The effects of prehospital TXA on mortality and neurologic outcomes in patients with traumatic intracranial hemorrhage: a subgroup analysis from the prehospital TXA for TBI trial

BACKGROUND

In the Prehospital Tranexamic Acid (TXA) for TBI Trial, TXA administered within two hours of injury in the out-of-hospital setting did not reduce mortality in all patients with moderate/severe traumatic brain injury (TBI). We examined the association between TXA dosing arms, neurologic outcome, and mortality in patients with intracranial hemorrhage (ICH) on computed tomography (CT).

METHODS

This was a secondary analysis of the Prehospital Tranexamic Acid for TBI Trial (ClinicalTrials.gov [NCT01990768]) that randomized adults with moderate/severe TBI (Glasgow Coma Scale<13) and systolic blood pressure > =90 mmHg within two hours of injury to a 2-gram out-of-hospital TXA bolus followed by an in-hospital saline infusion, a 1-gram out-of-hospital TXA bolus/1-gram in-hospital TXA infusion, or an out-of-hospital saline bolus/in-hospital saline infusion (placebo). This analysis included the subgroup with ICH on initial CT. Primary outcomes included 28-day mortality, 6-month Glasgow Outcome Scale-Extended (GOSE) < = 4, and 6-month Disability Rating Scale (DRS). Outcomes were modeled using linear regression with robust standard errors.

RESULTS

The primary trial included 966 patients. Among 541 participants with ICH, 28-day mortality was lower in the 2-gram TXA bolus group (17%) compared to the other two groups (1-gram bolus/1-gram infusion 26%, placebo 27%). The estimated adjusted difference between the 2-gram bolus and placebo groups was -8·5 percentage points (95% CI, -15.9 to -1.0) and between the 2-gram bolus and 1-gram bolus/1-gram infusion groups was -10.2 percentage points (95% CI, -17.6 to -2.9). DRS at 6 months was lower in the 2-gram TXA bolus group than the 1-gram bolus/1-gram infusion (estimated difference -2.1 [95% CI, -4.2 to -0.02]) and placebo groups (-2.2 [95% CI, -4.3, -0.2]). Six-month GOSE did not differ among groups.

CONCLUSIONS

A 2-gram out-of-hospital TXA bolus in patients with moderate/severe TBI and ICH resulted in lower 28-day mortality and lower 6-month DRS than placebo and standard TXA dosing.

LEVEL OF EVIDENCE

Therapeutic/Care Management, Level II.

Airway Strategy and Ventilation Rates in the Pragmatic Airway Resuscitation Trial

BACKGROUND

We sought to describe ventilation rates during out-of-hospital cardiac arrest (OHCA) resuscitation and their associations with airway management strategy and outcomes.

METHODS

We analyzed continuous end-tidal carbon dioxide capnography data from adult OHCA enrolled in the Pragmatic Airway Resuscitation Trial (PART). Using automated signal processing techniques, we determined continuous ventilation rate for consecutive 10-second epochs after airway insertion. We defined hypoventilation as a ventilation rate <6 breaths/min. We defined hyperventilation as a ventilation rate >12 breaths/min. We compared differences in total and percentage post-airway hyper- and hypoventilation between airway interventions (laryngeal tube (LT) vs. endotracheal intubation (ETI). We also determined associations between hypo-/hyperventilation and OHCA outcomes (ROSC, 72-hour survival, hospital survival, hospital survival with favorable neurologic status).

RESULTS

Adequate post-airway capnography were available for 1,010 (LT n=714, ETI n=296) of 3,004 patients. Median ventilation rates were: LT 8.0 (IQR 6.5-9.6) breaths/min, ETI 7.9 (6.5-9.7) breaths/min. Total duration and percentage of post-airway time with hypoventilation were similar between LT and ETI: median 1.8 vs. 1.7 minutes, p=0.94; median 10.5% vs. 11.5%, p=0.60. Total duration and percentage of post-airway time with hyperventilation were similar between LT and ETI: median 0.4 vs. 0.4 minutes, p=0.91; median 2.1% vs. 1.9%, p=0.99. Hypo- and hyperventilation exhibited limited associations with OHCA outcomes.

CONCLUSION

In the PART Trial, EMS personnel delivered post-airway ventilations at rates satisfying international guidelines, with only limited hypo- or hyperventilation. Hypo- and hyperventilation durations did not differ between airway management strategy and exhibited uncertain associations with OCHA outcomes.

Airway strategy and chest compression quality in the Pragmatic Airway Resuscitation Trial

BACKGROUND

Chest compression (CC) quality is associated with improved out-of-hospital cardiopulmonary arrest (OHCA) outcomes. Airway management efforts may adversely influence CC quality. We sought to compare the effects of initial laryngeal tube (LT) and initial endotracheal intubation (ETI) airway management strategies upon chest compression fraction (CCF), rate and interruptions in the Pragmatic Airway Resuscitation Trial (PART).

METHODS

We analyzed CPR process files collected from adult OHCA enrolled in PART. We used automated signal processing techniques and a graphical user interface to calculate CC quality measures and defined interruptions as pauses in chest compressions longer than 3 s. We determined CC fraction, rate and interruptions (number and total duration) for the entire resuscitation and compared differences between LT and ETI using t-tests. We repeated the analysis stratified by time before, during and after airway insertion as well as by successive 3-min time segments. We also compared CC quality between single vs. multiple airway insertion attempts, as well as between bag-valve-mask (BVM-only) vs. ETI or LT.

RESULTS

Of 3004 patients enrolled in PART, CPR process data were available for 1996 (1001 LT, 995 ETI). Mean CPR analysis duration were: LT 22.6 ± 10.8 min vs. ETI 25.3 ± 11.3 min (p < 0.001). Mean CC fraction (LT 88% vs. ETI 87%, p = 0.05) and rate (LT 114 vs. ETI 114 compressions per minute (cpm), p = 0.59) were similar between LT and ETI. Median number of CC interruptions were: LT 11 vs. ETI 12 (p = 0.001). Total CC interruption duration was lower for LT than ETI (LT 160 vs. ETI 181 s, p = 0.002); this difference was larger before airway insertion (LT 56 vs. ETI 78 s, p < 0.001). There were no differences in CC quality when stratified by 3-min time epochs.

CONCLUSION

In the PART trial, compared with ETI, LT was associated with shorter total CC interruption duration but not other CC quality measures. CC quality may be associated with OHCA airway management.

Delphi Analysis of Science Gaps in the 2015 American Heart Association Cardiac Arrest Guidelines

Background

Current cardiac arrest guidelines have limited high‐quality scientific evidence to support recommendations for care. The quality of scientific evidence on which guidelines are based may correlate with improved patient outcomes and meaningful survival. We sought to develop a prioritized list of knowledge gaps in resuscitation to assist researchers, policy makers, and funding agencies in their decision‐making process.

Methods and Results

A 4‐stage modified Delphi method was used with a panel of cardiac arrest experts. Experts addressed the prompt: “What are the top 3 gaps in knowledge involving cardiac arrest care that should be research priorities for National Institutes of Health/American Heart Association funding to have the greatest impact on public health?” Knowledge gaps were identified in the initial round, rated in a second round, and rank ordered in the third round, and they underwent final review and consensus (final round). The outcome was 10 knowledge gaps, with prioritization of the top 3 gaps. A total of 61 gaps, with 19 distinct themes, were identified by participants. The 10 knowledge gaps most likely to affect public health identified by the expert panel included, in order, the following: telecommunicator cardiopulmonary resuscitation, hemodynamic monitoring for goal‐directed resuscitation, reasons why bystanders fail to respond, optimization of postarrest care, out‐of‐hospital cardiac arrest identification and response, individualizing resuscitation strategies, predicting patients at risk, tools for neuroprognostication, optimal airway management, and optimizing educational strategies.

Conclusions

Ten priorities for cardiac arrest research were identified, but consensus was not reached on the prioritized top 3. Future research should address these gaps to potentially improve resuscitation guideline evidence quality.

Impact of Bystander Automated External Defibrillator Use on Survival and Functional Outcomes in Shockable Observed Public Cardiac Arrests

BACKGROUND

Survival following out-of-hospital cardiac arrest (OHCA) with shockable rhythms can be improved with early defibrillation. Although shockable OHCA accounts for only ≈25% of overall arrests, ≈60% of public OHCAs are shockable, offering the possibility of restoring thousands of individuals to full recovery with early defibrillation by bystanders. We sought to determine the association of bystander automated external defibrillator use with survival and functional outcomes in shockable observed public OHCA.

METHODS

From 2011 to 2015, the Resuscitation Outcomes Consortium prospectively collected detailed information on all cardiac arrests at 9 regional centers. The exposures were shock administration by a bystander-applied automated external defibrillator in comparison with initial defibrillation by emergency medical services. The primary outcome measure was discharge with normal or near-normal (favorable) functional status defined as a modified Rankin Score ≤2. Survival to hospital discharge was the secondary outcome measure.

RESULTS

Among 49 555 OHCAs, 4115 (8.3%) observed public OHCAs were analyzed, of which 2500 (60.8%) were shockable. A bystander shock was applied in 18.8% of the shockable arrests. Patients shocked by a bystander were significantly more likely to survive to discharge (66.5% versus 43.0%) and be discharged with favorable functional outcome (57.1% versus 32.7%) than patients initially shocked by emergency medical services. After adjusting for known predictors of outcome, the odds ratio associated with a bystander shock was 2.62 (95% confidence interval, 2.07-3.31) for survival to hospital discharge and 2.73 (95% confidence interval, 2.17-3.44) for discharge with favorable functional outcome. The benefit of bystander shock increased progressively as emergency medical services response time became longer.

CONCLUSIONS

Bystander automated external defibrillator use before emergency medical services arrival in shockable observed public OHCA was associated with better survival and functional outcomes. Continued emphasis on public automated external defibrillator utilization programs may further improve outcomes of OHCA.

Post-resuscitation arterial oxygen and carbon dioxide and outcomes after out-of-hospital cardiac arrest

OBJECTIVE

To determine if arterial oxygen and carbon dioxide abnormalities in the first 24h after return of spontaneous circulation (ROSC) are associated with increased mortality in adult out-of-hospital cardiac arrest (OHCA).

METHODS

We used data from the Resuscitation Outcomes Consortium (ROC), including adult OHCA with sustained ROSC ≥1h after Emergency Department arrival and at least one arterial blood gas (ABG) measurement. Among ABGs measured during the first 24h of hospitalization, we identified the presence of hyperoxemia (PaO2≥300mmHg), hypoxemia (PaO2<60mmHg), hypercarbia (PaCO2>50mmHg) and hypocarbia (PaCO2<30mmHg). We evaluated the associations between oxygen and carbon dioxide abnormalities and hospital mortality, adjusting for confounders.

RESULTS

Among 9186 OHCA included in the analysis, hospital mortality was 67.3%. Hyperoxemia, hypoxemia, hypercarbia, and hypocarbia occurred in 26.5%, 19.0%, 51.0% and 30.6%, respectively. Initial hyperoxemia only was not associated with hospital mortality (adjusted OR 1.10; 95% CI: 0.97-1.26). However, final and any hyperoxemia (1.25; 1.11-1.41) were associated with increased hospital mortality. Initial (1.58; 1.30-1.92), final (3.06; 2.42-3.86) and any (1.76; 1.54-2.02) hypoxemia (PaO2<60mmHg) were associated with increased hospital mortality. Initial (1.89; 1.70-2.10); final (2.57; 2.18-3.04) and any (1.85; 1.67-2.05) hypercarbia (PaCO2>50mmHg) were associated with increased hospital mortality. Initial (1.13; 0.90-1.41), final (1.19; 1.04-1.37) and any (1.01; 0.91-1.12) hypocarbia (PaCO2<30mmHg) were not associated with hospital mortality.

CONCLUSIONS

In the first 24h after ROSC, abnormal post-arrest oxygen and carbon dioxide tensions are associated with increased out of-hospital cardiac arrest mortality.

Post-discharge outcomes after resuscitation from out-of-hospital cardiac arrest: A ROC PRIMED substudy

IMPORTANCE

Assessment of morbidity is an important component of evaluating interventions for patients with out-of-hospital cardiac arrest (OHCA).

OBJECTIVE

We evaluated among survivors of OHCA cognition, functional status, health-related quality of life and depression as functions of patient and emergency medical services (EMS) factors.

DESIGN

Prospective cohort sub-study of a randomized trial.

SETTING

The parent trial studied two comparisons in persons with non-traumatic OHCA treated by EMS personnel participating in the Resuscitation Outcomes Consortium.

PARTICIPANTS

Consenting survivors to discharge.

MAIN OUTCOME MEASURES

Telephone assessments up to 6 months after discharge included neurologic function (modified Rankin score, MRS), cognitive impairment (Adult Lifestyle and Function Mini Mental Status Examination, ALFI-MMSE), health-related quality of life (Health Utilities Index Mark 3, HUI3) and depression (Telephone Geriatric Depression Scale, T-GDS).

RESULTS

Of 15,794 patients enrolled in the parent trial, 729 (56% of survivors) consented. About 644 respondents (88% of consented) completed ≥ 1 assessment. Likelihood of assessment was associated with baseline characteristics and study site. Most respondents had MRS ≤ 3 (82.7%), no cognitive impairment (82.7% ALFI-MMSE ≥ 17), no severe impairment in health (71.6%, HUI3 ≥ 0.7) and no depression (90.1% T-GDS≤10). Outcomes did not differ by trial intervention or time from hospital discharge.

CONCLUSIONS AND RELEVANCE

The majority of patients in this large cohort who survived cardiac arrest and were interviewed had no, mild or moderate health impairment. Concern about poor quality of life is not a valid reason to abandon efforts to improve an EMS system's response to cardiac arrest.

International variation in policies and practices related to informed consent in acute cardiovascular research: Results from a 44 country survey

BACKGROUND

Research in an emergency setting such as that with an acute cardiovascular event is challenging because the window of opportunity to treat may be short and may preclude time to obtain informed consent from the patient or their representative. Some perceive that requiring informed consent in emergency situations has limited improvements in care. Vulnerable populations including minorities or residents of low-income countries are at greatest risk of need for resuscitation. Lack of enrollment of such patients would increase uncertainties in treatment benefit or harm in those at greater risk of need for resuscitation. We sought to assess international variation in policies and procedures related to exception from informed consent (EFIC) or deferred consent for emergency research.

METHODS

A brief survey instrument was developed and modified by consensus among the investigators. Included were multiple choice and open-ended responses. The survey included an illustrative example of a hypothetical randomized study. Elicited information included the possibility of conducting such a study in the respondent's country, as well as approvals required to conduct the study. The population of interest was emergency physicians or other practitioners of acute cardiovascular event research.

RESULTS

Usable responses were obtained from 44 countries (76% of surveyed). Community opposition to EFIC was noted in 6 (14%) countries. Emergency Medical Services (EMS) providers in 8 (20%) countries were judged unable or unwilling to participate. A majority of countries (36, 82%) required approval by a Research Ethics Committee or similar. Government approval was required in 25 (57%) countries.

CONCLUSION

There is international variation in practices and policies related to consent for emergency research. There is an ongoing need to converge regulations based on the usefulness of multinational emergency research to benefit both affluent and disadvantaged populations.

Resuscitation Outcomes Consortium-Amiodarone, Lidocaine or Placebo Study (ROC-ALPS): Rationale and methodology behind an out-of-hospital cardiac arrest antiarrhythmic drug trial

BACKGROUND

Despite their wide use, whether antiarrhythmic drugs improve survival after out-of-hospital cardiac arrest (OHCA) is not known. The ROC-ALPS is evaluating the effectiveness of these drugs for OHCA due to shock-refractory ventricular fibrillation or pulseless ventricular tachycardia (VF/VT).

METHODS

ALPS will randomize 3,000 adults across North America with nontraumatic OHCA, persistent or recurring VF/VT after ≥1 shock, and established vascular access to receive up to 450 mg amiodarone, 180 mg lidocaine, or placebo in the field using a double-blind protocol, along with standard resuscitation measures. The designated target population is all eligible randomized recipients of any dose of ALPS drug whose initial OHCA rhythm was VF/VT. A safety analysis includes all randomized patients regardless of their eligibility, initial arrhythmia, or actual receipt of ALPS drug. The primary outcome of ALPS is survival to hospital discharge; a secondary outcome is functional survival at discharge assessed as a modified Rankin Scale score ≤3.

RESULTS

The principal aim of ALPS is to determine if survival is improved by amiodarone compared with placebo; secondary aim is to determine if survival is improved by lidocaine vs placebo and/or by amiodarone vs lidocaine. Prioritizing comparisons in this manner acknowledges where differences in outcome are most expected based on existing knowledge. Each aim also represents a clinically relevant comparison between treatments that is worth investigating.

CONCLUSIONS

Results from ALPS will provide important information about the choice and value of antiarrhythmic therapies for VF/VT arrest with direct implications for resuscitation guidelines and clinical practice.

The impedance threshold device (ITD-7)--a new device for combat casualty care to augment circulation and blood pressure in hypotensive spontaneously breathing warfighters

Inspiration through -7cm H2O resistance results in an increase in venous blood flow back to the heart and a subsequent increase in cardiac output and blood pressure in hypotensive animals and patients. Breathing through the impedance threshold device with 7cm H2O resistance (ITD-7) also reduces intracranial pressure with each inspiration, thereby providing greater blood flow to the brain. A new device called an ITD-7 was developed to exploit these physiological mechanisms to buy time in hypotensive War Fighters when other therapies are not readily available. Animal and clinical data with the ITD-7 demonstrate the potential value and limitations of this new non-invasive approach to enhancing circulation.

Resuscitation Outcomes Consortium (ROC) PRIMED cardiac arrest trial methods part 2: rationale and methodology for "Analyze Later vs. Analyze Early" protocol

OBJECTIVE

The primary objective of the trial is to compare survival to hospital discharge with modified Rankin score (MRS) < or =3 between a strategy that prioritizes a specified period of CPR before rhythm analysis (Analyze Later) versus a strategy of minimal CPR followed by early rhythm analysis (Analyze Early) in patients with out-of-hospital cardiac arrest.

METHODS

Design-Cluster randomized trial with cluster units defined by geographic region, or monitor/defibrillator machine. Population-Adults treated by emergency medical service (EMS) providers for non-traumatic out-of-hospital cardiac arrest not witnessed by EMS. Setting-EMS systems participating in the Resuscitation Outcomes Consortium and agreeing to cluster randomization to the Analyze Later versus Analyze Early intervention in a crossover fashion. Sample size-Based on a two-sided significance level of 0.05, a maximum of 13,239 evaluable patients will allow statistical power of 0.996 to detect a hypothesized improvement in the probability of survival to discharge with MRS < or =3 rate from 5.41% after Analyze Early to 7.45% after Analyze Later (2.04% absolute increase in primary outcome).

CONCLUSION

If this trial demonstrates a significant improvement in survival with a strategy of Analyze Later, it is estimated that 4000 premature deaths from cardiac arrest would be averted annually in North America alone.

Acute management of sudden cardiac death in adults based upon the new CPR guidelines

PURPOSE OF THE REVIEW

The aim of this article is to provide a comprehensive description of interventions that can improve outcomes in adults with sudden cardiac death. The new American Heart Association 2005 Guidelines introduced a number of changes for the initial management of cardiorespiratory arrest based on new data that accumulated over the last 5 years.

ACUTE MANAGEMENT OF SUDDEN CARDIAC DEATH

Appropriate interventions targeting the three phases of cardiopulmonary resuscitation (CPR) (electrical, circulatory, and metabolic) should be implemented. Early defibrillation in early witnessed arrest with one shock is very effective and can improve survival outcomes. When resuscitation efforts are delayed and CPR is performed by paramedics, 2 min of CPR before shock is recommended. Emphasis has been placed on fast and forceful continuous compressions with minimal interruptions, adequate decompression, and decrease in the rate of ventilations to 8-10/min for intubated patients with two rescuers and a universal increase in compression to ventilation ratio to 30:2 for lone rescuers. Mechanical adjuncts to improve circulation have been adapted in the recommendations. The inspiratory impedance threshold device that enhances negative intrathoracic pressure and improves venous preload has been recommended for application in intubated and bag-mask ventilated patients. Owing to the difficulty of endotracheal intubation, airway management devices (Combitube and Laryngeal Mask Airway) can be used as alternatives with minimal extra training.

CONCLUSION

The new guidelines for CPR have focused on early defibrillation, uninterrupted compressions, complete decompression, fewer ventilations, and simplification and uniformity of the process.

Community Lay Rescuer Automated External Defibrillation Programs

Cardiovascular disease is a leading cause of death for adults ≥40 years of age. The American Heart Association (AHA) estimates that sudden cardiac arrest is responsible for about 250 000 out-of-hospital deaths annually in the United States. Since the early 1990s, the AHA has called for innovative approaches to reduce time to cardiopulmonary resuscitation (CPR) and defibrillation and improve survival from sudden cardiac arrest. In the mid-1990s, the AHA launched a public health initiative to promote early CPR and early use of automated external defibrillators (AEDs) by trained lay responders in community (lay rescuer) AED programs. Between 1995 and 2000, all 50 states passed laws and regulations concerning lay rescuer AED programs. In addition, the Cardiac Arrest Survival Act (CASA, Public Law 106-505) was passed and signed into federal law in 2000. The variations in state and federal legislation and regulations have complicated efforts to promote lay rescuer AED programs and in some cases have created impediments to such programs. Since 2000, most states have reexamined lay rescuer AED statutes, and many have passed legislation to remove impediments and encourage the development of lay rescuer AED programs. The purpose of this statement is to help policymakers develop new legislation or revise existing legislation to remove barriers to effective community lay rescuer AED programs. Important areas that should be considered in state legislation and regulations are highlighted, and sample legislation sections are included. Potential sources of controversy and the rationale for proposed legislative components are noted. This statement will not address legislation to support home AED programs. Such recommendations may be made after the conclusion of a large study of home AED use.

Added value of new acute coronary syndrome computer algorithm for interpretation of prehospital electrocardiograms

A new computerized acute coronary syndrome (ACS) computer algorithm has been developed with the aim of improving the electrocardiographic detection of acute myocardial ischemia and infarction in the emergency department (ED). The purpose of this study was to determine the added value of the new ACS algorithm in assisting ED physicians to obtain a more accurate diagnosis in patients with ACS. The new algorithm combines a rule-based decision tree, which uses well-known clinical criteria and a data-centered neural network model for more robust pattern recognition. Input parameters of the neural network model consist of morphology features of derived Frank X, Y, Z waveforms and the patient's gender and age. The neural network model was trained with electrocardiograms obtained from documented acute myocardial infarction patients at the Mayo Clinic who were a part of a research ACS database, which includes electrocardiograms (ECGs) of more than 5,000 individuals at hospital admission (1st ECG in the ED). The test set portion of the study was conducted in 2 steps: 1) One emergency physician and 1 cardiologist classified 1,902 clinically correlated out-of-hospital ECGs without seeing the interpretation statement from the algorithm into 1 of the following categories: 1) acute myocardial infarction, acute ischemia, or nonischemic; 2) After 9 months, the same 2 physicians classified the same group of ECGs but with the interpretation statement of the algorithm printed on the tracing. The results demonstrated that with the assistance of the new algorithm, the emergency physician and cardiologist improved their sensitivity of interpreting acute myocardial infarction by 50% and 26%, respectively, without a loss of specificity. The new algorithm also improved the emergency physician's acute ischemia interpretation sensitivity by 53% and still maintained a reasonable specificity (91%). The new ACS algorithm provides added value for improving acute ischemia and infarction detection in the ED.

A new method to incorporate age and gender into the criteria for the detection of acute inferior myocardial infarction

Recent studies have shown that younger women are more likely to die during and after hospitalization for acute myocardial infarction (MI) than older women and men of all ages. This may be partly due to incorrect diagnosis or late detection of acute MI in younger women. At high specificity levels (>98%), the sensitivity of the initial ECG to detect acute MI may be as low as 30% when using traditional criteria by both physicians and computerized interpretation programs. This study examines if women of different age groups have a similar ECG presentation to men during acute inferior MI and if the diagnostic accuracies of the initial ECG are comparable. We analyzed chest pain ECGs from Mayo Clinic and Medical College of Wisconsin, which included 1,339 patients with acute inferior MI and 1,169 age-matched controls with noncardiac chest pain. We subdivided all groups by age (below and above 60 years) and compared ECG parameters (ST elevation, ST depression, QRS duration, R-wave amplitude, Q-wave duration and amplitude, QT interval) between genders. For inferior MI patients under age 60, women had lower ST elevations at the J point in lead II than men (57 +/- 91 microV vs. 86 +/- 117 microV, P < .02). This trend was reversed for patients over age 60 (lead a VF: 102 +/- 126 microV vs. 84+/-117 microV, P < .04; Lead III: 130+/-146 microV vs. 103+/-131 microV, P < .007). A neural network method was used to identify the most significant group of ECG parameters for detecting acute MI. An adaptive fuzzy logic method was developed for adapting to the threshold differences among the different gender and age groups. The new algorithm improved the sensitivity of acute inferior MI detection by more than 25% relative to old algorithm, while maintaining the high specificity around 98% for noncardiac chest pain patients.

Use of an inspiratory impedance valve improves neurologically intact survival in a porcine model of ventricular fibrillation

BACKGROUND

This study evaluated the potential for an inspiratory impedance threshold valve (ITV) to improve 24-hour survival and neurological function in a pig model of cardiac arrest.

METHODS AND RESULTS

Using a randomized, prospective, and blinded design, we compared the effects of a sham versus active ITV on 24-hour survival and neurological function. After 6 minutes of ventricular fibrillation (VF), followed by 6 minutes of cardiopulmonary resuscitation (CPR) with either a sham or an active valve, anesthetized pigs received 3 sequential 200-J shocks. If VF persisted, they received epinephrine (0.045 mg/kg), 90 seconds of CPR, and 3 more 200-J shocks. A total of 11 of 20 pigs (55%) in the sham versus 17 of 20 (85%) in the active valve group survived for 24 hours (P<0.05). Neurological scores were significantly higher with the active valve; the cerebral performance score (1=normal, 5=brain death) was 2.2+/-0.2 with the sham ITV versus 1.4+/-0.2 with the active valve (P<0.05). A total of 1 of 11 in the sham versus 12 of 17 in the active valve group had completely normal neurological function (P<0.05). Peak end-tidal CO2 (PETCO2) values were significantly higher with the active valve (20.4+/-1.0) than the sham (16.8+/-1.5) (P<0.05). PETCO2 >18 mm Hg correlated with increased survival (P<0.05).

CONCLUSIONS

Use of a functional ITV during standard CPR significantly improved 24-hour survival rates and neurological recovery. PETCO2 and systolic blood pressure were also significantly higher in the active valve group. These data support further evaluation of ITV during standard CPR.

Utilization of cardiopulmonary resuscitation in nursing homes in one community: rates and nursing home characteristics

OBJECTIVE

To determine the rate of cardiopulmonary resuscitation use among all nursing homes in a large urban area, to examine CPR use over time, to discover whether CPR use varies among nursing homes, and to describe characteristics of patients undergoing CPR.

DESIGN

Retrospective survey.

SETTING

Nursing homes in a large urban area.

PARTICIPANTS

One hundred ninety-six nursing home residents of 68 nursing homes underwent cardiopulmonary resuscitation over a 4-year period (1986-1989). Over this time there were 9,486 deaths in these homes, which comprised 10,252 beds.

MEASUREMENTS

The CPR:death ratio was determined for each facility. The ratio was analyzed over time and by type of facility (eg, proprietary, non-profit, size of facility). The ratio was also examined among facilities with variable death rates. Patients undergoing CPR are described.

RESULTS

The ratio of CPR:death over the 4-year period was 0.02. CPR:death ratio was higher (0.03) for the proprietary homes compared with the non-profit homes (0.01) P < 0.0001. A significant downward trend of CPR:death was noted over the study period for the non-profit homes; no such trend was noted in the proprietary homes. Size of nursing home did not influence the rate of CPR use. Homes with greater numbers of deaths per bed had a lower utilization of CPR. Patients undergoing CPR were old, frail, and had multiple medical problems. CPR attempts were frequent around the time of nursing home admission.

CONCLUSION

The utilization of CPR in nursing homes is quite low. Non-profit homes utilize CPR less than proprietary homes. Nursing homes with the highest numbers of deaths per bed utilize CPR less than homes with lower numbers of deaths per bed. Nursing home residents receiving CPR are quite old, have multiple illnesses, and are impaired.

Time delays in the diagnosis and treatment of acute myocardial infarction: a tale of eight cities. Report from the Pre-hospital Study Group and the Cincinnati Heart Project

To establish the magnitude of prehospital and hospital delays in initiating thrombolytic therapy for acute myocardial infarction, the time from telephone 911 emergency medical system (EMS) activation to treatment and its components were analyzed from eight separate ongoing trials. This included estimates of ambulance response time, prehospital evaluation and treatment time, and time from admission to the hospital to initiation of thrombolytic therapy. The average time from EMS activation to patient arrival at the hospital was prospectively determined to be 46.1 +/- 8.2 minutes in 3715 patients from eight centers. The time from admission to the hospital to initiation of thrombolytic therapy was retrospectively determined to be 83.8 +/- 55.0 minutes in a separate group of 730 patients from six centers. Both the prehospital and hospital time delays were much longer than those perceived by paramedics and emergency department directors. Shorter hospital time delays were observed in patients in whom a prehospital ECG was obtained as part of a protocol-driven prehospital diagnostic strategy and a diagnosis of acute infarction made before arrival at the hospital (36.3 +/- 11.3 minutes in 13 patients). These results show that the magnitude of time required to evaluate, transport, and initiate thrombolytic therapy will preclude initiation of treatment to most patients within the first hour of symptoms. Implementation of a protocol-driven prehospital diagnostic strategy may be associated with a reduction in time to thrombolytic therapy.

Electromechanical dissociation: six years prehospital experience

Electromechanical dissociation (EMD) is the presenting rhythm in approximately 17% of all prehospital cardiorespiratory arrests. Yet, we know comparatively little about the demographic profile of these patients. The purpose of this study was to review historical and resuscitative parameters to help create a demographic profile. For a 6-year period of time from January 1st, 1980 to December 31st, 1985, 503 adult patients presented to a prehospital system in non-traumatic, nonpoisoned, cardiorespiratory arrest with an initial rhythm of electromechanical dissociation. The overall average response time was 6.1 +/- 3.2 min. Sixty percent of the patients were witnessed arrests and 65% had bystander initiated CPR. Forty-six percent of the patients had a cardiac history: myocardial infarction 13%, CHF 11% and other 21%. Other pertinent past medical history included diabetes 15%, COPD 10% and seizures 3%. The average age was 69.8 +/- 13.7 years. Fifty-seven percent were male. Forty-three percent were on cardiac medication including: digoxin, 24%; nitroglycerin, 12%; potassium supplements, 9%; propranolol, 8%; isordil, 6%; quinidine, 3%; nitropaste, 3%; and other cardiac medications, 15%. One hundred forty-eight (29%) patients developed a pulse at some time during resuscitative efforts, of these 17 (3.4%) patients responded with a pulse immediately after intubation. The mean time of resuscitation to sustaining pulse was 20 +/- 11 min and the mean resuscitation time to sustaining pressure was 22 +/- 11 min. Nineteen percent were successfully resuscitated, defined as a conveyance of a patient with a pulse and a rhythm to an emergency department. Four point four percent were saved, defined as a patient discharged alive from the hospital. Approximately 53% of the successfully resuscitated patients and 45% of the save patients were determined to have a probable respiratory event as the primary etiology of their arrest. This study attempts to provide some insight into the demographic profile of the patients in EMD.

Defining electromechanical dissociation: morphologic presentation

Electromechanical dissociation (EMD) is inconsistently defined in the literature. Our definition is the presence of discernible electrical complexes (excluding ventricular tachycardia and ventricular fibrillation) and the absence of palpable pulses. It has been noted that EMD may present with a variety of morphological complexes. It was the purpose of this study to categorize the electrical morphologic characteristics of patients presenting in EMD and to correlate morphology with patient outcome and response to therapy. From the 6-year period, January 1st, 1980 to December 31st, 1985, 503 evaluable adult patients presented to an urban paramedic system in non-traumatic, non-poisoned, cardiorespiratory arrest and were determined to be in EMD. The rhythm strips obtained from paramedics on all patients were retrospectively reviewed and were arbitrarily categorized in the following manner: Group 1, normal QRS width, isoelectric ST and normal appearing T-waves; Group 2A, atrial activity, widened QRS width (greater than or equal to 0.12 ms) or abnormal ST and/or T-waves (ST depression, elevation, slurring or T-wave inversion); Group 2B, same as Group 2A but without atrial activity; Group 3, essentially monophasic, slurred RST complexes. The respective initial distribution was Group 1, 147 (29%); Group 2A, 248 (49%); Group 2B, 60 (12%); Group 3, 48 (10%). The relative frequency of morphologies preceding the attainment of a pulse was as follows: Group 1, 30 (24%); Group 2A, 82 (65%); Group 2B, 8 (6%); Group 3, 6 (5%) (P less than or equal to 0.01 with no significant difference between Group 2B and 3).(ABSTRACT TRUNCATED AT 250 WORDS)

Interventions in the therapy of electromechanical dissociation

Electromechanical dissociation (EMD) is a major arrest rhythm for which there is often inadequate treatment. The purpose of this study was to evaluate the different pharmacological and non-pharmacological interventions considered in the treatment of EMD. During the 6-year period, January 1st, 1980 to December 31st, 1985, 503 evaluable adult patients presented in a non-traumatic, non-poisoning cardiopulmonary arrest with the initial rhythm of EMD. One hundred nineteen patients obtained a pulse during resuscitation efforts following drug administration. The average time to obtaining pulses after the last drug administration was 1.97 +/- 2.21 min. The following drugs were last administered prior to transient pulses: bicarbonate, 31/119 (26%); epinephrine, 26/119 (22%); atropine, 26/119 (22%); dopamine, 13/119 (11%); calcium, 11/119 (9%); isoproterenol, 7/119 (6%); other drugs, 5/119 (4%). Ninety-five percent of the successful resuscitations received eight or less drug interventions and all saves received three or less drug interventions. Two hundred twenty-four patients (44.5%) had 288 non-pharmacological interventions. Twenty-three patients developed a pulse after intervention in the following distribution: MAST suit (N = 9), pericardiocentesis (N = 6), fluid challenge (N = 5), needle thoracostomy (N = 1), and intervention combinations (N = 2). The time interval between intervention and the onset of pulse was as follows: MAST suit, 4 +/- 2.8 min; pericardiocentesis, 3.7 +/- 3.6 min; fluid challenge, 4.8 +/- 4.1 min; needle thoracostomy, 6 min. The overall save rate for intervention patients was 0.9% whereas for those not having intervention it was 7.2% (P less than or equal to 0.0003).(ABSTRACT TRUNCATED AT 250 WORDS)

Use of carbon monoxide to measure luminal stirring in the rat gut

We used carbon monoxide (CO) as a probe to quantitatively measure intestinal unstirred water layers in vivo. CO has several features that make it uniquely well suited to measure the unstirred layer in that its tight binding to hemoglobin makes uptake diffusion limited, and its relatively high lipid solubility renders membrane resistance negligible relative to the water barriers of the unstirred layer and epithelial cell. The unique application of CO was the measurement of the absorption rate of CO both from the gas phase as well as a solute dissolved in saline. Several lines of evidence showed that a gut stripped free of saline and then filled with gas contained a negligible unstirred layer. Thus, absorption of CO from the gas phase measured resistance of just the epithelial cell. Subtraction of this value from the resistance of CO absorption from saline provided a direct measure of unstirred layer resistance. Studies in the rat showed for a 3-min absorption period that the conventionally calculated apparent unstirred layer for the jejunum was 411 micron and for the colon was 240 micron. However, this conventionally calculated unstirred layer resistance did not truly depict the situation in the rat gut, since there was a continuing depletion of CO from outer surfaces of luminal contents throughout the experiment period. This produced a continually increasing diffusion barrier with time. Calculation of expected absorption rate from unstirred cylinders with the dimensions of the rat gut indicated that there was virtually no stirring in the small intestine and minimal stirring in the colon. The technique described in this paper appears to be simpler and to require fewer assumptions for validity than other techniques previously used to measure unstirred layers in vivo.