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What causes extreme weakness with low carbon dioxide?

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The following is an actual conversation between an iCliniq user and a doctor that has been reviewed and published as a Premium Q&A.

Medically reviewed by

Dr. Divya Banu M

Published At January 28, 2020
Reviewed AtJuly 24, 2023

Patient's Query

Hello doctor,

I am experiencing episodes of extreme weakness, lethargy, and tiredness. I feel unable to get out of bed, and I find myself going to the bathroom often at night. Two years ago, I had an ECG-proven ventricular tachycardia after an episode that lasted for several days. I have had lab tests done close to two episodes. A month ago, my carbon dioxide levels were slightly low at 19, and there was trace blood in my urine. The USG (Urine Specific Gravity) reading was 1.005, and the urine pH was 7. Recently, this month, my second lab results showed mild low bicarbonate levels. The current medications I am taking include Methotrexate, Mobic, Metoprolol, Vitamin D, and Folic acid. I have undergone lab tests for blood and urinalysis.

Kindly help.

Hello,

I am glad you chose icliniq for your medical-related queries.

I understand your concern.

I went through your reports that you sent (attachment removed to protect patient identity). One report shows a slightly low normal potassium level of 3.8. V-tach (ventricular tachycardia) can potentially be associated with low potassium levels. There could be a condition called distal renal tubular acidosis, for which we need to check urine sodium, potassium, chloride, and creatinine levels, and calculate the urinary anion gap. Also, I would like to know how long you have been taking Methotrexate?

Hope I have clarified your query.

Thank you.

Patient's Query

Hi doctor,

Thank you for answering so quickly with some ideas. I would be interested in exploring how to rule out the renal acidosis. If you make recommendations on which additional labs to collect I will try to get them during next episode if I can get to my general practitioner. I have taken Methotrexate for the past 10 years but recently halved my dose of it. This issue with the tired spells began four years back. I have a history of dermatomyositis and have recently weaned off Prednisone, which I hoped would have fixed the issues but I have had two episodes since stopping the Prednisone.

During the ventricular tachycardia (VT) episode in the hospital, my Blood Urea Nitrogen (BUN) Creatinine level was low at 11.2 (range 12-20), Chloride (CL) level was high at 110 (range 98-107), and Potassium (K) level was within the normal range at 4 (range 3.5-4.1). On the second day of admission in the Critical Care Unit (CCU) on intravenous (IV) therapy, my BUN Creatinine level was high at 21.7, Chloride (Cl) level remained high at 111, Carbon dioxide (CO2) level was low (22-32), and Potassium (K) level was normal at 3.7 (range 3.5-5.1). I was discharged on Metoprolol, and it seemed to help with the episodes, but I still occasionally experience them. I am considering seeking a kidney consultation after a suggestion from a nurse friend.

Hi,

Welcome back to icliniq.com.

So, as I note, most of the time your potassium is nearly within the normal range, but CO2 in the blood is low. Regarding muscle weakness, it could be due to your dermatomyositis, and sometimes, long-term steroid exposure can cause proximal muscle weakness and symptoms like difficulty getting up from a squatting position. To rule this out, we will need to conduct an EMG (electromyography) and NCS (nerve conduction studies). Regarding renal tubular acidosis, we should measure urinary sodium, potassium, chloride, and creatinine levels. Additionally, we should conduct an arterial blood gas test to check pH and bicarbonate levels. Also, please measure your serum osmolarity again, as it was elevated to 320 some months ago. We will likely get a clear picture after conducting these tests. Till then, take care.

I hope this has helped you.

Thank you.

Patient's Query

Hi doctor,

Thank you for the reply.

Ok, so I read up on this, and it says autoimmune disorders can cause distal renal tubular acidosis (RTA). I have had low complement in the past, so my dermatomyositis is more of the overlap variety of connective tissue disorder. So, I think ruling out this RTA might be a good idea since it seems to be very treatable. I am going to my general practitioner this week to talk to her about this, and I guess my main questions are:

  1. Can this manifest in discrete episodes or extreme weakness verging on paralysis?
  2. Do you know of cases where this was induced by medications or diet?
  3. Do you know why my osmolality is high if I drink plenty of water and have no diarrhea or vomiting? Should not my ADH (antidiuretic hormone) also be high if my osmolality is that high?
  4. My bicarbonate is not super low, but only mildly low. Is that enough to convince a doctor to try to test for RTA? As I understand it, when my bicarbonate is low, my urine pH should be adjusting to it, so is 7 a bit high to have at the same time as low bicarbonate?
  5. My electrocardiogram, in addition to ventricular tachycardia, have had t-wave inversions, left axis deviation, and right conduction delays. Could that be caused by something like this?

Hello,

Welcome back to icliniq.com.

  1. Yes, only if hypokalemia is severe, as I said. It can be because of your original disease and steroids.
  2. Yes, but not in your case.
  3. That is something odd.
  4. High urinary pH is indicative of distal renal tubular acidosis (RTA).
  5. Yes, definitely.

Hope I have solved your query. I will be happy to help you further.

Thank you.

Patient's Query

Hello doctor,

Thank you for your prompt reply.

My last EKG was four years back, and I still have myopathy, but it showed up as mild non-irritable myopathy in my proximal muscles and also my tibia muscle. I was told it could be because of longstanding disease. Thank you for the answers. I was going to ask the doctor if maybe my ADH could be low because of long-term steroid use and adrenal insufficiency to see if that would be playing a role. I drink 100 ounces of water a day plus sports drink, so it is really frustrating to be constantly told I am not drinking enough. My urine pH has been 7. Is urine pH of 7 not neutral? Or is it that it should be lower in the context of low bicarbonate? My bicarbonate is not always low; it only seems to be low during these attacks. Could you explain a little bit about why you think it is good to rule out distal RTA? I appreciate your time. Sorry, I meant EMG above in the previous query.

Hello,

Welcome back to icliniq.com

Ideally, urine pH should be acidic, while blood is acidic, and urine is neutral. That means there can be a problem in urine acidification, and that is what RTA (Renal Tubular Acidosis) is. ADH (antidiuretic hormone) release in the body is pulsatile, so one reading cannot tell you anything.

Hope I have helped you.

Thank you.

Patient's Query

Hello doctor,

Thank you for the insight.

I understand a little better now. So, you are saying maybe if my osmolality went up a little more, the ADH would punch the gas eventually, basically? One last question on RTA, could it make me dehydrated? My time limit is just about up. I will run these tests by my doctor and let you know at a later date if they yield any useful information on my case.

Thank you for your time.

Hello,

Welcome back to icliniq.com.

Your high osmolality is a bit odd; that is why I suggested you do investigations and repeat the osmolality test. RTA (renal tubular acidosis) can cause dehydration. Take care.

Hope I have clarified your query.

Thank you.

Same symptoms don't mean you have the same problem. Consult a doctor now!

Dr. Pankaj Jawandhiya
Dr. Pankaj Jawandhiya

Nephrology

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