Hypothermia after cardiac arrest: a treatment that works

Association between body mass index and clinical outcomes in out-of-hospital cardiac arrest survivors treated with targeted temperature management

BACKGROUND

To determine the impact of body mass index (BMI) on clinical outcomes in out-of-hospital cardiac arrest (OHCA) survivors treated with targeted temperature management (TTM).

METHODS

We conducted a retrospective cohort study of 261 adult OHCA survivors who received complete TTM between January 2011 and December 2018 using data from the Research Patient Database Registry of Partners HealthCare system in Boston. Patients were categorized as underweight (BMI < 18.5 kg/m2), normal weight (BMI = 18.5-24.9 kg/m2), overweight (BMI = 25-29.9 kg/m2), and obese (BMI ≥ 30 kg/m2), according to the World Health Organization classification.

RESULTS

The average BMI was 28.9 ± 7.1 kg/m2. Patients with a higher BMI had higher rates of hypertension and diabetes mellitus, and were more likely to be witnessed on collapse. Patients with lower BMI levels had higher sequential organ failure assessment (SOFA) scores, blood urea nitrogen values, and mild thrombocytopenia rates (platelet count <150 K/μL) after the TTM treatment. The survival to discharge and favorable neurological outcome at discharge were reported in 117 (44.8%) and 76 (29.1%) patients, respectively. The survival at discharge, favorable neurologic outcomes at discharge, length of hospital admission, and the occurrence of acute kidney injury did not significantly differ between the BMI subgroups. In logistic regression model, BMI was not an independent predictor for survival at discharge (adjusted odds ratio 0.945, 95% CI 0.883-1.012, p = 0.108) nor for the favorable neurologic outcome at discharge (adjusted odds ratio 1.022, 95% CI 0.955-1.093, p = 0.528).

CONCLUSION

In OHCA patients treated with TTM, there was no significant difference across BMI subgroups for survival or favorable neurologic outcome at discharge.

The Effect of Prophylactic Anticoagulation with Heparin on the Brain Cells of Sprague-Dawley Rats in a Cardiopulmonary-Cerebral Resuscitation Model

After a cardiac arrest (CA) of 5 to 10 min, a marked activation of blood coagulation occurs and microthrombi are found in the cerebral vessels. These microcirculatory disturbances directly affect the outcome on cardiopulmonary resuscitation (CPR). The purpose of this study was to investigate the effects and potential mechanisms of prophylactic anticoagulation on rat brain cells after cerebral CPR. After setting up an asphyxial CA model, we monitored the basic parameters such as the vitals and survival rate of the rats and assessed the respective neurological deficit (ND) and histological damage (HD) scores of their brain tissues. We, furthermore, investigated the influence of heparin on the expressions of TNF-α, IL-1β, CD40, NF-κB, and HIF-1α after asphyxial CA. The results showed that anticoagulation with heparin could obviously improve the outcome and prognosis of brain ischemia, including improvement of neurological function recovery and prevention of morphological and immunohistochemical injury on the brain, while significantly increasing the success rate of CPR. Treatment with heparin significantly inhibited the upregulation of CD40, NF-κB, and HIF-1α induced by asphyxial CA. Thrombolysis treatment may improve the outcome and prognosis of CPR, and future clinical studies need to evaluate the efficacy of early heparin therapy after CA.

Number of Prehospital Defibrillation Shocks and the Return of Spontaneous Circulation in Out-of-Hospital Cardiac Arrest

OBJECTIVE

It has not been determined yet whether the number of defibrillation shocks delivered over the first 30 min of cardiopulmonary resuscitation (CPR) impacts the rate of successful return of spontaneous circulation (ROSC) in out-of-hospital cardiac arrest (OHCA).

METHODS

We conducted a retrospective observational study in non-traumatic OHCA. Patients who were administered defibrillation shocks using a public automated external defibrillator (AED) were consecutively enrolled in the study. We assessed the relationship between ROSC and the number of prehospital defibrillation shocks and constructed an receiver operating characteristic (ROC) curve to illustrate the ability of repeated defibrillation shocks to predict ROSC over the first 30 min of CPR.

RESULTS

Increasing the number of defibrillation shocks progressively decreased the probability to achieve ROSC. The highest rate of ROSC (33%) was observed when four shocks were delivered. The ROC curve illustrated that the fourth shock maximised sensitivity and specificity (area under the curve [AUC]=0.72). The positive and negative predictive values for ROSC reached 82% and 48%, respectively, when <4 shocks were delivered.

CONCLUSION

The delivery of four defibrillation shocks in OHCA most related to ROSC. The evaluation of the number of delivered shock during the first 30 min of CPR is a simple tool that can be used for an early decision in OHCA patient.

Cyanide: critical issues in diagnosis and treatment

The concern of a terrorist attack using cyanide, as well as the gradual awareness of cyanide poisoning in fire victims, has resulted in a renewed interest in the diagnosis and treatment of cyanide poisoning. The formerly academic presentation of cyanide poisoning must be replaced by more useful knowledge, which will allow emergency physicians and rescue workers to strongly suspect cyanide poisoning at the scene. Human cyanide poisonings may result from exposure to cyanide, its salts, or cyanogenic compounds, while residential fires are the most common condition of exposure. In fire victims, recognition of the cyanide toxidrome has been hampered by the short half-life in blood and poor stability of cyanide. In contrast, carboxyhemoglobin, as a marker of carbon monoxide poisoning, is easily measured and long-lasting. No evidence supports the assumption of the arbitrary fixed lethal thresholds of 50% for carboxyhemoglobin, and 3 mg/L for cyanide, in fire victims. Preliminary data, drawn when comparing pure carbon monoxide and pure cyanide poisonings, suggest that a cyanide toxidrome can be defined considering signs and symptoms induced by cyanide and carbon monoxide, respectively. Prospective studies in fire victims may provide value in clarifying signs and symptoms related to both toxicants. Cyanide can induce a lifethreatening poisoning from which a full recovery is possible. A number of experimentally efficient antidotes to cyanide exist, whose clinical use has been hampered due to serious side effects. The availability of potentially safer antidotes unveils the possibility of their value as first-line treatment, even in a complex clinical situation, where diagnosis is rapid and presumptive.

Infusion of solutions of pre-irradiated components in rats

INTRODUCTION

The objective of this study was to conduct a 14-day toxicology assessment for intravenous solutions prepared from irradiated resuscitation fluid components and sterile water.

METHODS

Healthy Sprague Dawley rats (7-10/group) were instrumented and randomized to receive one of the following Field IntraVenous Resuscitation (FIVR) or commercial fluids; Normal Saline (NS), Lactated Ringer's, 5% Dextrose in NS. Daily clinical observation, chemistry and hematology on days 1,7,14, and urinalysis on day 14 were evaluated for equivalence using a two sample t-test (p<0.05). A board-certified pathologist evaluated organ histopathology on day 14.

RESULTS

Equivalence was established for all observation parameters, lactate, sodium, liver enzymes, creatinine, WBC and differential, and urinalysis values. Lack of equivalence for hemoglobin (p=0.055), pH (p=0.0955), glucose (p=0.0889), Alanine-Aminotransferase (p=0.1938), albumin (p=0.1311), and weight (p=0.0555, p=0.1896), was deemed not clinically relevant due to means within physiologically normal ranges. Common microscopic findings randomly distributed among animals of all groups were endocarditis/myocarditis and pulmonary lesions.

DISCUSSION

These findings are consistent with complications due to long-term catheter use and suggest no clinically relevant differences in end-organ toxicity between animals infused with FIVR versus commercial fluids.

Blood glucose level and outcome after cardiac arrest: insights from a large registry in the hypothermia era

INTRODUCTION

The influence of blood glucose (BG) level during the post-resuscitation period after out-of-hospital cardiac arrest (OHCA) is still debated. To evaluate the relationship between blood glucose level and outcome, we included the median glycemia and its maximal amplitude over the first 48 h following ICU admission in an analysis of outcome predictors.

METHODS

We conducted a database study in a cardiac arrest center in Paris, France. Between 2006 and 2010, we included 381 patients who were all resuscitated from an OHCA. A moderate glycemic control was applied in all patients. The median glycemia and the largest change over the first 48 h were included in a multivariate analysis that was performed to determine parameters associated with a favorable outcome.

RESULTS

Of the 381 patients, 136 (36 %) had a favorable outcome (CPC 1-2). Median BG level was 7.6 mmol/L (6.3-9.8) in patients with a favorable outcome compared to 9.0 mmol/L (IQR 7.1-10.6) for patients with an unfavorable outcome (p < 0.01). Median BG level variation was 7.1 (4.2-11) and 9.6 (5.9-13.6) mmol/L in patients with and without a favorable outcome, respectively (p < 0.01). In multivariate analysis, an increased median BG level over the first 48 h was found to be an independent predictor of poor issue [OR = 0.43; 95 % CI (0.24-0.78), p = 0.006]. Finally a progressive increase in median BG level was associated with a progressive increase in the proportion of patients with a poor outcome.

CONCLUSION

We observed a relationship between high blood glucose level and outcome after cardiac arrest. These results suggest the need to test a strategy combining both control of glycemia and minimization of glycemic variations for its ability to improve post-resuscitation care.

Invasive versus noninvasive cooling after in- and out-of-hospital cardiac arrest

Pittl U, Schratter A, Desch S et al. Invasive versus non-invasive cooling after in- and out-of-hospital cardiac arrest: a randomized trial. Clin. Res. Cardiol. 102(8), 607–614 (2013). Therapeutic hypothermia is the cornerstone of the postcardiac arrest period management. Several methods may be used as external or internal cooling. Pittl et al. reported a randomized, prospective, single-center study evaluating an invasive (Coolgard®) versus a non-invasive (Arctic Sun®) cooling method after cardiac arrest in 80 patients in Germany. The neurological outcome and neuron-specific enolase level were not different in the two groups at 72 h after cardiac arrest. The efficacy of the two cooling methods were similar. This study underlines the fact that the type of cooling method is not the most important thing to consider in therapeutic hypothermia, but the need of a progressive and soft rewarming may make the difference in the future between different devices.

Factors predicting the use of therapeutic hypothermia and survival in unconscious out-of-hospital cardiac arrest patients admitted to the ICU

INTRODUCTION

Therapeutic hypothermia (TH) after out-of-hospital cardiac arrest (OHCA) was adopted early in Norway. Since 2004 the general recommendation has been to cool all unconscious OHCA patients treated in the intensive care unit (ICU), but the decision to cool individual patients was left to the responsible physician. We assessed factors that were associated with use of TH and predicted survival.

METHOD

We conducted a retrospective observational study of prospectively collected cardiac arrest and ICU registry data from 2004 to 2008 at three university hospitals.

RESULTS

A total of 715 unconscious patients older than 18 years of age, who suffered OHCA of both cardiac and non-cardiac causes, were included. With an overall TH use of 70%, the survival to discharge was 42%, with 90% of the survivors having a favourable cerebral outcome. Known positive prognostic factors such as witnessed arrest, bystander cardio pulmonary resuscitation (CPR), shockable rhythm and cardiac origin were all positive predictors of TH use and survival. On the other side, increasing age predicted a lower utilisation of TH: Odds Ratio (OR), 0.96 (95% CI, 0.94 to 0.97); as well as a lower survival: OR 0.96 (95% CI, 0.94 to 0.97). Female gender was also associated with a lower use of TH: OR 0.65 (95% CI, 0.43 to 0.97); and a poorer survival: OR 0.57 (95% CI, 0.36 to 0.92). After correcting for other prognostic factors, use of TH remained an independent predictor of improved survival with OR 1.91 (95% CI 1.18-3.06; P <0.001). Analysing subgroups divided after initial rhythm, these effects remained unchanged for patients with shockable rhythm, but not for patients with non-shockable rhythm where use of TH and female gender lost their predictive value.

CONCLUSIONS

Although TH was used in the majority of unconscious OHCA patients admitted to the ICU, actual use varied significantly between subgroups. Increasing age predicted both a decreased utilisation of TH as well as lower survival. Further, in patients with a shockable rhythm female gender predicted both a lower use of TH and poorer survival. Our results indicate an underutilisation of TH in some subgroups. Hence, more research on factors affecting TH use and the associated outcomes in subgroups of post-resuscitation patients is needed.

Invasive versus non-invasive cooling after in- and out-of-hospital cardiac arrest: a randomized trial

INTRODUCTION

Mild induced hypothermia (MIH) is indicated for comatose survivors of sudden cardiac arrest (SCA) to improve clinical outcome. In this study, we compared the efficacy of two different cooling devices for temperature management in SCA survivors.

METHODS

Between April 2008 and August 2009, 80 patients after survived in-hospital (IHCA) and out-of-hospital cardiac arrest (OHCA) were included in this prospective, randomized, single center study. Hypothermia was induced after randomization by either invasive Coolgard(®) cooling or non-invasive ArcticSun(®) surface cooling at 33.0 °C core body temperature for 24 h followed by active rewarming. The primary endpoint was defined as the efficacy of both cooling systems, measured by neuron-specific enolase (NSE) levels as a surrogate parameter for brain damage. Secondary efficacy endpoints were the clinical and neurological outcome, time to start of cooling and reaching the target temperature, target temperature-maintenance and hypothermia-associated complications.

RESULTS

NSE at 72 h did not differ significantly between the 2 groups with 16.5 ng/ml, interquartile range 11.8-46.5 in surface-cooled patients versus 19.0 ng/ml, interquartile range 11.0-42.0 in invasive-cooled patients, p = 0.99. Neurological and clinical outcome was similar in both groups. Target temperature of 33.0 °C was maintained more stable in the invasive group (33.0 versus 32.7 °C, p < 0.001). Bleeding complications were more frequent with invasive cooling (n = 17 [43.6 %] versus n = 7 [17.9 %]; p = 0.03).

CONCLUSION

Invasive cooling has advantages with respect to temperature management over surface cooling; however, did not result in different outcome as measured by NSE release in SCA survivors. Bleeding complications were more frequently encountered by invasive cooling.

Protective hypothermia: An old therapy with a new prospective

Therapeutic hypothermia (protective hypothermia) has been known to have beneficial effects since ancient times but interest was renewed after two land mark publication a decade ago. The survival as well as quality of life of post cardiac arrest patients depends on neurological outcome. Mild induced hypothermia is recommended for improving the neurological status of these patients. All acute care physician, nurses and emergency medical services personals should be aware of this approach. We report a case of post cardiac arrest that displayed improved neurological status with mild therapeutic hypothermia. Case: A young, female patient experienced perioperative cardiac arrest. Immediate resuscitation lead to return of spontaneous circulation in six minutes. Her post resuscitation Glasgow Coma score (GCS) was five. We induced therapeutic hypothermia—the patient required sedation and a chemical muscle relaxant. After 24 h we began slow rewarming. On day four, her GCS improved to 14, and she was extubated on day 6. She had mild cognitive disorder but was functionally independent. She was transferred to the ward on day 11 and subsequently discharged home. Conclusion: Mild induced therapeutic hypothermia improves neurological status of post cardiac arrest patients; however, it had adverse effect of increased risk for infection, arrhythmia and electrolyte disorders.

Femoro-iliacal artery versus pulmonary artery core temperature measurement during therapeutic hypothermia: an observational study

AIM OF THE STUDY

Therapeutic hypothermia after cardiac arrest improves neurologic outcome. The temperature measured in the pulmonary artery is considered to best reflect core temperature, yet is limited by invasiveness. Recently a femoro-arterial thermodilution catheter (PiCCO-Pulse Contour Cardiac Output) has been introduced in clinical practice as a safe and accurate haemodynamic monitoring system, which is also able to measure blood temperature. The aim of the study was to investigate, if the temperature measured with the PiCCO catheter reflects pulmonary artery temperature better than other sites during therapeutic hypothermia.

METHODS

In this observational study twenty patients after cardiac arrest and successful resuscitation were cooled with various cooling methods to 33 ± 1°C for 24h, followed by rewarming. Temperatures were recorded continuously in the pulmonary artery (Tpa), femoro-iliacal artery (Tpicco), ear canal (Tear), oesophagus (Toeso) and urinary bladder (Tbla). We assessed agreement of methods using the Bland Altman approach including bias and limits of agreement (LA).

RESULTS

All other sites differed significantly from Tpa with the bias varying from 0.4°C (Tbla) to -0.6°C (Tear). Standard deviations varied from 0.1°C (Tpicco, Toeso) to 0.5°C (Tear). For all sites bias was closer to zero with increasing average temperatures. Bias tended to be larger in the cooling phase compared to overall measurements.

CONCLUSIONS

Temperature measurement in the femoro-iliacal artery (Tpicco) reflects the gold standard of pulmonary artery temperature most accurately, especially during the cooling phase. Tpicco is easily accessible and might be used for monitoring core temperature without the need for additional temperature probes.

HIF-1-α and survivin involved in the anti-apoptotic effect of 2ME2 after global ischemia in rats

Survivin is an anti-apoptotic gene that decreases the apoptosis by depressing the expression of caspase-3. Hypoxia-inducible factor-1-alpha (HIF-1-alpha) is a transcription factor specifically activated by hypoxia. 2-methoxyestradiol (2ME2) is an estradiol derivative and a known HIF-1-alpha inhibitor. 2ME2 decreased apoptosis by inhibiting HIF-1-alpha. The aim of the present study was to investigate if survivin is involved in the anti-apoptotic effect of 2ME2. Male adult rats were used to make the global ischemia (GI) model. Ten minutes after GI, 2ME2 was injected intraperitoneally (16 mg/kg weight). Rats were killed at 6 hours, 12 hours, 24 hours, 48 hours, 96 hours, and 7 days. GI produced a marked increase in HIF-1-alpha expressions in the hippocampus at 6 hours and peaked at 48-96 hours. The expressions of survivin and caspase-3 were increased lightly in a similar time course. These molecular changes were accompanied by massive cell loss and apoptosis in the hippocampal regions. 2ME2 treatment reduced the expression of HIF-1-alpha, increased survivin expression, and decreased the expression of caspase-3. These results indicate that survivin and HIF-1-alpha were involved in the anti-apoptotic effect of 2ME2 treated following GI. 2ME2 may decrease the HIF-1-alpha expression, up-regulate the survivin expression, inhibit the expression of caspase-3, and finally reduce apoptosis after GI.

Neurologic and cardiac benefits of therapeutic hypothermia

Numerous studies have shown the favorable effects of lowering the core temperature of the body in various conditions such as acute myocardial infarction, acute cerebrovascular disease, acute lung injury, and acute spinal cord injury. Therapeutic hypothermia (TH) works at different molecular and cellular levels. TH improves oxygen supply to ischemic areas and increases blood flow by decreasing vasoconstriction, as well as oxygen consumption, glucose utilization, lactate concentration, intracranial pressure, heart rate, cardiac output, and plasma insulin levels. TH has been shown to improve neurologic outcome in acute cerebrovascular accidents. Furthermore, recent studies revealed that TH is a useful method of neuroprotection against ischemic neuronal injury after cardiac arrest. TH in out-of-hospital cardiac arrest is becoming a standard practice nationwide. Further studies need to be performed to develop a better understanding of the benefits and detrimental effects of TH, to identify the most efficacious TH strategy, and the candidates most likely to derive benefit from the procedure. Although many animal studies have demonstrated benefit, larger human clinical trials are recommended to investigate the beneficial effect of TH on reducing myocardial infarction size and coronary reperfusion injuries.

Is hypothermia after cardiac arrest effective in both shockable and nonshockable patients?: insights from a large registry

BACKGROUND

Although the level of evidence of improvement is significant in cardiac arrest patients resuscitated from a shockable rhythm (ventricular fibrillation or pulseless ventricular tachycardia [VF/Vt]), the use of therapeutic mild hypothermia (TMH) is more controversial in nonshockable patients (pulseless electric activity or asystole [PEA/asystole]). We therefore assessed the prognostic value of hypothermia for neurological outcome at hospital discharge according to first-recorded cardiac rhythm in a large cohort.

METHODS AND RESULTS

Between January 2000 and December 2009, data from 1145 consecutive out-of-hospital cardiac arrest patients in whom a successful resuscitation had been achieved were prospectively collected. The association of TMH with a good neurological outcome at hospital discharge (cerebral performance categories level 1 or 2) was quantified by logistic regression analysis. TMH was induced in 457/708 patients (65%) in VF/Vt and in 261/437 patients (60%) in PEA/asystole. Overall, 342/1145 patients (30%) reached a favorable outcome (cerebral performance categories level 1 or 2) at hospital discharge, respectively 274/708 (39%) in VF/Vt and 68/437 (16%) in PEA/asystole (P<0.001). After adjustment, in VF/Vt patients, TMH was associated with increased odds of good neurological outcome (adjusted odds ratio, 1.90; 95% confidence interval, 1.18 to 3.06) whereas in PEA/asystole patients, TMH was not significantly associated with good neurological outcome (adjusted odds ratio, 0.71; 95% confidence interval, 0.37 to 1.36).

CONCLUSIONS

In this large cohort of cardiac arrest patients, hypothermia was independently associated with an improved outcome at hospital discharge in patients presenting with VF/Vt. By contrast, TMH was not associated with good outcome in nonshockable patients. Further investigations are needed to clarify this lack of efficiency in PEA/asystole.

Mild Hypothermia as a Cardioprotective Approach for Acute Myocardial Infarction: Laboratory to Clinical Application

In many animal models, mild therapeutic hypothermia is a powerful intervention, reducing myocardial infarct size, reducing the no-reflow phenomenon, and improving healing after infarction. Cooling in these models has been produced by various means including whole-body hypothermia, synchronized hypothermic coronary venous retro-perfusion, heat exchangers, and regional hypothermia targeting the heart alone. However, in humans, the most widely used techniques are surface cooling and cooling by endovascular heat-exchange catheters. The reduction in temperature necessary to produce cardioprotection is mild (32-34°C), appears to have no detrimental effects on left ventricular function or regional myocardial blood flow, and may improve microvascular reflow to previously ischemic heart tissue. It has been shown in experimental and clinical studies that for therapeutic hypothermia to be effective it must be (1) initiated as early as possible after the onset of ischemia and (2) initiated before reperfusion. This may require initiation of hypothermia in the ambulance, well before mechanical reperfusion occurs. The mechanisms of protection produced by hypothermia have yet to be conclusively determined but may include a decrease in tissue metabolic rate, preservation of high energy phosphates, a reduction in tissue apoptosis or induction of heat shock proteins.

Hypothermic modulation of anoxic brain injury in adult survivors of cardiac arrest: a review of the literature and an algorithm for emergency physicians

Anoxic brain injury is a common outcome after cardiac arrest. Despite substantial research into the pathophysiology and management of this injury, a beneficial treatment modality has not been previously identified. Recent studies show that induced hypothermia reduces mortality and improves neurological outcomes in patients resuscitated from ventricular fibrillation. This article reviews the literature on induced hypothermia for anoxic brain injury and summarizes a treatment algorithm proposed by the Canadian Association of Emergency Physicians Critical Care Committee for hypothermia induction in cardiac arrest survivors.

Contemporary practices in postcardiac arrest syndrome: the role of mild therapeutic hypothermia

Out-of-hospital cardiac arrest remains a major cause of mortality and morbidity despite progress in resuscitative practices. The number of survivors with severe neurological impairment at hospital discharge is similarly dismal. Recently, much attention has been directed toward the use of mild therapeutic hypothermia in the care of comatose survivors with postcardiac arrest syndrome. Recent research suggests mild hypothermia lowers mortality and improves neurological outcome after successful treatment of cardiac arrest. The current 2005 updated guidelines of International Liaison Committee on Resuscitation and European Resuscitation Council recommend the utilization of mild induced hypothermia in postresuscitation treatment. Hypothermia induction in order to avoid the pathophysiological mechanisms of euthermia and hyperthermia and subsequent complications are briefly discussed. Cooling methods, potential side effects and questions regarding implementation of therapeutic hypothermia recommendations in every day clinical practice and future investigation are also addressed.

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.

Application of Induced Hypothermia for Neuroprotection after Cardiac Arrest: A Systematic Review

The dismal outcome after cardiac arrest calls for novel therapeutic approaches. Therapeutic hypothermia is a promising therapeutic modality. In this article we review the evidence for therapeutic hypothermia, for the best methods for cooling available and for the safety of therapeutic hypothermia.

Therapeutic hypothermia: past, present, and future

Cardiac arrest causes devastating neurologic morbidity and mortality. The preservation of the brain function is the final goal of resuscitation. Therapeutic hypothermia (TH) has been considered as an effective method for reducing ischemic injury of the brain. The therapeutic use of hypothermia has been utilized for millennia, and over the last 50 years has been routinely employed in the operating room. TH gained recognition in the past 6 years as a neuroprotective agent in victims of cardiac arrest after two large, randomized, prospective clinical trials demonstrated its benefits in the postresuscitation setting. Extensive research has been done at the cellular and molecular levels and in animal models. There are a number of proposed applications of TH, including traumatic brain injury, acute encephalitis, stroke, neonatal hypoxemia, and near-drowning, among others. Several devices are being designed with the purpose of decreasing temperature at a fast and steady rate, and trying to avoid potential complications. This article reviews the historical development of TH, and its current indications, methods of induction, and potential future.

Pathogenetic and prognostic significance of altered coagulation and fibrinolysis in acute lung injury/acute respiratory distress syndrome

OBJECTIVE

The coagulation and inflammatory cascades may be linked in the pathogenesis of acute lung injury and acute respiratory distress syndrome. However, direct evidence for the contribution of abnormalities in coagulation and fibrinolysis proteins to outcomes in patients with acute lung injury/acute respiratory distress syndrome is lacking.

DESIGN

Retrospective measurement of plasma levels of protein C and plasminogen activator inhibitor-1 in plasma samples that were collected prospectively as part of a large multicenter clinical trial. The primary outcome was hospital mortality. To evaluate the potential additive value of abnormalities of these biomarkers, the excess relative risk of death was calculated for each combination of quartiles of protein-C and plasminogen activator inhibitor-1 levels.

SETTING

Ten university medical centers.

PATIENTS

The study included 779 patients from a multicenter clinical trial of a protective ventilatory strategy in acute lung injury/acute respiratory distress syndrome and 99 patients with acute cardiogenic pulmonary edema, as well as ten normal controls.

MEASUREMENTS AND MAIN RESULTS

Compared with plasma from controls and patients with acute cardiogenic pulmonary edema, baseline protein-C levels were low and baseline plasminogen activator inhibitor-1 levels were elevated in acute lung injury/acute respiratory distress syndrome. By multivariate analysis, lower protein C and higher plasminogen activator inhibitor-1 were strong independent predictors of mortality, and ventilator-free and organ-failure-free days. Plasminogen activator inhibitor-1 and protein C had a synergistic interaction for the risk of death.

CONCLUSIONS

Early acute lung injury/acute respiratory distress syndrome is characterized by decreased plasma levels of protein C and increased plasma levels of plasminogen activator inhibitor-1 that are independent risk factors for mortality and adverse clinical outcomes. Measurement of plasminogen activator inhibitor-1 and protein-C levels may be useful to identify those at highest risk of adverse clinical outcomes for the development of new therapies.

Rapid implementation of therapeutic hypothermia in comatose out-of-hospital cardiac arrest survivors

BACKGROUND

The implementation of therapeutic hypothermia (TH) into daily clinical practice appears to be slow. We present our experiences with rapid implementation of a simple protocol for TH in comatose out-of-hospital cardiac arrest (OHCA) survivors.

METHODS

From June 2002, we started cooling pre-hospitally with sport ice packs in the groin and over the neck. In the intensive care unit (ICU), we used ice-water soaked towels over the torso. All patients were endotracheally intubated, on mechanical ventilation and sedated and paralysed. The target temperature was 33 +/- 1 degrees C to be maintained for 12-24 h. We used simple inclusion criteria: (i) no response to verbal command during the ambulance transport independent of initial rhythm and cause of CA; (ii) age 18-80 years; and (iii) absence of cardiogenic shock (SBP < 90 mmHg despite vasopressors). We compared the first 27 comatose survivors with a presumed cardiac origin of their OHCA with 34 historic controls treated just before implementation.

RESULTS

TH was initiated in all 27 eligible patients. The target temperature was reached in 24 patients (89% success rate). ICU- and hospital- length of stay did not differ significantly before and after implementation of TH. Hypokalemia (P= 0.001) and insulin resistance (P= 0.025) were more common and seizures (P= 0.01) less frequently reported with the use of TH. The implementation of TH was associated with a higher hospital survival rate (16/27; 59% vs. 11/34; 32%, respectively; P< or = 0.05). Our results indicate a population-based need of approximately seven cooling patients per 100,000 person-years served.

CONCLUSION

Our simple, external cooling protocol can be implemented overnight in any system already treating post-resuscitation patients. It was well accepted, feasible and safe, but not optimal in terms of cooling rate. Neither safety concerns nor costs should be a barrier for implementation of TH.

Outcome in neurocritical care: Advances in monitoring and treatment and effect of a specialized neurocritical care team

OBJECTIVE

To review current advances in the treatment of critically ill neurologic patients, including specialized care by neurointensivists.

DESIGN

Review article.

MAIN DISCUSSION AND CONCLUSIONS

Significant developments in the fields of neurology and neurosurgery have led to improved treatments for the critically ill neurologic patient. The major areas reviewed include neuromonitoring, disease-specific treatments, and specialized neurocritical care units and team. The current trend is for the application of the so-called multimodality neuromonitoring, which includes the use of several monitoring techniques, including intracranial pressure, brain electrophysiology, brain metabolism and oxygenation, and cerebral blood flow, among others. Many new therapies that have been introduced are discussed, including thrombolytic therapy for acute ischemic stroke, induced hypothermia for comatose survivors of cardiac arrest, and endovascular coiling for ruptured cerebral aneurysms. Lastly, the introduction of neurointensivists and neurocritical care units has been associated with reduced hospital mortality and resource utilization without changes in readmission rates or long-term mortality rates.

Therapeutic hypothermia

Therapeutic hypothermia has been used for millennia, but in recent years was not in much clinical use due to an apparent high risk of complications. More recently, the benefits of induced therapeutic hypothermia have been rediscovered, mainly with the improvement in neurological outcome in out-of-hospital cardiac arrest victims. In addition, therapeutic hypothermia has been suggested to improve outcome in other neurological conditions such as traumatic brain injury, neonatal asphyxia, cerebrovascular accidents and intracranial hypertension. This article reviews the history of the discovery of therapeutic hypothermia, as well as the current therapeutic applications and ways to deliver this treatment. Cooling techniques and recovery processes, as well as potential complications are also reviewed. Clinicians caring for a wide variety of critically ill patients should be familiar with the use of therapeutic hypothermia.

Under-humidification and over-humidification during moderate induced hypothermia with usual devices

OBJECTIVE

In mechanically ventilated patients with induced hypothermia, the efficacy of heat and moisture exchangers and heated humidifiers to adequately humidify the airway is poorly known. The aim of the study was to assess the efficacy of different humidification devices during moderate hypothermia.

DESIGN

Prospective, cross-over randomized study.

SETTINGS

Medical Intensive Care Unit in a University Hospital.

PATIENTS AND PARTICIPANTS

Nine adult patients hospitalized after cardiac arrest in whom moderate hypothermia was induced (33 degrees C for 24[Symbol: see text]h).

INTERVENTIONS

Patients were ventilated at admission (period designated "normothermia") with a heat and moisture exchanger, and were randomly ventilated during hypothermia with a heat and moisture exchanger, a heated humidifier, and an active heat and moisture exchanger.

MEASUREMENTS AND RESULTS

Core temperature, inspired and expired gas absolute and relative humidity were measured. Each system demonstrated limitations in its ability to humidify gases in the specific situation of hypothermia. Performances of heat and moisture exchangers were closely correlated to core temperature (r (2)[Symbol: see text]=[Symbol: see text]0.84). During hypothermia, heat and moisture exchangers led to major under-humidification, with absolute humidity below 25[Symbol: see text]mgH(2)O/l. The active heat and moisture exchanger slightly improved humidification. Heated humidifiers were mostly adequate but led to over-humidification in some patients, with inspiratory absolute humidity higher than maximal water content at 33 degrees C with a positive balance between inspiratory and expiratory water content.

CONCLUSIONS

These results suggest that in the case of moderate hypothermia, heat and moisture exchangers should be used cautiously and that heated humidifiers may lead to over-humidification with the currently recommended settings.

Recommended guidelines for reviewing, reporting, and conducting research on post-resuscitation care: The Utstein style

The aim of this report is to establish recommendations for reviewing, reporting, and conducting research during the post-resuscitation period in hospital. It defines data that are needed for research and more specialised registries and therefore supplements the recently updated Utstein template for resuscitation registries. The updated Utstein template and the out-of-hospital "Chain of Survival" describe factors of importance for successful resuscitation up until return of spontaneous circulation (ROSC). Several factors in the in-hospital phase after ROSC are also likely to affect the ultimate outcome of the patient. Large differences in survival to hospital discharge for patients admitted alive are reported between hospitals. Therapeutic hypothermia has been demonstrated to improve the outcome, and other factors such as blood glucose, haemodynamics, ventilatory support, etc., might also influence the result. No generally accepted, scientifically based protocol exists for the post-resuscitation period in hospital, other than general brain-oriented intensive care. There is little published information on this in-hospital phase. This statement is the result of a scientific consensus development process started as a symposium by a task force at the Utstein Abbey, Norway, in September 2003. Suggested data are defined as core and supplementary and include the following categories: pre-arrest co-morbidity and functional status, cause of death, patients' quality of life, in-hospital system factors, investigations and treatment, and physiological data at various time points during the first three days after admission. It is hoped that the publication of these recommendations will encourage research into the in-hospital post-resuscitation phase, which we propose should be included in the chain-of-survival as a fifth ring. Following these recommendations should enable better understanding of the impact of different in-hospital treatment strategies on outcome.

Mechanisms of hyperbaric oxygen and neuroprotection in stroke

Cerebral vascular diseases, such as neonatal encephalopathy and focal or global cerebral ischemia, all result in reduction of blood flow to the affected regions, and cause hypoxia-ischemia, disorder of energy metabolism, activation of pathogenic cascades, and eventual cell death. Due to a narrow therapeutic window for neuroprotection, few effective therapies are available, and prognosis for patients with these neurological injuries remains poor. Hyperbaric oxygen (HBO) has been used as a primary or adjunctive therapy over the last 50 years with controversial results, both in experimental and clinical studies. In addition, the mechanisms of HBO on neuroprotection remain elusive. Early applications of HBO within a therapeutic window of 3-6h or delayed but repeated administration of HBO can either salvage injured neuronal tissues or promote neurobehavioral functional recovery. This review explores the discrepancies between experimental and clinical observations of HBO, focusing on its therapeutic window in brain injuries, and discusses the potential mechanisms of HBO neuroprotection.

The Role of Thermoregulation in Cardiac Resuscitation

Regulating a patient's body temperature has long been within the scope of practice of the critical care nurse. Different measures and modalities have been used to achieve normothermia in the past. Recent research has demonstrated how crucial body temperature can be, not only because of its potential for neuroprotection but also because of its effects on all body systems. The general consensus of current literature is that maintaining mild hypothermia at 32 degrees to 34 degrees C (89.6 degrees-93.2 degrees F) for 12 to 24 hours after cardiac arrest may provide optimal neuroprotection with minimal complications for patients.

Multiple effects of hyperbaric oxygen on the expression of HIF-1 alpha and apoptotic genes in a global ischemia-hypotension rat model

Hypoxia-inducible factor-1alpha (HIF-1alpha) is a transcription factor specifically activated by hypoxia. Activation of proapoptotic caspase-9 and caspase-3 pathways, by binding with tumor suppressor p53, HIF-1alpha could lead to harmful actions such as apoptosis. We examined whether increasing oxygen levels by hyperbaric oxygen (HBO) offers neuroprotection, at least partially by suppression of HIF-1alpha and apoptotic genes. Male SD rats (n = 78) were randomly divided into 13 groups: 1 sham group, 6 groups of global ischemia-hypotension (GI), and 6 groups of HBO treatment after global ischemia-hypotension (GI + HBO). HBO (3 ATA for 2 h) was applied at 1 h after global ischemia-hypotension. Rats were sacrificed at 6, 12, 24, 48, and 96 h and 7 days. Global ischemia-hypotension (10 min ischemia, 30-35 mm Hg) produced a marked increase of HIF-1alpha expressions in the hippocampus and cortex at 6 h and peaked at 48-96 h. The expressions of p53, caspase-9, and caspase-3 were all increased in a similar time course. These molecular changes were accompanied by massive cell loss in the hippocampal regions and to a lesser degree in the cortex, with features of apoptosis. HBO treatment reduced expressions of HIF-1alpha, p53, caspase-9, and caspase-3 and decreased cell death. The protein levels of proapoptotic caspase-8 and antiapoptotic bcl-2 were increased after global ischemia-hypotension and HBO potentiated the expression of caspase-8 and decreased expression of bcl-2. These results indicate that HBO has multiple actions on apoptotic genes even though the overall effect of HBO was decreased HIF-1alpha expression and reduced apoptosis after global ischemia-hypotension.

Brain function after resuscitation from cardiac arrest

PURPOSE OF REVIEW

In industrial countries the incidence of cardiac arrest is still increasing. Almost 80% of cardiac arrest survivors remains in coma for varying lengths of time and full cerebral recovery is still a rare event. After successful cardiopulmonary resuscitation, cerebral recirculation disturbances and complex metabolic postreflow derangements lead to death of vulnerable neurons with further deterioration of cerebral outcome. This article discusses recent research efforts on the pathophysiology of brain injury caused by cardiac arrest and reviews the beneficial effect of therapeutic hypothermia on neurologic outcome along with the recent approach to prognosticate long-term outcome by electrophysiologic techniques and molecular markers of brain injury.

RECENT FINDINGS

Recent experimental studies have brought new insights to the pathophysiology of secondary postischemic anoxic encephalopathy demonstrating a time-dependent cerebral oxidative injury, increased neuronal expression, and activation of apoptosis-inducing death receptors and altered gene expression with long-term changes in the molecular phenotype of neurons. Recently, nuclear MR imaging and MR spectroscopic studies assessing cerebral circulatory recovery demonstrated the precise time course of cerebral reperfusion after cardiac arrest. Therapeutic hypothermia has been shown to improve brain function after resuscitation from cardiac arrest and has been introduced recently as beneficial therapy in ventricular fibrillation cardiac arrest.

SUMMARY

Electrophysiologic techniques and molecular markers of brain injury allow the accurate assessment and prognostication of long-term outcome in cardiac arrest survivors. In particular, somatosensory evoked potentials have been identified as the method with the highest prognostic reliability. A recent systematic review of 18 studies analyzed the predictive ability of somatosensory evoked potentials performed early after onset of coma and found that absence of cortical somatosensory evoked potentials identify patients not returning from anoxic coma with a specificity of 100%.

Clinical review: Devices and drugs for cardiopulmonary resuscitation -- opportunities and restraints

The science and technology of CPR is only just emerging from its infancy. However, substantial improvements are anticipated, including the ability of lay rescuers to identify cardiac arrest promptly, the availability of additional measurements, and expanded intelligence provided by expanded AEDs with which to more effectively prompt the rescuer through the resuscitation procedure. Most important in our view is the ability to maintain uninterrupted precordial compression. Better timing and better waveforms for defibrillation are emerging. The recognition of the importance of postresuscitation myocardial dysfunction and the selection of better vasopressor agents to minimize the adverse inotropic and chronotropic actions of adrenergic drugs are also likely to improve outcomes of CPR.