Importance of monitoring in high risk surgical patients.

Increased metabolic requirements by surgical trauma is responsible of the changes in cardiac index and oxygen delivery (DO2), represent compensatory adaptation in circulatory functions stimulated by increased metabolic needs. The amount of this compensation varies with age, gender, severity of illness, operation type, associated medical conditions, shock duration, complications, organ failure, and outcome. Hypotension, low cardiac index, arterial hemoglobin desaturation, low oxygen delivery, and low oxygen consumption served and sometimes are persistent over time; these abnormalities were more notorious in the nonsurvivors than in the survivors. Lethal circulatory dysfunctions may begin during the intraoperative period but become more apparent before and are responsible of organ failure during postoperative stages. An approach that measures adequacy of tissue perfusion is a fundamental objective in anesthesia and critical care medicine. Traditional measures of tissue perfusion have included arterial pressure monitoring, urine output, arterial pH and blood lactate. These measures have major limitations, and changes in these measures may significantly lag behind clinical interventions. After trauma and major surgery despite normalization of these variables, global tissue hypoxia may still persist. Unrecognized or untreated conditions may lead to organ failure and death. In critical or high risk patients, early invasive monitoring is necessary to precisely define the adequacy of the cardiac response and to individually tailor therapy. The care provided in the first hours significantly impacts the progression of organ failure and mortality. Although this period is brief compared with the total length of hospitalization, physiological determinants of outcome may be established before ICU admission. Early postoperative monitoring revealed differences in survivor and nonsurvivor patterns and provided goals for improving outcome.