Key learning points

• Understand the reasons why a patient's heart may develop rhythm problems in theatre

• Understand the reason for the correct positioning of ECG leads

• Appreciate the causes of intra-operative changes in ECG

• Understand the nature and ECG signatures of major rhythm problems

• Understand the nature and ECG signatures of changes in cardiac perfusion

When a patient is recovering from an anaesthetic, careful observation is required in order to note developing problems at an early stage.

Meticulous clinical observation of the patient can distinguish early problems associated with respiration and with circulation. One of the most important pieces of equipment to assist in patient assessment is the electrocardiograph (ECG) monitor.

The ECG was a breakthrough in the assessment of patients which we often take for granted. As a non-invasive and painless observation tool its information is crucial to the safe delivery of patients from surgery and anaesthetic.

This chapter will look at the nature of ECG monitoring, what the monitor can tell you about the patient and what it cannot.

Some common problems of cardiac function will then be described and their ECG signature discussed.

The information that ECG gives us

An ECG gives a graphic description of electrical events in the heart – an electrical signature of cardiac function, if you will. It does not measure any mechanical function of the heart, such as the pumping action. Mechanical function will mostly result from the electrical events, but there are circumstances where it may not.