Effect of continuous compressions and 30:2 cardiopulmonary resuscitation on global ventilation/perfusion values during resuscitation in a porcine model

2024 RECOVER Guidelines: Basic Life Support. Evidence and knowledge gap analysis with treatment recommendations for small animal CPR

OBJECTIVE

To systematically review evidence and devise treatment recommendations for basic life support (BLS) in dogs and cats and to identify critical knowledge gaps.

DESIGN

Standardized, systematic evaluation of literature pertinent to BLS following Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Prioritized questions were each reviewed by 2 Evidence Evaluators, and findings were reconciled by BLS Domain Chairs and Reassessment Campaign on Veterinary Resuscitation (RECOVER) Co-Chairs to arrive at treatment recommendations commensurate to quality of evidence, risk to benefit relationship, and clinical feasibility. This process was implemented using an Evidence Profile Worksheet for each question that included an introduction, consensus on science, treatment recommendations, justification for these recommendations, and important knowledge gaps. A draft of these worksheets was distributed to veterinary professionals for comment for 4 weeks prior to finalization.

SETTING

Transdisciplinary, international collaboration in university, specialty, and emergency practice.

RESULTS

Twenty questions regarding animal position, chest compression point and technique, ventilation strategies, as well as the duration of CPR cycles and chest compression pauses were examined, and 32 treatment recommendations were formulated. Out of these, 25 addressed chest compressions and 7 informed ventilation during CPR. The recommendations were founded predominantly on very low quality of evidence and expert opinion. These new treatment recommendations continue to emphasize the critical importance of high-quality, uninterrupted chest compressions, with a modification suggested for the chest compression technique in wide-chested dogs. When intubation is not possible, bag-mask ventilation using a tight-fitting facemask with oxygen supplementation is recommended rather than mouth-to-nose ventilation.

CONCLUSIONS

These updated RECOVER BLS treatment recommendations emphasize continuous chest compressions, conformation-specific chest compression techniques, and ventilation for all animals. Very low quality of evidence due to absence of clinical data in dogs and cats consistently compromised the certainty of recommendations, emphasizing the need for more veterinary research in this area.

Anisodamine hydrobromide ameliorates cardiac damage after resuscitation

The microcirculation is correlated with the prognosis of patients with cardiac arrest and changes after resuscitation. In the present study, the effects of anisodamine hydrobromide (AH) on microcirculation was investigated and its potential mechanisms were explored. A total of 24 pigs were randomly grouped into three groups (n=8): Sham, Saline and AH group. After pigs were anesthetized, intubated and mechanically ventilated, ventricular fibrillation was induced by electrical stimulation. After 8 min, cardiopulmonary resuscitation was given to the restoration of spontaneous circulation (ROSC). Arteriovenous blood was collected at baseline and 0, 1, 2, 4 and 6 h after ROSC to measure blood gas and cytokines. Perfused vessel density (PVD) and microvascular flow index (MFI) were measured to reflect the microcirculation. Continuous cardiac output and global ejection fraction were measured to indicate hemodynamics. Compared with Sham group, PVD and MFI in the intestines and the sublingual regions decreased significantly after resuscitation. The microcirculation recovered faster in the AH group than the SA group. The decrease of intestinal microcirculatory blood flow was closely related to the decrease of sublingual microcirculatory blood flow. The cardiac function was impaired after resuscitation, and a decrease of IFN-γ as well as IL-2 and an increase of IL-4 as well as IL-10 suggested the immune imbalance. The microcirculation changes in sublingual regions were closely related to the changes in intestines. AH could improve the immune imbalance after resuscitation and was beneficial to the recovery of cardiac function.

The protective effects of phosphodiesterase-5 inhibitor, sildenafil on post-resuscitation cardiac dysfunction of cardiac arrest: by regulating the miR-155-5p and miR-145-5p

Background

MiRNA-155 and miRNA-145 have been demonstrated to function as a key regulator in the development of the cardiovascular system. Recent experimental and clinical studies have indicated the cardioprotective role of sildenafil during ischemia/reperfusion (I/R) injury. This study was designed to investigate if administration of sildenafil will attenuate post-resuscitation myocardial dysfunction by regulating miRNA-155 and miR-145 expressions.

Methods

Thirty-two male pigs (weighing 30 ± 2 kg) were randomly divided into 4 groups, sildenafil group (n = 8), sildenafil +NG-nitro-l-arginine methyl ester (L-NAME) (20 mg/kg L) group (n = 8), saline (SA group, n = 8); and sham operation group (sham group, n = 8). Eight minutes of untreated VF was followed by defibrillation in anesthetized, closed-chest pigs. Hemodynamic status and blood samples were obtained at 0 min, 0.5, 1, 2, 4 and 6 h after return of spontaneous circulation (ROSC), and the hearts were removed and analyzed under electron microscopy, quantitative real-time polymerase chain reaction and ultra structural analysis were performed to evaluate myocardial injury.

Results

Compared with the sildenafil + L-NAME and saline groups, the sildenafil group had better outcomes in terms of hemodynamic and oxygen metabolism parameters as well as 24-h survival rate, and attenuated myocardial injury; In this study, CA pigs showed evidently increased levels of miR-155-5p and miR-145-5p, while the sildenafil treatment decreased the levels of miR-155-5p and miR-145-5p in CA pigs. In addition, the levels of eNOS was decreased in CA pigs, validating sildenafil attenuating post-resuscitation myocardial dysfunction by regulating miRNA-155 and miR-145 expressions.

Conclusions

Sildenafil group had better outcomes in terms of hemodynamic and oxygen metabolism parameters as well as 24-h survival rate, inhibited the increases in the miR-155-5p and miR-145-5p levels and attenuated myocardial injury in a porcine model of CA and resuscitation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13049-020-00819-5.

Duration of cardiac arrest requires different ventilation volumes during cardiopulmonary resuscitation in a pig model

There are few studies examining the ventilation strategies recommended by current CPR guidelines. We investigated the influence of different minute volume applying to untreated cardiac arrest with different duration, on resuscitation effects in a pig model. 32 Landrace pigs with 4 or 8 min (16 pigs each) ventricular fibrillation (VF) randomly received two ventilation strategies during CPR. "Guideline" groups received mechanical ventilation with a tidal volume of 7 ml/kg and a frequency of 10/min, while "Baseline" groups received a tidal volume (10 ml/kg) and a frequency used at baseline to maintain an end-tidal PCO₂ (P_ETCO₂) between 35 and 40 mmHg before VF. Mean airway pressures and intrathoracic pressures (P_IT) in the Baseline-4 min group were significantly higher than those in the Guideline-4 min group (all P < 0.05). Similar results were observed in the 8 min pigs, except for no significant difference in minimal P_IT and P_ETCO₂ during 10 min of CPR. Venous pH and venous oxygen saturation were significantly higher in the Baseline-8 min group compared to the Guideline-8 min group (all P < 0.05). Aortic pressure in the Baseline-8 min group was higher than in the Guideline-8 min group. Seven pigs in each subgroup of 4 min VF models achieved the return of spontaneous circulation (ROSC). Higher ROSC was observed in the Baseline-8 min group than in the Guideline-8 min group (87.5% vs. 37.5%, P = 0.039). For 4 min VF but not 8 min VF, a guideline-recommended ventilation strategy had satisfactory results during CPR. A higher minute ventilation resulted in better outcomes for subjects with 8 min of untreated VF through thoracic pump.

A survey of ventilation strategies during cardiopulmonary resuscitation

BACKGROUND

Many controversies still exist regarding ventilator parameters during cardiopulmonary resuscitation (CPR). This study aimed to investigate the CPR ventilation strategies currently being used among physicians in Chinese tertiary hospitals.

METHODS

A survey was conducted among the cardiac arrest team physicians of 500 tertiary hospitals in China in August, 2018. Surveyed data included physician and hospital information, and preferred ventilation strategy during CPR.

RESULTS

A total of 438 (88%) hospitals completed the survey, including hospitals from all 31 mainland Chinese provinces. About 41.1% of respondents chose delayed or no ventilation during CPR, with delayed ventilations all starting within 12 minutes. Of all the respondents who provided ventilation, 83.0% chose to strictly follow the 30:2 strategy, while 17.0% chose ventilations concurrently with uninterrupted compressions. Only 38.3% respondents chose to intubate after initiating CPR, while 61.7% chose to intubate immediately when resuscitation began. During bag-valve-mask ventilation, only 51.4% of respondents delivered a frequency of 10 breaths per minute. In terms of ventilator settings, the majority of respondents chose volume control (VC) mode (75.2%), tidal volume of 6-7 mL/kg (72.1%), PEEP of 0-5 cmH₂O (69.9%), and an FiO₂ of 100% (66.9%). However, 62.0% of respondents had mistriggers after setting the ventilator, and 51.8% had high pressure alarms.

CONCLUSION

There is a great amount of variability in CPR ventilation strategies among cardiac arrest team physicians in Chinese tertiary hospitals. Guidelines are needed with specific recommendations on ventilation during CPR.

Effects of Mild Hypothermia on Cardiac and Neurological Function in Piglets Under Pathological and Physiological Stress Conditions

To investigate the different effects of mild hypothermia on pathological and physiological stress conditions in piglets, 30 pigs were randomized into four groups: cardiac arrest and mild hypothermia (CA-MH group), cardiac arrest and normothermia (CA-NH group), non-CA-MH (NCA-MH group), and a sham operation. The same hypothermia intervention was implemented in both CA-MH and NCA-MH groups. The CA-NH group did not undergo therapeutic hypothermia after resuscitation. The hemodynamic parameters were recorded. Cerebral metabolism variables and neurotransmitters in the extracellular fluid were collected through microdialysis tubes. The serum of venous blood was used to detect levels of inflammatory factors. The cerebral function was evaluated. At 24 and 72 hours after resuscitation, the cerebral performance category and neurological deficit score in the CA-NH group had higher values. Heart rate and cardiac output (CO) in the CA-MH group during cooling were lower than that of the CA-NH group, but CO was higher after rewarming. Glucose was higher during cooling, and extracellular lactate and lactate/pyruvate ratio in the CA-MH group were lower than that of the CA-NH group. Noradrenaline and 5-hydroxytryptamine in the CA-MH and NCA-MH groups were lower than that of the CA-NH group and sham group during cooling, respectively. Inflammatory factor levels, including interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-8, and tumor necrosis factor-α, in the CA-MH group were lower than that of the CA-NH group at cooling for 12 hours. These values in the NCA-MH group were higher than that of the sham group. Under a light and an electron microscope, the worse pathological results of heart and brain were observed in the two cardiac arrest groups. Mild hypothermia can provide limited organ protection in the specific pathological condition caused by ischemia-reperfusion, but it may produce a negative effect in a normal physiological state.

CPR feedback/prompt device improves the quality of hands-only CPR performed in manikin by laypersons following the 2015 AHA guidelines

PURPOSE

We investigated the effects of a cardiopulmonary resuscitation (CPR) feedback/prompt device on the quality of chest compression (CC) during hands-only CPR following the 2015 AHA guidelines.

METHODS

A total of 124 laypersons were randomly assigned into three groups. The first (n=42) followed the 2010 guidelines, the second (n=42) followed the 2015 guidelines with no feedback/prompt device, the third (n=40) followed the 2015 guidelines with a feedback/prompt device (2015F). Participants underwent manual CPR training and took a written basic life support examination, then required to perform 2min of hands-only CPR monitored by a CPR feedback/prompt device. The quality of CPR was quantified as the percentage of correct CCs (mean CC depth and rate, complete recoil and chest compression fraction (CCF)) per 20s, as recorded by the CPR feedback/prompt device.

RESULTS

Significantly higher correct ratios of CC, CC depth, and rate were achieved in the 2010 group in each minute vs the 2015 group. The greater mean CC depth and rate were observed in the 2015F group vs the 2015 group. The correct ratio of CC was significantly higher in the 2015F group vs the 2015 group. CCF was also significantly higher in the 2015F group vs the 2015 group in the last 20s of CPR.

CONCLUSIONS

It is difficult for a large percentage of laypersons to achieve the targets of CC depth and rate following the 2015 AHA guidelines. CPR feedback/prompt devices significantly improve the quality of hands-only CPR performance by laypersons following the standards of the 2015 AHA guidelines.

Ventilation during cardiopulmonary resuscitation in children: a survey on clinical practice

BACKGROUND

This study aimed to investigate the ventilation practice during cardiopulmonary resuscitation (CPR) and after return of spontaneous circulation (ROSC) in children.

METHODS

An online survey of CPR practices was designed and sent to healthcare professionals treating children.

RESULTS

A total of 477 healthcare professionals from 46 countries responded to this survey; 92.7% were physicians and 64.2% worked in pediatric intensive care units. Specific CPR guidelines were used by 97.7% of respondents. The respiratory rate most frequently used for children over 12 months was 13 to 20 respirations per minute (rpm) (46% in intubated and 41.8% in non-intubated). For infants under 12 months, the most frequently used respiratory rate was 21 to 30 rpm in intubated patients (37.3%): in non-intubated infants, 13 to 20 rpm (26.5%) and 21 to 30 rpm (26.5%) were used with the same frequency. In North America, the respiratory rate most widely used was 7 to 12 rpm; higher rates (13 to 20 rpm and 21 to 30 rpm) were used in Europe and Latin America (P<0.001). After ROSC, no significant differences in the respiratory rates used were found between the continents. More than 40% of healthcare professionals had a target oxygen saturation below 94%; more than 10% used a target arterial PCO₂ below 35 mmHg and more than 13% above 45 mmHg.

CONCLUSIONS

There is considerable variation in the management of ventilation of children in cardiac arrest, and international recommendations are not being followed in a high percentage of cases.

Effect of mild hypothermia on renal ischemia/reperfusion injury after cardiopulmonary resuscitation in a swine model

Purpose:

To investigate the effect of intravascular cooling on renal function after resuscitation.

Methods:

Twenty four pigs were randomized into three groups (n=8 in each group): therapeutic hypothermia group (TH group), normothermia group (NH group) and sham operation group (SHAM group). After 6 minutes of untreated VF, CPR was performed. Upon ROSC, the TH group received the intravascular cooling. The NH and SHAM group did not undergo therapeutic hypothermia. Haemodynamic parameters were recorded. The bloods were analyzed for serum creatinine (sCr), CysC and NGAL. The kidney was surgically removed observe pathologic changes under a light microscope.

Results:

The sCr increased in both TH and NH groups after ROSC, compared to baseline. Between two groups, the sCr and creatinine clearance (Cc) showed lower level in the TH group. The urine volume per hour in the TH group were higher during cooling. After resuscitation, NGAL and CysC in the NH group were higher than in the TH group. Under the light microscope, compared with the TH group, the renal injury was prominent in the NH group.

Conclusion:

Mild hypothermia had a protection to renal ischemia reperfusion injury after resuscitation.

Sudden cardiac death

INTRODUCTION

Sudden cardiac arrest continues to be the leading cause of death in the industrialized world.

SOURCES OF DATA

Original papers, reviews and guidelines.

AREAS OF AGREEMENT

Community programs for lay bystander cardiopulmonary resuscitation (CPR) and automatic external defibrillation improve outcomes. Post-arrest care, including targeted temperature management (TTM) combined with early coronary angiography and percutaneous coronary intervention, is helpful for those suffering cardiac arrest during an ST-segment elevation myocardial infarction.

AREAS OF CONTROVERSY

(1) The optimal approach to encourage lay bystanders to assist with resuscitation efforts. (2) Whether TTM combined with early coronary angiography is cost effective for those without ST elevation on their post-arrest ECG is unknown.

GROWING POINTS

Increasing data show that chest compression-only CPR is preferred by lay rescuers and improves local survival rates.

AREAS TIMELY FOR DEVELOPING RESEARCH

Randomized clinical trials are underway to examine the utility of early coronary angiography in the treatment of post-arrest patients without ST-segment elevation.

Comparison of early sequential hypothermia and delayed hypothermia on neurological function after resuscitation in a swine model

BACKGROUND

We utilized a porcine cardiac arrest model to compare early sequential hypothermia (ESH) with delayed hypothermia (DH) and no hypothermia (NH) to investigate the different effects on cerebral function after resuscitation.

METHODS

After return of spontaneous circulation (ROSC), resuscitated 24 pigs divided into three groups. The ESH group implemented early sequential hypothermia immediately, and the DH group implemented delayed hypothermia at 1 h after ROSC. The core temperature, hemodynamic parameters and oxygen metabolism were recorded. Cerebral metabolism variables and neurotransmitter in the extracellular fluid were collected through the microdialysis tubes. The bloods were analyzed for venous jugular bulb oxygen saturation, lactate and neuron specific nolase. The cerebral function was evaluated using the cerebral performance category and neurologic deficit score at 72h after ROSC and cerebral histology in the right posterior frontal lobe were collected.

RESULTS

ESH reached the target temperature earlier and showed more favorable outcomes of neurological function than DH. Specifically, early sequential hypothermia reduced cerebral oxygen and energy consumption and decreased extracellular accumulation of neurotransmitters after resuscitation and protected the integrity of the BBB during reperfusion.

CONCLUSIONS

Early sequential hypothermia could increase the protection of neurological function after resuscitation and produce better neurological outcomes. The institutional protocol number: 2010-D-013.

Enalapril protects against myocardial ischemia/reperfusion injury in a swine model of cardiac arrest and resuscitation

There is strong evidence to suggest that angiotensin-converting enzyme inhibitors (ACEIs) protect against local myocardial ischemia/reperfusion (I/R) injury. This study was designed to explore whether ACEIs exert cardioprotective effects in a swine model of cardiac arrest (CA) and resuscitation. Male pigs were randomly assigned to three groups: sham-operated group, saline treatment group and enalapril treatment group. Thirty minutes after drug infusion, the animals in the saline and enalapril groups were subjected to ventricular fibrillation (8 min) followed by cardiopulmonary resuscitation (up to 30 min). Cardiac function was monitored, and myocardial tissue and blood were collected for analysis. Enalapril pre-treatment did not improve cardiac function or the 6-h survival rate after CA and resuscitation; however, this intervention ameliorated myocardial ultrastructural damage, reduced the level of plasma cardiac troponin I and decreased myocardial apoptosis. Plasma angiotensin (Ang) II and Ang-(1–7) levels were enhanced in the model of CA and resuscitation. Enalapril reduced the plasma Ang II level at 4 and 6 h after the return of spontaneous circulation whereas enalapril did not affect the plasma Ang-(1–7) level. Enalapril pre-treatment decreased the myocardial mRNA and protein expression of angiotensin-converting enzyme (ACE). Enalapril treatment also reduced the myocardial ACE/ACE2 ratio, both at the mRNA and the protein level. Enalapril pre-treatment did not affect the upregulation of ACE2, Ang II type 1 receptor (AT1R) and MAS after CA and resuscitation. Taken together, these findings suggest that enalapril protects against ischemic injury through the attenuation of the ACE/Ang II/AT1R axis after CA and resuscitation in pigs. These results suggest the potential therapeutic value of ACEIs in patients with CA.

Association of Arterial Oxygen Tension During In-Hospital Cardiac Arrest With Return of Spontaneous Circulation and Survival

BACKGROUND

Despite numerous advances in the delivery of resuscitative care, in-hospital cardiac arrest (IHCA) continues to be associated with high morbidity and mortality. We sought to study the impact of arterial oxygen tension (Pao₂) on return of spontaneous circulation (ROSC) and survival to discharge in patients with IHCA.

METHODS

The study population included 255 consecutive patients who underwent advanced cardiac life support-guided resuscitation from January 2012 to December 2013 for IHCA at an academic tertiary medical center. Of these patients, 167 underwent arterial blood gas testing at the time of the arrest. Baseline demographic, clinical, laboratory, and clinical outcome data were recorded. The primary outcome of interest was survival to hospital discharge. Secondary outcome of interest was presence of ROSC.

RESULTS

Of the 167 patients studied, Pao₂ categorization included the following: Pao₂ < 60 mm Hg (n = 38), Pao₂ of 60-92 mm Hg (n = 44), Pao₂ of 93 to 159 mm Hg (n = 43), Pao₂ of 160 to 299 mm Hg (n = 24), and Pao₂ ≥ 300 mm Hg (n = 18). Patients with higher Pao₂ levels during the time of cardiac arrest were noted to have higher rates of hypertension and chronic kidney disease. Clinical presentation of IHCA, in particular, the initial rhythm, location of IHCA, and duration of cardiopulmonary resuscitation, was similar in all groups. Patients with higher Pao₂ levels had higher platelet count, higher arterial pH, and lower arterial carbon dioxide tension (Pco₂). With respect to outcomes, patients with higher intra-arrest Pao₂ levels had progressively higher rates of ROSC (58% vs 71% vs 72% vs 79% vs 100%, P = .021) and survival to discharge (16% vs 23% vs 30% vs 33% vs 56%, P = .031). In multivariate analysis, Pao₂ ≥ 300 mm Hg was independently associated with higher survival to discharge (odds ratio 60.68; 95% confidence interval: 3.04-1210.28; P = .007; referent Pao₂ < 60 mm Hg).

CONCLUSION

Higher intra-arrest Pao₂ is independently associated with higher rates of survival to discharge in adults with IHCA.

Hands-off Time during Automated Chest Compression Device Application in Out-of-Hospital Cardiac Arrest: A Case Series Report

INTRODUCTION

During out-of-hospital cardiac arrest (OHCA), chest compression interruptions or hands-off time (HOT) affect the prognosis. Our aim was to measure HOT due to the application of an automated chest compression device (ACD) by an advanced life support team.

MATERIALS AND METHODS

This was a prospective observational case series report since the introduction of a new method of installing the ACD. Inclusion criteria were patients over 18 years old with OHCA who were treated with an ACD (Lucas 2(TM), Physio-Control). The ACD application was indicated only for OHCA patients transported to a hospital for Extra Corporeal Life Support (ECLS). We recorded the HOT related to switching from manual to mechanical chest compressions. An ACD consists of dorsal and ventral components, which can be installed either in one or in two steps, separated from a chest compression sequence. HOT was expressed as a median number of seconds [interquartile range].

RESULTS

From January 1, 2012 to January 15, 2013, 30 patients were included. In the case of ACD application in one phase (n = 16), the median HOT was 25.3 s [19.8-30.5]. With regard to patients with an ACD application in two phases (n = 14), the median HOT was, respectively, 9.8 s [7.8-17] and 12.4 s [9.5-16.2], that is, a median global HOT of 23.6 s [19-27.6]. HOT was not different between ACD applications in one or two phases (p = 0.52). For a two phase application, the median chest compression time between the two manipulations was 14.2 s [6.4-18].

CONCLUSION

There was no significant difference between techniques in the application of the Lucas 2(TM) device in terms of HOT. The short time needed to apply the device lends itself well to use as a primary chest compression modality during cardiac arrest as well as a bridge to novel resuscitation strategies (ECLS). A further study is currently underway with a larger number of ECLS patients.

Effects of Shenfu injection on macrocirculation and microcirculation during cardiopulmonary resuscitation

AIM OF THE STUDY

To examine the effects of Shenfu injection (SFI) on macrocirculation and microcirculation during ventricular fibrillation (VF) and cardiopulmonary resuscitation (CPR).

MATERIALS AND METHODS

Sixteen female Landrace pigs were used in this study. After anesthesia, coronary perfusion pressure (CPP) was measured, and then the abdominal cavity was opened to observe the mesenteric microcirculation with the aid of sidestream dark field imaging. Following the guidelines, we determined microvascular flow index, perfused vessel density and proportion of perfused vessels both for large (diameter>20 μm) and small (diameter<20 μm) microvessels. SFI (1 ml/kg) or saline was given by vein injection at 1h before inducing VF. CPR was initiated after 4 min VF.

RESULTS

The shocks and duration of CPR were less in the SFI group compared with saline group. As the occurrence of VF, the CPP suddenly dropped to near zero, and cannot be measured in the both groups. However, there was greater CPP during CPR and at 1h after return of spontaneous circulation in the SFI group than saline group. Compared with saline, SFI significantly improved the microcirculation parameters of large and small microvessels during VF and CPR.

CONCLUSIONS

SFI can improve the microvascular blood flow and CPP during VF and CPR, and reduce the shocks and duration of CPR.

Sildenafil Protects against Myocardial Ischemia-Reperfusion Injury Following Cardiac Arrest in a Porcine Model: Possible Role of the Renin-Angiotensin System

Sildenafil, a phosphodiesterase-5 inhibitor sold as Viagra, is a cardioprotector against myocardial ischemia/reperfusion (I/R) injury. Our study explored whether sildenafil protects against I/R-induced damage in a porcine cardiac arrest and resuscitation (CAR) model via modulating the renin-angiotensin system. Male pigs were randomly divided to three groups: Sham group, Saline group, and sildenafil (0.5 mg/kg) group. Thirty min after drug infusion, ventricular fibrillation (8 min) and cardiopulmonary resuscitation (up to 30 min) was conducted in these animals. We found that sildenafil ameliorated the reduced cardiac function and improved the 24-h survival rate in this model. Sildenafil partly attenuated the increases of plasma angiotensin II (Ang II) and Ang (1–7) levels after CAR. Sildenafil also decreased apoptosis and Ang II expression in myocardium. The increases of expression of angiotensin-converting-enzyme (ACE), ACE2, Ang II type 1 receptor (AT1R), and the Ang (1–7) receptor Mas in myocardial tissue were enhanced after CAR. Sildenafil suppressed AT1R up-regulation, but had no effect on ACE, ACE2, and Mas expression. Sildenafilfurther boosted the upregulation of endothelial nitric oxide synthase (eNOS), cyclic guanosine monophosphate (cGMP) and inducible nitric oxide synthase(iNOS). Collectively, our results suggest that cardioprotection of sildenafil in CAR model is accompanied by an inhibition of Ang II-AT1R axis activation.

The effects of phosphodiesterase-5 inhibitor sildenafil against post-resuscitation myocardial and intestinal microcirculatory dysfunction by attenuating apoptosis and regulating microRNAs expression: essential role of nitric oxide syntheses signaling

Background

Recent experimental and clinical studies have indicated the cardioprotective role of sildenafil during ischemia/reperfusion (I/R) injury. Sildenafil has been shown to attenuate postresuscitation myocardial dysfunction in piget models of ventricular fibrillation. This study was designed to investigate if administration of sildenafil will attenuate post-resuscitation myocardial dysfunction by attenuating apoptosis and regulating miRNA expressions, furthermore, ameliorating the severity of post-microcirculatory dysfunction.

Methods

Twenty-four male pigs (weighing 30 ± 2 kg) were randomly divided into groups, sildenafil pretreatment (n = 8), saline (n = 8) and sham operation (sham, n = 8). Sildenafil pretreatment consisted of 0.5 mg/kg sildenafil, administered once intraperitoneally 30 min prior to ventricular fibrillation (VF). Eight minutes of untreated VF was followed by defibrillation in anesthetized, closed-chest pigs. Hemodynamic status and blood samples were obtained at 0 min, 0.5, 1, 2, 4 and 6 h after return of spontaneous circulation (ROSC). Surviving pigs were euthanatized at 24 h after ROSC, and hearts were removed for analysis by electron microscopy, western blotting, quantitative real-time polymerase chain reaction (PCR), and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. Intestinal microcirculatory blood flow was visualized by a sidestream dark-field imaging device at baseline and 0.5, 1, 2, 4, and 6 h after ROSC.

Results

Compared with the saline group, the sildenafil group had a higher 24-hour survival (7/8 versus 3/8 survivors, p < 0.05) and a better outcome in hemodynamic parameters. The protective effect of sildenafil also correlated with reduced cardiomyocyte apoptosis, as evidenced by reduced TUNEL-positive cells, increased anti-apoptotic Bcl-2/Bax ratio and inhibited caspase-3 activity in myocardium. Additionally, sildenafil treatment inhibited the increases in the microRNA-1 levels and alleviated the decreases in the microRNA-133a levels which negatively regulates pro-apoptotic genes. At 6 h after ROSC, post-resuscitation perfused vessel density and microcirculatory flow index were significantly lower in the saline group than in the sildenafil group.

Conclusions

The major findings of this study are as follows: (1) sildenafil improved post-resuscitation perfusion of the heart, and thus reduced cardiac myocyte apoptosis and improved cardiac function; (2) sildenafil treatment inhibited the increases in the microRNA-1 levels, but alleviated the decreases in the microRNA-133a levels.

The protective effects of a phosphodiesterase 5 inhibitor, sildenafil, on postresuscitation cardiac dysfunction of cardiac arrest: metabolic evidence from microdialysis

INTRODUCTION

Recent experimental and clinical studies have indicated the cardioprotective role of sildenafil during ischemia/reperfusion injury. The aim of this study was to determine, by obtaining metabolic evidence from microdialysis, if sildenafil could reduce the severity of postresuscitation myocardial dysfunction and lead to cardioprotection through beneficial effects on energy metabolism.

METHODS

Twenty-four male piglets were randomly divided into three groups: sildenafil (n = 8), saline (SA; n = 8) and sham operation (n = 8). Sildenafil pretreatment consisted of 0.5 mg/kg sildenafil administered once intraperitoneally 30 minutes prior to ventricular fibrillation (VF). The myocardial interstitial fluid (ISF) concentrations of glucose, lactate, pyruvate, glutamate and glycerol were determined by microdialysis before VF. Afterward, the piglets were subjected to 8 minutes of untreated VF followed by 15 minutes of open-chest cardiopulmonary resuscitation. ISF was collected continuously, and the experiment was terminated 24 hours after resuscitation.

RESULTS

After 8 minutes of untreated VF, the sildenafil group exhibited higher glucose and pyruvate concentrations of ISF and lower lactate and glutamate levels in comparison with the SA group, and these data reached statistical significance (P < 0.05). Advanced cardiac life support was delivered to both groups, with a 24-hour survival rate showing a promising trend in the sildenafil group (7 of 8 versus 3 of 8 survivors, P < 0.05). Compared with the SA group, the sildenafil group had a better outcome in terms of hemodynamic and oxygen metabolism parameters (P < 0.05). Myocardial tissue analysis revealed a dramatic increase in the contents of ATP, ADP and phosphocreatine in the sildenafil group versus the SA group at 24 hours after return of spontaneous circulation (ROSC; P = 0.03, P = 0.02 and P = 0.02, respectively). Furthermore, 24 hours after ROSC, the sildenafil group had marked elevations in activity of left ventricular Na(+)-K(+)-ATPase and Ca(2+)-ATPase compared with the SA group (P = 0.03, P = 0.04, respectively).

CONCLUSIONS

Sildenafil could reduce the severity of postresuscitation myocardial dysfunction, and it produced better clearance of metabolic waste in the ISF. This work might provide insights into the development of a novel strategy to treat postresuscitation myocardial dysfunction.

Effects of Chinese medicine shen-fu injection on the expression of inflammatory cytokines and complements during post-resuscitation immune dysfunction in a porcine model

OBJECTIVE

To investigate the action of Shen-Fu Injection (SFI) in regulating the expression of the serum complements and inflammatory cytokines synthesized and released in response to the stress of global ischemia accompanying cardiac arrest (CA) and resuscitation.

METHODS

Thirty pigs were randomly divided into the sham (n=6) and 3 returns of spontaneous circulation (ROSC) groups (n=24). After 8-min untreated ventricular fibrillation and 2-min basic life support, 24 pigs of the ROSC groups were randomized into three groups (n=8 per group), which received central venous injection of SFI (SFI group), epinephrine (EP group), or saline (SA group). Hemodynamic status and blood samples were obtained at 0, 0.5, 1, 2, 4, 6, 12, and 24 h after ROSC.

RESULTS

Serum concentrations of specific activation markers of the complement system C3, C4 and C5b-9 were increased during cardiopulmonary resuscitation through 24 h after ROSC. There were intense changes of various pro-inflammatory cytokines and anti-inflammatory cytokines as early as 0.5 h after CA. Compared with the EP and SA groups, SFI treatment reduced the proinflammatory cytokines levels of interleukin (IL)-6, IL-8 and tumor necrosis factor α (TNF-α, P<0.05), and increased the anti-inflammatory cytokine levels of IL-4 and IL-10 (P<0.05). Further, SFI treatment decreased the values of C3, C4 and C5b-9 compared with the EP and SA groups.

CONCLUSIONS

SFI, derived from the ancient Chinese medicine, has significant effects in attenuating post-resuscitation immune dysfunction by modulating the expression of complements and cytokines levels. The current study provided an experimental basis for the clinical application of a potential pharmacologic target for post resuscitation immune dysfunction.

Ventilation/perfusion ratios measured by multiple inert gas elimination during experimental cardiopulmonary resuscitation

BACKGROUND

During cardiopulmonary resuscitation (CPR) the ventilation/perfusion distribution (VA /Q) within the lung is difficult to assess. This experimental study examines the capability of multiple inert gas elimination (MIGET) to determine VA /Q under CPR conditions in a pig model.

METHODS

Twenty-one anaesthetised pigs were randomised to three fractions of inspired oxygen (1.0, 0.7 or 0.21). VA/ Q by micropore membrane inlet mass spectrometry-derived MIGET was determined at baseline and during CPR following induction of ventricular fibrillation. Haemodynamics, blood gases, ventilation distribution by electrical impedance tomography and return of spontaneous circulation were assessed. Intergroup differences were analysed by non-parametric testing.

RESULTS

MIGET measurements were feasible in all animals with an excellent correlation of measured and predicted arterial oxygen partial pressure (R(2)  = 0.96, n = 21 for baseline; R(2)  = 0.82, n = 21 for CPR). CPR induces a significant shift from normal VA /Q ratios to the high VA /Q range. Electrical impedance tomography indicates a dorsal to ventral shift of the ventilation distribution. Diverging pulmonary shunt fractions induced by the three inspired oxygen levels considerably increased during CPR and were traceable by MIGET, while 100% oxygen most negatively influenced the VA /Q. Return of spontaneous circulation were achieved in 52% of the animals.

CONCLUSIONS

VA /Q assessment by MIGET is feasible during CPR and provides a novel tool for experimental purposes. Changes in VA /Q caused by different oxygen fractions are traceable during CPR. Beyond pulmonary perfusion deficits, these data imply an influence of the inspired oxygen level on VA /Q. Higher oxygen levels significantly increase shunt fractions and impair the normal VA /Q ratio.

Combination of epinephrine with esmolol attenuates post-resuscitation myocardial dysfunction in a porcine model of cardiac arrest

Background

Recent experimental and clinical studies have indicated that the β-adrenergic effect of epinephrine significantly increases the severity of post resuscitation myocardial dysfunction. The aim of the study was to investigate whether the short-acting β₁-selective adrenergic blocking agent, esmolol, would attenuate post resuscitation myocardial dysfunction in a porcine model of cardiac arrest.

Methods and Results

After 8 min of untreated ventricular fibrillation and 2 min of basic life support, 24 pigs were randomized to three groups (n = 8 per group), which received central venous injection of either epinephrine combined with esmolol (EE group), epinephrine (EP group), or saline (SA group). Hemodynamic status and blood samples were obtained at 0, 30, 60, 120, 240 and 360 min after return of spontaneous circulation (ROSC). Surviving pigs were euthanatized at 24 h after ROSC, and the hearts were removed for analysis by electron microscopy, Western blotting, quantitative real-time polymerase chain reaction, and terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling (TUNEL) assay. Compared with the EP and SA groups, EE group had a better outcome in hemodynamic function, (improved dp/dt maxima and minima and cardiac output) (P<0.05), and improved oxygen metabolism (oxygen delivery and oxygen consumption) (P<0.05), which suggesting that EE can protect myocardial tissue from injury and improve post-resuscitation myocardial dysfunction. The protective effect of EE also correlated with reducing cardiomyocyte apoptosis, evidenced by reducing TUNEL-positive cells, increasing anti-apoptotic Bcl-2/Bax ratio and suppression of caspase-3 activity in myocardium.

Conclusions

Esmolol, a short-acting β₁-selective adrenergic blocking agent, given during CPR has significant effects on attenuating post resuscitation myocardial dysfunction. The current study provides a potential pharmacologic target for post resuscitation myocardial dysfunction.

Even four minutes of poor quality of CPR compromises outcome in a porcine model of prolonged cardiac arrest

Objective. Untrained bystanders usually delivered suboptimal chest compression to victims who suffered from cardiac arrest in out-of-hospital settings. We therefore investigated the hemodynamics and resuscitation outcome of initial suboptimal quality of chest compressions compared to the optimal ones in a porcine model of cardiac arrest. Methods. Fourteen Yorkshire pigs weighted 30 ± 2 kg were randomized into good and poor cardiopulmonary resuscitation (CPR) groups. Ventricular fibrillation was electrically induced and untreated for 6 mins. In good CPR group, animals received high quality manual chest compressions according to the Guidelines (25% of animal's anterior-posterior thoracic diameter) during first two minutes of CPR compared with poor (70% of the optimal depth) compressions. After that, a 120-J biphasic shock was delivered. If the animal did not acquire return of spontaneous circulation, another 2 mins of CPR and shock followed. Four minutes later, both groups received optimal CPR until total 10 mins of CPR has been finished. Results. All seven animals in good CPR group were resuscitated compared with only two in poor CPR group (P < 0.05). The delayed optimal compressions which followed 4 mins of suboptimal compressions failed to increase the lower coronary perfusion pressure of five non-survival animals in poor CPR group. Conclusions. In a porcine model of prolonged cardiac arrest, even four minutes of initial poor quality of CPR compromises the hemodynamics and survival outcome.

Effect of continuous compression and 30:2 cardiopulmonary resuscitation on cerebral microcirculation in a porcine model of cardiac arrest

BACKGROUND

The effect of rescue breathing on neurologic prognosis after cardiopulmonary resuscitation (CPR) is controversial. Therefore, we investigated the cerebral microcirculatory and oxygen metabolism during continuous compression (CC) and 30:2 CPR (VC) in a porcine model of cardiac arrest to determine which is better for neurologic prognosis after CPR.

METHODS

After 4 min of ventricular fibrillation, 20 pigs were randomised into two groups (n=10/group) receiving CC-CPR or VC-CPR. Cerebral oxygen metabolism and blood flow were measured continuously using laser Doppler flowmetry. Haemodynamic data were recorded at baseline and 5 min, 30 min, 2 h and 4 h after restoration of spontaneous circulation (ROSC).

RESULTS

Compared with the VC group, the mean cortical cerebral blood flow was significantly higher at 5 min ROSC in the CC group (P<0.05), but the difference disappeared after that time point. Brain percutaneous oxygen partial pressures were higher, and brain percutaneous carbon dioxide partial pressures were lower, in the VC group from 30 min to 4 h after ROSC; significant differences were found between the two groups (P<0.05). However, no significant difference of the cerebral oxygen extraction fraction existed between the two groups.

CONCLUSIONS

Inconsistency of systemic circulation and cerebral microcirculation with regard to blood perfusion and oxygen metabolism is common after CPR. No significant differences in cortical blood flow and oxygen metabolism were found between the CC-CPR and VC-CPR groups after ROSC.

Effect of mild hypothermia on the coagulation-fibrinolysis system and physiological anticoagulants after cardiopulmonary resuscitation in a porcine model

The aim of this study was to evaluate the effect of mild hypothermia on the coagulation-fibrinolysis system and physiological anticoagulants after cardiopulmonary resuscitation (CPR). A total of 20 male Wuzhishan miniature pigs underwent 8 min of untreated ventricular fibrillation and CPR. Of these, 16 were successfully resuscitated and were randomized into the mild hypothermia group (MH, n = 8) or the control normothermia group (CN, n = 8). Mild hypothermia (33°C) was induced intravascularly, and this temperature was maintained for 12 h before pigs were actively rewarmed. The CN group received normothermic post-cardiac arrest (CA) care for 72 h. Four animals were in the sham operation group (SO). Blood samples were taken at baseline, and 0.5, 6, 12, 24, and 72 h after ROSC. Whole-body mild hypothermia impaired blood coagulation during cooling, but attenuated blood coagulation impairment at 72 h after ROSC. Mild hypothermia also increased serum levels of physiological anticoagulants, such as PRO C and AT-III during cooling and after rewarming, decreased EPCR and TFPI levels during cooling but not after rewarming, and inhibited fibrinolysis and platelet activation during cooling and after rewarming. Finally, mild hypothermia did not affect coagulation-fibrinolysis, physiological anticoagulants, or platelet activation during rewarming. Thus, our findings indicate that mild hypothermia exerted an anticoagulant effect during cooling, which may have inhibitory effects on microthrombus formation. Furthermore, mild hypothermia inhibited fibrinolysis and platelet activation during cooling and attenuated blood coagulation impairment after rewarming. Slow rewarming had no obvious adverse effects on blood coagulation.

Hypothermia-induced neuroprotection is associated with reduced mitochondrial membrane permeability in a swine model of cardiac arrest

Increasing evidence has shown that mild hypothermia is neuroprotective for comatose patients resuscitated from cardiac arrest, but the mechanism of this protection is not fully understood. The aim of this study was to determine whether prolonged whole-body mild hypothermia inhibits mitochondrial membrane permeability (MMP) in the cerebral cortex after return of spontaneous circulation (ROSC). Thirty-seven inbred Chinese Wuzhishan minipigs were successfully resuscitated after 8 minutes of untreated ventricular fibrillation (VF) and underwent recovery under normothermic (NT) or prolonged whole-body mild hypothermic (HT; 33°C) conditions for 24 or 72 hours. Cerebral samples from the frontal cortex were collected at 24 and 72 hours after ROSC. Mitochondria were isolated by differential centrifugation. At 24 hours, relative to NT, HT was associated with reductions in opening of the mitochondrial permeability transition pore, release of pro-apoptotic substances from mitochondria, caspase 3 cleavage, apoptosis, and neurologic deficit scores, as well as increases in mitochondrial membrane potential and mitochondrial respiration. Together, these findings suggest that mild hypothermia inhibits ischemia-induced increases in MMP, which may provide neuroprotection against cerebral injury after cardiac arrest.

Effect of rescue breathing during cardiopulmonary resuscitation on lung function after restoration of spontaneous circulation in a porcine model of prolonged cardiac arrest

OBJECTIVE

The destruction of the pulmonary structure after cardiopulmonary resuscitation may lead to lung function breakdown. The aim of this study was to investigate lung function after cardiopulmonary resuscitation and the influence of rescue breathing on lung function.

DESIGN

Prospective, randomized animal study.

SETTING

A university animal research laboratory.

SUBJECTS

Twenty-eight male domestic pigs weighing 30 ± 2 kg.

INTERVENTIONS

The animals were randomized into three groups: continuous compressions (n = 12), 30:2 compression/rescue ventilation cardiopulmonary resuscitation (n = 12), and sham cardiopulmonary resuscitation (n = 4). Ventricular fibrillation was induced in the continuous compressions and compression/rescue ventilation groups.

MEASUREMENTS AND MAIN RESULTS

Cardiac output, extravascular lung water, and airway resistance were measured at baseline and 1, 2, and 4 hrs after restoration of spontaneous circulation. Thoracopulmonary compliance, lower inflection point, and dead space were calculated. Lung ventilation/perfusion scans with Tc were performed 48 hrs before the experiment and 24 hrs after restoration of spontaneous circulation. Conventional histopathology evaluation was performed. Dead space, airway resistance, lower inflection point, and extravascular lung water significantly increased and compliance decreased after restoration of spontaneous circulation in the continuous compressions and compression/rescue ventilation groups. Lung injury was more severe in the continuous compressions group. Significant differences were found between the two groups in the three time points after restoration of spontaneous circulation (p < 0.05). Variables of the sham cardiopulmonary resuscitation group remained stable during the whole protocol. Poor ventilation/perfusion and mismatch were found after restoration of spontaneous circulation, but the injury was mitigated in the compression/rescue ventilation group. Histopathology injury in the compression/rescue ventilation group was also improved.

CONCLUSIONS

Appropriate rescue breathing during cardiopulmonary resuscitation does not influence the prognosis of cardiac arrest or the hemodynamics after restoration of spontaneous circulation but can improve lung function and alleviate lung injury.

Shen-fu injection reduces postresuscitation myocardial dysfunction in a porcine model of cardiac arrest by modulating apoptosis

Shen-Fu injection (SFI) following cardiac arrest exhibits cardioprotective effects, but its effect on myocardial dysfunction, a critical issue following resuscitation, is unclear. This study sought to examine whether SFI reduces postresuscitation myocardial dysfunction in a porcine model of cardiac arrest by modulating apoptosis. After 8 min of untreated ventricular fibrillation and 2 min of basic life support, 24 pigs were randomized divided into three groups, which received central venous injection of either Shen-Fu (SFI group; 1.0 mL/kg), epinephrine (EP group; 0.02 mg/kg), or saline (SA group). After successful return of spontaneous circulation (ROSC), hemodynamic status and blood samples were obtained at 0, 30, 120, and 360 min after ROSC. Surviving pigs were killed at 24 h after ROSC, and the hearts were removed for analysis by electron microscopy, Western blotting, quantitative real-time polymerase chain reaction, and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) assay. Compared with the EP and SA groups, animals treated with SFI had improved left ventricular function (P < 0.05), lower troponin T levels (P < 0.01), and increased tissue perfusion and oxygen metabolism (P < 0.05). Shen-Fu injection was associated with a reduction in (i) Bcl-2, Bax, and caspase 3 protein expression (P < 0.05); (ii) caspase 3 mRNA upregulation; and (iii) apoptosis, compared with the EP and SA groups. Caspase 3-mediated apoptosis occurs following myocardial injury after cardiopulmonary resuscitation in pigs. Shen-Fu injection decreased myocardial injury; improved myocardial ultrastructure; inhibited Bcl-2, Bax, and caspase 3 expression; and reduced myocardial apoptosis. Therefore, SFI could significantly attenuate postresuscitation myocardial dysfunction by modulating apoptosis.

Load-distributing band improves ventilation and hemodynamics during resuscitation in a porcine model of prolonged cardiac arrest

Background

The use of mechanical cardiopulmonary resuscitation (CPR) has great potential for the clinical setting. The purpose of present study is to compare the hemodynamics and ventilation during and after the load-distributing band CPR, versus the manual CPR in a porcine model of prolonged cardiac arrest, and to investigate the influence of rescue breathing in different CPR protocols.

Methods

Sixty-four male pigs (n = 16/group), weighing 30 ± 2 kg, were induced ventricular fibrillation and randomized into four resuscitation groups: continuous load-distributing band CPR without rescue ventilation (C-CPR), load-distributing band 30:2 CPR (A-CPR), load-distributing band CPR with continuous rescue breathing (10/min) (V-CPR) or manual 30:2 CPR (M-CPR). Respiratory variables and hemodynamics were recorded continuously; blood gas was analyzed.

Results

Tidal volume produced by compressions in the A-, C- and V-CPR groups were significantly higher compared with the M-CPR group (all p < 0.05). Coronary perfusion pressure of the V-CPR group was significantly lower than the C-CPR group (p < 0.01), but higher than the M-CPR group. The increasing of lung dead space after restoration of spontaneous circulation was significantly greater in the M-CPR group compared with the A-, C- and V-CPR groups (p < 0.01). Blood pH gradually decreased and was lower in the M-CPR group than that in the A-, C- and V-CPR groups (p < 0.01). PaO₂ of the A-, C- and V-CPR groups were significantly higher and PaCO₂ were significantly lower compared with the M-CPR (both p < 0.05). Cerebral performance categories were better in the A-, C- and V-CPR groups compared with the M-CPR group (p < 0.0001).

Conclusions

The load-distributing band CPR significantly improved respiratory parameters during resuscitation by augmenting passive ventilation, and significantly improved coronary perfusion pressure. The volume of ventilation produced by the load-distributing band CPR was adequate to maintain sufficient gas exchange independent of rescue breathing.

Comparison of times of intervention during pediatric CPR maneuvers using ABC and CAB sequences: a randomized trial

BACKGROUND

The proposed introduction of the CAB (circulation, airway, breathing) sequence for cardiopulmonary resuscitation has raised some perplexity within the pediatric community. We designed a randomized trial intended to verify if and how much timing of intervention in pediatric cardiopulmonary resuscitation is affected by the use of the CAB vs. the ABC (airway, breathing, circulation) sequence.

PATIENTS AND METHODS

340 volunteers, paired into 170 two-person teams, performed 2-rescuer healthcare provider BLS with both a CAB and ABC sequence. Their performances were audio-video recorded and times of intervention in the two scenarios, cardiac and respiratory arrest, were monitored.

RESULTS

The CAB sequence compared to ABC prompts quicker recognition of respiratory (CAB vs. ABC=17.48 ± 2.19 vs. 19.17 ± 2.38s; p<0.05) or cardiac arrest (CAB vs. ABC=17.48 ± 2.19 vs. 41.67 ± 4.95; p<0.05) and faster start of ventilatory maneuvers (CAB vs. ABC=19.13 ± 1.47s vs. 22.66 ± 3.07; p<0.05) or chest compressions (CAB vs. ABC=19.27 ± 2.64 vs. 43.40 ± 5.036; p<0.05).

CONCLUSIONS

Compared to ABC the CAB sequence prompts shorter time of intervention both in diagnosing respiratory or cardiac arrest and in starting ventilation or chest compression. However, this does not necessarily entail prompter resumption of spontaneous circulation and significant reduction of neurological sequelae, an issue that requires further studies.

Mild hypothermia attenuates mitochondrial oxidative stress by protecting respiratory enzymes and upregulating MnSOD in a pig model of cardiac arrest

Mild hypothermia is the only effective treatment confirmed clinically to improve neurological outcomes for comatose patients with cardiac arrest. However, the underlying mechanism is not fully elucidated. In this study, our aim was to determine the effect of mild hypothermia on mitochondrial oxidative stress in the cerebral cortex. We intravascularly induced mild hypothermia (33°C), maintained this temperature for 12 h, and actively rewarmed in the inbred Chinese Wuzhishan minipigs successfully resuscitated after 8 min of untreated ventricular fibrillation. Cerebral samples were collected at 24 and 72 h following return of spontaneous circulation (ROSC). We found that mitochondrial malondialdehyde and protein carbonyl levels were significantly increased in the cerebral cortex in normothermic pigs even at 24 h after ROSC, whereas mild hypothermia attenuated this increase. Moreover, mild hypothermia attenuated the decrease in Complex I and Complex III (i.e., major sites of reactive oxygen species production) activities of the mitochondrial respiratory chain and increased antioxidant enzyme manganese superoxide dismutase (MnSOD) activity. This increase in MnSOD activity was consistent with the upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) mRNA and protein expressions, and with the increase of Nrf2 nuclear translocation in normothermic pigs at 24 and 72 h following ROSC, whereas mild hypothermia enhanced these tendencies. Thus, our findings indicate that mild hypothermia attenuates mitochondrial oxidative stress in the cerebral cortex, which may be associated with reduced impairment of mitochondrial respiratory chain enzymes, and enhancement of MnSOD activity and expression via Nrf2 activation.

Neonatal resuscitation science, education, and practice: the role of the Neonatal Resuscitation Program

For almost 25 years, the Neonatal Resuscitation Program of the American Academy of Pediatrics has provided educational tools that are used in the United States and throughout the world to teach neonatal resuscitation. Over that time period, the guidelines for resuscitation have been increasingly evidence-based and a formal system has been established to determine which steps should be updated on the basis of available information. The most recent update occurred in 2010. This article describes the evidence review process and the specific evidence that lead to a number of significant changes in practice that were included in the 2010 guidelines.