Immediate prehospital hypothermia protocol in comatose survivors of out-of-hospital cardiac arrest

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.

Targeted temperature management for adult out-of-hospital cardiac arrest: current concepts and clinical applications

Targeted temperature management (TTM) (primarily therapeutic hypothermia (TH)) after out-of-hospital cardiac arrest (OHCA) has been considered effective, especially for adult-witnessed OHCA with a shockable initial rhythm, based on pathophysiology and on several clinical studies (especially two randomized controlled trials (RCTs) published in 2002). However, a recently published large RCT comparing TTM at 33 °C (TH) and TTM at 36 °C (normothermia) showed no advantage of 33 °C over 36 °C. Thus, this RCT has complicated the decision to perform TH after cardiac arrest. The results of this RCT are sometimes interpreted fever control alone is sufficient to improve outcomes after cardiac arrest because fever control was not strictly performed in the control groups of the previous two RCTs that showed an advantage for TH. Although this may be possible, another interpretation that the optimal target temperature for TH is much lower than 33 °C may be also possible. Additionally, there are many points other than target temperature that are unknown, such as the optimal timing to initiate TTM, the period between OHCA and initiating TTM, the period between OHCA and achieving the target temperature, the duration of maintaining the target temperature, the TTM technique, the rewarming method, and the management protocol after rewarming. RCTs are currently underway to shed light on several of these underexplored issues. In the present review, we examine how best to perform TTM after cardiac arrest based on the available evidence.

The prehospital management of traumatic brain injury

Traumatic brain injury (TBI) is an important cause of death and disability, particularly in younger populations. The prehospital evaluation and management of TBI is a vital link between insult and definitive care and can have dramatic implications for subsequent morbidity. Following a TBI the brain is at high risk for further ischemic injury, with prehospital interventions targeted at reducing this secondary injury while optimizing cerebral physiology. In the following chapter we discuss the prehospital assessment and management of the brain-injured patient. The initial evaluation and physical examination are discussed with a focus on interpretation of specific physical examination findings and interpretation of vital signs. We evaluate patient management strategies including indications for advanced airway management, oxygenation, ventilation, and fluid resuscitation, as well as prehospital strategies for the management of suspected or impending cerebral herniation including hyperventilation and brain-directed hyperosmolar therapy. Transport decisions including the role of triage models and trauma centers are discussed. Finally, future directions in the prehospital management of traumatic brain injury are explored.

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.

Therapeutic mild hypothermia improves early outcomes in rabbits subjected to traumatic uncontrolled hemorrhagic shock

BACKGROUND

Survival benefits of mild hypothermia in animals suffering from uncontrolled hemorrhagic shock (HS) may be influenced by trauma severity. We hypothesized that mild hypothermia would improve early outcomes based on our rabbit model of severe traumatic HS.

MATERIALS AND METHODS

Fifty male New Zealand rabbits weighing between 1.6 and 2.2 kg were randomized into one of the five groups: group 1 (sham), group 2 (37°C/80 mm Hg), group 3 (37°C/40 mm Hg), group 4 (34°C/80 mm Hg), and group 5 (34°C/40 mm Hg). Under urethane anesthesia, animals that suffered fractures and uncontrolled HS received prehospital fluid resuscitation (aggressive or limited) with temperature controlled at normothermia or mild hypothermia, hemostasis, and hospital resuscitation followed by observation.

RESULTS

Mild hypothermia significantly improved cardiac systolic function and decreased lung wet-to-dry weight ratios and total injury score compared with normothermia. Group 5 manifested the best results in lung injury. The decreased base excess and pH and increased lactate levels during HS and limited fluid resuscitation were not exacerbated by mild hypothermia. Electrolytes including potassium and calcium and blood glucose levels as well as coagulation were not significantly influenced after mild hypothermia treatment. Seven-hour survival in the hypothermic groups was higher than that in the normothermic groups, although there was no significant difference in survival between groups 5 and 3.

CONCLUSIONS

Therapeutic mild hypothermia improves early outcomes through improving lung and cardiac performance without causing evident homeostasis disturbances in the rabbit model of traumatic uncontrolled HS. Animals may benefit most under the combination treatment with mild hypothermia and limited fluid resuscitation.

Seasonal variability and influence of outdoor temperature on body temperature of cardiac arrest victims

AIM OF THE STUDY

Mild therapeutic hypothermia is a major advance in post-resuscitation-care. Some questions remain unclear regarding the time to initiate cooling and the time to achieve target temperature below 34 °C. We examined whether seasonal variability of outside temperature influences the body temperature of cardiac arrest victims, and if this might have an effect on outcome.

METHODS

Patients with witnessed out-of-hospital cardiac arrests were enrolled retrospectively. Temperature variables from 4 climatic stations in Vienna were provided from the Central Institute for Meteorology and Geodynamics. Depending on the outside temperature at the scene the study participants were assigned to a seasonal group. To compare the seasonal groups a Student's t-test or Mann-Whitney U test was performed as appropriate.

RESULTS

Of 134 patients, 61 suffered their cardiac arrest during winter, with an outside temperature below 10 °C; in 39 patients the event occurred during summer, with an outside temperature above 20 °C. Comparing the tympanic temperature recorded at hospital admission, the median of 36 °C (IQR 35.3-36.3) during summer differed significantly to winter with a median of 34.9 °C (IQR 34-35.6) (p<0.05). This seasonal alterations in core body temperature had no impact on the time-to-target-temperature, survival rate or neurologic recovery.

CONCLUSION

The seasonal variability of outside temperature influences body temperature of out-of-hospital cardiac arrest victims.

Infusion of 4°C normal saline can improve the neurological outcome in a porcine model of cardiac arrest

BACKGROUND

This study sought to investigate induction of therapeutic hypothermia using ice-cold intravenous fluid after cardiopulmonary resuscitation (CPR). The effects on temperature, hemodynamics, cognitive performance and the accompanying neurohistopathological changes, and apoptosis were assessed.

METHODS

Fourteen piglets had 4 minutes of untreated ventricular fibrillation, followed by CPR. The animals in which spontaneous circulation was restored were randomly assigned to two groups: the hypothermia group (n = 7) was given an infusion of 4°C cold normal saline solution 30 mL/kg at an infusion rate of 1.33 mL/kg/min, followed by 10 mL/kg/h to 4 hours after restoration of spontaneous circulation; the control group (n = 7) was given the same infusion at room temperature. Variables were measured repeatedly until 4 hours after restoration of spontaneous circulation. Neurocognitive performance was evaluated 24 hours after CPR. Then animals were killed and the brains were removed for histopathology at 24 hours after restoration of spontaneous circulation. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling method was used for apoptosis evaluation.

RESULTS

Compared with the control group, the core temperature of the hypothermia group was significantly decreased (p < 0.01). The cerebral performance categories at 24 hours after restoration of spontaneous circulation in the hypothermia group were better than that in the control group (p < 0.05). The percentage of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling-positive cells in the cortex and dentate gyrus of the hippocampus were significantly reduced in the hypothermia group compared with the control group at 24 hours after restoration of spontaneous circulation. By observation of transmission electron microscopy, the neuron damages were significantly reduced in hypothermia group.

CONCLUSION

4°C normal saline solution is a safe and effective method to reduce brain damages and prevent apoptotic cell death after cardiac arrest.

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.

Anesthesia and analgesia protocol during therapeutic hypothermia after cardiac arrest: a systematic review

BACKGROUND

Present practice guidelines recommend sedative-analgesic and neuromuscular blocking administration during therapeutic hypothermia in comatose patients after cardiac arrest. However, none suggests the best administration protocol. In this study, we evaluated intensivists' preferences regarding administration.

METHODS

A systematic literature review was conducted to identify clinical studies published between 1997 and July 2009. Selected articles had to meet the following criteria: use of hypothermia to improve neurologic outcome after cardiac arrest, and specific mention of the sedative protocol used. We checked drugs and dose used, the reason for their administration, and the specific type of neurologic and neuromuscular monitoring used.

RESULTS

We identified 44 studies reporting protocols used in 68 intensive care units (ICUs) from various countries. Midazolam, the sedative used most often, was used in 39 ICUs at doses between 5 mg/h and 0.3 mg/kg/h. Propofol was used in 13 ICUs at doses up to 6 mg/kg/h. Eighteen ICUs (26%) did not report using any analgesic. Fentanyl was the analgesic used the most, in 33 ICUs, at doses between 0.5 and 10 microg/kg/h, followed by morphine in 4 ICUs. Neuromuscular blocking drugs were routinely used to prevent shivering in 54 ICUs and to treat shivering in 8; in 1 ICU, their use was discouraged. Pancuronium was used the most, in 24 ICUs, followed by cisatracurium in 14. Four ICUs used neuromuscular blocking drug administration guided by train-of-four monitoring and 3 ICUs used continuous monitoring of cerebral activity.

CONCLUSIONS

There is great variability in the protocols used for anesthesia and analgesia during therapeutic hypothermia. Very often, the drug and the dose used do not seem the most appropriate. Only 3 ICUs routinely used electroencephalographic monitoring during paralysis. It is necessary to reach a consensus on how to treat this critical care population.

Coma due to cardiac arrest: prognosis and contemporary treatment

Approximately 80% of patients who are successfully resuscitated from cardiac arrest do not regain consciousness immediately after return of spontaneous circulation, and may remain in a coma for hours or weeks, or even be in a persistent vegetative state. Recent investigations have focused on the identification of early clinical characteristics and biomarkers that can reliably predict emergence from coma in those who survive, and on therapies that might improve neurologic outcome from the ischemic brain injury that can be caused by cardiac arrest.

Prehospital therapeutic hypothermia after cardiac arrest--from current concepts to a future standard

Therapeutic hypothermia has been shown to improve survival and neurological outcome after prehospital cardiac arrest. Existing experimental and clinical evidence supports the notion that delayed cooling results in lesser benefit compared to early induction of mild hypothermia soon after return of spontaneous circulation. Therefore a practical approach would be to initiate cooling already in the prehospital setting. The purpose of this review was to evaluate current clinical studies on prehospital induction of mild hypothermia after cardiac arrest. Most reported studies present data on cooling rates, safety and feasibility of different methods, but are inconclusive as regarding to outcome effects.