By Y. Thorus. University of South Carolina.
A number of citizens were killed or injured discount v-gel 30gm with amex, and there was signifcant property damage that required a considerable amount of resources to repair or rebuild buy on line v-gel. The citizens of New Orleans have relocated (many permanently) to other cities best v-gel 30gm, which efectively reduced the population of New Orleans in the short term generic v-gel 30gm overnight delivery. Criticism and investigations were launched into a number of government agencies that were involved with Hurricane Katrina, 56 ◾ Case Studies in Disaster Response and Emergency Management which revealed shortcomings in operational procedures, logistical controls, and operational planning, as well as having no efective leadership in emergency man- agement during a crisis. Items of Note Reports of widespread violence in the Superdome turned out to be exaggerated. Hurricane Rita, 2005 Stage 1 of the Disaster You are the director of a federal agency that is tasked with overseeing rescue and relief aid to areas that are afected by natural disasters. On September 20, the National Hurricane Center determines a hurricane has formed and is heading for the United States (National Weather Service, 2007). The director should begin to take an inventory of what supplies are on hand to contend with such an emergency, such as food, water, and medical supplies. In addition, the director should also begin to formulate a plan concerning how those supplies will be delivered quickly and, if it is possible, how to position some of those resources in depots close to where the hurricane may strike the coast. The director will need manpower to move the supplies and vehicles to carry the supplies to key locations. In addi- tion, the director will need temporary shelters for personnel as well as mobile generators and refrigeration units to store food and medicine that may be needed in case of an emergency. Interacting with state and local ofcials that are in the possible strike area of the hurricane is critical to determine what resources may be needed by those communi- ties. In addition, the director will need to communicate with other federal department heads to coordinate eforts on getting supplies where they will be needed the most. Stage 2 of the Disaster On September 21, the governor of one state activated 1,200 National Guardsmen, 1,100 state guardsmen, and state game wardens to contend with the impending crisis. In addition, the governor of that state reversed the fow of trafc, making the interstate highways one direction—only out of the major port city of that state for Case Studies: Disasters from Natural Causes—Hurricanes ◾ 57 evacuation purposes (Hays, 2005). You are receiving some good news that patients from certain major hospitals and some shut-ins have already been transferred to cities out of reach of the hurricane (Easton, 2005). However, you are now aware that trafc has been gridlocked for one state in particular and that evacuation is not occurring as fast as you would like. In addition, much of the nation’s oil refnery production centers are vulnerable (Townsend, 2005). The director should attempt to provide fueling points for vehicles that are along the evacuation route as well as food and water to the drivers. The director should contact the state emergency response coordinator and see if there are any alternative ways that trafc can be rerouted or phased into certain highways to temporarily alleviate the trafc jams. If at all possible, as much oil and chemicals as possible should be removed prior to the hurricane strikes to avoid chemical and hazardous material situations. The director should stay in close contact with other federal agency directors as well as state and local government of- cials in order to coordinate efective disaster response relief eforts. Stage 3 of the Disaster On September 24 the hurricane makes landfall between two neighboring states (Hurricane Headquarters, 2007). As the hurricane hits the coastline, three com- munities in one state are completely obliterated, with another six communities suf- fering heavy damage (Struck and Milbank, 2005). Two million people are now without electricity (Diamond, 2005), and the estimate for property damage stands at $10 billion (National Weather Service, 2007). The death toll has reached an estimated 82 people that have been killed by either direct causes of the storm or indirect causes (Knabb, Brown, and Rhome, 2006). The director should attempt to see if mobile generators are available to be deployed to communities where power has been knocked out by the storm. The director should also attempt to get fuel to those plants that have not been resupplied so that they can be back up and running fairly quickly. What is your plan to get aid to the communities that have been struck by the hurricane? The director needs to be very proactive in getting logistics moving toward cities that have no food, water, or medical supplies. The cities that have been hit the hardest will get relief aid as soon as roadways are available that can be used to transport goods to those areas. For areas that are isolated, helicopters will be needed to transport goods to those communities. What is your communication plan for interacting with other agencies and non- proft organizations? If the director does not maintain communication with the other organizations, there is a danger that relief will not be distributed properly to the afected communities, with some areas receiving too much aid while others receive nothing at all. Tere will need to be temporary housing provided for residents whose homes have been destroyed or damaged. Key Issues Raised from the Case Study Evacuations on a massive scale not only require the necessary infrastructure to handle a heavy trafc load, but must also take into account the support structure necessary for increased vehicular use (e. If evacuations are conducted in stages, it is necessary to ensure that those stages are rigidly adhered to in order to avoid a massive infusion of vehicles all using the same roads at the exact same time. The trafc gridlock caused by evacuees is a focal point in this particular case study. Millions of people used the same interstate highways at the same time, forc- ing trafc to a crawl. People who voluntarily left the city were in their cars for hours and had not moved very far at all when the formal evacuation order was given. At least one former city manager in Liberty, Texas, discussed how he and his staf were handing out cups of water to motorists that had been stuck in trafc for hours. The logistical planning was incomplete and resulted in lack of water, food, and gas for motorists that were attempting to get clear of the Houston metropolitan area where Hurricane Rita had the potential to make landfall. Items of Note Hurricane Rita resulted in $8 billion of damage to Texas alone, which also resulted in thousands of people being unable to return home for weeks due to infrastruc- ture damage (Struck and Milbank, 2005). At least 90 tornadoes were associated with Hurricane Rita and produced the most tornadoes ever recorded in Jackson, Mississippi, in a single event to date (2012) (Knabb, Brown, and Rhome, 2006). Chapter 4 Case Studies: Disasters from Natural Forces—Floods Johnstown Flood, Pennsylvania, 1889 Stage 1 of the Disaster You are the mayor of a town of 30,000 people. Your town mainly consists of blue- collar steel workers that are of German descent. Unfortunately, your town has been built on a foodplain where two rivers meet and the riverbanks have been narrowed to give the town more land to construct residential housing and other buildings. In addition, the South Fork Dam located upstream needs maintenance badly, but is not being maintained by the local hunting and fshing lodge that is responsible for its upkeep (U. As the leader of the community, you should encourage precautionary measures on the issue of fooding because it is a recurring problem and can be a potentially bigger problem in the future. The mayor should undertake a study that will review the planning and zoning ordinances of the town and direct the town council to take action on restricting certain development along the river. An emergency plan of action and evacuation plan should be developed for the citizens of the town as well as identifying resources that may be needed in case of an emergency. The mayor’s communication plan should include the town council members and make them aware of the potentially dangerous situations that can occur if certain issues are not dealt with appro- priately. Additionally, the mayor should begin to develop support for better planning and building ordinances with the town’s staf as well as the housing developers. The mayor should be in contact with the party responsible for maintenance of the South Fork Dam as well as the town’s frst responders. The community at large should be made aware of any emergency or evacu- ation plans that currently exist. Resources need to be put in place to ensure that the mayor can communicate with the town residents in times of crisis. What resources do you need to acquire for the problems that have occurred or that could occur? One of the bigger problems that the mayor will face is getting the resources to fx the South Fork Dam. The general population currently does not feel any sense of urgency in making repairs or even maintaining the dam. What government entities do you need to interface with to accomplish your plan of action? As stated earlier, the mayor needs to interface successfully with the town council. Communications with the town council are imperative for getting the resources needed to repair the dam, as well as for passing any type of build- ing or zoning ordinances concerning the development that is continuing along the river.
Since almost all congenital cardiac surgery is in a sense ‘minimally invasive’ in that the cardiac incisions must be limited order v-gel australia, it is often diffcult for all members of the team to be able to follow the progress of the procedure purchase v-gel. These instruments are designed to Furthermore buy discount v-gel 30 gm online, the picture from the headlight camera can be be controlled by the fngers rather than by the arms buy discount v-gel 30 gm on-line. Unlike adults, children rarely complain of back, era, as well as an overhead camera mounted in the overhead neck or interscapular pain following a sternotomy. This composite sion does not require stretching, cutting or tearing of any image can be connected via the Internet to viewing stations muscles, unlike so many other incisions. The blood supply elsewhere in the hospital such as the senior surgeon’s offce of the bone is excellent in children so that healing is usually or remotely allowing a junior surgeon to call for input from rapid and complete. For example, the Norwood procedure with should be performed using small instruments. While it is a Blalock shunt involves work on the great vessels and right true that many of the instruments used for congenital car- subclavian artery so that the incision should extend up to the diac surgery need to be delicate, they should not necessarily sternal notch. They need to be long enough to allow three pairs sion can be limited and does not need to extend to the bot- of hands (the surgeon and two assistants) to simultaneously tom of the xiphoid process. On the other hand, the depth procedures, however, the top end of the skin incision can be of the surgical feld in neonates and infants is very much limited to end some distance below the sternal notch. This is an important cosmetic consideration since the major dis- is an important advantage for the surgeon in that it allows advantage of the standard incision is the fact that it can be the hand to be stabilized on the chest wall. By limiting the diac surgeons can use time in the dentist’s chair proftably upper end of the incision it is possible to conceal the incision by analyzing the methods by which dentists and hygienists with most clothing. As with It is critically important that the bone incision be exactly dental instruments, most of the movement of instruments in the midline. The width of the sternum varies tremendously used by the congenital cardiac surgeon should be controlled between children and it may be very narrow. If the incision by the fne muscles of the hand and not by the forearm and is made off midline there is a real risk that the sternal wires shoulder girdle muscles. Microvascular instruments, such as will cut through the delicate cartilaginous bone resulting in the Castro–Viejo needle holder are specifcally designed to an unstable sternum and poor healing. An unstable sternum be controlled by the fngers rather than by the arms and are will increase the risk of mediastinal infection. Relative to most other surgical incisions, it has There are a number of options to improve the cosmetic less postoperative pain, particularly in young children who appearance of the standard sternotomy incision. Opening the been possible to prove that minimally invasive incisions sternum requires hinging of the ribs at the costovertebral reduce pain or speed convalescence. It should be is suffciently fexible in children that there seems to be little exceedingly rare that axillary artery cannulation is required, or no advantage in ‘T-ing’ off the incision to one or other side. Carotid artery cannulation is not recommended other can be kept entirely below the level of the nipples. While this than in extreme situations because there is a risk that cerebral limited incision allows for safe closure of septal defects, we blood fow will be compromised. ReopeRaTiVe sTeRnoTomy The previous skin scar is usually excised and the sternal Reopening a sternal incision can be done safely as long as wires are cut and removed. Planning begins with and the linea alba is opened to allow a plane to be developed the preoperative studies which should document the distance behind the lower end of the sternum. The used to elevate the lower end of the sternum off the heart and sternal wires are quite helpful as markers on a direct antero- to provide a counter pressure to the oscillating sternal saw. If a conduit is known to be close to the left side of the status of the femoral and iliac vessels. This knowledge the sternum it may be advisable to free up only the right half may be available from the preoperative catheterization, from of the sternum until the retractor is placed. However, ulti- femoral ultrasound studies or simply from careful palpation mately dissection should extend to the pleural cavities bilat- of the femoral pulses and observation for evidence of previ- erally. At least one groin should be prepped completion of the procedure, but more importantly it allows into the surgical feld. Injury to the right heart can gener- the heart to be moved around more freely, thereby improving ally be dealt with easily by cannulating the femoral artery exposure without having to retract the chambers of the heart and placing a pump sucker in the injured structure. Even emergency cannulation of the femoral ves- nal retractor is in place, dissection is begun using the elec- sels after an aortic injury has occurred will not be helpful trocautery. Dissection should be begun in the space between because blood pumped into the arterial system from any the diaphragm and the inferior surface of the heart which is cannulation site will simply exit via the site of aortic injury. Grasping the diaphragm with for- Certain anomalies carry a higher risk of injury to the aorta, ceps and moving it up and down helps to identify the correct most notably d-transposition of the great arteries. The space is traced rightwards until the right atrium is erative catheterization should include lateral images which identifed. Suffcient inferior right atrial free wall is cleared have a suffciently large frame size to show both the ster- to allow placement of at least one venous cannula. In fact, it may be the surgeon’s choice to proceed with of the sternum and particularly if there is obvious adhesion cannulation at this stage. The remainder of the dissection can which will be apparent because of absence of relative move- proceed during the cooling phase of bypass. Decompression ment between the two structures, then femoral cannulation of the right atrium allows dissection in this area to proceed is required of both the femoral artery and vein before the more rapidly and safely. The child should be cooled on femoral bypass before the bone is cut in the vicinity of the aorta. If sTeRnaL cLosuRe the preoperative studies demonstrate that a right heart struc- ture is very close or adherent to the sternum, at a minimum The sternum is closed with wires of an appropriate gauge the femoral artery should be cannulated before the bone is for the child’s size. It is often wise to cannulate a femoral vein also with a advisable to place the wires through the costal cartilage to thin-walled cannula, such as the Biomedicus® cannula. Ischemic necrosis caused by cannula should be advanced to the level of the right atrium the encircling wires is rarely, if ever, seen. If the femo- wires with an inadequate depth of bite will often cut through ral arteries are occluded bilaterally, it may be necessary to the thin and delicate bone of the child’s sternum. Rather than following the femo- eight wires reduce the tension on each bite and do not appear ral vessels up under the inguinal ligament, it is preferable to interfere with sternal growth. Bleeding can be reduced by that is diffcult to control without leaving a large amount of accurate dissection in the less vascular planes that almost packing, it may be wise to leave the sternum open. This situ- always exist between structures, no matter how many previ- ation most commonly arises in neonates, but rarely beyond ous procedures have been performed. If hemodynamic instability is severe and the surgi- single skill in the feld of congenital surgery which seems to cal team has determined that there is no remediable anatomic be as innate as the ability to see these tissue planes. Most importantly, skill can be developed in using the skin edges with continuous nylon. Every surgeon will learn to fnd a blend of cutting sTeRnaL suspension and coagulation current that suits his or her dissecting style. The blend will need to be varied depending on the tissue char- The occasional neonate will have such extreme instability acteristics. For example, the woody edematous planes that are that it is helpful to elevate the sternum completely off the found in the child who has had a bidirectional Glenn shunt are heart. This can be achieved with heavy nylon sutures that best developed with a predominantly coagulation current with encircle each half of the sternum and can be attached to the appropriate countertraction developed between the surgeon overhead heater of the Isolette®. A strong coagulation current be helpful in bringing together the two halves of the sternum is often useful when taking lung adhesions down because gradually over a day or two by twisting the nylon suspension very vascular adhesions will have developed, particularly to sutures together. This will minimize the hemodynamic com- the heart itself, but also to the chest wall. A posterolateral thoracotomy is used for repair of coarcta- Electrocautery carries a risk of injury to nerves, particu- tion, but little else in the modern era. Care are placed through a sternotomy approach and a patent duc- must be taken to reduce the strength of the current when tus is ligated through ports using a video-assisted approach. It may be advisable to The thoracotomy for coarctation repair should be in the use sharp dissection when very close to the nerve. It is mainly a pos- when adhesions are very dense and vascular, injury to nerves terior rather than a lateral incision so that it should not be necessary to divide any of the serratus anterior. The muscle layer is closed with a sequence of the operation, the surgeon can optimize the expo- running absorbable suture, such as Vicryl, followed by a sub- sure and the effciency of the procedure. It is very easy to ‘paint oneself into a occasionally advisable to close the thick skin of the back with corner’ from which point the only way out is to take down interrupted nylon sutures because this area is prone to break- some of the work that has already been done.
They are subendocardially localized generic v-gel 30 gm with visa, and branch into small transmural ramifications (12) 30gm v-gel sale. In rare circumstances discount 30 gm v-gel overnight delivery, these remnants may provide the substrate for some forms of ventricular preexcitation in otherwise normally structured hearts (16) purchase v-gel on line amex. A: Shows schematic representation of the location of the conduction system components in relation to the external and internal cardiac anatomy. Note the differential staining within the cardiac nodes and the bundle of His, the latter being additionally surrounded by connective tissue. The sporadic appearance of individual cardiomyocytes resembling so-called Purkinje cells in the atrial musculature between the cardiac nodes, and in the pulmonary venous sleeves, caused some authors to conclude that these cells constitute specialized conduction tissue at these ectopic locations (17,18). In the postnatal heart, however, the preferential conduction that exists within the atrial musculature is explained by the orientation of the cardiomyocytes, rather than the existence of specialized internodal tracts (19). A: Shows that in the very early chicken embryonic heart (about stage 9), which is not yet contracting, action potentials of spontaneous depolarization can be detected over the entire heart tube. Functional pacemaking area in the early embryonic chick heart assessed by simultaneous multiple-site optical recording of spontaneous action potentials. Note that the interval between the upstroke of the action potentials measured at proximal (①) and distal (②) sites of the heart tube remains remarkably similar at stage 13 as compared to very young stage 10 (red bars in B). At stage 13, the initial phase of the caudal action potential, however, already resembles the slow depolarization period of the definitive pacemaker action potential, so-called “phase 4 depolarization” (arrow in B). Localization of pacemaker in chick embryo heart at the time of initiation of heartbeat. At the beginning, the initiation of contraction is observed in the middle of the straight heart tube (23), where excitation–contraction coupling of the cardiomyocytes has progressed sufficiently to produce active shortening of the myofibrils. Studies in chicken embryos using voltage-sensitive dyes detecting spontaneous electrical depolarization have demonstrated that pacemaker activity can be identified along the whole primary heart tube prior to any contractile activity (24). However, the earliest spontaneous pacemaking activity always is located at the inflow of the primary heart tube (25) (Fig. During further development, the pacemaking activity in already differentiated myocardium is suppressed, while newly added myocardium at the venous pole assures this site remains the dominant pacemaker site (25,26), ensuring efficient unidirectional pumping of the blood. Very early in embryonic life, prior to the development of true pacemaker ion current(s), shuttling of calcium in and out of the sarcoplasmic reticulum through an inositol triphosphate–dependent mechanism may be responsible for pacemaker activity (28). After the venous sinus has shifted to the right, the walls of its right lateral part become muscular and thickened. Although these studies were based on comparable histologic stainings, they led to very different hypotheses about its development. Numerous molecular studies in experimental animals, and in human hearts, have revealed that this is not the case. The primary heart tube, although consisting of cardiomyocytes, which, due to their primitive phenotype, all possess pacemaker activity (23,35), does not contain the precursors of the cells destined to form the definitive sinus node, as at this stage the cardiomyocytes forming the systemic venous sinus have not yet been added to the heart (see Chapter 1). In a pattern strictly complementary to the expression of Nkx2-5 within the developing atrial chambers, the mesenchymal cells at the caudal ventral side of the inflow tract express the T-box transcription factor Tbx18, which drives them to differentiate into cardiomyocytes forming sinus muscle, and ultimately the sinus node (36,38). Genetic lineage analyses have provided strong evidence for the origin of the entire venous sinus from these Tbx18-expressing cardiac progenitor cells. Taking into account that these cells are the precursors of the sinus node, this finding is consistent with the previous observation that the elongating heart tube shows an increase in beat rate (39). Early specification of the sinus nodal primordium in the mouse embryonic heart is regulated by another T-box transcription factor Tbx3 (41), which is expressed in the human embryonic heart in an almost identical pattern. Tbx3 represses the expression of the fast-conducting connexins 40 and 43, thus allowing newly added sinus myocardium to escape from further differentiation toward working myocardium (Fig. Forced expression of Tbx3 in the atrial myocardium of the postnatal mouse heart leads to the development of ectopic functional pacemaker tissue, thus identifying Tbx3 as a key regulator of the sinus nodal phenotype (41). Accordingly, dual sinus nodes are present in Pitx2c-deficient mice and in humans with right isomerism of atrial appendages (43). Green arrows indicate positive regulation and red lines suppression of the sinus muscle and atrial muscle differentiation. The failure of complete “atrialization” of this myocardium in some individuals could explain the presence of ectopic automaticity, and the initiation of ectopic atrial tachycardias. With ongoing development, the primary myocardium at specific locations along the outer curvature of the looping heart tube begins to further differentiate and expand to form the atrial and ventricular chambers, which are characterized by fast conduction of the electrical impulse, and matching synchronous contractions (45). In chicken embryos, retrovirus-labeled neural crest cells are not identified in the definitive conduction system (50), demonstrating that the entire conduction system has a myogenic origin. In the hearts of wild-type mouse the expression of Tbx3 and connexin 40 are strictly complementary, while in the mouse heart, in which Tbx3 was knocked-out, expression of connexin 40 is extended into the sinus node. Tbx3 controls the sinoatrial node gene program and imposes pacemaker function on the atria. Since standard histology does not permit the unambiguous identification of different tissue types, it is not surprising that their conclusions were far from comparable. A: Shows a scanning electron microscopic image of a stage 17 chicken looping heart, where ballooning of the atrial and ventricular chambers has just been initiated at the outer curvature of the heart tube. Developmental origin, growth, and three-dimensional architecture of the atrioventricular conduction axis of the mouse heart. Along with many other transcription factors Tbx3, once more, plays an important role in this process (70) (Fig. Thus, Tbx5 and Nkx2-5 act synergistically within the transcriptional network of the developing bundle of His by cooperatively activating expression of the transcriptional repressor Id2. Cellular birth-dating studies suggest that this factor governs the slowing of proliferation of the cardiomyocytes making up the bundle of His and its branches (63). Interestingly, distinct gene expression programs appear to regulate early versus late development of the bundle of His (71). The mechanisms by which this fascinating selective gene regulation is achieved remain to be elucidated. Molecular analysis of patterning of conduction tissues in the developing human heart. According to current model, the bundle of His and its branches develops in situ from the myocardial cells of the ventricular septum under regulation by numerous transcription factors. Endothelin and neuregulin play important role in specification of the Purkinje network. An important characteristic of these bundles is their high conductivity due to the expression of fast-conducting connexin 43 (74), which can lead in specific circumstances to life-threatening arrhythmias. The Bmp-receptor 1a, also known as Alk3, and the transcription factor Tbx2 have been shown to play an important role in the correct formation of the plane of insulation on the left side of the mouse heart (75,76). In the absence of myocardial Alk3 or Tbx2 expression, not only does connective tissue fail to form between the atrial and ventricular chambers, but also the persisting myocardial strands do become fast conducting, and are thus capable of causing preexcitation. The bundle of His, which remains the only muscular connection between the atrial and ventricular chambers after completion of the formation of the insulation plane, becomes gradually isolated from P. Note the tiny myocardial tracts still crossing the forming plane of insulation (arrows). The main function of the ventricular conduction network is the rapid propagation and uniform distribution of the impulse to the ventricular muscle mass. Unlike the working myocytes, however, they have a poorly developed contractile apparatus, and even display some degree of automaticity, resembling the embryonic primitive phenotype (46). In embryonic hearts that do not have discernible bundle branches or a Purkinje fiber network, fast conduction within the developing ventricles already is present at stages when the trabeculations have appeared. It has been established that the development of the mature pattern of ventricular activation and formation of the Purkinje fiber network are closely linked to the development of the ventricular trabeculations (50). The cavities of the ventricles in the early embryonic heart contain an extensive meshwork of trabeculations, which attach to the thin outer ventricular wall, and, similar to the myocytes making up the mature Purkinje fibers, express the fast-conducting connexins 40 and 43 (31,63,78). Thus, there is a molecular substrate for preferential rapid conduction of the electrical impulse through the ventricular trabeculations to the ventricular musculature in the embryonic heart even without a fully differentiated true ventricular conduction network. Individual ventricular myocyte precursor cells give rise to a series of progeny that migrate preferentially vertically to form the meshwork of trabeculations (79,80). From mouse studies, it is known that neuregulin-1 and Notch signaling are necessary and sufficient to form the ventricular trabeculations by regulating the relative proportion of the embryonic ventricular cardiomyocytes that form the trabecular and compact myocardium (81,82). Another signaling molecule, endothelin-1, secreted by endothelial cells covering the ventricular trabecular myocardium, probably in response to increasing biomechanical forces such as shear stress and pressure in the walls of the ventricular chambers, has been shown to play an important role in the induction of the Purkinje fiber network in the chicken embryonic heart (83,84). Several transcription factors have been shown to play a role in the regulation of the development of rapid conduction within the Purkinje cardiomyocytes by affecting the expression of connexin 40. Another transcription factor, Irx3, also regulates formation and function of the His–Purkinje system (90).