Mary Pat Larsen

Predicting survival from out-of-hospital cardiac arrest: A graphic model

STUDY OBJECTIVE To develop a graphic model that describes survival from sudden out-of-hospital cardiac arrest as a function of time intervals to critical prehospital interventions. PARTICIPANTS From a cardiac arrest surveillance system in place since 1976 in King County, Washington, we selected 1,667 cardiac arrest patients with a high likelihood of survival: they had underlying heart disease, were in ventricular fibrillation, and had arrested before arrival of emergency medical services (EMS) personnel. METHODS For each patient, we obtained the time intervals from collapse to CPR, to first defibrillatory shock, and to initiation of advanced cardiac life support (ACLS). RESULTS A multiple linear regression model fitting the data gave the following equation: survival rate = 67%-2.3% per minute to CPR-1.1% per minute to defibrillation-2.1% per minute to ACLS, which was significant at P < .001. The first term, 67%, represents the survival rate if all three interventions were to occur immediately on collapse. Without treatment (CPR, defibrillatory shock, or definitive care), the decline in survival rate is the sum of the three coefficients, or 5.5% per minute. Survival rates predicted by the model for given EMS response times approximated published observed rates for EMS systems in which paramedics respond with or without emergency medical technicians. CONCLUSION The model is useful in planning community EMS programs, comparing EMS systems, and showing how different arrival times within a system affect survival rate.

Incidence of agonal respirations in sudden cardiac arrest

STUDY OBJECTIVE To discover the frequency of agonal respirations in cardiac arrest calls, the ways callers describe them, and discharge rates associated with agonal respirations. DESIGN We reviewed taped recordings of calls reporting cardiac arrests and emergency medical technician and paramedic incident reports for 1991. Arrests after arrival of emergency medical services were excluded. SETTING King County, Washington, excluding the city of Seattle. PARTICIPANTS Four hundred forty-five persons with out-of-hospital cardiac arrests receiving emergency medical services. INTERVENTIONS Telephone CPR, emergency medical technicians-defibrillation, and advanced life support by paramedics. MEASUREMENTS AND MAIN RESULTS Any attempts at breathing described by callers were identified, as well as whether agonal respirations could be heard by dispatcher, emergency medical technicians, or paramedics. Agonal respirations occurred in 40% of 445 out-of-hospital cardiac arrests. Callers described agonal breathing in a variety of ways. Agonal respirations were present in 46% of arrests caused by cardiac etiology compared with 32% in other etiologies (P < .01). Fifty-five percent of witnessed arrests had agonal activity compared with 16% of unwitnessed arrests (P < .001). Agonal respirations occurred in 56% of arrests with a rhythm of ventricular fibrillation compared with 34% of cases with a nonventricular fibrillation rhythm (P < .001). Twenty-seven percent of patients with agonal respirations were discharged alive compared with 9% without them (P < .001). CONCLUSION There is a high incidence of agonal activity associated with out-of-hospital cardiac arrest. Presence of agonal respirations is associated with increased survival. These findings have implications for public CPR training programs and emergency dispatcher telephone CPR programs.

REASONS PATIENTS WITH CHEST PAIN DELAY OR DO NOT CALL 911

STUDY OBJECTIVE To determine the reasons patients with suspected acute myocardial infarction (AMI) delay seeking medical care or do not call 911. DESIGN Telephone interview of patients hospitalized with suspected AMI. SETTING Nine hospitals in King County, Washington. PARTICIPANTS Patients admitted to a CCU or ICU between October 1, 1986, and December 31, 1987, with suspected AMI occurring out-of-hospital. Spouses of patients who met criteria but died during the hospitalization also participated. INTERVENTIONS Hospital records were reviewed, and a 20-minute telephone interview was conducted of patients who reside in King County but do not live in an extended care facility. MEASUREMENTS Patient demographics, cardiac history, symptoms, time of acute symptom onset, time of emergency department arrival, method of transportation, discharge diagnosis, and hospital outcome were abstracted from hospital records. Circumstances leading to the hospitalization, reasons for delay in seeking care, and reasons for not calling 911 were determined in the telephone interview. RESULTS In a 15-month period, 5,207 patients were hospitalized for suspected AMI in King County, Washington. Twenty-seven percent had AMI. Median patient delay between symptom onset and hospital arrival was 2 hours. Paramedics transported 45% of all patients. A representative subset of patients (2,316) were interviewed. The main reasons for delay were because the patient thought that the symptoms would go away, because the symptoms were not severe enough, and because the patient thought that the symptoms were caused by another illness. The main reasons for not calling 911 were because the symptoms were not severe enough, because the patient did not think of calling 911, and because the patient thought that self-transport would be faster because of his or her close location to the hospital. CONCLUSION Maximal benefit from thrombolytic therapy is not realized in a substantial proportion of patients with AMI because of delays in seeking medical care. Knowledge of the reasons patients delay or do not call 911 can help focus efforts on achieving more rapid treatment of patients with AMI.

Survival rates from out-of-hospital cardiac arrest: Recommendations for uniform definitions and data to report

Survival rates for out-of-hospital cardiac arrest vary widely among locations. We surveyed the definitions used in published studies of out-of-hospital cardiac arrest. Data from 74 studies involving 36 communities showed survival rates ranging from 2% to 44%. There were five different case definitions and 11 different definitions of survivors. The absence of uniform definitions prevents meaningful intersystem comparisons, prohibits explorations of hypotheses about effective interventions, and interferes with the efforts of quality assurance. The most satisfactory numerator for a survival rate appears to be survival to hospital discharge; the most appropriate denominator appears to be witnessed adult cardiac arrest of presumed heart disease etiology, with ventricular fibrillation as the initial identified rhythm. Proposed definitions for the data emergency medical services systems should report as they examine their cardiac arrest survival rates are presented.

Out-of-Hospital Transcutaneous Pacing by Emergency Medical Technicians in Patients with Asystolic Cardiac Arrest

BACKGROUND Transcutaneous cardiac pacemakers generate electrical stimuli that pace the heart through external electrodes that adhere to the chest wall. Transcutaneous pacing has been useful in some patients with bradycardia, but its efficacy in patients with asystole and full cardiac arrest has been limited, possibly because of delays in the initiation of pacing. We studied the efficacy of early transcutaneous pacing in patients with out-of-hospital asystolic cardiac arrest. METHODS For three years we provided transcutaneous pacemakers to about half the fire districts in a large emergency-medical-services system (the intervention group). In these districts, we authorized emergency medical technicians (EMTs) to begin transcutaneous pacing in patients with cardiac arrest and primary asystole or post-defibrillation asystole. Pacing was done as early as possible, before endotracheal intubation or intravenous medication. EMTs in the other fire districts (the control group) treated similar patients with basic cardiopulmonary resuscitation but without transcutaneous pacing. RESULTS The EMTs in the intervention group initiated transcutaneous pacing in 112 of the 278 patients with primary asystole. Of these patients, 22 (8 percent) were admitted to the hospital, and 11 (4 percent) were discharged. Among the 259 patients treated by the EMTs in the control group, 21 (8 percent) were admitted to the hospital, and 5 (2 percent) were discharged. The two groups did not differ significantly with respect to the rate of hospital admission or survival. Survival after early pacing for post-defibrillation asystole was no better than survival after pacing for primary asystole. CONCLUSIONS Transcutaneous pacing appears to offer no benefit in patients with asystolic cardiac arrest, even when it is performed as early as possible by EMTs in the field. Our data suggest that the widespread implementation of early transcutaneous pacing for out-of-hospital asystolic cardiac arrest would be ineffective.

Numerators, denominators, and survival rates: Reporting survival from out-of-hospital cardiac arrest

This study demonstrates the effect of different denominators on the survival rate from out-of-hospital cardiac arrest. We retrospectively analyzed data from a cardiac arrest surveillance system in King County, Washington during the years 1976 to 1988, and calculated survival rates using eight different definitions of denominators. The eight survival rates ranged from 16% to 49% discharge from hospital. The denominator for the lowest survival rate included all cases of cardiac arrest for whom emergency medical services personnel started cardiopulmonary resuscitation. The denominator for the highest survival rate included: all cases of presumed cardiac etiology; first recorded rhythm was ventricular fibrillation; collapse witnessed; cardiopulmonary resuscitation started by bystanders within 4 minutes; and definitive care provided within 8 minutes. The definition of cases included in the denominator can dramatically effect the resultant survival rate. There must be national and international agreement about definitions of denominators for valid cross community comparisons.

'Call fast, Call 911': a direct mail campaign to reduce patient delay in acute myocardial infarction.

OBJECTIVES A 10-month direct mail campaign was implemented to increase use of emergency medical services via 911 calls and to reduce prehospital delay for individuals experiencing acute myocardial infarction symptoms. METHODS This prospective, randomized, controlled trial involved three intervention groups (receiving brochures with informational, emotional, or social messages) and a control group. RESULTS Intervention effects were not observed except for individuals who had a history of acute myocardial infarction and who were discharged with a diagnosis of acute myocardial infarction; their 911 use was meaningfully higher in each intervention group than in the control group. CONCLUSIONS The mailings affected only the individuals at greatest risk.

The epidemiology of cardiac arrest in young adults

STUDY OBJECTIVE To describe the epidemiology of cardiac arrest in young adults and to determine if there are characteristics unique to this group in terms of etiology, rhythm, and outcome. DESIGN Retrospective, case review. SETTING King County, Washington. TYPE OF PARTICIPANTS All out-of-hospital victims of cardiac arrest who received emergency aid. MEASUREMENTS The etiology, cardiac rhythm, and outcome were identified for each case. MAIN RESULTS During the 13-year period from 1976 to 1989, there were 8,054 cardiac arrests; 252 of these were among young adults 18 to 35 years of age. Of those 252 cases, 61 (24%) were caused by ischemic heart disease, and 60 (24%) were caused by overdose. Asystole was the most common rhythm (48%), followed by ventricular fibrillation or tachycardia (31%). Long-term survival following these rhythms was 4% and 28%, respectively. In terms of age, etiology, and rhythm, young adults appear to represent a transitional group between children and older adults. There were no unique characteristics specific to young adults. Long-term survival is dependent more on rhythm than on age. CONCLUSION In terms of age, etiology, and rhythm, young adults appear to represent a transitional group between children and older adults.

Expected death and unwanted resuscitation in the prehospital setting

STUDY OBJECTIVE To determine the outcome, location, preexisting conditions, and resuscitation wishes of prehospital cardiac arrest patients. DESIGN Retrospective review of paramedic and emergency medical technician run reports. SETTING Urban area with a two-tiered emergency medical services response system covering an area of 2,128 square miles and serving a population of 1,413,900 (in 1988). PARTICIPANTS All prehospital cardiac arrest patients to which the King County, Washington, Emergency Medical Services (KCEMS) system responded to during a 12-month period. Unless decapitation, decomposition, or dependent lividity existed, all cardiac arrest patients in the KCEMS system received full resuscitative efforts. MEASUREMENTS We analyzed run reports from 694 cardiac arrest patients, excluding all cardiac arrests from trauma, overdose, or drowning, or obvious signs of extended downtime such as decomposition or dependent lividity. We defined an unwanted resuscitation as a resuscitation attempt despite written or verbal requests by the patient, family, or private physician. We defined a patient as having severe, chronic disease if the run report listed one or more conditions associated with poor survival rates after inpatient CPR. These included cancer, cerebral vascular accident, dementia, renal failure, dialysis, AIDS, thoracic or abdominal aneurysms, cirrhosis, or if the patient was bedridden or was receiving chronic home nursing care. MAIN RESULTS Overall 16% (103 of 633) of all cardiac arrest patients survived to hospital discharge. Seven percent (47 of 633) of all cardiac arrest patients fit the unwanted resuscitation definition; 2% (one of 47) survived to hospital discharge. Twenty-five percent (158 of 633) of cardiac arrest patients fit the definition of severe chronic disease; 8% (12 of 158) survived to hospital discharge. CONCLUSION Severe chronic disease and unwanted resuscitation patients comprised one-third of all resuscitation attempts by KCEMS during a 12-month period. Both groups had lower survival rates compared to cardiac arrest patients who did not have severe chronic disease or indications of unwanted resuscitation.

Incidence of cardiac arrest during self-transport for chest pain.

STUDY OBJECTIVE To assess the incidence of cardiac arrest among patients who use self-transport to seek medical care for chest pain. METHODS This was a retrospective cohort study of patients admitted to a CCU for suspected acute myocardial infarction (AMI) and patients experiencing out-of-hospital cardiac arrest preceded by symptoms in King County, Washington, between January 1, 1992, and July 31, 1994. Participants were identified through use of the databases compiled by the Myocardial infarction Triage and intervention Trial, which reviewed medical records in all area hospitals, and the Cardiac Arrest Surveillance System, which tracks all incidences in which CPR is performed by EMS personnel in King County. Patients whose sudden cardiac arrests were not preceded by symptoms were excluded. Hospital records were abstracted to find the means of transport for patients admitted to CCUs. For cardiac arrest patients, the medical history, presence of symptoms, means of transport, and prehospital death information were abstracted from paramedic field reports. Outcome (admission, discharge, or in-hospital death) was obtained from hospital records. An event cause (cardiac or other) was determined from death certificates, hospital records, or consultation with private physicians. RESULTS During the 30-month study period, 13,187 patients sought help for cardiac symptoms and were either admitted to a CCU or died before admission after calling 911. A majority, 7,393 (59%), were transported by emergency medical services, and 5,182 (41%) used private transportation to obtain medical care; the means of transport could not be determined for 612 patients. Of the EMS group, 6,978 were admitted to the hospital without experiencing prehospital cardiac arrest, and 415 (5.6%) arrested before arriving at the hospital. Of the group using private transportation, 5,164 were admitted without arresting and 18 (.35%) arrested before arrival, after which 911 was called (P < .001). CONCLUSION The incidence of cardiac arrest among patients who attempted to reach the hospital by private transportation was very low compared with the incidence among those who chose the EMS system for transport. This suggests that patient self-selection occurs, with the more seriously ill patients more commonly calling 911 for transport.