Confined space medicine is a practice that is used in areas with limited access and potentially decreased ventilation. This is often due to structural collapse of buildings secondary to natural disasters such as earthquakes, hurricanes, or tornadoes. However, it may also be due to a terrorist blast, fire, or poor building standards. There may be small numbers of victims such as in a house collapse or a mass-casualty event such as the 1995 bombing of the Alfred P. Murrah building in Oklahoma City which resulted in 168 deaths and the 2001 World Trade Center attack which resulted in over 3000 deaths.
Types of Building Collapse
There are 4 general types of building collapse:
Urban Search and Rescue
Urban search and rescue (USAR) is a unique discipline involving the location, extrication, and stabilization of victims from confined spaces such as a building collapse. This is a multi-hazard discipline involving all types of disasters. USAR team members include search and rescue personnel, structural specialists, and medical staff including physicians. No matter what the cause of the collapse or the number of victims, the priority is the safety of the rescuer. The structural engineer is the one on the response team responsible for determining the relative safety of the site. Recognizing the importance of being careful with secondary collapse is paramount. However, the final decision to enter the scene is that of the team leader. Appropriate equipment is necessary. This includes helmet, dust mask, ear plugs, safety glasses, heavy duty gloves, steel toe boots, and coveralls. On an international level, USAR is organized by the International Search and Rescue Advisory Group (INSARAG) which is part of the United Nations Office for the Coordination of Humanitarian Affairs and is a global network of more than 80 countries. In the United States, the Federal Emergency Management Agency has 28 teams across the country. Europe has similar rescue groups, and there are volunteer USAR teams throughout the world.
There are 5 stages to a USAR operation: reconnaissance, medical assessment of victims, a search of other areas for live victims, removal of small debris by "bucket brigades," and the removal of larger debris by heavy equipment. Victims can be reached by rescue dogs or even rescue robots. Acoustic microphones may also detect them. The assessment of the victims can be achieved verbally or by cameras including fiberoptic devices.
There is a “golden day” of 24 to 48 hours after the event for which treatment is critical. However, there is no actual golden hour. If rescuers cannot immediately get to these victims, they will often die. Patients who die in the first 24 hours usually do so from either shock or airway issues; whereas, patients who die in after 24 hours usually do so from sepsis or multi-organ failure. Injuries in collapsed structures may include fractures, multiple trauma, lacerations, closed head injury, hypothermia, dehydration, and crush injury/crush syndrome. In addition, there may be injuries from the inhalation of toxic fumes or dust.
Managing the airway in a confined space begins with the basic standard equipment including suction, bag valve mask, oral airways, laryngoscope, nasotracheal tubes, and endotracheal tubes. Other equipment such as the laryngeal mask airway, esophageal obturator airway, esophageal, gastric tube airway, lighted stylet, and cricothyrotomy kits may be useful. Extended length tubing for oxygen may be necessary. If there is a concern of dust inhalation, then albuterol or ipratropium may be useful.
Intubating in such a constricted space has unique challenges. In line, c-spine stabilization may be difficult or impossible. There are the technical challenges of the impossibility of intubating from the standard position from behind the patient. This will often require the face-to-face technique also known as inverse intubation or icepick intubation. Although the laryngoscope is still held with the right hand and the handle toward the patient’s feet, the incubator may be on the side of the patient or straddle the patient. There is no clear, proven advantage of video laryngoscopy in this position when compared with the traditional laryngoscope blades. Another technique that may be useful in the unconscious patient is digital intubation where the rescuer uses his or her fingers to lift the epiglottis and then slide the tube through the glottis and into the trachea. A cricothyrotomy may need to be performed, and in a recent study, the Quicktrak proved faster to insert than the Melker kit. This was thought to be because the Quicktrack has fewer parts and requires less manipulation.
Mild to severe chest injuries can occur, with the worst often being fatal. A tension pneumothorax should be treated either by needle application, finger thoracostomy, or chest tube placement. If needle application is to be performed, current studies show that there is greater success with a longer needle catheter such as a 14 gauge 5 cm needle with a 4.5 cm catheter sheath. More importantly, success is also tied to insertion of the needle in either the 4-5 intercostal space at the mid-axillary or anterior axillary line as opposed to placement at the 2 intercostal space midclavicular line which is what was previously taught.
Crush Injury and Crush Syndrome
Crush injury and crush syndrome may be encountered. The crush injury is the direct injury to the limb or organ by compressive forces whereas the crush syndrome is the systemic effects of the crush injury. These systemic effects include rhabdomyolysis, renal failure, sepsis, acute respiratory distress syndrome, disseminated intravascular coagulation, bleeding, arrhythmias, electrolyte imbalance. It is the second most frequent cause of death from earthquakes, the first being trauma. The pathophysiology includes impaired kidney perfusion and intratubular obstruction by myoglobin and uric acid.
The treatment emphasizes early fluid resuscitation even while the victim is under the rubble. One should start an intravenous line with normal saline at 1000 mL per hour tapered by 50% after 2 hours for adults and 20 mL/kg per hour for children for the first 2 hours and then 10cc/kg per hour. However, in the elderly, children, or those with volume overload, then less fluid should be given. If one is unable to place an intravenous line, then one can attempt to place an intraosseous line. If neither of these is possible, then one can consider hypodermoclysis which is administering subcutaneous, intravenous fluids at 1 mL per minute. One can access more than one site by this route and deliver up to 3 L per day. Lactated ringers should be avoided as it contains potassium which can worsen already life-threatening hyperkalemia is certain patients. In general, 3 to 6 L should be given over the first 6 hours while monitoring the patient’s hemodynamic status and urine output. If there is anuria (after hypovolemia is excluded), then give only 500 to 1000 mL per day in addition to fluid losses. If close monitoring is impossible, then give up to 3 to 6 L of intravenous fluid per day. However, if close monitoring is possible, then one can give more than 6 L per day.
Once the victim is extricated, one can then add 50 meq of sodium bicarbonate to each liter of half-normal saline (combined produces a solution nearly isotonic) to maintain urinary pH over 6.5. Patients in rhabdomyolysis need approximately 200 to 300 meq of bicarbonate a day.
Mannitol is controversial both regarding its proven efficacy in traumatic rhabdomyolysis and its side effect profile. On the one hand, it may be useful to increase extracellular volume and prevent the deposition of renal tubular casts; on the other hand, it may also lead to heart failure and renal toxicity if not dosed properly. Mannitol is contraindicated in oliguria, hypervolemia, hypertension, and heart failure, so the decision to give this should not be automatic. Mannitol, if used, should be given as a 60 ml dose of 20% mannitol given over 3 to 5 minutes to test if there is a urinary response. Mannitol should only be continued if there is a 30 to 50 mL per hour increase in urinary output over baseline. The dose of mannitol is 1 to 2 gm/kg per day for a total of 120 gm per day at a rate of 5 gm per hour.
Several electrolyte abnormalities may be present. Hypocalcemia should only be treated if one is symptomatic as one may later develop hypercalcemia. Start with 10 mL of intravenous calcium gluconate 10% or 5 mL of intravenous calcium chloride 10% over 2 minutes. Hyperkalemia should be monitored and treated as needed based on the potassium level and more importantly, electrocardiographic changes. If there are severe or life-threatening electrocardiographic changes or arrhythmias such as the widening of the QRS to third-degree heart block or pulseless electrical activity, the intravenous calcium gluconate or chloride should be given immediately. It may be necessary to give several doses every 10 minutes to achieve the cardioprotective effects of calcium. If the patient is acidotic then sodium bicarbonate 1 meq/kg should be given intravenously over several minutes. To drive the potassium into the cells, 10 units of intravenous insulin, together with 1 to 2 ampules of D50, should be given. In addition, albuterol inhalations should be given. Kaexylate with sorbitol can be given orally at 25 to 50 gm, or it may be given as a retention enema. Patients with life-threatening hyperkalemia may require dialysis. One of the critiques of recent missions to disaster sites is that there were not enough dialysis machines to treat those with renal failure secondary to crush injuries. Blood products should be given as necessary.
One of the more severe complications of crush injury is compartment syndrome. One should monitor for the “5Ps” which includes: pain, paresthesias, paralysis, pallor, and pulselessness. However, it is important to realize that pain out of portion to the exam may be present before the other symptoms and may be the initial presentation of compartment syndrome. A more objective measure is to detect pressures within the compartment. A pressure greater than 40 mm hg indicates the need for a fasciotomy, Although there is no consensus regarding the exact number, some sources recommend an intracompartmental pressure of greater than 30 mm Hg, or a less than 30 mm Hg difference between intracompartmental pressure and diastolic blood pressure as an indication for fasciotomy.
Confined space medicine involves a multi-hazard and multidisciplinary approach to the treatment of victims trapped in a structural collapse. There are unique challenges to both the initial treatment of such victims regarding airway management as well as the treatment of crush syndrome.