Noninvasive physiologic monitoring of high-risk surgical patients

Objectives: To study the feasibility of multicomponent non-invasive monitoring, consisting of a new bioimpedance method for estimating cardiac output together with routine pulse oximetry and transcutaneous oximetry, and to compare physiologic data obtained noninvasively with hemodynamic and oxygen transport data obtained by standard invasive pulmonary artery thermodilution catheter to evaluate circulatory function in high-risk surgical patients. Design: Prospective descriptive analysis of the time course of physiologic patterns in surgical patients. Setting: University-run county hospital. Patients: Seventy-one consecutively monitored, high-risk, critically ill surgical patients in their perioperative period. Outcome Measures: Simultaneous measurements by invasive and noninvasive methods to describe and compare the temporal physiologic patterns of survivors and nonsurvivors. Results: The new impedance cardiac output estimations closely approximated those of the thermodilution method (r=0.82, P<.001). Episodes of hypotension, tachycardia, low cardiac index, arterial hemoglobin desaturation, low transcutaneous oximetry, reduced oxygen delivery, and low oxygen consumption occurred with both groups but were more pronounced in the nonsurvivors than in the survivors. Noninvasive monitoring provided information similar to that of the thermodilution method. Both approaches indicated low flow and poor tissue perfusion (oxygenation) that was worse in the non-survivors. Conclusions: The multicomponent noninvasive monitoring provides continuous online, real-time displays of physiologic data that allow immediate recognition of circulatory dysfunction as well as the means to titrate therapy to appropriate predetermined therapeutic goals. The non- invasive systems are easy to apply, safe, inexpensive, reasonably accurate, and cost-effective.