1. The delivery of modern critical care is predicated
on the ability to monitor a large number of physiologic variables and
formulate evidenced-based therapeutic strategies to manage these
2. Technologic advances in monitoring have at least a theoretical
risk of exceeding our ability to understand the clinical implications
of the derived information. This could result in the use of monitoring data
to make inappropriate clinical decisions. Therefore, the implementation
of any new monitoring technology must take into account the relevance and
accuracy of the data obtained, the risks to the patient, as well
as the evidence supporting any intervention directed at correcting
the detected abnormality.
3. The routine use of invasive monitoring devices, specifically
the pulmonary artery catheter, must be questioned in light of the
available evidence that does not demonstrate a clear benefit to
its widespread use in various populations of critically ill patients.
4. The future of physiologic monitoring will be dominated by the
application of noninvasive and highly accurate devices that guide
The Latin verb monere, which means “to
warn, or advise” is the origin for the English word monitor.
In contemporary medical practice, patients undergo monitoring to
detect pathologic variations in physiologic parameters, providing
advanced warning of impending deterioration in the status of one
or more organ systems. The intended goal of this endeavor is that
by using this knowledge, the clinician takes appropriate actions
in a timely fashion to prevent or ameliorate the physiologic derangement.
Furthermore, physiologic monitoring is used not only to warn, but
also to titrate therapeutic interventions, such as fluid resuscitation
or the infusion of vasoactive or inotropic drugs. Monitoring tools
also can be valuable for diagnostic evaluation and assessment of
prognosis. The intensive care unit (ICU) and operating room are
the two locations where the most advanced monitoring capabilities
are routinely used in the care of critically ill patients.
In the broadest sense, physiologic monitoring encompasses a spectrum
of endeavors, ranging in complexity from the routine and intermittent
measurement of the classic vital signs (i.e., temperature, pulse,
arterial blood pressure, and respiratory rate) to the continuous recording
of the oxidation state of cytochrome oxidase, the terminal element
in the mitochondrial electron transport chain. The ability to assess
clinically relevant parameters of tissue and organ status and use
this knowledge to improve patient outcomes represents the “holy grail” of
critical care medicine. Unfortunately, consensus is often lacking
regarding the most appropriate parameters to monitor to achieve
this goal. Furthermore, making an inappropriate therapeutic decision
due to inaccurate physiologic data or misinterpretation of good
data can lead to a worse outcome than having no data at all. Of the
highest importance is the integration of physiologic data obtained
from monitoring into a coherent and evidenced-based treatment plan.
Current technologies available to assist the clinician in this endeavor
are summarized in this chapter, as well as a brief look at emerging ...