Call after call, we search the patient for the obvious or unexpected in an attempt to save the lives of those we treat.  Sometimes our observations set the stage for a patient’s remarkable recovery.   Other times, the rest of the medical community ridicules our observations.  The patient lies on your stretcher awaiting your care.  But how much do you really know about your patient?  Do you appreciate the intricate network of channels and valves that circulate a mysterious substance?  Do you appreciate the miracle of a pump that in design is elegant, yet has the ability to determine that something is wrong and work to fix the problem long before the patient or you has ever determined that one exists?  With as much progress that mankind has made in the last 70 years in the fields of science, math, and related fields, we will always be surpassed by the design and function of the human body.

Hypertension

Blood pressure is the force of blood against the walls of arteries. Blood pressure rises and falls during the day. When blood pressure stays elevated over time, it is called high blood pressure. The medical term for high blood pressure is hypertension. High blood pressure is dangerous because it makes the heart work too hard and contributes to atherosclerosis (hardening of the arteries). It increases the risk of heart disease and stroke, which are the first- and third-leading causes of death among Americans. High blood pressure also can result in other conditions, such as congestive heart failure, kidney disease, and blindness.

A blood pressure level of 140/90 mmHg or higher is considered high for most people. About two-thirds of people over age 65 have high blood pressure. If your blood pressure is between 120/80 mmHg and 139/89 mmHg, then you have prehypertension. This means that you don’t have high blood pressure now but are likely to develop it in the future. You can take steps to prevent high blood pressure by adopting a healthy lifestyle.  Those who do not have high blood pressure at age 55 face a 90 percent chance of developing it during their lifetimes. So high blood pressure is a condition that most people have at some point in their lives.

Both numbers in a blood pressure test are important, but for people who are 50 or older, systolic pressure gives the most accurate diagnosis of high blood pressure. Systolic pressure is the top number in a blood pressure reading. It is high if it is 140 mmHg or above.  On the ambulance (or in an acute setting), we are usually more focused on the systolic measurement of blood pressure. In more controlled and clinical settings (like a clinic), the diastolic measurement is just as important as increased systolic blood pressure

Effects of High Blood Pressure

High blood pressure is the most important risk factor for stroke. Very high pressure can cause a break in a weakened blood vessel, which then bleeds in the brain. This can cause a stroke. If a blood clot blocks one of the narrowed arteries, it can also cause a stroke.  High blood pressure can eventually cause blood vessels in the eye to burst or bleed. Vision may become blurred or otherwise impaired and can result in blindness. As people get older, arteries throughout the body “harden,” especially those in the heart, brain, and kidneys. High blood pressure is associated with these “stiffer” arteries. This, in turn, causes the heart and kidneys to work harder. The kidneys act as filters to rid the body of wastes. Over time, high blood pressure can narrow and thicken the blood vessels of the kidneys. The kidneys filter less fluid, and waste builds up in the blood. The kidneys may fail altogether. When this happens, medical treatment (dialysis) or a kidney transplant may be needed. High blood pressure is a major risk factor for heart attack. The arteries bring oxygen-carrying blood to the heart muscle.  In hypertension, the higher than normal pressures exerted on the blood pressure wall often result in damage.  This damage results in calcium and plaque deposits on the arteries (as a result of the clotting cascade or healing process) resulting in narrowed coronary arteries.  The problem is worsened by the fact that high blood pressure results in higher than normal myocardial oxygen demand which over time will increase while the capacity of the coronary artery to replenish the myocardium is decreased.  High blood pressure is the number one risk factor for congestive heart failure (CHF). CHF is a serious condition in which the heart is unable to pump enough blood to supply the body’s needs.

Shock

Shock or hypoperfusion is a condition that will take the life of your patient unless critical interventions are made in a timely manner.  As an EMT, you were trained to recognize and treat shock.  Treating shock can be simple or complicated depending upon the underlying cause.  This part of the lecture will cover shock, its causes, and associated treatment.  No matter what type of shock you are dealing with, there are some interventions that are always appropriate.  High flow oxygen, keeping the patient warm, stopping bleeding (when bleeding is present and can be stopped), and rapid transport are the primary treatments for shock and should be performed for all types of shock.  Communication with the emergency department is another key that will help ensure your patient survives.  Much of what we know today come from efforts of the military, which forms the majority of what we know about shock today.  Another contributor to the body of knowledge about shock comes from a Dr. R. Adams Cowley of Maryland.  Dr. Cowley, a cardiologist by trade noticed shock and referred to it as a “momentary lapse before death.”  Dr. Cowley’s research paved the way for the modern EMS system and our understanding and treatment of shock.  To this day, the EMS and trauma centers of Maryland carry on the work of Dr. Cowley.  Our understanding of shock allows us to identify and treat shock, and in some cases, anticipate and completely avoid it.

Shock is a serious, life-threatening medical condition where insufficient blood flow reaches the body tissues for oxygenation. As the blood carries oxygen and nutrients around the body, reduced flow hinders the delivery of these components to the tissues, and can stop the tissues from functioning properly. The process of blood entering the tissues is called perfusion, so when perfusion is not occurring properly this is called a hypoperfusional (hypo = below) state. Medical shock should not be confused with the emotional state of shock (i.e. you learn that you just won the lottery and pass out), as the two are not related. Medical shock is a life-threatening medical emergency and one of the most common causes of death for critically ill people. Shock can have a variety of effects, all with similar outcomes, but all relate to a problem with the body’s circulatory system. For example, shock may lead to hypoxia (a lack of oxygen in the body tissues) or cardiac arrest (the heart stopping)

There are three stages (but more in some medical texts) of shock, although shock is a complex and continuous condition and there is no sudden transition from one stage to the next.

• Compensatory (Compensating) – The body employing physiological mechanisms, including neural, hormonal, and bio-chemical mechanisms characterize this stage in an attempt to reverse the condition. As a byproduct of metabolism, the body makes waste various waste products.  Many of the waste products are simply discarded through one system or another, however special attention must be given to the destruction of acids.  Normally, the body would (using some enzymes) remove the hydrogen from the acidic compounds and combine with other elements in the body to form a volatile acid (an acid that can be broken down into carbon dioxide and water).  In shock, the acidic compounds created are not as easily broken down and build up in the blood stream.  The result is a metabolic acidosis and as a result of the acidosis, the person will begin to hyperventilate in order to rid the body of carbon dioxide (thinking the acidosis is from volatile acids). The baroreceptors in the arteries detect the resulting hypotension, and cause the release of epinephrine and norepinephrine. Norepinephrine causes predominately vasoconstriction with a mild increase in heart rate, whereas epinephrine predominately causes an increase in heart rate with a small effect on the vascular tone; the combined effect results in an increase in blood pressure. Renin-angiotensin axis is activated and arginine vasopressin is released to conserve fluid via the kidneys. Also, these hormones cause the vasoconstriction of the kidneys, gastrointestinal tract, and other organs to divert blood to the heart, lungs and brain. The lack of blood to the renal system causes the characteristic low urine production. However the effects of the Renin-angiotensin axis take time and are of little importance to the immediate homeostatic mediation of shock.
• Progressive (Decompensated) – Should the cause of the crisis not be successfully treated, the shock will proceed to the progressive stage and the compensatory mechanisms begin to fail. Due to the decreased perfusion of the cells, sodium ions build up within while potassium ions leak out. As anaerobic metabolism (a backup metabolism that temporarily exists in the absence of oxygen) continues, increasing the body’s metabolic acidosis, the arteriolar and precapillary sphincters constrict such that blood remains in the capillaries. Due to this, the hydrostatic pressure will increase and, combined with histamine release, this will lead to leakage of fluid and protein into the surrounding tissues. As this fluid is lost, the blood concentration and viscosity increase, causing sludging of the microcirculation. The prolonged vasoconstriction will also cause the vital organs to be compromised due to reduced perfusion.
• Refractory (Irreversible) – At this stage, the vital organs have failed and the shock can no longer be reversed. Brain damage and cell death have occurred. Various conditions are associated with this stage of shock (most notably Acute Respiratory Distress Syndrome).  This patient may be managed temporarily on a ventilator, dialysis, cardiac balloon pumps, and other adjuncts in the intensive care unit.  Death is usually the outcome.  A goal of treating shock is to ensure that the patient never makes it to refractory shock.  Since you never really know what stage of shock the patient has progressed to, your treatments may be in vain.  Nevertheless, treat known or suspected shock aggressively and in accordance with your local protocols.

In 1972 Hinshaw and Cox suggested the following classification that is still used today. It uses four types of shock: hypovolemic, cardiogenic, distributive, and obstructive shock:

• Hypovolemic shock – This is the most common type of shock and based on insufficient circulating volume. Its primary cause is loss of fluid (any fluid) from the circulation from either an internal or external source. An internal source may be hemorrhage. External causes may include extensive bleeding, high output fistulae (a connection between a hollow organ and an adjacent organ) or severe burns (plasma loss).
• Cardiogenic shock – This type of shock is caused by the failure of the heart to pump effectively. This can be due to damage to the heart muscle, most often from a large myocardial infarction. Other causes of cardiogenic shock include arrhythmias, cardiomyopathy, congestive heart failure (CHF), contusio cordis (like the kid who gets hit in the chest with a baseball and goes into cardiac arrest – Hashimoto’s syndrome), or cardiac valve problems.
• Distributive shock – As in hypovolemic shock there is an insufficient intravascular volume of blood. This form of “relative” hypovolemia is the result of dilation of blood vessels, which diminishes systemic vascular resistance. Examples of this form of shock are:
  • Septic shock – This is caused by an overwhelming infection leading to vasodilation, such as by Gram negative bacteria i.e. Escherichia coli, Proteus species, Klebsiella pneumoniae, which release an endotoxin which produces adverse biochemical, immunological and occasionally neurological effects which are harmful to the body. Gram-positive cocci, such as pneumococci and streptococci, and certain fungi as well as Gram-positive bacterial toxins produce a similar syndrome.
  • Anaphylactic shock – Caused by a severe anaphylactic reaction to an allergen, antigen, drug or foreign protein causing the release of histamine, which causes widespread vasodilation, leading to hypotension and increased capillary permeability.
  • Neurogenic shock – is shock caused by the sudden loss of the autonomic nervous system signals to the smooth muscle in vessel walls. This can result from severe central nervous system (brain and spinal cord) damage. With the sudden loss of background sympathetic stimulation, the vessels suddenly relax resulting in a sudden decrease in peripheral vascular resistance and decreased blood pressure.
    • Spinal Shock is a form of neurogenic shock  Spinal shock  is caused by trauma to the spinal cord resulting in the sudden loss of autonomic and motor reflexes below the injury level. Without stimulation by sympathetic nervous system the vessel walls relax uncontrolled, resulting in a sudden decrease in peripheral vascular resistance, leading to vasodilation and hypotension.
• Obstructive shock – In this situation the flow of blood is obstructed which impedes circulation and can result in circulatory arrest. Several conditions result in this form of shock.
  • Cardiac tamponade in which blood in the pericardium prevents inflow of blood into the heart (venous return). Constrictive pericarditis, in which the pericardium shrinks and hardens, is similar in presentation.
  • Tension pneumothorax. Through increased intrathoracic pressure, bloodflow to the heart is prevented (venous return).
  • Massive pulmonary embolism is the result of a thromboembolic incident in the bloodvessels of the lungs and hinders the return of blood to the heart.
  • Aortic stenosis hinders circulation by obstructing the ventricular outflow tract

Without knowing what to look for, it is possible to completely miss shock.  Since there is no transition between the stages of shock, we must treat according to what we see.  Pediatric patients are extremely tricky to discover shock due to the fact that the infants and children have the ability to vasoconstrict for long periods of time, delaying the progression of symptoms that we normally associate with shock (and when they start displaying shock like symptoms, the progression between the stages is quick and sure).  A pediatric patient can be treated according to the mechanism of injury before the presence of shock symptoms are seen.  Always treat shock aggressively (and transport to a facility that is capable of continuing your care where you left off) and in accordance with your local protocols. 

• Hypovolemic shock
  • Anxiety, restlessness, altered mental state due to decreased cerebral perfusion and subsequent hypoxia.
  • Hypotension due to decrease in circulatory volume.
  • A rapid, weak, thready pulse due to decreased blood flow combined with tachycardia.
  • Cool, clammy skin due to vasoconstriction and stimulation of vasoconstriction.
  • Rapid and shallow respirations due to sympathetic nervous system stimulation and acidosis.
  • Hypothermia due to decreased perfusion and evaporation of sweat.
  • Thirst and dry mouth, due to fluid depletion.
  • Fatigue due to inadequate oxygenation.
  • Cold and mottled skin (cutis marmorata), especially extremities, due to insufficient perfusion of the skin.
  • Distracted look in the eyes or staring into space, often with pupils dilated.
• Cardiogenic shock, similar to hypovolemic shock but in addition:
  • Distended jugular veins due to increased jugular venous pressure.
  • Absent radial pulse due to tachyarrhythmia.
• Obstructive shock, similar to hypovolemic shock but in addition:
  • Distended jugular veins due to increased jugular venous pressure.
  • Pulsus paradoxus (as seen with a different blood pressure on inspiration than expiration of >10mm/Hg) in case of cardiac tamponade
• Septic shock, similar to hypovolemic shock except in the first stages:
  • Pyrexia and fever, or hyperthermia, due to overwhelming bacterial infection.
  • Vasodilation and increased cardiac output due to sepsis.
• Neurogenic shock, similar to hypovolemic shock except in the skin’s characteristics. In neurogenic shock, the skin is warm and dry.
• Anaphylactic shock
  • Urticaria (rash).
  • Localized edema, especially around the face.
  • Weak and rapid pulse.
  • Breathlessness and cough due to narrowing of airways and swelling of the throat.
  • Marked hypotension.

In the early stages, shock requires immediate intervention to preserve life. Therefore, the early recognition and treatment is paramount in the prehospital arena. The management of shock requires immediate intervention, even before a differential diagnosis is made. Re-establishing perfusion to the organs is the primary goal through restoring and maintaining the blood circulating volume ensuring oxygenation and blood pressure are adequate, achieving and maintaining effective cardiac function, and preventing complications. Patients attending with the symptoms of shock will have, regardless of the type of shock, their airway managed and oxygen therapy initiated. In case of respiratory insufficiency, intubation and mechanical ventilation may be necessary.  The aim of these acts is to ensure survival during the transportation to the hospital; they do not cure the cause of the shock. Specific treatment depends on the cause.