Monday November 6, 2006
Awareness of biggest port on venous catheter !

If central venous catheter is inserted, it is important to be aware of size of biggest lumen. Like in triple lumen, biggest port is of 16 G, and in quad lumen is of 14 G. In situations where IVF boluses are required as in septic patients, it is appropriate to write orders to infuse IVF bolus via biggest size port of catheter. As per Hagen-Poiseuille equation just 2 fold increase in radius increases flow by 16 fold. Although It is not always necessary that biggest port is the distal port but in most widely use TLCs - distal port is the largest bore port and as they are not positioned closely against the vessel wall, they may help in free flow of the IVF. Also, thrombus formation could be faster in the smaller ports causing obstruction to free flow of bolus.

It is true that distal port is mostly used and preferred for CVP monitoring but in a situation where IVF boluses are priority, it is not important which port is in use for CVP measurements, but adopt a consistent port so measurements can be 'trend'. One study compared CVP measurement via 3 ports and found clinically unsignificant mean difference of 1.12 - 1.28 mm Hg 1.


Related previous pearl: CVP via PICC


Reference:

Influence of Port Site on Central Venous Pressure Measurements From Triple-Lumen Catheters in Critically Ill Adults - American Journal of Critical Care - JANUARY 1998 - VOLUME 7 - NUMBER 1