AMERICAN JOURNAL OF EMERGENCY MEDICINE n Volume 4, Number 5 n September 1986

varying in population from 5,000 to 57,000, were random- ized 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 com- munities served as controls. After one year, treatment and control communities were made to cross over. Chest elec- trodes 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:

Total patients Mean age Male/Female Presenting rhythm

Treatment Group Control Group 75 56 69.4 years 68.0 years 53132 38/l 8

VF 42 (56%) 33 (59%) Bradyasystale 24 (32%) 16 (29%) PIVR 9 (12%) 7 (12%)

Witnessed 49 (65%) 32 (57%) CPR prior to ambulance arrival 33 (44%) 38 (68%) Hospital admissions 16 (21%) 6 (11%) Discharge survivors 6* (8%) IT (2%) Discharge survivors from VF 5142 (12%) 1/33T (3%) * One survivor in the treatment group was bradycardic, pulseless, and ap- neic. Pulse and blood pressure returned with assisted ventilation only. t The control group survivor experienced ventricular fibrillation in the am- bulance near the hospital and was subsequently defibrillated in the emer- gency department.

Ambulance response times in the two groups were com- parable (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 pre- sented to the machine, with 54 receiving a defibrillatory shock (84% sensitivity). On eight occasions (12%), tine ven- tricular fibrillation was interpreted as asystole and exter- nally paced. One sequence of ventricular fibrillation was properly evaluated but not detibrillated, and one patient’s permanent pacemaker spikes interfered with proper treat- ment. 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-hos- pital 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 experi- enced 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.

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The effect of moderate fluid loading during electrically in- duced ventricular fibrillation (VF) and CPR in 18 dogs (12-26 kg) was investigated. Oxygen uptake was recorded continuously with a spirometer modified to permit positive- pressure ventilation. Blood flows were measured with radio- active 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’s- treated 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 ce- rebral 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 cere- bral blood flow returned to near control value, while LV perfusion remained low. Oxygen uptake was not signifi- cantly affected by fluid loading with either whole blood or Ringer’s.

Time CO LV Brain Op Uptake (min) (mllminlkg) (ml/min/g) (mllminlkg) (mllminlkg)

5 65.8 * 5.0 0.65 ? 0.06 0.75 t 0.08 4.18 + 0.29 13 88.4 2 8.6* 0.48 2 0.08* 0.49 2 0.06* 4.29 + 0.27 20 55.1 * 5.0’ 0.51 t 0.08 0.73 t 0.10 4.46 2 0.32

* Indicates statistically significant difference from control (5 min) value (CK < 0.01).

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 per- fusion. In this study, central venous diastolic pressure in- creased 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 con- sumption, indicating that fluid loading does not improve metabolic status.

Development and Widespread Use of Automatic External De- fibrlllators. W. Douglas Weaver, Michael K. Copass, Deb- orah Hill, Carl Morgan, Robert D. Swenson, Carol Fahrenbruch, Michael D. Emery, Leonard A. Cobb. Uni- versity 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