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The second acid-base imbalance we’re going to talk about is respiratory alkalosis.
The lab values you’re going to see here are a high pH, obviously indicating alkalosis, and a low PaCO2. While it’s always possible, it’s relatively rare to see a significant hypoxemia with respiratory alkalosis, because it usually means the patient is breathing really fast or deep. BUT – they can only keep that up for so long, so make sure you’re still watching oxygenation levels!
So, because we know that high CO2 levels equal acidosis, we can reasonably deduce that LOW CO2 levels or a loss of CO2 would cause a respiratory alkalosis. The most common cause is hyperventilation. This could be too fast or too deep or both. Let’s use the same pressure release valve analogy from respiratory acidosis. Except, in this case, the pressure release valve on the water heater is stuck open. All the steam is escaping and it’s impossible to actually heat your water. In this case, all the CO2 is escaping because of this crazy breathing pattern and it’s impossible to get a good acid-base balance. This crazy breathing pattern could be due to anxiety or fear, or even a fever or it could also be compensating for hypoxia or even for a metabolic acidosis. Remember that compensation is when the opposite system tries to compensate. So if I have a metabolic acidosis, my respiratory system will try to compensate for it by creating an alkalotic state – sometimes it just goes a little too far and overcompensates! Another time we can see respiratory alkalosis is when a patient is on a mechanical ventilator and the breathing rate or tidal volume is set too high. Without realizing it, we have blown off way too much of their CO2. Fortunately – that’s an easy fix – just turn the rate or volume down!
So, again, we’re going to see signs and symptoms of the cause. They may tell you they’re anxious or you may see tachycardia or a fever. Or we may actually see that the rate on the ventilator is set at 30 with huge tidal volumes. Then, we’re going to see signs of the alkalosis itself – lightheadedness, numbness and tingling, shortness of breath, and even chest discomfort. And, of course, because our brain is so super sensitive to changes in our pH and CO2 levels, there will be some confusion as well. If any of you have ever hyperventilated, you probably know what this feels like. I remember one time when I was in middle school, I was crying so hard, I think I had slammed my hand in a door or something, and I was hyperventilating from the pain. I remember getting really lightheaded, and the next thing I remember, my mom was waking me up and picking me up off the ground because I had passed out! Luckily, when I passed out, I stopped freaking out, started breathing normally, and my CO2 levels levelled off enough for me to wake back up! But, think about someone who can’t seem to stop hyperventilating, or someone who has some sort of underlying process making them hyperventilate. Eventually, their body will give out – they can’t keep that up for that long, right? They’re going to end up exhausted and eventually they will stop being able to protect their own airway.
So, the #1 thing we need to do for someone in respiratory alkalosis is fix whatever is causing it! If it’s an anxiety, fear, or fever situation, we treat that. We can reassure them, make sure they know they’re safe, and even try the paper bag trick! I’m sure you’ve seen this before – we have people breathe into a paper bag. While it may not actually decrease their anxiety, it will keep them from going into respiratory alkalosis. Think about it, if they are breathing out into a paper bag, and then breathing back in – they’re rebreathing their exhaled CO2, right? so it keeps their CO2 levels from getting too low. This is certainly not a permanent fix or a miracle cure, but it will keep them from passing out! We also want to address any ventilator settings that might be wonky. Make sure you are checking with your facility’s policy. In MOST cases, the Respiratory Therapist is really the only one who should be adjusting the ventilator settings, but you can certainly talk to them and see what they think. As a last resort, if we can’t get someone to calm down or slow their breathing, we can use meds like benzodiazepines to help them relax a little. Again, it’s all about fixing the cause of the alkalosis.
Priority nursing concepts for a patient with respiratory alkalosis are going to be acid-base balance, gas exchange, and oxygenation. Remember that the hyperventilation could be due to hypoxia, or could cause the patient to tire out eventually and therefore become a breathing and oxygenation issue.
So remember that lab values for Respiratory alkalosis are a high pH and a low PaCO2. It is most commonly caused by hyperventilation for one reason or another, including anxiety, fear, compensation for hypoxia or metabolic acidosis, or mechanical ventilator settings that are inappropriate. You will see symptoms of the cause, symptoms of the alkalosis like lightheadedness, shortness of breath, or confusion. It is also possible to see some hypokalemia because of the alkalosis, but it is less common with respiratory alkalosis. And, of course, we always want to treat the cause, decrease any anxiety they have, and try to get that respiratory rate down. And of course correct any inappropriate vent settings.
Make sure you check out all the resources attached to this lesson, and check out The next two lessons for the metabolic source acid-base imbalances. Now, go out and be your best selves today. And, as always, happy nursing!!