Annals of emergency medicine
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Sixty-five patients who arrived in the emergency department in cardiac arrest were studied prospectively to determine whether central venous pH could be used as an accurate predictor of arterial pH in prolonged cardiac arrest. Central venous and arterial access were obtained as soon as possible after arrival in the emergency department. Simultaneous arterial and venous samples were drawn and sent for blood gas analysis. ⋯ In 13 of these 15 patients the acid base status would have been managed correctly based on the predicted pHa (pHcv + 0.12 correction factor). The pHcv was also valuable in identifying a second subgroup of patients who required no further bicarbonate therapy; all patients who had a pHcv greater than or equal to 7.15 had a pHa greater than 7.30 (21 patients). The central venous pH was found to be a useful index of arterial pH when applied to a definable subset of patients, which in this study constituted 45% of all patients in prolonged cardiac arrest.
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Recent animal studies and preliminary clinical observations suggest that the addition of interposed abdominal compressions (IAC) to ventilation and chest compression of standard cardiopulmonary resuscitation (CPR) augments blood flow, blood pressures, and immediate survival. To investigate the physical basis for enhanced circulation during IAC-CPR, we developed an electrical model of the circulation. Heart and blood vessels were modeled as resistive-capacitive networks, pressures as voltages, blood flow as electric current, blood inertia as inductance, and the cardiac and venous valves as diodes. ⋯ During simulation of CPR, IAC improved cranial and myocardial perfusion at all levels of chest compression pressure by amounts linearly related to peak abdominal pressure, suggesting that the abdomen can function as a second, independent blood pump during CPR. Brain and heart flow were improved further during simulated vasoconstriction in kidneys, abdominal viscera, and extremities. Based on the fundamental properties of the cardiovascular system represented in the model, abdominal counterpulsation provides a rational basis for flow augmentation during CPR.
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Standard external CPR (SECPR) steps A, B, and C can maintain the brain's viability if started immediately, but not after prolonged arrest times. "New CPR" (simultaneous ventilation-compression CPR, SVC-CPR) is not suitable for basic life support, and may not be physiologically superior to optimally performed SECPR. The superiority of interposed abdominal compression CPR (IAC-CPR) over SECPR for basic life support is also uncertain. Open-chest CPR is physiologically superior to all external CPR methods studied thus far. ⋯ Barbiturates have been shown to exert no breakthrough effect on outcome after cardiac arrest, but are safe in the hands of those skilled in advanced intensive care. Barbiturates may be of adjunctive value after prolonged cardiac arrest, particularly when used to suppress seizures, facilitate controlled ventilation, and reduce intracranial pressure. Calcium entry blockers have been shown in animal models to improve hemodynamics and cerebral outcome postarrest, but not consistently.(ABSTRACT TRUNCATED AT 250 WORDS)
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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. ⋯ 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.
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Comparative Study
Circulatory support during cardiac arrest using a pneumatic vest and abdominal binder with simultaneous high-pressure airway inflation.
Animal and clinical studies suggest that blood flow during closed-chest cardiopulmonary resuscitation (CPR) results from phasic intrathoracic pressure fluctuations produced by rhythmic sternal depressions rather than from cardiac compression. Using physiologic observations made in animals and human beings during circulatory collapse and vigorous coughing, a pneumatic thoracic vest garment and abdominal binder device has been designed to emulate "cough CPR." Hemodynamic findings and microsphere regional perfusion observed during cardiac arrest and airway/vest/binder inflation are comparable to those observed during simultaneous chest compression and pulmonary ventilation CPR (SCV-CPR). ⋯ The vest/binder apparatus significantly improved the coronary perfusion gradient and survival. Further studies are in progress to determine the clinical utility of this promising resuscitation adjunct.