Esophageal Cooling Device Versus Other Temperature Modulation Devices for Therapeutic Normothermia in Subarachnoid and Intracranial Hemorrhage

Mechanisms of action behind the protective effects of proactive esophageal cooling during radiofrequency catheter ablation in the left atrium

Proactive esophageal cooling for the purpose of reducing the likelihood of ablation-related esophageal injury resulting from radiofrequency (RF) cardiac ablation procedures is increasingly being used and has been Food and Drug Administration cleared as a protective strategy during left atrial RF ablation for the treatment of atrial fibrillation. In this review, we examine the evidence supporting the use of proactive esophageal cooling and the potential mechanisms of action that reduce the likelihood of atrioesophageal fistula (AEF) formation. Although the pathophysiology behind AEF formation after thermal injury from RF ablation is not well studied, a robust literature on fistula formation in other conditions (eg, Crohn disease, cancer, and trauma) exists and the relationship to AEF formation is investigated in this review. Likewise, we examine the abundant data in the surgical literature on burn and thermal injury progression as well as the acute and chronic mitigating effects of cooling. We discuss the relationship of these data and maladaptive healing mechanisms to the well-recognized postablation pathophysiological effects after RF ablation. Finally, we review additional important considerations such as patient selection, clinical workflow, and implementation strategies for proactive esophageal cooling.

Minimizing Shivering During Targeted Normothermia: Comparison Between Novel Transnasal and Surface Temperature-Modulating Devices

BACKGROUND

Shivering is a common adverse effect of achieving and maintaining normothermia in neurocritical care patients. We compared the burden of shivering and shivering-related interventions between a novel transnasal temperature-modulating device (tnTMD) and surface cooling temperature-modulating devices (sTMDs) during the first 24 h of targeted normothermia in mechanically ventilated febrile neurocritical care patients.

METHODS

This is a case-control study controlling for factors that impact shiver burden: age, sex, body surface area. All patients underwent transnasal cooling (CoolStat, KeyTech, Inc.) as part of an ongoing multicenter clinical trial (NCT03360656). Patients undergoing treatment with sTMDs were selected from consecutively treated patients during the same time period. Data collected included the following: core body temperature (every 2 h), bedside shivering assessment scale (BSAS) score (every 2 h), and administration of antishivering medication for a BSAS score > 1. Time to normothermia (≤ 37.5 °C), as well as temperature burden > 37.5 °C (°C × h), were compared between groups using Student's t-test for mean differences. The proportion of patients requiring interventions, as well as the number of interventions per patient, was compared using the χ2 test. Significance was determined based on a p value < 0.05.

RESULTS

There were 10 tnTMD patients and 30 sTMD patients included in the analysis (mean age: 62 ± 4, 30% women, body surface area = 1.97 ± 0.25). There were no differences between groups in temperature at cooling initiation (tnTMD: 38.5 ± 0.2 °C vs. sTMD: 38.7 ± 0.5 °C, p = 0.3), time to ≤ 37.5 °C (tnTMD: 1.8 ± 1.5 h vs. sTMD: 2.9 ± 1.4 h, p = 0.1), or temperature burden > 37.5 (tnTMD: - 0.4 ± 1.13 °C × h vs. sTMD median [IQR]: - 0.57 ± 0.58 °C × h, p = 0.67). The number of tnTMD patients who received pharmacologic shivering interventions was lower than the number of controls (20 vs. 67%, p = 0.01). tnTMD patients also had fewer shivering interventions per patient (0 [range: 0-3] vs. 4 [range: 0-23], p < 0.001).

CONCLUSIONS

A transnasal cooling approach achieved similar time to normothermia and temperature burden with less shivering than surface cooling. This approach may be a feasible option to consider for mechanically ventilated febrile neurocritical care patients.

Systemic Inflammation after Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is one of the most severe neurological disorders, with a high mortality rate and severe disabling functional sequelae. Systemic inflammation following hemorrhagic stroke may play an important role in mediating intracranial and extracranial tissue damage. Previous studies showed that various systemic inflammatory biomarkers might be useful in predicting clinical outcomes. Anti-inflammatory treatment might be a promising therapeutic approach for improving the prognosis of patients with aSAH. This review summarizes the complicated interactions between the nervous system and the immune system.

Perioperative targeted temperature management of severely burned patients by means of an oesophageal temperature probe

BACKGROUND

Hypothermia in severely burned patients is associated with a significant increase in morbidity and mortality. The use of an oesophageal heat exchanger tube (EHT) can improve perioperative body temperatures in severely burned patients. The aim of this study was to investigate the intraoperative warming effect of oesophageal heat transfer in severe burn patients.

METHODS

Single-centre retrospective study performed at the Burns Centre of the University Hospital Zurich. Between January 2020 and May 2021 perioperative temperature management with EHT was explored in burned patients with a total body surface area (TBSA) larger than 30%. Data from patients, who received perioperative temperature management by EHT, were compared to data from the same patients during interventions performed under standard temperature management matching for length and type of intervention.

RESULTS

A total of 30 interventions (15 with and 15 without EHT) in 10 patients were analysed. Patient were 38 [26-48] years of age, presented with severe burns covering a median of 50 [42-64] % TBSA and were characterized by an ABSI of 10 [8-12] points. When receiving EHT management patients experienced warming at 0.07 °C per minute (4.2 °C/h) compared to a temperature loss of - 0.03 °C per minute (1.8 °C/h) when only receiving standard temperature management (p < 0.0001). No adverse or serious adverse events were reported.

CONCLUSION

The use of an oesophageal heat transfer device was effective and safe in providing perioperative warming to severely burned patients when compared to a standard temperature management protocol. By employing an EHT as primary temperature management device perioperative hypothermia in severely burned patients can possibly be averted, potentially leading to reduced hypothermia-associated complications.

Computational modeling of targeted temperature management in post-cardiac arrest patients

Our core body temperature is held around [Formula: see text]C by an effective internal thermoregulatory system. However, various clinical scenarios have a more favorable outcome under external temperature regulation. Therapeutic hypothermia, for example, was found beneficial for the outcome of resuscitated cardiac arrest patients due to its protection against cerebral ischemia. Nonetheless, practice shows that outcomes of targeted temperature management vary considerably in dependence on individual tissue damage levels and differences in therapeutic strategies and protocols. Here, we address these differences in detail by means of computational modeling. We develop a multi-segment and multi-node thermoregulatory model that takes into account details related to specific post-cardiac arrest-related conditions, such as thermal imbalances due to sedation and anesthesia, increased metabolic rates induced by inflammatory processes, and various external cooling techniques. In our simulations, we track the evolution of the body temperature in patients subjected to post-resuscitation care, with particular emphasis on temperature regulation via an esophageal heat transfer device, on the examination of the alternative gastric cooling with ice slurry, and on how anesthesia and the level of inflammatory response influence thermal behavior. Our research provides a better understanding of the heat transfer processes and therapies used in post-cardiac arrest patients.

Core warming of coronavirus disease 2019 (COVID-19) patients undergoing mechanical ventilation-A protocol for a randomized controlled pilot study

BACKGROUND

Coronavirus disease 2019 (COVID-19), caused by the virus SARS-CoV-2, is spreading rapidly across the globe, with little proven effective therapy. Fever is seen in most cases of COVID-19, at least at the initial stages of illness. Although fever is typically treated (with antipyretics or directly with ice or other mechanical means), increasing data suggest that fever is a protective adaptive response that facilitates recovery from infectious illness.

OBJECTIVE

To describe a randomized controlled pilot study of core warming patients with COVID-19 undergoing mechanical ventilation.

METHODS

This prospective single-site randomized controlled pilot study will enroll 20 patients undergoing mechanical ventilation for respiratory failure due to COVID-19. Patients will be randomized 1:1 to standard-of-care or to receive core warming via an esophageal heat exchanger commonly utilized in critical care and surgical patients. The primary outcome is patient viral load measured by lower respiratory tract sample. Secondary outcomes include severity of acute respiratory distress syndrome (as measured by PaO2/FiO2 ratio) 24, 48, and 72 hours after initiation of treatment, hospital and intensive care unit length of stay, duration of mechanical ventilation, and 30-day mortality.

RESULTS

Resulting data will provide effect size estimates to guide a definitive multi-center randomized clinical trial. ClinicalTrials.gov registration number: NCT04426344.

CONCLUSIONS

With growing data to support clinical benefits of elevated temperature in infectious illness, this study will provide data to guide further understanding of the role of active temperature management in COVID-19 treatment and provide effect size estimates to power larger studies.

Thermoregulation: A journey from physiology to computational models and the intensive care unit

Thermoregulation plays a vital role in homeostasis. Many species of animals as well as humans have evolved various physiological mechanisms for body temperature control, which are characteristically flexible and enable a fine-tuned spatial and temporal regulation of body temperature in different environmental conditions and circumstances. Human beings normally maintain a core body temperature at around 37°C, and maintenance of this relatively high temperature is critical for survival. Therefore, principles of thermoregulatory control have also important clinical implications. Infections can cause the body temperature to rise internally and several diseases can cause a dysfunction of thermoregulatory mechanisms. Moreover, the utilization of thermotherapies in treating various diseases has been known for thousands of years with a recent resurgence of interest. An increasing amount of research suggests that targeted temperature management is of paramount importance to patient outcomes in certain clinical scenarios. We provide a concise summary of the basic concepts of thermoregulation. Emphasis is given to the principles of thermoregulation in humans in basic pathological states and to targeted temperature management strategies in the clinical environment, with special attention on therapeutic hypothermia in postcardiac arrest patients. Finally, the discussion is focused on the potential offered by computational thermophysiological models for predicting thermal responses of patients in various clinical circumstances, for proposing new perspectives in the design of novel thermal therapies, and to optimize targeted temperature management strategies. This article is categorized under: Cardiovascular Diseases > Cardiovascular Diseases>Computational Models Cardiovascular Diseases > Cardiovascular Diseases>Environmental Factors Cardiovascular Diseases > Cardiovascular Diseases>Biomedical Engineering.

Safety and Feasibility of a Novel Transnasal Cooling Device to Induce Normothermia in Febrile Cerebrovascular Patients

BACKGROUND

Inducing normothermia with surface cooling temperature modulating devices (TMDs) is cumbersome and often associated with significant shivering. We tested the safety and feasibility of a novel transnasal evaporative cooling device to induce and maintain normothermia in febrile patients following ischemic and hemorrhagic stroke.

METHODS

A single-center study utilizing the CoolStat® transnasal cooling device was used to achieve core temperature reduction in mechanically ventilated stroke patients with fever (T ≥ 38.3 C) refractory to acetaminophen by inducing an evaporative cooling energy exchange in the nasal turbinates thru a high flow of dehumidified air into the nasal cavity and out through the mouth. Continuous temperature measurements were obtained from tympanic and core (esophageal or bladder) temperature monitors. Safety assessments included continuous monitoring for hypertension, tachycardia, and raised intracranial pressure (when monitored). Otolaryngology (ENT) evaluations were monitored for any device-related nasal mucosal injury with a pre- and post-visual examination. Shivering was assessed every 30 min using the Bedside Shivering Assessment Scale (BSAS). Duration of device use was limited to 8 h, at which time patients were transitioned to routine care for temperature management.

RESULTS

Ten subjects (median age: 54 years, BMI: 32.5 kg/m², 60% men) were enrolled with normothermia achieved in 90% of subjects. One subject did not achieve normothermia and was later refractory to other TMDs. Median baseline temperature was 38.5 ± 0.1 C, with a reduction noted by 4 h (38.5 ± 0.1 vs 37.3 ± 0.8, P < 0.001) and sustained at 8 h (38.5 ± 0.1 vs 37.1 ± 0.7, P = 0.001). Time to normothermia was 2.6 ± 1.9 h. The median BSAS was 0 (range 0-1) with only 4 episodes necessitating meperidine across 76 h of study monitoring. No treatment was discontinued due to safety concerns. ENT evaluations noted no device-related adverse findings.

CONCLUSIONS

Inducing normothermia with a novel transnasal TMD appears to be safe, feasible and not associated with significant shivering. A multicenter trial testing the ability of the CoolStat to maintain normothermia for 24 h is currently underway.

Comparison of a Continuous Noninvasive Temperature to Monitor Core Temperature Measures During Targeted Temperature Management

Background

Temperature modulating devices (TMD) currently utilize core temperature measurements during targeted temperature management (TTM) that are currently limited to esophageal (Et), bladder (Bt), or rectal (Rt) temperatures. We assessed the ability of a continuous noninvasive temperature monitor to accurately approximate core temperature during TTM.

Methods

All patients undergoing TTM using a gel pad surface TMD and an existing core temperature monitoring device were eligible for this study. Core and continuous noninvasive temperature monitoring values were simultaneously recorded for up to 72 h of TTM. The two sets of temperature data were downloaded from a clinical data acquisition storage system at 1-min intervals. The Bland–Altman method assessed agreement between the core and continuous noninvasive temperature monitor values, by measuring the mean difference (± 2 SD) between these values.

Results

There were 20 subjects that underwent study between January 2018 and March 2018 (55% women, age: 57 ± 14 years old, BMI: 28.9 + 9.8 kg/m², 100% mechanically ventilated). The comparison patient temperature source was predominantly esophageal (n = 10) followed by bladder (n = 5) or rectal (n = 5). There were a total of 999 h of paired patient temperature data from esophageal (50%), bladder (25%), and rectal (25%) temperatures. Bland–Altman analysis demonstrated good agreement with the superficial temperature monitor and core temperature measures in all patients overall, with a difference mean of 0.06 ± 0.39 C (P = 0.99) and no proportional bias noted (β =0.002, P = 0.917).

Conclusions

Continuous noninvasive temperature monitoring is a suitable alternative method for assessing core temperature during TTM. Future studies should focus on developing connectivity with a continuous noninvasive temperature monitor to approximate core temperature during TTM.

The Use of Core Warming as a Treatment for Coronavirus Disease 2019 (COVID-19): an Initial Mathematical Model

Background: Increasing data suggest that elevated body temperature may be helpful in resolving a variety of diseases, including sepsis, acute respiratory distress syndrome (ARDS), and viral illnesses. SARS-CoV-2, which causes coronavirus disease 2019 (COVID-19), may be more temperature sensitive than other coronaviruses, particularly with respect to the binding affinity of its viral entry via the ACE2 receptor. A mechanical provision of elevated temperature focused in a body region of high viral activity in patients undergoing mechanical ventilation may offer a therapeutic option that avoids arrhythmias seen with some pharmaceutical treatments. We investigated the potential to actively provide core warming to the lungs of patients with a commercially available heat transfer device via mathematical modeling, and examine the influence of blood perfusion on temperature using this approach. Methods: Using the software Comsol Multiphysics, we modeled and simulated heat transfer in the body from an intraesophageal warming device, taking into account the airflow from patient ventilation. The simulation was focused on heat transfer and warming of the lungs and performed on a simplified geometry of an adult human body and airway from the pharynx to the lungs. Results: The simulations were run over a range of values for blood perfusion rate, which was a parameter expected to have high influence in overall heat transfer, since the heat capacity and density remain almost constant. The simulation results show a temperature distribution which agrees with the expected clinical experience, with the skin surface at a lower temperature than the rest of the body due to convective cooling in a typical hospital environment. The highest temperature in this case is the device warming water temperature, and that heat diffuses by conduction to the nearby tissues, including the air flowing in the airways. At the range of blood perfusion investigated, maximum lung temperature ranged from 37.6°C to 38.6°C. Conclusions: The provision of core warming via commercially available technology currently utilized in the intensive care unit, emergency department, and operating room can increase regional temperature of lung tissue and airway passages. This warming may offer an innovative approach to treating infectious diseases from viral illnesses such as COVID-19, while avoiding the arrhythmogenic complications of currently used pharmaceutical treatments.

Effects of High-Flow Transesophageal Dry Air on Core Temperature: A Novel Method of Therapeutic Hypothermia

Therapeutic hypothermia (TH) is one of the few proven neuroprotective modalities in clinical practice. However, current methods to achieve TH are suboptimal. We investigated a novel esophageal device that utilizes high-flow transesophageal dry air to achieve TH via evaporating cooling. Seven Yorkshire pigs (n = 7) underwent hypothermia therapy using a novel esophageal device that compartmentalizes a segment of esophagus through which high-flow dry air freely circulates in and out of the esophagus. Efficacy (primary objective) and safety (secondary objective) were evaluated in all animals. Safety assessment was divided into two sequential phases: (1) acute safety assessment (n = 5; terminal studies) to evaluate adverse events occurring during therapy, and (2) chronic safety assessment (n = 2; survival studies) to evaluate adverse events associated with therapy within 1 week of follow-up. After 1 hour of esophageal cooling (mean airflow rate = 64.2 ± 3.5 L/min), a significant reduction in rectal temperature was observed (37.3 ± 0.2°C → 36.3 ± 0.4°C, p = 0.002). The mean rectal temperature reduction was 1 ± 0.4°C. In none of the seven animals was oral or pharyngeal mucosa injury identified at postprocedural visual examination. In the two animals that survived, no reduction of food ingestion, signs of swallowing dysfunction or discomfort, or evidence of gastrointestinal bleeding was observed during the 1-week follow-up period. Open-chest visual inspection in those two animals did not show damage to the esophageal mucosa or surrounding structures. A novel esophageal device, utilizing high-flow transesophageal dry air, was able to efficiently induce hypothermia despite external heating. Therapy was well-tolerated, and no acute or chronic complications were found.

Esophageal Heat Exchanger Versus Water-Circulating Cooling Blanket for Targeted Temperature Management

To date, the optimal cooling device for targeted temperature management (TTM) remains unclear. Water-circulating cooling blankets are broadly available and quickly applied but reveal inaccuracy during maintenance and rewarming period. Recently, esophageal heat exchangers (EHEs) have been shown to be easily inserted, revealed effective cooling rates (0.26-1.12°C/h), acceptable deviations from target core temperature (<0.5°C), and rewarming rates between 0.2 and 0.4°C/h. The aim of this study was to compare cooling rates, accuracy during maintenance, and rewarming period as well as side effects of EHEs with water-circulating cooling blankets in a porcine TTM model. Mean core temperature of domestic pigs (n = 16) weighing 83.2 ± 3.6 kg was decreased to a target core temperature of 33°C by either using EHEs or water-circulating cooling blankets. After 8 hours of maintenance, rewarming was started at a goal rate of 0.25°C/h. Mean cooling rates were 1.3 ± 0.1°C/h (EHE) and 3.2 ± 0.5°C/h (blanket, p < 0.0002). Mean difference to target core temperature during maintenance ranged between ±1°C. Mean rewarming rates were 0.21 ± 0.01°C/h (EHE) and 0.22 ± 0.02°C/h (blanket, n.s.). There were no differences with regard to side effects such as brady- or tachycardia, hypo- or hyperkalemia, hypo- or hyperglycemia, hypotension, shivering, or esophageal tissue damage. Target temperature can be achieved faster by water-circulating cooling blankets. EHEs and water-circulating cooling blankets were demonstrated to be reliable and safe cooling devices in a prolonged porcine TTM model with more variability in EHE group.

Esophageal Temperature Management in Patients Suffering from Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of death in the United States, and represents 2.5 million Emergency Department attendances, admissions into hospital, and deaths. A range of temperature modulating devices have been used to proactively cool TBI patients; however, there are currently no uniform targeted temperature management (TTM) guidelines in this patient population. Esophageal temperature management (ETM) is a relatively new TTM modality and the purpose of this study is to determine whether ETM is effective in controlling core temperature in TBI cases. This prospective interventional trial was a single-site study that enrolled 12 patients who received a TTM protocol using ETM. Eleven out of 12 patients reached target temperature during the first 10 hours of treatment. A total of 480 temperature measurements were recorded; 85% of the total measurements were within ±1°C of target temperature (408 measurements) and 75% were within ±0.5°C of target temperature (360 measurements). The average time to target was 5.83 ± 5.01 hours (range 1–20), with an average cooling rate of 0.58°C/h (range 0.15–1.5°C/h). This prospective interventional trial supports that ETM is a feasible TTM modality for severe TBI cases. The esophageal heat transfer device used in this study demonstrated comparable or superior performance to other commercially available TTM modalities, and the low adverse event rate may offer advantages over more invasive methods with reported higher complication rates.