Upon arriving at an accident, a bicycle is seen pinned under the front of the car.  A 7 year old lies sprawled across the pavement in front of the vehicle.  Skin is cool and mottled, breathing rapid and shallow, pulse is rapid, and blood pressure is near normal.  The boy is in shock, his body is trying to compensate for internal bleeding by an increase in heart rate and cardiac output.  Perfusion, or blood flow, is inadequate despite a normal blood pressure.  Later, an elderly female is the concern of her family.  Suddenly she became unresponsive, her left arm lies limp, and she can not speak.  She meets all the criteria for a stroke.  Her blood pressure is 194/124.   These are two very different persons presenting with very different signs, symptoms, and challenges for pre-hospital care.  But for both, the accurate measurement of blood pressure and assessment of tissue perfusion are critical for treatment and long term outcomes.

 

The goals of blood flow are to optimize the oxygen balance between supply and demand as well as maximize oxygen delivery.  A persons body compensates quickly following an acute episode of injury or illness, measurements may vary over time due to many factors.  Blood pressure represents not only the force that drives blood flow to the person’s vital organs but is also a reflection of the effort of the cardiovascular system.  It is the pressure of circulating blood against the walls of the arteries, veins, and chambers of the heart.  Systolic (top number), is the pressure exerted against the walls of the arteries as the left heart pumps out oxygenated blood.  Diastolic (bottom number), is pressure at rest, when the heart is not pumping.  Any factor that increases resistance of the vessels to the flow of blood or that affects the amount of blood pumped by the heart will change the blood pressure.  It may increase with age, mainly because the veins do not dilate as well.

 

Perfusion is the delivery of adequate volumes of oxygenated blood to sustain life under normal conditions.  Swift deterioration in blood pressure can signal a serious problem for patients because of the potential complications of  lack of oxygen to the tissue and systems failure.  For this reason pre-hospital care must be quick to recognize the signs and symptoms of low blood pressure, which remains one of the best indicators of internal bleeding from trauma.

 

To help assess the status of a patient, relying on the level of consciousness is very important.  A reduction in blood pressure may precede a reduced level of consciousness.  Dizziness or lightheadedness upon standing can be an excellent indication of reduced brain perfusion.  Problems related to blood pressure, including hemorrhage and the resulting decrease in pressure and the response to elevated blood pressure, both acute and chronic, are some of the most common reasons for calling EMS.

 

A variety of therapies are initiated based on blood pressure readings and overall patient assessment during pre-hospital assessment, treatment, and transport.  It is important to consider the readings within the overall context of the person’s status, both physical and mental. Remember, many things can affect the accuracy of the reading.  If at all possible, measurements should be compared with a patient’s normal blood pressure reading, which in an emergency is difficult to do.  Persons requiring care often need support with fluids to increase the pressure.  High blood pressures or stroke victims may be in need of medications.  Regardless, if you suspect abnormally high or low blood pressure, contact 911 for the nearest EMS, you need medical assistance.