Current opinion in critical care
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Curr Opin Crit Care · Jun 2001
Comparative StudyArginine vasopressin during cardiopulmonary resuscitation and vasodilatory shock: current experience and future perspectives.
Epinephrine use during cardiopulmonary resuscitation (CPR) is controversial because of its receptor-mediated adverse effects such as increased myocardial oxygen consumption, ventricular arrhythmias, ventilation-perfusion defect, postresuscitation myocardial dysfunction, ventricular arrhythmias, and cardiac failure. In the CPR laboratory, vasopressin improved vital organ blood flow, cerebral oxygen delivery, resuscitability, and neurologic recovery more than did epinephrine. ⋯ The new international CPR guidelines recommend 40 U vasopressin intravenously, and 1 mg epinephrine intravenously, as equally effective for the treatment of adult patients in ventricular fibrillation; however, no recommendation for vasopressin has been made to date for adult patients with asystole and pulseless electrical activity, or in children, because of lack of clinical data. When adrenergic vasopressors were unable to maintain arterial blood pressure in patients with vasodilatory shock, continuous infusions of vasopressin (0.04-0.10 U/min) stabilized cardiocirculatory parameters and even ensured weaning from catecholamines.
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Controversy still exists concerning the strategy of targeting so-called supranormal levels of oxygen delivery as a means of improving outcome from high-risk surgery. The pathogenesis of postoperative morbidity is not fully defined; however, it seems likely that the gastrointestinal tract plays a pivotal role, particularly as a source of endotoxin, which is a potent stimulator of the inflammatory response. Delayed recovery of gastrointestinal function also is a major contributor to postoperative morbidity. Demonstration of a significant reduction in gut ischemia, endotoxemia, postoperative inflammatory response, and morbidity in a high-risk general surgical population as a result of perioperative hemodynamic optimization would be a highly worthwhile study.
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Curr Opin Crit Care · Jun 2001
ReviewAssessment of the microcirculatory flow in patients in the intensive care unit.
Various techniques have been used at bedside to assess the microcirculation of critically ill patients, including nailfold videomicroscopy, laser doppler techniques, and orthogonal polarization spectral imaging. Nailfold videomicroscopy was introduced first, but its value may be limited by the extreme sensitivity of nailfold microcirculation to external temperature or vasoconstrictive agents. Laser Doppler techniques can measure gastric or jejunal mucosal blood flow as well as skin and muscle blood flow, but do not take into account blood flow heterogeneity, a major parameter of microcirculation. The recent introduction of orthogonal polarization spectral imaging techniques allows direct visualization of microcirculation in critically ill patients, opening a new area for the investigation of the pathophysiologic processes involved in the hemodynamic alterations of shock states.
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This review discusses the mechanisms of neurologic damage during and after global cerebral ischemia caused by cardiac arrest. The different pathways of membrane destruction by radicals, free fatty acids, excitatory amino acids (neurotransmitters), calcium, glucose metabolism, and oxygen availability and demand in relation to metabolic rate are briefly discussed. ⋯ Two pioneering studies of the 1950s and four recent publications (in part preliminary results of ongoing studies) in humans are discussed in detail. The conclusions are as follows: (1) hypothermia holds promise as the only specific brain therapy after cardiac arrest so far; (2) hyperthermia is not tolerable after successful resuscitation; and (3) if the ongoing European multicenter trial of hypothermia after cardiac arrest finds a significant benefit to mild hypothermia, withholding hypothermia may be ethically hard to defend.