| Respiratory alkalosis treatment is done at affordable | | | | - Interstitial lung disease |
| cost in India | | | | - Asthma |
| Introduction | | | | - Emphysema |
| Background | | | | - Chronic bronchitis |
| Respiratory alkalosis is a clinical disturbance due to | | | | Miscellaneous |
| alveolar hyperventilation. Alveolar hyperventilation leads | | | | - Sepsis |
| to a decreased partial pressure of arterial carbon | | | | - Hepatic failure |
| dioxide (PaCO2), or partial pressure of carbon dioxide | | | | - Mechanical ventilation |
| (PCO2). In turn, the decrease in PCO2 increases the | | | | - Heat exhaustion |
| ratio of bicarbonate concentration to PCO2 and | | | | - Recovery phase of metabolic acidosis |
| increases the pH level. The decrease in PCO2 | | | | - Congestive heart failure |
| (hypocapnia) develops when a strong respiratory | | | | Differential Diagnoses |
| stimulus causes the lungs to remove more carbon | | | | Asthma |
| dioxide than is produced metabolically in the tissues. | | | | Pneumonia, Bacterial |
| Respiratory alkalosis can be acute or chronic. In acute | | | | Atrial Fibrillation |
| respiratory alkalosis, the PCO2 level is below the lower | | | | Pneumonia, Community-Acquired |
| limit of normal and the serum pH is alkalemic. In chronic | | | | Atrial Flutter |
| respiratory alkalosis, the PCO2 level is below the lower | | | | Pneumonia, Viral |
| limit of normal, but the pH level is normal or near | | | | Atrial Tachycardia |
| normal. | | | | Pneumothorax |
| Respiratory alkalosis is the most common acid-base | | | | Head Trauma |
| abnormality observed in patients who are critically ill. It is | | | | Pregnancy Diagnosis |
| associated with numerous illnesses and is a common | | | | Heatstroke |
| finding in patients on mechanical ventilation. Many | | | | Pulmonary Edema, Cardiogenic |
| cardiac and pulmonary disorders can manifest | | | | Hyperthyroidism |
| respiratory alkalosis as an early or intermediate finding. | | | | Pulmonary Edema, High-Altitude |
| When respiratory alkalosis is present, the cause may | | | | Meningitis |
| be minor; however, more serious disease processes | | | | Pulmonary Embolism |
| should also be considered in the differential diagnosis. | | | | Metabolic Acidosis |
| Pathophysiology | | | | Pulmonary Fibrosis, Idiopathic |
| Breathing is the body’s way of providing adequate | | | | Metabolic Alkalosis |
| amounts of oxygen for metabolism and for removing | | | | Sepsis, Bacterial |
| carbon dioxide produced by the tissues. By sensing the | | | | Myocardial Infarction |
| body’s partial pressure of oxygen (PO2) and | | | | Toxicity, Salicylate |
| PCO2, the respiratory system adjusts pulmonary | | | | Panic Disorder |
| ventilation so that oxygen uptake and carbon dioxide | | | | Toxicity, Theophylline |
| elimination at the lungs is equal to that used and | | | | Other Problems to Be Considered |
| produced by the tissues. PO2 is not as closely | | | | - Hyperthyroidism: Hyperthyroidism increases ventilation |
| regulated because adequate hemoglobin saturation | | | | chemoreflexes, thereby causing hyperventilation. |
| can be achieved over a wide range of PO2 levels. | | | | These return to normal with treatment of the |
| Oxygen is dependent on pressure gradients whereas, | | | | hyperthyroidism. |
| carbon dioxide diffuses much easier through an | | | | - Pregnancy: Progesterone levels are increased during |
| aqueous environment, making carbon dioxide regulation | | | | pregnancy. Progesterone causes stimulation of the |
| more complex. The PCO2 must be maintained at a | | | | respiratory center, which can lead to respiratory |
| level that ensures hydrogen ion concentrations remain | | | | alkalosis. |
| in the narrow limits required for optimal protein function. | | | | - Congestive heart failure: Patients with congestive |
| Metabolism generates a large quantity of volatile acid | | | | heart failure (and other low cardiac-output states) |
| (carbon dioxide) and nonvolatile acid. The metabolism | | | | hyperventilate at rest, during exercise, and during sleep. |
| of fats and carbohydrates leads to the formation of a | | | | Owing to pulmonary congestion, pulmonary vascular |
| large amount of carbon dioxide.1 The carbon dioxide | | | | and interstitial receptors are stimulated. Additionally, the |
| combines with water to form carbonic acid. The lungs | | | | low cardiac-output state and hypotension stimulate |
| excrete the volatile fraction through ventilation, and acid | | | | breathing via the arterial baroreceptors. |
| accumulation does not occur. Significant alterations | | | | - Chronic/severe liver disease: Several mechanisms |
| in ventilation can affect the elimination of carbon | | | | have been hypothesized to explain the hyperventilation |
| dioxide and lead to a respiratory acid-base disorder. | | | | associated with liver disease. Increased levels of |
| PCO2 is normally maintained in the range of 37-43 mm | | | | progesterone, ammonia, vasoactive intestinal peptide, |
| Hg. Chemoreceptors in the brain (central | | | | and glutamine can stimulate respiration. Patients with |
| chemoreceptors) and in the carotid bodies (peripheral | | | | severe disease or portal hypertension may have small |
| chemoreceptors) sense hydrogen concentrations and | | | | pulmonary arteriovenous anastomoses in the lungs or |
| influence ventilation to adjust the PCO2, PO2, and pH. | | | | portal-pulmonary shunts, which result in hypoxemia. |
| Under this feedback regulator is how the PCO2 is | | | | This stimulates the peripheral chemoreceptors and |
| maintained within its narrow normal range. When these | | | | leads to hyperventilation. |
| receptors sense an increase in hydrogen ions, | | | | - Salicylate overdose: Initially, a respiratory alkalosis |
| breathing is increased to “blow off” carbon | | | | occurs, which is followed by a metabolic acidosis that |
| dioxide and subsequently reduce the amount of | | | | induces secondary hyperventilation. |
| hydrogen ions. Various disease processes may cause | | | | - Fever and sepsis: Fever and sepsis may manifest as |
| stimulation of ventilation with subsequent | | | | hyperventilation, even before hypotension develops. |
| hyperventilation. If hyperventilation is persistent, it leads | | | | The exact mechanism is not known but is thought to |
| to hypocapnia. | | | | be due to carotid body or hypothalamic stimulation by |
| Hyperventilation refers to an increase in the rate of | | | | the increased temperature. |
| alveolar ventilation that is disproportionate to the rate | | | | - Pain: Hyperventilation may be due to stimulation of |
| of metabolic carbon dioxide production, leading to an | | | | the peripheral and central chemoreceptors, as well as |
| arterial PCO2 below the normal range. Two words | | | | the behavioral control system. |
| often used synonymously with hyperventilation are | | | | - Hyperventilation syndrome: This is also known as |
| tachypnea, an increase in respiratory frequency, and | | | | psychogenic hyperventilation, and it is due to stress |
| hyperpnea, an increase in the minute volume of | | | | and anxiety, both of which act on the behavioral |
| ventilation. These should not be used to describe | | | | respiratory control system. The hyperventilation |
| hyperventilation because they are distinct entities and | | | | ceases during sleep, when the behavioral control |
| neither results from nor means a change in PaCO2. | | | | system is inactive and only the metabolic system is |
| Hyperventilation is often associated with dyspnea, but | | | | controlling breathing. The diagnosis of hyperventilation |
| not all patients who are hyperventilating complain of | | | | syndrome should be a diagnosis of exclusion. Rule out |
| shortness of breath. Conversely, patients with dyspnea | | | | all organic medical conditions, including pulmonary |
| need not be hyperventilating. | | | | embolism, cardiac ischemia, and hyperthyroidism, |
| Acute hypocapnia causes a reduction of serum levels | | | | before establishing a diagnosis of hyperventilation |
| of potassium and phosphate secondary to increased | | | | syndrome. |
| intracellular shifts of these ions. A reduction in free | | | | Workup |
| serum calcium also occurs. Calcium reduction is | | | | Laboratory Studies |
| secondary to increased binding of calcium to serum | | | | - Arterial blood gas determinations |
| albumin. Many of the symptoms present in persons | | | | - Alkalemia is documented by the presence of an |
| with respiratory alkalosis are related to the | | | | increased pH level (>7.44) on arterial blood gas |
| hypocalcemia. Hyponatremia and hypochloremia may | | | | determinations. |
| also be present. | | | | - The presence of a decreased PCO2 level (<36 |
| Acute hyperventilation with hypocapnia causes a small, | | | | mm Hg) indicates a respiratory etiology of the |
| early reduction in serum bicarbonate levels resulting | | | | alkalemia. |
| from cellular uptake of bicarbonate. Acutely, plasma pH | | | | Serum chemistries |
| and bicarbonate concentration vary proportionately | | | | - Acute respiratory alkalosis causes small changes in |
| with the PCO2 along a range of 15-40 mm Hg. The | | | | electrolyte balances. Minor intracellular shifts of sodium, |
| relationship of PCO2 to arterial hydrogen and | | | | potassium, and phosphate levels occur. A minor |
| bicarbonate is 0.7 mmol/L per mm Hg and 0.2 mmol/L | | | | reduction in free calcium occurs due to an increased |
| per mm Hg, respectively. After 2-6 hours, respiratory | | | | protein-bound fraction. |
| alkalosis is renally compensated by a decrease in | | | | - Compensation for respiratory alkalosis is by |
| bicarbonate reabsorption. The kidneys respond more | | | | increased renal excretion of bicarbonate. In acute |
| to the decreased PCO2 rather than the increased pH. | | | | respiratory acidosis, the bicarbonate concentration level |
| Kidney compensation may take several days and | | | | decreases by 2 mEq/L for each decrease of 10 mm |
| requires normal kidney function and intravascular | | | | Hg in the PaCO2 level. In chronic respiratory acidosis, |
| volume status. The expected change in serum | | | | the bicarbonate concentration level decreases by 5 |
| bicarbonate concentration can be estimated as | | | | mEq/L for each decrease of 10 mm Hg in the PaCO2 |
| follows: | | | | level. Plasma bicarbonate levels rarely drop below 12 |
| - Acute | | | | mm Hg secondary to compensation for primary |
| - Bicarbonate (HCO3 -) falls 2 mEq/L for each | | | | respiratory alkalosis. |
| decrease of 10 mm Hg in the PCO2 | | | | Complete blood cell count |
| - That is, ?HCO3 = 0.2(?PCO2) | | | | - An elevation of the WBC count may indicate early |
| - Maximum compensation: HCO3 - = 12-20 mEq/L | | | | sepsis as a possible etiology of respiratory alkalosis. |
| Chronic | | | | - A reduced hematocrit value may indicate severe |
| - Bicarbonate (HCO3 -) falls 5 mEq/L for each | | | | anemia as the potential cause of respiratory alkalosis. |
| decrease of 10 mm Hg in the PCO2 | | | | Liver function test: Findings may be abnormal if hepatic |
| - That is, ?HCO3 = 0.5(?PCO2) | | | | failure is the etiology of the respiratory alkalosis. |
| - Maximum compensation: HCO3 - = 12-20 mEq/L | | | | Cultures of blood, sputum, urine, and other sites: These |
| Note that a plasma bicarbonate concentration of less | | | | should be considered, depending on information |
| than 12 mmol/L is unusual in pure respiratory alkalosis | | | | obtained from the history and physical examination and |
| alone. | | | | if sepsis or bacteremia are thought to be the cause |
| The expected change in pH with respiratory alkalosis | | | | of the respiratory alkalosis. |
| can be estimated with the following equations: | | | | Imaging Studies |
| - Acute respiratory alkalosis: Change in pH = 0.008 X | | | | - Chest radiography |
| (40 – PCO2) | | | | - Perform chest radiography to help rule out pulmonary |
| - Chronic respiratory alkalosis: Change in pH = 0.017 X | | | | disease as a cause of hypocapnia and respiratory |
| (40 – PCO2) | | | | alkalosis. |
| Frequency | | | | - Potential etiologies that may be confirmed based on |
| United States | | | | chest radiography findings include pneumonia, |
| The frequency of respiratory alkalosis varies | | | | pulmonary edema, aspiration pneumonitis, |
| depending on the etiology. It is the most common | | | | pneumothorax, and interstitial lung disease. |
| acid-base abnormality observed in critically ill patients. | | | | CT scanning |
| Mortality/Morbidity | | | | - CT scanning of the chest may be performed if chest |
| Morbidity and mortality of patients with respiratory | | | | radiography findings are inconclusive or a pulmonary |
| alkalosis depend on the nature of the underlying cause | | | | disorder is strongly considered as a differential |
| of the respiratory alkalosis and associated conditions. | | | | diagnosis. CT scanning is more sensitive for helping |
| Clinical | | | | detect disease, and findings may reveal abnormalities |
| History | | | | not seen on the chest radiograph. |
| Clinical manifestations of respiratory alkalosis depend | | | | - Consider spiral CT angiography of the chest if |
| on its duration, its severity, and the underlying disease | | | | pulmonary embolism is suggested. |
| process. | | | | - Consider CT scanning of the brain if a central cause |
| - The hyperventilation syndrome can mimic many | | | | of hyperventilation and respiratory alkalosis is |
| conditions that are more serious. Symptoms may | | | | suggested. Specific etiologies that may be diagnosed |
| include paresthesias, circumoral numbness, chest pain | | | | based on brain CT scan findings include |
| or tightness, dyspnea, and tetany. | | | | cerebrovascular accident, CNS tumor, and CNS |
| - Acute onset of hypocapnia can cause cerebral | | | | trauma. |
| vasoconstriction. Therefore, an acute decrease in | | | | Ventilation perfusion scanning: Consider this scan in |
| PCO2 reduces cerebral blood flow and can cause | | | | patients who are unable to have intravenous contrast |
| neurologic symptoms, including dizziness, mental | | | | to assess for pulmonary embolism. |
| confusion, syncope, and seizures. | | | | Brain MRI |
| - The first cases of spontaneous hyperventilation with | | | | - If a central cause of hyperventilation and respiratory |
| dizziness and tingling leading to tetany were described | | | | alkalosis is suggested and the initial brain CT scan |
| in 1922 by Goldman in patients with cholecystitis, | | | | findings are negative or inconclusive, an MRI of the |
| abdominal distention, and hysteria.2 | | | | brain can be considered. |
| - Haldane and Poulton described painful tingling in the | | | | - MRIs may reveal abnormalities not seen on CT |
| hands and feet, numbness and sweating of the hands, | | | | scans. Possible etiologies based on MRIs include |
| and cerebral symptoms following voluntary | | | | cerebrovascular accident, CNS tumor, and CNS |
| hyperventilation.3 | | | | trauma. |
| Physical | | | | Procedures |
| Physical examination findings in patients with | | | | - Perform a lumbar puncture if the history and physical |
| respiratory alkalosis are usually nonspecific and are | | | | examination findings are suggestive of a CNS |
| related to the underlying illness or cause of the | | | | infectious process. Perform cytologic analysis in |
| respiratory alkalosis. | | | | patients suggested to have meningeal metastasis. |
| - Many patients with hyperventilation syndrome appear | | | | Treatment |
| anxious and are frequently tachycardic. | | | | Medical Care |
| Understandably, tachypnea is a frequent finding. | | | | Treatment of respiratory alkalosis is primarily directed |
| - In acute hyperventilation, chest wall movement and | | | | at correcting the underlying disorder. |
| breathing rate increase. In patients with chronic | | | | - Respiratory alkalosis itself is rarely life threatening. |
| hyperventilation, these physical findings may not be | | | | Therefore, emergent treatment is usually not indicated |
| obvious. | | | | unless the pH level is greater than 7.5. Because |
| - Positive Chvostek and Trousseau signs may be | | | | respiratory alkalosis usually occurs in response to |
| elicited. | | | | some stimulus, treatment is usually unsuccessful unless |
| - Patients with underlying pulmonary disease may have | | | | the stimulus is controlled. |
| signs suggestive of pulmonary disease, such as | | | | - If the PCO2 is corrected rapidly in patients with |
| crackles and rhonchi. Cyanosis may be present if the | | | | chronic respiratory alkalosis, metabolic acidosis may |
| patient is hypoxic. | | | | develop due to the renal compensatory drop in serum |
| - If the underlying pathology is neurologic, the patient | | | | bicarbonate. |
| may have focal neurologic signs or a depressed level | | | | - The tidal volume and respiratory rate may be |
| of consciousness. | | | | decreased in mechanically ventilated patients who |
| - Cardiovascular effects of hypocapnia in healthy and | | | | have respiratory alkalosis. Inadequate sedation and |
| alert patients are minimal, but in patients who are | | | | pain control may be the etiology of respiratory |
| anesthetized, critically ill, or receiving mechanical | | | | alkalosis in patients breathing over the set ventilator |
| ventilation, the effects can be more significant. Cardiac | | | | rate. |
| output and systemic blood pressure may fall as a | | | | - In hyperventilation syndrome, patients benefit from |
| result of the effects of sedation and positive-pressure | | | | reassurance, rebreathing into a paper bag during acute |
| ventilation on venous return, systemic vascular | | | | episodes, and treatment for underlying psychological |
| resistance, and heart rate. | | | | stress. Sedatives and/or antidepressants should be |
| - Cardiac rhythm disturbances may occur because of | | | | reserved for patients who have not responded to |
| increased tissue hypoxia related to the leftward shift | | | | conservative treatment. Beta-adrenergic blockers may |
| of the hemoglobin-oxygen dissociation curve. | | | | help control the manifestations of the hyperadrenergic |
| Causes | | | | state that can lead to hyperventilation syndrome in |
| The differential diagnosis of respiratory alkalosis is | | | | some patients. |
| broad; therefore, a thorough history, physical | | | | - In patients presenting with hyperventilation, a stepwise |
| examination, and laboratory evaluation are helpful in | | | | approach should be used to rule out potentially |
| limiting the differential and arriving at the diagnosis. | | | | life-threatening, organic causes first. |
| - Central nervous system | | | | Consultations |
| - Pain | | | | Based on the findings from the history, physical |
| - Hyperventilation syndrome | | | | examination, laboratory studies, and imaging modalities, |
| - Anxiety | | | | the necessity for assistance from consultants such as |
| - Psychosis | | | | pulmonologists, neurologists, or nephrologists can be |
| - Fever | | | | determined. |
| - Cerebrovascular accident | | | | Follow-up |
| - Meningitis | | | | Prognosis |
| - Encephalitis | | | | - The prognosis of respiratory alkalosis is variable and |
| - Tumor | | | | depends on the underlying cause and the severity of |
| - Trauma | | | | the underlying illness. |
| Hypoxia | | | | Patient Education |
| - High altitude | | | | - Patients with hyperventilation syndrome as the |
| - Severe anemia | | | | etiology of their respiratory alkalosis may particularly |
| - Right-to-left shunts | | | | benefit from patient education. The underlying |
| Drugs | | | | pathophysiology should be explained in simple terms, |
| - Progesterone | | | | and patients should be instructed in breathing |
| - Methylxanthines | | | | techniques that may be used to relieve the |
| - Salicylates | | | | hyperventilation. Reassurance is key for these patients. |
| - Catecholamines | | | | Miscellaneous |
| - Nicotine | | | | Medicolegal Pitfalls |
| Endocrine | | | | - The most important factor in managing respiratory |
| - Pregnancy | | | | alkalosis is to recognize that it may be associated with |
| - Hyperthyroidism | | | | serious medical disorders. Many of these conditions |
| Pulmonary | | | | may be life threatening if not diagnosed early. If the |
| - Pneumothorax/hemothorax | | | | cause of respiratory alkalosis cannot be readily |
| - Pneumonia | | | | determined, a list of differential diagnoses should be |
| - Pulmonary edema | | | | developed and all serious medical conditions should be |
| - Pulmonary embolism | | | | excluded. |
| - Aspiration | | | | |