NAPLEX Math Help: Acid Base Disorder

[NaplexRx]

Please help me how to approach this type of questions:

A babysitter brings a 9-year-old girl to the ER. She is unarousal. Labs are ordered & an ABG is drawn. The ABG results are as follows: 7.49/42/85/39/96. What acid base disorder does the child have?
A. Metabolic acidosis
B. Metabolic alkalosis
C. Respiratory acidosis
D. Respiratory alkalosis

Thanks so much!!!

---

Members don't see this ad.

 

[zzll]

answer is b. you have to know what the items in ABG results stand for. pH/pCO2/pO2/HCO3-/O2sta and the normal range for pH, pCO2 and HCO3. In your question, pH7.49 is beyond the normal range 7.35-7.45, so it's alkalosis. HCO3- is high in this case (normal range is 22-26). If HCO3- is out of range, it's metabolic disorder. If pCO2 is out of range, it's respiratory disorder. So the answer is Metabolic Alkalosis. You can find this in RxPrep. I'm not sure if it is in renal disease part.

 

[NaplexRx]

Got it! Thank you so much for your help.

 

[NaplexRx]

Oh, what about in the case where both paCO2 & HCO3 are out of range? As seen in this question:

A patient has the following ABG: pH=7.6, paCO2=60, HCO3=32. What's the acid-base disorder in this patient?

I know it's Alkalosis (since pH is out of range). But how do I det whether it's Respiratory or Metabolic since both values are out of range??

 

[thecoolpharmboi]

Please help me how to approach this type of questions:

A babysitter brings a 9-year-old girl to the ER. She is unarousal. Labs are ordered & an ABG is drawn. The ABG results are as follows: 7.49/42/85/39/96. What acid base disorder does the child have?
A. Metabolic acidosis
B. Metabolic alkalosis
C. Respiratory acidosis
D. Respiratory alkalosis

Thanks so much!!!

B.

Oh, what about in the case where both paCO2 & HCO3 are out of range? As seen in this question:

A patient has the following ABG: pH=7.6, paCO2=60, HCO3=32. What's the acid-base disorder in this patient?

I know it's Alkalosis (since pH is out of range). But how do I det whether it's Respiratory or Metabolic since both values are out of range??

I believe it is chronic metabolic alkalosis resulting in compensating respiratory acidosis. Here's an explanation I found online:

Increases in arterial blood pH depress respiratory centers. The resulting alveolar hypoventilation tends to elevate PaCO2 and restore arterial pH toward normal. The pulmonary response to metabolic alkalosis is generally less predictable than the response to metabolic acidosis. Hypoxemia, as a result of progressive hypoventilation, eventually activates oxygen-sensitive chemoreceptors; the latter stimulates ventilation and limits the compensatory pulmonary response. Consequently, PaCO2 usually does not rise above 55 mm Hg in response to metabolic alkalosis. As a general rule, PaCO2 can be expected to increase 0.25–1 mm Hg for each 1 mEq/L increase in [HCO3–].

I'm not 100% sure if what I said is right myself (not very good at this) but I think having basic idea should suffice for the test.

 

[sgkman]

Go ttu RxPREP Group on Facebook. There are bunch of people there who ask and answer questions regarding Naplex. Helped me bunch when I was preparing for the exam.

 

[NaplexRx]

B.



I believe it is chronic metabolic alkalosis resulting in compensating respiratory acidosis. Here's an explanation I found online:

Increases in arterial blood pH depress respiratory centers. The resulting alveolar hypoventilation tends to elevate PaCO2 and restore arterial pH toward normal. The pulmonary response to metabolic alkalosis is generally less predictable than the response to metabolic acidosis. Hypoxemia, as a result of progressive hypoventilation, eventually activates oxygen-sensitive chemoreceptors; the latter stimulates ventilation and limits the compensatory pulmonary response. Consequently, PaCO2 usually does not rise above 55 mm Hg in response to metabolic alkalosis. As a general rule, PaCO2 can be expected to increase 0.25–1 mm Hg for each 1 mEq/L increase in [HCO3–].

I'm not 100% sure if what I said is right myself (not very good at this) but I think having basic idea should suffice for the test.

Thank you for the explanation! I hope the NAPLEX doesn't expect us to know this extensive info.

 

[NaplexRx]

Go ttu RxPREP Group on Facebook. There are bunch of people there who ask and answer questions regarding Naplex. Helped me bunch when I was preparing for the exam.

Ok...thanks for the info! Btw, did u feel RxPrep Math was adequate for the exam? I saw the SDN packet, but seemed hard.

 

[sgkman]

I tried SDN upto question 40 or something and I just thought those questions were stupidly too hard if you know what I mean. I just tossed the rest in the trashcan and never looked at it again. passed with 118. Do it if you have time, do it so you can get the feeling of readiness.

 

[NaplexRx]

I tried SDN upto question 40 or something and I just thought those questions were stupidly too hard if you know what I mean. I just tossed the rest in the trashcan and never looked at it again. passed with 118. Do it if you have time, do it so you can get the feeling of readiness.

Oh ok...thanks! I'll probably won't bother with it then. I'll save the time to review Therapeutics. Congrats on passing. 118 is great!!!

 

[radio frequency]

When reviewing these, I found some incredibly helpful YouTube videos. One was actually by a nurse -- he had a really good system to ensure you didn't make a mistake in identifying your acid base disorders. You should try to find one!