Chapter 4: Mass Gatherings

Mass gathering medical care refers to the provision of medical services to organized events or venues with relatively large numbers of people in a defined geographic area. Typically, mass gatherings are considered to be events that have at least 1000 people; however, this does not have to be the case.^1,2 Although the principles of mass gathering medical care traditionally apply to congregations of large numbers of people, these principles also apply to smaller venues with a relatively high concentration of people in a limited space and those where it may not be easy to access the general system of EMS. Therefore, the principles of mass gathering medical care also apply to athletic events with fewer than 1000 people, as well as airplanes, cruise ships, and wilderness environments.

Table 4-1 lists some of the major factors affecting planning for a mass gathering event. Physical barriers may inhibit easy entry and exit from the site. These barriers can make it difficult to get medical resources into, and to get patients out of, the event location. Reliable communication between medical personnel, event organizers, and outside medical resources is key to a successful medical response. Environmental factors will also affect the response, especially at extremes of cold, wet weather that can precipitate hypothermia or hot weather that can precipitate dehydration and heat stroke. Finally, event planners should consider possible public health threats of widespread communicable disease and the potential for a terrorist attack with explosive or other devices.

The need for mass gathering medical care was first described after two spectators collapsed and died during a University of Nebraska football game in 1965.³ The event organizers were not prepared to manage medical emergencies in the midst of the event, and consequently, when these two patients needed medical care, the organizers were not able to meet the need. Medical directors have become experienced in mass gathering medicine, and case reports are described for sporting events, concerts, expositions, and other large congregations of people.²

One of the largest global gatherings, the Islamic Hajj pilgrimage to Mecca, Saudi Arabia (reaching 2.5 million in 2009), has required officials to manage threats to public safety from outbreaks of infectious disease to major traumatic injuries from stampedes. Other notable global mass gatherings include the 2010 World Expo in Shanghai, China, which attracted approximately 70 million visitors, and the FIFA 2010 World Cup in South Africa, during which more than 1 million foreign visitors entered the country.⁴ As large-scale global mass gatherings become more common, it is evident that there is a need for a global effort to develop the science of mass gathering medicine. This is exemplified by the mass gathering conference held in collaboration with the Kingdom of Saudi Arabia Ministry of Health in Jeddah, Saudi Arabia, in 2010⁴ and the formation of an online registry for mass gathering data collection as developed by the University of British Columbia.⁵

Interestingly, despite the fact that mass gatherings are generally attended by individuals in good health, these events tend to have a higher incidence of illness and injury than that which would be found in the general population.⁶ The incidence of usage of medical care at mass gatherings has been reported to range from 4 to 440 patients per 10,000.² The wide variance in medical usage rate is a function of the type of event and environmental factors.

In preparing for a mass gathering event, medical directors should develop an organized approach through the development of a medical action plan.⁷

PHYSICIAN MEDICAL OVERSIGHT

All mass gathering events should have an identified physician medical director who is responsible for developing the medical action plan. The medical director is also responsible for providing medical oversight before and during the event. This person should be board certified in emergency medicine and have a current medical license from the state(s) where the event will be located. The medical director should also have experience in the medical direction of EMS and the provision of medical care at mass gathering events. In the future, it will be desirable for the event medical director to be board certified in EMS. Experience and training in EMS provide an event medical director with skills in field medicine, including creative thinking, the ability to make diagnostic and treatment decisions purely on clinical grounds, and an awareness of operational environments that are very different from a typical ED.

The medical director is responsible for developing plans for indirect medical oversight and ensuring a coordinated system of direct medical oversight. Indirect oversight describes a system of written protocols that provide the medical personnel with a standardized set of directions for the care of a variety of traumatic and medical conditions that may be encountered during the event. These protocols should always be consistent with local EMS protocols unless the medical director has prior approval from the local jurisdictional EMS medical director to deviate from them. Direct medical oversight describes a method of direct communication with medical providers during the event to answer questions and provide medical direction in real time during the event. Although direct oversight can be delegated to a team of physicians for an event of long duration, ideally, the medical director should plan to be on site during the event as much as possible.

COMMAND AND CONTROL

In addition to an event medical director, mass gathering plans should have an organized system of command and control. Although many systems exist for the command and control of resources at emergency incidents or mass gatherings, one of the most well-tested and efficient methods is the Incident Command System. It was initially developed as a consequence of poor management of a series of wild-land fires in Southern California in 1970.⁸ The system can be used for any type or size of emergency, disaster, or mass gathering, with the purpose of allowing either a single agency or multiple agencies to communicate using common terminology and operating procedures. Further, the ease in putting the system into action allows it to be functional from the time an incident occurs until the requirement for operations no longer exists. In fact, since its original development, the Incident Command System has been adopted by the National Fire Academy and currently provides the structure for the Federal National Incident Management System.⁸

The purpose of establishing a command and control system like the Incident Command System is to define clear lines of reporting and communication among all major functioning components that may coexist during an incident. The organizational structure develops in a modular fashion from the top down and may incorporate five functional divisions.⁸ While the Command function is always established, the other divisions, which include Operations, Logistics, Planning, and Finance, form as needed (Figure 4-1). The incident commander for a mass gathering event ideally should be someone with experience functioning within an Incident Command System structure. A lead fire official would be well suited as the incident commander, because officers in the fire service typically have extensive experience working within the Incident Command System. However, if the local fire department is not involved with the event, as may be the case in smaller events, command should be managed by someone with EMS experience and ideally should not be a physician. As will be discussed later, the physician's role within the Incident Command System structure should be focused on direct oversight of patient care and not involve the global issues that are the concern of the incident commander. In short, the incident commander must be involved in directing available resources, communicating effectively within the organization, continuously assessing the incident priorities, coordinating activities of outside agencies, and always retaining ultimate responsibility for the incident.

Within a typical Incident Command System, the provision of medical care to the public occurs within the Operations Section. Often referred to as the "doers," it is the function of the Operations Section to complete the primary tasks of the mission. The medical branch in Operations should establish a similar modular command framework for organizing the various medical teams, each having at a minimum their own team lead. Members of the medical teams include, but are not limited to, EMTs, paramedics, nurses, physician assistants, and physicians. It is not required that the physician take the lead role of each medical team. In fact, it may be more beneficial to have the individual with EMS or fire service experience in the role of team lead, which ideally may be an EMS physician. Depending on the number of agencies involved, there may be more than one EMS medical director on scene. An agency's medical director should be available for direct medical oversight as needed and should ideally be on site as much as possible. The medical director(s) should function as a commander within the Operations Section and report back to the section head of Operations who ultimately reports to the incident commander. Key to the success of the Incident Command System is that every individual abides by the established hierarchical ranks of command.

Perhaps the most important functional component for ensuring a successful mass gathering event within the Incident Command System structure is the Logistics Section. Logistics personnel are responsible for ensuring that all equipment and supplies are available and in working order when needed. Whereas the Operations personnel are the "doers," the Logistics personnel are the "getters." They "get" the supplies needed by Operations. Because the ability to effectively care for the public at a mass gathering event is highly dependent on having a certain amount of supplies, it cannot be stressed enough that a well-functioning Logistics unit is critical to the success of the event. The event medical director should not have to be responsible for acquiring necessary supplies if Logistics is functioning well.

The Incident Command System also provides a framework for accountability of personnel, which is paramount to maintaining safety during a potentially long and unpredictable event. Within each branch under Operations, there should be a designated safety officer. The sole responsibility of this individual is not to provide care, but instead to maintain a system by which all personnel are accounted for at all times. This may include simply keeping a visual account of personnel, which would only be feasible at a very small event, or implementing a method that uses an identification tag that is kept by the safety officer during the time each individual is operational on scene. Each functional unit safety officer should ultimately report to the command staff safety officer for the event, who reports to the incident commander.

Closely related to the concept of accountability is the notion of force protection. This is a term used by the U.S. military to describe preventive measures taken to mitigate hostile actions against individuals. The number one priority in all events is scene safety. It is well known that if a medical provider becomes sick or injured, the provider will use resources intended for the public and distract other providers from the ability to perform their duties. As such, a sick or injured medical provider has the potential to dramatically disrupt the overall medical mission for the event. While medical personnel are always responsible for assessing and assuring their own safety and those with whom they work, it is imperative to have a well-designed plan for the overall medical care and protection of the medical providers at the event. One of the duties of the event medical director is to be prepared to provide care to the other medical providers should the need arise. In addition, communication with law enforcement personnel will help to ensure the overall protection of the medical providers. Their support should be readily available and have the means to immediately respond to any location should the situation become unsafe. Depending on the type of event, threats could range from those that are readily seen (i.e., crowds at a concert) to those that are hidden (i.e., explosives and other weapons carried by an individual with the goal of using mass gathering events to kill and injure).

RECONNAISSANCE

In the beginning stages of preparation, the medical director and assistants need to assess the site to identify the geographic variants that will affect their ability to provide medical care to the public. Within the Incident Command System structure, this establishes a role for the event medical director in the Planning Section. Most important, the planners will need to determine routes of ingress and egress for the event. Backup plans should also be developed. Planners should determine ideal locations for setting up a base of operations, fixed medical care sites, and staging areas for mobile units. Decisions should take into account the effects of predicted traffic flow, predicted sites of high-volume medical need, natural geographic barriers, and location of receiving medical facilities.

NEGOTIATIONS

The process of developing a medical plan for a mass gathering event requires a cohesive teamwork approach with multiple interest groups. First and foremost, the medical planners should develop a plan that meets the needs of the public and the event planners. This first step may require some negotiations with event planners in determining locations for fixed and mobile medical units, level of care to be provided, and resources provided to the medical units. Negotiations will determine if the medical units will be paid under contractual terms by the event planners or if they will volunteer their services to the event. This negotiation stage should also resolve who will finance the purchase of needed supplies and pay for other needed resources, such as costs of transportation and liability coverage.

Regardless of who pays for supplies, it is important that the medical teams coordinate with the Logistics Section to ensure that equipment and supplies are readily available when needed. Similarly, regardless of who is responsible for acquiring supplies, there is value to the event medical director having ultimate control over the acquisition and maintenance of critical medical supplies, as this will ensure that the medical needs of the public are assured.

Medical planners should also establish communication and agreements with other outside agencies that have a potential need to interact with the medical response team for the event. Medical teams that are formed outside the local jurisdictional EMS system should have an agreement with local EMS that addresses transportation of patients out of the event to local resource hospitals. Transfer and acceptance agreements should be developed with the hospitals. Local law enforcement should be contacted for assistance with traffic flow and security. Events that have the potential to be affected by security issues on a national scale may also require agreements with the U.S. Department of Homeland Security for disaster and security response.

HUMAN RESOURCES, LEVEL OF CARE, AND TRAINING

The event medical director should determine the desired level of care for the event based on the predicted medical need and available resources. Depending on the needs of the event, the desired level of care may range from emergency medical responders to physicians. Once the desired level of care and the predicted patient volume are determined, the medical director will be able to develop a plan for human resource needs. These resources may be acquired through the local EMS system, area hospitals, medical training programs, or other sources such as ski patrols and medical reserve corps.

Medical personnel should be licensed to practice at their level of training in the local jurisdiction. Although the medical personnel should be trained for their established level of care, the medical director may want to have additional training sessions to address specific injuries and medical conditions that are predicted to be encountered by the medical personnel during the event. Regardless, it is important that the providers work within a defined scope of practice as determined by level of training and any operational-specific protocols that may be authorized by local authorities for mass gathering events.

EQUIPMENT

When considering equipment for a mass gathering event, planners and medical directors should take into account the type of event, the weather, and the skill level of the medical staff. Medical units comprised of personnel at the EMT level or lower will need to carry significantly less equipment than units staffed by personnel at the paramedic level or higher. Units with physicians may elect to have on hand supplies to do simple suturing and advanced resuscitation. However, thought should be given to the available time needed to suture a wound in balance to the patient volume and the availability of the fixed standing acute care centers. If available, it may be more advantageous to refer patients needing procedures to acute care hospitals. The appropriate way to manage the need for procedures is dependent on the available resources and the overall mission of the medical care at the event.

Often, a large proportion of time spent planning out supplies is focused on generating a broad list and subsequently obtaining supplies that would be necessary to provide medical care for a critical patient. As discussed earlier, it is important to consider that rapid transport of this patient away from the incident to the controlled environment of an acute care hospital may be more beneficial for the patient and free up the provider to care for other patients who would likely not receive evaluation given the time-consuming nature of the critical patient. In addition, proportionally fewer critical patients are seen at a given event compared with the vast majority who seek aid for minor complaints such as scrapes, blisters, headaches, and sprains. Therefore, more effort should be placed on obtaining supplies in highest demand. As suggested by the number and type of complaints seen, those supplies in highest demand typically include bandages, foam padding for blisters, ice for sprains, fluids for oral rehydration, acetaminophen, and ibuprofen.

In general, the incidence of cardiopulmonary arrest and the need for major resuscitation at mass gathering events is low. However, medical units should, at the very least, have access to an automated external defibrillator. Event-specific protocols should address the use of advanced airway equipment, including the possible use of medications for rapid sequence intubation. Plans for other resuscitation needs should also be addressed prior to the event so that all providers manage these small numbers of cases in a standard format (e.g., fluids for sepsis, postresuscitation care, management of cardiac arrhythmia, status asthmaticus). Although it is rare that there is a need for major resuscitation, there may be value to having supraglottic airways (e.g., KING LT Airway^®) and adult intraosseous needles (e.g., EZ-IO^®).

In addition to the level of training of the medical staff, equipment needs will be determined by the mobility of the unit. Some events may need mobile medical units that are able to reach patients in difficult locations or easily move through large crowds. Units on foot and other nonmotorized means of travel will be able to carry fewer supplies than those using motorized vehicles such as golf carts. For events using nonmotorized mobile units, it will be important to design a means to bring heavier supplies to a patient should the need arise, such as equipment needed to manage a patient with a high suspicion of spinal cord injury. Units in fixed locations will be able to stock a greater quantity of materials, possibly including cots, shelter, and additional medical supplies.

Although the equipment needs are unique for each event, there are some things that are universal. Tables 4-2 and 4-3 show suggested items for both mobile and fixed units as well as suggested equipment based on the skill level of medical personnel.

TREATMENT FACILITIES

Medical directors will need to determine if the scope of the event will require fixed treatment facilities or if mobile units will be sufficient. Factors that contribute to this decision are the predicted number of patients expected to seek medical care, length of the event, distance to off-site medical care, and environmental factors. Fixed treatment facilities can be set up in mobile tents or within a permanent structure. Regardless, fixed treatment facilities should be set up in such a way as to be able to withstand the predictable weather conditions that may be encountered during the duration of the event. From a patient care perspective, it is important to have a facility that has environmental control to manage heat-related illness in warm weather and cold-related illness in cold/wet weather. Off-site treatment facilities should be arranged with local hospitals.

TRANSPORTATION

Nonmedical and medical transportation is necessary, taking into account the number, capacity, and staging location for transport units. Nonmedical transportation units move personnel and resources throughout the site. Medical transportation moves patients within the event location and out to area hospitals.

Planners may also need to address nontraditional modes of transportation, such as golf carts, boats, bicycles, horses, snowmobiles, and toboggans. Protocols should also be developed that address the appropriate use of air medical transportation, including location and setup of a safe landing zone.

PUBLIC HEALTH

Public health concerns during a mass gathering event may be addressed by the event managers or delegated to the local public health authority or the medical director and EMS system. Even if these concerns are not delegated to the medical response team, public health concerns can affect patient care, and therefore the medical director should be aware of these issues. Table 4-4 lists some potential public health concerns.

ACCESS TO CARE

The event managers and medical director should develop plans to ensure that the public will be able to access emergency care, if needed. These plans should ensure that the locations of fixed treatment facilities are well marked with signs and other visual aids and that there are limited barriers to access these facilities. Fixed treatment facilities should be accessible to all members of the public and comply with guidelines that are in accordance with the Americans with Disabilities Act. Mobile medical personnel should also wear vests or other high-visibility clothing easily identified by the public. Pamphlets or signage can alert the public about methods for accessing emergency care.

COMMUNICATIONS

Successful management of any mass gathering event is contingent upon an effective communication system. To maintain coordination and control, the system must be tailored to the unique needs of the scenario. The design is dictated by a variety of factors, including geography and size of venue, number of participants, budget, and the systems of those with whom providers will be interfacing. Consideration should also be given to environmental factors including temperature extremes, water, and noise. Venues at music concerts and motor sports may require special communication devices to allow for providers to communicate with each other while in the presence of loud background noise.

Modalities can range from simple flag signals to sophisticated radio networks and may include consumer Family Radio Service devices (walkie-talkies), cellular systems, and landline phones. Each has their strengths and weaknesses. Walkie-talkies have a multitude of channel options but are typically limited to a 1- to 2-mile range. Cellular and other phone systems may provide an inexpensive option but are easily overwhelmed by large numbers of users during a crisis. Two-way radios with more power and range than Family Radio Service systems may be analog or digital, using very high frequency, ultra-high frequency, or 800-MHz frequencies. Systems using a repeater antenna allow for communication over greater distances and across rugged terrain. Large-scale, trunked radio systems provide central control of end-user access to selected channels, allowing a greater number of people to function within a limited spectrum. These systems also allow for discrete groups of responders to communicate among themselves without disturbing other groups.

If the communications network is not linked to surrounding resources, a protocol must be in place for making contact and for relaying information as needed. In an urban environment, this may be in the form of an on-site representative from the local EMS system or an identified phone number or frequency designated for the activation of additional resources. In a remote area, one or more people may be tasked with relaying messages via radio or traveling to the nearest telephone or area of cellular service to contact local authorities, or a specific "communications tent" may be organized.

DOCUMENTATION

The medical director should develop a system for documentation of patient encounters during the event. This system need not be as extensive as that which would be found in the typical ED setting and, instead, should be focused on the event to address specific components of the patient encounter as outlined in Table 4-5. Medical documentation should be easy to complete and not exhaustive, such that it can be quickly completed if large numbers of patients seek medical care at the same time. Medical directors may want to consider a method of electronic documentation. Paper documentation should ideally be on a single sheet that can be used by all providers involved in the patient's care (Figure 4-2).

LIABILITY

All members of the medical response team for a mass gathering event should have medical liability coverage. Depending on the restrictions of the carrier, liability coverage may be provided by the policy of one's primary employment or may need to be purchased as additional coverage. The medical director may want to arrange coverage for all members of the medical response team as a group. This should be factored into the cost of providing medical care for the event and should be discussed with planners during the negotiation stage before the event. It is important to note that, if the medical personnel will be reimbursed for services in the form of legal tender or payment in kind (even in the form of a free meal at the event), they may not be protected from liability through Good Samaritan laws, depending on the state. In addition, if the medical providers are advertising their medical services to the public at an event even by setting up an established medical tent, the providers have established a duty to act and are liable to the public to provide care at an established standard. In order to mitigate untoward risk, the medical director should review the laws that pertain to the local area before the event.

CONTINUOUS QUALITY IMPROVEMENT

Unless an event is anticipated to be a one-time occurrence of a short duration, the medical director should establish a method of continuous quality improvement. The continuous quality improvement program should begin with a review of the documentation for patient encounters to identify elements of the system that are performing well and elements that need improvement. The results of continuous quality improvement review should then be used to improve upon the system of delivery of care. The medical director may also consider having regular case reviews with the medical personnel at the event to improve the care being delivered.

COMMERCIAL AIRLINE FLIGHTS

Commercial airline flights represent a special scenario in mass gathering medicine. The steadily rising number of travelers, the increasing mobility of people with chronic illness, and the aging population all contribute to make in-flight medical emergencies more and more common. Yet, the exact incidence is not known because a formal system to report in-flight medical emergencies is not required by the Federal Aviation Administration.⁹ However, it is known that cardiac, neurologic, and respiratory emergencies comprise the more serious complaints as defined by a need to divert the aircraft or use ground-based EMS resources.^10,11,12 GI complaints, such as abdominal pain, nausea, and vomiting, are common yet rarely represent medical emergencies and require little intervention. The combined data suggest that medical emergencies occur at a rate of 20 to 100 per million passengers, with a death rate of 0.1 to 1 per million passengers.^10,13,14

Factors unique to the airline environment that affect medical care include the lower partial pressure of oxygen, potential exposure to chemical irritants, dry air, virulent airborne particles, and venous stasis. The aircraft cabin is typically pressurized to the equivalent of 5000 to 8000 feet above sea level. For individuals with cardiopulmonary disease, this relative decrease in arterial blood oxygen saturation may compromise cardiovascular reserves, thus precipitating an emergency. For chronic obstructive pulmonary disease and asthma patients, a combination of dry cabin air, respiratory irritants, reduced partial pressure of oxygen, and lack of access to their bronchodilators may trigger respiratory problems. In addition, this setting may aggravate normal health behaviors through alcohol ingestion, dehydration, and the inaccessibility of prescribed medications.

The management and disposition of medical emergencies on commercial airline flights are dependent on available personnel and equipment. Airline crew members receive education in basic first aid and CPR as mandated by the Federal Aviation Administration.¹⁵ In addition, most large commercial flights include passengers with some medical training who are called upon to assist a passenger or crew member in distress. Assuming that care rendered is provided on a volunteer basis, Good Samaritan laws should provide protection from medical malpractice liability.

Onboard medical supplies are limited. The Federal Aviation Administration requires passenger-carrying aircraft weighing more than 7500 pounds maximum capacity with at least one flight attendant to carry an enhanced emergency medical kit in addition to a basic first aid kit, as outlined in Table 4-6.¹⁶ Some airlines may choose to supplement these supplies with additional types of medications or equipment. Oxygen supplies are plentiful in the case of cabin depressurization, but there is typically limited availability of supplemental oxygen for sick passengers. In some cases, the pilot may be able to lower the cruising altitude to increase the cabin pressure and subsequently increase the level of oxygen. In 2004, the Federal Aviation Administration mandated that all domestic flights carry an automated external defibrillator.¹⁵ Finally, passengers on board may provide their own medicines for use by others during an emergency, providing an inconsistent but possibly valuable resource.

The decision to divert an aircraft for a medical emergency is a balance between medical need, cost, and logistic constraints. Although the final decision to divert is made by the pilot, there are a number of resources available for guidance. Most airlines contract with some form of ground-based online medical support. Usually directed by an emergency physician, these services provide information on resources available at airports in the vicinity and along the route of flight. From a medical perspective, it is necessary to decide if the patient is stable enough to continue to the planned destination or if there is a need for immediate definitive care. The cost of diverting an aircraft, including rebooking of flights and the cost of dumping fuel to meet maximum landing weight, can be quite high, running from $30,000 to $750,000. Logistically, diversion requires finding a landing site that can accommodate the aircraft and has appropriate medical resources nearby. The decision to divert an international flight may be complicated by legal issues, such as landing rights and passenger screening requirements.

The advent of long-haul travel brings to the forefront the issue of global spread of infectious disease. Passengers may travel across the globe between continents while in the prodromal phase of a disease, or they may knowingly travel while ill, making efforts to mask signs and symptoms with medications. It has been reported that risk of infection is greatest on flights longer than 8 hours and among passengers seated within two rows of the infected individual, particularly referring to the transmission of tuberculosis.¹⁷ This is a testament to the well-contained local circulation of cabin air. However, there is the misconception by some that when an infected passenger sneezes, the majority of the passengers of the aircraft will become infected. In reality, cabin air is a mixture of outside air that enters the aircraft engine continuously and recirculated air passing through high-efficiency particulate air filters that remove particles as small as 0.003 μm.¹⁷

Both the outbreak of severe acute respiratory syndrome in November 2002 and the H1N1 influenza pandemic outbreak of April 2009 demonstrated the urgent need for a rapid, appropriate, and coordinated international response to deal with the spread of pandemics. Consequently, the concept of quarantine is often considered as an option for preventing the spread of disease. Drawing on the most recent experience and analysis of the response efforts to the 2009 H1N1 pandemic, it is evident that airport quarantine inspection is not effective in preventing the spread of influenza virus.^17,18 It has been determined that between the large number of people in the incubation period (thus not showing any symptoms), the low accuracy of the inspection kits used, and the poor cost-effectiveness, quarantine inspection in itself is not effective in preventing the spread of respiratory viruses. However, follow-up information obtained from passengers, follow-up surveys distributed to passengers, and information disseminated on symptoms to be aware of are believed to be important in mitigating the secondary spread of viruses.

CRUISE SHIP MEDICINE

Nearly 10 million people travel on cruise lines each year, the majority of whom are from North America. With an average customer age of 55 years on many ships, the number of people with chronic medical conditions can be quite high.¹⁹ Large vessels carry >2000 passengers and 1000 crew, resulting in a uniquely isolated environment with a high probability of encountering sick patients.²⁰

The most common complaints seen in the ship's infirmary are shortness of breath and injuries. Other complaints are outlined in Table 4-7. On a typical week-long cruise with 1100 passengers, it is estimated that there will be an average of four potentially life-threatening conditions, with one patient terminating the cruise early as a result.¹⁹ The decision to continue onboard treatment, to transport to a shore-based facility, or to arrange aeromedical evacuation must be made in light of weather forecasts, predicted flight time, and the quality of local resources. This choice is often made in conjunction with online medical support services provided by the cruise line.

WILDERNESS MEDICINE

Mass gathering events that are located within a wilderness environment can present unique challenges to the provision of medical care. Ideally, medical directors for wilderness mass gathering events should be experienced in both wilderness medicine and EMS. The 16-hour National Association of EMS Physicians/Wilderness Medical Society's Wilderness EMS Medical Directors Course provides concrete skills that are beneficial to a medical director for a wilderness mass gathering event. These events can occur in environments with extremes of temperature that medical personnel should be prepared to manage, both for themselves and for the care of patients. Most significantly, mass gatherings in wilderness environments can present challenges in the extrication of patients and may necessitate the use of alternative means of transport such as horses, snowmobiles, and aircraft.

ULTRA-DISTANCE ATHLETIC EVENTS

One of the clinical situations often encountered during exercise, particularly in individuals involved in endurance events such as marathons, triathlons, and ultra-distance athletic races, is the management of fluid and electrolyte repletion, specifically severe and potentially life-threatening hyponatremia. Exercise-associated hyponatremia, first described in the early 1980s, is defined as serum sodium below the normal reference range of the laboratory occurring during or up to 24 hours after prolonged physical activity.^21,22 Both fluid intake in excess of fluid loss and impaired urinary water excretion due to persistent secretion of antidiuretic hormone are important pathologic mechanisms contributing to this rapid, predominately dilutional decrease in serum sodium. Risk factors for developing exercise-associated hyponatremia include a high rate of fluid consumption during and after exercise (often associated with weight gain compared with prerace weight), exercise time longer than 4 hours, female sex, and a low body mass index.²³

Athletes presenting to first aid tents during ultra-distance events should be evaluated for electrolyte abnormalities.²⁴ Although a serum sodium level should ideally be checked before administering IV fluids, this may not always be feasible in the mass gathering environment. Therefore, it is critical to be able to identify individuals with signs and symptoms consistent with hyponatremia and to differentiate those with life-threatening presentations. The majority of hyponatremic athletes are asymptomatic or mildly symptomatic, with manifestations such as nausea and vomiting, malaise, lightheadedness, dizziness, headache, and fatigue. Severe, life-threatening manifestations include confusion, seizures, and coma, which may indicate the development of cerebral edema and impending death.

Hyponatremia during athletic events is best managed by preventative means. Oral rehydration using fluids that contain both carbohydrates and sodium, as found in commercial "sports drinks," results in less of a dilutional effect; however, they are still relatively hypotonic compared to plasma. It has also been previously suggested that maintaining a fluid balance during the event by limiting drinking to <500 mL/h will help to prevent hyponatremia. However, given the wide variation in sweat production and renal water excretion between individual athletes, and in the same individual depending on conditions during the race, it is not feasible to develop specific universal guidelines. Overall, recommendations for endurance athletes support the concept of drink according to thirst.²²

Athletes presenting with the clinical manifestation of mild to moderate hyponatremia should have fluid restriction and observation until the onset of spontaneous diuresis rather than administration of hypertonic saline, since similar symptoms may occur in hypernatremia.^22,25 However, among those with severe symptoms, when it is not feasible to measure serum sodium due to the constraints of the mass gathering event, treatment should be initiated empirically. Recommendations suggest an initial 100 mL bolus of 3% hypertonic saline, which should raise the serum sodium by 2 to 3 mEq/L. The bolus can be followed by an infusion rate of 3% hypertonic saline at 2 to 3 mL/kg/h to establish an increase in the serum sodium concentration of 4 to 5 mmol/L over the first 1 to 2 hours in order to reverse the osmotic gradient.²⁶ An alternative approach is to administer an additional two boluses of 100 mL of 3% hypertonic saline every 10 minutes until life-threatening symptoms have resolved.²⁷ Once clinical improvement occurs, the rate of infusion is decreased to follow the guidelines recommend for the safe correction of chronic hyponatremia (maximum increase of 12 mmol/L over 24 hours).²⁶

CARDIAC ARRESTS

Although cardiac arrests comprise a small percentage of medical occurrences at mass gathering events, results can be detrimental if planners are not well prepared for this potential need. At the very least, planners should prepare to have an adequate number of automated external defibrillators and make calculated decisions as to where these devices should be placed to minimize response time for all locations within the event. Planners should also consider the placement of ambulances within the event for easy egress and the provision of advance life support care.

MASS CASUALTY

In planning for a mass gathering, the event medical director should be cognizant of and prepared for the potential of a mass casualty incident. Plans should include methods of triage, coordination of the mass casualty with local EMS, and distribution of large numbers of patients as needed to area acute care facilities. Ultimately, the medical teams should function seamlessly in the Incident Command System structure such that patient flow is managed in the same manner regardless of the numbers of patients seen at any point in time and the potential influx of large numbers of patients in the event of a mass casualty situation.