Fluid, Electrolyte & Acid-Base · Topic 17 of 23
Respiratory Alkalosis
The anxious post-op patient breathing 28 times per minute has a pH of 7.52 — but the real danger isn't the anxiety.
Respiratory alkalosis: read the gas in three calls
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A textbook respiratory alkalosis with no patient attached yet. Read it in three calls, then load a patient.
Make the three calls first. What to look for, what to do and what to expect ordered fill in for the disorder you find.
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Respiratory alkalosis
Breathing too fast or too deep. CO₂ is blown off, the pH rises — and the lips and fingers start to tingle.
mmHg · normal 35 – 45 · with a pH above 7.45 (normal 7.35 – 7.45)
Always breathing too fast or deep — most often anxiety or pain
Never assume anxiety until hypoxemia and pulmonary embolism are ruled out
What causes it
Watch forMost common: anxiety and pain — but rule out the serious ones first
Fast breathing can be a clue to a serious lung problem. It can also be the lungs compensating for a metabolic acidosis (e.g., DKA, or salicylate overdose later on).
What you'll see
SignsTingling around the mouth and in the fingers
Labs & diagnostics
CheckPaCO₂ below 35 with pH above 7.45
Red flags
Act nowTreatment: treat the trigger
Cause decidesSlow the breathing by treating the cause
Stay, reassure, coach slow breathing; an anxiolytic as prescribed if severe.
Give the prescribed analgesic; treat fever or infection.
The provider or respiratory therapist lowers the rate or tidal volume. Changing FiO₂ changes oxygen, not CO₂.
Not a nurse-only changeRebreathing lowers inspired oxygen — it has caused deaths when the real cause was hypoxemia or myocardial ischemia.
More detail
Nursing priorities
In orderRespiratory or metabolic alkalosis?
ROME — Respiratory Opposite, Metabolic Equal
| pH | pH above 7.45 |
|---|---|
| PaCO₂ | Low PaCO₂ (below 35) — the cause |
| HCO₃⁻ | About normal at first; below 22 as the kidneys compensate |
| Which way | PaCO₂ moves opposite to the pH (Respiratory Opposite) |
| Breathing | Fast, deep breathing — hyperventilation |
| Potassium | Can fall — shifts into cells |
| Classic causes | Anxiety, pain, hypoxemia, pulmonary embolism |
| Fix | Treat the trigger — rule out hypoxemia first |
Teach your patient
DischargeRespiratory alkalosis: CO₂ blown off by fast breathing. Rule out hypoxemia and pulmonary embolism before calling it anxiety.
Sources · OpenStax Medical-Surgical Nursing 10.4, OpenStax Fundamentals of Nursing 20.2, StatPearls on respiratory alkalosis, ABG analysis, hypocalcemia, hypokalemia, hypercapnia and pulse oximetry, Merck Manual Professional: respiratory alkalosis, and Callaham, hypoxic hazards of paper bag rebreathing (1989). Typical adult values — follow your protocol.
Respiratory Alkalosis
The anxious post-op patient breathing 28 times per minute has a pH of 7.52 — but the real danger isn't the anxiety. It's what the alkalosis does to calcium and potassium.
Respiratory alkalosis occurs when the patient hyperventilates, blowing off excess CO2 and driving the pH above 7.45 with a PaCO2 below 35 mmHg. The root problem is always alveolar hyperventilation — anxiety and pain are the most common triggers on the NCLEX, but fever, sepsis, hypoxemia, high altitudes, mechanical over-ventilation, and early salicylate toxicity also cause it. The critical downstream effect: alkalosis drops extracellular H+ concentration, so H+ shifts out of cells to buffer the blood; to maintain electrical neutrality, K+ shifts into cells, producing hypokalemia. Simultaneously, more calcium binds to albumin in alkalotic blood, dropping ionized (free) calcium levels and causing neuromuscular irritability — tingling, numbness, carpopedal spasms, and a positive Chvostek or Trousseau sign. Nursing priorities center on treating the underlying cause: coaching slow breathing, using a calm environment for anxiety-driven cases, adjusting ventilator rate/tidal volume for iatrogenic causes, and monitoring for cardiac dysrhythmias related to the electrolyte shifts. Rebreathing into a paper bag is outdated and no longer recommended because it can worsen hypoxia.
Key Distinctions
Don't confuse respiratory alkalosis (low CO2, high pH, patient is hyperventilating) with metabolic alkalosis (high HCO3, high pH, usually from vomiting or NG suction). Students often attribute numbness and tingling to the anxiety itself — it's actually the alkalosis-induced drop in ionized calcium. Iatrogenic respiratory alkalosis from mechanical ventilation is corrected by decreasing rate or tidal volume, not by adding sedation alone.
Clinical Pearl
Fast breathing blows off CO2, blows up the pH, and blows calcium and potassium into hiding — think 'blow off three things at once.'
Knowledge Check
3 quick questions on the must-knows for this topic.
What breathing problem causes respiratory alkalosis?
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Go further
- SimulatorAcid–Base & ABG SimulatorBuild a gas. Watch compensation happen. Move CO₂ or bicarbonate, then read the gas in three calls: pH, cause, compensation.
- SimulatorFluid & Electrolyte SimulatorChange one lab. Watch the whole patient respond. Sodium, potassium, calcium, magnesium, pH and volume, all linked — with a live ECG and an IV pole where every bag runs.
- GuideRespiratory vs Metabolic Acidosis and Alkalosis: The 4 Disorders With Causes, Findings and What the Nurse DoesTwo organs, two directions. Respiratory disorders are CO₂ problems that belong to the lungs and happen in minutes; metabolic disorders show up in the bicarbonate and come from everywhere else. Each of the four with its causes, what you see, what the nurse does and what the provider orders — in a table, then patient by patient, with each one loaded in a live gas.
- GuideABG NCLEX Questions: The 6 Patterns the Exam Keeps TestingThe NCLEX rarely asks you to name a gas. It asks what the gas means and what the nurse does. Name the gas with the normal-pH trap, which patient is at risk, what the nurse does first, what the provider will order, the electrolyte that moves with the pH, and the finding that means it is getting worse — with a live gas for the anticipate-the-order pattern.
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