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Development and widespread use of automatic external defibrillators
AMERICAN
JOURNAL
OF EMERGENCY
MEDICINE
n Volume
4, Number
varying in population from 5,000 to 57,000, were randomized into two eight-member groups for a two-year cross-over study. Commencing August 1, 1984, eight communities were designated to treat patients with the AEDP while eight communities served as controls. After one year, treatment and control communities were made to cross over. Chest electrodes were used in an anterior/apical position, and initial airway management was standardized using a Seal-EasyR mask. Although this study has not reached completion, eighteen months’ of data have been collected and analyzed: Treatment Group Control Group 75 56 Total patients 69.4 years 68.0 years Mean age 38/l 8 Male/Female 53132 Presenting rhythm 42 (56%) 33 (59%) VF 24 (32%) 16 (29%) Bradyasystale 9 (12%) 7 (12%) PIVR 32 (57%) Witnessed 49 (65%) CPR prior to ambulance arrival 33 (44%) 38 (68%) 6 (11%) 16 (21%) Hospital admissions IT (2%) Discharge survivors 6* (8%) 5142 (12%) 1/33T (3%) Discharge survivors from VF * One survivor in the treatment group was bradycardic, pulseless, and apneic. Pulse and blood pressure returned with assisted ventilation only. t The control group survivor experienced ventricular fibrillation in the ambulance near the hospital and was subsequently defibrillated in the emergency department.
Ambulance response times in the two groups were comparable (less than 8 minutes in 53% of the treatment group and 70% of the control group). Of the 42 patients in VF in the treatment group, 28 experienced a witnessed arrest. All of the survivors of VF in this group had a witnessed arrest. Thus, the rate of survival of patients with a witnessed arrest in VF in the treatment group was 18% (5128). Heart-Aid Model 95R performance was evaluated as well. Sixty-four sequences of ventricular fibrillation were presented to the machine, with 54 receiving a defibrillatory shock (84% sensitivity). On eight occasions (12%), tine ventricular fibrillation was interpreted as asystole and externally paced. One sequence of ventricular fibrillation was properly evaluated but not detibrillated, and one patient’s permanent pacemaker spikes interfered with proper treatment. In no instance of asystole or an organized rhythm was a defibrillatory shock delivered. Sequences of asystole were noted either initially or after countershock on 52 occasions. All were paced, seven (13%) achieved a palpable pulse, but no patients survived. The discharge survival rate of patients with out-of-hospital VF treated with the Heart-Aid Model 95 (AEDP) was 12% in rural Southeastern Minnesota communities. When the arrest in VF was witnessed, the survival rate was 18%. All five survivors of VF in the treatment group had experienced a witnessed arrest. Moderate Fluid Loading with Whole Blood Versus Ringer’s
Solution During CPR in Dogs. William D. Voorhees, III, Sandra H. Ralston. Purdue University, West Lafayette, IN 47907. 424
5 n September
1986
The effect of moderate fluid loading during electrically induced ventricular fibrillation (VF) and CPR in 18 dogs (12-26 kg) was investigated. Oxygen uptake was recorded continuously with a spirometer modified to permit positivepressure ventilation. Blood flows were measured with radioactive microspheres (15 + 0.9 urn diameter) at 5, 13, and 20 min after initiation of VF and CPR. After 10 minutes of CPR, all dogs received a rapid intravenous infusion (10 ml/kg) of either whole blood (n = 9) or Ringer’s solution (n = 9). Differences between the blood- and the Ringer’streated groups were not statistically significant for any of the measured variables. However, the effects of fluid loading on cardiac output (CO), left ventricular (LV) perfusion, and cerebral blood flow were significant. After fluid loading, CO increased 34% (at 13 minutes) then decreased (at 20 minutes) to 84% of the control (5 minutes) value. Despite the increase in CO, LV perfusion fell to 74% of control, while cerebral blood flow decreased to 65% of control after fluid loading. At 20 minutes (10 minutes after fluid loading), CO and cerebral blood flow returned to near control value, while LV perfusion remained low. Oxygen uptake was not significantly affected by fluid loading with either whole blood or Ringer’s. Brain Time CO LV (min) (mllminlkg) (mllminlkg) (ml/min/g) 0.75 t 0.08 5 0.65 ? 0.06 65.8 * 5.0 0.48 2 0.08* 0.49 2 0.06* 13 88.4 2 8.6* 0.51 t 0.08 0.73 t 0.10 20 55.1 * 5.0’ * Indicates statistically significant difference from control (5 < 0.01).
Op Uptake (mllminlkg) 4.18 + 0.29 4.29 + 0.27 4.46 2 0.32 min) value (CK
The changes in organ perfusion can be explained in part by the concurrent changes in blood pressures. Previous studies have shown that the level of central arterial diastolic pressure (CADP) and the central arteriovenous diastolic pressure difference (CAVDP) correlate with vital organ perfusion. In this study, central venous diastolic pressure increased significantly (9.2 to 13.9 mm Hg) after fluid load. However, CADP did not rise proportionately (3 1.9 to 33.9 mm Hg), and the CAVDP actually decreased. Although fluid load during CPR improves CO, flow to the heart and brain decreases. Moreover, there is no increase in oxygen consumption, indicating that fluid loading does not improve metabolic status. Development and Widespread Use of Automatic External Defibrlllators. W. Douglas Weaver, Michael K. Copass, Deborah Hill, Carl Morgan, Robert D. Swenson, Carol Fahrenbruch, Michael D. Emery, Leonard A. Cobb. University of Washington, Seattle, Washington. An automatic external defibrillator (AED) has been used by first responders in our tiered emergency system to treat 408 patients with cardiac arrest and also by three of 43 family members of patients at risk for ventricular fibrillation (VF). The detection algorithm was initially developed from a pre-recorded database but has since been modified based on field observations. The VF detector correctly identified 172 of 196 (88%) of VF database records but only 145 of 275 (53%) VF periods during initial clinical use (P < 0.001). Since modifying the detector, 75 of 83 (90%) VF periods
ABSTRACTS
were correctly identified, a significant improvement over initial performance (P < 0.001). No patient with a rhythm other than VF has been inappropriately shocked. Fortyeight of 171 (28%) patients discovered in VF, two of 158 (1%) in asystole, three of 73 (4%) in EMD, one of six (17%) in ventricular tachycardia have survived. One-quarter of VF patient regained pulse and blood pressure before paramedics arrived. On average, the AED was used 4.8 ? 2.5 minutes, delivered 1.7 -C 0.8 shocks, and effected defibrillation in 68% of 220 shocks. In the layperson experience, two of three patients were resuscitated, and one survived. In all, 51 of 83 (61%) consec-
FROM PERDUE CONFERENCE
ON CPR
utive patients who previously had been resuscitated appear to be candidates for AED. Training of laypersons takes approximately 5 hours, although there is a rapid loss of skills; 93% were judged proficient after class, 72% at one month, and 56% at six months. The instructional sequence and continuing educational material that optimizes performance is not yet clear. Widespread use of AED by first responders is possible and beneficial, algorithm performance can be judged best by field trials, and layperson use is feasible, but there are as yet many undetermined factors that will ultimately define the utility of such an approach.
425
JOURNAL
OF EMERGENCY
MEDICINE
n Volume
4, Number
varying in population from 5,000 to 57,000, were randomized into two eight-member groups for a two-year cross-over study. Commencing August 1, 1984, eight communities were designated to treat patients with the AEDP while eight communities served as controls. After one year, treatment and control communities were made to cross over. Chest electrodes were used in an anterior/apical position, and initial airway management was standardized using a Seal-EasyR mask. Although this study has not reached completion, eighteen months’ of data have been collected and analyzed: Treatment Group Control Group 75 56 Total patients 69.4 years 68.0 years Mean age 38/l 8 Male/Female 53132 Presenting rhythm 42 (56%) 33 (59%) VF 24 (32%) 16 (29%) Bradyasystale 9 (12%) 7 (12%) PIVR 32 (57%) Witnessed 49 (65%) CPR prior to ambulance arrival 33 (44%) 38 (68%) 6 (11%) 16 (21%) Hospital admissions IT (2%) Discharge survivors 6* (8%) 5142 (12%) 1/33T (3%) Discharge survivors from VF * One survivor in the treatment group was bradycardic, pulseless, and apneic. Pulse and blood pressure returned with assisted ventilation only. t The control group survivor experienced ventricular fibrillation in the ambulance near the hospital and was subsequently defibrillated in the emergency department.
Ambulance response times in the two groups were comparable (less than 8 minutes in 53% of the treatment group and 70% of the control group). Of the 42 patients in VF in the treatment group, 28 experienced a witnessed arrest. All of the survivors of VF in this group had a witnessed arrest. Thus, the rate of survival of patients with a witnessed arrest in VF in the treatment group was 18% (5128). Heart-Aid Model 95R performance was evaluated as well. Sixty-four sequences of ventricular fibrillation were presented to the machine, with 54 receiving a defibrillatory shock (84% sensitivity). On eight occasions (12%), tine ventricular fibrillation was interpreted as asystole and externally paced. One sequence of ventricular fibrillation was properly evaluated but not detibrillated, and one patient’s permanent pacemaker spikes interfered with proper treatment. In no instance of asystole or an organized rhythm was a defibrillatory shock delivered. Sequences of asystole were noted either initially or after countershock on 52 occasions. All were paced, seven (13%) achieved a palpable pulse, but no patients survived. The discharge survival rate of patients with out-of-hospital VF treated with the Heart-Aid Model 95 (AEDP) was 12% in rural Southeastern Minnesota communities. When the arrest in VF was witnessed, the survival rate was 18%. All five survivors of VF in the treatment group had experienced a witnessed arrest. Moderate Fluid Loading with Whole Blood Versus Ringer’s
Solution During CPR in Dogs. William D. Voorhees, III, Sandra H. Ralston. Purdue University, West Lafayette, IN 47907. 424
5 n September
1986
The effect of moderate fluid loading during electrically induced ventricular fibrillation (VF) and CPR in 18 dogs (12-26 kg) was investigated. Oxygen uptake was recorded continuously with a spirometer modified to permit positivepressure ventilation. Blood flows were measured with radioactive microspheres (15 + 0.9 urn diameter) at 5, 13, and 20 min after initiation of VF and CPR. After 10 minutes of CPR, all dogs received a rapid intravenous infusion (10 ml/kg) of either whole blood (n = 9) or Ringer’s solution (n = 9). Differences between the blood- and the Ringer’streated groups were not statistically significant for any of the measured variables. However, the effects of fluid loading on cardiac output (CO), left ventricular (LV) perfusion, and cerebral blood flow were significant. After fluid loading, CO increased 34% (at 13 minutes) then decreased (at 20 minutes) to 84% of the control (5 minutes) value. Despite the increase in CO, LV perfusion fell to 74% of control, while cerebral blood flow decreased to 65% of control after fluid loading. At 20 minutes (10 minutes after fluid loading), CO and cerebral blood flow returned to near control value, while LV perfusion remained low. Oxygen uptake was not significantly affected by fluid loading with either whole blood or Ringer’s. Brain Time CO LV (min) (mllminlkg) (mllminlkg) (ml/min/g) 0.75 t 0.08 5 0.65 ? 0.06 65.8 * 5.0 0.48 2 0.08* 0.49 2 0.06* 13 88.4 2 8.6* 0.51 t 0.08 0.73 t 0.10 20 55.1 * 5.0’ * Indicates statistically significant difference from control (5 < 0.01).
Op Uptake (mllminlkg) 4.18 + 0.29 4.29 + 0.27 4.46 2 0.32 min) value (CK
The changes in organ perfusion can be explained in part by the concurrent changes in blood pressures. Previous studies have shown that the level of central arterial diastolic pressure (CADP) and the central arteriovenous diastolic pressure difference (CAVDP) correlate with vital organ perfusion. In this study, central venous diastolic pressure increased significantly (9.2 to 13.9 mm Hg) after fluid load. However, CADP did not rise proportionately (3 1.9 to 33.9 mm Hg), and the CAVDP actually decreased. Although fluid load during CPR improves CO, flow to the heart and brain decreases. Moreover, there is no increase in oxygen consumption, indicating that fluid loading does not improve metabolic status. Development and Widespread Use of Automatic External Defibrlllators. W. Douglas Weaver, Michael K. Copass, Deborah Hill, Carl Morgan, Robert D. Swenson, Carol Fahrenbruch, Michael D. Emery, Leonard A. Cobb. University of Washington, Seattle, Washington. An automatic external defibrillator (AED) has been used by first responders in our tiered emergency system to treat 408 patients with cardiac arrest and also by three of 43 family members of patients at risk for ventricular fibrillation (VF). The detection algorithm was initially developed from a pre-recorded database but has since been modified based on field observations. The VF detector correctly identified 172 of 196 (88%) of VF database records but only 145 of 275 (53%) VF periods during initial clinical use (P < 0.001). Since modifying the detector, 75 of 83 (90%) VF periods
ABSTRACTS
were correctly identified, a significant improvement over initial performance (P < 0.001). No patient with a rhythm other than VF has been inappropriately shocked. Fortyeight of 171 (28%) patients discovered in VF, two of 158 (1%) in asystole, three of 73 (4%) in EMD, one of six (17%) in ventricular tachycardia have survived. One-quarter of VF patient regained pulse and blood pressure before paramedics arrived. On average, the AED was used 4.8 ? 2.5 minutes, delivered 1.7 -C 0.8 shocks, and effected defibrillation in 68% of 220 shocks. In the layperson experience, two of three patients were resuscitated, and one survived. In all, 51 of 83 (61%) consec-
FROM PERDUE CONFERENCE
ON CPR
utive patients who previously had been resuscitated appear to be candidates for AED. Training of laypersons takes approximately 5 hours, although there is a rapid loss of skills; 93% were judged proficient after class, 72% at one month, and 56% at six months. The instructional sequence and continuing educational material that optimizes performance is not yet clear. Widespread use of AED by first responders is possible and beneficial, algorithm performance can be judged best by field trials, and layperson use is feasible, but there are as yet many undetermined factors that will ultimately define the utility of such an approach.
425