Medical Aspects of Chemical Warfare (2008) - The Black Vault

Decontamination of Chemical Casualtiessetting is often referred to as emergency decontamination,self decontamination, or buddy rescue. The firstdecontamination in the civilian setting may not occuruntil a fire department decontamination unit arrives.Patient operational decontamination might not readilyapply in the civilian setting because private ambulanceservices may refuse to accept contaminated patientsand civilian patients do not have IPE.Individuals who escape the scene of the releasebefore the arrival of the first responders may manageto access transportation while still in contaminatedclothing. This was the case during the Tokyo subwaysarin attack, in which many victims either walkedor took taxis to hospitals. 4 Otherwise, contaminatedindividuals must be moved to a decontaminationstation established by the fire department or set up ata hospital for patient thorough decontamination. Decontaminationstations near the incident site are oftenreferred to as mass casualty decontamination stationsor gross decontamination areas. 2,5 Victims might alsobe moved to a water source, such as a hose or shower,for buddy decontamination. Because fleeing casualtiesmight bypass decontamination, or responding firedepartments may fail to perform adequate decontamination,it is important that every hospital has thecapability of establishing its own patient thoroughdecontamination area outside its entrance.Since the events of September 11, 2001, military andcivilian agencies have sought to improve their patientdecontamination capabilities. 6 Industry has respondedwith a wide array of decontamination equipment andmaterials for simplifying this process. Civilian andmilitary sectors are now much better prepared for thechallenges of patient decontamination.Action of Chemical Agents on the SkinCrone described the function of the skin as a barrierand the possible effect of chemical agents on tissues: 7,8The skin consists of a number of layers of living cellsof varied function bounded on the outside by a thinlayer of dead cells, the stratum corneum. This layeris the main diffusion barrier to the entry of foreignsubstances. The blood supply to the skin does notreach directly to the epidermis. Therefore, a liquidcontacting the skin surface first has to penetrate thestratum corneum, and then diffuse through the largelyaqueous medium of the cell layers to the nearest bloodcapillaries, from whence it is carried round the body.There is opportunity for a chemical to be bound tothe outer skin layers, so that further delay and storagecan occur. 7Chemicals that act directly on the skin, such assulfur mustard, need little penetration for their effectsto begin; they act directly on the integrity of theskin cells. This same process occurs with other highlyreactive chemicals such as acids and alkalis. Moresystemically acting chemicals, such as nerve agents,may need to cross the skin barrier before they can affectbody systems. Generalizations about the permeabilityof skin are often inadequate. 8 The skin is not a simplesystem, and its permeability depends on many factorsincluding temperature and the skin’s thickness,integrity, and hydration.The stratum corneum retains moisture and providesa barrier to outside hazards. This barrier is very effectiveagainst water-soluble chemicals. However, it ismore permeable to fat-soluble (lipophilic) chemicalsbecause of the layers of lipids in the epidermis thatunderlie and surround the keratinized dead skincells making up the stratum corneum. 8 When tracingagent progress from the surface of the skin to thebloodstream, three skin “compartments” must beconsidered: (1) the outer application layer, where theagent lies on the skin; (2) the boundary layer, wherethe agent is moving through the skin; and (3) the areawhere a dermal reservoir of agent that has diffusedinto the lipid area of the stratum corneum may form. 9Rapid decontamination seeks to prevent large dosesof agent from penetrating to the lipid area of the stratumcorneum and subsequently into the circulation.Later decontamination seeks to remove any agent thatremains on the surface of the skin.A liquid chemical warfare agent (CWA) is oftenthought to be accessible on the surface of the skin for upto 3 minutes, taking approximately 30 minutes for theagent to cross the skin barrier and enter the capillaries.Some of the hazardous agent is likely to be temporarilysequestered in the skin during this transit. Accordingto Buckley et al, 10 inappropriate skin treatments couldtheoretically aid in the dermal transit of agent, and theresulting store of hazardous agent could potentiallymake the situation worse for the victim. 10Most CWAs (particularly VX and mustard) aremoderately fat-soluble, enabling them to be absorbedthrough the stratum corneum over time. Lipid-solublechemical agents move quickly throughthe lipids surroundingthe cells in the stratum corneum and thenmore slowly into the hydrophilic (water-soluble)bloodstream.Contact time, concentration, solubility, temperature,hydration state, and physical condition of the skin areall factors that affect the absorption of agent throughthe skin’s epithelial layer. Vascularity of tissue plays an529