What causes arterial blood acidosis and how is it treated?

From the Guidelines

Arterial blood acidosis is primarily caused by respiratory or metabolic disturbances, and its treatment depends on the underlying cause and severity, with the goal of restoring blood pH and addressing the underlying condition to prevent morbidity and mortality. The causes of arterial blood acidosis can be categorized into two main types: respiratory acidosis and metabolic acidosis. Respiratory acidosis occurs when there is a retention of carbon dioxide in the blood, often due to conditions such as chronic obstructive pulmonary disease (COPD), severe pneumonia, or respiratory depression from drugs 1. On the other hand, metabolic acidosis results from excess acid production, such as in diabetic ketoacidosis or lactic acidosis, or bicarbonate loss, as seen in diarrhea or renal tubular acidosis 1.

Treatment Approaches

• For respiratory acidosis, improving ventilation is crucial, which may involve the use of bronchodilators like albuterol, antibiotics for infections, or mechanical ventilation in severe cases.
• Metabolic acidosis treatment focuses on addressing the underlying condition, such as administering insulin and fluids for diabetic ketoacidosis, discontinuing metformin for lactic acidosis, or providing fluid replacement for diarrhea.
• In cases of severe acidosis (pH < 7.2), sodium bicarbonate administration may be considered, typically 50-100 mEq IV over 30-60 minutes, although its use remains controversial 1.
• Hemodialysis may be necessary in cases involving renal failure or certain toxin ingestions.

Importance of Prompt Identification and Treatment

Prompt identification of the cause through arterial blood gas analysis, electrolyte panels, and clinical assessment is essential for effective treatment, as addressing only the acidosis without treating the underlying condition will result in continued acid-base disturbances 1. The use of noninvasive ventilation (NIV) may also be considered in certain cases, such as COPD exacerbations, to prevent acute respiratory acidosis and the need for invasive mechanical ventilation 1.

Recent Guidelines and Recommendations

Recent guidelines, such as those from the American Diabetes Association 1, emphasize the importance of individualized treatment based on a careful clinical and laboratory assessment, with the goal of restoring circulatory volume, resolving ketoacidosis, and correcting electrolyte imbalances and acidosis. The use of bicarbonate in the treatment of diabetic ketoacidosis is generally not recommended, as it has been shown to make no difference in the resolution of acidosis or time to discharge 1.

Key Considerations

• Addressing the underlying cause of arterial blood acidosis is critical for effective treatment and prevention of morbidity and mortality.
• Prompt identification through arterial blood gas analysis and clinical assessment is essential for guiding treatment.
• Individualized treatment plans should be based on the severity of the acidosis and the underlying condition, with consideration of the latest guidelines and recommendations.

From the FDA Drug Label

In cardiac arrest, a rapid intravenous dose of one to two 50 mL vials (44.6 to 100 mEq) may be given initially and continued at a rate of 50 mL (44. 6 to 50 mEq) every 5 to 10 minutes if necessary (as indicated by arterial pH and blood gas monitoring) to reverse the acidosis. Sodium bicarbonate in water dissociates to provide sodium (Na+) and bicarbonate (HCO3-) ions Bicarbonate (HCO3-) is a normal constituent of body fluids and the normal plasma level ranges from 24 to 31 mEq/liter Plasma concentration is regulated by the kidney through acidification of the urine when there is a deficit or by alkalinization of the urine when there is an excess.

Arterial blood becomes acidotic due to an excess of hydrogen ions. Treatment of arterial blood acidosis involves administering sodium bicarbonate intravenously to increase plasma bicarbonate, buffer excess hydrogen ions, and raise blood pH. The dosage of sodium bicarbonate is based on the severity of the acidosis and is typically administered in a stepwise fashion, with monitoring of blood gases, plasma osmolarity, and clinical condition. Key points to consider in treatment include:

• Dosage: 2 to 5 mEq/kg body weight over 4 to 8 hours
• Monitoring: blood gases, plasma osmolarity, arterial blood lactate, hemodynamics, and cardiac rhythm
• Goal: to achieve a total CO2 content of about 20 mEq/liter at the end of the first day of therapy, which is usually associated with a normal blood pH 2, 2

From the Research

Causes of Arterial Blood Acidosis

• Arterial blood acidosis, also known as metabolic acidosis, can occur due to various reasons, including the accumulation of endogenous acids that consume bicarbonate (high anion gap metabolic acidosis) or loss of bicarbonate from the gastrointestinal tract or the kidney (hyperchloremic or normal anion gap metabolic acidosis) 3.
• The cause of high anion gap metabolic acidosis includes lactic acidosis, ketoacidosis, renal failure, and intoxication with ethylene glycol, methanol, salicylate, and less commonly with pyroglutamic acid (5-oxoproline), propylene glycol, or djenkol bean (gjenkolism) 3.
• Diabetic ketoacidosis (DKA) is a common cause of arterial blood acidosis, characterized by elevated blood glucose levels, high urinary or blood ketoacids, and high anion gap metabolic acidosis 4.

Treatment of Arterial Blood Acidosis

• The treatment of acute metabolic acidosis is controversial, and the use of base to treat acute metabolic acidosis is not recommended due to a lack of definitive benefit and potential complications 5.
• The appropriate treatment of acute metabolic acidosis, in particular organic form of acidosis such as lactic acidosis, is cessation of acid production via improvement of tissue oxygenation 3.
• Bicarbonate has been shown to improve clinically relevant endpoints in the critically ill, even if higher pH values (>7.3) are targeted, but it can also induce serious side effects 6.
• The mainstays of treatment for diabetic ketoacidosis include restoration of circulating volume, insulin therapy, electrolyte replacement, and treatment of any underlying precipitating event 4.

Complications of Arterial Blood Acidosis

• Arterial blood acidosis can lead to various complications, including decreased cardiac output, arterial dilatation with hypotension, altered oxygen delivery, decreased ATP production, predisposition to arrhythmias, and impairment of the immune response 5.
• Diabetic ketoacidosis can cause respiratory compromise, including hypokalemia, hypomagnesemia, and hypophosphatemia, which can lead to respiratory muscle failure and increased morbidity and mortality 7.