For more information, visit www.nursing.com/cornell
Get unlimited access to lessons and study tools
Okay this is the last acid-base imbalance we’re going to talk about. This is metabolic alkalosis.
So, the lab values associated with metabolic alkalosis would be a high pH, a high bicarb level, and usually a base excess, which is a positive number on the base excess result. We will talk about base excess more and its own lesson later on and of course.
The general causes of metabolic alkalosis are the exact opposite of the general causes for metabolic acidosis. It is either caused by a loss of metabolic acids or by an increase in alkalis or bases. That increase in alkaline substances could come from excessive use of antacids or from the kidneys retaining excessive amounts of bicarb. The loss of acids could come from any number of conditions, the most common of which being excessive vomiting or NG Tube suction. Again, our stomach is a big bag full of hydrochloric acid. If we forcefully eject all of our acid or if we physically suck all the acid out of a patient’s stomach, the likelihood of them developing a metabolic alkalosis is very high. Another possible way they could lose too many acids is through the use of diuretics, especially potassium wasting diuretics like furosemide. Here’s the thing – not only can alkalosis cause hypokalemia, but hypokalemia can also cause alkalosis for the same reasons. If the body sees too little potassium in the bloodstream, it may try to bring more out of the cells. In doing so, it needs to replace it with hydrogen – therefore decreasing the hydrogen in the bloodstream causing an alkalosis. It’s kind of a chicken-or-the-egg type of situation. Just know that alkalosis and hypokalemia are closely related. The other thing you may have picked up on is that metabolic acidosis causes vomiting, but vomiting causes metabolic alkalosis. Think about it, if I’m acidotic and I start vomiting to get rid of acid, I could swing too far into alkalosis, right? So, if you’re taking a test or you’re looking a patient’s symptoms – ask yourself – am I thinking about a cause or a symptom? Is it asking “what caused this situation?” or “what would you see in this patient?” For example – your patient has been vomiting for 3 days due to a stomach flu, what acid-base imbalance would you expect as a result? Okay – that much vomit means loss of acids, so alkalosis. How about, “Your patient presents with altered level of consciousness and vomiting, what acid-base imbalance could be causing their symptoms?” Okay – I vomit to get rid of acids, so I probably have metabolic acidosis. Just use your critical thinking skills to figure out which direction we’re coming from.
Okay – so again, signs of the cause, signs of alkalosis, and signs of hypokalemia. The signs of alkalosis, in this case, will be altered LOC, headache, numbness and tingling, and a decreased respiratory rate. Why? Because my lungs are trying to compensate by hanging onto that acidic carbon dioxide. And signs of hypokalemia like arrhythmias and EKG changes.
Our number one priority when treating metabolic alkalosis is going to be to fix the underlying cause. This might mean addressing the loss of fluids from all of the vomiting or administering potassium. But, also, administering IV sodium chloride, AKA normal saline, is actually highly indicated for metabolic alkalosis because the chloride will help to correct the pH. And, of course, we could always do dialysis to address any issues brought on by the kidneys and to force correction of the acid-base imbalance.
Priority nursing concepts for a patient with metabolic alkalosis or going to be acid-base balance, gas exchange, and any other priorities associated with the underlying condition. Remember that these clients might slow their breathing rate down to retain CO2 to compensate and bring the pH back down, so it’s going to be important to evaluate oxygenation and gas exchange as well.
Let’s recap. Lab values associated with metabolic alkalosis or going to be a high pH and a high bicarb level, as well as a positive High base excess. Causes of metabolic alkalosis or a loss of acids as in vomiting or NG tube suctioning, or an increase in alkaline substances like with excessive use of antacids or if the kidneys hold on to Too Much bicarb. Also, don’t forget that hypokalemia and alkalosis very closely related. You will see symptoms of the underlying cause, symptoms of the alkalosis like altered level of consciousness and decrease respiratory rate, and possible signs of hypokalemia. We always want to treat the cause, but we also recognize that IV sodium chloride and potassium supplements can be very helpful as well as dialysis.
So, those are the four main acid-base imbalances that you need to know. Go back and review them as often as you need to to make sure that you understand the difference. And, don’t forget to check out all the resources attached to this lesson. Now, go out and be your best selves today. And, as always, happy nursing!!