Annex 3. Measurement of central venous pressure

The jugular venous pressure is usually measured with the patient propped up at 45° to the horizontal. The venous pressure waves in the internal jugular vein become visible in the supraclavicular fossa (provided the neck muscles are relaxed) at a pressure of approximately 4 cm H₂O. The wave form is characteristic in sinus rhythm (two waves for every arterial pulse). The height of the wave relative to the clavicles can be increased by lowering the patient, and the wave itself is usually not palpable. It must be distinguished from the carotid arterial pulsation. Measurement of the central venous pressure by examination of the external jugular vein or the filling of veins on the dorsum of the hand at different arm elevations is less reliable (e.g. the external jugular vein may be kinked in the supraclavicular fossa, and therefore not in free communication with the great veins and right atrium). However, rapid emptying of neck veins distended by occluding them at the base of the neck indicates that the venous pressure is not high.

In seriously ill patients, or those in whom assessment is considered inaccurate, a central venous catheter should be inserted. The catheter may be inserted into the jugular or subclavian vein provided that adequate facilities for a sterile procedure and subsequent nursing are available. Four approaches are possible: antecubital (Fig. A3.1), infraclavicular (Fig. A3.2), internal jugular and supraclavicular (Fig. A3.3).

Before readings can be taken, the zero on the manometer must be aligned as accurately as possible with the horizontal plane of the right atrium. A simple spirit level (e.g. 20-ml glass ampoule containing liquid with a bubble, taped to a ruler) can be used to locate the manometer zero at the same height as an appropriate chest-wall landmark, such as the mid-axillary line, in the supine patient (Fig. A3.4).

Fig. A3.1. Central venous pressure monitoring in a township hospital in rural Myanmar (Burma). A 70-cm catheter was inserted into an antecubital vein (Seldinger technique) and advanced until its tip was in the superior vena cava. An extension tube is connected to a simple saline manometer with its zero point at the level of the mid-axillary line

© D. A. Warrell

Fig. A3.2. Central venous pressure monitoring. Puncture of the subclavian vein (infraclavicular approach) preparatory to inserting a guide wire and short catheter (Seldinger technique)

© D. A. Warrell

Fig. A3.3. Central venous pressure monitoring. Surface markings of the subclavian vein for needle insertion by the supraclavicular approach

© D. A. Warrell

Fig. A3.4. Levelling of the central venous pressure manometer at the mid-axillary line using a home-made spirit level (ruler plus glass ampoule), in a Thai provincial hospital

© D. A. Warrell

If a central venous catheter is used, strict attention must be given to asepsis. Infection, air embolism and thrombosis are potential complications, especially if the catheter remains in place for a long time.