Alkalosis describes a condition in which there is an excess amount of base or alkali in the body fluids and tissues.
Alkalosis is a condition that is just the opposite of acidosis. It results due to an excess of alkali while acidosis occurs to increased acid level. The imbalance is classified as metabolic and respiratory, which emerges from different causes due to separate processes. The diagnosis is made through assessment of the history, physical exam, and important laboratory tests. Management includes treatment of the underlying disease and the physiological manifestations.
Metabolic alkalosis can occur secondary to diuretic use, loss of gastric acid (due to emesis, diarrhea, or nasogastric suction) , excessive antacid intake, and other causes.
Respiratory alkalosis develops as a consequence of tachypnea and/or hyperventilation, which may emerge secondary to hypoxia, metabolic acidosis, or stressed states such as with fever. This type of alkalosis arises from both pulmonary and extrapulmonary diseases .
This increase in serum bicarbonate develops in response to 1) loss of acid, 2) consumption of alkali, 3) intracellular shift of hydrogen ions or 4) contraction alkalosis.
Alveolar hyperventilation causes PaCO2 to drop below the bicarbonate concentration. In acute episodes or respiratory alkalosis, the pH is basic whereas chronic cases are characterized by a normal or close to normal pH due to metabolic compensation. This condition can affect all organs as it leads to electrolyte and mineral abnormalities.
The outcomes of metabolic and respiratory alkalosis are influenced by the causes and the contributing comorbidities.
Specifically, an arterial blood pH equivalent to 7.55 is associated with a 45% mortality rate, which dramatically increases to 80% when the pH is above 7.65  .
The manifestations of this condition are linked to the patient's history such as in cases with vomiting or diarrhea. Also, electrolyte deficiencies are associated with specific clinical features. For example, hypokalemia results in weakness, polyuria, myalgia, and serious sequelae such as cardiac arrhythmias while hypocalcemia produces remarkable findings that include altered mental status, tetany, Trousseau sign, Chvostek sign, and possibly seizures. Additionally, volume changes are characterized by signs of dehydration such as orthostatic hypotension, dry mucous membranes, decreased urine output, etc.
The symptoms reflect the etiology, duration of the alkalosis, and its degree. Hyperventilation leads to acute hypocapnia, which in turn decreases cerebral perfusion. Therefore, patients experience confusion, lightheadedness, loss of consciousness, and seizures. Also, patients with hyperventilation syndrome develop dyspnea, chest pain, paresthesia, and tetany .
Common features on the exam include tachypnea, tachycardia, and arrhythmias. Signs of hypocalcemia may also develop .
Patients with chronic respiratory alkalosis do not usually exhibit symptoms.
Clinical assessment consists of a detailed history including that of medication use, a full physical exam, and the appropriate studies.
The key tests include arterial blood gas (ABG) and a complete metabolic panel to evaluate electrolytes, renal function, etc. If the diagnosis is inconclusive, then the urinary chloride concentration should be measured.
On ABG, a pH greater than 7.45 indicates alkalemia. If the PaCO2 level is below 35 mm Hg, this reveals a respiratory origin. Also, acute episodes reveal a reduction in bicarbonate levels.
Further tests such as complete metabolic panel and screening for salicylate and theophylline should be performed.
Other diseases associated with hyperventilation should be excluded. Hence, a chest x-ray is crucial to evaluate underlying lung pathologies. Moreover, computerized tomography (CT) studies are obtained if radiography findings are unclear or if lung disease needs to be evaluated further.
The management of metabolic alkalosis consists of targeting the underlying etiology and rehydration with intravenous isotonic saline in chloride-responsive patients. Also, electrolyte replacement is paramount.
Additionally, vomiting should be treated with antiemetics and diuretics may be reduced in dose or discontinued if possible. Specific drugs such as potassium-sparing diuretics, carbonic anhydrase inhibitors, hydrochloric acid (HCl), and others may be of benefit . Also, hemodialysis can be performed in cases of severe alkalosis and volume overload in the context of pre-existing kidney disease .
The main approach to the management of this acid-base disorder aims at the treatment of the underlying condition. Also, patients should be encouraged to try breathing techniques to address the hyperventilation. Furthermore, mechanical ventilation settings may need to be adjusted.
Clinicians caring for hospitalized patients should be aware of how common these acid-base disorders are and take the proper measures to prevent them or manage them early.
What is alkalosis?
This is a condition in which the blood is alkaline due to the loss of acid or increased amount of bicarbonate. It can also be caused by breathing quickly or deeply. Alkalosis is a very common condition in hospitalized and ill patients.
What are the symptoms?
The symptoms depend on the underlying disease that led to the alkalosis. Patients may experience:
How is it diagnosed?
The doctor will ask questions about the patient's health, perform a physical exam, and order blood tests.
How is it treated?
The treatment depends on the cause of the alkalosis as underlying diseases should be managed. Also, patients will be treated with fluids, electrolytes, and the appropriate medications.