myocardial infarction, the heart will no longer be able  to  maintain  adequate  circulatory  pressure, even  though  the  volume  of  fluid  is  unchanged. Shock  will  develop  as  the  pressure  falls.  Heart  at- tack is an extreme medical emergency all corps- men must be ready to handle. It will be discussed in  greater  detail  in  the  “Common  Medical Emergencies”  section  of  this  chapter. Septic  Shock Septic  shock  usually  does  not  develop  for  2 to 5 days after an injury and the corpsman will not often see it in a first aid situation. It may ap- pear  during  the  course  of  peritonitis  caused  by penetrating abdominal wounds or perforation of the appendix. It may also result from gross wound contamination, rupture of an ulcer, or as a com- plication  of  certain  types  of  pneumonia.  Septic shock is the result of vasodilation of small blood vessels  in  the  wound  area,  or  general  vasodilation if  the  infection  has  entered  the  bloodstream.  In addition to increasing circulatory system volume, the  walls  of  the  blood  vessels  become  more permeable,  allowing  fluids  to  escape  into  the tissues. This type of shock carries a poor prognosis and must almost always be treated under the direct supervision  of  a  medical  officer. Anaphylactic Shock This type of shock occurs when an individual is exposed to a substance to which his or her body is particularly sensitive. In its most severe form, the body goes into an almost instantaneous violent reaction. A burning sensation, itching, and hives spread  across  the  skin.  Severe  edema  effects  body parts and the respiratory system. Blood pressure drops   alarmingly,   and   fainting   or   coma   may develop. The  causative  agent  may  be  introduced  into the  body  in  a  number  of  ways.  The  injection  of medicines, especially penicillin and horse- or egg- cultured serums, is one route. Another is the in- jection  of  venoms  by  stinging  insects  and  animals. The   inhalation   of   dusts,   pollens,   or   other materials to which a person is sensitive is a third route. Finally, a slightly slower but no less severe reaction  may  develop  from  the  ingestion  of  cer- tain foods and medications. Specific treatment of venoms  and  poisons  will  be  discussed  in  the “Poisons/Drug  Abuse”  section  of  this  chapter. GENERAL   TREATMENT PROCEDURES Intravenous fluid administration is the single most important factor in the treatment of any type of shock except cardiogenic shock. The proper use of  intravenous  equipment  and  fluids  are  discussed in   the   “Patient   Care”  chapter  of  the  manual. Ringer’s  lactate  is  probably  the  best  solution  to use,  although  normal  saline  is  adequate  until properly  cross-matched  whole  blood  can  be  ad- ministered. The electrolyte solutions replace not only  the  lost  blood  volume,  but  also  lost  extra- cellular  fluid  that  has  been  depleted  to  bolster  the shrunken blood volume. If the shock situation is severe  enough  to  warrant  immediate  adminis- tration  of  intravenous  fluids,  or  transportation to  a  medical  facility  will  be  delayed  and  a  medical officer  is  not  available  in  the  first  aid  situation to  write  an  administrative  order,  be  conservative. Start the intravenous fluid and let it run at a slow rate of 50 to 60 drops per minute. If intravenous solutions  are  unavailable  or  transportation  to  a medical  treatment  facility  will  be  delayed,  and there   are   no   contraindications   such   as gastrointestinal bleeding or unconsciousness, the patient  may  receive  an  electrolyte  solution  by mouth.  This  may  be  prepared  by  adding  a  tea- spoon of salt and half a teaspoon of baking soda to a quart or liter of water. Allow the patient to sip  the  solution. Pneumatic  Counter-Pressure  Devices (MAST) Commonly  known  as  Medical  Anti-Shock Trousers or Military Anti-Shock Trousers, these devices are designed to correct or counteract cer- tain   internal   bleeding   conditions   and hypovolemia. The garment does this by develop- ing  an  encircling  pressure  up  to  120  mm  Hg around  both  lower  extremities,  the  pelvis,  and  the abdomen.  The  pressure  created: 1. 2. 3. 4. Slows  or  stops  venous  and  arterial  bleeding in  areas  of  the  body  enclosed  by  the pressurized garment. Forces  available  blood  from  the  lower  body to the heart, brain, and other vital organs. Prevents  pooling  of  blood  in  the  lower extremities. Stabilizes fractures of the pelvis and lower extremities. 4-49