Physiologic Variables Affecting Blood


Posted on 13th June 2011 by admin in Uncategorized

There are many variables that can affect blood.  A phlebotomist should be aware of theses variables when collecting and examining blood samples.

Age.  A patient’s age can affect some blood components.  Newborns typically have higer values of red and white blood cells compared to adults.  Because kidney function tends to decrease with age, higher levels of creatinine may be evident in older patients.

Altitude.  Decreased oxygen levels can cause the body to produce more red blood cells to meet the body’s oxygen needs.  The higher the altitude the greater the increase of red blood cells.

Dehydration.  If a patient has lost a lot of fluids due to vomiting and diarrhea, dehydration will result.  Dehydrations can affect the blood causing the blood to become more concentrated.  If a patient is dehydrated it is difficult to obtain a blood sample.

Diet.  What you eat can affect your blood composition.  If you eat a lot of high sugar foods, like carbohydratees or sweets, your blood glucose levels will be high.  It can take several hours before the blood glucose levels return to normal.  Fatty foods can increase the fat content in blood causing the blood plasma to appear cloudy.  This condition of cloudy blood is called lepemia.  It can last for up to 12 hours.

Diurnal/Circadian Variations.  Diurnal variations occur daily and circadian variations occur in a 24 hour cycle.  These variations can affect blood composition.  Diurnal variations are affected by posture, activity, eating, daylight, darkness and sleep patterns.  Blood components that show diurnal variations include bilirubin, hemoglobin, insulin, iron, potassium, testosterone, and red blood cells.

Drug Therapy.  Some drugs can alter the concentrations of certain blood analytes.  this can cause an unwanted side effect. Physicians will monitor patients who are prescribed drugs that can affect specific blood analytes.  Chemotherapy can decrease white blood cells and platelets.  Many drugs are toxic to the liver.  Drugs with steroids or diurtetics can cause pancreatitis and thiazide diuretics can increase calcium and glucose levels and decrease sodium and potassium levels.

Drugs are known to interfere with test results causing false increases or decreases in results or inaccurate results .

Exercise.  The intensity and duration of exercise can affect a patient’s physical condition.  Exercise can directly affect the arterial pH and PCO2 levels.  Glucose, creatinine, insulin, lactic acid, and protein can increase in blood tests due to muscular activity.  Skeletal muscle enzymes increasefor 24 hours or more by exercise and vigorous exercise before blood collection can increase cholesterol levels by 6%.

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