Respiratory Alkalosis: Easy-to-Understand Explanation of Causes, Symptoms, and Treatment
What IS Respiratory Alkalosis?
Respiratory Alkalosis is a medical condition that occurs when too much Carbon Dioxide (CO2) leaves the body, which indirectly causes the blood pH to decrease increase above 7.45.
When too much CO2 leaves the body, it causes a chain reaction that decreases the amount of Hydrogen ions (H+) floating around. This decrease in H+ is what makes the blood pH increase, which makes the bloodstream more alkaline.
Basically: less CO2 = less H+ = more alkaline = higher pH
Your blood can become alkaline for other reasons, too. But when it becomes alkaline because of the CO2 levels, that is what makes it Respiratory Alkalosis.
What is the main cause of Respiratory Alkalosis?
Under normal circumstances, your body can adjust how much CO2 stays or leaves the bloodstream by controlling how fast or slow, and how shallow or deeply you breath. Therefore, the main cause of Respiratory Alkalosis is a pattern of breathing that results in the body getting rid of too much CO2. You might hear medical professionals refer to this as “blowing off” CO2, since the CO2 leaves the body through exhaling.
This pattern of “blowing off” CO2 can be caused by different underlying medical conditions. Basically, any condition that can disable the lungs from being able to hold on to CO2 can lead to Respiratory Alkalosis.
Why do I explain this first rather than just give you a list of conditions that can cause it (like everybody else does)? Because it’s better to understand the pathophysiology behind a condition, rather than simply memorizing a list of causes. You’re more likely to remember this way, AND you’re better able to critically think your way through test questions. That’s why I prefer to divide the causes of Respiratory Alkalosis into related categories.
Hyperventilation is the most common cause of Respiratory Alkalosis. In fact, many of the other diseases or causes that I mention below technically lead to Respiratory Alkalosis by causing hyperventilation first!
It’s easy to remember what hyperventilation is if you identify the root words: hyper-, and ventilation. When used as a prefix, the term “hyper-” means above and beyond, or excessive. Ventilation refers to the process of circulating air. Put them together, and it means that your lungs are “circulating air” (otherwise known as breathing!) faster than usual.
When you breath faster than usual, you’ll be exhaling, or “blowing off”, CO2 faster than usual, too. As the CO2 decreases, so does the H+. Before you know it, this loss of acid (H+) causes blood pH to increase and become more alkaline. And that’s Respiratory Alkalosis!
We commonly think of hyperventilation as being caused by anxiety or a full blown panic attack. But it also has many other possible causes, including iatrogenic reasons (aka the medical treatment!!).
One example of an iatrogenic cause is mechanical ventilation. If the mechanical ventilation rate is accidentally set too hight, then you force the patient into hyperventilation! Oops!
Certain medications can also cause Respiratory Alkalosis, too. Any substance having the potential to chemically cause hyperventilation, has the potential to be a main cause of Respiratory Alkalosis.
For example, catecholamines (like epinephrine), salicylates (like aspirin), and nicotine can all carry the risk of increasing respirations enough so that metabolic alkalosis could occur.
Problems in the brain stem that effect the respiratory control center can also lead to hyperventilation, and then respiratory alkalosis. For example, a tumor or brain damage could prevent the brain from sending the proper messages to the lungs. If the brain doesn’t tell the lungs to breath less frequently in response to certain variables, then CO2 can decrease in the blood.
Hypermetabolic State and More
A hypermetabolic state is a state of increased metabolic activity in the body. This can be related to a fever, or a more serious condition like sepsis or liver failure. A hypermetabolic state is a potential cause of rapid breathing, which can then progress to Respiratory Alkalosis.
Other potential causes that don’t necessarily fit into a tidy category include hypoxia at high altitudes, low blood pressure (hypotension) and pulmonary disease or embolism.
What are the different types of Respiratory Alkalosis?
Uncompensated Respiratory Alkalosis (Acute)
Uncompensated Respiratory Alkalosis is an acute condition that can come on suddenly. Under normal circumstances, the kidneys can help the lungs maintain correct blood pH by retaining H+ (an acid) and excreting bicarbonate (HCO3–, a base). However, because acute respiratory alkalosis can develop so quickly, the kidneys don’t have enough time to respond and balance out the pH.
The result is that there is too little CO2 in the blood, a normal amount of bicarbonate, and the blood pH increases above 7.45 to become more alkaline.
Fully Compensated Respiratory Alkalosis (Chronic)
Fully Compensated Respiratory Alkalosis is usually a chronic condition that comes on gradually. The slower pace of this imbalance allows time for the kidneys to help maintain healthy blood pH by retaining enough H+ and excreting excess bicarbonate.
Since the total bicarbonate level has time to decrease, AND the H+ is being preserved by the kidneys as much as possible, the net results are that there is too little CO2 AND too less than normal bicarbonate in the blood, so the pH moves back to the normal range of 7.35-7.45. The pH will lean towards the alkaline side however, so you’re more likely to see a pH of 7.41-7.45.
Partially Compensated Respiratory Alkalosis
Partially Compensated Respiratory Alkalosis is more of an “in-between” stage for when a patient is moving from Uncompensated Respiratory Alkalosis into Fully Compensated Respiratory Alkalosis.
As the lungs are blowing off too much CO2 and H+, the blood pH gradually increases and becomes more alkaline. At the same time, however, the the kidneys begin compensating by retaining H+ and eliminating bicarbonate to balance out the pH.
However, for Partially Compensated Respiratory Alkalosis, the kidneys have not had time to completely compensate for the lungs yet (if they had, then this would be called Fully Compensated Respiratory Alkalosis ?)
So you end up with too little CO2 AND too little bicarbonate, but the pH is still abnormal and in the alkaline range (greater than 7.45).
What are the symptoms of Respiratory Alkalosis?
Nursing textbooks (and professors) are great about listing LOTS of symptoms of Respiratory Alkalosis. The problem is, many of these signs and symptoms are rather generic, and could be true of many illnesses that are completely unrelated.
For nursing exams, you need to focus on understanding the pattern of symptoms that are specific and unique to Respiratory Alkalosis…because those are the symptoms that will show up on the exams! The most specific and unique Respiratory Alkalosis symptoms include:
Changes in Breathing Pattern
Specifically, Cheynes Stokes Respirations are a characteristic symptom of Respiratory Alkalosis. Cheynes Stokes Respirations involve a pattern where the patient gradually starts breathing deeper and faster, then gradually slows down again until they temporarily stop breathing altogether (apnea). Then the breathing pattern repeats.
Other breathing patterns that you might see would involve a reversal of the hyperventilation, into hypoventilation. This can be the body’s attempt to correct the underlying problem that causes the Respiratory Alkalosis.
Hypokalemia occurs when the cells start allowing H+ to exit, in exchange for K+ ions to enter. This helps to counterbalance the Respiratory Alkalosis by decreasing the pH, but at the expense of decreasing potassium in the blood.
With less K+ available inside the cell, the action potential for the cell membrane will be smaller and easier to trigger. This can lead to additional symptoms such as hyperreflexia and arrhythmias.
Hypocalcemia occurs because Respiratory Alkalosis creates conditions in the body that decrease the amount of free calcium ions that can be formed. This causes serum calcium levels to drop.
With less Ca+ available in the blood, you will see additional symptoms usually associated with hypocalcemia. Specifically, tetany (Chvostek’s sign and Trousseau’s sign) and/or parasthesias (especially tingling around the lips).
Abnormal ABG Results
Not surprisingly, a patient with Respiratory Alkalosis will have abnormal ABG results: PaCO2 less than 35 and pH greater than 7.45 (or pH between 7.41-7.45 if Compensated).
You might also hear the low CO2 level referred to as “hypocapnia”. In this case, the prefix “hypo-” means low, and “-capnia” refers to the CO2 levels.
“Generic” Symptoms of Respiratory Alkalosis
- syncope (fainting)
- diaphoresis (sweating)
Do you see how impossible it is to identify these generic Respiratory Alkalosis symptoms? They also occur with just about every other illness you’ll study in nursing school. In fact, some are exactly the same as what you would observe for Respiratory Acidosis! Which is why exams will always highlight the specific and unique symptoms…so YOU should focus on them when you study, too!
What is the treatment of Respiratory Alkalosis?
Like any disease process you’ll face in nursing school, treatment of Respiratory Alkalosis is twofold:
- Manage the urgent symptoms
- Correct the root cause
That is why it’s impossible to simply memorize a list of treatments for Respiratory Alkalosis, and then expect to be able to answer correctly on an exam. The treatment you choose will always depend on the context surrounding the root cause of the problem.
Managing the Symptoms of Respiratory Alkalosis
That being said, Respiratory Alkalosis is closely linked to hyperventilation! And hyperventilation is a breathing issue (remember your ABC’s?) Therefore, hyperventilation will frequently need to be addressed.
The best way to treat basic hyperventilation, especially when the cause is anxiety-related, is to have a patient breath into a paper bag. This forces them to “rebreath” the air that they have just exhaled, which contains a higher concentration of CO2. This will prevent the patient from “blowing off” as much CO2.
In addition, if the Respiratory Alkalosis has become severe enough to produce hypokalemia and/or hypocalcemia, then you may expect to administer potassium or calcium gluconate via IV therapy. Once the electrolyte imbalance is resolved, then the additional symptoms of hyperreflexia and arrhythmias (for potassium) or tetany and parasthesias (for calcium) should resolve.
Correcting Root Causes of Respiratory Alkalosis
If the root cause of the hyperventilation is iatrogenic, then it needs to be corrected as quickly as possible. For example, if the patient is mechanically ventilated and the settings are too high…for goodness sakes, turn them down!
Similarly, if a salicylate medication, such as aspirin, has caused the Respiratory Alkalosis, then you could expect to administer treatment for salicylate poisoning. Ditto for any other medication that can lead to Respiratory Alkalosis.
As you can see, there are at least as many possible Respiratory Alkalosis treatments as there are possible causes. That is why knowing and understanding pathophysiology is so important!
Is Hyperventilation Respiratory Acidosis or Alkalosis?
Like many diseases you study in nursing school, Respiratory Alkalosis can be paired with and studied with an “opposite” disorder. In this case, the “opposite” disorder is Respiratory Acidosis. Since everything is going in “opposite” directions with these two disorders, it is confusing to keep some things straight! Hyperventilation is one of the potentially confusing causes/symptoms.
It’s true that hyperventilation can occur in BOTH respiratory acidosis and respiratory alkalosis. The difference is when hyperventilation occurs during these two disease processes.
For respiratory acidosis, hyperventilation is the result of the illness, so it is considered a symptom. CO2 has accumulated in the blood, and needs to be reduced. The rapid, shallow breathing is an attempt to “blow off” some of the excess CO2.
On the other hand, as we’ve seen repeatedly, hyperventilation is the main cause of respiratory alkalosis, which is characterized by low CO2 in the blood. Since hyperventilation can be very effective at “blowing off” CO2 from the body, it is also very effective at causing low blood CO2.
To summarize, hyperventilation is a symptom is associated with Respiratory Acidosis, but hyperventilation is the main cause that can lead to Respiratory Alkalosis.
Summary: What you NEED TO KNOW about Respiratory Alkalosis to be a safe, effective, beginning Nurse
- Respiratory Alkalosis is caused by hyperventilation, but the hyperventilation can have different causes
- Identify the unique symptoms of Respiratory Alkalosis
- Recognize abnormal ABGs (CO2 less than 35 AND pH is alkaline) – Learn how to easily interpret ABGs
- Understand the relationship between Respiratory Acidosis and Respiratory Alkalosis
- Including the role that hyperventilation plays in both!
- Respiratory Alkalosis Treatment, and how it changes depending on the root causes