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pH Levels in the Human Body – What Are They?

Would You Recognize the Signs of Acidosis in Your Patients?

The state of your patient’s blood is at the center of their health. As blood runs through veins, arteries and capillaries, it is dropping off oxygen to feed cells, and picking up carbon dioxide for expulsion. Every bodily function is ultimately at the control of this process, making it vital that the blood is able to complete its endless mission.

What is Blood pH?

One of the measurements for healthy blood is its pH level. The pH of any fluid is a measure of the concentration of the hydrogen ion. 7 is considered neutral, with any number below that considered to be acidic. Higher numbers reflect blood that is alkaline. For optimal function of blood, a nurse should look for a number that falls between 7.35 and 7.45.

What Can Affect Blood pH?

There are a number of functions and factors that attribute to the blood’s pH. What a patient has eaten or drank in the last 24 hours, whether they have been vomiting or had diarrhea can all cause a pH level to change dramatically. The pH level in humans is also affected by some infections, like one of the urinary tract, or even abnormalities of kidney, respiratory and endocrine systems. A nurse needs to take all of these factors into consideration when assessing a patient when attempting to determine whether their blood has turned acidic.

What is Acidosis?

Acidosis is a condition that develops when the blood contains too much acid. It is the job of the kidneys and lungs to regulate this, so conditions that affect their function could lead to acidosis. Many of the normal processes inside the human body produce acid, but problems with the lungs or kidneys will cause it to build up.

The largest amounts of acid build in the blood from carbonic acid, which is a by-product of carbon dioxide and water. The lungs help to keep this process in check by exhaling carbon dioxide out of the body.  Changes in the patient’s respiratory rate can affect their blood pH in just a matter of minutes.

Acids are also excreted by the kidneys in urine, which also have the job of regulating the concentration of bicarbonate in the blood. If there is a change in bicarbonate, the effect in the patient may take days to present.

Acidosis can occur if the patient begins to produce an excessive amount of acid, or if there is a problem in the lungs or kidneys that is causing a decrease in how much is being excreted. Other causes may be attributed to the patient consuming a substance that is metabolized into an acid, or if they increase the excretion of base.

Respiratory acidosis occurs when the decrease in pH can be attributed to a decrease in lung function. Not enough carbon dioxide is being excreted, causing acid to build up in the blood. This can be due to:

  • Respiratory conditions like asthma
  • A sudden chest injury
  • Obesity
  • Misuse of sedative drugs
  • Excessive alcohol use
  • Deformed chest structure
  • Muscle weakness in the chest
  • A problem with the central nervous system

When acidosis occurs as a result of kidney malfunction, it is referred to as metabolic acidosis. Either the kidneys are not eliminating enough acid from the body or they are getting rid of too much base. The three main types of this type of acidosis are:

  • Diabetic acidosis – where a diabetic patient is not controlling their disease and the body’s lack of insulin has allowed ketones to build up in the body to acidify the blood.
  • Hyperchloremic acidosis – the result of a loss of sodium bicarbonate, which helps to keep the pH in blood neutral. Excessive vomiting or diarrhea can both lead to this form of acidosis.
  • Lactic acidosis – too much lactic acid in the blood comes from heavy drinking, heart failure, cancer and even excessive exercise.

What are the Symptoms of Acidosis?

Knowing the risk factors and symptoms associated with acidosis will help you in making an accurate diagnosis. Patients suffering from acidosis due to respiratory issues will:

  • Be fatigued
  • Have short of breath
  • Exhibit signs of confused behavior
  • Tire easily
  • Have a headache

If the acidosis is due to a malfunction of the kidneys you will notice that your patient:

  • Is breathing shallowly and rapidly
  • Seems confused
  • Is fatigued
  • Has a headache
  • Appears jaundiced
  • Has a decrease in appetite
  • Has an increased heart rate
  • Presents with breath smells sweet or fruity

Diagnosing Acidosis

In order for you to confirm acidosis in your patient, the attending physician is going to have to order a special series of blood tests. An arterial blood gas will check the levels of oxygen and carbon dioxide in the blood and reveal the pH while a metabolic panel checks the kidney function if you suspect that this is the cause of the acidosis. Taken together, the results should not only tell you if the patient has acidosis, but what the probable cause is.

Undiagnosed acidosis can lead to kidney failure and death. As a nurse, be on the lookout for its symptoms, know which patients are at risk, and act quickly if you suspect acidosis. Your understanding of blood pH and acidosis can save a life.

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Scrubs Staff


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