Introduction

Patients undergoing cardiothoracic surgery risk significant perioperative neurological dysfunction. This includes stroke, short- and long-term neurocognitive dysfunction, depression, delirium and confusion. The reasons for such injury are multi-factorial, and include hypoperfusion, macro- and microemboli, effects of general anaesthesia, initiation of inflammatory pathways and metabolic derangement. Postoperative monitoring is aimed at identifying abnormalities arising from a primary injury and/or preventing further neurological injury.

In addition, neurological monitoring is useful for assessing sedation levels; patients on the critical care unit should ideally be lightly sedated, readily rousable and cooperative. Most drugs are given using standard dosing guidelines without applying knowledge of their pharmacokinetics and dynamics, and large variability is found when studying population pharmacology. Sedation and analgesia should be individualized and goal directed; therefore, appropriate monitoring is crucial.

Clinical monitoring

For the majority ofpatients in a cardiothoracic critical care unit, the central nervous system (CNS) is currently monitored clinically by means of regular neurological examination and sedation scores only.

Neurological examination

A physical examination forms the basis of any assessment of the CNS. However, because most patients are recovering from the effects of general anaesthesia or continue to receive a combination of sedatives and analgesics, only simple examination is possible and hence only gross neurological deficits elicited.