What is Respiratory Alkalosis?
Respiratory alkalosis is an acid-base imbalance marked by decreased partial pressure of arterial carbon dioxide (less than 35 mm Hg) and increased blood pH (greater than 7.45), due to alveolar hyperventilation. Uncomplicated respiratory alkalosis lowers hydrogen ion concentration, which raises blood pH.
Causes
Pulmonary causes include severe hypoxemia, pneumonia, interstitial lung disease, pulmonary vascular disease, and acute asthma. Nonpulmonary causes include anxiety, fever, aspirin toxicity, metabolic acidosis, central nervous system disease, and pregnancy.
Complications
Watch for cardiac arrhythmias and seizures.
Signs and Symptoms
The cardinal sign is deep rapid breathing (40+ bpm). Expect CNS and neuromuscular disturbances: lightheadedness, agitation, circumoral and peripheral paresthesias, carpopedal spasms, twitching, and muscle weakness. A positive Chvostek's sign, nausea and vomiting, and muscle twitching round out the picture.
Assessment
Circulation: a history or presence of anemia and palpitations; hypotension, tachycardia, and irregular pulse or dysrhythmias.
Ego integrity: extreme anxiety, the most common cause of hyperventilation.
Food and fluid: dry mouth, nausea, and vomiting; abdominal distension from an elevated diaphragm (ascites, pregnancy) with vomiting.
Neurosensory: headache and tinnitus; numbness and tingling of the face, hands, and toes with circumoral and generalized paresthesia; lightheadedness, syncope, vertigo, and blurred vision; confusion, restlessness, obtunded responses, and coma; hyperactive reflexes, positive Chvostek's sign, tetany, and seizures; heightened sensitivity to environmental noise and activity; muscle weakness and unsteady gait.
Pain and discomfort: muscle spasms or cramps, epigastric pain, and precordial pain (tightness).
Respiration: dyspnea, a history of asthma or pulmonary fibrosis, or recent move or visit to high altitude; tachypnea with rapid, shallow breathing and hyperventilation (often 40 or more respirations per minute); intermittent periods of apnea.
Safety: fever.
Teaching and learning: use of salicylates or salicylate overdose, catecholamines, or theophylline. Care may require a change in the treatment or therapy of the underlying disease process or condition.
Diagnostic Studies
Confirm the diagnosis with arterial blood gas (ABG) analysis showing PaCO2 less than 35 mmHg and pH above 7.45, elevated in proportion to the fall in PaCO2 (acute) or falling toward normal as the kidneys excrete bicarbonate to compensate (chronic) (StatPearls, Alkalosis). ABG studies reveal abnormal values: pH above 7.45 and partial pressure of carbon dioxide below 35 mmHg.
Arterial pH is greater than 7.45 (may be near normal in the chronic stage). Bicarbonate (HCO3) is normal or decreased, less than 25 mEq/L (compensatory mechanism). PaCO2 is decreased, less than 35 mm Hg (primary). Serum potassium is decreased, serum chloride is increased, and serum calcium is decreased. Urine pH is increased, greater than 7.0.
Run screening tests to find the cause: CBC may reveal severe anemia (decreasing oxygen-carrying capacity); blood cultures may identify sepsis (usually Gram-negative); blood alcohol may be markedly elevated (acute alcoholic intoxication); a toxicology screen may reveal early salicylate poisoning; and chest x-ray or lung scan may reveal multiple pulmonary emboli.
Nursing Priorities
Achieve homeostasis, prevent or minimize complications, and provide information about the condition, prognosis, and treatment needs as appropriate.
Discharge Goals
Restore physiologic balance, keep the patient free of complications, confirm the condition, prognosis, and treatment needs are understood, and put a plan in place to meet needs after discharge.
Care Setting
Respiratory alkalosis does not occur in isolation. It is a complication of a broader problem and usually requires inpatient care in a medical-surgical or subacute unit.
Related Concerns
Use plans of care specific to the predisposing factors: anemias (iron deficiency, pernicious, aplastic, hemolytic), cirrhosis of the liver, craniocerebral trauma, hyperthyroidism, fluid and electrolyte imbalances, chronic heart failure, microbial pneumonia, sepsis or septicemia, and mechanical ventilatory assistance. Other concerns include metabolic acidosis and metabolic alkalosis.
Nursing Diagnosis
Possible nursing diagnoses include impaired gas exchange, ineffective breathing pattern, ineffective tissue perfusion, acute confusion, and risk for injury.
Nursing Interventions and Considerations
Stay alert for changes in neurologic, neuromuscular, or cardiovascular function. Institute safety measures for the patient with vertigo or the unconscious patient. Rule out life-threatening causes of hyperventilation first, since myocardial infarction, pulmonary embolism, and pneumothorax can all present this way. Once those are excluded, reassurance and coaching the patient to slow the breathing are usually enough to end an anxiety-driven episode (StatPearls, Hypocarbia). Encourage the anxious patient to verbalize fears, and administer sedation as ordered. Keep the patient warm and dry. Do not use paper-bag rebreathing: it is no longer recommended because it can cause dangerous hypoxia and deaths have occurred in patients whose underlying MI, pulmonary embolism, or pneumothorax was mistaken for simple hyperventilation (StatPearls, Hypocarbia). Monitor vital signs. Monitor ABGs, primarily PaCO2; a value less than 35 mmHg indicates too little CO2 (carbonic acid).
Frequently Asked Questions
What ABG values confirm respiratory alkalosis? A pH above 7.45 with a PaCO2 below 35 mmHg confirms respiratory alkalosis (StatPearls, Alkalosis). In the chronic form the kidneys excrete bicarbonate, so HCO3 drops and the pH drifts back toward normal.
What is the most common cause? Anxiety-driven hyperventilation is the cause you will see most often. Other triggers include fever, pain, hypoxemia, pneumonia, pulmonary embolism, salicylate (aspirin) toxicity, pregnancy, and central nervous system disease (StatPearls, Hypocarbia).
Why do patients feel tingling and muscle spasms? Alkalosis lowers ionized calcium, which raises neuromuscular excitability. That produces circumoral and peripheral paresthesias, carpopedal spasm, a positive Chvostek's sign, and tetany.
Should you use a paper bag for hyperventilation? No. Paper-bag rebreathing is no longer recommended because it can cause hypoxia, and patients with a missed myocardial infarction, pulmonary embolism, or pneumothorax have died after being treated for presumed hyperventilation (StatPearls, Hypocarbia). Rule out serious causes first, then coach slow breathing and reassure the patient.
How do you treat anxiety-driven respiratory alkalosis? Once life-threatening causes are excluded, calm reassurance, explaining why the symptoms happen, and coaching slower breathing usually end the episode. Treat any underlying medical cause directly.
What complications should you watch for? The dangerous endpoints are cardiac arrhythmias and seizures, both linked to the low ionized calcium and the shift in pH, so monitor cardiac rhythm and protect the patient from injury.