Читать книгу Emergency Medical Services - Группа авторов - Страница 185

The treatment of shock must be customized to the individual EMS agency and geographic location. In the urban setting with short transport times, the victim of a penetrating cardiac wound would probably benefit most from airway maintenance and rapid transport to the hospital. IV or intraosseous (IO) access could be attempted en route, if it will not delay delivery to definitive care [48]. On the other hand, with longer transport times in the rural setting, a similar patient might benefit from a carefully titrated crystalloid volume infusion during transport. Fluid delivery could be initiated while the patient is en route to the hospital, thereby prolonging neither scene time nor time until definitive care [49]. In the patient who presents a difficult IV access problem, IO infusions may be attempted. Placing the IO needle in the humeral head may result in faster infusion rates than the proximal tibia.

The ideal fluid for use in the field would be small in volume, portable, non‐allergenic, inexpensive, and would not interfere with clotting factors [35]. Unfortunately, this ideal fluid has yet to be discovered. Isotonic crystalloids are currently the fluid of choice for out‐of‐hospital resuscitation in the United States [1, 36, 49, 50]. Among critically ill patients requiring large volume resuscitation, there is a benefit of balanced crystalloid solutions over normal saline but there is insufficient evidence to recommend them for initial resuscitation. Moreover, as they are relatively hypotonic, they may be detrimental in traumatic brain injury [51]. Crystalloid fluids are inexpensive and widely available but may contribute to dilutional coagulopathy, hyperchloremic acidosis, and hypothermia when given in large volumes.

Whole blood would arguably provide the greatest benefit as a resuscitative fluid in the setting of hemorrhagic shock but lacks availability due to issues of cost, storage, and limited supply. Use of blood products in the prehospital environment is generally limited to a few air medical services and EMS systems that carry blood for administration to victims of hemorrhagic shock. Prehospital administration of plasma reduces mortality in trauma victims but suffers the same limitations as blood administration [52]. Freeze‐dried plasma that has a long shelf life and can be made readily available is being used outside the United States. It may become important in prehospital resuscitation [53–55].

The optimal volume of fluids to administer in the field is not known, especially in the trauma victim with uncontrolled hemorrhage [36, 48, 49,56–61]. Current trauma algorithms call for the administration of IV fluid for all major trauma victims. Insufficient fluid volume may allow exposure to increasing “doses” of hypotension, leading to worsening mortality from hypoperfusion [62]. Evidence suggests, however, that attempts at normalization of blood pressure with a large volume of fluids in a patient with uncontrolled hemorrhagic shock may be deleterious to patient outcome. Complications may include acidosis, dislodgement of blood clots, and dilution of clotting factors [56]. In such a patient, it appears that the best course is to give sufficient crystalloid to maintain perfusion (such as a peripheral pulse and mentation) pending the delivery of the patient to the appropriate facility [57–59].

Extremity veins are the typical sites for venous access. External jugular veins are also useful in many patients. Few EMS systems use central venous access. IO access has become so important as a method of vascular access that it is supported by a position statement from the National Association of EMS Physicians [63]. In patients in extremis or cases in which peripheral access is not immediately available, IO access may be preferred.