Nonselective β-blocking agent improves the outcome of cardiopulmonary resuscitation in a rat model

Beta-Adrenergic Blockade in Critical Illness

Catecholamine upregulation is a core pathophysiological feature in critical illness. Sustained catecholamine β-adrenergic induction produces adverse effects relevant to critical illness management. β-blockers (βB) have proposed roles in various critically ill disease states, including sepsis, trauma, burns, and cardiac arrest. Mounting evidence suggests βB improve hemodynamic and metabolic parameters culminating in decreased burn healing time, reduced mortality in traumatic brain injury, and improved neurologic outcomes following cardiac arrest. In sepsis, βB appear hemodynamically benign after acute resuscitation and may augment cardiac function. The emergence of ultra-rapid βB provides new territory for βB, and early data suggest significant improvements in mitigating atrial fibrillation in persistently tachycardic septic patients. This review summarizes the evidence regarding the pharmacotherapeutic role of βB on relevant pathophysiology and clinical outcomes in various types of critical illness.

Esmolol in the management of pre-hospital refractory ventricular fibrillation: A systematic review and meta-analysis

BACKGROUND

Esmolol has been proposed as a viable adjunctive therapy for pre-hospital refractory ventricular fibrillation/pulseless ventricular tachycardia (VF/pVT).

OBJECTIVES

We performed a systematic review and meta-analysis to assess the effectiveness of esmolol on pre-hospital refractory VF/pVT, compared with standard of care.

METHODS

MEDLINE, Embase, Scopus, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched for eligible studies. Two investigators independently extracted relevant data and assessed the methodological quality of each included study using the ROBINS-I tool. The quality of evidence for summary estimates was assessed according to GRADE guidelines. Pooled risk ratios (RRs) with 95% confidence intervals (CIs) for each outcome of interest were calculated.

RESULTS

The search yielded 3253 unique records, of which two studies were found to be in accordance with the research purpose, totaling 66 patients, of whom 33.3% (n = 22) received esmolol. Additional evidence was provided in the paper but was not relevant to the analysis and was therefore not included. Esmolol was likely associated with an increased rate of survival to discharge (RR 2.82, 95% CI 1.01-7.93, p = 0.05) (GRADE: Very low) and survival with favorable neurological outcome (RR 3.44, 95% CI 1.11-10.67, p = 0.03) (GRADE: Very low). Similar results were found for return of spontaneous circulation (ROSC) (RR 2.63, 95% CI 1.37-5.07, p = 0.004) (GRADE: Very low) and survival to intensive care unit (ICU)/hospital admission (RR 2.63, 95% CI 1.37-5.07, p = 0.004) (GRADE: Very low).

CONCLUSION

The effectiveness of esmolol for refractory VF/pVT remains unclear. Trial sequential analysis (TSA) indicates that the evidence is inconclusive and that further trials are required in order to reach a conclusion. Therefore, it is imperative to continue to accumulate evidence in order to obtain a higher level of scientific evidence.

Neuroendocrine Modulation of the Immune Response after Trauma and Sepsis: Does It Influence Outcome?

Although the treatment of multiple-injured patients has been improved during the last decades, sepsis and multiple organ failure (MOF) still remain the major cause of death. Following trauma, profound alterations of a large number of physiological systems can be observed that may potentially contribute to the development of sepsis and MOF. This includes alterations of the neuroendocrine and the immune system. A large number of studies focused on posttraumatic changes of the immune system, but the cause of posttraumatic immune disturbance remains to be established. However, an increasing number of data indicate that the bidirectional interaction between the neuroendocrine and the immune system may be an important mechanism involved in the development of sepsis and MOF. The aim of this article is to highlight the current knowledge of the neuroendocrine modulation of the immune system during trauma and sepsis.

Synergistic Effects of Moderate Therapeutic Hypothermia and Levosimendan on Cardiac Function and Survival After Asphyxia-Induced Cardiac Arrest in Rats

Background

This study investigated whether levosimendan, an inotropic calcium sensitizer, when combined with moderate therapeutic hypothermia, may exert synergistic benefits on post–cardiac arrest myocardial dysfunction and improve outcomes.

Methods and Results

After 9.5‐minute asphyxia‐induced cardiac arrest and resuscitation, 48 rats were randomized equally into 4 groups following return of spontaneous circulation (ROSC), including normothermia, hypothermia, normothermia–levosimendan, and hypothermia–levosimendan groups. For the normothermia group, the target temperature was 37°C while for the hypothermia group, the target temperature was 32°C, both of which were to be maintained for 4 hours after ROSC. Levosimendan was administered after ROSC with a loading dose of 10 μg/kg and then infused at 0.1 μg/kg per min for 4 hours. In the hypothermia–levosimendan group, left ventricular systolic function and cardiac output increased significantly, whereas the heart rate and systemic vascular resistance decreased significantly compared with the normothermia group. Also, the concentrations of interleukin 1β at 4 hours post‐ROSC and the production of NO between 1 hour and 4 hours post‐ROSC were reduced significantly in the hypothermia–levosimendan group compared with the normothermia group. The 72‐hour post‐ROSC survival and neurological recovery were also significantly better in the hypothermia–levosimendan group compared with the normothermia group (survival, 100% versus 50%, χ² test, P=0.006).

Conclusions

Compared with normothermia, only combined moderate therapeutic hypothermia and levosimendan treatment could consistently improve post–cardiac arrest myocardial dysfunction and decrease the release of pro‐inflammatory molecules, thereby improving survival and neurological outcomes. These findings suggest synergistic benefits between moderate therapeutic hypothermia and levosimendan.

β-Blockade use for Traumatic Injuries and Immunomodulation: A Review of Proposed Mechanisms and Clinical Evidence

Sympathetic nervous system activation and catecholamine release are important events following injury and infection. The nature and timing of different pathophysiologic insults have significant effects on adrenergic pathways, inflammatory mediators, and the host response. Beta adrenergic receptor blockers (β-blockers) are commonly used for treatment of cardiovascular disease, and recent data suggests that the metabolic and immunomodulatory effects of β-blockers can expand their use. β-blocker therapy can reduce sympathetic activation and hypermetabolism as well as modify glucose homeostasis and cytokine expression. It is the purpose of this review to examine either the biologic basis for proposed mechanisms or to describe current available clinical evidence for the use of β-blockers in traumatic brain injury, spinal cord injury, hemorrhagic shock, acute traumatic coagulopathy, erythropoietic dysfunction, metabolic dysfunction, pulmonary dysfunction, burns, immunomodulation, and sepsis.

Association of prior β-blocker use and the outcomes of patients with out-of-hospital cardiac arrest

β-Blocker therapy is one of the most commonly prescribed treatments for patients with cardiac conditions. In patients with out-of-hospital cardiac arrest (OHCA), however, recent data suggest that prior treatment with β-blockers could be harmful by lowering the incidence of a shockable presenting rhythm. The main objective of our study was to determine the association between prior β-blocker use and mortality in OHCA patients.

METHODS

An observational study was conducted using the Toronto Rescu Epistry database that captured consecutive OHCA patients from 2005 to 2010. Patients older than 65 years with nontraumatic cardiac arrest and attempted resuscitation were included. Patients prescribed β-blockers within 90 days of the arrest were compared with those without such therapy. The primary outcome was all-cause mortality at 30 days. Potential confounders were accounted for by inverse probability of treatment weighting using the propensity score.

RESULTS

The median age of 8,266 OHCA patients was 79 years, 41% were women, and 2,911 (35.2%) were prescribed a β-blocker prior to cardiac arrest. Patients prescribed β-blockers were more likely to have existing cardiac risk factors and cardiovascular conditions. In the propensity-weighted cohort, there were no differences in the presenting rhythm, with 18.4% of patients in the β-blocker group having a shockable rhythm vs 17.5% in the no β-blocker group (standardized difference .023). In addition, 30-day mortality was not significantly different between patients prescribed β-blockers and no β-blockers (95.6% vs 95.1%, P = .36).

CONCLUSION

β-Blocker use was not associated with lower rates of shockable rhythms or mortality among older patients with OHCA.

The effects of α- and β-adrenergic blocking agents on postresuscitation myocardial dysfunction and myocardial tissue injury in a rat model of cardiac arrest

We investigated the relationship between the severity of postresuscitation (PR) myocardial tissue injury and myocardial dysfunction after the administration of epinephrine as well as the protective effects of α- and β-adrenergic blocking agents. Forty male Sprague-Dawley rats were randomized into 6 groups: (1) placebo; (2) epinephrine; (3) epinephrine pretreated with α1-blocker (prazosin); (4) epinephrine pretreated with α2-blocker (yohimbine); (5) epinephrine pretreated with β-blocker (propranolol); and (6) epinephrine pretreated with β- plus α1-blocker (propranolol and prazosin). Cardiopulmonary resuscitation was initiated after 8 minutes of untreated ventricular fibrillation and continued for an additional 8 minutes. The myocardial function and the serum concentrations of troponin I (Tn I) and N-terminal probrain natriuretic peptide (NT-proBNP) were measured at baseline and after resuscitation. After resuscitation, both Tn I and NT-proBNP were significantly increased in all groups, especially in the epinephrine and epinephrine pretreated with α2-blocker groups. Significantly better PR myocardial function and neurologic deficit score were observed in epinephrine pretreated with the α1- or β-blocker with decreased releases of Tn I and NT-proBNP. However, the most significant improvements were observed in the animals pretreated with β- plus α1-blocker. The present study demonstrated that myocardial stunning may not be the only mechanism of PR myocardial dysfunction. Administration of epinephrine increased the severity of PR myocardial tissue injury and dysfunction. The β- and β- plus α1-blocker pretreatment significantly reduced the severity of PR myocardial tissue injury and myocardial dysfunction with better neurologic function and prolonged duration of survival.

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

A rat model of electrically-induced ventricular fibrillation followed by cardiac resuscitation using a closed chest technique that incorporates the basic components of cardiopulmonary resuscitation in humans is herein described. The model was developed in 1988 and has been used in approximately 70 peer-reviewed publications examining a myriad of resuscitation aspects including its physiology and pathophysiology, determinants of resuscitability, pharmacologic interventions, and even the effects of cell therapies. The model featured in this presentation includes: (1) vascular catheterization to measure aortic and right atrial pressures, to measure cardiac output by thermodilution, and to electrically induce ventricular fibrillation; and (2) tracheal intubation for positive pressure ventilation with oxygen enriched gas and assessment of the end-tidal CO2. A typical sequence of intervention entails: (1) electrical induction of ventricular fibrillation, (2) chest compression using a mechanical piston device concomitantly with positive pressure ventilation delivering oxygen-enriched gas, (3) electrical shocks to terminate ventricular fibrillation and reestablish cardiac activity, (4) assessment of post-resuscitation hemodynamic and metabolic function, and (5) assessment of survival and recovery of organ function. A robust inventory of measurements is available that includes - but is not limited to - hemodynamic, metabolic, and tissue measurements. The model has been highly effective in developing new resuscitation concepts and examining novel therapeutic interventions before their testing in larger and translationally more relevant animal models of cardiac arrest and resuscitation.

β-Receptor blocker influences return of spontaneous circulation and chemical examination in rats during cardiopulmonary resuscitation

OBJECTIVE

We investigated the influence of β-receptor blocker metoprolol on return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR) in rats with induced myocardial infarction (MI).

METHODS

Male Sprague-Dawley rats were randomly divided into three groups: the sham-operated group, the MI group without metoprolol, which was fed the vehicle, and the MI+metoprolol group receiving intragastric metoprolol. Each group was further divided randomly into three subgroups, depending on the dosage of epinephrine administered during subsequent CPR applied after the induction of asphyxial cardiac arrest.

RESULTS

The ROSC rate was significantly decreased in the low dose subgroup of MI group, unchanged in the medium dose subgroup of MI group, and significantly decreased in the high dose subgroup of MI group, compared with the same dose subgroup of sham-operated group. MI+metoprolol group had a lower ROSC rate than MI group in the medium dose subgroup, and a higher ROSC rate than MI group in the high dose subgroup. There was no difference in blood K(+) values of successful rats between MI group and MI+metoprolol group. The rats with successful CPR had lower blood K(+) values than rats with unsuccessful CPR in each of the three treatment groups.

CONCLUSIONS

Metoprolol administered to MI rats over a long period significantly improved ROSC rates under an appropriate dose of epinephrine during CPR. An increasing high blood K(+) value would attenuate the rate of a successful CPR.

Cytidine diphosphate choline improves the outcome of cardiac arrest vs epinephrine in rat model

OBJECTIVES

Cytidine diphosphate choline (CDP-choline) is a cholinergic agent that can both stimulate the cholinergic pathway and increase blood pressure. We aimed to investigate the effects of CDP-choline on the outcome of cardiac arrest in comparison with epinephrine.

METHODS

This was a randomized prospective animal study. Cardiac arrest was induced by asphyxia in 45 rats. After 7 minutes of asphyxia, resuscitation was attempted. The rats were allocated to different groups treated with 2 mL/kg saline, 100 μg/kg epinephrine, or 250 mg/kg CDP-choline. The hemodynamic parameters were monitored for 2 hours after resuscitation, and cardiac function was evaluated by echocardiography 2 hours after resuscitation. The hearts were harvested at the end of monitoring for histologic evaluation.

RESULTS

Epinephrine and CDP-choline improved the rate of return of spontaneous circulation and blood pressure during cardiopulmonary resuscitation; however, postresuscitation cardiac function in the CDP-choline and placebo groups was better than in the epinephrine group. Compared with the epinephrine group, less myocardial and mitochondrial injury was observed by electron microscopy in the CDP-choline and placebo groups; the level of superoxide dismutase and malondialdehyde indicated less peroxidative injury in the CDP-choline and placebo groups. Cytidine diphosphate choline and placebo also preserved connexin 43 when compared with epinephrine.

CONCLUSION

When administered during resuscitation, CDP-choline increased the rate of return of spontaneous circulation similarly to epinephrine. In addition, it did not increase the severity of myocardial injury and postresuscitation myocardial dysfunction, whereas epinephrine appeared to be harmful.

Anesthetic management of a patient with deteriorated cardiac function following cardiopulmonary resuscitation

A 73-year-old woman suffering from an abdominal aortic aneurysm (AAA), unstable angina, and low cardiac function (32% of ejection fraction) was scheduled for abdominal aortic replacement and coronary artery bypass grafting. However, before the scheduled operation the patient fell into cardiopulmonary arrest with ventricular fibrillation due to rupture of the AAA. Immediate cardiopulmonary resuscitation (CPR) using epinephrine and electrical defibrillation restored the spontaneous circulation. Following CPR, a continuous high-dose dopamine infusion (15 µg/kg/min) was initiated and emergent abdominal aortic replacement was performed. On arrival at the operating room, the patient showed serious hypotension, atrial fibrillation with multifocal ventricular premature contractions, and metabolic acidosis. Transesophageal echocardiography (TEE) suggested that the circulatory collapse might have resulted from diastolic dysfunction and deteriorated compliance of the left ventricular (LV) wall, possibly due to myocardial stunning induced by myocardial ischemia, and tachycardia induced by hypovolemia, both of which are influenced by high doses of catecholamine. We accordingly transfused adequate amounts of blood products and gradually decreased the infusion rate of dopamine to 4 µg/kg/min, while carefully monitoring blood pressure, central venous pressure, and TEE. By the end of surgery hemodynamic parameters had recovered to near normal levels. In post-resuscitated and hypovolemic patients, caution should be taken when administering high levels of exogenous catecholamines, which can induce myocardial stunning and circulatory collapse.

Epinephrine in resuscitation: curse or cure?

The use of epinephrine during cardiac arrest has been advocated for decades and forms an integral part of the published guidelines. Its efficacy is supported by animal data, but human trial evidence is lacking. This is partly attributable to disparities in trial methodology. Epinephrine’s pharmacologic and physiologic effects include an increase in coronary perfusion pressure that is key to successful resuscitation. One possible explanation for the lack of epinephrine’s demonstrated efficacy in human trials of out-of-hospital cardiac arrest is the delay in its administration. A potential solution may be intraosseus epinephrine, which can be administered quicker. More importantly, it is the quality of the basic life support, early and uninterrupted chest compressions, early defibrillation and postresuscitation care that will provide the best chance of neurologically intact survival.

Cardioprotective effects of erythropoietin on postresuscitation myocardial dysfunction in appropriate therapeutic windows

OBJECTIVE

Erythropoietin has been noted for its cardioprotective effects. The objective of the study is to investigate its effects on postresuscitation myocardial dysfunction and therapeutic windows.

DESIGN

Randomized animal study.

SETTING

Animal research laboratory.

SUBJECTS

Adult male adult Wistar rats.

INTERVENTIONS

Cardiopulmonary resuscitation was started after 6.5 or 9.5 mins of asphyxia-induced cardiac arrest. The resuscitated animals received either erythropoietin (1000, 3000, or 5000 U/kg) or placebo intravenously 3 mins after return of spontaneous circulation.

MEASUREMENTS AND MAIN RESULTS

Erythropoietin treatment improved the 3-day survival and left ventricular dP/dt40 and peak negative dP/dt after 6.5 mins asphyxia-induced cardiac arrest. The cardioprotective effects of erythropoietin decreased after 9.5 mins asphyxia-induced cardiac arrest with worse postresuscitation left ventricular dP/dt40 and peak negative dP/dt (p < .01 for both). The erythropoietin showed a dose-dependent response for its cardioprotective effects. The 3-day survival rates were higher in the group treated with erythropoietin 5000 U/kg than with 3000 and 1000 U/kg groups (p = .045 and .003, respectively). Postresuscitation left ventricular dP/dt40 and peak negative dP/dt were more preserved in the group treated with erythropoietin 5000 U/kg than the groups with lower doses (p < .05 for both).

CONCLUSIONS

Erythropoietin has the potential to improve postresuscitation myocardial dysfunction and short-term survival in appropriate therapeutic windows.

The potential beneficial effects of beta adrenergic blockade in the treatment of ventricular fibrillation

Cardiac arrest remains a major medical emergency in Western societies, with ventricular fibrillation being the initial rhythm in a significant proportion of cases. Adrenaline is generally accepted to improve the resuscitation outcome, since it improves coronary and cerebral blood flow during cardiopulmonary resuscitation, but several detrimental effects have been associated with its use, most of which are thought to be mediated by its beta adrenergic properties. Several animal studies suggest that beta adrenergic blockade during resuscitation, is associated with increased rates of resuscitation and improved post-resuscitation myocardial function. This article reviews the presence and function of beta-adrenoceptor subtypes in the intact and diseased human myocardium, as well as the differences observed in beta(1)- and beta(2) adrenoceptor subtypes in different species.

The use of mice and rats as animal models for cardiopulmonary resuscitation research

Cardiopulmonary resuscitation (CPR) after the induction of cardiac arrest (CA) has been studied in mice and rats. The anatomical and physiological parameters of the cardiopulmonary system of these two species have been defined during experimental studies and are comparable with those of humans. Moreover, these animal models are more ethical to establish and are easier to manipulate, when compared with larger experimental animals. Accordingly, the effects of successful CPR on the function of vital organs, such as the brain, have been investigated because damage to these vital organs is of concern in CA survivors. Furthermore, the efficacy of several drugs, such as adrenaline (epinephrine), vasopressin and nitroglycerin, has been evaluated for use in CA in these small animal models. The purpose of these studies is not only to increase the rate of survival of CA victims, but also to improve their quality of life by reducing damage to their vital organs after CA and during CPR.

Could Beta blockade improve outcome after injury by modulating inflammatory profiles?

BACKGROUND

Cardioprotection with beta-receptor antagonists improves outcome in high risk patients undergoing elective surgery. Recent trials have demonstrated an association between beta blocker (BB) use and improved outcomes after injury. The mechanisms through which BB result in improved outcomes remain poorly elucidated. In vitro evidence supports that BB modulates the postinjury inflammatory response. The purpose of this study was to examine the effects of BB on inflammatory profiles in injured patients at increased risk for heart disease.

METHODS

A pseudo-randomized, controlled trial of injured patients over 55 admitted to the intensive care unit was conducted. Patients were randomized to receive continuous BB or standard of care. Patients with a reported history of prehospital BB use were enrolled into an observational arm of the trial, continued on BB, and analyzed with the continuous BB group. Plasma interleukin (IL)-6 and IL-1beta levels were measured by enzyme-linked immunosorbent assay at baseline and day 1, 2, and 4 after BB initiation. Cytokine data were log transformed for normality assumptions. Repeated measures analysis of variance was used to test for within-group differences in cytokine levels over time.

RESULTS

Forty-two patients were enrolled. Seventeen patients were randomized to the control group and 25 patients received continuous BB (10 randomized/15 observational). There was no difference in gender, age, prior history of heart disease, or admission heart rate, systolic blood pressure or initial base deficit between groups. Baseline levels of IL-6 and IL-1beta did not differ between groups. Levels of IL-6, but not IL-1beta, decreased over time in patients receiving BB (p = 0.04), whereas levels in controls remained unchanged (p = 0.27). There were no BB related complications.

CONCLUSIONS

Use of BB decreases serum IL-6 levels over time in injured patients at risk for heart disease. This may contribute to improved outcomes noted in trauma patients receiving BB. Additionally, BB use in this population of patients is safe after endpoints of resuscitation have been met.

β-Blockers for the treatment of cardiac arrest from ventricular fibrillation?

More than 160,000 people suffer sudden cardiac death each year in the US. It is estimated that ventricular fibrillation (VF) is the initial rhythm in approximately 30% of these cases. Ventricular fibrillation that does not respond to the first few defibrillation attempts is associated with mortality rates of up to 97%. Currently, no pharmacological intervention has been shown to increase long-term survival in patients with shock-refractory VF. The purpose of this review article is to evaluate whether beta-blocker administration during the resuscitation of cardiac arrest from VF or pulseless ventricular tachycardia (VT) improves outcome. We searched the MEDLINE and EMBASE databases for human clinical trials, animal experimental trials, review articles, case reports and abstracts published between 1966 and September 2006. No human prospective randomized controlled trial has studied the effects of beta-blocker administration during VF directly. Prospective trials of anti-arrhythmics with beta-blocking properties have been published, as well as several case reports/case series and experimental animal studies. The evidence thus far suggests that beta-blockade during resuscitation from VF may be associated with increasing rates of resuscitation, greater post-resuscitation survival, and improved post-resuscitation myocardial function. These positive effects on outcome may be mediated by a decrease in the oxygen requirements of the fibrillating heart, thus improving the overall balance between myocardial oxygen supply and demand during resuscitation. While no significant detrimental effects directly related to low dose beta-blockade during VF have been reported in the studies reviewed, concerns relating to possible loss of myocardial contractility and hypotension remain. To this day, high quality human trials are lacking. Preliminary human studies are needed to assess the effects of beta-blockers in the treatment of cardiac arrest from ventricular fibrillation or pulseless VT further.

Beta-blocker use and the changing epidemiology of out-of-hospital cardiac arrest rhythms

BACKGROUND

The incidence of ventricular fibrillation (VF) as the presenting rhythm in out-of-hospital cardiac arrest (OHCA) is declining, whereas pulseless electrical activity (PEA) is increasing. This changing epidemiology has occurred concomitant with an increase in beta-blocker use.

AIMS

The aim of this study was to measure the association of beta-blocker use among prehospital cardiac arrest patients with PEA versus VF as presenting rhythm.

MATERIALS AND METHODS

In this retrospective cohort study, records of all OHCA patients presenting to a single municipal hospital between 1 January 2001 and 31 December 2006 were reviewed. Age, sex, race, first documented rhythm, estimated down time, presence of bystander CPR, return of spontaneous circulation, beta-blocker use, and comorbid illnesses were noted. A Mantel-Haenzel chi-square was computed to describe the association between beta-blocker use and PEA, compared to beta-blocker use and VF. A sensitivity analysis was also performed to account for missing data, misclassification of beta-blocker use, misclassification of initial rhythm, confounding by unknown factors, and random error.

RESULTS

After exclusion of patients with asystole and patients in whom beta-blocker use was unclear/unknown, a cohort of 179 arrests was evaluated. The odds ratio for beta-blocker use among PEA versus VF patients was 3.7 (95% CI 1.9-7.2), and probabilistic adjustment for exposure and outcome misclassification, confounding, and random error increased the odds ratio to 5.0 (95% CI 1.1-31.0).

CONCLUSIONS

There appears to be an association between beta-blockers and the changing epidemiology of arrest rhythms, which may account for the increasing incidence of PEA and concomitant decrease in VF.

Erythropoietin improves the postresuscitation myocardial dysfunction and survival in the asphyxia-induced cardiac arrest model

To investigate the effect of erythropoietin for the management of postresuscitation myocardial dysfunction following asphyxia-induced cardiac arrest. Male adult Wistar rats were used for the prospective controlled animal study. Asphyxia-induced cardiac arrest was performed by turning-off the ventilator and clamping the endotracheal tube. Cardiopulmonary resuscitation with an intravenous injection of 0.01 mg/kg epinephrine and mechanical ventilation were started after 6.5 minutes of asphyxia. The resuscitated animals received either erythropoietin (5000 U/kg) or equivalent volume of 0.9% saline as placebo intravenously 3 minutes after return of spontaneous circulation. The erythropoietin treatment produced better left ventricular dP/dt40 and -dP/dt in the invasive hemodynamic measurements, and left ventricular fraction shortening by echocardiography. Administration of erythropoietin also improved three days survival among those successfully resuscitated. The molecular effects of erythropoietin were shown by activation of its down streaming Akt and ERK 42/44 signaling pathways. EPO has the potential to improve postresuscitation myocardial dysfunction and short term survival in rats after asphyxia-induced cardiac arrest.

Sustained abdominal compression during CPR raises coronary perfusion pressures as much as vasopressor drugs

OBJECTIVES

This study investigated sustained abdominal compression as a means to improve coronary perfusion pressure (CPP) during cardiopulmonary resuscitation (CPR) and compared the resulting CPP augmentation with that achieved using vasopressor drugs.

METHOD

During electrically induced ventricular fibrillation in anesthetized, 30kg juvenile pigs, Thumper CPR was supplemented at intervals either by constant abdominal compression at 100-500mmHg using an inflated contoured cuff or by the administration of vasopressor drugs (epinephrine, vasopressin, or glibenclamide). CPP before and after cuff inflation or drug administration was the end point.

RESULTS

Sustained abdominal compression at >200mmHg increases CPP during VF and otherwise standard CPR by 8-18mmHg. The effect persists over practical ranges of chest compression force and duty cycle and is similar to that achieved with vasopressor drugs. Constant abdominal compression also augments CPP after prior administration of epinephrine or vasopressin.

CONCLUSIONS

During CPR noninvasive abdominal compression with the inflatable contoured cuff rapidly elevates the CPP, sustains the elevated CPP as long as the device is inflated, and is immediately and controllably reversible upon device deflation. Physical control of peripheral vascular resistance during CPR by abdominal compression has some advantages over pharmacological manipulation and deserves serious reconsideration, now that the limitations of pressor drugs during CPR have become better understood, including post-resuscitation myocardial depression and the need for intravenous access.

[Utility of vasopressin in cardiopulmonary resuscitation]

Many vasopressants have been studied in cardiopulmonary resuscitation (CPR) to increase cerebral and coronary perfusion. Although there is a debate on the utility of epinephrine, this is the one that has been used historically, above all after verifying that other agents such as norepinephrine, metoxamine or phenylephrine, have not been shown to be more effective. Currently, due to the good experimental results, the use of vasopressin (ADH) in CPR is being evaluated. However there is little (only three studies) and debated evidence based on randomized clinical trials (norepinephrine or ADH) in humans. Once these are reviewed, it can be concluded: The results of the three randomized studies in humans obtain different results regarding the utility of ADH in cardiorespiratory arrest (CRA) secondary to ventricular fibrillation, electro-mechanical dissociation or asystole. More prospective studies are needed to know the role of ADH in prolonged CRA and in asystole, that may be the subgroups that can benefit the most from this drug. The neurological repercussion of a drug in the context of CRA should be evaluated before its inclusion in the CPR guides.

Levosimendan improves postresuscitation myocardial dysfunction after β-adrenergic blockade

In earlier studies, we found that a nonselective beta-adrenergic blocking agent, propranolol, facilitated cardiac resuscitation, reduced postresuscitation myocardial ectopy, and improved postresuscitation survival. However, the potential adverse effects and specifically the negative inotropic actions of propranolol prompted our further investigation of the potential value of a non-beta-adrenergic inotropic drug, levosimendan, in conjunction with propranolol, for minimizing postresuscitation myocardial dysfunction after successful resuscitation from cardiac arrest. Ventricular fibrillation was induced and untreated for 7 minutes in 15 domestic pigs, which were divided into propranolol, propranolol plus levosimendan, and control groups. Propranolol was administered as a bolus dose of 0.1 mg/kg during cardiac arrest. Electrical defibrillation was attempted after 12 minutes of cardiac arrest including 5 minutes of precordial compression. Levosimendan was administered at 10 minutes after successful resuscitation in a dose of 20 microg/kg and followed by infusion of 0.4 microg/kg/min over the ensuing 220 minutes. Propranolol reduced energies or numbers of defibrillatory shocks and postresuscitation myocardial ectopy, and it improved postresuscitation myocardial dysfunction. When levosimendan was added, postresuscitation myocardial contractile function was improved even more.

Resuscitation and Emergency Management for Neonatal Foals

Early intervention can dramatically alter outcome in foals. Cardio-pulmonary cerebral resuscitation can be successful and clinically worthwhile when applied to foals that arrest as part of the birthing process. Readily available equipment and an ordered plan starting with addressing the respiratory system (airway and breathing) followed by the circulatory system (circulation and drugs) are the keys to success. Hypoglycemia is common in foals that are not nursing and in septic foals. Support of serum glucose can be an important emergency treatment. Respiratory support with oxygen therapy should be considered in all foals following resuscitation and dystocia. Other foals that are likely to benefit from oxygen are those that are dyspneic, cyanotic, meconium-stained after birth,or recumbent. Emergency therapies, applied correctly, are expected to result in decreased mortality and morbidity.