Circulation
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Current basic life support (BLS) protocols do not address the physiologic effects of accidental hypothermia in prehospital care. The extreme levels of bradycardia, bradypnea, and peripheral vasoconstriction that often accompany profound hypothermia may complicate the accurate diagnosis of cardiopulmonary arrest in the unmonitored patient. ⋯ This dilemma had led to disagreement among clinicians and researchers in hypothermia about prehospital care protocols for the severely hypothermic patient. This article reviews the controversy and recommends the application of a normal BLS protocol to hypothermic patients presenting in apparent cardiopulmonary arrest.
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Review
Special resuscitation situations: near drowning, traumatic injury, electric shock, and hypothermia.
Special resuscitation situations are cardiopulmonary arrests requiring modification or extension of conventional life support techniques. Significant controversy exists with regard to several aspects of special resuscitation, including whether or not there is a need to clear the airway of a near-drowning victim with the Heimlich maneuver and whether CPR should be initiated in an unmonitored hypothermic patient showing no signs of life. The previous standards and guidelines almost entirely neglected the management of cardiac arrest due to traumatic injury. The conference panel on Special Situations recommended that: the Heimlich maneuver should only be performed on near-drowning victims when the rescuer suspects that foreign matter is obstructing the airway or the victim fails to respond appropriately to mouth-to-mouth ventilation, further investigation is needed to better define the need for, the risks of, and the timing of the Heimlich in the near-drowning victim, there should be an expanded section in the standards and guidelines describing the differences in the management of a victim whose cardiac arrest is due to traumatic injury, CPR is indicated and should be done on a pulseless, unmonitored hypothermic patient in the field, but that a longer time to check for a pulse (up to one minute) may be required, and guidelines that the panel proposed be used for management of the underwater submersion victim in cardiac arrest.
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Blood flow during closed-chest CPR may result from variations in intrathoracic pressure rather than selective compression of the cardiac ventricles. During chest compression, the thoracic and abdominal cavities are subjected to positive pressure fluctuations. It has been suggested that compression of the abdomen may improve left heart outflow during CPR by limiting diaphragmatic movement or improving venous return. ⋯ Selective abdominal binding also increases systolic pressures during CPR but does not improve subdiaphragmatic venous return. Although abdominal binding may increase common carotid flow, it has not been shown to improve cerebral or myocardial perfusion when compared with conventional CPR alone. These CPR adjunct techniques have not been shown to improve outcome from cardiac arrest and should remain experimental until further well-designed studies addressing regional vital organ flow and outcome of resuscitation are performed.
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The addition of interposed abdominal compressions (IACs) to otherwise standard CPR enhances artificial circulation both in anesthetized dogs with ventricular fibrillation and in electrical models of the circulation that demonstrate fundamental mechanisms generating flow. Manual abdominal compressions cause both central aortic and central venous pressure pulses but, because of differences in venous and arterial capacitance, the former are usually greater than the latter. ⋯ However, no study has demonstrated that IAC-CPR improves either short- or long-term survival after cardiac arrest in man. Accordingly, the method remains experimental and cannot be recommended for basic life support at the present time.