Donald D. Brown

Prehospital Defibrillation Performed by Emergency Medical Technicians in Rural Communities

Survival after out-of-hospital cardiac arrest is poor in communities served only by basic ambulance services, but conventional advanced prehospital care is not an option for most rural communities. Ambulance technicians in 18 small communities (average population, 10,400) were trained to recognize and defibrillate ventricular fibrillation. Neither endotracheal intubation nor medication was used. Twelve additional communities of similar size where such early defibrillation was not attempted provided control data. In the communities where early defibrillation was available, 12 of 64 patients (19 per cent) who were found in ventricular fibrillation were resuscitated and discharged alive from the hospital; this was true of only 1 of 31 such patients (3 per cent) in the control communities, where only basic life support was available (P less than 0.05). Ten (83 per cent) of the long-term survivors received electrical shocks administered solely by the technicians. Early defibrillation by minimally trained ambulance technicians is an effective approach to emergency cardiac care in rural communities.

Decreased Bioavailability of Digoxin Due to Antacids and Kaolin-Pectin

Employing a Latin-square design and single-dose studies of bioavailability in 10 normal human volunteers, we tested the hypothesis that antacids and kaolin-pectin might interfere with the bioavailability of orally administered digoxin. Cumulative six-day urinary digoxin excretion (expressed as the percentage of a 0.75-mg dose recovered) was: control, 40.1+/-3.0 (S.E.); aluminum hydroxide, 30.7+/-2.9; magnesium hydroxide, 27.1+/-2.4; magnesium trisilicate, 29.1+/-1.7; and kaolin-pectin 23.4+/-2.0. The differences in means were highly significant (F = 10.47, P less than 0.005). Further analysis (multiple comparison test) revealed that control differed significantly from each of the other treatments (alpha = 0.05), but there was no such difference between any of the other treatment groups. The decreased cumulative excretion produced by antacids and kaolin-pectin reflected a striking reduction in digoxin absorption associated with these compounds that was not related to alteration of gut transit time or to adsorption of digoxin to these gastrointestinal medications.

Self-adhesive monitor/defibrillation pads improve prehospital defibrillation success

We compared self-adhesive, dual-function monitor/defibrillation electrode pads to standard chest monitoring leads and hand-held electrode paddles in the management of prehospital ventricular fibrillation in a single urban paramedic service. Shocks were delivered more quickly following paramedic arrival with self-adhesive pads than with hand-held paddles (1.6 vs 2.5 min; P less than .001). Ventricular fibrillation was terminated more frequently when shocks were delivered using the self-adhesive pads (55 of 58 patients, 95%) than when shocks were delivered using hand-held paddles (49 of 69 patients, 71%; P less than .005). Initial shocks delivered with self-adhesive pads were especially effective, converting 40 of 58 (69%) patients to an organized rhythm on the first or second shock; this was true of only 24 of 69 (35%) patients shocked with hand-held paddles (P less than .001). Patient survival to hospital admission improved when self-adhesive pads were used: 30 of the 58 (52%) patients shocked with self-adhesive pads achieved hospital admission, while only 21 of 69 patients (30%; P less than .025) survived to admission when hand-held paddles were used. In addition, electrical artifact that interfered with accurate rhythm interpretation was far more prevalent when standard monitoring electrodes were used, including artifact that resulted in inappropriate shock delivery (23% of patients monitored with standard electrodes vs 3% of patients monitored with self-adhesive pads; P less than .005). Self-adhesive monitor/defibrillation pads are superior to standard monitoring leads and hand-held electrode paddles in the management of prehospital ventricular fibrillation.

A new rhythm library for testing automatic external defibrillators: Performance of three devices☆

A library of arrhythmias obtained from patients with cardiac arrest was developed. Such a data base will permit both in vitro testing of the rhythm analysis system of automatic external defibrillators before clinical field trials are conducted and comparison of devices. Defibrillators equipped with voice/electrocardiographic tape recorders and used in the prehospital defibrillation programs in Iowa and King County, Washington provided the rhythm source. From these recordings, segments of ventricular fibrillation with minimal artifact and a duration of greater than or equal to 6 s were selected. Segments of ventricular fibrillation (n = 102) were categorized by average peak amplitude as fine (1 to less than 3 mm), medium (3 to less than 7 mm), coarse (7 to less than 12 mm) and extra coarse (greater than or equal to 12 mm), and transcribed onto high fidelity videocassette tapes. Nonventricular fibrillation cardiac arrest rhythms (n = 144), which included wide complex idioventricular rhythms, ventricular and supraventricular tachycardias, asystole and artifact, were also transcribed. Automatic external defibrillators developed by three manufacturers reached a treat (shock) decision on 88 to 93% of the ventricular fibrillation rhythms and on 5 to 10% of the nonventricular fibrillation rhythms. The latter decisions were defined as false positive, though for many rapid nonventricular fibrillation rhythms, countershock may be the appropriate treatment response. There were no statistically significant differences among the three devices in the shock/no shock decisions. A variety of ventricular fibrillation arrhythmias and terminology to express the preclinical performance of automatic external defibrillators are defined. Three commercially available automatic external defibrillators appear to successfully identify ventricular fibrillation and nonventricular fibrillation rhythms.(ABSTRACT TRUNCATED AT 250 WORDS)

Design of a multicenter randomized trial for the stroke prevention in atrial fibrillation study

Individuals with nonvalvular atrial fibrillation are at increased risk of stroke. The Stroke Prevention in Atrial Fibrillation Study is a 15-center randomized clinical trial examining the risks and benefits of low-intensity warfarin (prothrombin time of 1.3-1.8 times control) and aspirin (325 mg/day) in patients with constant or intermittent atrial fibrillation. Candidates for anticoagulation (group I) are randomized to receive warfarin in an open-label fashion, aspirin, or placebo; the last two treatments are given in a double-blind fashion. Warfarin-ineligible patients (group II) are randomized to receive aspirin or placebo in a double-blind fashion. Primary end points are ischemic stroke and systemic embolism. Secondary end points are death, transient ischemic attack, myocardial infarction, and unstable angina pectoris. Analysis is based on the intention-to-treat principle. The anticipated rate of primary end points in patients receiving placebo is 6%/yr. The sample size of 1,644 patients is based on a projected reduction in the rate of primary end points of 50% by warfarin and of 33% by aspirin (beta = 0.2, alpha = 0.05). Patient entry commenced in June 1987 and will continue for 3 years, with an additional year of follow-up. High-risk subsamples identified by clinical and echocardiographic criteria are sought prospectively.

Citizen response to cardiopulmonary emergencies

Since 1985, it has become apparent that the key to survival from adult sudden cardiac death is prompt defibrillation. Any delay from the time of collapse to the initial countershock will decrease the likelihood of survival. It also has been determined that CPR performed by lay rescuers is not begun promptly and, once started, often is performed for more than one minute before the emergency medical services (EMS) system is accessed, which significantly delays the time to defibrillation. In adults, therefore, the rescuer should phone first to activate the EMS system before performing CPR. In the pediatric population, respiratory arrests are far more common than cardiac arrests. Therefore, a rescuer should perform one minute of rescue support before activating the EMS system (a concept termed phone fast). It is recognized that this change is dependent upon a national EMS system that is still evolving. It is hoped that this change to phone first and phone fast will provide an impetus for rapid development of the EMS infrastructure.

Survival from out-of-hospital cardiac arrest: Effects of patient age and presence of 911 emergency medical services phone access☆

The purpose of this investigation was to determine factors associated with survival from out-of-hospital cardiac arrest, including effects of 911 Emergency Medical Services telephone access and the age of patient. Subjects included 1,753 prehospital cardiac arrest patients in Iowa. Patient survival status and other variables were compared for patients with access to a 911 service with those who did not, and for different age categories, using univariate associations and multivariate logistic regression analysis. The presence of 911 telephone access was significantly associated with survival from out-of-hospital cardiac arrest (9.18% versus 5.35% survival for 911 versus no 911 groups, respectively). This association was partially the result of the significant association of 911 with decreased time from collapse to call for help, decreased time to cardiopulmonary resuscitation (CPR), and decreased time to first shock (if in ventricular fibrillation [VF]). Younger age was significantly associated with survival in univariate analyses (8.94% versus 6.26% survival for younger versus older age groups, respectively), but this was not an independent association, which is indicated by the lack of significance of age in the multivariate model.

Effect of sulfasalazine on digoxin bioavailability

Low levels of digoxin were noted in a patient receiving digoxin and sulfasalazine (SSA). Discontinuation of SSA resulted in a significant increase in serum digoxin levels. To determine whether or not SSA consistently interfered with the therapeutic effect of digoxin, both drugs were administered to 10 normal subjects in a crossover study. Each received 2 doses of digoxin (0.5 mg, elixir): one dose given alone, and a second dose after 6 days of treatment with SSA. When digoxin was given with SSA, the average area under the serum digoxin curve fell from the control value of 8.79 ng hr ml−1 to 6.66 ng hr ml−1 (p < 0.05), fell and total urinary excretion decreased from 278 mcg/10 days to 228 mcg/10 days (p < 0.025). These changes suggest interference with the bioavailability of digoxin by SSA. Studies were conducted to determine whether SSA inhibited digoxin absorption by physically absorbing the glycoside from solution. In vitro tests failed to reveal any significant adsorptive properties for SSA.

Effect of furosemide on the renal excretion of digoxin

Digoxin serum and urine levels were determined by radioimmunoassay in 6 subjects (4 patients with heart disease and 2 volunteers without heart disease) who had been maintained on oral digoxin (0.25 or 0.5 mg daily). Observations were made during a 3‐day control period and then during 8 days of concomitant digoxin and oral furosemide (40 mg daily) therapy. Serum digoxin levels determined 10 and 24 hr after each dose of digoxin averaged 1.2 ± 0.1 ng/ml (M ± SE) during control and 1.3 ± 0.1 during the last 3 days on digoxin and furosemide. The daily urinary excretion of digoxin averaged 51 ± 6% of the oral dose during control and 52 ± 6 during the entire period of furosemide administration. The renal clearance of digoxin and creatinine averaged 94 ± 7 and 87 ± 11 ml/min, respectively, during control; corresponding values were 88 ± 8 and 85 ± 9 for urine collections demonstrating a distinct diuretic effect of furosemide and 87 ± 8 and 75 ± 10 for urine collections not demonstrating such an effect during diuretic therapy. The results suggest that the diuretic effect of furosemide does not significantly affect the excretion of digoxin.