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Irrigating fluidRelated Patent Categories: Drug, Bio-affecting And Body Treating Compositions, In Vivo Diagnosis Or In Vivo TestingIrrigating fluid description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060171889, Irrigating fluid. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention is within the field of irrigating fluids used in surgery on a mammal body, more specifically irrigating fluids containing a marker to enable detection of irrigating fluid absorbed by said body during surgery. The invention is based on the use of a new marker in such irrigating fluids, said new marker enabling a simple and proper monitoring of the irrigating fluid absorbed by the body while at the same time improving the conditions for the surgeon. BACKGROUND OF THE INVENTION [0002] Especially in endoscopic operations in the genitourinary tract the use of an irrigating fluid is required to gently dilate mucosal spaces and to remove blood and cut tissue from the operating field. There are several different irrigating fluids available commercially and the choice tends to be governed largely by tradition, although the price and properties of the fluid (e.g. stickiness and transparency) also play a role. The pharmacological effects of the fluid become important whenever it is absorbed by the patient. However, adverse reactions to irrigating fluids have not been documented as they have for drugs. [0003] Most irrigating fluids were developed when the documentation of safety was much less important that it is today. Pharmacologists and regulatory authorities also pay little attention to solutions because they are conceived as devices (like soap and detergents) rather than drugs. Nevertheless, numerous reports of symptomatic and even fatal fluid absorption during TURP (transurethral resection of the prostate) and transcervical resection of the endometrium (TCRE, an operation for alleviating menorrhagia) emphasize the importance of using an irrigating fluid with a favourable profile of adverse effects. [0004] For many years, little comparative data were available showing whether one irrigating fluid is more prone to adverse effects than others. However, during the past decade several studies covering this topic have been reported. [0005] A summary of said reports and further details concerning irrigating fluids can be found in British Journal of Urology (1997), 79, 669-680. Some of said details will, however, be presented below. [0006] Sterile water was used as irrigating fluid during the early years of TURP. However, obscure reactions with post-operative haemoglobulinuria sometimes occured and severe cases even led to death. Enrichment of the blood with salicylate and glucose when added to the sterile water made urologists realize, in 1947, that the absorption of the irrigating fluid into the circulation through severed prostatic veins must be the cause of the haemolysis. As electrolytes do not allow cutting by electrocautery, one or several non-electrolyte solutes capable of preventing haemolysis were then added to the irrigating fluid. [0007] Glycine was the first suggested as suitable, and the other irrigating fluids used today, mannitol and mixtures of sorbitol and mannitol, were introduced somewhat later. An example of a document disclosing an irrigating fluid containing glycerine or mannitol is Journal of Surgical Research, Vol 95, 2001, pp 114-125. Reference can also be made to GB 2234897 A, which discloses the use of glycerine and L-arginine in an irrigating fluid. [0008] Despite their non-haemolytic properties, absorption of the new irrigating fluids continued to be associated with adverse events which were often summarized as transurethral resection reactions (TUR syndrome). The clinical descriptions of this syndrome from the mid-1950s are still the cornerstones of our view of the risks associated with the use of irrigating fluids. [0009] The uptake of small amounts of irrigating fluid occurs during almost every TURP and TCRE. The absorbed volume varies greatly and cannot be predicted in the individual patient, although it tends to be larger in extended and bloody operations. The uptake of 1 L of fluid, which corresponds to an acute decrease in the serum sodium concentration of 5-8 mmol/L, is the volume above which the risk of absorption-related symptoms is statistically increased. [0010] Thus, in many cases the uptake of irrigating fluid, vascularly and extravascularly, is considerable. If said uptake exceeds 2-3 L the situation for the patient becomes lethal, and in more than 25% of actual cases the absorption has been reported to exceed 0.3 L. [0011] Therefore, in addition to attempts to find an irrigating fluid composition which is absorbed to an extent as minor as possible, efforts have been made to find markers for such irrigating fluids by means of which absorbed amounts of fluid can be detected as early as possible. [0012] One type of marker, or rather monitoring means, which is on the market, is a methodology where the patient is on a balance and his weight is checked. Such a methodology is, however, associated with considerable problems in calculating the amount fed to and removed from the patient during the course studied. [0013] A different methodology is the use of ethanol as a marker added to the rinsing fluid. More specifically, ethanol is added to the fluid and the ethanol content of the air exhaled by the patient is recorded. The use of this new technique is disclosed in a number of documents, e.g. The Journal of Urology, Vol. 149, 502-506, March 1993, and U.S. Pat. No. 5,603,332. This method solved part of the problems but new problems arose instead. Thus, for instance, the speed of detection of exhaled ethanol is slow, the accuracy of detection of small amounts of ethanol is low and side effects with respect to the patient occur, such as dizziness and even alcohol dependence. [0014] Primarily as a consequence of the non-accuracy of the method referred to a solute, especially glycine, has been added to the rinsing fluid (generally sterile water) so as to enhance the viscosity thereof, to reduce the absorbed amount of fluid, as well as to prevent or inhibit the heamolytic action thereof. However, by such a measure the irrigating fluid becomes less clear and the visibility for the surgeon is reduced, which is a considerable disadvantage as a clear and good sight for the surgeon is an essential prerequisite for surgery of the kind referred to. DISCLOSURE OF THE INVENTION [0015] The present invention is based on the use of a new marker for irrigating fluids of the types referred to above. More specifically, it has been found that the gas nitrous oxide (N.sub.2O) can be used as such a marker. Thus, the distribution kinetics of nitrous oxide makes it possible to measure the amount thereof in the expired breath from the patient during surgery of the kind disclosed above. Furthermore, said amount is essentially proportional to the absorbed amount of irrigating fluid. In addition thereto, the use of nitrous oxide in this respect shows great advantages as compared to the use of ethanol for the same purpose. Some of these advantages are the following. [0016] When nitrous oxide is added as a marker, already small amounts of absorbed rinsing or irrigating fluid can be detected within seconds. In other words, the present invention enables the use of a very rapid and accurate detection of fluid absorbed by the animal body. Hence, necessary measures can be taken at an early stage and in fact before symptoms occur. In addition thereto, this generally means that pure rinsing fluid, such as sterile water, without any added solutes, can be used as the irrigating fluid, which eliminates the previous disadvantages connected with such additions. Furthermore, nitrous oxide can be added to the fluid in advance and kept in solution for several years if using a suitable container material. In addition thereto, the detection of exhaled nitrous oxide is very accurate and can be made with simple and even existing nitrous oxide monitors. For instance, such monitors are available in anesthesia machines, which monitors may be used as such or easily converted into more accurate monitors. In this context, it should even be possible to design a common monitor for the purpose of the present invention as well as for anesthesia. Finally, as concerns the known analgesic effect with i.v. nitrous oxide, such an effect should be very limited and should not constitute any problem. [0017] More specifically, according to a first aspect of the present invention, there is provided a surgical irrigating fluid composition comprising a rinsing fluid and a fluid absorption marker, the characteristic feature of said composition being that said marker comprises nitrous oxide and is present in an amount which is detectable via a mammal, including human, body which is the subject of said surgery. [0018] Although, in general, the marker used in accordance with the present invention is detectable at any suitable site of the mammal body, the most convenient way of detecting the same is via the expired breath from the mammal in question. Accordingly, in a preferable embodiment of the composition, said nitrous oxide is preferably present therein in an amount that is detectable in said expired breath. [0019] The rinsing fluid referred to is selected in accordance with knowledge known per se in this technical field. Thus, it preferably comprises or consists of sterile water. [0020] Although one of the great advantages with the present invention is that pure water could be used as rinsing fluid, it is of course also within the scope of the invention to utilise a viscosity-enhancing and/or haemolysis-preventing solute as an additive if this is required or preferable for some specific reason. Thus, one embodiment of the composition claimed is a composition wherein the rinsing fluid comprises or contains a haemolysis-preventing solute. Such a solute is generally selected in accordance with general knowledge within this field. Examples of preferable solutes in this respect are glycine, mannitol and sorbitol or mixtures thereof. [0021] If used, said solute is preferably utilised within the range of 0.1-5.0% by weight, more preferably 0.5-2.5% by weight, and even more preferably 1.0-2.0% by weight, based on the weight of said rinsing fluid. Continue reading about Irrigating fluid... 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