Blood flow and perfusion pressure during open-chest versus closed-chest cardiopulmonary resuscitation in pigs

Intraventricular pressure and volume during conventional and automated head-up CPR

BACKGROUND

Active compression-decompression (ACD) CPR, an impedance threshold device (ITD) and automated head and thorax elevation, collectively termed AHUP-CPR, increases cerebral and coronary perfusion pressures, brain blood flow, end-tidal CO2 (ETCO2) and cerebral oximetry (rSO2) in animal models compared with conventional (C) CPR. We tested the hypothesis that cardiac stroke volume (SV) is higher with AHUP-CPR versus C-CPR or ACD + ITD in a porcine cardiac arrest model.

METHODS

Farm pigs (n = 14) were sedated, anesthetized, and ventilated. Hemodynamics, including biventricular pressure-volume loops, were continuously measured. Following 10 min of untreated ventricular fibrillation, C-CPR was performed for 2 min, then ACD + ITD for 2 min in the flat position, and then AHUP-CPR thereafter. Linear mixed-effects model and Pearson correlation comparisons were used for statistical analysis.

RESULTS

Coronary and cerebral perfusion pressures, ETCO2, rSO2, and right (RV) and left (LV) ventricular SV increased progressively and significantly with the implementation of AHUP-CPR (p < 0.05). RV SV with C-CPR was 24.8 ± 2.8 mL (∼48% of baseline) versus 45.2 ± 4.1 with AHUP-CPR (∼90% of baseline) (p < 0.01). LV SV with C-CPR was 17.6 ± 1.8 mL (∼35% of baseline) versus 38.7 ± 6.7 with AHUP-CPR (∼80% of baseline) (p < 0.01).

CONCLUSION

A fundamental and inherent shortcoming of C-CPR, limited cardiac stroke volume, and resultant forward flow, can be overcome with AHUP-CPR. These findings may help explain the better outcomes associated with early use of AHUP-CPR.

Active decompression during automated head-up cardiopulmonary resuscitation

BACKGROUND

The combination of active compression-decompression cardiopulmonary resuscitation (ACD-CPR) with an impedance threshold device (ITD) and controlled head-up positioning (AHUP-CPR) is associated with improved outcomes compared with conventional CPR (C-CPR). This study focused on the role of active decompression (AD) during AHUP-CPR.

METHODS

Farm pigs (n = 10, ∼40 kg) were anesthetized, intubated and ventilated. Physiological parameters and right ventricular pressure-volume loops were recorded continuously. Ventricular fibrillation was induced and left untreated for 10 mins, followed by automated C-CPR (2 min), ACD + ITD CPR in the flat position (2 min), and then AHUP-CPR with 3 cm of lift above the neutral chest position. After 15 min of CPR, AD was discontinued and then restarted incrementally to 4 cm. Data were analyzed with a linear mixed-effects model, using random intercepts for individual pigs.

RESULTS

Upon cessation of AD during AHUP-CPR, decompression right atrial pressure (+59%) increased (p < 0.01), whereas multiple hemodynamic parameters positively associated with perfusion, including coronary (-25%) and cerebral perfusion pressures (-11%), end-tidal CO2 (-13%), stroke volume and cardiac output (-26%), decreased immediately and significantly with p < 0.05. Restoration of AD reduced right atrial pressure and increased positive perfusion parameters in an incremental manner. Only with ≥ 3 cm of AD were all hemodynamic parameters restored to ≥ 90% of pre-AD discontinuation levels.

CONCLUSION

Full chest wall lift, achieved with ≥ 3 cm of AD, was needed to maintain and optimize hemodynamics during AHUP-CPR in pigs. These findings should be considered when optimizing care with this new approach.

The role of emergency department thoracotomy in patients with cranial gunshot wounds

BACKGROUND

Although several society guidelines exist regarding emergency department thoracotomy (EDT), there is a lack of data upon which to base guidance for multiple gunshot wound (GSW) patients whose injuries include a cranial GSW. We hypothesized that survival in these patients would be exceedingly low.

METHODS

We used Pennsylvania Trauma Outcomes Study data, 2002 to 2021, and included EDTs for GSWs. We defined EDT by International Classification of Diseases codes for thoracotomy or procedures requiring one, with a location flagged as emergency department. We defined head injuries as any head Abbreviated Injury Scale (AIS) score of ≥1 and severe head injuries as head AIS score of ≥4. Head injuries were "isolated" if all other body regions have an AIS score of <2. Descriptive statistics were performed. Discharge functional status was measured in five domains.

RESULTS

Over 20 years in Pennsylvania, 3,546 EDTs were performed; 2,771 (78.1%) were for penetrating injuries. Most penetrating EDTs (2,003 [72.3%]) had suffered GSWs. Survival among patients with isolated head wounds (n = 25) was 0%. Survival was 5.3% for the non-head injured (n = 94 of 1,787). In patients with combined head and other injuries, survival was driven by the severity of the head wound-0% (0 of 81) with a severe head injury ( p = 0.035 vs. no severe head injury) and 4.5% (5 of 110) with a nonsevere head injury. Of the five head-injured survivors, two were fully dependent for transfer mobility, and three were partially or fully dependent for locomotion. Of 211 patients with a cranial injury who expired, 2 (0.9%) went on to organ donation.

CONCLUSION

Although there is clearly no role for EDT in patients with isolated head GSWs, EDT may be considered in patients with combined injuries, as most of these patients have minor head injuries and survival is not different from the non-head injured. However, if a severe head injury is clinically apparent, even in the presence of other body cavity injuries, EDT should not be pursued.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level IV.

Cardiac arrest in the perioperative period: a consensus guideline for identification, treatment, and prevention from the European Society of Anaesthesiology and Intensive Care and the European Society for Trauma and Emergency Surgery

INTRODUCTION

Cardiac arrest in the operating room is a rare but potentially life-threatening event with mortality rates of more than 50%. Contributing factors are often known, and the event is recognised rapidly as patients are usually under full monitoring. This guideline covers the perioperative period and is complementary to the European Resuscitation Council guidelines.

MATERIAL AND METHODS

The European Society of Anaesthesiology and Intensive Care and the European Society for Trauma and Emergency Surgery jointly nominated a panel of experts to develop guidelines for the recognition, treatment, and prevention of cardiac arrest in the perioperative period. A literature search was conducted in MEDLINE, EMBASE, CINAHL and the Cochrane Central Register of Controlled Trials. All searches were restricted to publications from 1980 to 2019 inclusive and to the English, French, Italian and Spanish languages. The authors also contributed individual, independent literature searches.

RESULTS

This guideline contains background information and recommendation for the treatment of cardiac arrest in the operating room environment, and addresses controversial topics such as open chest cardiac massage, resuscitative endovascular balloon occlusion and resuscitative thoracotomy, pericardiocentesis, needle decompression, and thoracostomy.

CONCLUSIONS

Successful prevention and management of cardiac arrest during anaesthesia and surgery requires anticipation, early recognition, and a clear treatment plan. The ready availability of expert staff and equipment must also be taken into consideration. Success not only depends on medical knowledge, technical skills and a well-organised team using crew resource management, but also on an institutional safety culture embedded in everyday practice through continuous education, training, and multidisciplinary co-operation.

Cardiac arrest in the perioperative period: a consensus guideline for identification, treatment, and prevention from the European Society of Anaesthesiology and Intensive Care and the European Society for Trauma and Emergency Surgery

INTRODUCTION

Cardiac arrest in the operating room is a rare but potentially life-threatening event with mortality rates of more than 50%. Contributing factors are often known, and the event is recognised rapidly as patients are usually under full monitoring. This guideline covers the perioperative period and is complementary to the European Resuscitation Council (ERC) guidelines.

MATERIAL AND METHODS

The European Society of Anaesthesiology and Intensive Care and the European Society for Trauma and Emergency Surgery jointly nominated a panel of experts to develop guidelines for the recognition, treatment and prevention of cardiac arrest in the perioperative period. A literature search was conducted in MEDLINE, EMBASE, CINAHL and the Cochrane Central Register of Controlled Trials. All searches were restricted to publications from 1980 to 2019 inclusive and to the English, French, Italian and Spanish languages. The authors also contributed individual, independent literature searches.

RESULTS

This guideline contains background information and recommendation for the treatment of cardiac arrest in the operating room environment, and addresses controversial topics such as open chest cardiac massage (OCCM), resuscitative endovascular balloon occlusion (REBOA) and resuscitative thoracotomy, pericardiocentesis, needle decompression and thoracostomy.

CONCLUSION

Successful prevention and management of cardiac arrest during anaesthesia and surgery requires anticipation, early recognition and a clear treatment plan. The ready availability of expert staff and equipment must also be taken into consideration. Success not only depends on medical knowledge, technical skills and a well organised team using crew resource management but also on an institutional safety culture embedded in everyday practice through continuous education, training and multidisciplinary co-operation.

Open chest selective aortic arch perfusion vs open cardiac massage as a means of perfusion during in exsanguination cardiac arrest: a comparison of coronary hemodynamics in swine

AIM

To describe and compare the aortic-right atrial pressure (AoP-RAP) gradients and mean coronary perfusion pressures (CPPs) generated during open chest selective aortic arch perfusion (OCSAAP) with those generated during open cardiac massage (OCM) in hypovolemic swine.

METHODS

Ten male Hanford swine utilized in a prior poly-trauma study were included in the study. Animals were rendered hypovolemic via a 30% volume bleed. Upon confirmation of death, animals underwent immediate clamshell thoracotomy and aortic cross-clamping followed by 5 min of OCM. A catheter suitable for OCSAAP was then inserted into the aorta and animals underwent 1 min of OCSAAP at a rate of 10 mL/kg/min. Aortic and right atrial pressures were recorded continuously using solid-state blood pressure catheters. Representative 10-s intervals from each resuscitation method were extracted. Hemodynamic parameters including AoP-RAP gradients and CPPs were calculated and compared.

RESULTS

At baseline, time from death to intervention was significantly shorter for OCM. However, mean CPPs and AoP-RAP gradients were significantly higher in animals undergoing OCSAAP. 98% of OCSAAP segments had a mean CPP > 15, compared to 35% of OCM intervals. While OCM had a significant negative correlation between time to intervention and maximum CPP, this correlation was not significant for OCSAAP.

CONCLUSION

OCSAAP generates favorable and potentially time-resistant pressure gradients when compared to those generated by OCM. Further investigation of the technique of OCSAAP is warranted, as it may have potential utility as a therapy during resuscitative thoracotomy (RT).

Resuscitative Endovascular Balloon Occlusion of the Aorta Improves Cardiac Compression Fraction Versus Resuscitative Thoracotomy in Patients in Traumatic Arrest

STUDY OBJECTIVE

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is emerging as an alternative to resuscitative thoracotomy for proximal aortic control in select patients with exsanguinating hemorrhage below the diaphragm. The purpose of this study is to compare interruptions in closed chest compression or open chest cardiac massage during REBOA versus resuscitative thoracotomy.

METHODS

From May 2014 to December 2016, patients in arrest who received aortic occlusion with REBOA or resuscitative thoracotomy were included. Total cardiac compression time was defined as the total time that closed chest compression was performed for REBOA patients and the total time that closed chest compression (before resuscitative thoracotomy) and open chest cardiac massage (after thoracotomy) were performed for resuscitative thoracotomy patients. Cardiac compression fraction was defined as the time compressions occurred during the entire resuscitation phase. All resuscitations were captured by multiview, time-stamped videography.

RESULTS

Fifty patients with aortic occlusion after arrest were enrolled: 22 REBOA and 28 resuscitative thoracotomy. Most were men (86%) (median age 30.2 years, interquartile range [IQR] 24.9 to 42.3; median Injury Severity Score 27, IQR 16 to 42; neither differed between groups). The median duration of total cardiac compression time was 945 seconds (IQR 697 to 1,357) for REBOA versus 496 seconds (IQR 375 to 933) for resuscitative thoracotomy. During initial resuscitation, compressions occurred 86.5% of the time (SD 9.7%) during resuscitation with REBOA versus 35.7% of the time (SD 16.4%) in patients receiving resuscitative thoracotomy. Cardiac compression fraction improved after open cross clamp in resuscitative thoracotomy patients to 73.2% of the time (SD 18.0%) but remained significantly less than the same period for REBOA (86.7%; SD 9.4%). Mean cardiac compression fraction for REBOA was significantly improved over that for resuscitative thoracotomy (86.2% [SD 9.1%] versus 55.3 [SD 17.1%]; mean difference 31.0%; 95% confidence interval for difference 22.7% to 39.23%; P<.001). Median pause in resuscitation related to procedural tasks was 0 seconds (IQR 0 to 13) for REBOA and 148 seconds (IQR 118 to 223) in resuscitative thoracotomy.

CONCLUSION

Total duration of interruptions of cardiac compressions is shorter for patients receiving REBOA versus resuscitative thoracotomy before and during resuscitation with aortic occlusion. Markers for perfusion during resuscitation must be examined to understand the effects of cardiac compressions and aortic occlusion on patients in arrest because of hemorrhagic shock.

Preconditioning but not postconditioning treatment with resveratrol substantially ameliorates post‑resuscitation myocardial dysfunction through the PI3K/Akt signaling pathway

Post-resuscitation myocardial dysfunction (PRMD) is a severe complication that arises in patients after cardiac arrest (CA). However, there are no safe or effective treatment strategies that are currently available to treat these patients. In the present study, it was investigated whether resveratrol administration could inhibit myocardial nitrative stress to alleviate PRMD. CA was induced in Sprague-Dawley rats by trans-oesophageal alternating electrical stimulation, followed by cardiopulmonary resuscitation. Rats were then randomly divided into a preconditioning or a postconditioning group. Left ventricular function (+dP/dt_max and -dP/dt_min) was recorded for 4 h after the return of spontaneous circulation (ROSC), after which the animals were euthanized. Myocardial nitrative stress was analysed using enzyme-linked immunosorbent assay, western blotting and immunohistochemistry. Wortmannin (a PI3K inhibitor) was used to investigate the involvement of the PI3k/Akt signalling pathway in the cardio-protective activity of resveratrol. After ROSC, resveratrol improved PRMD compared to the vehicle control; however, resveratrol administration significantly improved PRMD in the preconditioning group compared to the postconditioning group. Likewise, resveratrol preconditioning significantly decreased the expression of iNOS and nitrotyrosine in rat hearts but did not significantly ameliorate myocardial nitrative stress. Wortmannin partially inhibited the protective effect of resveratrol preconditioning and resulted in the deterioration of cardiac function and increase in iNOS and nitrotyrosine levels. Resveratrol preconditioning could alleviate PRMD by inhibiting myocardial nitrative stress. The PI3K/Akt signalling pathway may be partially involved in the process.

Open chest cardiac massage offers no benefit over closed chest compressions in patients with traumatic cardiac arrest

BACKGROUND

Open chest cardiac massage (OCCM) is a commonly performed procedure after traumatic cardiac arrest (TCA). OCCM has been reported to be superior to closed chest compressions (CCC) in animal models and in non-TCA. The purpose of this study is to prospectively compare OCCM versus CCC in TCA using end-tidal carbon dioxide (ETCO2), the criterion standard for determining the effectiveness of chest compressions and detection of return of spontaneous circulation (ROSC), as the surrogate for cardiac output and marker for adequacy of resuscitation.

METHODS

This prospective observational study enrolled patients over a 9-month period directly presenting to a level 1 trauma center after TCA. Continuous high-resolution ETCO2 measurements were collected every 6 seconds for periods of CCC and OCCM, respectively. Patients receiving CCC only were compared with patients receiving CCC followed by OCCM. Student's t tests were used to compare ETCO2 within and between groups.

RESULTS

Thirty-three patients were enrolled (16 OCCM, 17 CCC-only). Mean time of CCC before OCCM was 66 seconds. Within the OCCM group, final, peak, mean, and median ETCO2 levels significantly increased when comparing the initial CCC period to the OCCM interval. Using a time-matched comparison, significant increases were observed in the final and peak but not mean and median values when comparing the first minute of CCC to the remaining time in the CCC-only group. However, when periods of OCCM were compared with equivalent periods of CCC-only, there were no differences in the initial, final, peak, mean, or median ETCO2 values. Correspondingly, no difference in rates of ROSC was observed between groups (OCCM 23.5% vs. CCC 38.9%; p = 0.53).

CONCLUSION

Although we could not control for confounders, we found no significant improvement in ETCO2 or ROSC with OCCM. With newer endovascular techniques for aortic occlusion, thoracotomy solely for performing OCCM provides no benefit over CCC.

LEVEL OF EVIDENCE

Therapeutic study, level III.

Echocardiography for patients undergoing extracorporeal cardiopulmonary resuscitation: a primer for intensive care physicians

Echocardiography is an invaluable tool in the management of patients with extracorporeal cardiopulmonary resuscitation (ECPR) and subsequent extracorporeal membrane oxygenation (ECMO) support and weaning. At the very beginning, echocardiography can identify the etiology of cardiac arrest, such as massive pulmonary embolism and cardiac tamponade. Eliminating these culprits saves life and may avoid the initiation of extracorporeal cardiopulmonary resuscitation. If the underlying causes are not identified or intrinsic to the heart (e.g., such as those caused by cardiomyopathy and myocarditis), conventional cardiopulmonary resuscitation (CCPR) will continue to maintain cardiac output. The quality of CCPR can be monitored, and if cardiac output cannot be maintained, early institution of extracorporeal cardiopulmonary resuscitation may be reasonable. Cannulation is sometimes challenging for extracorporeal cardiopulmonary resuscitation patients. Fortunately, with the help of ultrasonography procedures including localization of vessels, selecting a cannula of appropriate size and confirmation of catheter tip may become easy under sophisticated hand. Monitoring of cardiac function and complications during extracorporeal membrane oxygenation support can be done with echocardiography. However, the cardiac parameters should be interpreted with understanding of hemodynamic configuration of extracorporeal membrane oxygenation. Thrombus and blood stasis can be identified with ultrasound, which may prompt mechanical and pharmacological interventions. The final step is extracorporeal membrane oxygenation weaning. A number of studies investigated the accuracy of some echocardiographic parameters in predicting success rate and demonstrated promising results. Parameters and threshold for successful weaning include aortic VTI ≥ 10 cm, LVEF > 20-25%, and lateral mitral annulus peak systolic velocity >6 cm/s. However, the effectiveness of echocardiography in ECPR patients cannot be determined in observational studies and requires randomized controlled trials in the future. The contents in this review are well known to echocardiography specialists; thus, it should be used as an educational material for emergency or intensive care physicians. There is a trend that focused echocardiography is performed by intensivists and emergency physicians.

Outcome of patients receiving CPR in the ED of an urban academic hospital

BACKGROUND

The success of Closed Chest Cardiopulmonary Resuscitation (CC-CPR) degrades with prolonged times. Open Chest CPR (OC-CPR) is an alternative that may lead to superior coronary and cerebral perfusion. It is critical to determine when continued CC-CPR is unlikely to be successful to justify initiating OC-CPR as rescue therapy. The purpose of this study is to review CC-CPR outcomes to define a time threshold for attempting OC-CPR.

METHODS

We identified all adult non-trauma patients diagnosed with cardiac arrest, ventricular fibrillation, ventricular tachycardia and asystole from 1/1/10-12/31/14. We collected demographics, cardiac rhythm, resuscitation duration, survival to hospital discharge and neurological outcome. Using time to ROSC after ED arrival and good neurological outcome, we explored various times as triggers for attempting OC-CPR.

RESULTS

Among 242 cases of CPR, 205 cases were out-of-hospital cardiac arrest (OHCA). Mean age was 63.7 (±16.9),woman comprised 29.8% (72/242), and median prehospital CPR time was 30 min (20-44). Patients suffering ED arrest had improved ROSC (54.1% vs. 12.7%, p<0.001) and survival to hospital discharge rates (37.8% vs. 2.9%, p<0.001) compared to OHCA. Patients achieving ROSC had median total CPR duration of 18 minutes (10 minutes of pre-hospital CPR) compared with patients without ROSC who had 45 minutes (30 pre-hospital) respectively. No patient receiving > 10 minutes of CPR in the ED survived to hospital discharge.

CONCLUSION

In patients suffering OHCA and requiring CC-CPR in the ED, overall survival rate to good neurologic function is low. OC-CPR could potentially be attempted after 10 minutes of CC-CPR in the ED.

Systematic review of the mechanisms driving effective blood flow during adult CPR

BACKGROUND

High quality chest compressions is the most significant factor related to improved short-term and long-term outcome in cardiac arrest. However, considerable controversy exists over the mechanisms involved in driving blood flow.

OBJECTIVES

The aim of this systematic review is to elucidate major mechanisms involved in effective compression-mediated blood flow during adult cardiopulmonary resuscitation (CPR).

DESIGN AND SETTING

Systematic review of studies identified from the bibliographic databases of PubMed/Medline, Cochrane, and Scopus.

SELECTION CRITERIA

All human and animal studies including information on the responsible mechanisms of compression-related blood flow.

DATA COLLECTION AND ANALYSIS

Two reviewers (MG, TX) independently screened all potentially relevant titles and abstracts for eligibility, by using a standardized data-worksheet.

MAIN RESULTS

Forty seven studies met the inclusion criteria. Because of the heterogeneity in outcome measures, quantitative synthesis of evidence was not feasible. Evidence was critically synthesized in order to answer the review questions, taking into account study heterogeneity and validity. The number of included studies per category is as follows: blood flow during chest compression, nine studies; blood flow during chest decompression, six studies; effect of chest compression on cerebral blood flow, eight studies; active compression-decompression CPR, 14 studies; and effect of ventilation on compression-related blood flow, 13 studies.

CONCLUSION

The evidence so far is inconclusive regarding the major responsible mechanism in compression-related blood flow. Although both 'cardiac pump' and 'thoracic pump' have a key role, the effect of each mechanism is highly depended on other resuscitation parameters, such as positive pressure ventilation and compression depth.

The use of emergency department thoracotomy for traumatic cardiopulmonary arrest

Despite the establishment of evidence-based guidelines for the resuscitation of critically injured patients who have sustained cardiopulmonary arrest, rapid decisions regarding patient salvageability in these situations remain difficult even for experienced physicians. Regardless, survival is limited after traumatic cardiopulmonary arrest. One applicable, well-described resuscitative technique is the emergency department thoracotomy-a procedure that, when applied correctly, is effective in saving small but significant numbers of critically injured patients. By understanding the indications, technical details, and predictors of survival along with the inherent risks and costs of emergency department thoracotomy, the physician is better equipped to make rapid futile versus salvageable decisions for this most severely injured subset of patients.

Six-year prospective audit of 'scoop and run' for chest-reopening after cardiac arrest in a cardiac surgical ward setting

OBJECTIVES

The aim of the study was to identify which cardiac surgical ward patients benefit from 'scoop and run' to the operating room for chest reopening.

METHODS

In-hospital arrests in a cardiothoracic hospital were prospectively audited over a 6-year period. The following pieces of information were collected for every patient who was scooped to the operating room following cardiac arrest on the postoperative cardiac surgical wards: type of arrest, time since surgery, patient physiology before arrest, time to chest reopening, location of chest opening, surgical findings on reopening, time to cardiopulmonary bypass (if used) and patient outcomes.

EXCLUSIONS

arrests in intensive care unit (ICU) and operating rooms. The primary outcome measure was survival to discharge from the hospital.

RESULTS

There were 99 confirmed ward arrests in 97 cardiac surgical patients. The overall survival rates to discharge and at 1 year were 53.6% (52 of 97 patients) and 44.3% (43 of 97 patients), respectively. Twenty-one of the 97 (21.6%) patients underwent scoop and run to the operating room or ICU. Five of 12 daytime 'scoop and runs' survived to discharge, whereas none of nine survived where scoop and run was undertaken at night (P < 0.05). There was a trend towards increased survival when 'scoop and run' was undertaken following ventricular fibrillation/pulseless ventricular tachycardia arrests (P = 0.06) and in younger patients (P = 0.12) but neither achieved statistical significance. The median time out from surgery of survivors was 4 days (range 2-14 days). The median time to chest opening in survivors was 22 min. Cardiopulmonary bypass was utilized in four of five survivors. The median ICU and hospital lengths of stay were 176 h (range 34-857) and 28 days (range 13-70), respectively.

CONCLUSIONS

The key determinant of a favourable 'scoop and run' outcome was whether the arrest occurred during daytime or night-time hours (P < 0.05). Despite a median time to chest opening of 22 min, all five survivors were discharged neurologically intact. The median time from surgery in these survivors was 4 days. Because of the risk of hypoxic brain damage, 'scoop and run' should be restricted to patients suffering witnessed arrests. The study has potential implications for resuscitation training and out-of-hours medical staffing in cardiothoracic hospitals.

Post-cardiac arrest syndrome: Mechanisms and evaluation of adrenal insufficiency

Cardiac arrest is one of the leading causes of death and represents maximal stress in humans. After restoration of spontaneous circulation, post-cardiac arrest syndrome is the predominant disorder in survivors. Besides the post-arrest brain injury, the post-resuscitation myocardial stunning, and the systemic ischemia/reperfusion response, this syndrome is characterized by adrenal insufficiency, a disorder that often remains undiagnosed. The pathophysiology of adrenal insufficiency has not been elucidated. We performed a comprehensive search of three medical databases in order to describe the major pathophysiological disturbances which are responsible for the occurrence of the disorder. Based on the available evidence, this article will help physicians to better evaluate and understand the hidden yet deadly post-cardiac arrest adrenal insufficiency.

Post-cardiac arrest brain injury: pathophysiology and treatment

Cardiac arrest is a leading cause of death that affects more than a million individuals worldwide every year. Despite the recent advancement in the field of cardiac arrest and resuscitation, the management and prognosis of post-cardiac arrest brain injury remain suboptimal. The pathophysiology of post-cardiac arrest brain injury involves a complex cascade of molecular events, most of which remain unknown. Considering that a potentially broad therapeutic window for neuroprotective drug therapy is offered in most successfully resuscitated patient after cardiac arrest, the need for further research is imperative. The aim of this article is to present the major pathophysiological disturbances leading to post-cardiac arrest brain injury, as well as to review the available pharmacological therapies.

Retrospective analysis of emergency room thoracotomy in pediatric severe trauma patients

BACKGROUND

Although the integral role of ED thoracotomy for open cardiac massage has been extensively reviewed in adult literature, this "heroic maneuver" remains very controversial and greatly debated in children.

METHODS AND RESULTS

A retrospective cohort review of emergency thoracotomies in children, performed at a European Level I trauma center between 1992 and 2008 was undertaken. Clinical manifestation, injury mechanism and surgical treatment were described, with special regard to prognostic factors and outcome. A total of eleven thoracotomies were performed, ten for blunt injuries (91%), and one for perforating injury (9%), with a mean age of 7.8 years, range 2.6-15.4 years, comprising eight boys and three girls. The mean Injury Severity Score of the children with blunt force trauma was 46, ranging from 25 to 66 compared with 20 of the penetrating trauma victim. Ten of eleven patients (91%) who underwent ED thoracotomy died. Nine of them were in cardiac arrest on arrival. One patient who had a penetrating knife injury and had stable vital sign on arrival survived.

CONCLUSIONS

Similar to previous studies, out data confirmed ED thoracotomy for children in cardiac arrest from blunt trauma had universally fatal outcome. The mechanism of injury and signs of life at arrival were predictive key factors that influence the outcome of ED thoracotomy.

Randomised comparison of percutaneous left ventricular assist device with open-chest cardiac massage and with surgical assist device during ischaemic cardiac arrest

AIMS

A percutaneous left ventricular assist device can maintain blood flow to vital organs during ventricular fibrillation and may improve outcomes in ischaemic cardiac arrest. We compared haemodynamic and clinical effects of a percutaneous left ventricular assist device with a larger device deployed via endovascular prosthesis and with open-chest cardiac massage during ischaemic cardiac arrest.

METHODS

Eighteen swine were randomised into three groups. After thoracotomy, coronary ischaemia and ventricular fibrillation was induced. Cardiac output was measured with transit-time flowmetry. Tissue perfusion was measured with microspheres. Defibrillation was performed after 20 min.

RESULTS

Cardiac output with cardiac massage was 1129 mL min⁻¹ vs. 1169 mL min⁻¹ with the percutaneous- and 570 mL min⁻¹ with the surgical device (P < 0.05 surgical vs. others). End-tidal CO₂ was 3.3 kPa with cardiac massage vs. 3.2 kPa with the percutaneous- and 2.3 kPa with the surgical device (P < 0.05 surgical vs. others). Subepicardial perfusion was 0.33 mL min⁻¹ g⁻¹ with cardiac massage vs. 0.62 mL min⁻¹ g⁻¹ with both devices (P < 0.05 devices vs. massage), cerebral perfusion was comparable between groups (all reported values after 3 min cardiac arrest, all P<0.05 vs. baseline, all P = NS for 3 min vs. 15 min). Return of spontaneous circulation was achieved in 5/6 subjects with cardiac massage vs. 6/6 with the percutaneous- and 4/6 with the surgical device (P = NS).

CONCLUSION

The percutaneous device improved myocardial perfusion, maintained cerebral perfusion and systemic circulation with similar rates of successful defibrillation vs. cardiac massage. Increased delivery was not obtained with the surgical device during cardiac arrest.

Emergency department thoracotomy: still useful after abdominal exsanguination?

BACKGROUND

Although literature regarding emergency department thoracotomy (EDT) outcome after abdominal exsanguination is limited, numerous reports have documented poor EDT survival in patients with anatomic injuries other than cardiac wounds. As a result, many trauma surgeons consider prelaparotomy EDT futile for patients dying from intra-abdominal hemorrhage. Our primary study objective was to prove that prelaparotomy EDT is beneficial to patients with exsanguinating abdominal hemorrhage.

METHODS

A retrospective review of 237 consecutive EDTs for penetrating injury (2000-2006) revealed 50 patients who underwent EDT for abdominal exsanguination. Age, gender, injury mechanism and location, field and emergency department (ED) signs of life, prehospital time, initial ED cardiac rhythm, vital signs, Glasgow Coma Score, blood transfusion requirements, predicted mortality, primary abdominal injuries, and the need for temporary abdominal closure were analyzed. The primary study endpoint was neurologically intact hospital survival.

RESULTS

The 50 patients who underwent prelaparotomy EDT for abdominal exsanguination were largely young (mean, 27.3 +/- 8.2 years) males (94%) suffering firearm injuries (98%). Patients presented with field (84%) and ED signs of life (78%) after a mean prehospital time of 21.2 +/- 9.8 minutes. Initial ED cardiac rhythms were variable and Glasgow Coma Score was depressed (mean, 4.2 +/- 3.2). Eight (16%) patients survived hospitalization, neurologically intact. Of these eight, all were in hemorrhagic shock because of major abdominal vascular (75%) or severe liver injuries (25%) and all required massive blood transfusion (mean, 28.6 +/- 17.3 units) and extended intensive care unit length of stay (mean, 36.3 +/- 25.7 days).

CONCLUSIONS

Despite critical injuries, 16% survived hospitalization, neurologically intact, after EDT for abdominal exsanguination. Our results suggest that prelaparotomy EDT provides survival benefit to penetrating trauma victims dying from intra-abdominal hemorrhage.

Haemodynamics of cardiac arrest and resuscitation

PURPOSE OF REVIEW

This review will summarize the available data regarding the haemodynamic changes occurring following cardiac arrest in humans and animal models.

RECENT FINDINGS

Following cardiac arrest due to ventricular fibrillation without cardiopulmonary resuscitation, blood flow exponentially falls but continues for approximately 5 min until the pressure gradient between the aorta and the right heart is completely dissipated. During cardiopulmonary resuscitation forward flow occurs into the aorta during the compression phase. Coronary blood flow is retrograde during the compression phase and antegrade during the decompression phase. Carotid blood flow takes over a minute to reach plateau levels following the initiation of chest compressions, and even brief interruptions of compressions result in a dramatic reduction in carotid blood flow which takes a minute or so to recover to plateau levels when compressions are reinstituted. Coronary perfusion pressure during the release phase of cardiopulmonary resuscitation has been shown to be a powerful predictor of the likelihood of recovery of spontaneous circulation following restoration of electrical activity.

SUMMARY

Recent studies have provided important insights into the haemodynamics of cardiac arrest and of cardiopulmonary resuscitation which may inform more effective strategies for the management of cardiac arrest in the future.

Open-chest cardiopulmonary resuscitation: past, present and future

Out-of-hospital cardiac arrests account for approximately 1000 sudden cardiac deaths per day in the United States. Since its introduction in 1960 closed-chest cardiac massage (CCCM) often takes place as an attempt at resuscitation, although its survival rates are low. Other resuscitation techniques are available to physicians such as open-chest cardiopulmonary resuscitation (OCCPR). OCCPR has been shown by several scientists to be hemodynamically superior to CCCM as it increases arterial pressures, cardiac output, coronary perfusion pressures, return of spontaneous circulation and cerebral blood flow. Improved neurological and cardiovascular outcome and an increase in survival rate compared to CCCM have been described. Timing is one of the key variables in determining patient outcome when performing OCCPR. The American Heart Association in association with the International Liaison Committee (ILCOR) has specific indications for the use of OCCPR. Some investigators recommend starting OCCPR in out-of-hospital cardiac arrests on arrival at the scene instead of CCCM. Surprisingly, the incidence of infectious complications after thoracotomy in an unprepared chest is low. The vast majority of the patients' families accept OCCPR as a therapeutic choice for cardiac arrests and it has been showed to be economically viable. This paper reviews some of the basic and advanced concepts of this evolving technique.

Open-chest CPR improves survival and neurologic outcome following cardiac arrest

STUDY OBJECTIVE

To determine if 15 min of open-chest cardiac massage (OC-CPR) versus closed-chest compressions (CC-CPR) improves 72-h survival and neurologic outcome (behavioral and histologic) after 5 min of untreated cardiac arrest.

METHODS

Mongrel dogs were anesthetized and instrumented. Cardiac arrest was induced by KCl injection and after a 5-min period of non-intervention, dogs were randomized to receive either CC-CPR (N = 7) or OC-CPR (N = 5) performed for 15 min. The dogs were then resuscitated and physiologic data was recorded. Surviving dogs were scored at 72 h using canine neurodeficit score of Safar et al. (NDS; 0 = behaviorally normal, 500 = brain death). Dogs that could not be resuscitated or died before 72 h were assigned a score of 500. Brain histology was performed on all survivors.

RESULTS

All OC-CPR dogs were successfully resuscitated and were behaviorally normal at 72 h (NDS = 0). Histology in OC-CPR dogs showed little to no injury. Only three out of the seven CC-CPR dogs survived to 72 h. Of the survivors, one dog exhibited minor ataxia (NDS = 15), and two had incapacitating deficits (both NDS = 180). Two dogs died within 24 h after extubation, and one could not be resuscitated and the other could not be weaned from the ventilator (each NDS = 500). Histology of the CC-CPR survivors revealed moderate to severe lesions. NDS between groups was statistically significant (p < 0.0079).

CONCLUSION

In our canine model of cardiac arrest, OC-CPR significantly improved 72-h survival and neurologic outcome when compared to CC-CPR.

Open-Chest Cardiopulmonary Resuscitation after Cardiac Arrest in Cases of Blunt Chest or Abdominal Trauma: A Consecutive Series of 38 Cases

BACKGROUND

According to the literature, the overall outcome in a patient population with chest or abdominal injury with initial cardiac arrest has to be rated as poor. In cases of penetrating injuries, open-chest cardiopulmonary resuscitation (CPR) has been recommended as a treatment option to improve the survival rate. The aim of this study was to prove equal outcome for patients with blunt chest or abdominal trauma.

METHODS

During a 5-year period, a consecutive patient series admitted to an urban Level I trauma center was examined. Only patients with blunt trauma and witnessed cardiac arrest, who had a documented, uninterrupted closed-chest CPR (CCCPR) of less than 20 minutes were included in this study (n=38). Exclusion criteria were age over 70 years, penetrating injuries, CCCPR of more than 20 minutes, as well as nonprofessional bystander resuscitation.

RESULTS

Four of 38 patients survived. In comparison with the group of nonsurvivors, both groups showed a similar age and gender ratio (mean age, 28, 32, respectively). The mean Injury Severity Scale was 54 (range, 42-66) in the survivor group and 66 (range, 29-75) in the nonsurvivor group, respectively. The time of CCCPR was on average 13 minutes (range, 11-15 minutes) for the survivors and 16 minutes (range, 1-20 minutes) for the nonsurvivors.

CONCLUSION

Patients with blunt trunk trauma and cardiac arrest after hemorrhagic shock may benefit from open-chest CPR with the same probability as shown for patients with penetrating injuries. This is especially true if the procedure is started as soon as possible, but at the latest within 20 minutes after initial CCCPR.

Cardiac output, coronary blood flow, and blood gases during open-chest standard and compression-active-decompression cardiopulmonary resuscitation

OBJECTIVE

To determine whether open-chest compression-active-decompression (CAD) could improve cardiac output, coronary blood flow, blood gases, and resuscitation compared to open-chest manual compression in a porcine model of cardiac arrest.

DESIGN

Prospective, randomized laboratory investigation for measurement of cardiac output, coronary blood flow, arterial and mixed venous blood gases and potassium levels, and return of spontaneous circulation.

SUBJECTS

Ten pigs each weighing approximately 36.4 kg.

INTERVENTIONS

Following preparation of the model and opening of the chest, ultrasonic flow probes were placed on the ascending aorta and left anterior descending artery. Cardiac arrest was induced by epicardial pacing. Subjects received either open-chest CAD or open-chest manual compression. After 10 min of arrest, defibrillation was attempted.

MEASUREMENTS AND MAIN RESULTS

Cardiac output fell to 46+/-53% (95% CI: -20 to 112) and 41+/-14% (95% CI: 23-59) (P>0.05) of baseline with CAD and manual methods at 5 min after arrest, respectively. Similarly, coronary blood flow fell to 33+/-14% (95% CI: 16-50) and 42+/-16% (95% CI: 22-62) (P>0.05) of baseline at 5 min. Both groups developed similar levels of metabolic acidosis, mixed venous hypoxemia, and hyperkalemia, with potassium levels: 6.5+/-4.0 meq/l (95% CI: 1.6-11.4) at 5 min and 7.5+/-4.6 meq/l (95% CI: 1.8-13.2) at 10 min in the CAD group and 5.8+/-2.0 meq/l (95% CI: 3.4-8.3) at 5 min and 6.1+/-1.4 meq/l (95% CI: 4.4-7.9) at 10 min in the manual group. Levels of hyperkalemia were inversely proportional to the square of PvO(2). One pig in each group was resuscitated after defibrillation.

CONCLUSION

We found no benefit using CAD. Both low coronary blood flow and hyperkalemia may have limited resuscitation.

Is emergency open chest cardiopulmonary resuscitation accepted by patients' families?

Emergency open chest cardiopulmonary resuscitation (OCCPR) is sometimes performed on patients with cardiopulmonary arrest (CPA), especially those resulting from trauma. Since OCCPR is frequently carried out without the permission of patients' families, we surveyed the opinions of the families. A total of 1058 CPA patients were transferred to our department during the last 15 years. We sent questionnaires individually to the families of these patients to ask their opinions about OCCPR. The questionnaire provided the six questions allowing multiple answers; (1) Do you unconditionally agree with OCCPR? (2) Do you agree with OCCPR in children? (3) Do you agree with OCCPR in elderly patients? (4) Do you agree with OCCPR without permission from patient's families? (5) Do you entrust OCCPR to the doctors in charge? and (6) others. The questionnaire reached 846 families, of which 277 (32.7%) responded. The percentage response to each question was (1) 70.2, (2) 5.8, (3) 21.8, (4) 7.1, (5) 4.2 and (6) 5.0%. The younger the age of the responders the more they agreed with OCCPR. All the responders less than 30 years old agreed with the procedure. Of the 277 families, 95 had CPA patients treated with OCCPR. This group of families responded to six questions at the following rates: (1) 79.5, (2) 6.0, (3) 13.3, (4) 2. 4, (5) 4.8 and (6) 4.8%, suggesting that families with OCCPR patients are more cooperative to our treatment than those with non-OCCPR patients. The results of this study suggest that OCCPR in CPA patients is generally accepted by the patients' families, especially by young generations, although post-OCCPR careful explanation to patients' families is still indispensable.

Effects of vasopressin and epinephrine on splanchnic blood flow and renal function during and after cardiopulmonary resuscitation in pigs

OBJECTIVE

To compare the effects of vasopressin versus epinephrine on splanchnic blood flow during and after cardiopulmonary resuscitation (CPR), and to evaluate the effects of these vasopressors on renal function in the postresuscitation phase.

DESIGN

Prospective, randomized laboratory investigation using an established porcine CPR model with instrumentation for continuous measurement of splanchnic and renal blood flow.

SETTING

University hospital experimental laboratory.

SUBJECTS

A total of 12 anesthetized, 12- to 16-wk-old domestic pigs weighing 30-35 kg.

INTERVENTIONS

After 4 mins of cardiac arrest, and 3 mins of CPR, 12 pigs were randomly assigned to receive either 0.4 units/kg vasopressin (n = 6) or 45 microg/kg epinephrine (n = 6). Defibrillation was performed 5 mins after drug administration; all animals were observed for 6 hrs after return of spontaneous circulation (ROSC).

MEASUREMENTS AND MAIN RESULTS

Mean +/- SEM superior mesenteric artery blood flow was significantly (p < .05) lower after vasopressin compared with epinephrine at 90 secs after drug administration (13+/-3 vs. 129+/-33 mL/min); at 5 mins after drug administration (31+/-18 vs. 155+/-39 mL/min); at 5 mins after ROSC (332+/-47 vs. 1087+/-166 mL/min); and at 15 mins after ROSC (450+/-106 vs. 1130+/-222 mL/min); respectively. Mean +/- SEM left renal and hepatic artery blood flow after ROSC was comparable in both groups ranging between 120-290 mL/min (renal blood flow), and 150-360 mL/min (hepatic blood flow), respectively. Median urine output after ROSC showed no difference between groups, and highest values (180-220 mL/hr) were observed in the first 60 mins after ROSC. Median calculated glomerular filtration rate showed no difference between groups with values ranging between 30 and 80 mL/min in the postresuscitation phase. Calculated fractional sodium excretion and osmolar relationship between urea and plasma indicated no evidence for renal tubular dysfunction.

CONCLUSIONS

In the early postresuscitation phase, superior mesenteric blood flow was temporarily impaired by vasopressin in comparison with epinephrine. With respect to renal blood flow and renal function after ROSC, there was no difference between either vasopressor given during CPR. Vasopressin given during CPR did not result in an antidiuretic state in the postresuscitation phase.

Intra-aortic administration of epinephrine above aortic occlusion does not alter outcome of experimental cardiopulmonary resuscitation

Intra-aortic balloon occlusion during experimental cardiopulmonary resuscitation (CPR) improves coronary perfusion pressure and resuscitability and provides unique access to the central circulation. It has been hypothesized that administration of epinephrine into the aortic arch in combination with aortic occlusion would further improve haemodynamics during CPR, resuscitability and 24 h survival. In 16 anaesthetised dogs intravascular catheters were placed for hemodynamic and blood gas monitoring. An aortic balloon catheter was placed by femoral artery insertion with its tip just distal to the left subclavian artery. Ventricular fibrillation for 7.5 min without CPR, 2.5 min of Basic Life Support with chest compressions and ventilation with 100% oxygen were followed by 30 min of Advanced Cardiac Life Support (ACLS) with systemic canine drug dosages. The intra-aortic balloon was inflated when ACLS started and gradually deflated shortly after restoration of spontaneous circulation (ROSC). Epinephrine, in 100 microg/kg boluses every 5 min until the heart was restarted or 30 min had elapsed was administered through the intra-aortic catheter in the experimental group (n = 8) and via a central venous catheter in the control group (n = 8). Coronary perfusion pressure increased during the ACLS period in both groups (P < 0.05) with no difference between the groups and there was no difference in the frequency of ROSC (experimental group 5/8, control group 4/8). Furthermore with respect to 24 h survival, there was no difference between the experimental group (2/8) and the control group (3/8). Severe macroscopic haemorrhagic necrosis of the myocardium in the dogs with ROSC was found in 4/5 in the experimental group compared to 1/4 in the control group. In conclusion, intra-aortic administration of 100 microg/kg epinephrine doses combined with aortic occlusion during experimental CPR did not alter outcome.

Systemic oxygen uptake during experimental closed-chest cardiopulmonary resuscitation using air or pure oxygen ventilation

BACKGROUND

Although clinical cardiopulmonary resuscitation always includes ventilation with pure oxygen, this kind of ventilation has been reported to be associated with worse neurological outcome than ventilation with air in experimental cardiopulmonary resuscitation (CPR). The aim of the present investigation was to compare the systemic oxygen uptake during experimental closed-chest CPR including ventilation with pure oxygen or ambient air and, furthermore, to elucidate possible mechanisms of action in the regulation of pulmonary gas exchange.

METHODS

In 24 anesthetized piglets, 2 min of induced ventricular fibrillation and no ventilation was followed by 10 min of closed-chest CPR including i.v. administration of 0.5 mg adrenaline (at 8 min), and in one of the experimental groups alkaline buffer (at 5 min). The piglets were randomly divided into 3 groups: air ventilation during the entire CPR period with saline administration (n=8), air ventilation during the entire CPR period plus tris buffer mixture (n=8), and air ventilation for 3 min followed by 100% oxygen with saline administration (n= 8).

RESULTS

In the group ventilated with air and treated with tris buffer mixture, cardiac output was significantly greater than in the group ventilated with pure oxygen. The arterial-mixed venous oxygen content difference was approximately 25% greater with pure oxygen than with air ventilation; however, there was no difference in systemic oxygen uptake. Systemic oxygen uptake increased after administration of tris buffer mixture in the group ventilated with air.

CONCLUSIONS

Pulmonary hypoxic vasoconstriction appeared to be abolished during CPR including pure oxygen ventilation. Blood flow, not ventilation or pulmonary gas exchange, is the limiting factor during experimental closed-chest CPR.

Mixed venous oxygen saturation and biochemical parameters of hypoxia during progressive hypoxemia in 10- to 14-day-old piglets

In this study we wanted to assess the relationship between mixed venous oxygen saturation (SVO2) and tissue oxygenation. For that, we compared the values of SVO2 with oxygen delivery (DO2), oxygen consumption (VO2), and markers of tissue hypoxia such as lactate and pyruvate during progressive hypoxemia. Eight 10-14-d-old piglets were anesthetized, tracheotomized, intubated, and ventilated. A fiberoptic catheter was placed in the carotid artery to monitor arterial oxygen saturation (SaO2). A thoracotomy was performed, and a fiberoptic catheter was placed in the pulmonary artery to monitor SVO2. A transit time ultrasound flow probe was positioned around the ascending aorta to measure aorta flow. Progressive graded hypoxemia was induced by decreasing fractional inspiratory oxygen concentration (FIO2) from 1.0 to 0.30, 0.21, 0.15, and 0.10. After each FIO2 interval blood samples were taken for blood gases, lactate, and pyruvate. DO2 and VO2 were calculated. SVO2 decreased similarly to SaO2. A value of SVO2 of more than 40% excluded oxygen restricted metabolism. When DO2 decreased below a critical range (8.4-12.8 mL/kg x min), SVO2 decreased below 15%, and lactate and the lactate/pyruvate ratio increased. We conclude 1) that baseline SVO2 values excluded oxygen-restricted metabolism, 2) that SVO2 values between 15 and 40% were not a marker for oxygen-restricted metabolism, and 3) that SVO2 values below 15% were associated with oxygen-restricted metabolism. Reduced SVO2 values must be interpreted as a change of the factors that determine the balance between DO2 and VO2 and as a warning that, with further reduction of SVO2, oxygen restricted metabolism can develop.

Future directions for resuscitation research. V. Ultra-advanced life support

Standard external cardiopulmonary resuscitation (SECPR) frequently produces very low perfusion pressures, which are inadequate to achieve restoration of spontaneous circulation (ROSC) and intact survival, particularly when the heart is diseased. Ultra-advanced life support (UALS) techniques may allow support of vital organ systems until either the heart recovers or cardiac repair or replacement is performed. Closed-chest emergency cardiopulmonary bypass (CPB) provides control of blood flow, pressure, composition and temperature, but has so far been applied relatively late. This additional low-flow time may preclude conscious survival. An easy, quick method for vessel access and a small preprimed system that could be taken into the field are needed. Open-chest CPR (OCCPR) is physiologically superior to SECPR, but has also been initiated too late in prior studies. Its application in the field has recently proven feasible. Variations of OCCPR, which deserve clinical trials inside and outside hospitals, include 'minimally invasive direct cardiac massage' (MIDCM), using a pocket-size plunger-like device inserted via a small incision and 'direct mechanical ventricular actuation' (DMVA), using a machine that pneumatically drives a cup placed around the heart. Other novel UALS approaches for further research include the use of an aortic balloon catheter to improve coronary and cerebral blood flow during SECPR, aortic flush techniques and a double-balloon aortic catheter that could allow separate perfusion (and cooling) of the heart, brain and viscera for optimal resuscitation of each. Decision-making, initiation of UALS methods and diagnostic evaluations must be rapid to maximize the potential for ROSC and facilitate decision-making regarding long-term circulatory support versus withdrawal of life support for hopeless cases. Research and development of UALS techniques needs to be coordinated with cerebral resuscitation research.

Adverse effects of interrupting precordial compression during cardiopulmonary resuscitation

OBJECTIVES

In the current operation of automated external defibrillators, substantial time may be consumed for a "hands off" interval during which precordial compression is discontinued to allow for automated rhythm analyses before delivery of the electric countershock. The effects of such a pause on the outcomes of cardiopulmonary resuscitation were investigated.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Ventricular fibrillation was electrically induced in 25 Sprague-Dawley rats. After 4 mins of untreated ventricular fibrillation, precordial compression was begun and continued for 6 mins. Animals were then randomized to receive an immediate defibrillation shock or the defibrillation attempt was delayed for intervals of 10, 20, 30, or 40 secs.

MEASUREMENTS AND MAIN RESULTS

Immediate defibrillation restored spontaneous circulation in each instance. When defibrillation was delayed for 10 or 20 secs, spontaneous circulation was restored in three of five animals in each group. After a 30-sec delay, spontaneous circulation was restored in only one of five animals (p < .05). No animal was successfully resuscitated after a 40-sec delay (p < .01). With increasing delays, 24- and 48-hr survival rates were correspondingly reduced.

CONCLUSIONS

During resuscitation from ventricular fibrillation, prolongation of the interval between discontinuation of precordial compression and delivery of the first electric countershock substantially compromises the success of cardiac resuscitation. Accordingly, automated defibrillators are likely to be maximally effective if they are programmed to secure minimal "hands off" delay before delivery of the electric countershock.

Can a class III antiarrhythmic drug improve electrical defibrillation efficacy during ventricular fibrillation?

OBJECTIVES

We tested whether a new class III drug (MS-551) administered during ventricular fibrillation (VF) could decrease the defibrillation threshold (DFT) in anesthetized canine hearts.

BACKGROUND

Pretreatment with class III antiarrhythmic agents is known to enhance electrical defibrillation efficacy.

METHODS

In a preliminary study (n = 10), we ascertained the validity of DFT determination by a sequence of incremental defibrillation shocks in a single fibrillation/defibrillation episode. We then compared the DFTs after 130 s of VF with and without administration of MS-551 (2 mg/kg body weight) at 10 s after the onset of VF in 12 open chest dogs and 8 closed chest dogs.

RESULTS

MS-551 decreased the DFT in both experimental models (open chest [mean +/- SD]: from 416 +/- 106 to 318 +/- 92 V, p < 0.05; closed chest: from 714 +/- 75 to 615 +/- 112 V, p < 0.05). The change (delta) in DFT in each heart was inversely correlated with the drug-induced prolongation of VF cycle length before the defibrillation attempt (delta DFT vs. delta VF cycle length 10 s before the first discharge: r = -0.58 and -0.81, p < 0.05).

CONCLUSIONS

MS-551 given after the induction of VF improved defibrillation efficacy. Class III antiarrhythmic agents deserve consideration when VF is resistant to electrical defibrillation during cardiopulmonary resuscitation.

Future directions for resuscitation research. IV. Innovative advanced life support pharmacology

The topics discussed in this session include a partial review of laboratory and clinical studies examining the effects of adrenergic agonists on restoration of spontaneous circulation after cardiac arrest, the effects of varying doses of epinephrine, and the effects of novel vasopressors, buffer agents (NaHCO3, THAM, 'Carbicarb') and anti-arrhythmics (lidocaine, bretylium, amiodarone) in refractory ventricular fibrillation. Novel therapeutic approaches include titrating electric countershocks against electrocardiographic power spectra and of preceding the first countershocks with single or multiple drug treatments. These approaches need to be investigated further in controlled animal and patient studies. Epidemiologic data from randomized clinical outcome studies can give clues, but cannot document pharmacologic mechanisms in the dynamically changing events during attempts to achieve restoration of spontaneous circulation from prolonged cardiac arrest. Also, rapid drug administration by the intraosseous route was compared with intratracheal and intravenous (i.v.) drug administration. Many studies on the above treatments have yielded conflicting results because of differences between healthy hearts of animals and sick hearts of patients, differences in arrest (no-flow) times and cardiopulmonary resuscitation (CPR) (low-flow) times, different pharmacokinetics, different dose/response requirements, and different timing of drug administration during low-flow CPR versus during spontaneous circulation. The need to stabilize normotension and prevent rearrest by titrated novel drug administration, once spontaneous circulation has been restored, requires research. Most of the above topics require some re-evaluation in clinically realistic animal models and in cardiac arrest patients, especially by titration of old and new drug treatments against variables that can be monitored continuously during resuscitation.