chemistry

Metabolic acidosis

Metabolic acidosis is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Metabolic acidosis rather than just read about it. In short: Metabolic acidosis is a serious electrolyte disorder characterized by an imbalance in the body's acid-base balance. Metabolic acidosis has three main root causes: increased acid production, loss of bicarbonate, and a reduced ability of the kidneys to excrete excess acids.

Key takeaways

Metabolic acidosis belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Metabolic acidosis to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Metabolic acidosis from memory before moving on to harder problems.

Reference excerpt

Metabolic acidosis is a serious electrolyte disorder characterized by an imbalance in the body's acid-base balance. Metabolic acidosis has three main root causes: increased acid production, loss of bicarbonate, and a reduced ability of the kidneys to excrete excess acids. Metabolic acidosis can lead to acidemia, which is defined as arterial blood pH that is lower than 7.35. Acidemia and acidosis are not mutually exclusive – pH and hydrogen ion concentrations also depend on the coexistence of other acid-base disorders; therefore, pH levels in people with metabolic acidosis can range from low to high. Acute metabolic acidosis, lasting from minutes to several days, often occurs during serious illnesses or hospitalizations, and is generally caused when the body produces an excess amount of organic acids (ketoacids in ketoacidosis, or lactic acid in lactic acidosis). A state of chronic metabolic acidosis, lasting several weeks to years, can be the result of impaired kidney function (chronic kidney disease) and/or bicarbonate wasting. The adverse effects of acute versus chronic metabolic acidosis also differ, with acute metabolic acidosis impacting the cardiovascular system in hospital settings, and chronic metabolic acidosis affecting muscles, bones, kidney and cardiovascular health.

Signs and symptoms

Acute metabolic acidosis Symptoms are not specific, and diagnosis can be difficult unless patients present with clear indications for blood gas sampling. Symptoms may include palpitations, headache, altered mental status such as severe anxiety due to hypoxia, decreased visual acuity, nausea, vomiting, abdominal pain, altered appetite and weight gain, muscle weakness, bone pain, and joint pain. People with acute metabolic acidosis may exhibit deep, rapid breathing called Kussmaul respirations which is classically associated with diabetic ketoacidosis. Rapid deep breaths increase the amount of carbon dioxide exhaled, thus lowering the serum carbon dioxide levels, resulting in some degree of compensation. Overcompensation via respiratory alkalosis to form an alkalemia does not occur. Extreme acidemia can also lead to neurological and cardiac complications:

Neurological: lethargy, stupor, coma, seizures Cardiac: Abnormal heart rhythms (e.g., ventricular tachycardia) and decreased response to epinephrine, both leading to low blood pressure Physical examination can occasionally reveal signs of the disease, but is often otherwise normal. Cranial nerve abnormalities are reported in ethylene glycol poisoning, and retinal edema can be a sign of methanol intoxication.

Chronic metabolic acidosis Chronic metabolic acidosis has non-specific clinical symptoms but can be readily diagnosed by testing serum bicarbonate levels in patients with chronic kidney disease (CKD) as part of a comprehensive metabolic panel. Patients with CKD Stages G3–G5 should be routinely screened for metabolic acidosis.

Diagnostic approach and causes Metabolic acidosis results in a reduced serum pH that is due to metabolic and not respiratory dysfunction. Typically the serum bicarbonate concentration will be <22 mEq/L, below the normal range of 22 to 29 mEq/L, the standard base will be more negative than -2 (base deficit) and the pCO2 will be reduced as a result of hyperventilation in an attempt to restore the pH closer to normal. Occasionally in a mixed acid-base disorder where metabolic acidosis is not the primary disorder present, the pH may be normal or high. In the absence of chronic respiratory alkalosis, metabolic acidosis can be clinically diagnosed by analysis of the calculated serum bicarbonate level.

Causes Generally, metabolic acidosis occurs when the body produces too much acid (e.g., lactic acidosis, see below section), there is a loss of bicarbonate from the blood, or when the kidneys are not removing enough acid from the body. Chronic metabolic acidosis is most often caused by a decreased capacity of the kidneys to excrete excess acids through renal ammoniagenesis. The typical Western diet generates 75–100 mEq of acid daily, and individuals with normal kidney function increase the production of ammonia to get rid of this dietary acid. As kidney function declines, the tubules lose the ability to excrete excess acid, and this results in buffering of acid using serum bicarbonate, as well as bone and muscle stores. As there are many causes of acute metabolic acidosis it is helpful to group them by the presence or absence of a normal anion gap.

Increased anion gap Causes of increased anion gap include:

Lactic acidosis Ketoacidosis (e.g., Diabetic, alcoholic, or starvation) Chronic kidney failure 5-oxoprolinemia due to long-term ingestion of high-doses of acetaminophen with glutathione depletion (often seen with sepsis, liver failure, kidney failure, or malnutrition) Intoxication: Salicylates, methanol, ethylene glycol Organic acids, paraldehyde, ethanol, formaldehyde Carbon monoxide, cyanide, ibuprofen, metformin Propylene glycol (metabolized to L and D-lactate and is often found in infusions for certain intravenous medications used in the intensive care unit) Massive rhabdomyolysis Isoniazid, iron, phenelzine, tranylcypromine, valproic acid, verapamil Topiramate Sulfates Normal anion gap Causes of normal anion gap include:

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Metabolic acidosis

Start with the simplest possible case. Write down what Metabolic acidosis claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Metabolic acidosis before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Metabolic acidosis ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Metabolic acidosis

In research: Metabolic acidosis appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Metabolic acidosis in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Metabolic acidosis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acid–base disturbances, so understanding it makes those chapters shorter.
In everyday life: Look for Metabolic acidosis outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Metabolic acidosis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Metabolic acidosis means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Metabolic acidosis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Metabolic acidosis in simple terms?

Why does Metabolic acidosis matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Metabolic acidosis?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Metabolic acidosis.