Advances in shock research
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Cardiogenic shock is a relatively specific clinical syndrome characterized by decreased cardiac output, elevated left ventricular filling pressure, and arterial hypotension with vital organ hypoperfusion. It most commonly occurs as the consequence of extensive left ventricular damage due to myocardial infarction. The prognosis of patients with cardiogenic shock is very poor, because by definition there are no readily correctable metabolic, hemodynamic, humoral, or infectious problems whose treatment may lead to improved circulatory function. ⋯ All inotropic agents have the capacity to intensify myocardial ischemia because they may increase myocardial oxygen requirements in the face of limited arterial blood flow; isoproterenol, epinephrine, and norepinephrine appear to be particularly troublesome in this regard. Vasodilator agents (phentolamine, nitroprusside, and nitroglycerin) have also been used to alter left ventricular loading conditions in patients otherwise supported by inotropic drugs, and may be particularly useful in the management of "mechanical" complications of infarction such as mitral regurgitation and interventricular septal rupture. The use of these drugs, just as that of inotropic agents, must be tailored to specific hemodynamic abnormalities documented in individual patients.
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Comparative Study Clinical Trial
Crystalloid versus colloid for fluid resuscitation of hypovolemic patients.
The choice of the initial asanguinous fluid--either crystalloid or colloid--used for the resuscitation of the hypovolemic patient remains controversial. Colloid supporters argue for the careful preservation of the plasma colloid osmotic pressure (PCOP) to protect the lung from pulmonary edema. A careful analysis of the Starling microvascular forces operative at the pulmonary capillary makes such an effect unlikely. ⋯ EVLW remained in the normal range of 7.0 +/- 1.0 ml/kg during the first five hospital days for all patients despite profound decrease in PCOP (less than 15 mm Hg) and a low or negative PCOP - PAWP gradient. Crystalloid resuscitation clearly is not harmful to the lung and it is equally as effective as colloid resuscitation. Crystalloid is markedly less expensive than colloid and, given the greater cost of colloid without evident benefit, one wonders how their further use can be justified.