The tunneling of the PICCs is a technique that has been developed in recent years. The rationale of tunneling can be twofold:
- in the case of the absence of an appropriate vein in terms of caliber and accessibility in Dawson's green zone, the clinician may decide to cannulate a vein (basilica, axillary, etc.) located in Dawson's yellow zone. However, this area is not appropriate as an exit site, due to its proximity to the armpit. In this case, tunneling allows to achieve the ideal puncture site simultaneously with an ideal exit site. Therefore, Dawson's ZIM (Zone Insertion Method) helps to define when tunneling is needed (i.e.: when the ideal venipuncture site is in the yellow zone) but also how long should the tunnel be (i.e.: the tunnel should be long enough to obtain the exit site in the green zone).
- tunneling, by putting a distance between the exit site and site where the catheter enters the vein, has a direct protective effect against the risk of extraluminal bacterial contamination. In selected cases, tunneling may be adopted programmatically to reduce infectious risk.
Tunneled PICCs should be power injectable, in polyurethane, open-ended, not valved. Evidence from the literature shows that silicone PICCs have no advantage over those in polyurethane, but - on the contrary - they have many disadvantages (low flow; high incidence of dislocation and rupture, because of their fragility). There is no evidence of any advantage in the use of valved PICCs, which are associated with an increased risk of malfunction and higher cost if compared to non-valved PICCs. Thus, the same PICCs used as non-tunneled should be used as tunneled PICC.
Also tunneled PICCs should be inserted according to a well standardized technique, such as the one summarized in the SIP protocol (see our website).