Circulation
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Three forms of treatment are available for patients with paroxysmal supraventricular tachycardia (PSVT): nonpharmacologic, pharmacologic, and electrical. Nonpharmacologic treatments increase vagal tone and include the traditional carotid sinus massage and Valsalva maneuver as well as head-down tilt, activation of the diving reflex, and use of the pneumatic antishock garment. ⋯ Patients with antegrade accessory pathway conduction (such as those with Wolff-Parkinson-White syndrome) and a history of atrial fibrillation should be treated with intravenous procainamide if they are hemodynamically stable and with synchronized electrical countershock if they are hemodynamically unstable. Synchronized electrical countershock is the treatment of choice for hemodynamically unstable patients.
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The finding that blood flow during external chest compression may be due to increased intrathoracic pressure, and the subsequent reporting of increased carotid blood flow with simultaneous ventilation and chest compression or with abdominal binding during CPR ignited a flurry of investigations into alternative approaches to CPR. A number of alterations of the conventional CPR technique were proposed, many resulting in improved hemodynamics when compared with standard CPR techniques in the same subject. However, some of the proposed methods increased cerebral blood flow but decreased myocardial perfusion. ⋯ Not all studies support the conclusion that blood flow during closed-chest compression is secondary to increased intrathoracic pressure. It is probable that in man there is a spectrum. In some individuals the predominant mechanism of blood flow during CPR may be cardiac and/or vascular compression, and in others flow may be secondary to an increased intrathoracic pressure.
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Comparative Study
Vest inflation without simultaneous ventilation during cardiac arrest in dogs: improved survival from prolonged cardiopulmonary resuscitation.
Myocardial and cerebral blood flow can be generated during cardiac arrest by techniques that manipulate intrathoracic pressure. Augmentation of intrathoracic pressure by high-pressure ventilation simultaneous with compression of the chest in dogs has been shown to produce higher flows to the heart and brain, but has limited usefulness because of the requirement for endotracheal intubation and complex devices. A system was developed that can produce high intrathoracic pressure without simultaneous ventilation by use of a pneumatically cycled vest placed around the thorax (vest cardiopulmonary resuscitation [CPR]). ⋯ Vest CPR was compared with manual CPR with either conventional (300 newtons) or high (430 newtons) sternal force. After induction of ventricular fibrillation, each technique was performed for 26 min. Defibrillation was then performed.(ABSTRACT TRUNCATED AT 250 WORDS)
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Artificial ventilation is a cornerstone of basic life support-cardiopulmonary resuscitation (BLS-CPR). Recent data corroborate clinical studies performed in the 1950s and 1960s, suggesting a need to change the present American Heart Association standards for artificial ventilation. These studies show that gastric insufflation followed by regurgitation and pulmonary aspiration are a major hazard of artificial ventilation with an unprotected airway. ⋯ These methods of ventilation predispose the victim to gastric insufflation. Alternative methods of ventilation with longer inspiratory time and thus lower flow rate and peak inspiratory pressure are suggested. Additionally, rescue personnel, particularly EMTs and paramedics, should be taught how to apply cricoid pressure to prevent gastric insufflation in victims with an unprotected airway.
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Management of foreign body airway obstruction continues to be a major controversy in emergency medical care. Much of the disagreement is without doubt based on lack of a uniformly accepted model of acute airway obstruction representative of the clinical event. A variety of models have been used to assess different aspects of airway obstruction by foreign bodies. ⋯ Human volunteers, anesthetized and paralyzed patients, and cadavers have also been used. In several recent studies it was concluded that subdiaphragmatic pressure is the treatment of choice, while in at least one additional study firm back blows applied with the patient's head hanging downward were recommended as the treatment most likely to relieve airway obstruction. It seems likely that these apparently conflicting views can be reconciled and that a consensus recommendation for treatment of this emergency can be effected.