GOVERNMENT RIGHTSThis invention was made with Government support under Contract No. W81XWH-11-C-0062 awarded by the U.S. Army Medical Research Acquisition Activity (USAMRAA). The Government has certain rights to the invention.
The embodiments disclosed herein relate generally to medical training kits and methods. In especially preferred forms, the embodiments disclosed herein relate to kits and methods to assist in the simulated trauma training of personnel (e.g., medical first responders) for treatment of hemorrhaging wounds.
Military first responders must be prepared to treat uncontrolled hemorrhage, which remains the primary cause of death from combat wounds. Simulated trauma training is the bridge that spans the gap between classroom study and live animal training and, ultimately, battlefield experience. It is critical, therefore, that simulated trauma training be as realistic and as up to date as possible in terms of wounding patterns and advanced technologies designed to treat such wounds in the field.
Unfortunately, current blood simulation technologies are limited to dyed water or other similarly unrealistic approximations that do not closely mimic the look, feel and biological properties of human blood. There is no known commercial product available that accurately replicates the coagulation and clotting properties of human blood, especially as it relates to training first responders in the use of current and developmental hemostatic products, such as QUICK CLOT® COMBAT GAUZE™ commercially available from Combat Medical Systems™ of Fayetteville, N.C., CHITOGAUZE™ commercially available from HemCon Medical Technologies, Inc. of Portland, Oreg., and CELOX™ gauze commercially available from Medtrade Products LTD. of Crewe, UK.
It is therefore towards fulfilling the need of more realistic personnel training for traumatic hemorrhage control that the embodiments as disclosed herein are directed.
Medical training kits and methods are provided which include a simulated liquid blood which simulates mammalian whole blood and a simulated hemostatic component. The simulated liquid blood includes a gellable component. The simulated hemostatic component includes a gelling agent. The gelling agent causes the gellable component in the simulated liquid blood to form a mass of semi-solid or solid material in response to the simulated blood being brought into contact therewith to thereby simulate blood clotting.
According to some embodiments, the simulated liquid blood is a dilute acidic aqueous solution comprising chitosan as the gellable component. The chitosan may be present in the simulated blood formulation in an amount between about 0.6 to about 2.0 wt. %, and have a molecular weight of between about 50,000 Da to about 500,000 Da. In certain forms, the chitosan liquid can be autoclaved at temperatures between about 100 to about 150° C., at pressures of between about 5 to about 25 psi and a time of between about 1 minute to about 90 minutes and/or deacetylated so as to possess a percent deacetylation value (% DA) of at least about 70% (e.g., between about 70% to 100%).
The simulated blood closely approximates the look, feel and biological properties of whole mammalian, especially human, blood. In this regard, the simulated blood formulation may comprise at least one colorant in an amount sufficient to mimic coloration of whole mammalian blood and/or at least one additive selected from the group consisting of viscosity modifiers (e.g., cellulosic materials) and tactile agents (e.g., glycerol).
In certain embodiments the medical training kits and methods will include a simulated blood which comprises chitosan as a gellable component, and a simulated hemostatic component which comprises a gelling agent in sufficient amount to cause the chitosan to gel (desolubilize, polymerize, precipitate, complex and/or cross-link) so as to form a semi-solid or solid mass of chitosan in response to physical contact between the simulated blood and the gelling agent. The gelling agent may be at least one selected from the group consisting of, for example, sodium tripolyphosphate (NaTPP), β-glycerophospate, sodium bicarbonate, sodium carbonate and Rose Bengal.
The simulated hemostatic component may be in the form of a particulate (e.g., powder, granules or flakes) or liquid that may be brought into direct contact with the simulated blood. According to some embodiments, the simulated hemostatic component may include a carrier in or on which the gelling agent is provided. Suitable carriers for the gelling agent include liquids, gels and various physical substrates in the form of fabrics, gauzes, bandages, pads, sponges, dressings and the like typically encountered in the medical field. One embodiment of the hemostatic component may thus be in the form of a simulated hemostatic dressing which includes a fabric substrate carrying a particulate gelling agent.
In use, personnel (e.g., medical first responders) may be trained to treat wound hemorrhage by providing a simulated wound (e.g., a simulated wound associated with a training mannequin) and causing the simulated gellable liquid blood to flow into the wound in a manner that simulates hemorrhage. A simulated hemostatic component may thus be applied according to suitable treatment protocol to the wound in contact with the simulated blood. In such a manner, the gelling agent of the simulated hemostatic component is caused to interact physically with the gellable component of the simulated liquid blood and form a mass of semi-solid or solid material thereby simulating blood clotting.
These and other aspects of the present invention will become more clear after careful consideration is given to the following detailed description of a presently preferred exemplary embodiment thereof.
As used herein and in the accompanying claims, the terms below are intended to have the following definitions.
“Simulated blood” means a flowable liquid medium which visually and tactilely simulates whole mammalian blood, especially whole human blood. A “simulated blood” will thus closely mimic the look and feel of whole blood in terms of coloration, viscosity, feel (e.g., stickiness) and clotting/caking characteristics in the presence of a simulated hemostatic agent.
“Gellable” means the ability of a liquid medium to form a mass or lump of solid or semi-solid (gel) material which in sufficient quantity impedes (or stops entirely) the ability of the liquid medium to flow.
“Gellation” means that the gellable material forms a mass or lump of solid or semi-solid material which is the result of insolubilization, precipitation, polymerization, crosslinking, complexation and the like.
A “gelling agent” is a substance which causes gel to form in a gellable liquid in response to physical contact between the liquid and the gelling agent. In a simulated blood, the gelling agent will thus be capable of desolubulizing, precipitating, polymerizing, complexing, cross-linking and the like a non-biological gellable component in the simulated blood so as to form a semi-solid or solid mass (clot) of the gellable component.
A “simulated hemostatic component” is a material that either stands alone in the form of a particulate (e.g., powder, granules or flakes) or is incorporated into or onto a liquid, gel or solid carrier and which includes at least one gelling agent.
“Simulated hemostatic dressing” means a fabric (usually a gauze) that has been treated with and thus carries a sufficient amount of at least one gelling agent.
“Chitosan liquid” means a solution or suspension of chitosan in a dilute acidic aqueous medium.
“Fabric” means a collection of filaments, fibers and/or yarns which form a textile article having structural integrity. A fabric may thus be formed by means of conventional weaving, braiding, knitting, warp-knit weft insertion, spinbonding, melt blowing techniques to form structurally integrated masses of filaments, fibers and/or yarns.
“Synthetic” means that a textile article is man-made from a fiber-forming substance including polymers synthesized from chemical compounds, modified or transformed natural polymers, and minerals. Synthetic fibers are thus distinguishable from natural fibers such as cotton, wool, silk and flax.
“Filament” means a fibrous strand of extreme or indefinite length.
“Fiber” means a fibrous strand of definite length, such as a staple fiber.
“Yarn” means a collection of numerous filaments or fibers which may or may not be textured, spun, twisted or laid together.
Embodiments of the kits and methods as disclosed herein may include a simulated blood and a simulated hemostatic component which includes a gelling agent. According to certain embodiments, the simulated hemostatic component may be in the form of a simulated hemostatic dressing which includes a fabric substrate and a gelling agent carried by the fabric substrate. In other embodiments, the simulated hemostatic component is in the form of a simulated hemostatic agent, which comprises at least one gelling agent in the form of a particulate (e.g., powder, granule or flake). In use, the simulated blood may thus be provided as a source of blood flowing from a simulated wound of a training mannequin. The simulated hemostatic component (e.g., the gelling agent serving as a simulated hemostatic powder or a simulated hemostatic dressing comprised of a fabric and a gelling agent carried by the fabric) may thus be used by personnel being trained (e.g., a medical first responder trainee) in a simulated treatment of a hemorrhaging wound associated with the training mannequin.
The simulated blood component is a flowable liquid which visually and tactilely mimics natural whole mammalian (preferably human) blood. In certain preferred embodiments, the simulated blood is a flowable liquid having a viscosity at room temperature (20° C.) of between about 1 to about 6 cP, more preferably between about 3 to about 5 cP. The simulated blood in especially preferred embodiments includes chitosan which is dissolved or suspended in an acidic aqueous liquid and a colorant sufficient to achieve a red color simulating whole blood.
Virtually any form of chitosan that is soluble in an acidic aqueous liquid may be employed in the embodiments disclosed herein. Thus, a wide variety of commercially available forms of chitosan having a range of molecular weights of between about 50,000 Da to about 500,000 Da may be employed. In this regard, the molecular weight, concentration and degree of deacetylation of the chitosan can be selected so as to achieve the desired combination of properties (e.g., viscosity, appearance, gellability and the like) to mimic whole blood.
The molecular weight of the chitosan, and hence the viscosity of the chitosan liquid, can be adjusted by conventional autoclaving technique. Specifically, the viscosity of the chitosan liquid may be decreased by autoclaving a chitosan liquid containing a relatively higher molecular weight chitosan for a suitable time period to achieve the desired viscosity properties of the chitosan liquid. Autoclaving may also impart a brownish coloration and opacity to the chitosan liquid which, when combined with a subsequently added colorant, more closely mimics the reddish-brown coloration and opacity of whole blood. Suitable autoclaving conditions include autoclave temperatures of between about 100 to about 150° C., autoclave pressures of between about 5 to about 25 psi and a time of between about 1 minute to about 90 minutes, more preferably about 120-125° C. at 10-15 psi for about 10 to about 90 minutes. Suitable autoclaving conditions include a temperature of about 121° C., a pressure of about 15 psi and a time of about 15 or 75 minutes.
The chitosan employed in the simulated blood component preferably has a percent deacetylation value (% DA) of at least about 70%, more preferably between about 80% to 100%. In certain embodiments, the chitosan will have a % DA of between about 85% to about 95%. Deacetylation can be achieved by subjecting chitosan to deacetylation conditions, for example, contacting the chitosan at elevated temperature (e.g., about 120° C.) with a basic solution (e.g., sodium hydroxide), under nitrogen for a sufficient time period (e.g., between about 1 to about 3 hours).
The simulated blood component will typically comprise between about 0.6 to about 2.0 wt. %, more preferably between about 1.0 to about 1.5 wt. %, of chitosan. As noted above, the chitosan is preferably dissolved or suspended in a dilute acidic aqueous liquid having a pH of between about 4 to about 6, more preferably between about 4 to about 5. Virtually any dilute acid may be employed, for example, acetic acid, lactic acid, dilute hydrochloric (HCl) acid and the like. One preferred acidic liquid includes an aqueous acetic acid solution having an acetic acid concentration of between about 0.03 M to about 0.10 M, preferably between about 0.075 M to about 0.1 M.
Virtually any colorant that does not cause polymerization, cross-linking, complexation and/or precipitation of the chitosan can be employed to achieve the coloration of the simulated blood component that is desired to mimic the coloration of whole blood. The colorant may thus be one or more organic and/or inorganic liquid or pigment color additive that is capable of being dissolved or suspended in the acidic chitosan liquid.
Suitable colorants include, for example, alizarin (1,2-dihydroxyanthraquinone) crimson pigment, lac dye pigment, oenin chloride (malvidin-3-O-glucoside chloride), quinacridone red pigment (5,12-dihydro-quino[2,3-b]acridine-7,14-dione), venetian red pigment, napthol red pigment and concentrated (e.g., 2× to 4×) natural cherry juice (or other red fruit extracts). The colorant may be used alone or as combinations of two or more of the same. Most preferably, the colorant is provided in the simulated blood component to achieve red-green-blue (RGB) color coordinates of comparable to whole blood, i.e., a red (R) coordinate of about 94±9, a green (G) coordinate of about 37±3 and a blue (B) coordinate of about 40±4. The R-coordinate may thus range from about 45 to about 110, the G-coordinate may range from about 25 to about 55 and the B-coordinate may range from about 30 to about 50.
A variety of optional additives may be employed to provide the desired physical properties to either the simulated blood or to the simulated “clot” that results from interaction of the simulated blood with the simulated hemostatic agent. For example, a viscosity modifier (e.g., a cellulosic such as methyl cellulose) may be added to the simulated blood component to impart desirable viscosity characteristics (e.g., so as to provide greater “tackiness”). Suitable tactile agents, such as glycerol, may be employed to impart suitable “stickiness” to the simulated blood component. Glycerol also has an added benefit of decreasing clothing fabric staining tendencies of the simulated blood component.
The optional additives may be employed in amounts between 0 to about 40 wt. % of the simulated blood component. For example, the viscosity modifier may be employed in an amount of up to about 5.0 wt. %, and if employed may be present in an amount of between about 1.0 wt. % to about 5.0 wt. %, preferably between about 1.5 wt. % to about 3.5 wt. %. The tactile agent may additionally (or alternatively) be employed in an amount of up to about 30 wt. %, and if employed may be present in an amount between about 1.0 wt. % to about 30 wt. %, preferably between about 5 wt. % to about 25 wt. %.
The simulated blood component may be prepared by dissolving or suspending powdered chitosan of an appropriate degree of deacetylation in a dilute acidic aqueous liquid heated to a temperature between about 65° C. to about 80° C. to form a base chitosan liquid. Undissolved chitosan may be allowed to settle from the base liquid for removal by any suitable separation technique (e.g., vacuum filtration through 5 μm filtration membrane). In some embodiments, the base chitosan liquid may then be autoclaved under the conditions noted previously so as to reduce viscosity or impart opacity and/or a brownish coloration to the base chitosan solution. The colorant and other optional additives may then be blended into the base chitosan liquid. The resulting liquid may then be allowed to stand so as to settle out non-dissolved/suspended material and subjected to separation (e.g., vacuum filtration). The simulated blood component that is obtained may be collected and stored in a suitable container until use.
Embodiments of the simulated hemostatic component will necessarily include a gelling agent for gelling the gellable component in the simulated blood so as to mimic blood “clotting” when brought into physical contact with the simulated blood. In certain embodiments the simulated hemostatic component will be in the form of a simulated hemostatic dressing which includes a fabric substrate which carries the gelling agent. In other embodiments, the simulated hemostatic component will be in the form of a hemostatic particulate, liquid or gel material containing the gelling agent which can be brought directly into contact with the simulated blood.
The gelling agent is any material which on contact with the simulated blood component causes the gellable component in the simulated blood to desolubulize, polymerize, complex, precipitate and/or cross-link so as to form a semi-solid or solid mass. Thus, in those embodiments which employ chitosan as the gellable component of the simulated blood, the gelling agent causes the chitosan to desolubulize, polymerize, complex, precipitate and/or cross-link to form a semi-solid or solid mass of chitosan. It is the formation of the mass of semi-solid or solid chitosan which thus simulates blood clotting in response to the physical contact between the simulated hemostatic component and the simulated blood.
Preferred gelling agents for use in the simulated hemostatic dressing component include, for example, sodium tripolyphosphate (NaTPP), β-glycerophospate, sodium bicarbonate, sodium carbonate and Rose Bengal. Sodium tripolyphosphate is preferred. When the simulated hemostatic component is in the form of a simulated hemostatic dressing comprising a fabric substrate carrying the gelling agent, the gelling agent will preferably be present on and/or in the fabric substrate in an amount of between about 45 wt. % to about 75 wt. %, for example between about 60 wt. % to about 70 wt. %, based on the weight of the fabric substrate.
The fabric substrate employed in a simulated hemostatic dressing embodiment may be formed of virtually any synthetic and/or natural fiber and/or filament material and may be in the form of a woven or non-woven textile structure. In preferred embodiments, the fabric substrate is a relatively loosely woven gauze formed of filaments or yarns comparable to commercially available hemostatic dressing products. Suitable filaments and/or yarns that may be employed to form the fabric substrate include, but are not limited to, polyester, nylon, rayon and cotton. Blends of such filaments and yarns may also be employed if desired.
A binder may optionally be employed to suitably bind the simulated hemostatic agent to the fabric substrate. Suitable binders include, for example, agarose, powdered gelatin (Type A and/or Type B) and methyl cellulose. One or more than one binder may be mixed with the simulated hemostatic agent and applied onto the fabric substrate. Alternatively the binder may be applied onto the fabric substrate prior or subsequent to the application of the simulated hemostatic agent. For example, according to one embodiment, sodium tripolyphosphate may be applied onto the fabric substrate, followed by the application of a gelatin binder to the substrate.
The gelling agent and, if employed, the binder may be applied to the fabric substrate in any suitable manner. For example, the gelling agent and optional binder may be dissolved in a suitable solvent (preferably water) and applied to the fabric substrate by dipping, padding, spraying, roll-coating or like techniques. By way of example, when NaTPP is employed as a gelling agent, it may be applied onto the fabric substrate as a 20 wt. % solution of NaTPP by either spraying the solution onto the fabric substrate or submersing the fabric substrate into the solution. Subsequent drying of the thus NaTPP-treated fabric substrate will leave a dried solid residue of the NaTPP which is then capable of gelling the simulated blood component when brought into contact therewith.
The present invention will be further understood by reference to the following non-limiting Examples.
Different simulated blood formulations as identified in Table 1 below were prepared by combining (1) a base chitosan liquid, (2) colorant(s) and optionally (3) other additives. In each example, commercially available grades of chitosan having a percent deacetylation value (% DA) of between about 70% to about 80% and having molecular weight between about 50,000 Da and 500,000 Da were employed. Some chitosan variants were further deacetylated by stirring the chitosan in 120° C. 50% aqueous sodium hydroxide under nitrogen for 2.5 hours. The further deacetylated chitosan was thereafter filtered and recovered as a powder before preparing the base chitosan liquid. A chitosan liquid was formed by adding a chitosan variant to an acidic aqueous medium (i.e., acetic acid). In certain instances, the chitosan liquid was autoclaved under autoclaving conditions of 121° C., 15 psi for either 15 minutes or 75 minutes. The following summarizes the base chitosan liquids that were used in the simulated blood formulations of this Example 1:
- LMW=Commercial low molecular weight chitosan with no further deacetylation and no autoclaving of the chitosan liquid
- aLMW=Commercial low molecular weight chitosan with no further deacetylation but autoclaving of the chitosan liquid for 15 minutes
- aDALMW=Commercial low molecular weight chitosan with further deacetylation and autoclaving of the chitosan liquid for 15 minutes
- a75LMW=Commercial low molecular weight chitosan with no further deacetylation but autoclaving of the chitosan liquid for 75 minutes
- DAMMW=Commercial medium molecular weight chitosan further deacetylated and no autoclaving of the chitosan liquid
- a75DAMMW=Commercial medium molecular weight chitosan further deacetylated with autoclaving of the chitosan liquid for 75 minutes
| | | Acetic Acid | |
| | Concentration | Concentration | Colorant |
| # | type | (%) | (M) | Type and concentration |
|
| B1-1 | LWM | 2% | 0.1 | — |
| B1-2 | LMW | 1% | 0.05 | 6.25 mg/mL Alizarin crimson pigment |
| B1-3 | aLMW | 1% | 0.05 | 6.12 mg/mL Aluminum Lake FD&C red #40 |
| B2-1 | aLWM | 1.5 | 0.075 | 5.00 mg/mL Alizarin crimson pigment |
| B2-2 | aLWM | 1.5 | 0.075 | 5.00 mg/mL Jacquard red acid dye |
| B2-3 | aLWM | 1.5 | 0.075 | 5.00 mg/mL Jacquard Procion MX red |
| | | | reactive cold water dye |
| B2-4 | aLMW | 1.5 | 0.075 | 25% Concentrated natural cherry juice |
| B3-1 | LWM | 1.5 | 0.075 | 25% 4x concentrated natural cherry juice |
| B3-2 | LWM | 1.5 | 0.075 | 6.25 mg/mL erythrosine B |
| B3-3 | LWM | 1.5 | 0.075 | 5.00 mg/mL Rose Bengal |
| B3-4 | LMW | 1.5 | 0.075 | 10.0 mg/mL carminic acid |
| B3-5 | aLMW | 1.5 | 0.075 | 25% 4x concentrated natural cherry juice |
| B3-6 | LMW | 1.5 | 0.1 | 25% 2x concentrated natural cherry juice |
| B3-7 | aLMW | 1.16 | 0.058 | 2.72 mg/mL Alizarin crimson pigment |
| | | | 0.64 mg/mL Venetian red pigment |
| | | | 1.28 mg/mL Lac dye pigment |
| | | | 7.25% 4x concentrated natural cherry juice |
| B4-1 | aLWM | 1.6 | 0.078 | 3.9 mg/mL Alizarin crimson pigment |
| | | | 2.4 mg/mL Venetian red pigment |
| | | | 0.39 mg/mL Lac dye pigment |
| | | | 1.57 mg/mL Pthalo blue pigment |
| B4-2 | aLWM | 1.0 | 0.050 | 5.0 mg/mL Alizarin crimson pigment |
| | | | 1.0 mg/mL Venetian red pigment |
| | | | 1.0 mg/mL Pthalo blue pigment |
| B4-3 | aLWM | 1.1 | 0.053 | 4.1 mg/mL Alizarin crimson pigment |
| | | | 0.86 mg/mL Venetian red pigment |
| | | | 0.51 mg/mL Lac dye pigment |
| | | | 0.60 mg/mL Pthalo blue pigment |
| | | | 2.9% 4x concentrated natural cherry juice |
| B4-4 | aLMW | 0.60 | 0.030 | 3.0 mg/mL Alizarin crimson pigment |
| | | | 0.60 mg/mL Venetian red pigment |
| | | | 0.60 mg/mL Pthalo blue pigment |
| | | | 40% 4x concentrated natural cherry juice |
| B4-5 | aDA- | 1.2 | 0.060 | 6.0 mg/mL Alizarin crimson pigment |
| LMW | | | 1.2 mg/mL Venetian red pigment |
| | | | 40% 4x concentrated natural cherry juice |
| B4-6 | aLMW | 1.0 | 0.067 | 6.7 mg/mL Alizarin crimson pigment |
| | | | 33% 2x concentrated natural cherry juice |
| B4-7 | aDA- | 1.0 | 0.067 | 6.7 mg/mL Alizarin crimson pigment |
| LMW | | | 33% 2x concentrated natural cherry juice |
| B5-1 | a75LWM | 2.0 | 0.1 | 13 mg/mL Alizarin crimson pigment |
| | | | 2.8 mg/mL Venetian red pigment |
| B5-2 | a75LWM | 1.5 | 0.075 | 2.0 mg/mL Alizarin crimson pigment |
| | | | 1.4 mg/mL Venetian red pigment |
| | | | 25% 2x concentrated natural cherry juice |
| B5-3 | a75LMW | 1.5 | 0.075 | 2.0 mg/mL Alizarin crimson pigment |
| | | | 1.4 mg/mL Venetian red pigment |
| | | | 0.78 mg/mL Quinacridone red pigment |
| | | | 25% 2x concentrated natural cherry juice |
| B5-4 | a75LMW | 2.0 | 0.1 | 2.7 mg/mL Alizarin crimson pigment |
| | | | 1.8 mg/mL Venetian red pigment |
| | | | 1.0 mg/mL Quinacridone red pigment |
| B5-5 | aLMW | 1.0 | 0.05 | 5.0 mg/mL Alizarin crimson pigment |
| | | | 1.0 mg/mL Venetian red pigment |
| | | | 50% 4x concentrated natural cherry juice |
| B5-6 | DA-MMW | 1.5 | 0.075 | 25% 4x concentrated natural cherry juice |
| B5-7 | DA-MMW | 1.5 | 0.075 | 2.0 mg/mL Alizarin crimson pigment |
| | | | 1.4 mg/mL Venetian red pigment |
| | | | 0.78 mg/mL Quinacridone red pigment |
| | | | 25% 2x concentrated natural cherry juice |
| B5-8 | DA-MMW | 2.0 | 0.1 | 2.7 mg/mL Alizarin crimson pigment |
| | | | 1.8 mg/mL Venetian red pigment |
| | | | 1.0 mg/mL Quinacridone red pigment |
| B6-1 | a75LMW | 1.5 | 0.075 | 25% 2x concentrated natural cherry juice |
| B6-2 | a75DAM | 2.0 | 0.1 | 2.7 mg/mL Alizarin crimson pigment |
| MW | | | 1.8 mg/mL Venetian red pigment |
| | | | 1.0 mg/mL Quinacridone red pigment |
| B6-3 | aDALMW | 0.71 | 0.036 | 3.6 mg/mL Alizarin crimson pigment |
| | | | 0.71 mg/mL Venetian red pigment |
| | | | 36% 4x concentrated natural cherry juice |
| | | | 28% glycerol |
| B6-4 | a75LMW | 1.1 | 0.054 | 1.4 mg/mL Alizarin crimson pigment |
| | | | 0.89 mg/mL Venetian red pigment |
| | | | 0.56 mg/mL Quinacridone red pigment |
| | | | 18% 2x concentrated natural cherry juice |
| | | | 28% glycerol |
| B6-5 | aLMW | 1.1 | 0.054 | 18% 4x concentrated natural cherry juice |
| | | | 28% glycerol |
| B6-6 | a75LMW | 1.4 | 0.071 | 1.9 mg/mL Alizarin crimson pigment |
| | | | 1.2 mg/mL Venetian red pigment |
| | | | 0.71 mg/mL Quinacridone red pigment |
| | | | 28% glycerol |
| B6-7 | a75LMW | 2.0 | 0.1 | 2.7 mg/mL Alizarin crimson pigment |
| | | | 1.8 mg/mL Venetian red pigment |
| | | | 1.0 mg/mL quinacridone red pigment |
| | | | 1.6 mg/mL methyl cellulose |
| B6-8 | a75LMW | 2.0 | 0.1 | 2.7 mg/mL Alizarin crimson pigment |
| | | | 1.8 mg/mL Venetian red pigment |
| | | | 1.0 mg/mL Quinacridone red pigment |
| | | | 3.3 mg/mL methyl cellulose |
| B6-9 | a75LMW | 1.5 | 0.1 | 2.7 mg/mL Alizarin crimson pigment |
| | | | 1.8 mg/mL Venetian red pigment |
| | | | 1.0 mg/mL Quinacridone red pigment |
| | | | 12.5 g/mL Oenin chloride |
|
Different variants of simulated hemostatic dressings were prepared as identified in Table 2 below. In general, the gelling agent was absorbed either directly from aqueous solution or from a binder material solution into common commercially available medical gauze products. The gelling agents include compounds that (1) neutralize the acidic solvent to create a neutral or slightly basic solution in which chitosan is no longer soluble, (2) cause chitosan to precipitate out of the dilute acid solution via ionic complex formation and/or (3) crosslink the chitosan into a highly hydrated clot-like gel. Following absorption of the hemostatic agent, the simulated hemostatic dressings were allowed to dry as noted.
| TABLE 2 |
| |
| Dressing material | Hemostatic agent |
| # | Brand | Material | material | Drying method |
|
| D1-1 | Triangular | Unknown | 20% NaTPP | 75° C. oven |
| splint |
| bandage |
| D1-2 | CVS sterile | Rayon- | 20% NaTPP | 75° C. oven |
| gauze pad | polyester |
| D1-3 | CVS sterile | Rayon- | 5-7 mL 10% Na-TPP | 45 min in 75° C. oven; |
| gauze pad | polyester | | ambient overnight |
| D1-4 | CVS sterile | Rayon- | 5-7 mL 50/50 10% Na- | 45 min in 75° C. oven; |
| gauze pad | polyester | TPP/45% β-GP | ambient overnight |
| D1-5 | CVS sterile | Rayon- | 5-7 mL 50/50 1.5M sodium | 45 min in 75° C. oven; |
| gauze pad | polyester | bicarbonate/45% β-GP | ambient overnight |
| D1-6 | CVS stretchy | Rayon- | 5-7 mL 10% Na-TPP | 45 min in 75° C. oven; |
| rolled gauze | polyester | | ambient overnight |
| D1-7 | CVS stretchy | Rayon- | 5-7 mL 50/50 10% Na- | 45 min in 75° C. oven; |
| rolled gauze | polyester | TPP/45% β-GP | ambient overnight |
| D1-8 | CVS stretchy | Rayon- | 5-7 mL 50/50 1.5M sodium | 45 min in 75° C. oven; |
| rolled gauze | polyester | bicarbonate/45% β-GP | ambient overnight |
| D1-9 | CVS extra | Rayon- | 5-7 mL 10% Na-TPP | 45 min in 75° C. oven; |
| absorbent | polyester | | ambient overnight |
| gauze roll |
| D1-10 | CVS extra | Rayon- | 5-7 mL 50/50 10% Na- | 45 min in 75° C. oven; |
| absorbent | polyester | TPP/45% β-GP | ambient overnight |
| gauze roll |
| D1-11 | CVS extra | Rayon- | 5-7 mL 50/50 1.5M sodium | 45 min in 75° C. oven; |
| absorbent | polyester | bicarbonate/45% β-GP | ambient overnight |
| gauze roll |
| D1-12 | Kerlix gauze | Cotton | 5-7 mL 10% Na-TPP | 45 min in 75° C. oven; |
| roll | | | ambient overnight |
| D1-13 | Kerlix gauze | Cotton | 5-7 mL 50/50 10% Na- | 45 min in 75° C. oven; |
| roll | | TPP/45% β-GP | ambient overnight |
| D1-14 | Kerlix gauze | Cotton | 5-7 mL 50/50 1.5M sodium | 45 min in 75° C. oven; |
| roll | | bicarbonate/45% β-GP | ambient overnight |
| D2-1 | CVS sterile | Rayon- | 3 mL 3% powdered | ambient overnight |
| gauze pad | polyester | gelatin/5% NaTPP |
| D2-2 | CVS sterile | Rayon- | 3 mL 3% bovine Type B | ambient overnight |
| gauze pad | polyester | gelatin/5% NaTPP |
| D3-1 | CVS sterile | Rayon- | 0.44 mL/in215% NaTPP | NaTPP dried at 70° C. for |
| gauze pad | polyester | | 90 min |
| D3-2 | CVS sterile | Rayon- | 0.44 mL/in215% NaTPP | NaTPP dried at 70° C. for |
| gauze pad | polyester | 0.33 mL/in23% Type B | 90 min |
| | | gelatin | gelatin dried in ambient |
| | | | overnight |
| D3-3 | CVS sterile | Rayon- | 0.44 mL/in215% NaTPP | NaTPP dried at 70° C. for |
| gauze pad | polyester | 0.66 mL/in23% Type B | 90 min |
| | | gelatin | gelatin dried in ambient |
| | | | overnight |
| D3-4 | CVS sterile | Rayon- | 0.44 mL/in215% NaTPP | NaTPP dried at 70° C. for |
| gauze pad | polyester | 0.33 mL/in212% Type B | 90 min |
| | | gelatin | gelatin dried in ambient |
| | | | overnight |
| D3-5 | CVS sterile | Rayon- | 0.44 mL/in215% NaTPP | NaTPP dried at 70° C. for |
| gauze pad | polyester | 0.66 mL/in212% Type B | 90 min |
| | | gelatin | gelatin dried in ambient |
| | | | overnight |
| D3-6 | CVS sterile | Rayon- | 0.56 mL/in215% NaTPP/20 | Dried at 70° C. for 1 hour |
| gauze pad | polyester | mg/mL Rose Bengal |
| D4-1 | CVS sterile | Rayon- | 0.67 mL/in220% NaTPP | NaTPP dried at 70-75° C. |
| gauze pad | polyester | | for 20 min |
| D4-2 | CVS sterile | Rayon- | 0.67 mL/in220% NaTPP | NaTPP dried at 70-75° C. |
| gauze pad | polyester | 0.33 mL/in23% Type A | for 20 min |
| | | gelatin | gelatin dried in ambient |
| | | | overnight |
| D5-1 | CVS sterile | Rayon- | 0.61 mL/in220% NaTPP in | Dried at 75° C. in two 10 |
| gauze pad | polyester | deionized water | min increments followed by |
| | | | 1 hour air dry |
| D6-1 | CVS sterile | Rayon- | 0.28 mL/in21.5 mg/mL | Dried at 75° C. followed by |
| gauze pad | polyester | methyl cellulose/150 mg/mL | 1 hour air dry |
| | | NaTPP in deionized water |
|
| NaTPP: sodium tripolyphosphate |
| β-GP: β-glycerophosphate |
Different variants of simulated hemostatic powders were prepared as identified in Table 3 below. Gelling agent powders were either used as-received or were mixed into a slurry with chitosan, dried and collected into a powder.
| TABLE 3 |
|
| # | Material(s) | Description |
|
| P1-1 | NaTPP | As-received powder |
| P1-2 | β-GP | As-received powder |
| P4-1 | NaTPP/ | 2.5 g LMW chitosan mixed with 15 mL of 15% |
| chitosan | NaTPP in deionized H2O; spread flat and |
| | dried overnight at 70° C. |
| P4-2 | NaTPP/ | 1 g HMW chitosan mixed with 15 mL of 20% |
| chitosan | NaTPP in deionized H2O; spread flat and |
| | dried overnight at 70° C. |
|
20 mL of each simulated blood sample that was investigated for quantitative color approximation were swirled vigorously and poured into a 9 cm diameter glass Petri dish. To photograph the samples, a white soft box lighting tent was used to aid in reducing reflection glare and to provide even lighting conditions. Sample dishes were placed on a piece of white, plastic-backed absorbent paper to capture any accidental spills. Photographs were taken with a Nikon D90 D-SLR camera using a remote Nikon SB-800 Speedlight flash with factory diffuser cap. The flash was placed 6 inches to the right of the Petri dish and was triggered remotely using the Nikon D90's integrated slave flash system that utilizes the SB-800 Speedlight's onboard optical sensor. The camera was set to its manual operation setting, the f-stop was set to f/5.3 and shutter speed was set to 1/40 of a second. A Nikkor AF-S DX 18-105 mm f/3.5-5.6G ED VR lens was used to capture the images. The focal length of the lens was set to 75-80 mm to capture all images. The camera's white balance settings were custom calibrated to the lighting tent by photographing the empty space and allowing the camera to set the white background as a baseline.
The images were cropped to 500×500 pixels using ADOBE® Photoshop 6 software. The Petri dish images were then masked with a green image layer containing nine 5×5 pixel square holes. Using the color sampling tool of the ADOBE® Photoshop software, a 3×3 pixel sized sample was taken from the underlying Petri dish image of the simulated blood solutions. The color sampling tool was used to assay a 3×3 pixel square and average the RGB values for the sample area. The RGB values were recorded for each of the 9 sampling areas and the values were averaged.
Once the average RGB values were established, a pure RGB color was created from the results (average values were rounded to the nearest whole number). Using ADOBE® Photoshop software, a new 500×500 pixel image was created and filled with a custom color made using the average RGB values from each simulant sample. This new, solid color recreated the average color value of the surface of the blood simulant and allowed for easy visual comparison of color ranges of simulants versus human whole blood. The RGB images were saved as BMP (Bitmap) file type to minimize data compression and color loss. The pure RGB color values of each sample tested are shown in Table 4 below. The samples are listed in order of similarity to human whole blood based on the root mean square error of the RGB values relative to those of human whole blood. The results show that the color of the simulated blood samples of the present invention compare very well to that of human whole blood.
| Human whole blood | 94 ± 9 | 37 ± 3 | 40 ± 4 | 0 |
| B5-3 | 98 ± 15 | 44 ± 7 | 43 ± 7 | 8 |
| B4-2 | 101 ± 9 | 44 ± 4 | 44 ± 4 | 10 |
| B4-6 | 67 ± 6 | 39 ± 6 | 40 ± 6 | 17 |
| B5-5 | 50 ± 5 | 40 ± 5 | 42 ± 5 | 28 |
| B4-1 | 181 ± 2 | 92 ± 10 | 105 ± 7 | 120 |
|
| RMSE = root mean square error relative to RGB values for human whole blood. |
The kinematic viscosity of simulated blood formulations and human whole blood was determined using a Cannon-Fenske 100 routine viscometer. Fluid was drawn into the viscometer and the time required for the fluid meniscus to flow through a marked chamber was recorded. 3 efflux times were recorded and averaged for each sample. Kinematic viscosity was determined by multiplying the mean efflux time in seconds by the viscometer constant. Simulated blood formulations were tested at 22° C. (viscometer constant=0.01633) and human whole blood was tested at 37° C. (viscometer constant=0.01631). The results, shown in Table 5 below, indicate that the viscosity of the simulated blood formulations compare very well to that of human whole blood, especially formulation B4-7.
| TABLE 5 |
| |
| | Mean efflux time | Kinematic viscosity |
| Sample | (seconds) | (cStokes) |
| |
|
| Human whole blood | 351 ± 6 | 5.72 |
| (37° C.) |
| B4-7 | 340 ± 5 | 5.56 |
| B5-3 | 470 ± 10 | 7.68 |
| B4-2 | 553 ± 16 | 9.03 |
| B5-5 | 832 ± 1 | 13.6 |
| B5-4 | 951 ± 10 | 15.5 |
| |
Comparative testing of the rates at which simulated blood formulations and whole blood flow through tubing was performed so as to determine the realism of simulated blood formulations when used in trauma training mannequins. A 50 mL syringe barrel was filled with either a sample of simulated blood at room temperature (20° C.) or human whole blood at human body temperature (37° C.). Human whole blood was tested at several different time points after draw to determine if “age” was a factor. A syringe barrel was attached to a 24 in length of tubing and the assembly was suspended from a clamp with the syringe barrel open to the atmosphere. The time required for 50 mL of simulated or actual human whole blood to flow though tubing of varying inner diameters ( 1/16″, ⅛″ and ¼″) was recorded. The tubing was wetted with 50 mL of simulated blood formulation or whole human blood prior to testing. Samples were run in triplicate.
The results, shown in Table 6 below, indicate that it took significantly more time for all of the simulated blood formulations to flow through the system than it did for the human whole blood, regardless of age. Of the simulated blood formulations tested in this way, the one with flow-through time closest to that of human whole blood was formulation B4-2.
| Simulated Blood Formulations | Human Whole Blood |
| Tubing ID | B3-7 | B4-1 | B4-2 | B4-5 | 4 day old | 10 day old | 23 day old |
|
| 1/16″ | 650 ± 26 | 744 ± 23 | 300 ± 6 | 596 ± 6 | 94 ± 1 | — | 144 ± 18 |
| ⅛″ | 52 ± 0 | 64 ± 2 | 26 ± 1 | 48 ± 1 | 12 ± 2 | 12 ± 0 | 14 ± 1 |
| ¼″ | 2 ± 1 | 3 ± 0 | 1 ± 0 | 2 ± 0 | 1 ± 0 | — | 1 ± 0 |
|
| Values are means ± standard deviations (n = 3) |
Swatches of 50/50 Nylon/Cotton universal camouflage Army Combat Uniform (ACU) fabric were used to test the staining properties of several of simulated blood formulations. This study was designed to mimic spilling of blood simulant on the uniform of a trainee during use. Prior to testing, the ACU fabric was washed once in a household washing machine on a cold/cold standard cycle with 50 mL of WISK® High Efficiency detergent and hung dry prior to testing. Staining was tested after exposures of five minutes and 24 hours.
A 5 minute exposure staining test was carried out using 4 in.×5 in. swatches of ACU fabric. A 5 mL sample of simulated blood was placed onto each ACU fabric sample and allowed to soak in for 5 minutes. The ACU fabric swatches were then scrubbed by hand under luke-warm (25-30° C.) water for 2-3 minutes by folding them over and rubbing the ACU fabric together followed by soaking the swatch in the running water and wringing it out by hand. No detergent was used to clean the ACU fabric. The swatch samples were hung on a line in the laboratory and were left to air dry overnight. The dried swatches were examined for staining and photographed. The results of the testing are shown in Table 7A below.
Most of the simulated blood formulations left no stain at all. Two formulations, B5-3 and B5-4, left very light stains that could only be observed in the lighter color portions of the camouflage pattern. It is unclear why B5-3 and B5-4 performed differently than the others, except that they both contained relatively high quinacridone red pigment. Formulations B6-4 and B6-6 also contained quinacridone, but were also formulated with glycerol. It is believed that glycerol may maintain higher moisture content in stained fabric and thereby aid in stain removal. The glycerol-containing formulations also appeared more like human blood when first applied to the ACU fabric.
The 24 hour exposure staining test was carried out using 8 in×8 in swatches of ACU fabric. Each ACU fabric sample was stained with 5 mL of human whole blood or blood simulant, which was then allowed to soak into the fabric for 24 hours on the benchtop. Notes and observations were made during the staining procedure to compare the interaction of the blood simulants with the ACU fabric as compared to human whole blood. After 24 hours, the ACU fabric swatches were washed in a FRIGIDAIRE® Super Capacity, Heavy Duty Tumble Action household washing machine on warm/warm 1 hour wash setting with approximately 50 mL of TIDE® High Efficiency (HE) Detergent. The washed swatch samples were hung to dry overnight. The dried swatches were examined for staining and photographed. The interaction observations and stain removal results are shown in Table 7B below.
While whole blood was laundered out completely most of the simulated blood formulations left a visible stain behind. The two blood simulants that were laundered completely were the glycerol-containing formulations, B6-3 and B6-5. In addition, the glycerol-containing formulations presented and persisted on the surface of the ACU fabric with a vibrant red color much closer to that of human whole blood than all non-glycerol containing formulations.
The tackiness or adhesive properties of several simulated blood formulations were evaluated relative to that of citrated human whole blood. Coupons made from glass, wood, polyurethane rubber and medical silicone were lowered vertically into blood simulant or human whole blood (at 37° C.) and immersed at a 5 cm depth for 30 seconds. The coupons were quickly removed and any solution that dripped from the coupon was collected and weighed. Samples were tested in triplicate.
The results show that citrated human whole blood was significantly more tacky than all of the blood simulant formulations tested. Although the differences between most means were not statistically significant, the trends are interesting. Formulation B5-4, which tended to be the most tacky formulation tested, contained only pigments. Formulations B5-4 and B6-6 had identical chitosan and pigment packages, but B6-6 contained glycerol and B5-4 did not. Formulations B6-7 and B6-8 incorporated methyl cellulose and the chitosan was present at a higher concentration. Interestingly, although both glycerol and methyl cellulose were added, in part, to increase the stickiness of the blood simulants, they actually had the opposite effect. Formulation B3-7 contained several pigments and 4× concentrated natural cherry juice and was generally intermediate in tackiness between B5-4, which tended to be more tacky and B6-6, B6-7 and B6-8, which tended to be less tacky. Visual inspection of the test coupons suggested only slight qualitative differences in the interaction between the glycerol- or methyl cellulose-containing prototype blood simulants and the different materials.
Simulated blood for trauma training modules must maintain its properties when inventoried and stored. Samples of blood simulant formulations B4-1, B4-2, B4-5 and B5-5 were selected for “accelerated” shelf life testing that consisted of regular cycling between high and low temperature extremes. 30 mL of each solution were placed in a small glass bottle and sealed to prevent evaporation. The samples were placed in a 50° C. oven and were moved to a 4° C. refrigerator after 24 hours. The samples were alternated between 50° C. and 4° C. every 24 hours during the week and were stored at room temperature over the weekends. The test was conducted for four weeks.
The samples were photographed before testing began and at the conclusion of the four week study. The samples were also observed when transported from the refrigerator to the incubator. Initially, all formulations exhibited some pigment settling, but the pigment could be re-suspended easily with vigorous swirling. No color loss was observed despite the pigment settling. After 2 weeks, formulations B4-5 and B5-5 become more viscous. After 4 weeks, both formulations were “gelatinous,” having the consistency of jelly. Both of these formulations contained concentrated cherry juice. Formulations B4-1 and B4-2, which did not contain cherry juice extract, did not undergo an increase in viscosity during the four week test.
Static testing of various combinations of simulated blood formulation and simulated hemostatic dressing was performed. Static testing involved immersing 3 in.×1 in. test strips of the simulated hemostatic dressing materials into a simulated blood formulation. The test strips of dressing materials were observed to determine the formation of gel “coagulum.” It was observed that dressings impregnated with sodium tripolyphosphate (Na-TPP) provided the most realistic “clot” formation.
Testing of potential simulated hemostatic powder was conducted using an uncolored stock solution of 2% LMW chitosan in 0.1 M acetic acid. 50 mg of sodium tripolyphosphate (Na-TPP) powder (simulated hemostatic powder P1-1) was added to approximately 5 mL of the LMW chitosan solution in a glass Petri dish. Without active mixing, the sodium tripolyphosphate powder did not readily dissolve or disperse into the chitosan solution after five minutes. Instead, a small ring of crosslinked gel formed around the edge of the powder. When the sodium tripolyphosphate salt was mixed into the chitosan with a spatula, the powder began to cross-link the chitosan and form a hazy, opaque gel.
The same experiment was performed using β-glycerophosphate powder (P1-2). The β-glycerophosphate was added on top of approximately 5 mL LMW chitosan solution. When the salt was mixed into the chitosan solution, crosslinking was not rapid. The solution was left for 10 minutes but no cross-linked gels appeared to form. The mixture was slightly hazy but did not form a white gel as with the sodium tripolyphosphate.
Two additional hemostatic powder simulants were tested that consisted of sodium tripolyphosphate/chitosan powder blends. The first hemostatic powder simulant (P4-1) was prepared by mixing 2.5 g of stock low molecular weight chitosan powder with 15 mL of 15% sodium tripolyphosphate in deionized water. The second simulated hemostatic powder (P4-2) was prepared by mixing 1 g of stock high molecular weight chitosan flakes with 15 mL of 20% sodium tripolyphosphate in deionized water. Both slurries were spread flat onto a glass Petri dish and dried overnight at 70° C.
After the slurries had dried, they were scraped from the glass dishes. The high molecular weight P4-2 flakes were easier to remove than the low molecular weight P4-1 powder. Both samples appeared to have a large amount of sodium tripolyphosphate salt settled on the bottom of the dish, creating a lower layer of salt and an upper layer of chitosan. The layers were bound to each other well.
To test the clotting ability of simulated hemostatic powders P4-1 and P4-2, 0.4 g of each was sprinkled on top of approximately 30 mL of 2% deacetylated low molecular weight chitosan in 0.1 M acetic acid. The powders were allowed interact statically with the chitosan solution for 10 minutes. After 10 minutes both powders had formed a thick, white gel layer across the top of the chitosan solution. When the gels were lifted up, both exhibited good cohesion and were removed in one large piece.
A system to test blood simulant flow through treated gauze under pressure included a 60 mL syringe held vertically with a clamp and ring stand. A 24 in long piece of ⅛ in inner diameter silicone tubing was attached to the nozzle of the syringe. The barb fitting of a custom pressure plug was attached to a pressurized tank of nitrogen. Using a plastic hemostat to pinch the ⅛ in tubing closed, 25-50 mL of blood simulant was added to the open syringe. The syringe was either left open or the pressure plug was inserted into the open end of the syringe and the nitrogen tank was opened. When the pressure plug was used, an inline pressure regulator was used to maintain the nitrogen gas pressure entering the syringe at 2 psi.
One or two plys of simulated dressing D5-1 or untreated gauze measuring 1.5 in×1.5 in were folded over the end of the ⅛ in tubing and secured with a zip tie. When the plastic hemostat was released, the pressurized blood simulant flowed through the tubing (at approximate human arterial pressure when set to 2 psi) and interacted with the treated or untreated dressing at the end of the tube.
The results of the flow testing are summarized in Table 8 below. When tested under 2 psi pressure, 50 mL of blood simulant B3-7 drained rapidly through both the untreated gauze and dressing D5-1, with little or no difference. When the untreated gauze samples were examined, however, they had not absorbed much of the blood simulant and what was absorbed was less viscous and spread over most of the gauze surface. When the D5-1 hemostatic dressing simulant was examined, a much more concentrated gel had formed on the dressing surface.
When the blood simulant solution was gravity fed (open to atmosphere), performance differences were easier to discern. When an untreated piece of gauze was placed over the drain tube, the 50 mL volume of B3-7 emptied in 27 seconds. When simulated hemostatic dressing D5-1 was used, the 50 mL volume emptied in 1 minute 24 seconds. After 20 seconds, the flow through D5-1 slowed to a drip whereas the untreated gauze drained consistently with no slowing of flow rate. Again, the blood simulant did not adhere to the untreated gauze whereas a larger gel had formed on the surface of the D5-1 dressing material.
The next two experiments involved blood simulants B3-1 and B5-6, which are identical except for the molecular weight and degree of deacetylation of the chitosan (B3-1 has non-deacetylated low molecular weight chitosan and B5-6 has deacetylated medium molecular weight chitosan). When 35 mL of each was allowed to drain under 2 psi, it took 46 seconds for the B3-1 and 11 seconds for the B5-6. When the D5-1 dressing material was examined, there was a very small piece of dark red gel “clot” formed from B3-1 and only a very thin gel layer from B5-6.
The next set of experiments was similar. When 35 mL of blood simulant B5-3 (75 minute autoclaved low molecular weight chitosan) was tested against 2 plys of D5-1 under 2 psi, flow through the dressing material slowed after 30 seconds and stopped after 2-3 minutes. Although 2 psi pressure was maintained behind the solution for 5 minutes, no further flow was noted. Small gels were observed in the catch beaker. A large, gel “clot” formed on the outer surface of the gauze while it was still attached to the tubing and a large gel “clot” was also formed on the inside surface of the D5-1 dressing material. The gel was large enough to effectively “glue” the two pieces of gauze together. When simulated blood formulation B5-7 was used (B5-7 is identical to B5-3, except with deacetylated medium molecular weight chitosan) the result was nearly identical except that the “clots” were less substantial than with B5-3.
In a final test, simulated blood formulation B5-4 (75 minute autoclaved LMW chitosan) and B5-8 (deacetylated MMW chitosan), which had higher chitosan and acetic acid concentrations than the previous four blood simulants, were investigated. When 25 mL of B5-4 was used, the solution evacuated the syringe in 1 min and 10 seconds. No stoppage of flow was observed. Very large gels formed in the catch beaker. Gel “clots” formed on the outer surface of the gauze while it was still attached to the tubing. A medium sized gel “clot” formed on the inside surface of the treated gauze at the site where the tubing directly touched the gauze. The large gel that formed in the catch beaker was very robust and dense but was light pink in color. When 25 mL of B5-8 was used, flow through the D5-1 dressing material slowed after 30 seconds and stopped after 2-3 minutes. 2 psi pressure was maintained behind the solution for 5 minutes, but no further flow was noted. Approximately half of the solution flowed through the system before flow was stopped. Small gels were observed in the catch beaker and a medium sized gel “clot” formed on the inside surface of the dressing at the site where the tubing touched it directly. The gel was more localized than with the B5-4 simulant.
Simulated blood formulations B5-4, B6-1 and B6-2 were evaluated for performance characteristics using reservoirs, pumping systems and simulated wound beds representative of those used in the TRAUMA F/X™ simulator (Kforce Government Solutions, Inc.).
Initial testing of the simulated blood formulations included running 500 mL of blood simulant B5-4 through a circulating flow loop powered by an electronically regulated diaphragm pump system. The temperature of the pump was monitored with an infrared thermometer to observe any overheating conditions. A second system circulating a standard blood simulant (Kforce Government Solutions, Inc.) was run at the same time. Although simulant B5-4 was more viscous than the standard commercial blood simulant, it flowed through the system easily during the course of the experiment. The external temperature of the diaphragm pump used with the simulant B5-4 increased to 32° C. An identical pump used with a water-based solution containing remnants of the standard blood simulant was also increased to 30-32° C.
500 mL of blood simulant B5-4 was loaded into a reservoir and fed into a femoral artery hemorrhage mannequin model (Kforce Government Solutions, Inc.) using a pumping system. The wound bed was allowed to fill with blood simulant for approximately 10 seconds before two 3 in×3 in pieces of simulated hemostatic dressing D5-1 were placed inside the wound directly against the silicone tube feeding the simulated blood into the model. Direct pressure was applied to the wound to simulate battlefield treatment of a large hemorrhage. Blood simulant flowed out of the wound area. The simulant looked quite realistic, although the red color was not quite as bright red as whole blood. As pressure was applied to the wound, flow was reduced and the pumping mechanism, by design, automatically shut off. If pressure was released even slightly, the flow would resume.
After approximately 2 minutes, gelatinous clots could be seen forming around the gauze and flowing off of the wound model onto the table. After approximately 5 minutes the treated gauze was saturated with gel “clots”. Gel “clots” adhered to the silicone “skin” of the model as well as to the gauze and hands of the operator. The gels were slightly pink and lighter in color than the unreacted simulant. The blood simulant was easily cleaned off the silicone model between tests by rinsing with water and wiping with baby wipes. The experiment was repeated with identical results.
Blood simulant B6-2, 3 pieces of 3 in×3 in D5-1 simulated hemostatic dressing and 1 package of 4.5 inches wide×4.1 yards long compressed gauze (H&H PriMed™ Compressed Gauze, H&H Associates, Inc., Ordinary, Va.) were used to conduct a “wound packing” test. After the pieces of D5-1 simulated hemostatic dressing were applied directly to the blood simulant supply tube, the untreated compression gauze was used to fully pack the simulated wound. The compression gauze was packed into the wound and pressure was applied to the hemorrhage model to mimic wound packing to stanch hemorrhage in the field. Blood simulant flow was reduced, but not stopped, throughout the 5 minute test. Large “clots” flowed over the sides of the simulated wound model and formed on the surface of the gauze. Because the treated gauze was so compacted into the wound, gel “clot” formation was pressed into the treated and untreated gauze forming a large, solid lump of gel and gauze. The gauze was very dense and hard to the touch. The outside edge of the treated gauze that was in contact with the blood simulant supply tubing was coated with a thick layer of caked pink gel “clot”.
The “wound packing” test was repeated with simulated blood formulation B5-4, three 3 in×3 in pieces of simulated hemostatic dressing D5-1, one package of compressed gauze and direct application of pressure as described above. Gel formation in the “wound packing” model with formulation B5-4 was qualitatively identical to that observed with B6-2.
Another “wound packing” test was performed with simulated blood formulation B6-1. Formulation B6-1 is less viscous than both formulations B5-4 and B6-2, and it flowed quickly from the simulated wound bed. The formulation B6-1 had a brown tint and was much darker and more transparent than formulations B5-4 and B6-2. Gel “clot” formation was much less obvious during the testing, probably due to the lower chitosan concentration. A small amount of gel flowed out of the wound bed and a much smaller amount of gel formed on the surface of the D5-1 simulated hemostatic dressing. The gel “clots” that formed were brown in color.
Primary skin irritation studies were performed to assess the irritant and/or corrosive effects of the simulated blood formulations when given as a single dermal administration to white New Zealand rabbits. The study was designed to mimic spilling of blood simulant on the skin of a trainee during use. The design was aggressive, however, in that the blood simulant was not washed off in a time period that would be expected in a training scenario.
The three blood simulant formulations that were investigated in this primary skin irritation study were B3-1, B5-3 and B5-4. Whereas B3-1 only contains chitosan, acetic acid and cherry juice extract, B5-3 and B5-4 contain alizarin crimson, venetian red and quinacridone red pigments and are therefore more likely to be skin irritants. B5-3 also contains cherry juice extract.
Three groups of rabbits, with 3 animals per group, received 0.5 mL doses of the appropriate test or control materials as single dermal applications per test site. There were two test sites per material per animal. One of the test sites for each material was abraded by utilizing the back of a no. 40 clipper blade. The abrasions were sufficiently deep to penetrate the stratum corneum, but not to disturb the derma. The other test site for each material remained intact. The doses were held in contact with the skin under a semi-occlusive binder for an exposure period of 4 hours. Following the exposure period, the binder was removed and the remaining test materials were wiped from the skin using gauze moistened with deionized water followed by dry gauze. Test sites were subsequently examined and scored for dermal irritation for up to 7 days following patch removal.
Irritation was not observed at the abraded sites following dermal administration of blood simulant B3-1. Very slight erythema was observed at 1 intact test site at the 24 and 48 hour scoring intervals. Complete resolution of irritation occurred by the 72 hour scoring interval. No additional dermal changes were noted at the intact or abraded test sites.
Dermal administration of blood simulant B5-3 resulted in very slight erythema at a single intact site at the 1 hour scoring interval. Irritation was not observed at the abraded sites or remaining intact sites at the 1 hour scoring interval. At the 24 hour scoring interval, irritation was noted at all intact and abraded sites, and ranged from very slight to well-defined erythema. Complete resolution of irritation occurred by the Day 7 scoring interval. No additional dermal changes were noted at the intact and abraded test sites.
Administration of blood simulant B5-4 produced very slight to well-defined erythema and very slight edema by the 1 hour scoring interval. Complete resolution of irritation occurred by the day 7 scoring interval. Additional dermal observations included red staining of the test sites. The staining did not affect the ability to score the test sites.
Sodium dodecycl sulfate (SDS) and glycerol were included in the study as positive and negative controls for skin irritation, respectively. Dermal administration of 25% SDS solution resulted in slight to well-defined erythema at the intact and abraded test sites in all animals beginning at the 1 hour scoring interval and continuing through the final observation interval for the groups. Erythema increased to maximized erythema based on the presence of blanching within the test sites covering greater than 50% of the sites. Additional dermal changes including very slight to slight edema, superficial lightening, and desquamation were noted as the study progressed through the Day 7 scoring interval. No irritation was observed at either the intact or abraded glycerol control sites.
Dermal administration of blood simulant formulation B3-1 resulted in the least irritation when compared to formulations B5-3 and B5-4. The irritation resulting from administration of the B5-3 and B5-4 was comparable, although the irritation induced by B5-3 was slightly less than that of B5-4. B5-4 was the only blood simulant tested that resulted in staining of the test sites. The irritation resulting from the administration of 25% SDS solution demonstrated that the study was conducted in a manner that would indicate potential irritation. All blood simulant solutions had less irritation than the SDS-treated sites, as the irritation in the SDS treated sites was still present through day 7 on the animals remaining on study until that interval. Glycerol served as the negative control and resulted in no irritation. This allowed comparison of the blood simulant solutions to a known non-irritating material, and showed that the irritation induced by the blood simulant solutions was minimal and well tolerated by the animals. These results suggest that the simulated blood formulations are unlikely to be skin irritants, especially if they are washed off in a timely fashion.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope thereof.