Hemodynamic monitoring simply defined is the measurement and analysis of biological signals emanating from the cardiovascular system. Therapies based on these signals are then titrated and physiologic response is measured. Ideally hemodynamic monitoring should involve a holistic approach. Oxygen delivery at both global and regional levels as well as tissue perfusion and cellular health should be assessed. Although easy to articulate, our ability to monitor in this fashion remains limited. Indeed it is sobering to reflect on the paucity of high-quality validation of the commonly used monitors. No randomized trials exist to prove that even monitoring of basic vital signs is beneficial. In fact none are likely to ever be conducted. That being said, in a field as heavily weighted on monitoring, technological advances have evolved over the past 30 years. New noninvasive techniques attempt to negate the necessity of indwelling vascular catheters. The pulmonary artery catheter remains a cornerstone of hemodynamic monitoring despite the persistent controversy about its efficacy. In this chapter, hemodynamic monitoring techniques and important physiologic concepts behind these methods are addressed.

PHYSIOLOGIC PRINCIPLES

The basic tenet of hemodynamic monitoring is to ensure adequate oxygenation at the cellular level. Physiologic signals obtained by various monitoring techniques are often manipulated to this end. Outside of experimental technologies it is not possible to monitor cellular hypoxia; hence global and sometimes regional variables are used.