United Kingdom emergency departments (EDs) are subject to complex national performance targets and the recent development of Acute Medicine as a subspeciality branch of general medicine that deals solely with the first 12-72 hours of care of the medically unwell patient. The ‘four-hour rule’, introduced in 2003/4, mandated that 98% of patients presenting to an ED must be seen, treated and then admitted or discharged in under four hours. As a result, many EDs have ED-led observation units (OUs). Given that many UK EDs remain relatively understaffed, OUs tend to be small and take very well-defined low-risk patients. Although the St. Thomas Hospital OU offered a high standard of care, its smooth functioning was often challenged by the demands of the four-hour target, with the OU seen as an option to avoid patients ‘breaching’ their ED length of stay target. In 2012, the model of care was changed, with a focus on goal directed outcomes, for both admission and discharge. Eight beds within the new emergency medical unit (EMU) are now dedicated to goal-directed therapy, with the remainder for rapid goal-directed discharge.

The aim of hemodynamic monitoring is to enable the optimization of cardiac output and therefore improve oxygen delivery to the tissues, avoiding the accumulation of oxygen debt, in the perioperative period. Instigating goal-directed therapy based on validated optimization algorithms has been shown to reduce mortality in high-risk patients and complications in moderate- to high-risk patients.

A number of devices are available to facilitate this goal. Devices that continuously analyze the arterial pressure waveform to calculate various flow parameters have been developed and validated. These devices have facilitated the introduction of hemodynamic monitoring to the wider surgical population, providing useful clinical information that enables the judicious use of fluid therapy whilst avoiding hypervolemia.

This chapter explores the role that hemodynamic optimization plays in perioperative care, describes some of the commonly used invasive hemodynamic monitors, and explains how to use the information produced effectively. Used correctly, any monitor can be useful to improve outcome if applied to the right population, at the right time, and with the right strategy.

Key Learning Points

1. 1. Sepsis remains a major cause of death in the paediatric population.

2. 2. Mortality is higher in children with co-morbidities than in those without.

3. 3. Volume resuscitation is still the mainstay of initial resuscitation.

4. 4. Adrenaline is a rational choice as a first-line vasoactive agent.

5. 5. Combining clinical examination with plasma lactate can be used to guide resuscitation.

Estimation of intravascular volume status by clinical examination and static measurements such as central venous pressure and pulmonary capillary wedge pressure do not predict fluid responsiveness. Current evidence indicates that dynamic monitoring of arterial pressure and derived indices are the most sensitive and specific means of determining fluid responsiveness, especially in mechanically ventilated patients. Several monitors that automate and embellish this approach, a few of which are noninvasive, are now commercially available and they are gradually being incorporated into intensive and perioperative care practice. This chapter reviews the physiologic underpinnings of how and why the arterial pressure waveform can be used to determine fluid responsiveness and gives an overview of the devices incorporating these principles.