Usefulness of a surface cooling device (Arctic Sun®) for therapeutic hypothermia following cardiac arrest

Heat Transfer Capabilities of Surface Cooling Systems for Inducing Therapeutic Hypothermia

Therapeutic hypothermia (TH) is used to treat patients with cerebral ischemia. Body surface cooling provides a simple noninvasive method to induce TH. We compared three surface cooling systems (Arctic Sun with adhesive ArcticGel pads [AS]); Blanketrol III with two nonadhesive Maxi-Therm Lite blankets [BL]); and Blanketrol III with nonadhesive Kool Kit [KK]). We hypothesized that KK would remove more heat due to its tighter fit and increased surface area. Eight subjects (four females) were cooled with each system set to 4°C outflow temperature for 120 minutes. Heat loss, skin and esophageal temperature, and metabolic heat production were measured. Skin temperature was higher with KK (p = 0.002), heat loss was lower with KK in the first hour (p = 0.014) but not after 120 minutes. Heat production increased similarly with all systems. Core temperature decrease was greater for AS (0.57°C) than BL (0.14°C; p = 0.035), but not KK (0.24°C; p = 0.1). Each system had its own benefits and limitations. Heat transfer capability is dependent on the cooling pump unit and the design of the liquid-perfused covers. Both Arctic Sun and Blanketrol III cooling/pump units had 4°C output temperatures. However, the Blanketrol III unit had a greater flow rate and therefore more cooling power. The nonadhesive BL and KK covers were easier to apply and remove compared with the adhesive AS pads. AS had an early transient advantage in heat removal, but this effect decreased over the course of cooling, thus minimizing or eliminating any advantage during longer periods of cooling that occur during clinical TH. Clinical Trial Registration number: NCT04332224.

Efficacy and safety of the Arctic Sun device for hypoxic-ischemic encephalopathy in adult patients following cardiopulmonary resuscitation: A systematic review and meta-analysis

AIM

The principal objective of this study was to carry out a comprehensive and thorough analysis to compare the safety and effectiveness of the Arctic Sun, a servo-controlled surface cooling device, with conventional cooling techniques for providing therapeutic hypothermia in adult patients who had experienced hypoxic-ischemic brain injury following cardiopulmonary resuscitation.

METHODS

In order to achieve our goal, we conducted an extensive search of multiple databases including PubMed, Embase, Cochrane, and ClinicalTrials.gov up to the date of July 30, 2021. We only included studies that compared the safety and efficacy of the Arctic Sun surface cooling equipment with standard cooling approaches such as cooling blankets, ice packs, and intravenous cold saline for treating comatose adult patients who had recovered after experiencing cardiac arrest. We evaluated various outcomes, including all-cause mortality, good neurological outcome at 1 month, and the occurrence of adverse effects such as infections, shock, and bleeding. We employed a random-effects meta-analysis to estimate the odds ratio (OR) with 95% confidence intervals (CIs) for dichotomous outcomes.

RESULTS

One hundred and fourteen records were identified through our search; however, only three studies met our eligibility criteria, resulting in overall 187 patients incorporated in the meta-analysis. The findings indicated no significant difference in mortality rates among the Arctic Sun device and conventional cooling techniques (OR: 0.64; 95% CI: 0.34-1.19; P = 0.16; I2 = 0%). In addition, we found no significant difference in occurrence of good neurological outcomes (OR: 1.74; 95% CI: 0.94-3.25; P = 0.08; I2 = 0%) between the two cooling methods. However, the application of the Arctic Sun device was associated with increased incidence of infections compared to standard cooling methods (OR: 2.46; 95% CI: 1.18-5.11; P = 0.02; I2 = 0%). While no significant difference occurred in the incidence of shock (OR: 0.29; 95% CI: 0.07-1.18; P = 0.08; I2 = 40%), the use of the Arctic Sun device was linked to significantly fewer bleeding complications compared to standard cooling methods (OR: 0.11; 95% CI: 0.02-0.79; P = 0.03; I2 = 0%).

CONCLUSIONS

After analyzing the results of our meta-analysis, we concluded that the use of the Arctic Sun device for targeted temperature management following cardiopulmonary resuscitation did not result in significant differences in mortality rates or improve neurological outcomes when compared to standard cooling techniques.

Analysis of rebound intracranial pressure occurring during rewarming after therapeutic hypothermia in traumatic brain injury patients

OBJECTIVE

To investigate the risk factors associated with rebound intracranial pressure (ICP), a phenomenon that occurs when brain swelling reprogresses rapidly during rewarming in patients who have undergone therapeutic hypothermia for traumatic brain injury (TBI).

METHODS

This study analyzed 42 patients who underwent therapeutic hypothermia among 172 patients with severe TBI admitted to a single regional trauma center between January 2017 and December 2020. Forty-two patients were classified into 34.5 °C (mild) and 33 °C (moderate) hypothermia groups according to the therapeutic hypothermia protocol for TBI. Rewarming was initiated post-hypothermia, wherein ICP was maintained at ≤ 20 mmHg and cerebral perfusion pressure was maintained at ≥ 50 mmHg for ≥ 24 h. In the rewarming protocol, the target core temperature was increased to 36.5 °C at 0.1 °C/h.

RESULTS

Of the 42 patients who underwent therapeutic hypothermia, 27 did not survive: 9 in the mild and 18 in the moderate hypothermia groups. The moderate hypothermia group had a significantly higher mortality rate than the mild hypothermia group (p = 0.013). Rebound ICP occurred in 9 of 25 patients: 2 in the mild and 7 in the moderate hypothermia groups. In the risk factor analysis of rebound ICP, only the degree of hypothermia was statistically significant, and rebound ICP was observed more frequently in the moderate than in the mild hypothermia group (p = 0.025).

CONCLUSIONS

In patients who underwent rewarming after therapeutic hypothermia, rebound ICP presented a higher risk at 33 °C than at 34.5 °C. Therefore, more careful rewarming is needed in patients receiving therapeutic hypothermia at 33 °C.

Intravascular Versus Surface Cooling in Patients Resuscitated From Cardiac Arrest: A Systematic Review and Network Meta-Analysis With Focus on Temperature Feedback

OBJECTIVE

The aim of the study was to compare the effect of intravascular cooling (IC), surface cooling with temperature feedback (SCF), and surface cooling without temperature feedback (SCnoF) on neurologic outcome and survival in patients successfully resuscitated from cardiac arrest (CA) and treated with targeted temperature management (TTM) at 32-34°C.

DATA SOURCES

We performed a systematic review on Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, MEDLINE, SCOPUS, CINAHL, Web of Science, and Clinical Trials up to June 30, 2021.

STUDY SELECTION

We included randomized and nonrandomized studies on IC, SCF, and SCnoF in adult humans resuscitated from CA undergoing TTM, reporting neurologic outcome or survival.

DATA EXTRACTION

We performed a network meta-analysis to assess the comparative effects of IC, SCF, and SCnoF. The overall effect between two cooling methods included the effect of direct and indirect comparisons. Results are given as odds ratios (OR) and 95% CIs. Rankograms estimated the probability of TTM methods being ranked first, second, and third best interventions.

DATA SYNTHESIS

A total of 14 studies involving 4,062 patients met the inclusion criteria. Four studies were randomized controlled studies, and 10 studies were nonrandomized observational studies. IC compared with SCnoF was significantly associated with better neurologic outcome (OR, 0.6; 95% CI, 0.49-0.74) and survival (OR, 0.8; 95% CI, 0.66-0.96). IC compared with SCF, and SCF compared with SCnoF did not show significant differences in neurologic outcome and survival. The rankogram showed that IC had the highest probability to be the most beneficial cooling method, followed by SCF and SCnoF.

CONCLUSIONS

Our results suggest that in patients resuscitated from CA and treated with TTM at 32-34°C, IC has the highest probability of being the most beneficial cooling method for survival and neurologic outcome.

Comparison of hydrogel pad and water-circulating blanket cooling methods for targeted temperature management: A propensity score-matched analysis from a prospective multicentre registry

BACKGROUND

Various methods have been used to control body temperature in targeted temperature management (TTM), but few studies have compared specific subtypes of surface cooling systems. The aim of this study was to compare the efficiencies and neurological outcomes between hydrogels pad and water-circulating blanket cooling methods.

METHODS

We conducted a multicentre, prospective, registry-based study of out-of-hospital cardiac arrest patients treated with TTM between 2015 and 2018. We compared the neurological outcomes, efficacies for cooling, and adverse events between patients who received TTM using a hydrogel pad and water-circulating blanket cooling. Patients were one-to-one matched using propensity scores to adjust for differences in the baseline characteristics of each cooling method. The primary outcome was a favourable neurological outcome at 6 months.

RESULTS

We included 1,132 patients in the analysis, 870 of whom underwent hydrogel pad cooling, and the remaining 262 underwent water-circulating blanket cooling. In the unmatched cohort, a greater number of adverse events occurred in the water-circulating blanket group. The favourable neurologic outcome rates at 6 months were similar between the hydrogel pad group and the water circulating blanket group (30.2% vs. 29.8%, p = 0.939). In the propensity-matched cohort, which included 184 pairs, the rates of adverse events between the two groups were similar. The similarity of favourable neurologic outcome rates at 6 months between the two groups persisted (28.8% vs. 29.9%, p = 0.819).

CONCLUSION

Neurological outcomes and adverse events between the hydrogel pad cooling and water-circulating blanket cooling groups were similar.

Effect of different methods of cooling for targeted temperature management on outcome after cardiac arrest: a systematic review and meta-analysis

Background

Although targeted temperature management (TTM) is recommended in comatose survivors after cardiac arrest (CA), the optimal method to deliver TTM remains unknown. We performed a meta-analysis to evaluate the effects of different TTM methods on survival and neurological outcome after adult CA.

Methods

We searched on the MEDLINE/PubMed database until 22 February 2019 for comparative studies that evaluated at least two different TTM methods in CA patients. Data were extracted independently by two authors. We used the Newcastle-Ottawa Scale and a modified Cochrane ROB tools for assessing the risk of bias of each study. The primary outcome was the occurrence of unfavorable neurological outcome (UO); secondary outcomes included overall mortality.

Results

Our search identified 6886 studies; 22 studies (n = 8027 patients) were included in the final analysis. When compared to surface cooling, core methods showed a lower probability of UO (OR 0.85 [95% CIs 0.75–0.96]; p = 0.008) but not mortality (OR 0.88 [95% CIs 0.62–1.25]; p = 0.21). No significant heterogeneity was observed among studies. However, these effects were observed in the analyses of non-RCTs. A significant lower probability of both UO and mortality were observed when invasive TTM methods were compared to non-invasive TTM methods and when temperature feedback devices (TFD) were compared to non-TFD methods. These results were significant particularly in non-RCTs.

Conclusions

Although existing literature is mostly based on retrospective or prospective studies, specific TTM methods (i.e., core, invasive, and with TFD) were associated with a lower probability of poor neurological outcome when compared to other methods in adult CA survivors (CRD42019111021).

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2567-6) contains supplementary material, which is available to authorized users.

A comparison of intravascular and surface cooling devices for targeted temperature management after out-of-hospital cardiac arrest: A nationwide observational study

This study aimed to compare prognostic difference between intravascular cooling devices (ICDs) and surface cooling devices (SCDs) in targeted temperature management (TTM) recipients.Adult TTM recipients using ICD or SCD during 2012 to 2016 were included in this nationwide observational study. The outcome was survival to hospital discharge and good neurological outcome at hospital discharge.Among 142,905 out-of-hospital cardiac arrest patients, 1159 patients (SCD, n = 998; ICD, n = 161) were investigated. After propensity score matching for all patients, 161 matched pairs of patients were available for analysis (SCD, n = 161; ICD, n = 161). We observed no significant differences in the survival to hospital discharge (SCD, n = 144 [89.4%] vs ICD, n = 150 [93.2%], P = .32) and the good neurological outcomes (SCD, n = 86 [53.4%] vs ICD, n = 91 [56.5%], P = .65). TTM recipients were categorized by age groups (elderly [age >65 years] vs nonelderly [age ≤65 years]) to compare prognostic difference between ICD and SCD according to the age groups. In the nonelderly group, the use of ICD or SCD was not a significant factor for survival to hospital discharge or good neurologic outcome. Whereas, the use of ICD was significantly associated with good neurological outcome (odds ratio, 3.97; 95% confidence interval, 1.19 - 13.23, P = .02) compared with SCD in the elderly group.There were no significant differences in the survival to hospital discharge and the good neurological outcomes between SCD and ICD recipients. However, the use of ICD might be more beneficial than SCD in elderly patients.

Intravascular versus surface cooling for targeted temperature management after out-of-hospital cardiac arrest: an analysis of the TTH48 trial

Background

The aim of this study was to explore the performance and outcomes for intravascular (IC) versus surface cooling devices (SFC) for targeted temperature management (TTM) after out-of-hospital cardiac arrest.

Methods

A retrospective analysis of data from the Time-differentiated Therapeutic Hypothermia (TTH48) trial (NCT01689077), which compared whether TTM at 33 °C for 48 h results in better neurologic outcomes compared with standard 24-h duration. Devices were assessed for the speed of cooling and rewarming rates. Precision was assessed by measuring temperature variability (TV), i.e., the standard deviation (SD) of all temperature measurements in the cooling phase. Main outcomes were overall mortality and poor neurological outcome, including death, severe disability, or vegetative status.

Results

A total of 352 patients had available data and were included in the analysis; of those, 218 (62%) were managed with IC. A total of 114/218 (53%) patients with IC and 61/134 (43%) with SFC were cooled for 48 h (p = 0.22). Time to target temperature (≤ 34 °C) was significantly shorter for patients treated with endovascular devices (2.2 [1.1–4.0] vs. 4.2 [2.7–6.0] h, p < 0.001), but temperature was also lower on admission (35.0 [34.2–35.6] vs. 35.3 [34.5–35.8]°C; p = 0.02) and cooling rate was similar (0.4 [0.2–0.8] vs. 0.4 [0.2–0.6]°C/h; p = 0.14) when compared to SFC. Temperature variability was significantly lower in the endovascular device group when compared with SFC methods (0.6 [0.4–0.9] vs. 0.7 [0.5–1.0]°C; p = 0.007), as was rewarming rate (0.31 [0.22–0.44] vs. 0.37 [0.29–0.49]°C/hour; p = 0.02). There was no statistically significant difference in mortality (endovascular 65/218, 29% vs. others 43/134, 32%; p = 0.72) or poor neurological outcome (endovascular 69/218, 32% vs. others 51/134, 38%; p = 0.24) between type of devices.

Conclusions

Endovascular cooling devices were more precise than SFC methods in patients cooled at 33 °C after out-of-hospital cardiac arrest. Main outcomes were similar with regard to the cooling methods.

Targeted Temperature Management; Review of Literature and Guidelines; A Cardiologist's Perspective

BACKGROUND

Out of Hospital Cardiac Arrest (OHCA) remains not an uncommon occurrence in USA and the rest of the world. However, the survival to discharge following an episode of OHCA in adults is still very disappointing at around 10%. Several areas of improvement including education of general public in early Cardio Pulmonary Resuscitation (CPR) by bystander, chest compression first, and improvement of Emergency Medical response time have had a positive effect on the outcomes and survival but still much needs to be done. Recently, new data has emerged with regards to post resuscitation care and mild induced hypothermia (now preferably called; Targeted Temperature Management {TTM}) and several advances have been made.

CONCLUSION

The purpose of this review is to summarize and compare the most recent guidelines and also provide a practical approach to TTM especially with regards to the field of cardiology.

Editor's Choice-Effects of targeted temperature management on mortality and neurological outcome: A systematic review and meta-analysis

AIMS

The purpose of this study was to conduct a systematic review, and where applicable meta-analyses, examining the evidence underpinning the use of targeted temperature management following resuscitation from cardiac arrest.

METHODS AND RESULTS

Multiple databases were searched for publications between January 2000-February 2016. Nine Population, Intervention, Comparison, Outcome questions were developed and meta-analyses were performed when appropriate. Reviewers extracted study data and performed quality assessments using Grading of Recommendations, Assessment, Development and Evaluation methodology, the Cochrane Risk Bias Tool, and the National Institute of Health Study Quality Assessment Tool. The primary outcomes for each Population, Intervention, Comparison, Outcome question were mortality and poor neurological outcome. Overall, low quality evidence demonstrated that targeted temperature management at 32-36°C, compared to no targeted temperature management, decreased mortality (risk ratio 0.76, 95% confidence interval 0.61-0.92) and poor neurological outcome (risk ratio 0.73, 95% confidence interval 0.60-0.88) amongst adult survivors of out-of-hospital cardiac arrest with an initial shockable rhythm. Targeted temperature management use did not benefit survivors of in-hospital cardiac arrest nor out-of-hospital cardiac arrest survivors with a non-shockable rhythm. Moderate quality evidence demonstrated no benefit of pre-hospital targeted temperature management initiation. Low quality evidence showed no difference between endovascular versus surface cooling targeted temperature management systems, nor any benefit of adding feedback control to targeted temperature management systems. Low quality evidence suggested that targeted temperature management be maintained for 18-24 h.

CONCLUSIONS

Low quality evidence supports the in-hospital initiation and maintenance of targeted temperature management at 32-36°C amongst adult survivors of out-of-hospital cardiac arrest with an initial shockable rhythm for 18-24 h. The effects of targeted temperature management on other populations, the optimal rate and method of cooling and rewarming, and effects of fever require further study.

Comparison of Two Surface Cooling Devices for Temperature Management in a Neurocritical Care Unit

Fever increases mortality and morbidity and length of stay in neurocritically ill patients. Various methods are used in the neuroscience intensive care unit (NSICU) to control fever. Two such methods involve the Arctic Sun hydrogel wraps and the Gaymar cooling wraps. The purpose of our study was to compare these two methods in neurocritical care patients who had temperature >37.5°C for more than three consecutive hours and that was refractory to standard treatments. Data of patients requiring cooling wraps for treatment of hyperthermia at an NSICU at an academic, tertiary referral center were retrospectively reviewed. The average temperature before cooling was 38.5°C ± 0.38°C and 38.4°C ± 0.99°C for the Gaymar and Arctic Sun groups, respectively (p = 0.89). The Gaymar group took on average 16 ± 21.9 hours to reach goal temperature, whereas the Arctic Sun group took 2.22 ± 1.39 hours (p = 0.08). The average time outside of the target temperature was 57.0 ± 58.0 hours in the Gaymar group compared with 13.7 ± 17.1 hours in the Arctic Sun group (p = 0.04). Average duration of using the cooling wraps was similar between the two groups; 81.8% of patients had rebound hyperthermia in the Gaymar group compared with 20% in the Arctic Sun group (p = 0.0089). The Arctic Sun group had a nonsignificant increased incidence of shivering compared with the Gaymar group (40% vs. 18.18%, p = 0.36). We found that Arctic Sun surface cooling device was more efficient in attaining the target temperature, had less incidence of rebound hyperthermia, and was able to maintain normothermia better than Gaymar cooling wraps. The incidence of shivering tended to be more common in the Arctic Sun group.

Intravascular versus surface cooling for targeted temperature management after out-of-hospital cardiac arrest - an analysis of the TTM trial data

Background

Targeted temperature management is recommended after out-of-hospital cardiac arrest and may be achieved using a variety of cooling devices. This study was conducted to explore the performance and outcomes for intravascular versus surface devices for targeted temperature management after out-of-hospital cardiac arrest.

Method

A retrospective analysis of data from the Targeted Temperature Management trial. N = 934. A total of 240 patients (26%) managed with intravascular versus 694 (74%) with surface devices. Devices were assessed for speed and precision during the induction, maintenance and rewarming phases in addition to adverse events. All-cause mortality, as well as a composite of poor neurological function or death, as evaluated by the Cerebral Performance Category and modified Rankin scale were analysed.

Results

For patients managed at 33 °C there was no difference between intravascular and surface groups in the median time taken to achieve target temperature (210 [interquartile range (IQR) 180] minutes vs. 240 [IQR 180] minutes, p = 0.58), maximum rate of cooling (1.0 [0.7] vs. 1.0 [0.9] °C/hr, p = 0.44), the number of patients who reached target temperature (within 4 hours (65% vs. 60%, p = 0.30); or ever (100% vs. 97%, p = 0.47), or episodes of overcooling (8% vs. 34%, p = 0.15). In the maintenance phase, cumulative temperature deviation (median 3.2 [IQR 5.0] °C hr vs. 9.3 [IQR 8.0] °C hr, p = <0.001), number of patients ever out of range (57.0% vs. 91.5%, p = 0.006) and median time out of range (1 [IQR 4.0] hours vs. 8.0 [IQR 9.0] hours, p = <0.001) were all significantly greater in the surface group although there was no difference in the occurrence of pyrexia. Adverse events were not different between intravascular and surface groups. There was no statistically significant difference in mortality (intravascular 46.3% vs. surface 50.0%; p = 0.32), Cerebral Performance Category scale 3–5 (49.0% vs. 54.3%; p = 0.18) or modified Rankin scale 4–6 (49.0% vs. 53.0%; p = 0.48).

Conclusions

Intravascular and surface cooling was equally effective during induction of mild hypothermia. However, surface cooling was associated with less precision during the maintenance phase. There was no difference in adverse events, mortality or poor neurological outcomes between patients treated with intravascular and surface cooling devices.

Trial registration

TTM trial ClinicalTrials.gov number https://clinicaltrials.gov/ct2/show/NCT01020916NCT01020916; 25 November 2009

Resistance to conventional cardiopulmonary resuscitation in witnessed out-of-hospital cardiac arrest patients with shockable initial cardiac rhythm

BACKGROUND

Shockable initial cardiac rhythm is a key predictor of survival after out-of-hospital cardiac arrest (OHCA). However, not all patients with shockable OHCA achieve return of spontaneous circulation (ROSC) via conventional cardiopulmonary resuscitation (CPR). Therefore, we retrospectively analyzed patients with witnessed OHCA and shockable initial cardiac rhythm to identify the resistance factors for conventional CPR.

METHODS

We retrospectively analyzed consecutive patients with witnessed OHCA and shockable initial cardiac rhythm who were admitted to our hospital between October 2009 and October 2014. We then compared the baseline characteristics, pre-hospital clinical course, and causes of the cardiopulmonary arrest among patients who achieved ROSC via conventional CPR and patients who did not achieve ROSC via conventional CPR and underwent extracorporeal CPR (ECPR).

RESULTS

A total of 85 patients achieved ROSC via conventional CPR (non-ECPR group) and 40 patients did not achieve ROSC via conventional CPR and underwent ECPR (ECPR group). Among these 125 patients, 113 had known causes for their cardiopulmonary arrest, including 66 cases (53%) of acute myocardial infarction (AMI). There were no significant differences in the causes of arrest between the non-ECPR and ECPR cases. However, among the 66 cases of AMI (43 non-ECPR and 23 ECPR), the rate of non-recanalization during the initial coronary angiography was significantly higher among the ECPR cases (non-ECPR: 58% vs. ECPR: 87%; p=0.03).

CONCLUSIONS

The major cause of witnessed OHCA with shockable initial cardiac rhythm was AMI, and resistance to conventional CPR was related to continuous myocardial ischemia.

Effect of Admission Glasgow Coma Scale Motor Score on Neurological Outcome in Out-of-Hospital Cardiac Arrest Patients Receiving Therapeutic Hypothermia

BACKGROUND

Because the initial (on admission) Glasgow Coma Scale (GCS) examination has not been fully evaluated in comatose survivors of cardiac arrest (CA) who receive therapeutic hypothermia (TH), the aim of the present study was to determine any association between the admission GCS motor score and neurologic outcomes in patients with out-of-hospital CA who receive TH.

METHODS AND RESULTS

In the J-PULSE-HYPO study registry, patients with bystander-witnessed CA were eligible for inclusion. Patients were divided into 3 groups based on GCS motor score (1, 2-3, and 4-5) to assess various effects on neurologic outcome. Univariate and multivariate analyses were performed to identify independent predictors of good neurologic outcome at 90 days. Of 452 patients, 302 were enrolled. There was a significant difference among the 3 patient groups with regard to neurologic outcome at 90 days in the univariate analysis. Multiple logistic regression analyses showed that the GCS motor score on admission, age >65 years, bystander cardiopulmonary resuscitation, the time from collapse to return of spontaneous circulation, and pupil size <4 mm were independent predictors of a good neurologic outcome at 90 days in cases of CA (GCS motor score, 4-5: odds ratio, 8.18; 95% confidence interval: 1.90-60.28; P<0.01).

CONCLUSIONS

GCS motor score is an independent predictor of good neurologic outcome at 90 days in patients sustaining out-of-hospital CA who receive TH.

Therapeutic hypothermia for acute brain injuries

Therapeutic hypothermia, recently termed target temperature management (TTM), is the cornerstone of neuroprotective strategy. Dating to the pioneer works of Fay, nearly 75 years of basic and clinical evidence support its therapeutic value. Although hypothermia decreases the metabolic rate to restore the supply and demand of O₂, it has other tissue-specific effects, such as decreasing excitotoxicity, limiting inflammation, preventing ATP depletion, reducing free radical production and also intracellular calcium overload to avoid apoptosis. Currently, mild hypothermia (33°C) has become a standard in post-resuscitative care and perinatal asphyxia. However, evidence indicates that hypothermia could be useful in neurologic injuries, such as stroke, subarachnoid hemorrhage and traumatic brain injury. In this review, we discuss the basic and clinical evidence supporting the use of TTM in critical care for acute brain injury that extends beyond care after cardiac arrest, such as for ischemic and hemorrhagic strokes, subarachnoid hemorrhage, and traumatic brain injury. We review the historical perspectives of TTM, provide an overview of the techniques and protocols and the pathophysiologic consequences of hypothermia. In addition, we include our experience of managing patients with acute brain injuries treated using endovascular hypothermia.

An observational study of surface versus endovascular cooling techniques in cardiac arrest patients: a propensity-matched analysis

INTRODUCTION

Various methods and devices have been described for cooling after cardiac arrest, but the ideal cooling method remains unclear. The aim of this study was to compare the neurological outcomes, efficacies and adverse events of surface and endovascular cooling techniques in cardiac arrest patients.

METHODS

We performed a multicenter, retrospective, registry-based study of adult cardiac arrest patients treated with therapeutic hypothermia presenting to 24 hospitals across South Korea from 2007 to 2012. We included patients who received therapeutic hypothermia using overall surface or endovascular cooling devices and compared the neurological outcomes, efficacies and adverse events of both cooling techniques. To adjust for differences in the baseline characteristics of each cooling method, we performed one-to-one matching by the propensity score.

RESULTS

In total, 803 patients were included in the analysis. Of these patients, 559 underwent surface cooling, and the remaining 244 patients underwent endovascular cooling. In the unmatched cohort, a greater number of adverse events occurred in the surface cooling group. Surface cooling was significantly associated with a poor neurological outcome (cerebral performance category 3-5) at hospital discharge (p = 0.01). After propensity score matching, surface cooling was not associated with poor neurological outcome and hospital mortality [odds ratio (OR): 1.26, 95% confidence interval (CI): 0.81-1.96, p = 0.31 and OR: 0.85, 95% CI: 0.55-1.30, p = 0.44, respectively]. Although surface cooling was associated with an increased incidence of adverse events (such as overcooling, rebound hyperthermia, rewarming related hypoglycemia and hypotension) compared with endovascular cooling, these complications were not associated with surface cooling using hydrogel pads.

CONCLUSIONS

In the overall matched cohort, no significant difference in neurological outcomes and hospital morality was observed between the surface and endovascular cooling methods.

Intravascular versus surface cooling speed and stability after cardiopulmonary resuscitation

BACKGROUND AND OBJECTIVE

Mild therapeutic hypothermia (MTH) is used to limit neurological injury and improve survival after cardiac arrest (CA) and cardiopulmonary resuscitation, but the optimal mode of cooling is controversial. We therefore compared the effectiveness of MTH using invasive intravascular or non-invasive surface cooling with temperature feedback control.

METHODS

This retrospective study in post-CA patients studied the effects of intravascular cooling (CoolGard, Zoll, n=97), applied on the intensive care unit (ICU) in one university hospital compared with those of surface cooling (Medi-Therm, Gaymar, n=76) applied in another university hospital.

RESULTS

Time to reach target temperature and cooling speeds did not differ between groups. During the maintenance phase, mean core temperature was 33.1°C (range 32.7-33.7°C) versus 32.5°C (range 31.7-33.4°C) at targets of 33.0 and 32.5°C in intravascularly versus surface cooled patients, respectively. The variation coefficient for temperature during maintenance was higher in the surface than the intravascular cooling group (mean 0.85% vs 0.35%, p<0.0001). ICU survival was 60% and 50% in the intravascularly and surface cooled groups, respectively (NS). Lower age (OR 0.95; 95% CI 0.93 to 0.98; p<0.0001), ventricular fibrillation/ventricular tachycardia as presenting rhythm (OR 7.6; 95% CI 1.8 to 8.9; p<0.0001) and lower mean temperature during the maintenance phase (OR 0.52; 95% CI 0.25 to 1.08; p=0.081) might be independent determinants of ICU survival, while cooling technique and temperature variability did not contribute.

CONCLUSIONS

In post-CA patients, intravascular cooling systems result in equal cooling speed, but less variation in temperature during the maintenance phase, as surface cooling. This may not affect the outcome.