What Is Metabolic Acidosis?

Overview

Acidosis is characterized by either an abundance of acids or a deficiency of bicarbonate (a base) within the tissues of your body. There are two primary forms of acidosis: metabolic acidosis and respiratory acidosis. Respiratory acidosis occurs when there is an excess of CO2 (carbon dioxide, an acid) in the tissues. Metabolic acidosis results from the buildup of acids in your body due to various factors. High anion gap metabolic acidosis is caused by diabetic ketoacidosis, lactic acidosis, chronic kidney disease, or certain toxins. Normal anion gap metabolic acidosis happens when the level of bicarbonate, which aids in the maintenance of the body's acid-base balance, falls.¹ The more severe the acidosis, the lower the blood pH (lower pH = higher acidity). 

An anion gap shows the difference in positive and negative electric charges in your blood electrolytes. Electrolytes are ions that aid in the regulation of many metabolic processes in your body, such as the transport of nutrients and the elimination of waste products from our cells. Sodium, calcium, potassium, chloride, and phosphate are examples of electrolytes.

There are various underlying causes of metabolic acidosis (see below). The symptoms of metabolic acidosis can range from mild to severe and may include rapid breathing, confusion, fatigue, and in severe cases, even shock. 

This article will cover the causes, clinical symptoms, diagnosis, management and treatment of metabolic acidosis. 

Causes of metabolic acidosis

A range of conditions can lead to metabolic acidosis, either by increasing acid levels in the body or reducing bicarbonate levels. The most common causes include:

Diabetic ketoacidosis (DKA)

DKA occurs in people with poorly-controlled diabetes when the body breaks down fats for energy, resulting in the formation of acidic ketones. The most common triggers include newly diagnosed diabetes, an infection, or a failure to comply with treatment.^1,2

Lactic acidosis

Excessive production or decreased clearance of lactic acid (also referred to as lactate) can occur as a result of circumstances such as severe infections, shock, certain medicines, or oxygen delivery abnormalities such as sepsis or hypoxia.^1,3

Renal failure

Kidneys play a crucial role in maintaining the body's acid-base balance by excreting acid and reabsorbing bicarbonate.^1,4 Any impairment of kidney function can lead to metabolic acidosis. Acidosis itself can worsen kidney function.

Severe diarrhoea

Prolonged diarrhoea can cause the loss of bicarbonate through the digestive system, resulting in metabolic acidosis.¹

Starvation/fasting

During extended periods without food intake, the body may break down fats and proteins, leading to ketoacid production.⁵

Toxic ingestion

Some toxins, like methanol or ethylene glycol, can be metabolised into acidic substances, causing metabolic acidosis.¹

Salicylate poisoning

Overdose of salicylates, such as aspirin, can lead to an increase in acid levels.⁶

Inherited metabolic disorders

Certain rare genetic conditions, such as congenital lactic acidosis, can lead to abnormal metabolism of acids and cause metabolic acidosis.¹³

Alcohol intoxication

Excessive alcohol consumption can lead to an accumulation of lactic acid and ketones, contributing to acidosis.⁷

Signs and symptoms of metabolic acidosis

Metabolic acidosis can present with a spectrum of signs and symptoms, the severity of which depends on both the underlying cause and the degree of the acid-base imbalance. Some common signs and symptoms of metabolic acidosis include:⁸

Rapid breathing (Hyperventilation)

The body may attempt to compensate for the increased acidity by increasing the breathing rate, helping eliminate excess carbon dioxide (a byproduct of acid metabolism) through the lungs.⁹

Confusion or disorientation

Metabolic acidosis can affect the central nervous system, leading to confusion, difficulty concentrating or even altered consciousness in severe cases.

Fatigue and weakness

The acidic environment can impair cellular function and energy production, leading to feelings of fatigue and weakness.

Nausea and vomiting

Acidosis can irritate the gastrointestinal tract, causing nausea and vomiting. 

Increased heart rate (Tachycardia)

The heart may beat faster as a compensatory response to the acidosis.

Dehydration

In some cases, metabolic acidosis is associated with fluid loss and dehydration, especially in conditions like diarrhoea or kidney disorders.

Electrolyte imbalances

Acidosis can disrupt the balance of electrolytes in the body, leading to disturbances in potassium, calcium, and other essential minerals.

Deep, rapid breathing (Kussmaul breathing): In severe metabolic acidosis, a specific type of hyperventilation called Kussmaul breathing may occur, characterised by deep and laboured breathing.

Cardiac arrhythmias

Severe acidosis can influence the heart's electrical activity, causing cardiac arrhythmias, which are irregular heartbeats.¹⁰

Shock (in severe cases)

In untreated or severe metabolic acidosis, the condition can progress to shock, a life-threatening state where vital organs are not receiving adequate blood flow and oxygen.¹⁰

Diagnosis

Diagnosing metabolic acidosis involves a combination of clinical assessment, laboratory tests, and the evaluation of the patient's medical history. The diagnostic process aims to identify the underlying cause of the acid-base imbalance and determine the severity of the condition. Here are the key steps involved in diagnosing metabolic acidosis:⁸

Medical history taking and physical examination

Everything begins with medical history taking and physical examination. The healthcare provider will begin by taking a detailed medical history, including any existing medical conditions, medications, recent illnesses, or exposures to toxins that could contribute to metabolic acidosis. A full physical examination is conducted to look for signs and symptoms of metabolic acidosis, such as rapid breathing, dehydration, altered mental status, and abnormal heart rate.

Blood gas analysis

Arterial blood gas (ABG) analysis is a crucial test to measure the pH, partial pressure of carbon dioxide (PaCO₂), and bicarbonate (HCO₃^-) levels in the blood. In metabolic acidosis, the pH will be low (lower than 7.35), and bicarbonate levels will be decreased.¹²

Electrolyte levels

Blood tests will be performed to assess the levels of electrolytes, such as potassium, sodium, and chloride, which can be affected by metabolic acidosis.

Lactate levels

Elevated levels of lactate in the blood may indicate lactic acidosis, a type of metabolic acidosis.

Anion gap calculation

The anion gap is calculated using the levels of sodium, chloride, and bicarbonate in the blood. A high anion gap (higher than 12 mEq/L) indicates an increase in unmeasured acids, often associated with metabolic acidosis. 

Urine analysis

A urine sample may be collected to assess the concentration of ketones or to look for other signs of underlying kidney disorders.

Imaging and additional tests

In some cases, imaging studies (e.g., CT scans) or additional tests may be necessary to identify the underlying cause of metabolic acidosis, especially in cases of suspected toxic ingestions or organ dysfunction.

Diagnosing the specific cause of metabolic acidosis is crucial for planning the treatment and management. Once the underlying cause is identified, appropriate measures can be taken to correct the acid-base imbalance and address the condition responsible for metabolic acidosis

Management and treatment for metabolic acidosis

The treatment and management of metabolic acidosis depend on the underlying cause and the severity of the condition. The primary goal is to correct the acid-base imbalance, address the root cause, and restore the body's acid-base equilibrium. Here are some general approaches to managing and treating metabolic acidosis:

Treat the underlying cause

Identifying and addressing the condition responsible for metabolic acidosis is crucial. For example, in diabetic ketoacidosis (DKA), insulin therapy and fluid replacement are the key to management.² In cases of lactic acidosis due to infection, treating the infection and providing supportive care is necessary.³

Intravenous fluids

Intravenous fluids, such as normal saline or lactated Ringer's solution, are often given to correct dehydration and improve blood flow to organs, helping to clear excess acids from the body.⁸

Electrolyte replacement

Acidosis can lead to imbalances in electrolytes like potassium and calcium. It should be corrected, and appropriate electrolyte replacement therapy be administered.

Sodium bicarbonate

In severe cases of metabolic acidosis, when the pH is significantly low, sodium bicarbonate may be administered intravenously to increase blood bicarbonate levels and neutralise excess acids temporarily. However, it is still under investigation.¹¹

Ventilation support

In some cases, patients with severe acidosis may require mechanical ventilation to help control their breathing and reduce carbon dioxide levels.

Dialysis (in renal failure)

If metabolic acidosis is due to kidney failure, dialysis may be necessary to help remove waste products and acids from the blood.⁴

Monitoring

Close monitoring of vital signs, electrolyte levels, and blood gases is essential to assess the patient's response to treatment and adjust therapy as needed.

Preventive measures

For patients at risk of recurring metabolic acidosis, preventive measures may include managing diabetes properly, avoiding excessive alcohol consumption, and following dietary recommendations to prevent prolonged fasting or starvation.²

FAQs

How can I prevent metabolic acidosis?

To prevent metabolic acidosis, manage underlying health conditions like diabetes and kidney disease, stay adequately hydrated, maintain a balanced diet, limit alcohol consumption, take medications as prescribed and attend regular check-ups. Seek prompt medical attention for any concerning symptoms or health changes.

How common is metabolic acidosis?

Metabolic acidosis is a relatively common medical condition, occurring in various clinical settings. Its prevalence varies depending on underlying causes such as diabetic ketoacidosis, lactic acidosis, kidney disease, severe infections, and certain inherited metabolic disorders. Early recognition and appropriate management are crucial to prevent complications associated with metabolic acidosis, making it an important consideration in healthcare settings.

Who is at risk of metabolic acidosis?

Individuals at risk of metabolic acidosis include: 

• People with uncontrolled diabetes (leading to diabetic ketoacidosis)
• Those with kidney disease or impairment
• Patients with severe infections or sepsis (predisposing to lactic acidosis)
• Those experiencing prolonged diarrhoea (causing bicarbonate loss)
• Individuals undergoing starvation or fasting (triggering acidic ketone production)
• Patients taking certain medications like metformin (with potential for lactic acidosis, especially with kidney issues)
• Individuals engaged in excessive alcohol consumption (resulting in alcoholic ketoacidosis)
• Those with inherited metabolic disorders
• Individuals exposed to toxic substances that can cause acidosis

Awareness of these risk factors is crucial for early detection, proper management, and prevention of metabolic acidosis-related complications.

What can I expect if I have metabolic acidosis?

If you have metabolic acidosis, you can expect symptoms such as rapid breathing, confusion or disorientation, fatigue, nausea, increased heart rate, electrolyte imbalances, and potential dehydration. The seriousness and particular symptoms can differ based on the root cause and the degree of the acid-base imbalance. 

When should I see a doctor?

You should see a doctor immediately if you experience severe symptoms like rapid breathing, confusion, extreme fatigue, severe nausea, or irregular heartbeat. Additionally, if you have diabetes, kidney disease, chronic lung conditions, or take medications that could lead to metabolic acidosis, and you notice any related symptoms, seek medical attention promptly. Furthermore, if you have had a recent severe infection or suspect exposure to toxins that can cause acidosis, do not delay seeking medical evaluation. Unexplained changes in health or any concerns should also prompt you to contact a healthcare professional to ensure timely diagnosis and appropriate management, as early intervention is crucial in preventing complications associated with metabolic acidosis.

Summary

Metabolic acidosis is a medical condition characterized by increased acidity in the blood, resulting from either the overproduction of acids, impaired acid elimination, or decreased levels of bicarbonate has a variety of underlying causes, including diabetic ketoacidosis (DKA) and lactic acidosis. Chronic kidney disease can lead to metabolic acidosis as the kidneys play a pivotal role in regulating acid excretion and bicarbonate reabsorption. 

Common symptoms include rapid and deep breathing as a compensatory mechanism to eliminate excess carbon dioxide and lower blood acidity, confusion, fatigue, nausea, increased heart rate (tachycardia), and electrolyte imbalances. In severe cases, Kussmaul breathing, characterised by deep, laboured breathing and cardiac arrhythmias, may occur. Left untreated, metabolic acidosis can progress to life-threatening conditions like shock and organ failure. 

Treatment focuses on correcting the acid-base imbalance and addressing the underlying condition. Intravenous fluids, electrolyte replacements, and sodium bicarbonate administration may be used to restore acid-base equilibrium and neutralize excess acids.