Preparation of the patient:
If appropriate, the patient should be given a brief description of the procedure which includes some form of risk:benefit analysis and consent for the procedure should then be obtained. Some form of anaesthesia (either local or general) will be necessary. If the patient is to undergo surgery, insertion after induction of anaesthesia may be preferred but has the obvious drawback of depriving the anaesthetist of access to haemodynamic data at a time of potential haemodynamic instability.

In critically-ill patients, the catheter should generally be inserted under local anaesthesia. In these cases, the issues of the appropriate posture and level of sedation for the procedure should be carefully considered by the physician.

It should be remembered that the principal reason for placing the patient in the head-down position is to eliminate the risk of air-entrainment during venepuncture by ensuring that the venous pressure at the point of entry is above atmospheric pressure throughout the respiratory cycle.

The head-down posture also has the secondary effects of increasing the diameter of the vein and locally raising the venous pressure thereby making the vein less compressible. These secondary effects are particularly important in the case of jugular venepuncture (Figure 1) and less so in the case of the subclavian venepuncture (Figure 2).

If the patient already has a high venous pressure, a head-down position may not only be unnecessary, but dangerous, as the increase in venous return can precipitate acute ventricular failure. A head-down posture also leads to respiratory changes which may be sufficient to tip the balance for an unintubated patient with respiratory distress. The 'rule of thumb' is that if a patient assumes a head-up posture because of dyspnoea, this posture should not be altered during insertion of a PAC. (If the venous pressure is low in a patient with acute respiratory distress, the use of a peripheral site of insertion should be considered.)

If the right internal jugular approach is used, a rolled up sheet placed transversely under the shoulders may improve access to the vein. If the subclavian approach is used, a rolled up sheet placed longitudinally between the shoulder blades will have a similar effect.

If care is taken during infiltration of the insertion site, sedation is usually not necessary for the procedure. If premedication is used, awake insertion will not provoke myocardial ischaemia or other adverse haemodynamic events ^{1, 2}. O'Connor et al ³ have recently prospectively examined the the cardiovascular and catecholamine responses to pulmonary artery catheterisation when performed before or after induction of general anaesthesia. There were no statistically significant changes in any cardiovascular or catecholamine variable with time when compared with the base-line measurements and there were no statistically significant differences in plasma catecholamine levels between the awake and the anaesthetised groups.

The operator must be gowned and gloved and use a fully aseptic technique. The skin in the area of the insertion site should be prepared according to institutional guidelines. The area should be widely draped with sterile drapes. The patient is now ready for placement of the PAC introducer sheath (Figure 3) by the selected route of insertion.

1. Waller JL, Zaidan JR, Kaplan JA, et al: Hemodynamic response to preoperative vascular cannulation in patients with coronary artery disease. Anesthesiology 52:219, 1982

2. Quintin L, Whalley DO, Wynands JE, et al: The effects of vascular catheterization upon heart rate and blood pressure before aortocoronary bypass surgery. Can Anaesth Soc J 28:244, 1981

3. O'Connor PJ, Welsh KR, Cross MH, Shah MV. Cardiovascular responses to pulmonary artery catheterization. Eur J Anaesthesiol 2000 Mar;17(3):168-72

Last edited on: 10/12/2000