly decreased expression of IL-1β and BAX while increasing Bcl-2 and VEGF expression.

CONCLUSION

Therapeutic hypothermia upregulated Miro1 and enhanced MSC mitochondrial transfer-mediated neuroprotection in ischemic stroke. Combination of LCI with MSC therapy may facilitate clinical translation of this approach.

Selective endovascular cooling for stroke entails brain-derived neurotrophic factor and splenic IL-10 modulation

Stroke poses a serious health and economic burden, and the lack of treatment options necessitates a viable therapy. Hypothermia represents a promising stroke therapy, yet side effects of full-body cooling, such as pneumonia, limit its clinical application. Selective endovascular cooling (SEC), via infusion of cold saline through the intraarterial artery, represents an attractive alternative by locally cooling the brain while preserving body temperature. However, the mechanisms underlying SEC are poorly understood. Brain-derived neurotrophic factor (BDNF) is a widely recognized promotor of neuroplasticity and biomarker of stroke outcomes, as well as its association with inflammation, such as IL-10. Stroke-induced neuroinflammation exacerbates damage and stems from peripheral organs, namely the spleen. The spleen has emerged as a therapeutic target for stroke, yet the effect of SEC on the splenic inflammatory response is unknown. Here, we aimed to elucidate the local and peripheral mechanisms driving SEC as a neuroprotective stroke therapy by examining brain BDNF and splenic IL-10 expression. Animals that received SEC prior to stroke displayed elevated brain BDNF expression ipsilaterally and contralaterally across the cortex, striatum, and hippocampus. SEC also upregulated splenic IL-10, suggesting alteration of the peripheral inflammatory response. The oxygen-glucose deprivation in vitro model of stroke further demonstrated that "cold" rat splenocytes protected rat primary neurons by upregulating BDNF and IL-10. Altogether these data support BDNF- and IL-10-based mechanisms underlying the neuroprotective potential of SEC therapy for stroke, and further advance the concept of exploiting the pathological link between brain and spleen as therapeutic targets.

Local endovascular infusion and hypothermia in stroke therapy: A systematic review

Ischemic stroke is a leading cause of death and disability worldwide, but there are no effective, widely applicable stroke therapies. Systemic hypothermia is an international mainstay of postcardiac arrest care, and the neuroprotective benefits of systemic hypothermia following cerebral ischemia have been proven in clinical trials, but logistical issues hinder clinical acceptance. As a novel solution to these logistical issues, the application of local endovascular infusion of cold saline directly to the infarct site using a microcatheter has been put forth. In small animal models, the procedure has shown incredible neuroprotective promise on the biochemical, structural, and functional levels, and preliminary trials in large animals and humans have been similarly encouraging. In addition, the procedure would be relatively cost-effective and widely applicable. The administration of local endovascular hypothermia in humans is relatively simple, as this is a normal part of endovascular intervention for neuroendovascular surgeons. Therefore, it is expected that this new therapy could easily be added to an angiography suite. However, the neuroprotective efficacy in humans has yet to be determined, which is an end goal of researchers in the field. Given the potentially massive benefits, ease of induction, and cost-effective nature, it is likely that local endovascular hypothermia will become an integral part of endovascular treatment following ischemic stroke. This review outlines relevant research, discusses neuroprotective mechanisms, and discusses possibilities for future directions.

Clinical potential of pre-reperfusion hypothermia in ischemic injury

The damage caused by ischemic stroke is mostly refractory to medical therapies and amounts to a substantial degree of mortality and morbidity in the world. The core tenet of treatment for acute ischemic stroke (AIS) is to save 'reversible' ischemic tissue (ischemic penumbra) as quickly as possible within a limited therapeutic time window. The neuroprotective effect of hypothermia has been proven previously in a large number of animal experiments and clinical trials. Some of these animal and human studies have shown that pre-reperfusion hypothermia can reduce myocardial infarction and improve clinical outcomes. However, to date, there is little research about hypothermia before reperfusion in the animal model and human study of AIS. This review will explore possible benefits of the application of pre-reperfusion hypothermia in the setting of AIS.

Inflammatory cytokines are involved in dihydrocapsaicin (DHC) and regional cooling infusion (RCI)-induced neuroprotection in ischemic rat

OBJECTIVE

The combination of pharmacological hypothermia - dihydrocapsaicin (DHC) and intra-arterial regional cooling infusions (RCI) was found to enhance the efficiency of hypothermia and efficacy of hypothermia-induced neuroprotection in acute ischemic stroke. The aim of this study was to explore whether the combination could induce a long-term neuroprotective effects, as well as the underlying mechanism.

METHODS

Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO) for 2 h using intraluminal hollow filament. The ischemic rats were randomized to receive pharmacological hypothermia by intraperitoneal (i.p.) injection of DHC, physical hypothermia by RCI of 6 ml cold saline (4 °C), the combination, and no treatment. Over a 21-day period, brain damage was determined by infarct volume with MRI, and neurological deficit with grid-walking and beam balance tests. Blood brain barrier (BBB) was assessed by Evans-Blue (EB) contents. Inflammatory cytokines were determined in peri-infarct area by antibody array and ELISA.

RESULTS

The combination of DHC and RCI reduced (p < 0.05) infarct volume and neurologic deficit after stroke. BBB leakage and pro-inflammatory cytokines (IFN-γ, IL-2, and TNF-α) were significantly decreased (p < 0.05) because of the combination, while protective cytokines (IL-4 and IL-10) were increased (p < 0.05) in the peri-infarct area.

CONCLUSIONS

The combination approach enhanced the efficacy of hypothermia-induced neuroprotection following ischemic stroke. Our findings provide a hint to translate the combination method from bench to bedside.

Selective brain hypothermia

Selective brain hypothermia is a powerful concept for neuroprotection that has been successfully investigated in a variety of animal models of global and focal ischemia. Its major advantages over systemic hypothermia include rapid induction of cooling, ability to achieve profound target brain temperatures, organ-selective cooling, and temperature control. Clinical systems and devices are available or are currently under development that utilize conductive (surface-cooling pads, closed-loop catheters), convective (transnasal coolant delivery), or mass and energy transport (cold intra-arterial infusion) methods to achieve and maintain selective brain hypothermia. The "ideal" brain-cooling system that is characterized by rapid cooling to profound hypothermia, its ability to maintain selective cooling over several days, and is noninvasive in nature, remains unrealistic. Instead, systems may be identified by their distinct advantages to meet a specific need in the care of a patient. This involves the consideration of the timing of ischemic injury (preischemic, intraischemic, postischemic), extent of ischemic damage (excitotoxicity, inflammation, necrosis, edema), and type and setting of therapeutic intervention (intensive care, interventional therapy, surgery). The successful translation of these systems into clinical practice will depend on smart engineering, safety and efficacy, and usability in current clinical work flow.

Hypothermia Used in Medical Applications for Brain and Spinal Cord Injury Patients

Despite more than 80 years of animal experiments and clinical practice, efficacy of hypothermia in improving treatment outcomes in patients suffering from cell and tissue damage caused by ischemia is still ongoing. This review will first describe the history of utilizing cooling in medical treatment, followed by chemical and biochemical mechanisms of cooling that can lead to neuroprotection often observed in animal studies and some clinical studies. The next sections will be focused on current cooling approaches/devices, as well as cooling parameters recommended by researchers and clinicians. Animal and clinical studies of implementing hypothermia to spinal cord and brain tissue injury patients are presented next. This section will review the latest outcomes of hypothermia in treating patients suffering from traumatic brain injury (TBI), spinal cord injury (SCI), stroke, cardiopulmonary surgery, and cardiac arrest, followed by a summary of available evidence regarding both demonstrated neuroprotection and potential risks of hypothermia. Contributions from bioengineers to the field of hypothermia in medical treatment will be discussed in the last section of this review. Overall, an accumulating body of clinical evidence along with several decades of animal research and mathematical simulations has documented that the efficacy of hypothermia is dependent on achieving a reduced temperature in the target tissue before or soon after the injury-precipitating event. Mild hypothermia with temperature reduction of several degrees Celsius is as effective as modest or deep hypothermia in providing therapeutic benefit without introducing collateral/systemic complications. It is widely demonstrated that the rewarming rate must be controlled to be lower than 0.5 °C/h to avoid mismatch between local blood perfusion and metabolism. In the past several decades, many different cooling methods and devices have been designed, tested, and used in medical treatments with mixed results. Accurately designing treatment protocols to achieve specific cooling outcomes requires collaboration among engineers, researchers, and clinicians. Although this problem is quite challenging, it presents a major opportunity for bioengineers to create methods and devices that quickly and safely produce hypothermia in targeted tissue regions without interfering with routine medical treatment.

Regional transarterial hypothermic infusion in combination with endovascular thrombectomy in acute ischaemic stroke with cerebral main arterial occlusion: protocol to investigate safety of the clinical trial

INTRODUCTION

Acute cerebral ischaemia with main cerebral artery occlusion requires treatment with intravenous tissue plasminogen activator administration and/or endovascular thrombectomy. However, some patients fail to recover even after recanalisation because of ischaemia/reperfusion (I/R) injury. We hypothesised that regional transarterial hypothermic infusion would be effective for patients with I/R injury. The aim of this study is to validate the safety of this procedure.

METHODS AND ANALYSIS

This is a clinical exploratory study to evaluate safety of regional transarterial hypothermic infusion in combination with endovascular thrombectomy. Patients with acute ischaemic stroke and a National Institutes of Health Stroke Scale (NIHSS) score of 5-29 who require endovascular thrombectomy are eligible for the study. When no improvement in NIHSS score after the recanalisation is achieved by thrombectomy, cold saline (15°C) will be administered through a microcatheter located in the ipsilateral internal carotid artery. The primary endpoints of this study are mortality and morbidity. The secondary endpoint is deleterious effects on clinical data such as symptoms, radiographic findings and physiological data. The primary and secondary endpoints will be accumulated as case series because this study will be conducted on a small sample of seven patients.

ETHICS AND DISSEMINATION

All protocols and the informed consent form comply with the Ethics Guideline for Clinical Research (Japanese Ministry of Health, Labour and Welfare). Ethics review committees at the Hokkaido University Hospital approved the study protocols. The results of the study will be disseminated at several research conferences and also contributed to peer-reviewed journals. The study will be implemented and reported in line with the SPIRIT statement.

TRIAL REGISTRATION NUMBER

UMIN Clinical Trails Registry (UMIN000018255); pre-results.

Dihydrocapsaicin (DHC) enhances the hypothermia-induced neuroprotection following ischemic stroke via PI3K/Akt regulation in rat

OBJECTIVE

Hypothermia has demonstrated neuroprotection following ischemia in preclinical studies while its clinical application is still very limited. The aim of this study was to explore whether combining local hypothermia in ischemic territory achieved by intra-arterial cold infusions (IACIs) with pharmacologically induced hypothermia enhances therapeutic outcomes, as well as the underlying mechanism.

METHODS

Sprague-Dawley rats were subjected to right middle cerebral artery occlusion (MCAO) for 2h using intraluminal hollow filament. The ischemic rats were randomized to receive: 1) pharmacological hypothermia by intraperitoneal (i.p.) injection of dihydrocapsaicin (DHC); 2) physical hypothermia by IACIs for 10min; or 3) the combined treatments. Extent of brain injury was determined by neurological deficit, infarct volume, and apoptotic cell death at 24h and/or 7d following reperfusion. ATP and ROS levels were measured. Expression of p-Akt, cleaved Caspase-3, pro-apoptotic (AIF, Bax) and anti-apoptotic proteins (Bcl-2, Bcl-xL) was evaluated at 24h. Finally, PI3K inhibitor was used to determine the effect of p-Akt.

RESULTS

DHC or IACIs each exhibited hypothermic effect and neuroprotection in rat MCAO models. The combination of pharmacological and physical approaches led to a faster and sustained reduction in brain temperatures and improved ischemia-induced injury than either alone (P<0.01). Furthermore, the combination treatment favorably increased the expression of anti-apoptotic proteins and decreased pro-apoptotic protein levels (P<0.01 or 0.05). This neuroprotective effect was largely blocked by p-Akt inhibition, indicating a potential role of Akt pathway in this mechanism (P<0.01 or 0.05).

CONCLUSIONS

The combination approach is able to enhance the efficiency of hypothermia and efficacy of hypothermia-induced neuroprotection following ischemic stroke. The findings here move us a step closer towards translating this long recognized TH from bench to bedside.

Transarterial regional hypothermia provides robust neuroprotection in a rat model of permanent middle cerebral artery occlusion with transient collateral hypoperfusion

The robust neuroprotective effects of transarterial regional hypothermia have been demonstrated in the typical transient middle cerebral artery occlusion (tMCAO) model, but have not yet been tested in other ischemic stroke models, even though clinical ischemic conditions are diverse. In order to clarify these effects in a different ischemic stroke model, we employed a rat model of permanent MCAO (pMCAO) with transient collateral hypoperfusion (tCHP), which was achieved by direct MCA ligation through craniotomy and 1-h bilateral common carotid artery occlusion at the beginning of pMCAO. The infusion of 20ml/kg of 4°C cold saline (CS) or 37°C warm saline (WS) into the ipsilateral internal carotid artery (ICA) was performed for 15min in intra- or post-tCHP. Neurological scores, infarct/edema volumes, and neuronal apoptosis and reactive gliosis were compared between the CS and WS groups and a non-infusion control group after 48h of reperfusion. Although brain temperatures were only reduced by 2-3°C for 15min, the CS group had significantly better neurological scores, smaller infarct/edema volumes, and less penumbral neuronal apoptosis and reactive gliosis than the control and WS groups. The post-tCHP CS group exhibited prominent neuroprotective effects, even though infarct volumes and neuronal apoptosis were reduced less than those in the intra-tCHP CS group. In conclusion, we demonstrated the neuroprotective effects of transarterial regional hypothermia in an ischemic model of pMCAO with tCHP. Even though MCAO is persistent, cold infusion via the ICA is neuroprotective for the penumbra, suggesting the wider therapeutic application of this therapy.

Assessment of Blood-Brain Barrier Permeability by Dynamic Contrast-Enhanced MRI in Transient Middle Cerebral Artery Occlusion Model after Localized Brain Cooling in Rats

Objective

The purpose of this study was to evaluate the effects of localized brain cooling on blood-brain barrier (BBB) permeability following transient middle cerebral artery occlusion (tMCAO) in rats, by using dynamic contrast-enhanced (DCE)-MRI.

Materials and Methods

Thirty rats were divided into 3 groups of 10 rats each: control group, localized cold-saline (20℃) infusion group, and localized warm-saline (37℃) infusion group. The left middle cerebral artery (MCA) was occluded for 1 hour in anesthetized rats, followed by 3 hours of reperfusion. In the localized saline infusion group, 6 mL of cold or warm saline was infused through the hollow filament for 10 minutes after MCA occlusion. DCE-MRI investigations were performed after 3 hours and 24 hours of reperfusion. Pharmacokinetic parameters of the extended Tofts-Kety model were calculated for each DCE-MRI. In addition, rotarod testing was performed before tMCAO, and on days 1-9 after tMCAO. Myeloperoxidase (MPO) immunohisto-chemistry was performed to identify infiltrating neutrophils associated with the inflammatory response in the rat brain.

Results

Permeability parameters showed no statistical significance between cold and warm saline infusion groups after 3-hour reperfusion 0.09 ± 0.01 min^-1 vs. 0.07 ± 0.02 min^-1, p = 0.661 for K^trans; 0.30 ± 0.05 min^-1 vs. 0.37 ± 0.11 min^-1, p = 0.394 for kep, respectively. Behavioral testing revealed no significant difference among the three groups. However, the percentage of MPO-positive cells in the cold-saline group was significantly lower than those in the control and warm-saline groups (p < 0.05).

Conclusion

Localized brain cooling (20℃) does not confer a benefit to inhibit the increase in BBB permeability that follows transient cerebral ischemia and reperfusion in an animal model, as compared with localized warm-saline (37℃) infusion group.

Temperature Control in Rodent Neuroprotection Studies: Methods and Challenges

Extensive animal research facilitated the clinical translation of therapeutic hypothermia for cardiac arrest in adults and hypoxic-ischemic injury in infants. Similarly, clinical interest in hypothermia for other brain injuries, such as stroke, has been greatly supported by positive findings in preclinical work. The reliability, validity, and utility of animal models, among many research practices (blinding, randomization, etc.), are key to successful clinical translation. Here, we review methods used to induce and maintain hypothermia in animal models. These include physical and pharmacological methods. We emphasize the advantages and limitations of each approach, and the importance of using clinically relevant cooling protocols and appropriate monitoring and reporting approaches. Moreover, we performed a literature survey of ischemic stroke studies published in 2015 to highlight the continuing risk of temperature confounds in neuroprotection studies. For example, many still do not accurately monitor and report temperature during surgery (23.5%), even though almost half of these studies (46.0%) use pharmaceutical agents that likely influence temperature. We hope this review stimulates awareness and discussion of the importance of temperature in neuroprotective studies.

Endovascular Hypothermia in Acute Ischemic Stroke: Pilot Study of Selective Intra-Arterial Cold Saline Infusion

BACKGROUND AND PURPOSE

We conducted a pilot feasibility and safety study of selective brain cooling with intra-arterial infusion of cold saline combined with endovascular reperfusion for acute ischemic stroke.

METHODS

Patients with large-vessel occlusion within 8 hours after symptom onset were enrolled. All patients received intra-arterial recanalization combined with infusion of cold isotonic saline (4°C) in the ischemic territory through the angiographic catheter.

RESULTS

Twenty-six patients underwent the procedure, which was technically successful in all. The temperature of ischemic cerebral tissue was decreased by at least 2°C during infusion of the cold solution, and systemic temperature was mildly reduced (maximum 0.3°C). No obvious complications related to intra-arterial hypothermia were observed.

CONCLUSIONS

Selective brain cooling by intra-arterial infusion of cold saline combined with endovascular recanalization therapy in acute ischemic stroke seems feasible and safe.

Endovascular Cooling Catheter for Selective Brain Hypothermia: An Animal Feasibility Study of Cooling Performance

BACKGROUND AND PURPOSE

Therapeutic hypothermia represents a promising neuroprotective treatment in acute ischemic stroke. Selective cerebral hypothermia applied early, prior to and during endovascular mechanical recanalization therapy, may be beneficial in the critical phase of reperfusion. We aimed to assess the feasibility of a new intracarotid cooling catheter in an animal model.

MATERIALS AND METHODS

Nine adult sheep were included. Temperature probes were introduced into the frontal and temporal brain cortices bilaterally. The cooling catheter system was introduced into a common carotid artery. Selective blood cooling was applied for 180 minutes. Systemic and local brain temperatures were measured during cooling and rewarming. Common carotid artery diameters and flow were measured angiographically and by Doppler sonography.

RESULTS

The common carotid artery diameter was between 6.7 and 7.3 mm. Common carotid artery blood flow velocities increased moderately during cooling and after catheter removal. Maximum cerebral cooling in the ipsilateral temporal cortex was -4.7°C (95% CI, -5.1 to -4.0°C). Ipsilateral brain temperatures dropped significantly faster and became lower compared with the contralateral cortex with maximum temperature difference of -1.3°C (95% CI, -1.5 to -1.0°C; P < .0001) and compared with systemic temperature (-1.4°C; 95% CI, -1.7 to -1.0°C; P < .0001).

CONCLUSIONS

Sheep proved a feasible animal model for the intracarotid cooling catheter. Fast induction of selective mild hypothermia was achieved within the cooled cerebral hemisphere, with stable temperature gradients in the contralateral brain and systemic blood. Further studies are required to demonstrate any therapeutic benefit of selective cerebral cooling in a stroke model.

Therapeutic hypothermia for stroke: Where to go?

Ischemic stroke is a major cause of death and long-term disability worldwide. Thrombolysis with recombinant tissue plasminogen activator is the only proven and effective treatment for acute ischemic stroke; however, therapeutic hypothermia is increasingly recognized as having a tissue-protective function and positively influencing neurological outcome, especially in cases of ischemia caused by cardiac arrest or hypoxic-ischemic encephalopathy in newborns. Yet, many aspects of hypothermia as a treatment for ischemic stroke remain unknown. Large-scale studies examining the effects of hypothermia on stroke are currently underway. This review discusses the mechanisms underlying the effect of hypothermia, as well as trends in hypothermia induction methods, methods for achieving optimal protection, side effects, and therapeutic strategies combining hypothermia with other neuroprotective treatments. Finally, outstanding issues that must be addressed before hypothermia treatment is implemented at a clinical level are also presented.

The effect of a microcatheter-based selective intra-arterial hypothermia on hemodynamic changes following transient cerebral ischemia

OBJECTIVES

We investigated the effect of a microcatheter-based selectively induced intra-arterial hypothermia on hemodynamic changes following transient cerebral ischemia in rats.

METHODS

Stroke was induced in male Sprague-Dawley rats by a two-hour middle cerebral artery occlusion (MCAO) using a microcatheter. After the two-hour MCAO, 0·9% cold saline (0°C) was selectively infused through a microcatheter. Cerebral blood flow (CBF) in the ischemic brain region was continuously monitored by Laser-Doppler flowmetry (LDF) during the procedure. Following ischemia/reperfusion, serial functional neurologic testing was performed, and cerebral infarct volume was evaluated after 48 hours.

RESULTS

The local cold saline infusion, via a microcatheter, achieved a rapid induction of brain hypothermia (cerebral cortex from 37·1 ± 0·3 to 30·7 ± 0·4°C; striatum from 37·5 ± 0·3 to 30·9 ± 0·5°C). When compared to the non-treatment group, the local cold saline infusion treatment reduced both post-ischemic hyperperfusion (about 40%, P < 0·01) and delayed post-ischemic hypoperfusion (P < 0·01), improved functional neurological testing (P < 0·01), and reduced both cerebral infarction volume (40·6 ± 5·3 vs. 61·7 ± 8·6%, P < 0·01) and cerebral edema (7·8 ± 2·6 vs.15·4 ± 3·2%, P < 0·01).

CONCLUSION

Cold saline, when infused directly into the ischemic brain region, can confer robust neuroprotection by reducing immediate post-ischemic hyperperfusion and delayed post-ischemic hypoperfusion.

Better Glasgow outcome score, cerebral perfusion pressure and focal brain oxygenation in severely traumatized brain following direct regional brain hypothermia therapy: A prospective randomized study

BACKGROUND

Induced hypothermia for treatment of traumatic brain injury is controversial. Since many pathways involved in the pathophysiology of secondary brain injury are temperature dependent, regional brain hypothermia is thought capable to mitigate those processes. The objectives of this study are to assess the therapeutic effects and complications of regional brain cooling in severe head injury with Glasgow coma scale (GCS) 6-7.

MATERIALS AND METHODS

A prospective randomized controlled pilot study involving patients with severe traumatic brain injury with GCS 6 and 7 who required decompressive craniectomy. Patients were randomized into two groups: Cooling and no cooling. For the cooling group, analysis was made by dividing the group into mild and deep cooling. Brain was cooled by irrigating the brain continuously with cold Hartmann solution for 24-48 h. Main outcome assessments were a dichotomized Glasgow outcome score (GOS) at 6 months posttrauma.

RESULTS

A total of 32 patients were recruited. The cooling-treated patients did better than no cooling. There were 63.2% of patients in cooling group attained good GOS at 6 months compared to only 15.4% in noncooling group (P = 0.007). Interestingly, the analysis at 6 months post-trauma disclosed mild-cooling-treated patients did better than no cooling (70% vs. 15.4% attained good GOS, P = 0.013) and apparently, the deep-cooling-treated patients failed to be better than either no cooling (P = 0.074) or mild cooling group (P = 0.650).

CONCLUSION

Data from this pilot study imply direct regional brain hypothermia appears safe, feasible and maybe beneficial in treating severely head-injured patients.

In cold blood: intraarteral cold infusions for selective brain cooling in stroke

Hypothermia is a promising therapeutic option for stroke patients and an established neuroprotective treatment for global cerebral ischemia after cardiac arrest. While whole body cooling is a feasible approach in intubated and sedated patients, its application in awake stroke patients is limited by severe side effects: Strong shivering rewarms the body and potentially worsens ischemic conditions because of increased O2 consumption. Drugs used for shivering control frequently cause sedation that increases the risk of aspiration and pneumonia. Selective brain cooling by intraarterial cold infusions (IACIs) has been proposed as an alternative strategy for patients suffering from acute ischemic stroke. Preclinical studies and early clinical experience indicate that IACI induce a highly selective brain temperature decrease within minutes and reach targeted hypothermia 10 to 30 times faster than conventional cooling methods. At the same time, body core temperature remains largely unaffected, thus systemic side effects are potentially diminished. This review critically discusses the limitations and side effects of current cooling techniques for neuroprotection from ischemic brain damage and summarizes the available evidence regarding advantages and potential risks of IACI.

Interrupted intracarotid artery cold saline infusion as an alternative method for neuroprotection after ischemic stroke

Object

Intracarotid artery cold saline infusion (ICSI) is an effective method for protecting brain tissue, but its use is limited because of undesirable secondary effects, such as severe decreases in hematocrit levels, as well as its relatively brief duration. In this study, the authors describe and investigate the effects of a novel ICSI pattern (interrupted ICSI) relative to the traditional method (uninterrupted ICSI).

Methods

Ischemic strokes were induced in 85 male Sprague-Dawley rats by occluding the middle cerebral artery for 3 hours using an intraluminal filament. Uninterrupted infusion groups received an infusion at 15 ml/hour for 30 minutes continuously. The same infusion speed was used in the interrupted infusion groups, but the whole duration was divided into trisections, and there was a 20-minute interval without infusion between sections. Forty-eight hours after reperfusion, H & E and silver nitrate staining were utilized for morphological assessment. Infarct sizes and brain water contents were determined using H & E staining and the dry-wet weight method, respectively. Levels of neuron-specific enolase (NSE), S100β protein, and matrix metalloproteinase 9 (MMP-9) in the serum were determined using enzyme-linked immunosorbent assay. Neurological deficits were also evaluated.

Results

Histology showed that interrupted ICSI did not affect neurons or fibers in rat brains, which suggests that this method is safe for brain tissues with ischemia. The duration of hypothermia induced by interrupted ICSI was longer than that induced via the traditional method, and the decrease in hematocrit levels was less pronounced. There were no differences in infarct size or brain water content between uninterrupted and interrupted ICSI groups, but neuron-specific enolase and matrix metalloproteinase 9 serum levels were more reduced after interrupted ICSI than after the traditional method.

Conclusions

Interrupted ICSI is a safe method. Compared with traditional ICSI, the interrupted method has a longer duration of hypothermia and less effect on hematocrit and offers more potentially improved neuroprotection, thereby making it more attractive as an infusion technique in the clinic.