Surgical hemostatic agents: assessment of drugs and medical devices.

Surgical hemostatic agents are indicated to improve hemostasis when conventional techniques (compression, sutures or electrocoagulation) are inadequate. The National French Authority for Health (Haute Autorité de santé [HAS]) set out to assess these products (medical devices and agents) to determine their optimal utility. This evaluation included one class of products containing some form of human fibrinogen and thrombin and eight classes of medical devices and automated devices to prepare autologous fibrin. The assessment was based on a systematic review of the literature and expert opinion of health care professionals. The main measures of effectiveness of hemostatic agents were the success rate as expressed in terms of the time necessary to obtain adequate hemostasis, the volume of intra and/or postoperative blood loss, the need for blood transfusions, complication rate, duration of operations and hospital stay. A meta-analysis and 52 controlled randomized studies were selected involving cardiac or vascular surgery (19), ENT surgery (11), gastrointestinal surgery (5), urology (4), orthopedic surgery (4). Approximately half of the studies retained in this analysis evaluated blood derived agents (fibrin sealants) while the other half evaluated medical devices. The working group considered that there is not any evidence that these surgical hemostatic agents decrease the rates of transfusion, complications, reoperation, mortality, duration of operation and/or hospital stay. The working group considered that the use of surgical hemostatic agents to improve the safety of hemostasis in the absence of identified bleeding as an alternative to adequate conventional hemostasis was not justified. Surgical hemostatic agents can be used in ad hoc settings, as a complement to conventional methods to control persistent bleeding after conventional hemostatic techniques, or when abundant bleeding has led to biologic hemostatic disorders. The working group also distinguished several particular settings (mouth and dental care in patients under antiagregant or anticoagulation therapy, central nervous system surgery or acute aortic dissection). Comparative data are insufficient to determine if one product is superior to another for a specific use. To evaluate the clinical value of these products, methodologically sound clinical studies are necessary.

Adsorption Isotherms of Cetylpyridinium Chloride with Iron III Salts at Air/Water and Silica/Water Interfaces.

The interaction of iron III salts and cetylpyridinium chloride (CPC) has been studied at the air/water and silica/water interfaces. The surface tension of cetylpyridinium chloride has been determined in aqueous solutions in the presence of iron III chloride and iron III nitrate at two constant pH values, namely, 3.5 and 1.2. It is shown that the surface tension of the cationic surfactant depends upon the ionic strength of the solution through the pH adjustment in the presence of the former salt but not in the presence of the latter. The effect of iron III nitrate on the surface tension of CPC is similar to that of potassium nitrate, indicating that the iron III various-hydrolyzed species do not interfere with the composition of the air/water interface. The competitive adsorption of iron III nitrate salt and the cationic surfactant at a silica/water interface was next investigated. The adsorption isotherms were determined at pH 3.5. It is shown that although the iron III ions, which were added to the silica dispersion in the presence of the cetylpyridinium ions, were strongly bound to the anionic surface sites, the surfactant ions are not salted out in the solution but remain in close vicinity of the silica surface. Conversely as the cationic surfactant is added first to the silica dispersion in the presence of the adsorbed iron III ions, the metal ions and the surfactant ions are both coadsorbed onto the silica surface. It is suggested that iron III hydrolyzed or free cations and the cationic surfactant molecules may not compete for the same adsorption sites onto the silica surface. Copyright 2000 Academic Press.

A field evaluation of the Esophageal Obturator Airway.

The Esophageal Obturator Airway (EOA) has been considered an effective ventilatory technique for cardiopulmonary resuscitation; however, few studies of its field effectiveness have been performed. We evaluated the EOA in 158 cases of prehospital cardiac arrest resuscitated by EMT II personnel utilizing the EOA for airway maintenance. The time of insertion from arrival of the unit and the number of unsuccessful attempts were recorded. The EOA took longer than 4 minutes to insert in 47% of cases. It was incapable of being placed in 18.3% of cases, and required two or more attempts at insertion in 30%. There were six survivors in this series (3.7%). Subsequently, we measured arterial blood gas levels during ventilation with the EOA and after endotracheal intubation in 13 patients. Arterial oxygen tension greater than 60 mm Hg was achieved in only four of 13 patients with the EOA. All patients were hypercarbic and acidotic using the EOA. There was marked improvement in all parameters following ET intubation. The EOA presents technical problems which make it inferior to ET tubes in resuscitation of individuals in the field with cardiac arrest. Close monitoring of its use should be undertaken in areas where it is the primary method for airway maintenance.