Introduction
Some complex acid-base and electrolyte disorders are common in modern intensive care units. Injured and critically ill patients have conditions that affect the acid-base equilibrium. Most acid-base disturbances are mild but may lead to morbidity and mortality. Therefore, a complete understanding of the etiology and pathophysiology of these diseases is essential for proper management.
What Are Acids and Bases?
An acid is a hydrogen-containing substance capable of donating a hydrogen ion (proton) to another. Acidic substances are identified by their sour taste, and the potential of hydrogen (pH) values is less than seven.
A base is a molecule or ion that accepts a hydrogen ion from an acid. Bases are characterized by their bitter taste and slippery texture. The potential of hydrogen (pH) values is always greater than seven.
What Is Acid-Base Homeostasis?
The balance between the acids and bases and pH regulation is vital for normal physiological functions and cellular metabolism. Kidneys and lungs play an essential role in the regulation of acid-base balance. The average acid-base balance is the arterial pH between 7.36 and 7.44 and an intracellular pH of about 7.2. When the level of acid increases in the blood, it is called acidosis, whereas an increased level of alkalies (bases) is called alkalosis.
What Are Acid-Base Disturbances in Critical Care?
The acid-base disorders are the markers for the underlying pathology. Interpreting arterial blood gases is vital for recognizing acid-base disturbances. The methods for interpretation are the excess base method, Stewart (physiochemical method), and physiological method. The four-cardinal acid-base disorders during critical care are.
-
Metabolic alkalosis.
-
Respiratory acidosis.
-
Respiratory alkalosis.
Metabolic Acidosis:
Metabolic acidosis is a disorder in which acid imbalance in the body occurs due to excessive acid production by the body or the kidney’s inability to remove them. The types of metabolic acidosis are as follows:
1. Anion gap acidosis.
2. Non-anion gap acidosis - It is subdivided into three types. They are
-
Renal acidosis.
-
Gastrointestinal acidosis.
-
Iatrogenic acidosis.
Causes of Metabolic Acidosis:
The following factors cause the different types of metabolic acidosis during critical care.
-
Renal failures or kidney diseases, such as uremia, distal renal tubular acidosis, or proximal renal tubular acidosis).
-
Diabetic ketoacidosis.
-
Alcoholics.
-
Starvation.
-
Severe dehydration.
-
Lactic acidosis.
-
Sepsis.
-
Diarrhea.
-
Toxins include methanol, ethylene glycol, salicylates, and paraldehyde 5-oxo proline (pyroglutamic acid).
-
Parenteral nutrition.
-
Anion exchange resins.
-
Metabolic errors.
Symptoms of Metabolic Acidosis:
The most common symptoms of metabolic acidosis include the following.
-
Rapid breathing.
-
Fatigue.
-
Confusion.
How to Diagnose Metabolic Acidosis?
The diagnostic tests to detect metabolic acidosis include.
-
Arterial or venous blood gas.
-
Blood tests that measure sodium, potassium, ketones, and other chemicals.
-
Lactic acid test.
-
Urine ketones and pH.
How to Treat Metabolic Acidosis?
The treatment of metabolic acidosis is aimed at treating the cause of acidosis. Sodium bicarbonate (a form of carbon dioxide) is prescribed to balance the acid as it is an alkali. In addition, a diet rich in fruits and vegetables is advised because they produce alkalis.
Metabolic Alkalosis:
Metabolic alkalosis is a condition that occurs when body fluids and blood contain an excess quantity of bases or alkalis. In critically ill patients, excess amounts of bicarbonate occur in the body due to repeated vomiting and heart, kidney, and liver diseases.
Causes of Metabolic Alkalosis:
The following drugs cause metabolic acidosis in the intensive care unit.
-
Antacids (contain sodium bicarbonate).
-
Steroids.
-
Laxatives.
-
Diuretics or water pills.
Other causes of metabolic alkalosis are
-
Recurrent vomiting.
-
Cystic fibrosis.
-
Dehydration.
-
Electrolyte imbalance.
-
Hypochloremia (reduced levels of chloride in the blood).
-
Hyperaldosteronism (increased levels of adrenal hormone).
Symptoms of Metabolic Alkalosis:
The symptoms of metabolic alkalosis include the following.
-
Muscle cramps and spasms.
-
Fatigue.
-
Confusion.
-
Arrhythmia (abnormal heart rhythm).
-
Seizures and coma.
How to Diagnose and Treat Metabolic Alkalosis?
Physical tests, blood tests, electrocardiograms, and urinalysis diagnose metabolic alkalosis. The treatment of metabolic alkalosis includes the following.
-
Saline, chlorine, or hydrochloric acid infusion.
-
Potassium and magnesium replacement.
-
Discontinuing the medications that cause alkalosis.
Respiratory Acidosis:
Respiratory acidosis occurs due to the lung’s inability to remove all the carbon dioxide resulting in increased acids in the body fluids.
Causes of Respiratory Acidosis:
The following diseases and factors cause respiratory acidosis.
-
Lung disorders such as COPD (chronic obstructive pulmonary disease), pulmonary fibrosis, and asthma.
-
Medicines used in the intensive care unit suppress breathing. For example, opioids and benzodiazepines when used in combination with alcohol.
-
Obstructive sleep apnea.
Symptoms of Respiratory Acidosis:
The symptoms of respiratory acidosis include shortness of breath, lethargy, confusion, anxiety, sleepiness, warm and flushed skin, and sweating.
How to Diagnose and Treat Respiratory Acidosis?
Respiratory acidosis is diagnosed by arterial blood gas (measures oxygen and carbon dioxide in the blood), chest x-ray, and pulmonary function test.
Respiratory acidosis is treated with drugs like bronchodilators and corticosteroids, oxygen supplementation, and noninvasive positive pressure ventilation. In severe cases, the patient is put on a ventilator (breathing machine).
Respiratory Alkalosis:
Respiratory alkalosis occurs when the body does not have enough carbon dioxide. It is usually caused by breathing very profoundly or rapidly. Patients under mechanical ventilation in the ICU are at high risk of developing respiratory alkalosis.
Causes of Respiratory Alkalosis:
The following factors cause respiratory alkalosis in the intensive care unit.
-
Lung diseases such as asthma and embolism cause shortness of breath.
-
Neurological disorders such as stroke.
-
Pain and anxiety.
-
Liver diseases.
-
Overuse of drugs such as salicylates or progesterone.
Symptoms of Respiratory Alkalosis:
The common symptoms of respiratory alkalosis include breathlessness, dizziness, numbness, chest discomfort, irritability, nausea, syncope, tremors, and confusion.
How to Prevent and Treat Respiratory Alkalosis?
Therapy, relaxation techniques, supplemental oxygen, and medications such as opioid pain relievers and anti-anxiety drugs prevent and treat hyperventilation. If the respiratory alkalosis is caused by to ventilator setting, the physician modifies the environment to make the patient breathe comfortably.
Conclusion
Acid-base disorders in critically ill patients are common and can cause mortality if left untreated. However, traditional approaches measuring acid-base disorder are uncertain. Many limitations exist in establishing the relationship between acid-base disturbances and clinical outcomes in critical care.
