To the Editor:-I read with interest Dr. Kempen's description of the use of the Lever Lock cannula (Becton Dickinson and Company, Franklin Lakes, NJ) to connect a rapid infusion system to any existing intravenous access without the need to disconnect from the cannula (Anesthesiology 1996; 85:1492). Although I share his concerns regarding possible inadvertent removal of the existing cannula and the need to avoid blood spillage, I am concerned by his assertion that flow resistances are not significantly increased. It is unclear on what evidence this statement is based. I have previously described the in vitro effects of the Lever Lock on fluid delivery. [1] Even though the Lever Lock cannula is short and of a relatively large bore (15-gauge), it does cause a 10% reduction in flow rates through 16- and 14-gauge cannulae when it is included within the access system. It is in such settings as trauma and obstetrics that one often wishes flow to be maximal and to not be restricted by an unnecessary component. Additionally, it should be assumed that the length of intravenous tubing that remains between the Y-port and the access cannula provides additional resistance to flow because of its smaller internal diameter compared with blood or trauma tubing. Perhaps the practice he describes may be useful while other intravenous access is being established. If no other access can be established, then the flow through the existing cannula should be optimized and not limited by the Lever Lock cannula. Nevertheless, the assumed benefits of accessing an intravenous system in the way described by Dr. Kempen should be balanced against the potential for reduced flows compared with those achievable by connection of a high-volume infusion set directly to the intravenous cannula.
Gerard J. McHugh, F.A.N.Z.C.A.
Department of Anaesthesia and Intensive Care; Palmerston North Hospital; Palmerston North; New Zealand
(Accepted for publication April 25, 1997.)
