March 2, 2021
Samuel E. Greenberg, M.D
Most people know that Shock refers to a fall in blood pressure. Beyond that, they are ignorant of its causes. They do know that if it lasts long enough, that death will ensue. But does the blood pressure have to fall to zero for a person to be in shock? What is the blood pressure level at which shock is felt to be present? And how does the body deal with a fall in blood pressure?
Shock occurs when the pressure is too low to propel the blood forward to infuse into the major organs. These organs are the brain and kidney, foremost, and then the liver, heart, and the other organs thereafter. The actual blood pressure level, at which shock occurs, varies from person to person, but when the systolic blood pressure falls below 90 mm. of Mercury, most of the time shock occurs. Of course, irreversible damage may not occur immediately, and depends on the health and the age of the individual, but after some definable time, irreversible damage will set in and ultimately, death will occur.
Since Shock ensues when insufficient blood reaches the major organs, it is easy to figure out some of the causes of shock. The first one that comes to mind is when there is insufficient blood to move around, no matter how strong the pump is. This, of course, would occurs in bleeding states, and is called "Hemorrhagic Shock", a type of "Hypovolemic Shock" (diminished volume).This condition, of course, requires blood or blood products replacement to rectify. Additionally, the cause of the bleeding must be sought for and the bleeding must be stopped. In this type of shock, the body will send out chemicals which will constrict the peripheral arteries, which deliver blood to the skin and subcutaneous muscles, thus, shunting the blood to the deeper more vital organs. Hypovolemic Shock, also occurs in states when the fluid volume, aside from the blood cells, is diminished, as in severe dehydration. In this condition, replenishment of the fluid by a variety of liquids, either intravenously or orally will reverse the shock state.
A second common cause of SHOCK occurs when the pump, which in this case is the heart, is weakened and, despite an adequate amount of blood, the heart is unable to propel the blood to the vital organs. This condition most frequently occurs when the heart muscle is damaged, as with heart attacks (myocardial infarctions). This is a much more difficult condition to treat, than Hypovolemic shock and is referred to as Cardiogenic Shock. Treatment, of course, is to try and keep the blood pressure up sufficiently to propel the blood around, until the heart recovers, as by using an artificial pump, or by the use of medications which will shunt the blood from areas where it is needed less, such as the soft tissues and the skin, to the vital organs instead, where life can be sustained. The body is trying to do its thing, also, but needs help if the heart function is too severely depressed. In cases where there is an irregular heart rhythm, (arrhythmia), the heart function, because of, either the rapid or the irregular pulse, is unable to fill with enough blood during its resting phase to propel sufficient blood forward to the tissues.
Another, not infrequent, cause of SHOCK occurs when some toxin, either infectious or allergic, causes the blood vessels to dilate, which in effect shunts the blood away from the vital organs into vascular beds which supply less essential tissues, thus depriving the vital organs from receiving the blood they need to sustain life. This type of SHOCK is called MALDISTRIBUTION of flow or DISTRIBUTIVE SHOCK. This condition can occur in burns or acute pancreatitis, as other examples. In this group is included those conditions where the blood viscosity is thickened, such that the microcirculation is impeded, resulting in insufficient blood flow.
Conditions that thicken the blood and increase viscosity may include Polycythemia vera, multiple myeloma, and macroglobulinemia. Another synonym in "medical jargon" for this condition is Vasomotor Collapse". This condition is often suspected when there is a drastic drop in the blood pressure accompanied by a slow pulse. In trauma, for example, a reflex, involving the vagus nerve, will initiate a vasovagal reflex, which produces a slow pulse. Neurogenic shock, occurring in an occasional stroke, can manifest a vasodilatation resulting in distributive shock.
So, even though there are many different causes of shock, the clinical picture is fairly characteristic. There is profound arterial hypotension, restlessness and impaired mentality, diminished urine output, and shortness of breath. The person in shock generally is pale and sweaty with cool skin. Ultimately the person may complain of dizziness, dimming-then loss-of vision and, ultimately, pass out (Syncopy) and become comatose.
When Shock is suspected, the first thing to do is to lay the person in a supine position and, if necessary, to facilitate return of venous blood flow to the brain, place the person in a "heads down" position (Trendelenburg position). Concurrently, elevation of the feet will facilitate return of venous blood to the heart, where it can then be propelled to the vital organs, provided the heart pumping action is adequate. It has been estimated, that by merely placing the patient in a supine position with the feet 12 in. or more above the head will supply about 500cc's of blood for the central circulation. Restlessness, from diminished brain perfusion, may require sedation to help the person rest. Vomiting often occurs when the pressure falls, so that keeping the head turned sideways will minimize any aspiration of gastric secretions and subsequent lung complications. Intravenous fluids are needed to fill the vascular system for greater blood volume and this is the usual first interventional therapy offered. If the shock state continues, then vasopressors or cardio circulatory stimulants are then tried to shunt the blood to the vital organs. Inhalation Oxygen is mandatory, especially in carcinogenic shock, but may be valuable in septic or toxic shock, and shock due to injuries. Hypothermic shock is treated with warming techniques. Antibiotics are necessary in septic shock. Cortisone may be necessary in anaphylactic shock or adrenal insufficiency. Arrhythmic cardiogenic shock will require anti-arrhythmic measures varying from medication to electrical shock.
In many metabolic, toxic, or endocrinological causes of shock, secondary measures alone may not restore circulation. Identification and treatment of the specific underlying etiology is paramount in returning the circulation to a normal status.
Shock is the condition of insufficient blood flow to the vital organs, caused either by loss of intravascular volume, externally, as in bleeding or dehydration, or internally, as in extreme vasodilitation, or by loss of the ability of the heart to pump sufficient quantities of blood to those organs. The patient will exhibit central nervous system and circulatory symptoms and will require fluid replacement initially, followed secondly by medications intended to stimulate the cardiovascular system and ultimately by techniques or medications which will reverse the underlying etiology.
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