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Biomedical subjects

R W Yakaitis

Publications and source records attributed to R W Yakaitis.

At least 19 recordsLinked to original sources
PubMed1985

Effect of epinephrine on defibrillation in ischemic ventricular fibrillation.

Epinephrine is thought to improve the success of defibrillation with countershock therapy. However, a recent study failed to show any effect of epinephrine in dogs with normal coronary arteries undergoing electrically-induced ventricular fibrillation (VF). In the current study, the effects of epinephrine were examined in dogs with coronary occlusion undergoing both spontaneous and electrically-induced fibrillation. Forty pentobarbital-anesthetized dogs were prepared by placing snares around the circumflex and left anterior descending coronary arteries. Fibrillation and subsequent resuscitation were carried out with one coronary artery occluded. Dogs were randomly allocated so that half of the animals underwent spontaneous fibrillation and half were electrically fibrillated. In addition, half received epinephrine (1 mg) during resuscitation and half received normal saline solution (1 ml). After 3 minutes of cardiac arrest, cardiopulmonary resuscitation (CPR) was begun, and 30 seconds later epinephrine or saline were injected. One minute later defibrillation was attempted using successive stored energy doses of 1, 2, 4, 8, 16, and 32 J/kg. Delivered energy and transthoracic impedance were measured for each countershock. Successful defibrillation was defined as conversion to any rhythm other than VF or ventricular tachycardia that degenerated in VF within 10 seconds. No other drugs were given during resuscitation. Neither the type of fibrillation (electrically-induced versus spontaneous) or drug therapy (epinephrine versus placebo) had a significant effect on the incidence of defibrillation or the energy necessary for successful defibrillation. Epinephrine did significantly increase the incidence of resuscitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

The role of epinephrine in CPR: a reappraisal.

Epinephrine is the recommended drug for use in resuscitation from all types of cardiac arrest. Experimental evidence has shown that the actions of epinephrine important for the restoration of spontaneous circulation are mediated by the alpha-adrenergic properties. The beta-adrenergic effects do not aid restoration of spontaneous circulation, nor do they aid defibrillation; however, beta-adrenergic stimulation does increase the oxygen consumption of the fibrillating myocardium, a potentially deleterious effect. The important factor in restoring spontaneous circulation appears to be development of adequate coronary blood flow by increasing coronary perfusion pressure (aortic diastolic minus right atrial pressure). Aortic diastolic pressure can be increased by any potent alpha-adrenergic agonist. Because phenylephrine and methoxamine do not have significant beta-adrenergic actions, they should be considered as alternatives to epinephrine for aid in restoring spontaneous circulation. Once spontaneous circulation is restored, alpha-and/or beta-adrenergic agonists may be needed for circulatory support. Which drugs will provide the best longterm survival has not been established.

Epinephrine↗
PubMed1983

Spontaneous ischemic ventricular fibrillation in dogs: a new model for the study of cardiopulmonary resuscitation.

Most sudden cardiac deaths in man are associated with events causing myocardial ischemia and only 40-60% of these patients are successfully resuscitated. Further progress in reducing the mortality from such events will depend on a better understanding of the interventions used during CPR. Animal models currently used for the study of CPR do not involve myocardial ischemia. A new model of cardiac arrest (spontaneous ischemic ventricular fibrillation) in closed-chest dogs resembles more closely the events occurring in man. Initial controlled, randomized studies of the model demonstrate that it responds to resuscitation in a manner similar to human resuscitation. Further study of this model during CPR may lead to changes in patient care which will improve survival from episodes of sudden cardiac death.

Animals↗
PubMed1981

Mechanism of action of epinephrine in resuscitation from asphyxial arrest.

To determine the relative importance of the alpha and beta adrenergic effects of epinephrine in resuscitation, 32 dogs were studied in four groups. Group A (alpha blocked) received phenoxybenzamine, 70 mg/kg; group B (beta blocked), propranolol 5 mg/kg; group C (alpha and beta blocked) both drugs; and group D (control), no drug. After this treatment and 5 min of asphyxial arrest, all animals received closed chest cardiac massage (CCCM), artificial ventilation (AR), and epinephrine, 1 mg, iv. Resumption of spontaneous circulation occurred with the following frequency: group A, 0/8; group B, 6/8, group C, 0/8, group D, 7/8. The difference in successful resuscitation of the alpha blocked animals and the not alpha blocked animals is statistically significant (P less than or equal to 0.01). It is concluded that the efficacy of epinephrine in aiding resumption of spontaneous circulation from asphyxial arrest is due to alpha adrenergic receptor stimulation and that beta receptor stimulation is not important in determining outcome.

Animals↗
PubMed1981

Comparison of dopamine, dobutamine, and epinephrine in CPR.

Two new catecholamines, dopamine and dobutamine, have found widespread use for cardiovascular support. The relative efficacy of these drugs in aiding resuscitation from cardiopulmonary arrest is unknown. Dogs were subjected to either asphyxial or fibrillatory cardiac arrest. Resuscitation was attempted with artificial ventilation, closed chest cardiac massage, and one of four iv drug protocols: dopamine, 40 mg; epinephrine, 1 mg; dobutamine, 50 mg; or no drug. The incidence of successful resuscitation from both asphyxial and fibrillatory arrest was significantly greater in groups receiving dopamine or epinephrine than in groups receiving dobutamine or no drug. There was no difference in success between the dopamine and epinephrine groups. The authors conclude that, in dogs, dopamine is a useful adjunct to CPR because of its alpha-adrenergic stimulating activity at high doses. Dobutamine does not appear to be of value as the initial therapy of cardiac arrest. If the response in man is similar to that in dogs, dopamine may provide an alternative to epinephrine during CPR.

Animals↗
PubMed1980

Influence of time and therapy on ventricular defibrillation in dogs.

Factors that may influence energy requirements for ventricular defibrillation include the duration of fibrillation and the mode of resuscitation. The present study assesses the effect of these influences on the energy needed for defibrillation. Dogs were anesthetized, and arterial blood pressure and Lead II of the ECG were continuously recorded. Ventricular fibrillation was electrically induced in each dog for a period of 1, 3, 5, or 9 min. Three resuscitation techniques were evaluated: precountershock artificial ventilation (AV) and closed-chest cardiac massage (CCCM); precountershock AV/CCCM and epinephrine, 1 mg IV; and countershock without preliminary AV/CCCM or epinephrine. Each animal was shocked with successive doses of 1, 2, 4, and 8 J/kg, ceasing when either electrical conversion occurred or after the maximum dose had been delivered. If defibrillation was unaccompanied by resumption of spontaneous circulation (systolic pressure greater than 60 mm Hg greater than 2 min), AV/CCCM was administered for 1 min. In general, the incidence of defibrillation was inversely proportional to the duration of fibrillation. Epinephrine had no significant effect on the energy dose needed for conversion. After 2 min of fibrillation, however, epinephrine became increasingly important for restoration of circulation. The technique of immediate countershock was effective for episodes of fibrillation limited to approximately 3 min. Regardless of therapy, for intervals of fibrillation of up to 6 min, Gompertz data curves indicated that a delivered energy of 4--5 J/kg is the approximate energy dose associated with the maximum achievable incidence of defibrillation within the limits of this experimental protocol.

Animals↗
PubMed1979

Relative importance of alpha and beta adrenergic receptors during resuscitation.

Successful resuscitation from cardiac arrest in the asphyxiated dog model has been ascribed to the use of artificial ventilation, closed chest cardiac massage, and administration of a vasopressor. Controversy remains over whether the most commonly employed vasopressor, epinephrine, exerts its effects primarily by elevating diastolic pressure and reestablishing coronary flow, or by exciting cardiac pacemaker cells and enhancing myocardial contractility. To observe pure alpha and beta adrenergic receptor influences during resuscitation, three groups (alpha-blocked, beta-blocked, unblocked) of dogs were studied. beta-blocked dogs resuscitated with phenylephrine and unblocked dogs resuscitated with epinephrine experienced 100% successful resumption of spontaneous circulation after 5 min of asphyxia-induced arrest. Only 27% of alpha-blocked animals resuscitated with isoproterenol were successfully revived. The appearance of the ECG during cardiac arrest and resuscitation could in no way be used to predict the outcome of resuscitation attempts. Results suggest that, initially, alpha receptor stimulation with concomitant diastolic pressure elevation is more important to the success of resuscitation than beta receptor stimulation.

Animals↗
PubMedDate not supplied

Influence of pH and hypoxia on the success of defibrillation.

Clinical impressions about the problem of defibrillation during states of acid-base imbalance and hypoxia have been influenced by studies involving the effect of these derangements on the ventricular fibrillation threshold. Based on body weight, energy requirements for defibrillation in normal dogs were compared to requirements in dogs subjected to commonly encountered acid-base disturbances and severe hypoxemia. No significant differences were found. Seventy-five percent of all animals in the study were electrically converted with low-to-moderate levels of energy. The incidence of spontaneous resumption of circulation following defibrillation was lowest in animals subjected to metabolic acidosis and hypoxia. The results suggest that pH and blood gas alterations, previously shown to influence the normal ventricular fibrillation threshold, do not significantly affect the normal defibrillation threshold.

Acid-Base Imbalance↗