The purpose of hemodynamic monitoring is to identify cardiovascular insufficiency and to ensure optimal treatment of the unstable critically ill. Hemodynamic monitoring serves a diagnostic, therapeutic, and resuscitation target role. Although vital signs help assess the adequacy of tissue perfusion, they are a late indicator of tissue ischemia.1 Analysis of hemodynamic variables beyond traditional vital signs allows the clinician to differentiate various causes of hemodynamic instability and intervene appropriately.


Hemodynamic monitoring changes therapeutic decisions in up to 58% of patients and can unmask underlying cardiovascular compromise, allowing for early intervention.2–5 In this chapter, we discuss techniques applicable in the ED setting: blood pressure monitoring, central venous pressure (CVP) monitoring, cardiac output (CO) monitoring, and oxygenation and organ perfusion monitoring (Table 34-1).

Table Graphic Jump Location
Table 34-1 Hemodynamic Variables Obtainable in the ED 

Direct measurement of blood pressure was first performed by Stephen Hales in 1714, when he inserted a brass pipe in the left carotid artery of a living horse tied down on its back. The blood rose 8 ft 3 in. in the pipe above the level of the heart.6 In modern medicine, arterial blood pressure has been the crucial element of the clinical vital signs. Blood pressure is the force exerted by the circulating blood through a blood vessel. The pressure difference (ΔP) between two points in the vessel is governed by Ohm’s law: ΔP = Q × R, where Q is blood flow and R is resistance to flow. The clinical application of Ohm’s law states that the arterial pressure is determined by the CO (or blood flow in liters per minute) and total peripheral resistance (TPR), which means mean arterial pressure (MAP) = CO × TPR. In evaluating blood pressure as a hemodynamic indicator of organ perfusion, the contribution by TPR (the impediment to flow) must be taken into account in relation to CO, which is the measure of effective blood flow to the tissue. Although the more common measure of resistance is systemic vascular resistance, TPR provides a better physiologic measure of impediment to flow. Systemic vascular resistance is calculated as the ratio of total flow (CO) to the pressure difference between MAP and right atrial pressure. Right atrial pressure is not the back pressure ...

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.


About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessMedicine Full Site: One-Year Subscription

Connect to the full suite of AccessMedicine content and resources including more than 250 examination and procedural videos, patient safety modules, an extensive drug database, Q&A, Case Files, and more.

$995 USD
Buy Now

Pay Per View: Timed Access to all of AccessMedicine

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.