What is Lactic Acidosis?
Lactic acid is a substance that your body produces naturally, but it’s also often found in higher levels when someone is sick. When your body makes more lactic acid than it’s able to get rid of, this can cause serious health problems. Very high levels of lactic acid can affect your circulation and can even be fatal.
Because of this, doctors sometimes test the level of lactic acid in the blood. If lactic acid levels are high, this can serve as a warning sign of risk, and reducing those levels to normal can be a target for treatment. The higher the lactic acid level is, and the longer it takes to return to normal, the greater the risk of death.
Doctors also need to know that sometimes high lactic acid levels can occur when there’s enough blood flow and oxygen going to tissues. On the other hand, a condition known as lactic acidosis usually happens when there’s not enough blood flow and oxygen, irregularities in carbohydrate metabolism, or due to some medicines.
What Causes Lactic Acidosis?
Lactic acid is created in the body, usually about 20 mmol/kg/day, and it then goes into the bloodstream. This lactic acid is mainly broken down by the liver and kidney. Some parts of the body can use lactate, turning it into carbon dioxide (CO2) and water, but only the liver and kidney can use lactate to create glucose.
Lactic acid is normally made in excess by the skin, red cells, brain tissue, muscle, and the gastrointestinal (GI) tract, which includes your stomach and intestines. During vigorous exercise, your muscles produce the most lactic acid, which then returns to normal as long as the liver is functioning properly. Generally, high lactate levels can result from its increased production, decreased removal, or a mixture of both.
When the body breaks down glucose for energy through glycolysis, it produces another substance called pyruvate. Under conditions with enough oxygen, pyruvate enters a process called the citric acid cycle, which leads to the production of ATP, the chief energy currency of cells. However, when there’s not enough oxygen, pyruvate enters the lactic acid cycle or the Cori cycle.
In the lactic acid cycle, pyruvate changes into lactate and changes NADH into NAD+. NAD+ is then used in glycolysis to produce ATP. Excess lactate gets sent to the liver, where it undergoes a process to create glucose.
High and continuous lactic acidosis occurs when the body is making too much lactate that overpowers the liver’s ability to break it down. This could happen due to numerous factors such as severe convulsions together with impaired liver functions as seen in conditions like cirrhosis, low body temperature, severe infections, significant low blood volume, severe low blood pressure, or a combination of these factors.
Also, certain medications and toxins can cause lactic acidosis:
* Alcohols
* Acetaminophen
* Certain antiviral drugs
* Medications that stimulate the heart
* Metformin (used for diabetes)
* Cocaine
* Compounds containing cyanide
* Halothane (used for anesthesia)
* Propofol (a sedative)
* Isoniazid (used for tuberculosis)
* Salicylates
* Valproic acid (used for epilepsy)
* Sulfasalazine (used for inflammatory bowel disease)
Risk Factors and Frequency for Lactic Acidosis
Lactic acidosis is something that often concerns people who care for severely ill patients. However, there hasn’t been that much research on it. Most of the studies are either looking back at past cases or only include a small number of participants.
In 2011, a large-scale study was conducted by Jung and his team. They looked at this issue across several medical centers.
- In this study, severe lactic acidosis was found in 6% of the 2550 patients in the study.
- About 83% of these patients were treated with vasopressors, drugs that constrict blood vessels and increase blood pressure.
- The death rate among this group was 57%, and they had a pH of 7.09 (plus or minus 0.11) and high lactic acid levels.
- The study found a link between the severity of the lactic acidosis and how long it took for it to get better. Patients with higher levels of lactic acid or who took longer to recover had a higher death rate.
Often, patients with shock also have severe lactic acidosis (a pH less than 7.2), and about half of them don’t survive. If the patient’s pH level falls below 7.0, they don’t survive. However, in patients with lactic acidosis from non-shock situations, like from taking the diabetes drug metformin, even if their pH values hit 7.0, their death rate was only 25%.
Signs and Symptoms of Lactic Acidosis
Lactic acidosis can happen quickly or take several days to set in. A thorough medical history review should be done to help identify any potential causes such as shock conditions, intake of certain drugs or toxins that might be contributing to the lactic acidosis. If the patient cannot provide this information, the patient’s family should be consulted. The objective is to understand any factors that might have caused the lactic acidosis.
It’s important to note that lactic acidosis can develop after exercise or from certain medications. Also, kids with a deficiency in a key enzyme known as pyruvate dehydrogenase may experience lactic acidosis after an upper respiratory tract infection.
Lactic acidosis does not exhibit specific distinctive features. Rather, its signs and symptoms will largely depend on its underlying cause. Patients with lactic acidosis are typically in a critical condition, and may exhibit symptoms of shock such as hypovolemic (caused by extreme blood or fluid loss), septic (caused by infection), or cardiogenic (relating to the heart).
Upon examination, signs of insufficient tissue blood supply are often noted. Symptoms such as severely low blood pressure, mental confusion, decreased urine output, rapid breathing, and fever higher than 38.5 C often occur when the lactic acidosis is caused by septic shock. In an attempt to compensate for the acidosis, the body may exhibit a deep breathing pattern known as Kussmaul respirations.
Testing for Lactic Acidosis
If a patient is thought to have metabolic acidosis, which is a condition where there is too much acid in the body, tests on their blood and electrolytes in their body will be carried out. Metabolic acidosis can sometimes be identified through a measure called the ‘anion gap’, which can be calculated through a particular blood test. If this anion gap is higher than 12 mEq/L, it could suggest that the person has metabolic acidosis.
The anion gap is a way of checking the balance between positively and negatively charged ions, or particles, in the blood. It’s usually calculated using the following formula: Sodium – (Chloride + Bicarbonate).
In a healthy person, the anion gap is typically between 4 mEq/L and 12 mEq/L, due to the constant presence of unmeasured ions, such as phosphate and a protein called albumin.
Lactate is one type of ion that can contribute to a high anion gap and lead to metabolic acidosis if it’s present in high amounts. However, even when lactate is not very high, it can still cause metabolic acidosis, but with a normal anion gap. Furthermore, when albumin levels are low, a condition often observed in severe illnesses, it can affect the accuracy of anion gap measurements. In some cases, the anion gap might seem normal even if metabolic acidosis is otherwise present due to this low albumin level.
Treatment Options for Lactic Acidosis
Understanding the source of lactic acidosis is crucial to its treatment. Lactic acidosis is an acidic condition in your bloodstream caused by excessive levels of lactate, a product of glucose breakdown. For instance, if the condition due to abdominal blood flow reductions known as mesenteric ischemia, surgery might be necessary. Likewise, if seizures are causing lactic acidosis, treating the seizures becomes essential. Consequently, the patient’s further care would need to be specialized based on their individual circumstances.
With this in mind, let’s look at a particular condition that can trigger lactic acidosis — septic shock. A septic shock happens when an infection has spread throughout the body leading to low blood pressure which isn’t improving with fluid replacement, and it’s characterized by high lactate levels. According to the Surviving Sepsis Campaign (SSC), an initiative meant to reduce mortality and morbidity related to sepsis, addressing the infection in septic shock is an important aspect of treatment.
It’s essential to administer broad-spectrum antibiotics, which can fight a wide variety of bacteria, within an hour after recognizing sepsis. But, this should happen after drawing blood to determine the bacteria causing the infection. Besides, the quickest possible removal of any possible infection source in the body is generally recommended.
Additionally, for patients experiencing septic shock, it’s advised to provide a high volume of fluids within three hours of initial evaluation. The amount of additional fluid given should be based on regular check-ins with the patient. Goals for any treatment plan should include maintaining a mean arterial pressure (MAP) – an average blood pressure in an individual during a single cardiac cycle – of about 65 millimeters of mercury. For patients with severe sepsis that doesn’t improve despite fluid administration, a group of medications called vasopressors, which constrict the blood vessels, raising blood pressure, may become necessary. Norepinephrine is often the first-choice vasopressor.
There is debate over using alkaline substances in treating septic shock, and it might not necessarily help with improving blood flow. Similarly, Tromethamine (a substance that helps to prevent and treat too much acidity in the blood), while a good buffering agent, has no proven beneficial impact on the prognosis of these patients. Sometimes, hemodialysis, a procedure to remove waste and excess fluid from the blood, is employed to manage severe lactic acidosis, especially when the patient has kidney failure. In most cases, the root cause of the issue is poor blood circulation, which needs to be addressed first.
Lastly, for those patients with sepsis-induced lung injury (ARDS), a particular breathing support strategy that involves low volume and low pressure airflow should be used. This ensures the amount of air in the ventilator is no more than 6 milliliters per kilogram of the patient’s ideal body weight, and the pressure applied to get air into the lungs is not more than the recommended measure.
What else can Lactic Acidosis be?
These are some of the conditions that might be confused with each other due to similarities in their symptoms:
- Alcoholic ketoacidosis
- Anaemia
- Bacterial sepsis
- Distributive shock
- Hemorrhagic shock
- Inborn metabolic defects
- Metabolic acidosis
- Pyruvate dehydrogenase deficiency
- Respiratory failure
- Septic shock
It’s crucial for doctors to correctly identify the specific condition to provide the most effective treatment.
What to expect with Lactic Acidosis
The outlook for patients varies and largely depends on what’s causing their lactate levels to rise and how high these levels are. Lactate is a substance produced by the body, and its levels can rise due to certain health conditions. Very high lactate levels during a state of shock, when your organs aren’t getting enough blood flow, can be linked to a higher risk of death. Therefore, early diagnosis remains crucial for a better outcome.
