Endothelin-1 vasoconstriction during swine cardiopulmonary resuscitation improves coronary perfusion pressures but worsens postresuscitation outcome

How Epinephrine Administration Interval Impacts the Outcomes of Resuscitation during Adult Cardiac Arrest: A Systematic Review and Meta-Analysis

Current guidelines for treating cardiac arrest recommend administering 1 mg of epinephrine every 3−5 min. However, this interval is based solely on expert opinion. We aimed to investigate the impact of the epinephrine administration interval (EAI) on resuscitation outcomes in adults with cardiac arrest. We systematically reviewed the PubMed, EMBASE, and Scopus databases. We included studies comparing different EAIs in adult cardiac arrest patients with reported neurological outcomes. Pooled estimates were calculated using the IVhet meta-analysis, and the heterogeneities were assessed using Q and I2 statistics. We evaluated the study risk of bias and overall quality using validated bias assessment tools. Three studies were included. All were classified as “good quality” studies. Only two reported the primary outcome. Compared with a recommended EAI of 3−5 min, a favorable neurological outcome was not significantly different in patients with the other frequencies: for <3 min, odds ratio (OR) 1.93 (95% CI: 0.82−4.54); for >5 min, OR 1.01 (95% CI: 0.55−1.87). For survival to hospital discharge, administering epinephrine for less than 3 min was not associated with a good outcome (OR 1.66, 95% CI: 0.89−3.10). Moreover, EAI of >5 min did not pose a benefit (OR 0.87, 95% CI: 0.68−1.11). Our review showed that EAI during CPR was not associated with better hospital outcomes. Further clinical trials are necessary to determine the optimal dosing interval for epinephrine in adults with cardiac arrest.

Treatment Outcomes of Epinephrine for Traumatic Out-of-hospital Cardiac Arrest: A Systematic Review and Meta-analysis

INTRODUCTION

Despite the standard guidelines stating that giving epinephrine for patients with cardiac arrest is recommended, the clinical benefits of epinephrine for patients with traumatic out-of-hospital cardiac arrest (OHCA) are still limited. This study aims to evaluate the benefits of epinephrine administration in traumatic OHCA patients.

METHODS

We searched four electronic databases up to June 30, 2020, without any language restriction in research sources. Studies comparing epinephrine administration for traumatic OHCA patients were included. Two independent authors performed the selection of relevant studies, data extraction, and assessment of the risk of bias. The primary outcome was inhospital survival rate. Secondary outcomes included prehospital return of spontaneous circulation (ROSC), short-term survival, and favorable neurological outcome. We calculated the odds ratios (ORs) of those outcomes using the Mantel-Haenszel model and assessed the heterogeneity using the I² statistic.

RESULTS

Four studies were included. The risk of bias of the included studies was low, except for one study in which the risk of bias was fair. All included studies reported the inhospital survival rate. Epinephrine administration during traumatic OHCA might not demonstrate a benefit for inhospital survival (OR: 0.61, 95% confidence interval [CI]: 0.11-3.37). Epinephrine showed no significant improvement in prehospital ROSC (OR: 4.67, 95% CI: 0.66-32.81). In addition, epinephrine might not increase the chance of short-term survival (OR: 1.41, 95% CI: 0.53-3.79).

CONCLUSION

The use of epinephrine for traumatic OHCA may not improve either inhospital survival or prehospital ROSC and short-term survival. Epinephrine administration as indicated in standard advanced life support algorithms might not be routinely used in traumatic OHCA.

Comparing Drugs for Out-of-hospital, Shock-refractory Cardiac Arrest: Systematic Review and Network Meta-analysis of Randomized Controlled Trials

INTRODUCTION

The benefit of medications used in out-of-hospital, shock-refractory cardiac arrest remains controversial. This study aims to compare the treatment outcomes of medications for out-of-hospital, shock-refractory ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT).

METHODS

The inclusion criteria were randomized controlled trials of participants older than eight years old who had atraumatic, out-of-hospital, shock-refractory VF/pVT in which at least one studied group received a medication. We conducted a database search on October 28, 2019, that included PubMed, Scopus, Web of Science, CINAHL Complete, and Cochrane CENTRAL. Citations of relevant meta-analyses were also searched. We performed frequentist network meta-analysis (NMA) to combine the comparisons. The outcomes were analyzed by using odds ratios (OR) and compared to placebo. The primary outcome was survival to hospital discharge. The secondary outcomes included the return of spontaneous circulation (ROSC), survival to hospital admission, and the neurological outcome at discharge. We ranked all outcomes using surface under the cumulative ranking score.

RESULTS

We included 18 studies with 6,582 participants. The NMA of 20 comparisons included 12 medications and placebo. Only norepinephrine showed a significant increase of ROSC (OR = 8.91, 95% confidence interval [CI], 1.88-42.29). Amiodarone significantly improved survival to hospital admission (OR = 1.53, 95% CI, 1.01-2.32). The ROSC and survival-to-hospital admission data were significantly heterogeneous with the I2 of 55.1% and 59.1%, respectively. This NMA satisfied the assumption of transitivity.

CONCLUSION

No medication was associated with improved survival to hospital discharge from out-of-hospital, shock-refractory cardiac arrest. For the secondary outcomes, norepinephrine was associated with improved ROSC and amiodarone was associated with an increased likelihood of survival to hospital admission in the NMA.

Clinical outcomes and safety of passive leg raising in out-of-hospital cardiac arrest: a randomized controlled trial

BACKGROUND

There are data suggesting that passive leg raising (PLR) improves hemodynamics during cardiopulmonary resuscitation (CPR). This trial aimed to determine the effectiveness and safety of PLR during CPR in out-of-hospital cardiac arrest (OHCA).

METHODS

We conducted a randomized controlled trial with blinded assessment of the outcomes that assigned adults OHCA to be treated with PLR or in the flat position. The trial was conducted in the Camp de Tarragona region. The main end point was survival to hospital discharge with good neurological outcome defined as cerebral performance category (CPC 1-2). To study possible adverse effects, we assessed the presence of pulmonary complications on the first chest X-rays, brain edema on the computerized tomography (CT) in survivors and brain and lungs weights from autopsies in non-survivors.

RESULTS

In total, 588 randomized cases were included, 301 were treated with PLR and 287 were controls. Overall, 67.8% were men and the median age was 72 (IQR 60-82) years. At hospital discharge, 3.3% in the PLR group and 3.5% in the control group were alive with CPC 1-2 (OR 0.9; 95% CI 0.4-2.3, p = 0.91). No significant differences in survival at hospital admission were found in all patients (OR 1.0; 95% CI 0.7-1.6, p = 0.95) and among patients with an initial shockable rhythm (OR 1.7; 95% CI 0.8-3.4, p = 0.15). There were no differences in pulmonary complication rates in chest X-rays [7 (25.9%) vs 5 (17.9%), p = 0.47] and brain edema on CT [5 (29.4%) vs 10 (32.6%), p = 0.84]. There were no differences in lung weight [1223 mg (IQR 909-1500) vs 1239 mg (IQR 900-1507), p = 0.82] or brain weight [1352 mg (IQR 1227-1457) vs 1380 mg (IQR 1255-1470), p = 0.43] among the 106 autopsies performed.

CONCLUSION

In this trial, PLR during CPR did not improve survival to hospital discharge with CPC 1-2. No evidence of adverse effects has been found. Clinical trial registration ClinicalTrials.gov: NCT01952197, registration date: September 27, 2013, https://clinicaltrials.gov/ct2/show/NCT01952197 .

Comparing anesthesia with isoflurane and fentanyl/fluanisone/midazolam in a rat model of cardiac arrest

Only one in ten patients survives cardiac arrest (CA), underscoring the need to improve CA management. Isoflurane has shown cardio- and neuroprotective effects in animal models of ischemia-reperfusion injury. Therefore, the beneficial effect of isoflurane should be tested in an experimental CA model. We hypothesize that isoflurane anesthesia improves short-term outcome following resuscitation from CA compared with a subcutaneous fentanyl/fluanisone/midazolam anesthesia. Male Sprague-Dawley rats were randomized to anesthesia with isoflurane ( n = 11) or fentanyl/fluanisone/midazolam ( n = 11). After 10 min of asphyxial CA, animals were resuscitated by mechanical chest compressions, ventilations, and epinephrine and observed for 30 min. Hemodynamics, including coronary perfusion pressure, systemic O2 consumption, and arterial blood gases, were recorded throughout the study. Plasma samples for endothelin-1 and cathecolamines were drawn before and after CA. Compared with fentanyl/fluanisone/midazolam anesthesia, isoflurane resulted in a shorter time to return of spontaneous circulation (ROSC), less use of epinephrine, increased coronary perfusion pressure during cardiopulmonary resusitation, higher mean arterial pressure post-ROSC, increased plasma levels of endothelin-1, and decreased levels of epinephrine. The choice of anesthesia did not affect ROSC rate or systemic O2 consumption. Isoflurane reduces time to ROSC, increases coronary perfusion pressure, and improves hemodynamic function, all of which are important parameters in CA models.

NEW & NOTEWORTHY The preconditioning effect of volatile anesthetics in studies of ischemia-reperfusion injury has been demonstrated in several studies. This study shows the importance of anesthesia in experimental cardiac arrest studies as isoflurane raised coronary perfusion pressure during resuscitation, reduced time to return of spontaneous circulation, and increased arterial blood pressure in the post-cardiac arrest period. These effects on key outcome measures in cardiac arrest research are important in the interpretation of results from animal studies.

1H NMR-metabolomics: can they be a useful tool in our understanding of cardiac arrest?

OBJECTIVE

This review focuses on the presentation of the emerging technology of metabolomics, a promising tool for the detection of identifying the unrevealed biological pathways that lead to cardiac arrest.

DATA SOURCES

The electronic bases of PubMed, Scopus, and EMBASE were searched. Research terms were identified using the MESH database and were combined thereafter. Initial search terms were "cardiac arrest", "cardiopulmonary resuscitation", "post-cardiac arrest syndrome" combined with "metabolomics".

RESULTS

Metabolomics allow the monitoring of hundreds of metabolites from tissues or body fluids and already influence research in the field of cardiac metabolism. This approach has elucidated several pathophysiological mechanisms and identified profiles of metabolic changes that can be used to follow the disease processes occurring in the peri-arrest period. This can be achieved through leveraging the strengths of unbiased metabolome-wide scans, which include thousands of final downstream products of gene transcription, enzyme activity and metabolic products of extraneously administered substances, in order to identify a metabolomic fingerprint associated with an increased risk of cardiac arrest.

CONCLUSION

Although this technology is still under development, metabolomics is a promising tool for elucidating biological pathways and discovering clinical biomarkers, strengthening the efforts for optimizing both the prevention and treatment of cardiac arrest.

Endothelin-1 attenuates the hemodynamic response to exogenous epinephrine in a porcine ischemic ventricular fibrillation cardiac arrest model

Endothelin-1 (ET-1) increases in the ischemically induced ventricular fibrillation (VF) swine model of cardiac arrest and affects outcome by potentially attenuating the hemodynamic response to epinephrine. Fifty-one swine underwent percutaneous left anterior descending occlusion. Seven minutes postonset of ischemic VF, cardiopulmonary resuscitation (CPR) was initiated. If VF persisted after 3 shocks, 1 mg of epinephrine was given. ET-1 (collected at baseline and every 5 min until VF onset) was assayed with ELISA. Bayesian multivariate logistic regression analysis compared peak ET-1 levels with the binary outcome of a positive coronary perfusion pressure response of >20 mmHg following epinephrine. Sixteen animals (31%) failed to achieve a positive response. Restoration of spontaneous circulation (ROSC) was observed in 1/16 (6.3%) of epinephrine nonresponders and 20/35 (57.1%) of epinephrine responders (P = 0.0006). The median peak ET-1 level was 2.71 pg/mL [interquartile range (IQR) 1.06-4.40] in nonresponders and 1.69 pg/mL (IQR 0.99-2.35) in responders. ET-1 levels were inversely associated with epinephrine response with a median posterior odds ratio (OR) of a coronary perfusion pressure response of 0.72 (95% confidence interval [CI] 0.48-1.06) for each one-unit increase in ET-1 and a probability that the associated OR is <1 of 0.95. Peak ET-1 levels predict a lack of a hemodynamic response to epinephrine during treatment of cardiac arrest during ischemic VF.

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.

Plasma endothelin-1 level at the onset of ischemic ventricular fibrillation predicts resuscitation outcome

BACKGROUND

Endogenous vasopressors, including endothelin-1 (ET-1), have been shown to be elevated in patients following resuscitation from out-of-hospital cardiac arrest and are likely a physiologic response to global ischaemia. The importance of ET-1 in the setting of arrest and resuscitation has not been established. Prior work has demonstrated that ET-1 increases significantly after coronary occlusion. The purpose of this study was to assess changes in ET-1 following induction of ischaemia and VF.

METHODS

VF was induced in 30 anesthetized and instrumented swine by balloon occlusion of the LAD. Blood was collected from the right atrium at baseline and at 5 min intervals following LAD occlusion until VF occurred. After 7 min of VF, resuscitation was attempted in accordance with guidelines. ET-1 and matrix metalloproteinase-9 (MMP-9), a measure of infarct size, were measured using ELISA.

RESULTS

ET-1 and MMP-9 levels increased significantly from baseline within 20 min of occlusion of the LAD. Animals that could not be resuscitated had a higher ET-1 (p=0.031) at VF onset but similar ischaemia time (time to VF) and MMP-9, reflecting infarct size. An ET-1 level >4 pg/ml had a likelihood ratio of 4 for predicting resuscitation failure.

CONCLUSIONS

Elevated levels of ET-1 during acute ischaemia predict resuscitation failure independent of the time to VF. This finding may be due to the known effect of ET-1 on coronary vascular resistance or ventricular compliance, resulting in early ischemic contracture.

Postresuscitation myocardial stunning and its outcome: new approaches

What is the successful cardiopulmonary resuscitation? It is the few minutes postcardiopulmonary arrest that can answer. Twenty to 40 percent of patients who sustained cardiac arrest are initially resuscitated, but only 10% survive to hospital discharge, and more than 60% of victims succumb within 24 hours. This high fatality rate in the early hours and days after successful resuscitation is mainly related to the acute, intense, and reversible form of postresuscitation myocardial dysfunction (stunning) together with the ventricular tachyarrhythmia. It is a reversible process, provided that we are aware of the pertinent pathophysiology and then intervene accordingly. Herein I reviewed most of the published relevant articles concerning the causes, underlying mechanism, and the updated trials for management of postresuscitation myocardial stunning. I do agree that not only the restoration of the circulation but also long-term outcome should be the aim of resuscitation, and I readdress the role of epinephrine, dobutamine, biphasic defibrillator, with the new promising agent (ie, potassium channel opener), Delta-opioid receptor agonist, unloading intracellular calcium, antioxidants, and therapeutic hypothermia to halt this period of stunning. This will improve the outcome of the resuscitation efforts.

Drug administration in animal studies of cardiac arrest does not reflect human clinical experience

INTRODUCTION

To date, there is no evidence showing a benefit from any advanced cardiac life support (ACLS) medication in out-of-hospital cardiac arrest (OOHCA), despite animal data to the contrary. One explanation may be a difference in the time to first drug administration. Our previous work has shown the mean time to first drug administration in clinical trials is 19.4min. We hypothesized that the average time to drug administration in large animal experiments occurs earlier than in OOHCA clinical trials.

METHODS

We conducted a literature review between 1990 and 2006 in MEDLINE using the following MeSH headings: swine, dogs, resuscitation, heart arrest, EMS, EMT, ambulance, ventricular fibrillation, drug therapy, epinephrine, vasopressin, amiodarone, lidocaine, magnesium, and sodium bicarbonate. We reviewed the abstracts of 331 studies and 197 full manuscripts. Exclusion criteria included: non-peer reviewed, all without primary animal data, and traumatic models. From these, we identified 119 papers that contained unique information on time to medication administration. The data are reported as mean, ranges, and 95% confidence intervals. Mean time to first drug administration in animal laboratory studies and clinical trials was compared with a t-test. Regression analysis was performed to determine if time to drug predicted ROSC.

RESULTS

Mean time to first drug administration in 2378 animals was 9.5min (range 3.0-28.0; 95% CI around mean 2.78, 16.22). This is less than the time reported in clinical trials (19.4min, p<0.001). Time to drug predicted ROSC (odds ratio 0.844; 95% CI 0.738, 0.966).

CONCLUSION

Shorter drug delivery time in animal models of cardiac arrest may be one reason for the failure of animal studies to translate successfully into the clinical arena.

The resuscitation outcome: revisit the story of the stony heart

Postresuscitation syndrome is a state of myocardial dysfunction after the restoration of circulation by successful resuscitation. Despite several advances in the field of resuscitation, the management of out-of-hospital cardiac arrest is still suboptimal. The high fatality rate shortly after successful resuscitation is mainly related to postresuscitation myocardial dysfunction. Postresuscitation myocardial stunning is reversible, while stony heart is irreversible due to prolonged unsuccessful resuscitation. This article reviews most of the published articles concerning the causes, mechanism, pathophysiology, and the updated trials for management of postresuscitation myocardial dysfunction. Further studies are warranted to highlight postresuscitation disease and its hemodynamic sequences and then to intervene according to the different phases of cardiac arrest. By modifying the conventional modalities of resuscitation together with new promising agents, the rescuers will be able to salvage the jeopardized postresuscitation myocardium and prevent its progression to the dismal stony heart. Community awareness and staff education are crucial to shorten resuscitation time and improve short-term and long-term outcomes. There is an urgent need to revise the guidelines for cardiopulmonary resuscitation in community setting, but how? It is a matter of where and when it is of enough value to be efficacious and cost-effective.

Reversible myocardial dysfunction after cardiopulmonary resuscitation

OBJECTIVE

Myocardial stunning frequently has been described in patients with an acute coronary syndrome. Recently, it has also been described in critically ill patients without ischaemic heart disease. It is possible that the most severe form of any syndrome, leading to cardio-respiratory arrest, may cause myocardial stunning. Myocardial stunning appears to have been demonstrated in experimental studies, though this phenomenon has not been sufficiently studied in human models. The aim of the present work has been to study and describe the possible development of myocardial dysfunction in patients resuscitated after cardio-respiratory arrest, in the absence of acute or previous coronary artery disease.

DESIGN

Descriptive study of a case series.

SETTING

The intensive care unit (ICU) of a provincial hospital.

PATIENTS AND PARTICIPANTS

The study period was from April 1999 to June 2001. All patients admitted to the ICU with critical, non-coronary artery pathology, with no past history of cardiac disease, and those who were resuscitated after cardio-respiratory arrest, were included in the study.

MEASUREMENTS AND RESULTS

Transthoracic and transoesophageal echocardiography was used to assess left ventricular ejection fraction (LVEF) and disturbances of segmental contractility. This study was carried out within the first 24h after admission, during the first week, during the second or third week, after 1 month, and between 3 and 6 months. Twenty-nine patients with a median age of 65 years (range 24--76) were included in the study. Twelve patients died. Twenty patients developed myocardial dysfunction; the initial LVEF in these patients was 0.28 (0.12--0.51), showing improvement over time in the patients who survived. All of these patients presented disturbances of segmental contractility which also became normal over time.

CONCLUSIONS

After successful CPR, reversible myocardial dysfunction, consisting of systolic myocardial dysfunction and disturbances of segmental contractility, may occur.

Echocardiographic comparison of cardiopulmonary resuscitation (CPR) using periodic acceleration (pGz) versus chest compression

OBJECTIVE

This investigation compared the effects of conventional cardiopulmonary resuscitation (CPR) using an automated Thumper chest compression device to periodic acceleration CPR (pGz-CPR) on early post-resuscitation ventricular function assessed by echocardiography, in an adult pig model of CPR.

BACKGROUND

Whole body periodic acceleration along the spinal axis (pGz) is a new method of cardiopulmonary resuscitation (CPR). Biomechanical forces and biochemical release produced by pGz impart ventilation and increase blood flow. Our laboratory has reported normal neurological and cardiovascular function 48 h after return of spontaneous circulation in animals that have undergone 22 min of pGz-CPR.

METHODS

Ventricular fibrillation (VF) was induced in 16 animals (25-35 kg). After 3 min of non-interventional period, the animals were randomized to receive either pGz-CPR or Thumper-CPR for 15 min. After 18 min of VF, a single dose of vasopressin and bicarbonate were administered and defibrillation attempted. An echocardiogram was performed at baseline and serially for 6h. Ejection fraction (EF), fractional shortening (FS) and wall motion were assessed by 2D and M-mode echocardiography.

RESULTS

Return of spontaneous circulation to 360 min occurred in 5/8 (62%) of the animals receiving Thumper-CPR and in 7/8 (88%) receiving pGz-CPR. FS and EF were impaired after CPR, but pGz-CPR animals had less impairment than Thumper-CPR animals. Further, wall motion score index (WMSI) was more impaired after Thumper-CPR and remained as such even 6h post-CPR.

CONCLUSION

pGz holds promise as a new method for CPR with better left ventricular (LV) function post-CPR than the more traditional chest compression method.

Vasopressor agents: old and new components

PURPOSE OF REVIEW

In settings of cardiac arrest, reestablishing vital organ perfusion plays an important role in initial CPR. As a pharmacologic intervention, vasopressor agents aim to improve aortic diastolic pressure and, consequently, coronary and cerebral perfusion pressures.

RECENT FINDINGS

Historically, adrenergic agonists such as epinephrine have been suggested for routine use in CPR. However, epinephrine's efficacy is controversial because of its unfavorable inotropic and chronotropic action. This has prompted research into the use of alternative pressor agents with more promising hemodynamic features; these include selective alpha 2-adrenergic agonists and other nonadrenergic vasoconstrictors such as vasopressin.

SUMMARY

In this article, the main traditional and novel adrenergic and nonadrenergic vasopressor drugs are reviewed.

Survival with full neurologic recovery after prolonged cardiopulmonary resuscitation with a combination of vasopressin and epinephrine in pigs

We sought to determine the effects of a combination of vasopressin and epinephrine on neurologic recovery in comparison with epinephrine alone and saline placebo alone in an established porcine model of prolonged cardiopulmonary resuscitation (CPR). After 4 min of cardiac arrest, followed by 3 min of basic life support CPR, 17 animals were randomly assigned to receive, every 5 min, either a combination of vasopressin and epinephrine (vasopressin [IU/kg]/epinephrine [ micro g/kg]: 0.4/45, 0.4/45, and 0.8/45; n = 6), epinephrine alone (45, 45, and 200 micro g/kg; n = 6), or saline placebo alone (n = 5). After 22 min of cardiac arrest, including 18 min of CPR, defibrillation was attempted to achieve the return of spontaneous circulation. Aortic diastolic pressure was significantly (P < 0.01) increased 90 s after each of 3 vasopressin/epinephrine injections versus epinephrine alone versus saline placebo alone (mean +/- SEM: 69 +/- 3 mm Hg versus 45 +/- 3 mm Hg versus 29 +/- 2 mm Hg, 63 +/- 4 mm Hg versus 27 +/- 3 mm Hg versus 23 +/- 1 mm Hg, and 52 +/- 4 mm Hg versus 21 +/- 3 mm Hg versus 16 +/- 3 mm Hg, respectively). Spontaneous circulation was restored in six of six vasopressin/epinephrine pigs, whereas six of six epinephrine and five of five saline placebo pigs died (P < 0.01). Neurologic evaluation 24 h after successful resuscitation revealed only an unsteady gait and was normal 5 days after the experiment in all vasopressin/epinephrine-treated animals. In conclusion, in this porcine model of prolonged CPR, repeated vasopressin/epinephrine administration, but not epinephrine or saline placebo alone, ensured long-term survival with full neurologic recovery.

IMPLICATIONS

We present a study to evaluate the effects of a combination of vasopressin and epinephrine during prolonged cardiopulmonary resuscitation on neurological outcome in pigs. We found that all pigs treated with a combination of vasopressin and epinephrine could be resuscitated and had full neurologic recovery observed over an entire period of 5 days.

Endothelin-1 elevates regional cerebral perfusion during prolonged ventricular fibrillation cardiac arrest in pigs

Since adrenaline (epinephrine) also has negative effects during and after cardiopulmonary resuscitation (CPR) a non-adrenergic vasoconstrictor like endothelin might be an alternative to increase vital organ blood flow. We studied the effect of different doses of endothelin-1 compared with adrenaline on the ability to resuscitate, cerebral and myocardial blood flow (MBF) in a closed chest cardiac arrest pig model. After 5 min of ventricular fibrillation, CPR with a ventilator and a mechanical compression device was started. At 10 min, 31 pigs were randomized to receive a single dose of endothelin-1 50, 100 or 200 microg or repeated doses of adrenaline 0.04 mg kg(-1) or saline every 3 min. After 25 min, the pigs were defibrillated to achieve restoration of spontaneous circulation. Blood flow was measured with the fluorescent microsphere method. In animals receiving endothelin-1 50, 100 and 200 microg the cerebral blood flow (CBF) increased from median 28 (25th; 75th quartile: 16; 40), 32 (15; 48) and 17 (4; 65) to 36 (31; 54), 47 (39; 57) and 63 (35; 83) ml min(-1) per 100 g, respectively, 6 min after drug administration (P<0.05 endothelin-1 50 microg vs. Control, P<0.01 endothelin-1 100 and 200 microg vs. Control). At the same time CBF decreased in the control and adrenaline group from 36 (21; 41) and 39 (15; 50) to 12 (2; 25) and 24 (15; 26) ml min(-1) per 100 g, respectively, (P<0.05 adrenaline vs. endothelin-1 200 microg). There was no difference in MBF between the treatment groups despite a higher coronary perfusion pressure (CoPP) in the endothelin-1 groups. Restoration of spontaneous circulation could be only achieved in the endothelin-1 50 microg (3 of 7; 43%) and 100 microg (5 of 7; 71%) group. This study suggests that endothelin-1 enhances CBF during CPR better than adrenaline and increases resuscitation success.

Reversible myocardial dysfunction in critically ill, noncardiac patients: a review

OBJECTIVE

To review reversible myocardial dysfunction affecting critically ill patients without cardiac pathology.

DATA SOURCES

The bibliography for the study was compiled through a search of different databases for the period 1966-2001. References cited in the selected articles also were reviewed.

STUDY SELECTION

The selection criteria included all articles published on reversible myocardial dysfunction in critically ill patients.

CONCLUSIONS

Reversible myocardial dysfunction may develop in a situation of critical pathology, but the etiology of reversible myocardial dysfunction is not fully understood. This dysfunction may be accompanied by increases in enzyme concentrations and electrocardiographic changes. Reversible myocardial dysfunction probably is underdiagnosed, although its presence is associated with a worsening of the prognosis and with more specific therapeutic options. Further studies are necessary to define its true incidence and clinical implications.

Postresuscitation myocardial dysfunction

Postresuscitation myocardial dysfunction is common after prolonged cardiac arrest and can have life-threatening consequences. Experimental data suggest that systolic and diastolic left ventricular function can be adversely effected following successful resuscitation. Such dysfunction can resolve and represents true global myocardial stunning. Identified factors contributing to postresuscitation myocardial dysfunction include prolonged CPR, use of vasoconstricting drugs, and high-energy defibrillation. Potential treatments include dobutamine, KATP channel activators, and 21-aminosteroids. In the author's efforts to improve long-term survival from cardiac arrest, more attention is needed to the postresuscitation period.

Inhibition of nitric oxide improves coronary perfusion pressure and return of spontaneous circulation in a porcine cardiopulmonary resuscitation model

OBJECTIVE

During spontaneous circulation, nonspecific inhibition of nitric oxide synthase by N(G)-nitro-L-arginine methyl ester (L-NAME) increases systemic vascular resistance and, therefore, mean arterial pressure. If this effect can be extrapolated to cardiopulmonary resuscitation (CPR), administering L-NAME during CPR may be beneficial by maintaining or even improving coronary perfusion pressure, and hence successful defibrillation.

DESIGN

Prospective, randomized laboratory investigation using an established porcine model with instrumentation for hemodynamic variables, blood gases, and defibrillation attempt.

SETTING

University medical center experimental laboratory.

SUBJECTS

Ten domestic pigs.

INTERVENTIONS

After 4 mins of ventricular fibrillation, ten animals were randomly assigned to receive L-NAME (25 mg/kg; n = 5) or saline placebo (n = 5) (given in two doses) after 3 and 13 mins of CPR, respectively. Defibrillation was provided 5 mins after the second dose of active drug or placebo.

MEASUREMENTS AND MAIN RESULTS

Mean +/- sem coronary perfusion pressure was significantly (p < .05) higher 90 secs (27 +/- 3 vs. 17 +/- 3 mm Hg), 10 mins (28 +/- 3 vs. 14 +/- 2 mm Hg), and 15 mins (21 +/- 5 vs. 7 +/- 3 mm Hg) after the first L-NAME administration compared with saline placebo. Mean +/- sem coronary perfusion pressure remained significantly higher 90 secs and 5 mins after the second L-NAME vs. saline placebo administration (19 +/- 4 vs. 6 +/- 4 mm Hg, and 17 +/- 3 vs. 4 +/- 4 mm Hg). After 22 mins of cardiac arrest, including 18 mins of CPR, four of five pigs in the L-NAME group were successfully defibrillated, and survived the 60-min postresuscitation phase. In the placebo group, none of five pigs could be defibrillated successfully (p < .05).

CONCLUSIONS

Nonspecific blockade of nitric oxide synthase with L-NAME during CPR was associated with an increase in coronary perfusion pressure and resulted in significantly better initial resuscitation when compared with saline placebo.

Vasopressin and endothelin during cardiopulmonary resuscitation

Vital organ blood flow during cardiopulmonary resuscitation (CPR) and neurologic recovery after CPR were significantly better in pigs treated with vasopressin compared with epinephrine. Furthermore, two clinical studies evaluating both out-of-hospital and inhospital cardiac arrest patients found higher 24-hr survival rates in patients who were resuscitated with vasopressin compared with epinephrine. Scientists at the Leopold Franzens University in Innsbruck, Austria, are currently coordinating a multicenter, randomized clinical trial under the aegis of the European Resuscitation Council to study the effects of vasopressin vs. epinephrine in out-of-hospital cardiac arrest patients. Results of anticipated 1,500 enrolled patients may be available in 2001 and may help to determine the role of vasopressin during CPR. Another new, recently studied vasopressor for CPR is endothelin-1. To date, this vasopressor has only been studied as an intervention in animal CPR models, although plasma levels have been investigated in cardiac arrest patients. Initial reports found improved coronary perfusion pressure when combined with epinephrine. However, the CPR research group of the University of Arizona Sarver Heart Center found excessive vasoconstriction and worse survival than with epinephrine alone.