USMLE Forum Archives - USMLE Step 3 - ELECTROLYTES: Next Best Step Facts
ELECTROLYTES: Next Best Step Facts
harry206 - 05-09-09 02:43
Metabolic Acidosis ------>Next step -----> Anion Gap---->
(a) Anion Gap + ------> Next step -----> Osmolal gap (> 20 signifies alcohol ingestion)
(b) Non Anion Gap ------> Next step -----> Urine anion gap [+ signifies RTA, - signifies GI loss]
Metabolic Alkalosis -------> next step----> Urine Cl----->
(a) Urine Cl <20 ----->signifies ECF contraction------> Treat with N/S
(b) Urine Cl >20 ------>next step -----> BP---->
- High BP---> hyperaldosteronism
- Normal BP----> Barters, giettelmen syndrome
Osmolal Gap=
Observerd Osm -Calculated OSm
(Calculated OSm = 2 Na + Glu/18 +BUN/2.8)
Urine Anion Gap = (UNa + UK)- UCl
(normal= 0 to -50)
Renal Tubular Acidosis (RTA) ------> next step -----> K+---->
(a) K high ------> RTA type 4
(b) K low/Normal -------> Next step ------> Urine PH ----->
- PH < 5.5. ----> proximal RTA
- PH > 5.5 -----> Distal RTA
To check for Respiratory compesation:
Winter Formula used: 1.5(HCo3) + 8 = expected pCo2
(a) If Present Pco2> expected pCo2 ----> concomitant respi acidosis
(b) If Present Pco2< expected pCo2 ----> concomitant respi alkalosis
To check for Metabolic compesation:
(Calculated Anion Gap -12) + measured HCo3 = x
(a) If x >26 ----> concomitant metab alkalosis
(b) If x <26 ----> concomitant metab acidosis
harry206 - 05-09-09 02:43
Metabolic Acidosis ------>Next step -----> Anion Gap---->
(a) Anion Gap + ------> Next step -----> Osmolal gap (> 20 signifies alcohol ingestion)
(b) Non Anion Gap ------> Next step -----> Urine anion gap [+ signifies RTA, - signifies GI loss]
Metabolic Alkalosis -------> next step----> Urine Cl----->
(a) Urine Cl <20 ----->signifies ECF contraction------> Treat with N/S
(b) Urine Cl >20 ------>next step -----> BP---->
- High BP---> hyperaldosteronism
- Normal BP----> Barters, giettelmen syndrome
Osmolal Gap=
Observerd Osm -Calculated OSm
(Calculated OSm = 2 Na + Glu/18 +BUN/2.8)
Urine Anion Gap = (UNa + UK)- UCl
(normal= 0 to -50)
Renal Tubular Acidosis (RTA) ------> next step -----> K+---->
(a) K high ------> RTA type 4
(b) K low/Normal -------> Next step ------> Urine PH ----->
- PH < 5.5. ----> proximal RTA
- PH > 5.5 -----> Distal RTA
To check for Respiratory compesation:
Winter Formula used: 1.5(HCo3) + 8 = expected pCo2
(a) If Present Pco2> expected pCo2 ----> concomitant respi acidosis
(b) If Present Pco2< expected pCo2 ----> concomitant respi alkalosis
To check for Metabolic compesation:
(Calculated Anion Gap -12) + measured HCo3 = x
(a) If x >26 ----> concomitant metab alkalosis
(b) If x <26 ----> concomitant metab acidosis
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#1
Re: ELECTROLYTES: Next Best Step Facts usmlefever3 - 05-09-09 02:46 very nice compilation of important information
#2
Re: ELECTROLYTES: Next Best Step Facts
harry206 - 05-09-09 02:47 Thanks usmlefever
Plz add more info on this topic or
correct me if wrong
GL
#3
Re: ELECTROLYTES: Next Best Step Facts harry206 - 05-09-09 02:50 Other HY FActs:
Hypokalemia and Metabolic alkalosis ------->
Bartter, Gitelman & Liddle's syndrome
Bartter & Gitelman -----> Normal/dec BP
Liddle's ---------> Inc BP
Bartter ------> Normal Mg
Gitelman ------> dec Mg
Treatment:
Bartter: Inc salt diet, Inc K, NSAIDS
Gitelman: Inc K, Inc Mg, Amiloride
Liddle's :Amiloride
#4
Re: ELECTROLYTES: Next Best Step Facts usmlefever3 - 05-09-09 03:13 regarding metabolic alkalosis
increased urinary chloride - diuretics- saline responsive
#5
Re: ELECTROLYTES: Next Best Step Facts usmlefever3 - 05-09-09 03:18 regarding RTA
type 1 RTA - nephrocalcinosis because hypercalcuria and low citrate levels
type 2 RTA - fanconis synd and no nephrocalcinosis because citrate are high in urine
type 4 RTA - associated with DM
#6
Re: ELECTROLYTES: Next Best Step Facts harry206 - 05-09-09 03:19 Hi Usmlefever,
If Pt with Metabolic alkalosis have Urine Cl > 20 (this suggest ECF expansion and HTN) ---> these Pt can't be corrected with NS
(Very Imp HY Fact)
That is why next step after diagnosing Metabolic Alkalosis is checking Urine Cl
(Urine Cl< 10 suggest ECF contraction ---> responsive to NS)
#7
Re: ELECTROLYTES: Next Best Step Facts usmlefever3 - 05-09-09 03:32 
posted by harry206 on 05-09-09 02:50
Other HY FActs:
Hypokalemia and Metabolic alkalosis ------->
Bartter, Gitelman & Liddle's syndrome
Bartter & Gitelman -----> Normal/dec BP
Liddle's ---------> Inc BP
Bartter ------> Normal Mg
Gitelman ------> dec Mg
Treatment:
Bartter: Inc salt diet, Inc K, NSAIDS
Gitelman: Inc K, Inc Mg, Amiloride
Liddle's :Amiloride
Other HY FActs:
Hypokalemia and Metabolic alkalosis ------->
Bartter, Gitelman & Liddle's syndrome
Bartter & Gitelman -----> Normal/dec BP
Liddle's ---------> Inc BP
Bartter ------> Normal Mg
Gitelman ------> dec Mg
Treatment:
Bartter: Inc salt diet, Inc K, NSAIDS
Gitelman: Inc K, Inc Mg, Amiloride
Liddle's :Amiloride
to ADD to this pathogenesis of these :
bartter - mutation in Na K Cl co transport and ROMK K+ channel
gittelman-mutation in thiazide channel
liddle- mutation amiloride sensitive Na channel
#8
Re: ELECTROLYTES: Next Best Step Facts usmlefever3 - 05-09-09 03:36 posted by harry206 on 05-09-09 03:19
Hi Usmlefever,
If Pt with Metabolic alkalosis have Urine Cl > 20 (this suggest ECF expansion and HTN) ---> these Pt can't be corrected with NS
(Very Imp HY Fact)
That is why next step after diagnosing Metabolic Alkalosis is checking Urine Cl
(Urine Cl< 10 suggest ECF contraction ---> responsive to NS)
Hi Usmlefever,
If Pt with Metabolic alkalosis have Urine Cl > 20 (this suggest ECF expansion and HTN) ---> these Pt can't be corrected with NS
(Very Imp HY Fact)
That is why next step after diagnosing Metabolic Alkalosis is checking Urine Cl
(Urine Cl< 10 suggest ECF contraction ---> responsive to NS)
you are right but i have known that in case of diuretics urine chloride is high and still it is saline responsive
#9
Re: ELECTROLYTES: Next Best Step Facts harry206 - 05-09-09 03:40 But in Diuretics use: Urine Cl is < 20 ---> so it is responsive to NS
Thnx for ur other facts
GL
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