Induction of therapeutic hypothermia after cardiac arrest in prehospital patients using ice-cold Ringer’s solution: a pilot study

Impact of Induced Therapeutic Hypothermia by Intravenous Infusion of Ice-Cold Fluids After Hospital Arrival in Comatose Survivors of Out-of-Hospital Cardiac Arrest With Initial Shockable Rhythm

BACKGROUND

The effect of in-hospital rapid cooling by intravenous ice-cold fluids for comatose survivors of out-of-hospital cardiac arrest (OHCA) is unclear.

METHODS AND RESULTS

From the J-PULSE-HYPO study registry, data for 248 comatose survivors with return of spontaneous circulation (ROSC) who were treated with therapeutic hypothermia (34℃ for 12-72 h) after witnessed shockable OHCA were extracted. Patients were divided into 2 groups by the median collapse-to-ROSC interval (18 min), and then into 2 groups by cooling method (rapid cooling by intravenous ice-cold fluids vs. standard cooling). The primary endpoint was favorable neurological outcome (Cerebral Performance Category of 1 or 2) at 30 days after OHCA. In the whole cohort, the shorter collapse-to-ROSC interval group had significantly higher favorable neurological outcome than the longer collapse-to-ROSC interval group (78.2% vs. 46.8%, P<0.001). In the shorter collapse-to-ROSC interval group, no significant difference was observed in favorable neurological outcome between the 2 cooling groups (rapid cooling group: 79.4% vs. standard cooling group: 77.0%, P=0.75). In the longer collapse-to-ROSC interval group, however, favorable neurological outcome was significant higher in the rapid cooling group than in the standard cooling group (60.7% vs. 33.3%, P<0.01) and the adjusted odds ratio after rapid cooling was 3.069 (95% confidence interval 1.423-6.616, P=0.004).

CONCLUSIONS

In-hospital rapid cooling by intravenous ice-cold fluids improved neurologically intact survival in comatose survivors whose collapse-to-ROSC interval was delayed over 18 min after shockable OHCA.

Hypothermia for Acute Spinal Cord Injury

Neuroprotection after acute spinal cord injury is an important strategy to limit secondary injury. Animal studies have shown that systemic hypothermia is an effective neuroprotective strategy that can be combined with other therapies. Systemic hypothermia affects several processes at the cellular level to reduce metabolic activity, oxidative stress, and apoptotic neuronal cell death. Modest systemic hypothermia has been shown to be safe and feasible in the acute phase after cervical spinal cord injury. These data have provided the impetus for an active multicenter randomized controlled trial for modest systemic hypothermia in acute cervical spinal cord injury.

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.

Comparison of early sequential hypothermia and delayed hypothermia on neurological function after resuscitation in a swine model

BACKGROUND

We utilized a porcine cardiac arrest model to compare early sequential hypothermia (ESH) with delayed hypothermia (DH) and no hypothermia (NH) to investigate the different effects on cerebral function after resuscitation.

METHODS

After return of spontaneous circulation (ROSC), resuscitated 24 pigs divided into three groups. The ESH group implemented early sequential hypothermia immediately, and the DH group implemented delayed hypothermia at 1 h after ROSC. The core temperature, hemodynamic parameters and oxygen metabolism were recorded. Cerebral metabolism variables and neurotransmitter in the extracellular fluid were collected through the microdialysis tubes. The bloods were analyzed for venous jugular bulb oxygen saturation, lactate and neuron specific nolase. The cerebral function was evaluated using the cerebral performance category and neurologic deficit score at 72h after ROSC and cerebral histology in the right posterior frontal lobe were collected.

RESULTS

ESH reached the target temperature earlier and showed more favorable outcomes of neurological function than DH. Specifically, early sequential hypothermia reduced cerebral oxygen and energy consumption and decreased extracellular accumulation of neurotransmitters after resuscitation and protected the integrity of the BBB during reperfusion.

CONCLUSIONS

Early sequential hypothermia could increase the protection of neurological function after resuscitation and produce better neurological outcomes. The institutional protocol number: 2010-D-013.

The Outcomes of Targeted Temperature Management After Cardiac Arrest at Emergency Department: A Real-World Experience in a Developing Country

Targeted temperature management (TTM) is indicated for comatose survivors of cardiac arrest to improve outcomes. However, the benefit of TTM was verified by rigid controlled clinical trials. This study aimed at evaluating its effects in real-world practices. A prospective observational study was done at the emergency department of tertiary care, Thammasat Hospital, from March 2012 until October 2015. We included all who did not obey verbal commands after being resuscitated from cardiac arrest regardless of initial cardiac rhythm. We excluded patients with traumatic arrest, uncontrolled bleeding, younger than 15 years old, and of poor neurological status (Glasgow coma scale below 14) before cardiac arrest. Primary and secondary outcomes were survival to hospital discharge and favorable neurological outcome (Cerebral Performance Categories 1 or 2 within 30 days). We used the logistic regression model to estimate the propensity score (PS) that will be used as a weight in the analysis. To analyze outcomes, the PS was introduced as a factor in the final logistic regression model in conjunction with other factors. A total of 192 cases, 61 and 131 patients, were enrolled in TTM and non-TTM groups, respectively. Characteristics believed to be related to initiation of TTM: gender, age, cardiac etiology, out-of-hospital cardiac arrest, witness arrest, collapse time, initial rhythm, received defibrillation, and advanced airway insertion, were included in multivariable analysis and estimated PS. After adjusted regression analysis with PS, the TTM group had a better result in survival to hospital discharge (34.43% vs. 12.21%; adjusted incidence risk ratio (IRR), 2.95; 95% confidence interval (CI), 1.49-5.84; p = 0.002). For neurological outcome, the TTM group had a higher number of favorable neurological outcomes (24.59% vs. 6.87%; IRR, 3.96; 95% CI, 1.67-9.36; p = 0.002). In real-world practices without a strictly controlled environment, TTM can improve survival and favorable neurological outcome in postcardiac arrest patients regardless of initial rhythm.

Application of a novel rectal cooling device in hypothermia therapy after cerebral hypoxia-ischemia in rats

BACKGROUND

A new rectal cooling device for therapeutic hypothermia (TH) therapy is designed and is applied in TH treatment of SD rats with ischemic-hypoxic brain damage.

METHODS

Healthy adult SD rats (n = 45) were randomly assigned into four groups: the healthy control group (n = 5), the ischemia and hypoxia group (n = 10), the rectal TH cooling group (n = 18), and the ice blanket TH cooling group (n = 11). The rats in the rectal cooling and ice blanket TH groups received 12 h treatment after hypoxic-ischemic brain damage had been established, while those in the ischemia and hypoxia group did not. Taking the start of TH as the zero point, rats were sacrificed after 24 h and the brain and rectum tissues were sampled for histological analysis.

RESULTS

The TH induction time (37.3 ± 14.7 min) in the rectal cooling group was significantly shorter (F = 4.937, P < 0.05) than that in the ice blanket cooling group (75.6 ± 27.2 min). The HE and NISSL staining results showed that rats in the rectal TH cooling group had significantly decreased (P < 0.01) positive neurons cell count compared to those in ischemia and hypoxia group. In addition, TUNEL staining indicated that the number of apoptotic cells (3.9 ± 1.8 cells / × 400 field) and the apoptosis index (4.4 % ± 1.5) were significantly lower in rectal TH cooling group (P < 0.05) than in ischemia and hypoxia group (23.2 ± 12.1 cells / × 400 field, 26.6 % ± 12.1). Also, no rectal frostbite or inflammatory infiltration was observed in rats in the rectal TH treatment groups.

CONCLUSION

Our new cooling device realized rapid TH induction in SD rats with ischemic-hypoxic brain damage, inhibited the apoptosis of cells in the hippocampal CAl region, and did not cause histological damage to the rectal tissues.

Prehospital therapeutic hypothermia after out-of-hospital cardiac arrest: a systematic review and meta-analysis

BACKGROUND

The effectiveness and safety of the infusion of ice-cold fluids for prehospital hypothermia in cardiac arrest victims are unclear. This study assessed its effects in adult victims of out-of-hospital cardiac arrest.

METHODS

An online search of PubMed and Cochrane Library databases was performed. Cooling methods were limited to ice-cold fluid perfusion. Randomized controlled trials were included in this review. The main outcomes were body temperature at hospital arrival, survival to hospital discharge, neurological recovery, incidence of pulmonary edema, and the rate of rearrest.

RESULTS

Among 1155 citations, 5 studies were included in this meta-analysis. The pooled analysis of these studies revealed no differences in survival to hospital discharge, favorable neurological outcomes, and incidence of pulmonary edema between the treatment group and control group. There were significant differences in body temperature at hospital arrival (I² = 0.0%, χ² = 2.58, MD = -0.760, 95% confidence interval = -0.938 to -0.581, P < .001) and the rate of rearrest (I² = 0.0%, χ² = 0.69, 95% confidence interval = 1.109 to 1.479, P = .031).

CONCLUSIONS

Prehospital therapeutic hypothermia induced by intravenous infusion of ice-cold fluids in patients with out-of-hospital cardiac arrest decreased body temperature at hospital arrival but did not improve survival to hospital discharge and favorable neurological outcomes. Ice-cold fluid infusion did not increase the incidence of pulmonary edema but increased the incidence of rearrests.

Induced Hypothermia Does Not Harm Hemodynamics after Polytrauma: A Porcine Model

BACKGROUND

The deterioration of hemodynamics instantly endangers the patients' life after polytrauma. As accidental hypothermia frequently occurs in polytrauma, therapeutic hypothermia still displays an ambivalent role as the impact on the cardiopulmonary function is not yet fully understood.

METHODS

We have previously established a porcine polytrauma model including blunt chest trauma, penetrating abdominal trauma, and hemorrhagic shock. Therapeutic hypothermia (34°C) was induced for 3 hours. We documented cardiovascular parameters and basic respiratory parameters. Pigs were euthanized after 15.5 hours.

RESULTS

Our polytrauma porcine model displayed sufficient trauma impact. Resuscitation showed adequate restoration of hemodynamics. Induced hypothermia had neither harmful nor major positive effects on the animals' hemodynamics. Though heart rate significantly decreased and mixed venous oxygen saturation significantly increased during therapeutic hypothermia. Mean arterial blood pressure, central venous pressure, pulmonary arterial pressure, and wedge pressure showed no significant differences comparing normothermic trauma and hypothermic trauma pigs during hypothermia.

CONCLUSIONS

Induced hypothermia after polytrauma is feasible. No major harmful effects on hemodynamics were observed. Therapeutic hypothermia revealed hints for tissue protective impact. But the chosen length for therapeutic hypothermia was too short. Nevertheless, therapeutic hypothermia might be a useful tool for intensive care after polytrauma. Future studies should extend therapeutic hypothermia.

No benefit to prehospital initiation of therapeutic hypothermia in out-of-hospital cardiac arrest: a systematic review and meta-analysis

OBJECTIVES

The aim of this review was to define the effect of prehospital therapeutic hypothermia (TH) on survival and neurologic recovery in patients who have suffered out-of-hospital cardiac arrest (OHCA).

METHODS

Included in this review are randomized trials assessing the effect of prehospital TH in adult patients suffering nontraumatic OHCA. Trials assessing the effect of in-hospital TH were excluded. Only studies with a low risk of bias were eligible for meta-analysis. A medical librarian searched PubMed, Ovid, EMBASE, Ovid Global Health, the Cochrane Library, Guidelines.gov, EM Association Websites, CenterWatch, IFPMA Clinical Trial Results Portal, CINAHL, ProQuest, and the Emergency Medical Abstracts Database without language restrictions. Clinicaltrials.gov was searched for unpublished studies. Bibliographies were hand searched and experts in the field were queried about other published or unpublished trials. Using standardized forms, two authors independently extracted data from all included trials. Results from high-quality trials were pooled using a random-effects model. Two authors, using the Cochrane risk of bias tool, assessed risk of bias independently.

RESULTS

Of 740 citations, six trials met inclusion criteria. Four trials were at a low risk of bias and were included in the meta-analysis (N=715 patients). Pooled analysis of these trials revealed no difference in overall survival (relative risk [RR]=0.98, 95% CI=0.79 to 1.21) or good neurologic outcome (RR=0.96, 95% CI=0.76 to 1.22) between patients randomized to prehospital TH versus standard therapy. Heterogeneity was low for both survival and neurologic outcome (I2=0).

CONCLUSIONS

Randomized trial data demonstrate no important patient benefit from prehospital initiation of TH. Pending the results of ongoing larger trials, resources dedicated to this intervention may be better spent elsewhere.

Utilization of rapid infusion system with cold saline in the induction of therapeutic hypothermia

OBJECTIVE

To examine the cooling effectiveness of a rapid infusion system (RIS) during induction of therapeutic hypothermia.

METHODS

This laboratory study simulated the effect of three fluid delivery methods: rapid dripping without any other equipment (control); RIS; pressure bag. Cold energy loss (℃ × min) was calculated as: (temperature of the proximal thermoprobe--temperature of the distal thermoprobe) × (total infusion time).

RESULTS

Infusion time was significantly shorter and cold energy loss significantly lower in the RIS group than in the two other groups.

CONCLUSIONS

RIS preserves the cold energy of fluid more effectively than pressure bag or control. RIS allows for rapid infusion at a constant pressure and can be easily applied in an emergency setting.

Comparison of cold crystalloid and colloid infusions for induction of therapeutic hypothermia in a porcine model of cardiac arrest

Introduction

Large-volume cold intravenous infusion of crystalloids has been used for induction of therapeutic hypothermia after cardiac arrest. However, the effectiveness of cold colloids has not been evaluated. Therefore, we performed an experimental study to investigate the cooling effect of cold normal saline compared to colloid solution in a porcine model of ventricular fibrillation.

Methods

Ventricular fibrillation was induced for 15 minutes in 22 anesthetized domestic pigs. After spontaneous circulation was restored, the animals were randomized to receive either 45 ml/kg of 1°C cold normal saline (Group A, 9 animals); or 45 ml/kg of 1°C cold colloid solution (Voluven®, 6% hydroxyethyl starch 130/0.4 in 0.9% NaCl) during 20 minutes (Group B, 9 animals); or to undergo no cooling intervention (Group C, 4 animals). Then, the animals were observed for 90 minutes. Cerebral, rectal, intramuscular, pulmonary artery, and subcutaneous fat body temperatures (BT) were recorded. In the mechanical ex-vivo sub study we added a same amount of cold normal saline or colloid into the bath of normal saline and calculated the area under the curve (AUC) for induced temperature changes.

Results

Animals treated with cold fluids achieved a significant decrease of BT at all measurement sites, whereas there was a consistent significant spontaneous increase in group C. At the time of completion of infusion, greater decrease in pulmonary artery BT and cerebral BT in group A compared to group B was detected (−2.1 ± 0.3 vs. -1.6 ± 0.2°C, and −1.7 ± 0.4 vs. -1.1 ± 0.3°C, p < 0.05, respectively). AUC analysis of the decrease of cerebral BT revealed a more vigorous cooling effect in group A compared to group B (−91 ± 22 vs. -68 ± 23°C/min, p = 0.046). In the mechanical sub study, AUC analysis of the induced temperature decrease of cooled solution revealed that addition of normal saline led to more intense cooling than colloid solution (−7155 ± 647 vs. -5733 ± 636°C/min, p = 0.008).

Conclusions

Intravenous infusion of cold normal saline resulted in more intense decrease of cerebral and pulmonary artery BT than colloid infusion in this porcine model of cardiac arrest. This difference is at least partially related to the various specific heat capacities of the coolants.

Out-of-hospital cardiac arrest: 10 years of progress in research and treatment

Cardiac disease is the most common cause of mortality in Western countries, with most deaths due to out-of-hospital cardiac arrest (OHCA). In Sweden, 5000-10 000 OHCAs occur annually. During the last decade, the time from cardiac arrest to start of cardiopulmonary resuscitation (CPR) and defibrillation has increased, whereas survival has remained unchanged or even increased. Resuscitation of OHCA patients is based on the 'chain-of-survival' concept, including early (i) access, (ii) CPR, (iii) defibrillation, (iv) advanced cardiac life support and (v) post-resuscitation care. Regarding early access, agonal breathing, telephone-guided CPR and the use of 'track and trigger systems' to detect deterioration in patients' condition prior to an arrest are all important. The use of compression-only CPR by bystanders as an alternative to standard CPR in OHCA has been debated. Based on recent findings, guidelines recommend telephone-guided chest compression-only CPR for untrained rescuers, but trained personnel are still advised to give standard CPR with both compressions and ventilation, and the method of choice for this large group remains unclear and demands for a randomized study. Data have shown the benefit of public access defibrillation for dispatched rescuers (e.g. police and fire fighters) but data are not as strong for the use of automated defibrillators (AEDs) by trained or untrained rescuers. Postresuscitation, use of therapeutic hypothermia, the importance of specific prognostic survival factors in the intensive care unit and the widespread use of percutaneous coronary intervention have all been considered. Despite progress in research and improved treatment regimens, most patients do not survive OHCA. Particular areas of interest for improving survival include (i) identification of high-risk patients prior to their arrest (e.g. early warning symptoms and genes); (ii) increased use of bystander CPR training (e.g. in schools) and simplified CPR techniques; (iii) better identification of high-incidence sites and better recruitment of AEDs (via mobile phone solutions?); (iv) improved understanding of the use of therapeutic hypothermia; (v) determining which patients should undergo immediate coronary angiography on hospital admission; and (vi) clarifying the importance of extracorporeal membrane oxygenation during CPR.

Therapeutic hypothermia application vs standard support care in post resuscitated out-of-hospital cardiac arrest patients

INTRODUCTION

Survival after cardiac arrest remains poor, especially when it occurs outside of hospital. In recent years, therapeutic hypothermia has been used to improve outcomes in patients who have experienced cardiac arrest, however, application to out-of-hospital cardiac arrest (OHCA) patients remains controversial.

METHODS

A total of 175 OHCA patients underwent therapeutic hypothermia (TH), which was performed using large volume ice crystalloid fluid (LVICF) infusions after ICU admission. Ice packs and conventional cooling blankets were used to maintain a core body temperature of 33°C, according to standard protocol for 36 hours. Patients in the control group received standard supportive care without TH. Hospital survival and neurologic outcomes were compared.

RESULTS

There was no significant difference between the groups with regards to patient characteristics, underlying etiologies, and length of hospital stays. The duration of cardiac pulmonary resuscitation (CPR) was also similar. In the 51 patients that received TH, 14 were alive at hospital discharge. In the 124 patients belonging to the supportive care group, only 15 were alive at hospital discharge (27.5% vs. 12.1%, p = 0.013). Approximately 7.9% of patients in the TH group had good neurologic outcomes (4 of 51) compared with the 1.7% (2 of 124) of patients in the supportive group (p = 0.04). There were no specific treatment-related complications.

CONCLUSION

Therapeutic hypothermia can be safely applied to OHCA patients and can improve their outcome. Further large scale studies are needed to verify our results.

[Post-resuscitation syndrome. Role of inflammation after cardiac arrest]

Cardiac arrest with subsequent cardiopulmonary resuscitation causes an ischemic reperfusion syndrome of the whole body resulting in localized damage of particularly sensitive organs, such as the brain and heart, together with systemic sequelae. The main factor is a generalized activation of inflammatory reactions resulting in symptoms similar in many aspects to those of sepsis. Systemic inflammation strengthens organ damage due to disorders in the macrocirculation and microcirculation due to metabolic imbalance as well as the effects of direct leukocyte transmitted tissue destruction. The current article gives an overview on the role of inflammation following cardiac arrest and presents in detail the underlying mechanisms, the clinical symptoms and possible therapeutic approaches.

Crystalloid vs. hypertonic crystalloid-colloid solutions for induction of mild therapeutic hypothermia after experimental cardiac arrest

PURPOSE

To compare cerebral and hemodynamic consequences of different volumes of cold acetated Ringer's solution or cold hypertonic saline dextran administered in order to achieve mild hypothermia after cardiac arrest (CA) in a pig model of experimental cardiopulmonary resuscitation (CPR).

METHODS

Using an experimental pig model of 12 min CA (followed by 8 min CPR or no resuscitation) we compared four groups of piglets: a control group, a normothermic group and two groups with different solutions administered for induction of hypothermia. The control group of 5 piglets underwent 12 min CA without subsequent CPR, after which the brain of the animals was removed immediately. After restoration of spontaneous circulation (ROSC) the resuscitated piglets were randomized into a normothermic group (NT group=10), and two hypothermic groups that received cold infusions of either 30 mL/kg acetated Ringer's solution (Much fluid group, M, n=10) or 3mL/kg hypertonic saline dextran solution (Less fluid group, L, n=10), respectively, administered during 30 min. Additional external cooling with ice packs was used in hypothermic groups. Sixty or 180min after ROSC the experiment was terminated. Immediately after arrest the brain was removed for histological analyses.

RESULTS

The median time to reach the target core temperature of 34 °C after ROSC was 51.5±7.8 min in L group and 48.8±8.6 min in M group. Less cerebral tissue content of water (p<0.001), sodium (p<0.0001), potassium (p<0.0001) and less central venous pressure (CVP) at 5 and 15 min after ROSC were demonstrated in L group. Increased brain damage was demonstrated over time in NT group (p<0.001). Less neurologic damage and BBB disruptions (albumin leakage) was observed at 180min in M group in comparison with both NT and L groups (p<0.001).

CONCLUSION

No statistical differences were observed between the hypothermic groups in the time to achieve mild hypothermia. Although inclusion of cold hypertonic crystalloid-colloidal solutions in the early resuscitation after ROSC may be more effective than cold crystalloids in reducing brain edema, this study demonstrates that mild hypothermia induced with small volumes of cold hypertonic crystalloid-colloids is less as effective as crystalloid's induced hypothermia in mitigating brain injury after cardiac arrest.

Management of the post-cardiac arrest syndrome

BACKGROUND

Recent advances in resuscitation science have revolutionized care of the cardiac arrest patient. Dramatic departures from time-honored advanced cardiac life support therapies, such as cardiocerebral resuscitation and bundled post-arrest care, have given rise to a new paradigm of resuscitation practices, which has boosted the rate of neurologically intact survival.

OBJECTIVES

This article reviews the pathophysiology of the post-cardiac arrest syndrome, the collective pathophysiology after return of spontaneous circulation, and presents management pearls specifically for the emergency physician. This growing area of scientific inquiry must be managed appropriately to sustain improved outcomes.

DISCUSSION

The emergency physician must understand this pathophysiology, manage resuscitated patients according to the latest evidence, and coordinate with appropriate inpatient resources.

CONCLUSION

The new approach to cardiac arrest care is predicated on a chain of survival that spans the spectrum of care from the prehospital arena through the emergency, intensive, and inpatient settings. The emergency physician is a crucial link in this chain.

Can a Cold (4°C) IV Fluid Bolus to Induce Therapeutic Hypothermia Really Deliver 4°C to Children?

Induced therapeutic hypothermia after pediatric cardiac arrest is under investigation. Animal and adult data suggest that rapid achievement of temperatures (T) <34°C may improve outcomes. Cold intravenous fluids (IVF) rapidly induce hypothermia in adults. We sought to evaluate the actual T of IVF entering a pediatric simulated model when a 4°C 30 mL/kg normal saline bolus was infused at standard rates. At ambient T 25°C, T probes were placed in 4°C 1 L normal saline bags (Tbag) and at distal tip infusion tubing at simulated patient entry (Tin). Simultaneous Tbag and Tin were recorded every 15 seconds during infusion. About 30 mL/kg was infused by pressure bag over 30 minutes for 10 kg (300 mL at 10 mL/min), 25 kg (750 mL at 25 mL/min), and 65 kg (2000 mL at 67 mL/min) patients. Tests were run in duplicate. For 10 kg, Tbag was 6.4°C±1.1°C and Tin was 17°C±0.9°C. For 25 kg, Tbag was 7°C±1.4°C and Tin was 12°C±1.2°C. For 65 kg, Tbag was 5.8°C±1.6°C and Tin was 8.6°C±1.7°C. Tbag<Tin for all three simulated patient sizes (p<0.01). ΔT (10.6°C±1.8°C) was largest for 10 kg and smallest for 65 kg (2.8°C±1.7°C) simulated patients (p<0.01), confirming that ΔT is infusion rate dependent. Using simulations of cold IVF boluses to induce therapeutic hypothermia, we found that infusion rates and techniques influence T gradient from fluid bag to patient entry. We speculate that alternative techniques may be needed if 4°C IVF boluses are used to induce therapeutic hypothermia in small children.

Induction and maintenance of therapeutic hypothermia after pediatric cardiac arrest: efficacy of a surface cooling protocol

OBJECTIVE

To assess the feasibility, effectiveness, side effects, and adverse events associated with a standardized surface cooling protocol. Induced therapeutic hypothermia after pediatric cardiac arrest is an important intervention.

DESIGN

Prospective intervention trial.

SETTING

Urban, tertiary care children's hospital.

PATIENTS

Twelve pediatric cardiac arrest survivors.

INTERVENTIONS

Standardized surface cooling protocol.

MEASUREMENTS AND MAIN RESULTS

Patients (age: median, 1.5 yrs; interquartile range, 0.5-6.25; cardiopulmonary resuscitation duration: median, 18 mins; interquartile range, 10-45) were cooled by a standard surface cooling protocol for rapid induction and maintenance of goal rectal temperature (T) 32°C-34°C for 24 hrs, with prospectively defined rescue protocols. Side effects and clinical interventions were recorded. Median time to rectal T ≤34°C was 1.5 (1, 1.5) hrs from cooling initiation and 6 (5, 6.5) hrs from arrest. T was documented every 30 mins. Maintenance target T 32°C-34°C was attained in 78% (414 of 531) of measurements, overshoot hypothermia <32°C in 15% (81 of 531), and overshoot hyperthermia >34°C in 7% (36 of 531). Mean bias between rectal vs. esophageal T was -0.42°C (95% confidence interval, -0.49 to -0.35), and between rectal and bladder T was 0.16°C (95% confidence interval, 0.11-0.22). Side effects observed included: hypokalemia <3.0 mEq/L in 67% of patients and bradycardia <2% for age in 58%. There were no episodes of bleeding or ventricular tachyarrhythmia that required treatment. Six (50%) of 12 patients survived to discharge.

CONCLUSIONS

A standard surface cooling protocol achieved rapid induction of hypothermia after pediatric cardiac arrest. During maintenance of hypothermia, 78% of measures were within target T 32°C-34°C. Commonly employed temperature sites (esophageal, rectal, and bladder) were similar. Overshoot hypothermia and associated side effects were common, but there were no serious adverse events attributable to induced therapeutic hypothermia in this case series. Surface cooling protocols to induce and maintain therapeutic hypothermia after pediatric cardiac arrest are potentially feasible.

Regional impact of cardiac arrest center criteria on out-of-hospital transportation practices

BACKGROUND

Cardiac arrest center (CAC) criteria are not well defined, nor is their potential impact on current emergency medical services (EMS) transportation practices for post-cardiac arrest (PCA) patients. In addition to the availability of emergent cardiac catheterization (CATH) and therapeutic hypothermia (TH), high-volume centers and those with PCA protocols have been associated with improved outcomes. Objectives. This study aimed 1) to identify the PCA treatment capabilities of receiving hospitals in a 10-county regional EMS system without official CAC designation and 2) to determine the proportion of PCA patients who are transported to hospitals meeting three proposed CAC definitions. We hypothesized that a majority of patients are already transported to hospitals that meet proposed CAC criteria.

METHODS

We distributed a survey to 34 receiving hospitals to determine availability and volume of CATH, TH, a PCA protocol, and a 24-hour intensivist. We conducted a retrospective study of adult, nontrauma cardiac arrest patients transported with a pulse from 2006 to 2008 for 16 EMS agencies. The proportions of patients transported to hospitals meeting three CAC criteria were compared: criteria A (availability of CATH and TH), criteria B (criteria A, >200 CATHs per year, and a PCA protocol), and criteria C (criteria B and a 24-hour intensivist).

RESULTS

Data were obtained from 31 of 34 hospitals (91.1%), of which 10 (32.3%) met criteria A, seven (22.6%) met criteria B, and six (19.4%) met criteria C. Of 1,193 cardiac arrest patients, 46 (3.9%) were excluded because of transport to a pediatric, closed, or out-of-region hospital. There were 335 patients (81.1%) with return of spontaneous circulation and a pulse present upon arrival at the destination facility transported to hospitals meeting criteria A, 304 patients (73.6%) transported to hospitals meeting criteria B, and 273 patients (66.1%) transported to hospitals meeting criteria C.

CONCLUSIONS

In a region without official CAC designation, only one-third of hospitals meet basic CAC criteria (CATH and TH), but those facilities receive 81% of PCA patients. Fewer patients (66%) are transported to hospitals meeting more stringent CAC criteria. These data describe the potential impact of developing a CAC policy based on current transportation practices.

The role of hypothermia in post-cardiac arrest patients with return of spontaneous circulation: a systematic review

OBJECTIVES

To update a comprehensive systematic review of the use of therapeutic hypothermia after cardiac arrest that was undertaken initially as part of the 2010 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science. The specific question addressed was: 'in post-cardiac arrest patients with a return of spontaneous circulation, does the induction of mild hypothermia improve morbidity or mortality when compared with usual care?'

METHODS

Pubmed was searched using ("heart arrest" or "cardiopulmonary resuscitation") AND "hypothermia, induced" using 'Clinical Queries' search strategy; EmBASE was searched using (heart arrest) OR (cardiopulmonary resuscitation) AND hypothermia; The Cochrane database of systematic reviews; ECC EndNote Library for "hypothermia" in abstract OR title. Excluded were animal studies, reviews and editorials, surveys of implementation, analytical models, reports of single cases, pre-arrest or during arrest cooling and group where the intervention was not hypothermia alone.

RESULTS

77 studies met the criteria for further review. Of these, four were meta-analyses (LOE 1); seven were randomised controlled trials (LOE 1), although six of these were from the same set of patients; nine were non-randomised, concurrent controls (LOE 2); 15 were trials with retrospective controls (LOE 3); 40 had no controls (LOE 4); and one was extrapolated from a non-cardiac arrest group (LOE 5).

CONCLUSION

There is evidence supporting the use of mild therapeutic hypothermia to improve neurological outcome in patients who remain comatose following the return of spontaneous circulation after a cardiac arrest; however, much of the evidence is from low-level, observational studies. Of seven randomised controlled trials, six use data from the same patients.

Intraosseous infusion of ice cold saline is less efficacious than intravenous infusion for induction of mild therapeutic hypothermia in a swine model of cardiac arrest

BACKGROUND

Intravenous (IV) infusion of ice cold saline is an effective method to initiate induction of mild therapeutic hypothermia (MTH) following resuscitation from out-of-hospital cardiac arrest (OOHCA). Intraosseous (IO) infusion of cold saline may be an alternative method to induce MTH.

OBJECTIVE

The goal of this study was to determine if IO infusion of cold saline is a comparable alternative to IV infusion for inducing MTH in a laboratory swine model of cardiac arrest.

METHODS

Ten mixed breed swine were resuscitated from cardiac arrest and randomized post-resuscitation to infusion with ice cold saline using either IO (n = 5) or IV (n = 5) access. The study endpoints were either a goal esophageal temperature of 34 °C or the elapse of a 30 min time period, simulating a long prehospital transport.

RESULTS

Four of five pigs in the IV infusion group achieved goal temperature within 30 min compared to 0/5 in the IO infusion group (p = 0.048). The mean esophageal temperature change was significantly higher in the IV group when compared to the IO group (p < 0.001). Post-arrest hemodynamic parameters were similar between the two groups.

CONCLUSIONS

IV infusion of ice cold saline is an efficacious method to achieve MTH in this swine model of cardiac arrest. Furthermore, IO infusion of cold saline is not sufficient to induce MTH in the time routinely available in the prehospital setting following OOHCA.

Pre-hospital cooling of patients following cardiac arrest is effective using even low volumes of cold saline

Introduction

Pre-hospital induction of therapeutic mild hypothermia (TH) may reduce post-cardiac arrest brain injury in patients resuscitated from out-of-hospital cardiac arrest. Most often, it is induced by a rapid intravenous administration of as much as 30 ml/kg of cold crystalloids. We decided to assess the pre-hospital cooling effectivity of this approach by using a target dose of 15-20 ml/kg of 4°C cold normal saline in the setting of the physician-staffed Emergency Medical Service. The safety and impact on the clinical outcome have also been analyzed.

Methods

We performed a prospective observational study with a retrospective control group. A total of 40 patients were cooled by an intravenous administration of 15-20 ml/kg of 4°C cold normal saline during transport to the hospital (TH group). The pre-hospital decrease of tympanic temperature (TT) was analyzed as the primary endpoint. Patients in the control group did not undergo any pre-hospital cooling.

Results

In the TH group, administration of 12.6 ± 6.4 ml/kg of 4°C cold normal saline was followed by a pre-hospital decrease of TT of 1.4 ± 0.8°C in 42.8 ± 19.6 min (p < 0.001). The most effective cooling was associated with a transport time duration of 38-60 min and with an infusion of 17 ml/kg of cold saline. In the TH group, a trend toward a reduced need for catecholamines during transport was detected (35.0 vs. 52.5%, p = 0.115). There were no differences in demographic variables, comorbidities, parameters of the cardiopulmonary resuscitation and in other post-resuscitation characteristics. The coupling of pre-hospital cooling with subsequent in-hospital TH predicted a favorable neurological outcome at hospital discharge (OR 4.1, CI95% 1.1-18.2, p = 0.046).

Conclusions

Pre-hospital induction of TH by the rapid intravenous administration of cold normal saline has been shown to be efficient even with a lower dose of coolant than reported in previous studies. This dose can be associated with a favorable impact on circulatory stability early after the return of spontaneous circulation and, when coupled with in-hospital continuation of cooling, can potentially improve the prognosis of patients.

Trial Registration

ClinicalTrials (NCT): NCT00915421

Postresuscitation care: entering a new era

PURPOSE OF REVIEW

The purpose of this study is to discuss recent data relating to the treatment of cardiac arrest survivors. This is a rapidly evolving component of resuscitation medicine that impacts significantly on the quality of survival after cardiac arrest.

RECENT FINDINGS

The postcardiac arrest syndrome comprises postcardiac arrest brain injury, postcardiac arrest myocardial dysfunction, the systemic ischaemia/reperfusion response, and the persistent precipitating disease. Primary percutaneous coronary intervention is the preferred method for restoring coronary perfusion when cardiac arrest has been caused by an ST-elevation myocardial infarction. Many cardiac arrest survivors with non-ST-elevation myocardial infarction may also benefit from urgent percutaneous coronary intervention. Comatose cardiac arrest survivors should be managed with a moderate blood glucose target range of below 10 mmol/l (180 mg/dl). Therapeutic hypothermia is now generally accepted as part of a treatment strategy for comatose survivors of cardiac arrest, but its use may render conventional methods of prognostication unreliable.

SUMMARY

Survivors from cardiac arrest develop a postcardiac arrest syndrome. Postresuscitation care, including primary percutaneous coronary intervention, therapeutic hypothermia, and control of blood sugar, improves survival and neurological outcome in cardiac arrest survivors. Completely reliable prognostication in comatose survivors of cardiac arrest is difficult to achieve.

Feasibility of intra-arrest hypothermia induction: A novel nasopharyngeal approach achieves preferential brain cooling

AIM

In patients with cardiopulmonary arrest, brain cooling may improve neurological outcome, especially if applied prior to or during early reperfusion. Thus it is important to develop feasible cooling methods for pre-hospital use. This study examines cerebral and compartmental thermokinetic properties of nasopharyngeal cooling during various blood flow states.

METHODS

Ten swine (40+/-4kg) were anesthetized, intubated and monitored. Temperature was determined in the frontal lobe of the brain, in the aorta, and in the rectum. After the preparatory phase the cooling device (RhinoChill system), which produces evaporative cooling in the nasopharyngeal area, was activated for 60min. The thermokinetic response was evaluated during stable anaesthesia (NF, n=3); during untreated cardiopulmonary arrest (ZF, n=3); during CPR (LF, n=4).

RESULTS

Effective brain cooling was achieved in all groups with a median cerebral temperature decrease of -4.7 degrees C for NF, -4.3 degrees C for ZF and -3.4 degrees C for LF after 60min. The initial brain cooling rate however was fastest in NF, followed by LF, and was slowest in ZF; the median brain temperature decrease from baseline after 15min of cooling was -2.48 degrees C for NF, -0.12 degrees C for ZF, and -0.93 degrees C for LF, respectively. A median aortic temperature change of -2.76 degrees C for NF, -0.97 for LF and +1.1 degrees C for ZF after 60min indicated preferential brain cooling in all groups.

CONCLUSION

While nasopharyngeal cooling in swine is effective at producing preferential cerebral hypothermia in various blood flow states, initial brain cooling is most efficient with normal circulation.

Augmentation of the cooling capacity of refrigerated fluid by minimizing heat gain of the fluid using a simple method of cold insulation

OBJECTIVES

This study was undertaken to determine how rapidly refrigerated fluids gain heat during bolus infusion and to determine whether the refrigerated fluids could be kept cold by a simple cold-insulation method.

METHODS

One liter of refrigerated fluid was run through either a 16-gauge catheter (16G(-) and 16G(+) groups) or an 18-gauge catheter (18G(-) and 18G(+) groups) while monitoring the temperature in the fluid bag and the outflow site. In the 16G(+) and the 18G(+) groups, the fluid bag was placed with an ice pack inside an insulating sleeve during the fluid run.

RESULTS

In the 16G(-) and the 18G(-) groups, the outflow temperature increased to 10-12 degrees C during the fluid run. Meanwhile, outflow temperatures in the 16G(+) and the 18G(+) groups remained below 4.6 and 6.8 degrees C, respectively. The temperatures differed significantly between the 16G(-) and the 16G(+) groups (p < 0.001) and between the 18G(-) and the 18G(+) groups (p < 0.001), respectively.

CONCLUSIONS

Substantial heat gain occurred in the refrigerated fluid even during the relatively short duration of bolus infusion. The heat gain could, however, be easily minimized by cold insulation of the fluid bag.

Surface cooling for rapid induction of mild hypothermia after cardiac arrest: design determines efficacy

OBJECTIVES

Recently, a novel cooling pad was developed for rapid induction of mild hypothermia after cardiac arrest. The aim of this study was to evaluate the cooling efficacy of three different pad designs for in-hospital cooling.

METHODS

Included in this prospective interventional study were patients with esophageal temperature (Tes) > 34 degrees C on admission. The cooling pad consists of multiple cooling units, filled with a combination of graphite and water, which is precooled to -18 degrees C (design A) or to -9 degrees C (designs B and C) before use. The designs of the cooling pad differed in number, shape, and thickness of the cooling units, with weights of 9.7 kg (design A), 5.3 kg (design B), and 6.2 kg (design C). All three designs were tested in sequential order and were changed according to the results found in the previous trial. Cooling was started after admission until Tes = 34 degrees C, when the cooling pad was removed. The target temperature of Tes = 32-34 degrees C was maintained for 24 hours. Data are presented as medians and interquartile ranges (IQRs = 25%-75%) or proportions.

RESULTS

Cooling rates were 3.4 degrees C/hour (IQR = 2.5-3.7) with design A (n = 12), 2.8 degrees C/hour (IQR = 1.6-3.3) with design B (n = 7), and 2.9 degrees C/hour (IQR = 1.9-3.6) with design C (n = 10; p = 0.5). To reach 34 degrees C, the cooling pad had to be exchanged with a new one due to melting and therefore depleting cooling capacity in three patients with design A, in five patients with design B, and in no patient with design C (p = 0.004).

CONCLUSIONS

With adequate design and storage temperature, the cooling pad proved to be efficient for rapid in-hospital cooling of patients resuscitated from cardiac arrest.

Therapeutic hypothermia: implications for acute care practitioners

The use of therapeutic hypothermia (TH) in acute care medicine has evolved over the past 2 centuries, and its use over the past decade has increased in emergency departments, intensive care units, and operating rooms. Therapeutic hypothermia has several potential clinical applications based on its putative mechanisms of action. It appears to improve oxygen supply to ischemic areas of the brain and decreases intracranial pressure. Mild-to-moderate TH (33 degrees C +/- 1 degrees C) after resuscitation from cardiac arrest is neuroprotective, and also acts on the cardiovascular system with evidence of a decrease in heart rate and increase in systemic vascular resistance. Therapeutic hypothermia decreases cardiac output by 7% for each 1 degrees C decrease in core body temperature, but maintains the stroke volume and the mean arterial pressure. Despite a growing amount of data, this life-saving technique is underutilized in hospitals worldwide. The purpose of this comprehensive review is to show the evolution and the clinical use of TH as it pertains to acute care practitioners.

Therapeutic hypothermia after cardiac arrest - implementation in UK intensive care units

A telephone survey was carried out to determine how many United Kingdom intensive care units were using therapeutic hypothermia as part of their management of unconscious patients admitted after cardiac arrest. All 247 intensive care units listed in the 2008 Directory of Critical Care Services were contacted to determine how many units were using hypothermia as part of their post-cardiac arrest management and how it was implemented. We obtained information from 243 (98.4%) of the intensive care units. At the time of the study, 208 (85.6%) were using hypothermia as part of post-cardiac arrest management. There has been a steady increase annually in the number of units performing therapeutic cooling from 2003 to date, with the majority of units starting in 2007 or 2008. The International Liaison Committee on Resuscitation guidelines, which recommend the use of therapeutic hypothermia for comatose patients following successful resuscitation from cardiac arrest, have taken at least 4-5 years to achieve widespread implementation in the United Kingdom.