All surgical patients require monitoring to assess cardiovascular stability, and sometimes may benefit from optimization of their hemodynamic status. Therefore, all surgeons require a basic understanding of physiological underpinnings of hemodynamic monitoring. The physiological rationale is still the primary level of defense for monitoring critically ill patients. Arterial catheterization to monitor arterial pressure is a safe procedure with a low complication rate; however, it should be used only when clear indications exist. There is no evidence that achieving pressures over 65 mm Hg increases organ perfusion or favors outcome. The analysis of pulse pressure variation is a useful method to assess preload responsiveness and a potential tool for resuscitation. CVP has been wrongly used as a parameter of goal for replacement of intravascular volume in shock patients. Volume loading in patients who have CVP greater than 12 mmHg is unlikely to increase cardiac output, and attempts to normalize CVP in early goal-directed therapy during resuscitation have no proven benefit. The use of PAC provides direct access to several physiological parameters, both as raw data and derived measurements (CO, SvO2, DO2). At present, targeting specific levels of DO2 has proven effective only in high-risk surgery patients in the perioperative time. Ppao is often used as a bedside assessment of pulmonary edema, pulmonary vasomotor tone, intravascular volume status, and LV preload and performance. Several publications have explored the potential indications and benefits of the PAC to direct goal therapies. Beyond this controversy, there is a trend toward less invasive methods of hemodynamic monitoring, and current data support protocols of monitoring and goal-directed therapy that could improve outcome in selected group of surgical patients.
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