Norris S O
AACN Clin Issues Crit Care Nurs. 1993 May;4(2):309-19.
Low cardiac output after cardiac surgery may be caused by hypovolemia, myocardial depression, vasoconstriction, and dysrhythmias. Postoperative hypovolemia occurs because of blood volume loss and decreased diastolic filling. Diuresis, intravascular fluid shift into the interstitium, hormonal influences, and bleeding deplete blood volume. Diastolic filling may be compromised by positive end-expiratory pressure, vasodilation, dysrhythmias, and venous return obstruction. The primary indicator of intravascular volume is ventricular preload, which may be measured indirectly with central venous pressure, left atrial pressure, or pulmonary capillary wedge pressure. Recognition of hypovolemia is aided through the use of cardiac pressure trend monitoring and evaluation of noninvasive indicators of hypovolemia. Nursing goals, in response to hypovolemia, are to increase the circulating volume, optimize oxygen delivery, stabilize hemodynamics, improve tissue perfusion, and prevent shock.
心脏手术后的心输出量降低可能由血容量不足、心肌抑制、血管收缩和心律失常引起。术后血容量不足是由于血容量丢失和舒张期充盈减少所致。利尿、血管内液体向间质转移、激素影响和出血会使血容量减少。呼气末正压、血管舒张、心律失常和静脉回流受阻可能会损害舒张期充盈。血管内容量的主要指标是心室前负荷，可通过中心静脉压、左心房压或肺毛细血管楔压间接测量。通过使用心脏压力趋势监测和评估血容量不足的非侵入性指标，有助于识别血容量不足。针对血容量不足的护理目标是增加循环血量、优化氧输送、稳定血流动力学、改善组织灌注并预防休克。
