ABSTRACT
Traditionally, central venous pressure (CVP), the pressure of blood returning to the right atrium, was viewed as indicating preload, and so blood volume, but CVP is a poor predictor of haemodynamic responsiveness. Pale, discoloured, cyanosed or clammy skin indicates poor perfusion – whether from hypovolaemia, vascular disease or excessive vasoconstriction. Intra-arterial blood pressure monitoring is usually more accurate, and slightly higher, than non-invasive measurement, provided arterial traces do not look dampened. Compared with intra-arterial measurement, "dampening" of measurement between arteries and skin surface cause lower systolic and higher diastolic measurements with non-invasive blood pressure – D. S. Picone measured differences in single figures. During removal of internal jugular or subclavian CVCs, negative pressure inspiration could entrain an air embolus between the time the catheter is removed and the site closes. Peripherally inserted central cannulae have a lower infection risk than CVCs. Cardiac output studies enable titration of fluids, inotropes and vasopressors to optimise haemodynamic status in critical illness.
