and the back of the hands will be hard todistinguish.There are frequent complaints of thirst. Even theseverely wounded may complain of thirst ratherthan pain.The kidneys may shut down. Urine formationeither ceases or greatly diminishes if the systolicblood pressure falls below 80 for long periods oftime.The person may faint from inadequate venousblood return to the heart. This may be the resultof a temporary gravitational pooling of the bloodassociated with standing up too quickly.HYPOVOLEMIC SHOCKHypovolemic shock is also known as oligemic orhematogenic shock. The essential feature of all formsof hypovolemic shock is loss of fluid from thecirculating blood volume, so that adequate circulationto all parts of the body cannot be maintained.Hemorrhagic ShockIn cases where there is internal or externalhemorrhage due to trauma (hemorrhagic shock), thereis a loss of whole blood, including red blood cells. Thediminished blood volume causes a markedly lessenedcardiac output and reduced peripheral circulation.This results in reduction of oxygen transported to thetissues (hypoxia); reduction of perfusion, thecirculation of blood within an organ; and reduction ofwaste products transported away from the tissue cells.Under these conditions, body cells are able to carry ontheir normal functions for only a short period of time.The body tries to restore the circulatory volume bysupplying fluid from the body tissues. The result is aprogressive fall in the hematocrit (ratio of red bloodcells to plasma) and in the red blood cell count.Burn ShockIn burn shock, on the other hand, there is aprogressive increase in the hematocrit and red bloodcell count. This increase is due to hemoconcentrationfrom loss of the plasma fraction of the blood into andthrough the burned area.NEUROGENIC SHOCKNeurogenic shock, sometimes called vasogenicshock, results from the disruption of autonomicnervous system control over vasoconstriction. Undernormal conditions, the autonomic nervous systemkeeps the muscles of the veins and arteries partiallycontracted. At the onset of most forms of shock,further constriction is signaled. However, the vascularmuscles cannot maintain this contraction indefinitely.A number of factors, including increased fluid loss,central nervous system trauma, or emotional shock,can override the autonomic nervous system control.The veins and arteries immediately dilate, drasticallyexpanding the volume of the circulatory system, with acorresponding reduction of blood pressure.Simple fainting (syncope) is a variation ofneurogenic shock. It often is the result of a temporarygravitational pooling of the blood as a person standsup. As the person falls, blood again rushes to the head,and the problem is solved. Neurogenic shock may alsobe induced by fear or horror, which will override theautonomic nervous system control.Shell shock and bomb shock are other variations ofneurogenic shock that are important to the HospitalCorpsman. These are psychological adjustmentreactions to extremely stressful wartime experiencesand do not relate to the collapse of the cardiovascularsystem. Symptoms range from intense fear to completedementia and are manifestations of a loss of nervouscontrol. Care is limited to emotional support of thepatient and his evacuation to the care of a psychiatristor psychologist.4-23Figure 4-19.—Symptoms of shock.
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