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contraction of the ventricles at very rapid rates (Adam and Osborne 2005). Ventricular fibrillation results in cardiac arrest and death if not reversed with defibrillation and the injection of adrenaline. The cause of this condition is often myocardial infarction (MI), electrical shock, acidosis, electrolyte disturbances and hypovolaemia (Resuscitation Council UK 2005).

Body fluids are good conductors of electricity so it is possible through electrocardiography to observe how the currents generated are transmitted through the heart. The electrocardiograph provides a graphic representation and record (electrocardiogram (ECG)) of electrical activity as the heart beats (see Twelvelead electrocardiogram (ECG)). The ECG makes it possible to identify abnormalities in electrical conduction within the heart. Changes in the pattern or timing of the deflection in the ECG may indicate problems with the heart’s conduction system, such as those caused by MI (Marieb and Hoehn 2010). For examples of normal and abnormal ECGs, see Twelvelead electrocardiogram (ECG).

Amplitude

Amplitude is a reflection of pulse strength and the elasticity of the arterial wall. This varies because of the alternating strong and weak ventricular contractions (Bickley and Szilagyi 2009). The flexibility of the artery of the young adult feels different from the hard artery of the patient suffering from arteriosclerosis. It takes some clinical experience to appreciate the differences in amplitude. However, it is important to be able to recognize major changes such as the faint flickering pulse of the severely hypovolaemic patient or the irregular pulse in cardiac arrhythmias.

Assessing gross pulse irregularity

Paradoxical pulse is a pulse that markedly decreases in amplitude during inspiration. On inspiration, more blood is pooled in the lungs and so decreases the return to the left side of the heart; this affects the consequent stroke volume. A paradoxical pulse is usually regarded as normal, although in conjunction with such features as hypotension and dyspnoea, it may indicate cardiac tamponade (Bickley and Szilagyi 2009), hypovolaemia, severe airway obstruction or tension pneumothorax (Wong 2007).

When there is a gross pulse irregularity, it may be useful to use a stethoscope to assess the apical heart beat. This is done by placing the diaphragm of the stethoscope over the apex of the heart and counting the beats for 60 seconds. A second nurse should record the radial pulse at the same time. The deficit between the two should be noted using, for example, different colours on the patient’s chart to indicate the apex and radial rates (Docherty 2002).

Evidencebased approaches

Rationale

The pulse is taken for the following reasons.

To gather information on the heart rate, pattern of beats (rhythm) and amplitude (strength) of pulse.

To determine the individual’s pulse on admission as a base for comparing future measurements.

To monitor changes in pulse.

(Marieb and Hoehn 2010)

Indications

Conditions in which a patient’s pulse may need careful monitoring are described below.

Postoperative and critically ill patients require monitoring of the pulse to assess for cardiovascular stability. The patient’s pulse should be recorded preoperatively in order to establish a baseline and to make comparisons. Hypovolaemic shock post surgery from the loss of plasma or whole blood results in a decrease in circulatory blood volume. The resulting acceleration in heart rate causes a tachycardia that can be felt in the pulse. The greater the loss in volume, the more thready the pulse is likely to feel.

Blood transfusions require careful monitoring of the pulse as an incompatible blood transfusion may lead to a rise in pulse rate (British Committee for Standards in Haematology 1999) (see Chapter 8).

Patients with local or systemic infections or inflammatory reactions require monitoring of their pulse to detect sepsis/severe sepsis. This is characterized by a decrease in the mean arterial pressure (MAP) and a rise in pulse rate (Marieb and Hoehn 2010).

Patients