The effects of head-cooling on brain function during passive hyperthermia: an fMRI study.

PURPOSE: To investigate the effect of head-cooling on resting-state spontaneous brain activity during passive hyperthermia. METHODS: An environmental heat exposure was simulated on 16 healthy men under a normal control condition (NC) at 25 °C and two hot conditions at 50 °C with hyperthermia with head-cooling condition (HHC) and without hyperthermia condition (HOT) keeping the head cool, respectively. Resting-state functional MRI (fMRI) data were acquired under each condition and the values of amplitude low frequency fluctuations (ALFF) and z functional connectivity (zFC) were computed to examine regional activity and functional integration, respectively. Pearson's correlation analysis between the ALFF value and subjective sensations scores were performed. RESULTS: Brain regions with significant ALFF differences among the three conditions were found primarily in the right medial prefrontal cortex/anterior cingulate cortex (MPFC/ACC), bilateral posterior cingulate cortex/precuneus (PCC/PCu), and right fusiform gyrus. Compared to the NC or HOT condition, the HHC condition exhibited significantly increased ALFF in the bilateral PCC/PCu and decreased ALFF in the right fusiform gyrus. However, ALFF of the right MPFC/ACC showed no significant difference between the NC and HHC conditions. Positive FC between the right MPFC/ACC and bilateral PCC/PCu was significantly increased in HHC condition with respect to HOT condition. Negative FC between the right fusiform gyrus and the right MPFC/ACC, bilateral PCC/PCu was observed with a decreasing trend from the HHC condition to the HOT condition. Moreover, head-cooling also improved thermal comfort during passive hyperthermia. CONCLUSIONS: Head-cooling could substantially reduce the negative effect of hyperthermia on human brain activity as well as thermal sensation.

Yawning reduces facial temperature in the high-yawning subline of Sprague-Dawley rats.

BACKGROUND: Yawning is a stereotyped behavior that enhances blood flow to the skull, and the resulting counterflow has been hypothesized as a mechanism for brain cooling. Studies have shown that yawns are strongly associated with physiological and pathological conditions that increase brain temperature, and that they are followed by equivalent decreases in brain temperature. However, measured reductions in cranial or facial temperatures following yawning have yet to be reported, to our knowledge. To accomplish this, we used a subline of Sprague-Dawley rats that yawn at a much greater rate (20 yawns/h) than do outbred Sprague-Dawley rats (2 yawns/h). RESULTS: Using an infrared camera, we effectively evaluated thermal changes in the cornea and concha of these rats before, during, and after yawns. The maximum temperature in both regions significantly decreased 10 s following yawns (concha: -0.3 °C, cornea: -0.4 °C), with a return to basal temperatures after 20 s. CONCLUSIONS: This study is the first clear demonstration of yawning-induced thermal cooling on the surface of the face, providing convergent evidence that this behavior plays a functional role in thermoregulation. As other studies have demonstrated that yawning is capable of reducing cortical brain temperature, our current data support the idea that yawning functions as a thermoregulator, affecting all structures within the head.

Comparison of selective head cooling versus whole-body cooling.

BACKGROUND: This study compared selective head cooling (SHC) and whole-body cooling (WBC) in newborns with hypoxic-ischemic encephalopathy (HIE). METHODS: We conducted a prospective randomized small-scale pilot study in newborns with HIE, born after >35 weeks of gestation. The patients were randomly assigned to receive SHC or WBC. RESULTS: The SHC group consisted of 17 patients, and the WBC group, 12 patients. There was no significant difference in adverse effects related to cooling therapy between the two groups. During the 12 month study period, seven patients in the SHC group and four in the WBC group died, but the difference was not significant (P = 0.667). Among the patients alive at 12 months after treatment, six in the SHC group and four in the WBC group had severe disabilities; the difference was not significant (P = 0.671). When the composite outcome of death or severe disability was evaluated, the difference between the SHC group (77%, n = 13) and the WBC group (67%, n = 8) was not significant (P = 0.562). Moreover, the number of survivors without disability at 12 months after treatment did not differ significantly between the SHC group (n = 3) and the WBC group (n = 4; P = 0.614). CONCLUSIONS: There were no significant differences in adverse effects, 12 month neuromotor development, or mortality rate between SHC and WBC in newborns with HIE, born after >35 weeks of gestation.

Effects of intraoperative external head cooling on short-term cognitive function in patients after coronary artery bypass graft surgery.

The aim of study was to assess the effects of an intraoperative external head-cooling technique on cognitive dysfunction in the early postoperative period (at the 10th day) in patients after coronary artery bypass graft (CABG) surgery. Patients in Group H (n=25) were cooled with CPB and the intraoperative, external head-cooling technique, patients in Group C (n=25) were cooled only with cardiopulmonary bypass (CPB) to achieve mild hypothermia (33 - 34 °C). Cognitive function was analyzed before the operation and after the surgery using the Mini Mental State Examination (MMSE), the Modified Visual Reproduction Test from the Wechsler Memory Scale, Trail Making (A/B), WAIS--Digit Span (WDS) and WAIS Digit Symbol Substitution Test (WDSST). The incidence of cognitive impairment at the 10th day after the surgery was 36% (n=9) in Group H and 64% (n=16) in Group C (p=0.048). The temperature during the aortic cross-clamp period was associated with a lower rate of cognitive dysfunction (p=0.05, r(2)=0.09). The intraoperative, external head-cooling technique during the aortic cross-clamp period has a neuroprotective effect and leads to less short-term cognitive function impairment after CABG surgery.

Is Selective Head Cooling Combined with Whole-Body Cooling the Most Effective Hypothermia Method for Neonatal Hypoxic-Ischemic Encephalopathy?

This study aimed to compare combined hypothermia (CH) to the 2 classical therapeutic hypothermia (TH) methods selective head cooling (SHC) and whole-body cooling (WBC). This retrospective cohort study included neonates who underwent CH, SHC, and WBC between 2012 and 2020. Mean rectal temperature was maintained at 33.5 ± 0.5°C by cooling the head and the body in the CH group, at 34.5 ± 0.5°C by cooling the head in the SHC group, and at 33.5 ± 0.5°C by cooling the body in the WBC group. The groups were compared in terms of side effects, magnetic resonance imaging (MRI) scores, and status at discharge. The study included 60 neonates in the CH group, 112 in the WBC group, and 27 in the SHC group. There was no significant difference in side effects between the groups (p > 0.05). There was no significant difference in brain MRI scores between the groups (p > 0.05); however, gray matter, white matter, and total MRI scores in the CH group were lower than in the WBC group. Duration of hospitalization was shorter in the CH group than in the other two groups (p = 0.022). CH was not associated with more side effects than the two classical TH methods. In addition, some of these findings suggest that CH might result in better clinical outcome than the two classical TH methods.

Selective head cooling in the acute phase of concussive injury: a neuroimaging study.

Introduction: Neurovascular decoupling is a common consequence after brain injuries like sports-related concussion. Failure to appropriately match cerebral blood flow (CBF) with increases in metabolic demands of the brain can lead to alterations in neurological function and symptom presentation. Therapeutic hypothermia has been used in medicine for neuroprotection and has been shown to improve outcome. This study aimed to examine the real time effect of selective head cooling on healthy controls and concussed athletes via magnetic resonance spectroscopy (MRS) and arterial spin labeling (ASL) measures. Methods: 24 participants (12 controls; 12 concussed) underwent study procedures including the Post-Concussion Symptom Severity (PCSS) Rating Form and an MRI cooling protocol (pre-cooling (T1 MPRAGE, ASL, single volume spectroscopy (SVS)); during cooling (ASL, SVS)). Results: Results showed general decreases in brain temperature as a function of time for both groups. Repeated measures ANOVA showed a significant main effect of time (F = 7.94, p < 0.001) and group (F = 22.21, p < 0.001) on temperature, but no significant interaction of group and time (F = 1.36, p = 0.237). CBF assessed via ASL was non-significantly lower in concussed individuals at pre-cooling and generalized linear mixed model analyses demonstrated a significant main effect of time for the occipital left ROI (F = 11.29, p = 0.002) and occipital right ROI (F = 13.39, p = 0.001). There was no relationship between any MRI metric and PCSS symptom burden. Discussion: These findings suggest the feasibility of MRS thermometry to monitor alterations of brain temperature in concussed athletes and that metabolic responses in response to cooling after concussion may differ from controls.

The Term Newborn: Evaluation for Hypoxic-Ischemic Encephalopathy.

Neonatal encephalopathy due to perinatal hypoxia-ischemia (hypoxic-ischemic encephalopathy [HIE]) occurs at a rate of 1 to 3 per 1000 live births. Therapeutic hypothermia is the standard of care and the only currently available therapy to reduce the risk of death or disability in newborns with moderate to severe HIE. Hypothermia therapy needs to be initiated within 6 hours after birth in order to provide the best chance for neuroprotection. All pediatricians and delivery room attendants should be trained to recognize encephalopathy and understand the eligibility criteria for treatment. The modified Sarnat examination is the most frequently used tool to assess the degree of encephalopathy and has six categories, each of which can have mild, moderate, severe abnormalities. Apart from historical and biochemical criteria, a neonate must have 3 of 6 categories scored in the moderate or severe range in order to qualify for hypothermia as was done in the randomized trials. Whether an infant qualifies or there is concern that an infant might have HIE, transfer to a center that can perform treatment should be initiated immediately. Hypothermia significantly reduces the risk of death or moderate to severe impairments at 2 years and at school age. On average, only 7 neonates need to be treated for one neonate to benefit. Although easy in concept, implementation of hypothermia does require expertise and should be carried out under the guidance of a neonatologist. If infants are passively cooled prior to transport, core temperature needs to be closely monitored with a target of 33.5°C ± 0.5°C. Maintenance of homeostasis is important in order to prevent conditions that may result in additional brain injury. Seizures are common in neonates with HIE, but electrographic seizures are rare in the first few hours after birth if the insult occurred during labor and delivery. Prophylactic antiepileptic drugs should not be administered. Brain monitoring in the form of electroencephalogram (EEG) and or amplitude-integrated EEG should be implemented as soon as possible to help with prognosis and to accurately diagnose seizures.

Therapeutic hypothermia in asphyxiated newborns: selective head cooling vs. whole body cooling - comparison of short term outcomes.

OBJECTIVES: Therapeutic hypothermia TH became broadly used in the management of the asphyxiated newborns. Although two cooling methods are used, so far the superiority of none of them has been established. The purpose of the study is to compare two cooling methods: selective head cooling (SHC) and whole body cooling (WBC) MATERIAL AND METHODS: We conducted a prospective observational study in newborns with HIE. The patients received one of methods: SHC or WBC. The eligibility criteria were similar to previous studies. Stability of cardio-respiratory parameters and short term outcomes were analyzed. RESULTS: 78 neonates with hypoxic-ischemic encephalopathy due to perinatal asphyxia were involved in this study. The SHC group consisted of 51 newborns, the WBC group consisted of 27 patients. Both study groups had similar baseline characteristics and condition at birth. There were no significant differences in hospital course, neurological status and adverse effects associated with cooling procedure between groups. Analyzing the rate of thrombocytopenia and the number of transfusions of blood components no statistically significant differences were found between the groups. CONCLUSIONS: Results of our study indicate that two compared methods of TH despite varied target core temperature ranges do not differ significantly according to clinical course and risk of adverse events. Further observations are conducted and we look forward to the results of the long neurodevelopmental care.

Body Temperature, Heart Rate, and Short-Term Outcome of Cooled Infants.

Therapeutic hypothermia following neonatal encephalopathy is neuroprotective. However, approximately one in two cooled infants still die or develop permanent neurological impairments. Further understanding of variables associated with the effectiveness of cooling is important to improve the therapeutic regimen. To identify clinical factors associated with short-term outcomes of cooled infants, clinical data of 509 cooled infants registered to the Baby Cooling Registry of Japan between 2012 and 2014 were evaluated. Independent variables of death during the initial hospitalization and survival discharge from the cooling hospital at ≤28 days of life were assessed. Death was associated with higher Thompson scores at admission (p < 0.001); higher heart rates after 3-72 hours of cooling (p < 0.001); and higher body temperature after 24 hours of cooling (p = 0.002). Survival discharge was associated with higher 10 minutes Apgar scores (p < 0.001); higher blood pH and base excess (both p < 0.001); lower Thompson scores (at admission and after 24 hours of cooling; both p < 0.001); lower heart rates at initiating cooling (p = 0.003) and after 24 hours of cooling (p < 0.001) and lower average values after 3-72 hours of cooling (p < 0.001); higher body temperature at admission (p < 0.001); and lower body temperature after 24 hours and lower mean values after 3-72 hours of cooling (both p < 0.001). Survival discharge was best explained by higher blood pH (p < 0.05), higher body temperature at admission (p < 0.01), and lower body temperature and heart rate after 24 hours of cooling (p < 0.01 and <0.001, respectively). Lower heart rate, higher body temperature at admission, and lower body temperature during cooling were associated with favorable short-term outcomes.

Influence of external head cooling on the head, core body and blood temperatures using 3D whole-body model.

PURPOSE: The purpose of this study is to evaluate the impact of external head cooling on alleviating the heat stress in the human body by analyzing the temperatures of the core body (Tc), blood (Tblood) and head (Th) during exercise conditions using 3D whole body model. DESIGN/METHODOLOGY/APPROACH: Computational study is conducted to comprehend the influence of external head cooling on Tc, Tblood and Th. The Pennes bioheat and energy balance equations formulated for the whole-body model are solved concurrently to obtain Tc, Tblood and Th for external head cooling values from 33 to 233 W/m2 Increased external head cooling of 404 W/m2 is used to compare the numerical and experimental Th data. FINDINGS: Significant reductions of 0.21°C and 0.38°C are observed in Th with external head cooling of 233 and 404 W/m2, respectively. However, for external head cooling of 233 W/m2, lesser reductions of 0.03°C and 0.06°C are found in Tc and Tblood, respectively. Computational results for external head cooling of 404 W/m2 show a difference of 15 per cent in Th compared to experimental values from literature. ORIGINALITY/VALUE: The development of stress because of heat generated within human body is major concern for athletes exercising at high intensities. This study provides an insight into the effectiveness of external head cooling in regulating the head and body temperatures during exercise conditions.

Comparison of selective head cooling therapy and whole body cooling therapy in newborns with hypoxic ischemic encephalopathy: short term results.

AIM: In this study, it was aimed to investigate which method was superior by applying selective head cooling or whole body cooling therapy in newborns diagnosed with moderate or severe hypoxic ischemic encephalopathy. MATERIALS AND METHOD: Newborns above the 35th gestational age diagnosed with moderate or severe hypoxic ischemic encephalopathy were included in the study and selective head cooling or whole body cooling therapy was performed randomly. The newborns who were treated by both methods were compared in terms of adverse effects in the early stage and in terms of short-term results. Ethics committee approval was obtained for the study (06.01.2010/35). RESULTS: Fifty three babies diagnosed with hypoxic ischemic encephalopathy were studied. Selective head cooling was applied to 17 babies and whole body cooling was applied to 12 babies. There was no significant difference in terms of adverse effects related to cooling therapy between the two groups. When the short-term results were examined, it was found that the hospitalization time was 34 (7-65) days in the selective head cooling group and 18 (7-57) days in the whole body cooling group and there was no significant difference between the two groups (p=0.097). Four patients in the selective head cooling group and two patients in the whole body cooling group were discharged with tracheostomy because of the need for prolonged mechanical ventilation and there was no difference between the groups in terms of discharge with tracheostomy (p=0.528). Five patients in the selective head cooling group and three patients in the whole body cooling group were discharged with a gastrostomy tube because they could not be fed orally and there was no difference between the groups in terms of discharge with a gastrostomy tube (p=0.586). One patient who was applied selective head cooling and one patient who was applied whole body cooling died during hospitalization and there was no difference between the groups in terms of mortality (p=0.665). CONCLUSIONS: There is no difference between the methods of selective head cooling and whole body cooling in terms of adverse effects and short-term results.

Protective head-cooling during cardiac arrest and cardiopulmonary resuscitation: the original animal studies.

Prolonged standard cardiopulmonary resuscitation (CPR) does not reliably sustain brain viability during cardiac arrest. Pre-hospital adjuncts to standard CPR are needed in order to improve outcomes. A preliminary dog study demonstrated that surface cooling of the head during arrest and CPR can achieve protective levels of brain hypothermia (30°C) within 10 minutes. We hypothesized that protective head-cooling during cardiac arrest and CPR improves neurological outcomes. Twelve dogs under light ketamine-halothane-nitrous oxide anesthesia were arrested by transthoracic fibrillation. The treated group consisted of six dogs whose shaven heads were moistened with saline and packed in ice immediately after confirmation of ventricular fibrillation. Six control dogs remained at room temperature. All 12 dogs were subjected to four minutes of ventricular fibrillation and 20 minutes of standard CPR. Spontaneous circulation was restored with drugs and countershocks. Intensive care was provided for five hours post-arrest and the animals were observed for 24 hours. In both groups, five of the six dogs had spontaneous circulation restored. After three hours, mean neurological deficit was significantly lower in the treated group (P=0.016, with head-cooled dogs averaging 37% and the normothermic dogs 62%). Two of the six head-cooled dogs survived 24 hours with neurological deficits of 9% and 0%, respectively. None of the control group dogs survived 24 hours. We concluded that head-cooling attenuates brain injury during cardiac arrest with prolonged CPR. We review the literature related to the use of hypothermia following cardiac arrest and discuss some promising approaches for the pre-hospital setting.