Most of the common signs and symptoms of anemia are the result of one or both of two disturbances. They are reduced oxygen carrying capacity and the hemodynamic effects of a decreased volume of blood.
A number of factors determine individual signs and symptoms of anemia. They are how low the red blood cell count drops, how fast it occurs, the presence of comorbidities, and the cause of the anemia. General signs and symptoms of anemia directly relate to the decreased amount of blood. Indirect signs and symptoms reflect the process or state which causes the anemia.
Oxygen carrying capacity is the amount of oxygen a quantity of blood is able to absorb for transport to tissues of the body. The bulk of oxygen in the blood is bound to hemoglobin. Therefore in states of anemia the oxygen carrying capacity is less than normal because of deficient amounts of hemoglobin.
Hemodynamic effects are the physical expressions of circulation (the flow of blood in the body). Their determinants are the force of contraction of the heart and the volume of blood in blood vessels. Blood pressure and heart rate are the main measurable indicators. Therefore, hemodynamic signs and symptoms of anemia are those related to the effect of anemia on the force of contraction of the heart, blood pressure and how fast the heart beats.
The presence and severity of certain signs and symptoms of anemia depend not only on the degree of anemia but also on how fast it develops. The reason is the limited amount of time the body has to compensate when significant hemodynamic effects are involved. Anemia due to acute blood loss is particularly problematic in this respect. The reason is the loss of intravascular volume is not only due to a reduction of red blood cells. It is also due to a loss of some of the fluid portion of blood.
The primary means by which the body compensates for a loss of intravascular volume is under the control of hormones. It involves increased absorption of fluid by the kidneys and decreased net excretion of water. A less common but additional means of increasing the volume within blood vessels is by an increase in the oncotic pressure of blood. Increased protein production by the liver is the mechanism by which it occurs.
Signs of Anemia
Signs of anemia are visible or measurable indicators of a decreased number of red blood cells ± a loss of some of the fluid portion of blood. The most common ones are the following:
- pallor (paleness)
- tachycardia (faster than normal heart rate)
- hypotension (below normal blood pressure)
- tachypnea (faster than normal breathing rate)
Pallor is a result of decreased oxygen carrying capacity. Oxygen bound to hemoglobin gives blood its red color. When the amount of hemoglobin is below normal blood is less red. Consequently, skin through which blood flows is less red or pale. For obvious reasons, paleness of the mucous membranes of the inside of the eyelids or the mouth is a more reliable sign of anemia than is skin pallor in dark-complexioned persons. The hemoglobin has to be more than moderately low for pallor to be observable though.
The heart beats faster than normal to compensate for the reduced amount of oxygen in the blood per heartbeat. Chemoreceptors mediate this response. In addition it beats faster if the blood pressure drops because of hemodynamic effects. Baroreceptors are involved in this response.
The increased rate of breathing can be due to either or both effects of the anemia on the normal physiology which governs the supply of oxygen to tissues. Faster breathing is the body’s attempt to compensate for decreased oxygen delivery to tissues. It doesn’t matter if it is because of a decreased amount of hemoglobin carrying oxygen or reduced flow of blood to the tissues. Peripheral chemoreceptors are involved in this response.
Symptoms of Anemia
The symptoms that people with anemia experience are due to the same two disturbances of bodily function as those that cause the physical signs. The main symptoms of anemia are the following:
- dyspnea (shortness of breath)
- fatigue (feeling tired)
- a general sense of muscle weakness
- syncope (fainting)
- palpitations (a sensation of forceful and/or irregular heartbeats)
Most of the above symptoms can be due to either or both disturbances. But lightheadedness, fainting and palpitations are due to the hemodynamic effects.
Worsening of any of the above or other symptoms or signs initially caused by an unrelated disease can also be a sign of anemia. A common example is an increase in the frequency or severity of chest pain in a person with blocked arteries in the heart as the red blood count drops. A worse-case scenario in this instance might be the occurrence of a heart attack. Whatever the case, the change in symptoms or signs of the comorbidity is due to decreased delivery of oxygen to the involved tissues.
Indirect Signs and Symptoms of Anemia
Other signs and symptoms can serve as clues of anemia even though they are not a result of the reduced amount of blood per se. They mainly pertain to hemolysis, iron deficiency and acute blood loss as causes. The more common ones are the following:
- jaundice (yellow discoloration of the skin or mucous membranes lining the inside of the eyelids and covering the cornea)
- splenomegaly (enlargement of the spleen)
- melena (black or tar colored bowel movements)
- spooning of the fingernails
Jaundice occurs as a result of an increased rate of bilirubin formation. Bilirubin is a breakdown product of hemoglobin following red blood cell death or destruction. The liver normally gets rid of it, but is not able to prevent its accumulation when its rate of production is significantly greater than normal. Since bilirubin is yellow in color the end result of its buildup in tissues is jaundice.
An enlarged spleen can be a cause of accelerated red blood cell destruction. It can also be a sign of extramedullary erythropoiesis as a response to chronic or severe anemia.
Spooning of the fingernails is inward curving of the top surface of the fingernails in the shape of a spoon as opposed to the usual upward curving of the surface from the sides. Most commonly, it is a sign of iron deficiency or other forms of microcytic anemia.
Signs and symptoms alone are not sufficient to make a diagnosis of anemia. Knowledge of them can heighten suspicion though. A heightened index of suspicion can lead to a prompt and timely diagnosis as well as a favorable outcome.