well, i know what i do both on insertion and when im removing central lines. i am not a crna, but this is apart of my practice set.
i try and visualize the physiology to come up with multiple ways to do things and why they would, or wouldnt work. so a quick review of the "whys" cant hurt (and it keeps it in my head):
during spontaneous breathing, negative intrathoracic pressures generate the pressure gradient for inspiration. upon entry into the venous system, this negative intrathoracic pressure can also encourage air to enter the insertion site and cause air embolism. a pressure difference of 5 cm of h2o across a 14-gauge needle allows 100 ml of air per second to enter the venous system.1
. (in dogs, rapid administration of 0.5-1 ml/kg air is often fatal. 50 ml of air can cause hypotension and dysrhythmias and more than 300 ml of air can be lethal.1
breath holding (valsalva) creates positive pressure in the intrathoracic space. this will minimize the risk for air entry into the catheter. a mechanically delivered positive pressure breath will create the same protection (using the bvm to hold the pts breath).
left side down-trendelenberg position might trap the embolus in the right ventricle and prevent migration to the lung. this is hardly proven, but it cannot hurt the patient if the position is feasible.
i actually cannot think of another way to help avoid the possiblity of an air embolism. the proven one is valsalva.
now on insertion, there are two things to consider. first, let me say that i am not trained in or central line insertion, but i do a few things to create success and avoid complications.
there are 2 schools
of thought in regards to insertion. some people have the patient exhale in order to deflate the lung and decrease the risk of an iatrogenic pneumo. i actually, do not do this. in my practice i actually place my patients in trendelenburg in order to increase venous return thereby dilating the vein and i have the patient valsalva. the reason i do this is to create positive pressure in order to avoid air embolism but also to increase the diameter of the vein thereby making it easier to puncture the subclavian or the ij. always keep a closed system by plugging the end of the cath with your thumb as well until you hook it to a bag. i have attached links to ultrasounds of my own ij in trendelenburg and valsalva
ij in situ normal laying flat
ij in trendelenburg only diameter .45 cm x .99 cm
ij in trendelenburg and valsalva diameter 1.1cm x 1.67 cm
capan lm, miller sm: perioperative embolic complications. in anesthesia & perioperative complications. 2nd edition. benumof jl, saidman lj, editors. mosby, st louis. 1999, pp 685-738