Metabolic acidosis

Metabolic acidosis is a process where the body fails to properly regulate the acidity of its fluids, particularly blood. There are several different types of health conditions that can cause metabolic acidosis. The seriousness and danger of metabolic acidosis depends upon its causes; it should never be left untreated. 

Definition & Facts

Acidity is rated on the pH scale, where lower numbers are more acidic and a 7 is neutral. Normally, body fluids are around 7.4 on the pH scale, regulated by the kidneys' ability to filter hydrogen from the blood and produce bicarbonate, a basic compound that neutralizes acids. A pH of 7.1 or less is potentially life-threatening.

One form of acidosis, respiratory acidosis, is caused by the lungs becoming unable to remove enough carbon dioxide from the body. Metabolic acidosis is caused by problems in the digestive system and urinary system, where the body breaks down or metabolizes compounds for use in the body. 

Symptoms & Complaints

Typical symptoms include fast, deep breathing (hyperpnea) due to a lack of oxygen in the body; tiredness and confusion; muscle weakness; chest pain, joint pain, or abdominal pain; nausea and vomiting; an accelerated and/or uneven heart rate (tachycardia; cardiac arrhythmia); and headaches.

If the liver is involved, jaundice (a yellowing of the skin and eyes) can also be a symptom. If the acidosis is the result of diabetes (diabetic ketoacidosis), the patient will often have sweet, fruity-smelling breath.

In severe cases, or cases that are allowed to go untreated, metabolic acidosis can cause seizures, shock, organ damage, coma, and possibly death. Low-level chronic acidosis, which can be a result of chronic kidney disease, can also leach calcium out of the bones and produce osteoporosis.

Causes

There are several ways the body can go into metabolic acidosis: either the body is producing too much acid, there is not enough base in the body to neutralize the acid, or the kidneys are failing to remove acid from the body. Specifically, the following conditions are the main causes of metabolic acidosis: 

• Diabetic ketoacidosis, or DKA, occurs in patients who do not have enough insulin in their bodies. Acidic compounds called ketones build up in the blood. This is mostly seen in diabetics who are not properly controlling their disease. Eating a high fat / low carbohydrate diet can also produce an overabundance of ketones in the blood.
• Lactic acidosis occurs when the body overproduces lactic acid. Normally, the muscles produce lactic acid when they exercise without sufficient oxygen available; this is part of why the muscles become sore when they're worked too hard. Over-exercise can send the body into lactic acidosis, or a more severe condition called rhabdomyolysis. Lactic acid can also build up excessively under conditions that prevent the body from efficiently transporting oxygen, including alcohol abuse, heart failure, liver failure, low blood sugar, infections, or cancer.
• Hyperchloremic acidosis occurs when the body loses too much bicarbonate and can no longer neutralize acids. This can occur as a result of severe vomiting, diarrhea, or dehydration.

Metabolic acidosis can also be caused by overconsumption of aspirin or other salicylate drugs, toxins such as methyl salicylate and ethylene glycol (antifreeze) that attack the kidneys, and diseases that interfere with kidney function.

Diagnosis & Tests

It is important for the physician to be able to determine the cause of the acidosis before treating. First, it's necessary to discover whether the acidosis is the result of respiratory or metabolic problems. If it's a metabolic condition, then the physician needs to determine where in the metabolism the problem is arising.

If acidosis is suspected, the usual first step is an arterial blood gas test, which tests the acidity of the blood and how much dissolved oxygen or carbon dioxide it is carrying. If the blood gas test comes back positive for acidosis, another blood test, the metabolic panel, will help reveal how the metabolic system is working and the levels of various chemicals in the body. This can help rule out respiratory acidosis.

If the blood tests seem to indicate metabolic acidosis, the doctor may request clinical urine tests to see how the kidneys are functioning. In the case of diabetic ketoacidosis, it's possible for a patient to test their own blood or urine for ketones at home using a blood sugar meter or test strips. 

Treatment & Therapy

Treatment of metabolic acidosis should always include treating the underlying condition that gave rise to the acidosis in the first place. The body's pH can be raised by giving a basic compound, such as sodium bicarbonate, potassium citrate, or sodium citrate, depending on the levels of potassium and sodium in the body.

The base supplement can be given orally or via an IV. This can be accompanied by insulin in the case of diabetic ketoacidosis. IV fluids can help rehydrate the body in cases where the problem is caused by a lack of oxygen.

Dialysis or detoxification may be necessary in cases where the problem is poisoning or acid buildup due to kidney failure. If the acidosis is the result of an infection, antibiotics may be prescribed. 

Prevention & Prophylaxis

Drinking alcohol and using aspirin in moderation, and avoiding or quitting smoking to keep the body properly oxygenated can all help reduce the risk of this condition. If one is diabetic, it is important to control one's disease with regular blood tests and insulin.