To the Editor:-I read the laboratory report, Testing the Competency of the Hemostasis Valve in Introducer Catheters published in Anesthesiology 1998; 88(5):1404-6, with great concern and alarm.
Arrow [registered sign] strives to manufacture our hemostasis valves to the highest standards of performance. However, we think that it is important that practitioners not misread the results of this testing to infer that any manufacturers' valve system is infallible. Another concern is that many practitioners refer to an introducer system and a hemostasis valve in genetic terms; perhaps thinking that this report could apply to all valves in all introducers consequently may develop into a false sense of security. We recommend that an obturator be used anytime the hemostasis valve of the introducer is empty, which applies to the period of time after a catheter has been removed or if the catheter insertion is delayed.
It is important to note that the function of the hemostasis valve is to serve as a seal when a catheter is indwelling or temporarily removed from the indwelling sheath. The valve is not designed as a long-term seal against vacuum or backpressure. The one-way valve must seal well without dampening, occluding, or impeding the insertion and manipulation of the indwelling catheter. For this reason, the valve design is a compromised balance between sealing well and gently holding various catheter sizes. Even though our percutaneous sheath introducer products are manufactured to the highest of standards, no valve is infallible. This simple “better safe than sorry” position is the reason for the obturator use recommendations in our product instructions.
The soft valve in the hemostasis assembly maintains a seal by fully closing around and conforming to an inserted object like a catheter. It is possible, however unlikely, for this material to take a “set” around an inserted catheter so that when the catheter is removed, the soft valve material does not rebound fully to make a complete seal. The function of the obturator is to reduce this potential risk of embolism by ensuring the sealing of the valve after removal of a catheter. Consequently, we unequivocally recommend the use of an obturator cap under any circumstances.
As the authors stated, their hypothesis was that “hemostasis valves of introducer catheters will remain competent to pressures in excess of intrathoracic pressures which may be generated under clinical conditions, and the obturator cap is not essential to prevent air embolism.”
The researcher tested 79 valves: 29 had been used in patients, and 50 were new. All of these valves when tested withstood extreme negative pressures. Even though these data are impressive, the researchers' sample size is small compared with the number of valved percutaneous sheath introducer products that Arrow International [registered sign] has sold during the past 16 years.
We agree that the frequency of a failed valve caused by whatever set of circumstances is extremely rare, but we cannot in good conscience make the recommendation to clinicians that the researchers have made in their article. It seems that to place an obturator cap is such an easy task to potentially save a patient's life.
I hope that you and your subscribers find this information helpful. If you have any questions that I can help answer, please do not hesitate to contact me.
Matthew J. Moore
Product Specialist; Critical Care Products; Arrow International, Inc.; Reading, Pennsylvania;firstname.lastname@example.org
(Accepted for publication November 24, 1998.)