Field-induced Therapeutic Hypothermia for Neuroprotection after Out-of Hospital Cardiac Arrest: A Systematic Review of the Literature

Implementing a Stepwise Shivering Protocol During Targeted Temperature Management

Background: Shivering is often encountered in patients undergoing targeted temperature management (TTM) after cardiac arrest. The most efficient, safe way to prevent shivering during TTM is not clearly defined. Objective: The purpose of this study was to evaluate the impact of shivering management using a stepwise shivering protocol on time to target temperature (TT), medication utilization and nursing confidence. Methods: Single-center, retrospective chart review of all post-cardiac arrest patients who underwent TTM between 2016 and 2021. The primary outcome is a comparison of time to TT pre- and post-protocol implementation. Secondary objectives compared nursing confidence and medication utilization pre- and post-shivering protocol implementation. Results: Fifty-seven patients were included in the pre-protocol group and thirty-seven were in the post-protocol group. The median (IQR) time to TT was 195 (250) minutes and 165 (170), respectively (p = 0.190). The average doses of acetaminophen was 285 mg pre- vs 1994 mg post- (p <0.001, buspirone 47 mg pre- vs 127 mg post- (p < 0.001), magnesium 0.9 g pre-vs 2.8 g post- (p < 0.001), and fentanyl 1564 mcg pre- vs 2286 mcg post- (p=0.023). No difference was seen for midazolam and cisatracurium. Nurses reported feeling confident with his/her ability to manage shivering during TTM 38.5% of the time pre-protocol compared to 60% post-protocol (p = 0.306). Conclusion: Implementation of a stepwise approach to prevent and treat shivering improved time to TT in our institution, although this finding was not statistically significant. The stepwise protocol supported a reduced amount of high-risk medication use and increased nursing confidence in shivering management.

Pediatric Drowning: A Standard Operating Procedure to Aid the Prehospital Management of Pediatric Cardiac Arrest Resulting From Submersion

OBJECTIVES

Drowning is one of the leading causes of death in children. Resuscitating a child following submersion is a high-pressure situation, and standard operating procedures can reduce error. Currently, the Resuscitation Council UK guidance does not include a standard operating procedure on pediatric drowning. The objective of this project was to design a standard operating procedure to improve outcomes of drowned children.

METHODS

A literature review on the management of pediatric drowning was conducted. Relevant publications were used to develop a standard operating procedure for management of pediatric drowning.

RESULTS

A concise standard operating procedure was developed for resuscitation following pediatric submersion. Specific recommendations include the following: the Heimlich maneuver should not be used in this context; however, prolonged resuscitation and therapeutic hypothermia are recommended.

CONCLUSIONS

This standard operating procedure is a potentially useful adjunct to the Resuscitation Council UK guidance and should be considered for incorporation into its next iteration.

Pre-hospital versus in-hospital initiation of cooling for survival and neuroprotection after out-of-hospital cardiac arrest

BACKGROUND

Targeted temperature management (also known under 'therapeutic hypothermia', 'induced hypothermia'", or 'cooling') has been shown to be beneficial for neurological outcome in patients who have had successful resuscitation from sudden cardiac arrest, but it remains unclear when this intervention should be initiated.

OBJECTIVES

To assess the effects of pre-hospital initiation of cooling on survival and neurological outcome in comparison to in-hospital initiation of cooling for adults with pre-hospital cardiac arrest.

SEARCH METHODS

We searched CENTRAL, MEDLINE, EMBASE, CINAHL, BIOSIS, and three trials registers from inception to 5 March 2015, and carried out reference checking, citation searching, and contact with study authors to identify additional studies.

SELECTION CRITERIA

We searched for randomized controlled trials (RCTs) in adults with out-of-hospital cardiac arrest comparing cooling in the pre-hospital setting to in-hospital cooling. Our primary outcomes were survival and neurological outcome; our secondary outcomes were adverse events, quality of life, and length of stay in the intensive care unit (ICU) and in the hospital.

DATA COLLECTION AND ANALYSIS

We used Cochrane's standard methodological procedures.

MAIN RESULTS

We included seven RCTs (2369 participants randomized) on the induction of pre-hospital cooling in comparison to in-hospital cooling. There was considerable methodological heterogeneity and risk of bias mainly due to deficits in the administration of cooling, therefore we refrained from pooling the results for survival and neurological outcome and we presented the results for each study separately. Adverse events were rare: based on four studies with 1713 adults pre-hospital induction of cooling may increase the risk of cardiac re-arrests. Risk of bias within the seven individual studies was generally moderate. Overall the quality of the evidence was very low. This was mainly driven by inconsistency and low precision.

AUTHORS' CONCLUSIONS

Currently, there is no convincing evidence to clearly delineate beneficial or harmful effects of pre-hospital induction of cooling in comparison to in-hospital induction of cooling. This conclusion is based on very low quality evidence.

Targeted temperature management in brain protection: An evidence-based review

Targeted temperature management (TTM) for neuroprotection involves maintaining the temperature of the brain at predetermined levels by various techniques. It is aimed at avoiding the harmful effects of hyperthermia on the brain and at exploiting the protective effects of lower tissue temperature. There has been an explosion in the use of TTM for neuroprotection in a variety of clinical scenarios apart from the commonly accepted fields of resuscitation and ischaemic, hypoxic encephalopathy. This review briefly discusses the evidence base for TTM. The focus is on various areas of application for neuroprotection, the practical issues pertaining to TTM implementation, the recent data that support it and the present areas of controversy.

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.

Brain resuscitation in the drowning victim

Drowning is a leading cause of accidental death. Survivors may sustain severe neurologic morbidity. There is negligible research specific to brain injury in drowning making current clinical management non-specific to this disorder. This review represents an evidence-based consensus effort to provide recommendations for management and investigation of the drowning victim. Epidemiology, brain-oriented prehospital and intensive care, therapeutic hypothermia, neuroimaging/monitoring, biomarkers, and neuroresuscitative pharmacology are addressed. When cardiac arrest is present, chest compressions with rescue breathing are recommended due to the asphyxial insult. In the comatose patient with restoration of spontaneous circulation, hypoxemia and hyperoxemia should be avoided, hyperthermia treated, and induced hypothermia (32-34 °C) considered. Arterial hypotension/hypertension should be recognized and treated. Prevent hypoglycemia and treat hyperglycemia. Treat clinical seizures and consider treating non-convulsive status epilepticus. Serial neurologic examinations should be provided. Brain imaging and serial biomarker measurement may aid prognostication. Continuous electroencephalography and N20 somatosensory evoked potential monitoring may be considered. Serial biomarker measurement (e.g., neuron specific enolase) may aid prognostication. There is insufficient evidence to recommend use of any specific brain-oriented neuroresuscitative pharmacologic therapy other than that required to restore and maintain normal physiology. Following initial stabilization, victims should be transferred to centers with expertise in age-specific post-resuscitation neurocritical care. Care should be documented, reviewed, and quality improvement assessment performed. Preclinical research should focus on models of asphyxial cardiac arrest. Clinical research should focus on improved cardiopulmonary resuscitation, re-oxygenation/reperfusion strategies, therapeutic hypothermia, neuroprotection, neurorehabilitation, and consideration of drowning in advances made in treatment of other central nervous system disorders.

Core temperature measurement in therapeutic hypothermia according to different phases: comparison of bladder, rectal, and tympanic versus pulmonary artery methods

PURPOSE

Comparisons of bladder, rectal and tympanic temperatures versus pulmonary artery (PA) temperature during different therapeutic hypothermia (TH) phases.

METHODS

Twenty-one patients admitted to our emergency department (ED) after out-of-hospital cardiac arrests were included in this study. For comparison, the temperature of four different sites, urinary bladder (BL), rectal (RE), tympanic membrane (TM) digital thermometers, and a Swan-Ganz catheter were used during TH, which were controlled by a surface cooling method. TH is divided into three phases: induction, maintenance, and rewarming phase.

RESULTS

In the induction phase, the mean differences between PA temperatures and those of the other methods studied were: BL (-0.24 ± 1.30°C), RE (-0.52 ± 1.40°C), and TM (1.11 ± 1.53°C). The mean differences between PA temperatures and those of the other methods in the maintenance phase were BL (0.06 ± 0.79°C), RE (-0.30 ± 1.16°C), and TM (1.12 ± 1.29°C); in the rewarming phase: BL (0.08 ± 0.86°C), RE (-0.03 ± 1.71°C), and TM (0.89 ± 1.62°C); and in the total phase: BL (0.04 ± 0.90°C), RE (-0.22 ± 1.44°C), and TM (1.03 ± 1.47°C).

CONCLUSIONS

The mean difference between BL and PA temperatures is lower than those in other sites during TH. On the contrary, there are larger differences between TM and PA temperatures when compared to other sites. The differences between RE and PA temperatures are comparatively less than those between TM and PA. However, RE temperature tends to be higher than the temperature recorded by a BL thermometer or Swan-Ganz catheter during the rapid induction phase.

Successful resuscitation after multiple injuries in the wilderness

BACKGROUND

Survival of blunt trauma associated with hypothermic and hemorrhagic cardiac arrest in wilderness areas is extremely rare.

CASE REPORT

We describe a case of a 19-year-old female college sophomore who, while glissading down Mt. Adams, had a 400-pound boulder strike her back and left pelvis, propelling her 40 feet down the mountain to land face down in the snow at 7000 feet. It took 4 h from the time of injury until the arrival of the helicopter at our Emergency Department and Trauma Center. The patient lost vital signs en route and had no CO(2) production. A cardiothoracic surgeon was the trauma surgeon on call. The patient was taken directly from the helipad to the operating room, where cutdowns enabled initial intravenous access, median sternotomy and pericardiotomy open heart massage, massive transfusion, chest and abdominal cavity irrigations with warm saline, correction of acid base imbalances and coagulopathies, and epicardial pacing that led to a successful reanimation of the patient. The patient was rewarmed without extracorporeal membrane oxygenation or heat exchangers. The ensuing multiple organ failures (heart, lungs, kidneys, intestines, brain, and immune system) and rhabdomyolysis led to a 2-month intensive care unit stay. She received over 120 units of blood and blood products. The patient regained cognitive function, mobility, and overcame multiple organ failure.

CONCLUSION

This report is presented to increase awareness of the potential survivability in hypothermia, and to recognize the heroic efforts of the emergency services personnel whose efforts saved the patient's life.

Roles of individual prolyl-4-hydroxylase isoforms in the first 24 hours following transient focal cerebral ischaemia: insights from genetically modified mice

This study investigated the function of each of the hypoxia inducible factor (HIF) prolyl-4-hydroxylase enzymes (PHD1–3) in the first 24 h following transient focal cerebral ischaemia by using mice with each isoform genetically suppressed. Male, 8- to 12-week old PHD1−/−, PHD2+/− and PHD3−/− mice and their wild-type (WT) littermate were subjected to 45 min of middle cerebral artery occlusion (MCAO). During the experiments, regional cerebral blood flow (rCBF) was recorded by laser Doppler flowmetry. Behaviour was assessed at both 2 h and 24 h after reperfusion with a common neuroscore. Infarct volumes, blood–brain barrier (BBB) disruption, cerebral vascular density, apoptosis, reactive oxygen species (ROS), HIF1α, and glycogen levels were then determined using histological and immunohistochemical techniques. When compared to their WT littermates, PHD2+/− mice had significantly increased cerebral microvascular density and more effective restoration of CBF upon reperfusion. PHD2+/− mice showed significantly better functional outcomes and higher activity rates at both 2 h and 24 h after MCAO, associated with significant fewer apoptotic cells in the penumbra and less BBB disruption; PHD3−/− mice had impaired rCBF upon early reperfusion but comparable functional outcomes; PHD1−/− mice did not show any significant changes following the MCAO. Production of ROS, HIF1α staining and glycogen content in the brain were not different in any comparison. Life-long genetic inhibition of PHD enzymes produces different effects on outcome in the first 24 h after transient cerebral ischaemia. These need to be considered in optimizing therapeutic effects of PHD inhibitors, particularly when isoform specific inhibitors become available.

Local head and neck cooling leads to hypothermia in healthy volunteers

BACKGROUND

Prehospital cooling of acute stroke patients would be ideal when associated with minor or no side effects. Therefore, we evaluated a cooling cap for the surface of head and cervical regions in awake volunteers.

METHODS

10 healthy volunteers were treated by external cooling for 190 min using a gel-based cooling device. Vital signs, rectal temperature, tympanic temperature, the extent of shivering and individual perception of frostiness and discomfort were measured.

RESULTS

All participants (median age 35 years) successfully completed the treatment and experienced only mild to moderate discomfort. No serious adverse events and no shivering were noticed. There was a significant drop in the tympanic temperature to 34.68°C (difference from baseline: 1.7°C, 95% CI: 0.61-2.7°C, p = 0.001), in the rectal temperature to 36.65°C (difference from baseline: 0.65°C, 95% CI: 0.06-1.2°C, p = 0.019) and in the heart rate (difference from baseline: 15 beats/min, 95% CI: 0.63-30 beats/min, p = 0.035).

CONCLUSION

Treatment with the cooling device was well tolerated by all participants. The technique had measurable effects on core body temperature (rectal) and tympanic temperature (may reflect temperature at the external ear and skin rather than intracranial). It can be considered as a simple therapeutic approach to patients with suspected stroke in the prehospital setting.

Autonomic regulation during mild therapeutic hypothermia in cardiopulmonary resuscitated patients

OBJECTIVE

We investigated whether there are differences in autonomic cardiovascular regulation in resuscitated patients undergoing therapeutic hypothermia (TH) in relation to the clinical outcome.

METHOD

Between 2005 and 2007, 18 consecutive resuscitated patients were enrolled. ECG and blood pressure data were recorded for 48 h during hypothermia and warming up to a body core temperature of 36°C. Autonomic regulation was assessed by applying time, frequency, and non-linear dynamics domain methods from heart rate and blood pressure variability (HRV/BPV) analyses.

RESULTS

Nine patients survived with good neurological recovery, and nine patients died during the ICU stay. In both groups, we found a decreased HRV presented by standard deviation of R-R intervals (sdNN) below 50 ms(2) at each time of measurement. Immediately after recovery to a body core temperature of 36°C, a significant higher HRV was found in survivors compared to non-survivors by means of indices sdNN (40.2 ± 19.5 vs. 10.9 ± 4.1 ms(2), P = 0.01), R-R intervals distribution histogram [shannon] (3.7 ± 0.6 vs. 2.2 ± 0.4, P = 0.008), very low frequency band [VLF] (152.2 ± 99.3 vs. 3.4 ± 1.9, P = 0.001) and the variance of the time series of R-R intervals [Wsdvar] (1.16 ± 0.52 vs. 0.29 ± 0.25, P = 0.02) . A decreased spontaneous BPV was found only among survivors comparing blood pressure characteristics within stable hypothermia to the initial state before hypothermia.

CONCLUSION

Resuscitated patients show a significantly reduced HRV before, during and after TH. Compared to survivors, the non-survivors show a further and significantly decrease of HRV immediately after hypothermia.