Acid Base Q, .......................NBME 2,3,14,15 - forever07

[ArchivalUser]

Hi forevr07,I was away...
D)see in metabolic acidosis in severe diarrhea occurs as HCO3-lost in urine so urine is aways alkaline and hence the pH OF urine.So there is retention of NH4+ ions,means H+ions are retaining in body.So as u said above correctly that more CO2 means more H+ions,so CO2 must be washing out so as to provide less H+in the body which already is too much retaining,because co2 buffers with H+ ions in equation Co2+H2o=HCO3-+H+ so more co2,more would be the gainig of h+ions,and worsening the situation so co2 must be decreasing in ECF so as to start compensating unless patient is not suffering from chronic lung disease where CO2 can't get washed away as much as it should!

[ArchivalUser]

GI loss of HCO3-...in severe dehydration and if no prompt hydration RTA results.so much h+retention in kidney parenchyma would damage it and eventually it will sloughed off and lead to necrosis..

[ArchivalUser]

Hello the_dumb, thank you so much, i got u point.

So, regarding D option, that is H+ accumulation and acidosis, right?

Can it be the answer for that Q? That means metabolic acidosis.


I mean for Q17. 12-hour history of vomiting and diarrhea. ?

[ArchivalUser]

I want to clear one more thing, regarding Metabolic Alkalosis...

If CL resistant MAL...means urine CL more than 20, kidney can't save CL...ECF volume is expanded......so, we can't give Normal saline..(eg.Primary hyperaldosteronism, Bartter's)

If CL sensitive MAL...means urine CL less than 20, kidney save the CL from the body, ECF volume is depleted.....that cause contraction alkalosis ( Am i right here)....more aldosterone..causing Na & H2O retention, more H+ & K+ loss in urine. (eg.. diuretics)

So, treatment is Normal Saline

Appreciate you for helping me out.!!TQ

[ArchivalUser]

One more Q please!

Ph-7.4, co2 - 50, HCO3 - 34 ....Respiratory Acidosis plus metabolic alkalosis...so mixed.

-Where can we find this case? .....Is it Diarrhoea and COPD?
- How will be the compensation??

[ArchivalUser]

A 57-year-old woman is extubated and transferred to
the recovery room
after a cholecystectomy. She appears restless. Her
blood pressure is
120/70 mm Hg, pulse is 80/min, and respirations are
10/min. Arterial
blood gas analysis on room air shows:


pH 7.24
PCO2 85 mm Hg
PO2 60 mm Hg

Intravenous naloxone therapy is begun, but she does
not improve. Which
of the following is the most appropriate next step in
management?

A
) Encouraging deep breathing and cough

B
) Administration of 40% oxygen via nasal cannula

C
) Administration of furosemide

D
) Transfusion of 1 unit of packed red blood cells

E
) Reintubation and mechanical ventilation

[ArchivalUser]

@forever07
Q19 12 hr hx of V&D

u said D..
but i think it would be excessive metabolic acid formation rather than increase CO2 in ECF..its not like that if more acidosis means more CO2 in ECF,,here primary patho is metabolic acidosis so respiratory component has to compensate...in short HCO3- and CO2 must go in parallel direction normally while compensating for each other...As he is giving Hx of 12 hours,so by that time u see CO2 is 38 now..means he is hyperventilating(in this q from central chemoreceptors,due to shock and hypotension,less CO2 perfusion in blood in medulla oblangata and high H+,as u remember H+ can pass CNS and in acidosis more H+ ions accumulation and crossing to BBB can stimulate breathing control,MO perceives more H+ and less CO2 means he get the signal to hyperventilate the lungs) and compensating but inadequately and hence CO2 is washing out from ECF.and if in case he might could have a chronic COPD pt then PCO2 increases as well as HCO3- also must be increasing to compensate for RA..

[ArchivalUser]

@ forever07 ph=7.4,co2=50 hco3-=34
brother this is not mixed
it is Respiratory acidosis and metabolic alkalosis...which one is primary basically need more info about pathology..and clinical Sx first.
ph=7.4 means whatever compensation is almost near to get the respective component fully compensated.

mixed is when u get Resp and metabolic either acidosis or mixed
like in example here ph=7,32 co2=65,hco3-=18 u can see primary patho is in lungs and metabolism is not compensating at all,instead of increase of hco3-,we get decrease(means more H+) so kind of mixed R & M ACIDOSIS.

there r some triple acid base disorders- like 1) salicylate poisoning:where u see Anion gap M acidosis(from salicylic acid),and metabolic alkalosis(vomiting),and Resp Alkalosis as well (due to direct stimulation of respiratory center).

2)Diabetic or alcholic ketoacidosis:-Non anion gap MA(ketoacidosis),Metabolic alkalosis(vomiting and hypovolemia) and compensatory Resp alkalosis...

And there is Winter's formula IN MIXED DISORDERS

which is : expected pCO2=1.5 HCO3-+8,or pco2=HCO3-+15.can be used to calculate pco2 in the setting of metabolic acidosis.
if measured pco2>expected pco2,means concomitant resp acidosis exists..
if measured pco2

[ArchivalUser]

if measured pco2

[ArchivalUser]

this page is messed up man..i m writing and over and over again and its still not displaying!!