Transcript دكتر مديحي

[H+]
=(3.98x10-8) ~ 40nEq/lit
pH
=-log[H+]
=-log( 3.98x10-8)
=-(0.60-8.0)
7.4
Acid
donates
hydrogen
ion
Base
accepts
hydrogen
ion
HA
+
[H ].[A ]
+
[H ].[A ]
HA
[H+]=[ HA]/ [ A-]
[H+]=k[ HA]/ [ A-]
-log[H+]=-logk[ HA]/ [ A-]
-log[H+]=-logk+log [ A-]/[ HA]
pH=pk+log [ A-]/[ HA]
H2O + CO2  H2CO3  H+ + HCO3-
pH=pk+log [HCO3-]/[H2CO3]
pH=6.1+log [HCO3-]/[H2CO3]
[
[H+]=24 [PCO2] / [HCO3-]
Non-bicarbonate buffers:
Protein
Phosphate
Bone
...
Kidneys:
Resorb
HCO3-
Buffers
Secretion of
hydrogen ions
H2O + CO2  H2CO3  H+ + HCO3-
H2 po41phatPhose:
po43-
H po42H2 po41H3 po4
[H+] [ H po42- ]
[NH3] [H+]
[ NH4+]
pH
[H+]
PCO2
Partial
pressure CO2
PO2
Partial
pressure O2
HCO3
Bicarbonate
BE
Base excess
SaO2
Case Study




A 4-year-old girl was admitted to the emergency
room because of poor intake, vomiting, fever and
abdominal pain over the last 3 days.
Mother denied any history of drug ingestion.
Past medical history is significant for recurrent
urinary tract infections.
The BP was 90/57 mmHg, PR 90/min, and
respirations 32/min
Case Study (cont’d)


Laboratory data on admission revealed a serum Na+
of 135 mEq/, K + 6.2 mEq/L, Cl- 117 mEq/L, HCO310 mEq/L, BUN 23 mg/dL, creatinine
0.4mg/dL,glucose 100 mg/dL, calcium 9.2 mg/dL,
phosphorous 4.0 mg/dL, uric acid 4.8 mg/dL.
Arterial blood pH was 7.10, and pCO2 28 mmHg.
Case Study (cont’d)



Urinalysis showed a pH of 6.5, negative for
blood or protein.
The urine sediment was normal.
Urine Cl- was 52, Na+ 68, and K+ 25.
Quiz



What acid-base is present?
What is the most likely diagnosis?
What investigation would establish the
diagnosis?
Step 1
What is the primary acid-base
disturbance?

Metabolic acidosis is the primary acid-base
disorder:
- Low blood pH (7.10)
- Low HCO3- level (10 mEq/L)
Step 2
Is the metabolic acidosis associated
with a normal or an increased anion
gap?
AG = Na+ - (Cl- + HCO3-)
Patient has a normal AG acidosis

Serum AG = (135) - [(117+16)]
= (135) - (133)

= 12 mEq/L
The fall in serum HCO3- level in this patient is
matched by an equal rise in the serum Clconcentration, thus the patient has normal anion
gap acidosis
Causes of normal AG acidosis






GI bicarbonate loss
Use of carbonic anhydrase
Hyperalimentation
Ureteral diversions
NH4Cl infusions
Renal tubular acidosis (RTA)
Step 3
Is the respiratory compensation
adequate?





pCO2 = 1.2 HCO3pCO2 = 1.2 (25-10) or 18 mmHg
Expected pCO2 = (40-18) = 22 mmHg
Patient’s pCO2 = 28 mmHg
Patient’s pCO2 > the expected pCO2
Respiratory Acidosis
Our patient has a mixed acid-base
disorder
Normal AG metabolic acidosis
plus
Respiratory acidosis
The urine AG
Urine AG = (UC +) - (UA-)
Urine Cl- > Urine (Na+ + K+)
The usefulness of the urine AG in the
evaluation of distal RTA


A negative urine AG suggests the presence of a
normal distal urinary acidification
A positive urine AG (Na+ + K +) > Cl- suggests the
presence of impaired distal urinary acidification
Urine AG as an index of NH4excretion



NH4+ is an unmeasured cation and its excretion at the
distal tubule is usually accompanied by Cl- excretion
(NH4Cl)
The urinary AG should become progressively negative
as the rate of NH4Cl excretion increases
Under normal condition the urine AG is negative
Classification of RTA



Classic distal RTA (RTA-1)
Proximal RTA (RTA-2)
Hyperkalemic distal RTA (RTA-IV)
Quiz
What is the most likely diagnosis?
The most likely diagnosis is RTA-IV
1. Normal AG acidosis
2. Hyperkalemia
3. Urine pH >5.5
4. Positive urine AG
Quiz
What is the most likely cause of RTA-IV?
 A. Acute non-obstructive pyelonephritis
 B. Acute pyelonephritis with VUR
 C. Addison disease
 D. Non-obstructive pyelonephritis
B. Pyelonephritis with VUR
Quiz
What investigations you order to confirm this
diagnosis?
 A. Renal sonogram
 B. Urine β2 microglobulin
 C. DMSA scan
 D. VCUG
 E. DTPA scan
A. Renal sonogram
Our patient has a positive urine AG
Urine


+
(Na
+
+
UK )
> Urine
Cl
Urine AG = [(Na+ + K+ )] - (Cl-)
= [(68 + 25)] -(52)
= (93) - (52)
= 41 mEq/L
The positive urine AG is consistent with the
impaired distal urinary acidification
Differential diagnosis of impaired
distal renal acidification


Classic distal RTA (RTA-I)
Hyperkalemic distal RTA (RTA-IV)
Characteristics of RTA





RTA-1
Urine pH >5.5
Severe hypokalemia
Low urine citrate exc
Nephrocalcinosis
Urolithiasis




RTA-IV
Urine pH varies
hyperkalemia
Normal urine citrate
Decreased renin and
aldosterone secretion
Causes of classic distal RTA (RTA-I)






Idiopathic
Familial
Hypercalciuria
Amphotricin B
Chronic active hepatitis
Medullary sponge kidney
Causes of hyperkalemic
distal RTA (RTA-IV)






Urinary tract obstruction
Vesicoureteral reflux
Interstitial nephritis
Systemic lupus erythematosis
Diabetes mellitus
Primary hypoaldosteronism
Case Study


A 12-year-old girl was admitted to the emergency
department in a semi-comatose condition. Blood
pressure was 110/65 mmHg; pulse 87/min; and
respiratory rate 22/min. The remainder of the PE
was normal.
Laboratory data on admission revealed serum Na+
of 135 mEq/, K + 2.1 mEq/L, Cl- 117 mEq/L,
HCO3- 10 mEq/L, BUN 13 mg/dL, creatinine 0.4
mg/dL, and glucose 90 mg/dL.
Case study (cont’d)


Arterial blood pH was 7.10, and PCO2 33 mmHg.
Urinalysis showed a pH of 7.0. The urine sediment
was normal
The patient was intubated and potassium was
given intravenously.
Quiz



What acid-base disorder is present?
What is the most likely diagnosis?
What investigation would establish the diagnosis?
Step 1: Review ABG data
What is the primary acid-base disturbance?
 Blood pH =7.10
 HCO3 = 10 mEq/L
 PCO2 = 33 mmHg
The findings of low HCO3- and low pH suggest a
primary metabolic acidosis
Step 3: Review serum
electrolytes?
Is the metabolic acidosis associated with a normal
or an increased anion gap?
 Serum AG = (135) - [(117+16)]
 patient has normal AG acidosis
 = (135) - (133)
Normal AG =12 mEq/L
Step 2: Assess respiratory
compensation
Is the respiratory compensation adequate?
 Patient’s PCO2 = 33 mmHg
∆PCO2 = 1.2 ∆HCO3 ∆PCO2 = 1.2 (25-10) or 18 mmHg
 Expected PCO2 = (40-18) = 22 mmHg
Patient’s PCO2> the expected pCO2
Quiz
What is the acid-base diagnosis?
a - Metabolic acidosis
b - Respiratory acidosis
c - Metabolic acidosis and respiratory acidosis
d - Metabolic acidosis and respiratory alkalosis
c - Metabolic acidosis and respiratory
acidosis
Quiz
What is the most likely diagnosis?
a - Distal RTA (RTA-1)
b - Proximal RTA (RTA-2)
c - Distal RTA (RTA-4)
d - Cystinosis
a - Distal RTA (RTA-1)
Quiz
How would you confirm the diagnosis?
a - kidney ultrasound
b - Measure urinary anion gap
c - Measure urine ammonia level
d - Measure urine phosphorous level
a - Kidney ultrasound
b - Measure urine anion gap
Case Study

You are asked to see a 10-month-old boy found to be
stuporous at home. On examination he appears well
developed, his weight is 9.6 kg, height 73 cm,
temperature is 37° C, BP 87/55 mmHg, pulse 98
beats/min, respiratory rate 38/min. Several
ecchymoses are present over his trunk and limbs. The
remaining of PE is unremarkable.
Case Study (cont’d)

Laboratory data reveals srum sodium 140 mEq/L,
potassium 3.8 mEq/L, chloride 108 mEq/L,
bicarbonate 13 mEq/L, BUN 14 mg/dL, creatinine 0.5
mg/dL, ketones 2+, arterial pH 7.34 and PCO2 20
mmHg
Quiz


What is the acid-base diagnosis?
What is the likely diagnosis?
Step 1: Review ABG data



arterial pH 7.34
PCO2 20 mmHg
bicarbonate 13 mEq/L
The pH and HCO3- are both decreased witch
suggest a primary metabolic acidosis
Step 2: Review serum
electrolytes

Is the metabolic acidosis associated with
a normal or an increased anion gap?
What is the AG?




Patient has large AG acidosis
AG = Na+ - (Cl- + HCO3-)
AG = (140) – (108 + 13)
AG = 19 mEq/L
Step 3: Assess respiratory
compensation
Is the respiratory compensation
adequate?
 Patient’s PCO2 = 20 mmHg
∆PCO2 = 1.2 ∆HCO3 ∆PCO2 = 1.2 (25-13) or 14.4 mmHg
 Expected PCO2 = (40-14.4) = 25.6 mmHg
Patient’s PCO2< the expected PCO2
Quiz
What is the acid-base diagnosis?
a - Metabolic Acidosis
b - Metabolic acidosis and respiratory
acidosis
c - Metabolic acidosis and respiratory
alkalosis
d - Metabolic acidosis and metabolic
alkalosis
c – Metabolic acidosis and respiratory
alkalosis
Quiz
What is the most likely diagnosis?
a - Sepsis
b - Salicylate toxicity
c - Lactic acidosis associated with liver failure
d - Liver failure
e - Ethanol toxicity
b - Salicylate toxicity
(presence of ecchymoses)
Case Study


A 9-month-old girl was admitted with a 2-week
history of lethargy and weight loss despite having
solids. She was born at 38 Weeks's gestation with a
birth weight 3.2 Kg. There was no neonatal problems.
On examination she was aferible, 10% dehydrated.
BP was 78/45 mmHg, height 62 cm (75%), weight
5.9 kg (<5%).
Case Study (cont’d)

Urine and blood cultures were negative The Hb was
11.2 g/dL with normal electrophoresis. Blood pH was
7.55, PCO2 53 mmHg, Na+ 130 mEq/L, CL- 87
mEq/L, k+ 2.9 mEq/L, HCO3- 30, BUN 22 mg/dL,
creatinine 0.3 mg/dL. Urine electrolyte levels were
Na+ 19 mEq/L, K+ 7 mEq/L and Cl- 5 mEq/L.
Quiz



What acid-base disorder is present?
What is the most likely diagnosis?
What investigation would establish the
diagnosis?
Step 1: Review the ABG data



Arterial pH 7.55
HCO3- 30
PCO2 53 mmHg
Since the pH and HCO3- are both elevated,
the primary acid-base is likely to be
metabolic alkalosis
Step 2: Review serum
electrolytes

Is the metabolic acidosis associated with
a normal or an increased anion gap?
What is the AG?




Patient has normal AG acidosis
AG = Na+ - (Cl- + HCO3-)
AG = (130) – (87 + 30)
AG = 13 mEq/L
Step 3: Assess respiratory compensation
Is the respiratory compensation adequate?
 Patient’s PCO2 = 53 mmHg
∆PCO2 = 0.6 ∆HCO3 ∆PCO2 = 0.6 (30-25) or 3.0 mmHg
 Expected PCO2 = (40+3.0) = 43.0 mmHg
Patient’s PCO2 >the expected PCO2
Quiz
What is the patient’s acid-base
diagnosis?
a - Metabolic alkalosis and respiratory
acidosis
b - Metabolic alkalosis and respiratory
alkalosis
c - Metabolic alkalosis
d - Respiratory alkalosis
a - Metabolic alkalosis and respiratory
acidosis
Diagnostic approach to metabolic alkalosis
Urine Cl- < 15 mEq/L
 Persistent vomiting
 CFP
 Use of diuretics
 Decreased effective
arterial blood volume
due to CHF, NS,
cirrhosis
Urine Cl- > 20 mEq/L
 Bartter’s syndrome
 Hyperaldosteronism
 Liddle’s syndrome
 Gittleman’s syndrome
Quiz
What is the most likely diagnosis?
a - CFP
b - Bartter syndrome
c - Liddle syndrome
d - Gitelman syndrome
a - CFP
Quiz
How would you confirm this diagnosis?


The sweat test provides the definitive diagnostic
test for cystic fibrosis
Result of a sweat test in this child, revealed Na+ 99
mEq/L and sweat Cl- 119 mEq/L, confirming the
diagnosis of cystic fibrosis
Quiz
How would you confirm this diagnosis?


The sweat test provides the definitive diagnostic
test for cystic fibrosis
Result of a sweat test in this child, revealed Na+ 99
mEq/L and sweat Cl- 119 mEq/L, confirming the
diagnosis of cystic fibrosis
Quiz
What do you estimate his urine pH to be?
 Acid <5.5
 Alkaline >6.0
 Alkaline >6.0



(urine Na + K) - urine Cl
(90 + 35) – 65 = 60
Urine AG is positive
Quiz
Would you like to draw a blood gas?
 Yes, I believe one is indicated
 No, I don not believe it is necessary
No, I do not believe it is necessary
Case study




A 15-year-old male was admitted to emergency
room because of altered CNS status
Blood pressure was 120/80 mmHg, pluse 80 bpm,
and respiratory rate 24/min.
Breathing sounds were diminised with diffuse
rales bilaterally
The abdoman is soft without masses or
organomegaly
Quiz
What do you estimate his arterial pH and pCO2
to be?
 7.20 and 25 mmHg
 7.25 and 30 mmHg
 7.30 and 35 mmHg
 7.35 and 28 mmHg
 7.40 and 30 mmHg
7.35 and 28 mmHg
Comments
PCO2 = 1.2 HCO3

PCO2 = 1.2 (25-15)

PCO2 = 12
 Patient’s PCO2 = (40-12)
Patient’s PCO2 = 28 mmHg

Comments







H = 24 Pco2/HCO3
H = 24 (28)/15
Patient H = 44.8 or 45 nEq/L
Normal pH 7.40 = H 40 mEq/L
10 H = 10 pH
Patient’s H 45
Patient’s pH = 7.35
Case study (cont’d)


Laboratory data showed a serum Na 144
mEq/L, K 3.5, Cl 100, HCO3 15 (mEq/L).
BUN was 33, Cr 1.0, glucose 180 (mg/dL).
Serum ketones was +1 positive and serum
osmolality was 330 mosm/Kg
Arterial pH was 7.30, pCO2 25 mmHg.
Urinalysis was negative with a pH 5.0 and SG
1.020.
Quiz



What acid-base is present?
What is the most likely diagnosis?
What investigation would establish the
diagnosis?
Quiz
What is the most likely acid-base diagnosis?

A. Metabolic acidosis and metabolic alkalosis plus
respiratory acidosis

B. Metabolic acidosis and metabolic alkalosis

C. Mixed metabolic acidosis plus respiratory alkalosis

D. Mixed metabolic acidosis and metabolic alkalosis
plus respiratory acidosis
D. Metabolic acidosis and metabolic alkalosis
plus respiratory alkalosis
Quiz
Given the clinical setting, what is the most likely
diagnosis?
 A. Toxic ingestion (methanol or ethylene glycol)
 B. Lactic acidosis
 C. Starvation ketoacidosis
 D. Ethanol ketoacidosis
D. Ethanol intoxication
Step 1
What is the primary acid-base
disturbance?
Low pH (7.30)
Low PCO2 (25)
Low HCO3 (15)
Primary Metabolic Acidosis
Step 2
Is the metabolic acidosis associated
with a normal or an increased anion
gap?
AG = Na+ - (Cl- + HCO3-)
AG= 144 – (100 + 15)
AG = 29 mEq/L
Large AG Metabolic Acidosis
The ionic anatomy of serum (mEq/L)
155
(Cations) = (Anions)
135
Unmeasured Anio = 23
125
Unmeasured Cation = 11
105
85
Cl- 103
Na+ 140
(140) - (103 + 25) = 12 mEq/L
65
Normal AG = 12 + 4
45
25
HCO3- 25
15
Pr- 15
5
0
AG = 23-11 = 12 mEq/L
K+ 4.5
Ca+ + 5.0
Mg++ 1.5
151 mEq
OA- 4
HPO4- - 2
SO4 - - 2
151 mEq
Metabolic Acidosis
Cl103
Na+
140
HCO325
A12
NORMAL
Cl103
Cl113
Na+
140
HCO315
A12
NORMAL AG
ACIDOSIS
HCO315
Na+
140
A22
LARGE AG
ACIDOSIS
Step 3
Is the respiratory compensation
adequate?





pCO2 = 1.2
HCO3pCO2 = 1.2 (25-15) or 12 mmHg
Expected pCO2 = (40-12) = 28 mmHg
Patient’s pCO2 = 25 mmHg
Patient’s pCO2 < the expected pCO2
Respiratory alkalosis
This patient has a mixed acid-base
disorder
Large AG metabolic acidosis
plus
Respiratory alkalosis
Step 4
Determine the presence of any
concurrent metabolic alkalosis?
HCO3- / AG = 1


As a rule, with metabolic acidosis of the large AG,
there should be a 1:1 correspondence between
decreasing serum HCO3- and increasing AG
Whenever the AG is elevated but serum HCO3 is
not reduced reciprocally, a mixed metabolic
acidosis and alkalosis coexist.
This patient’s serum HCO3 is
reduced by 10 mEq/L(from
25 to 15) however but his AG
rose by 17 mEq/L(from 12 to
29). The rise in the AG is>the
fall in HCO3
Cl94
Cl103
Na++
140
Na++
140
HCO3-
HCO3- /AG> 1
Thus, this patient has mixed
large AG metabolic acidosis
and metabolic alkalosis plus
respiratory alkalosis.
HCO315
19
A-
A22
PURE HIGH AG
ACIDOSIS
Patient
27
MIXED HIGH AG ACIDOSIS
& METABOLIC ALKALOSIS
Causes of large AG acidosis





Renal failure
Ketoacidosis: (diabetes mellitus, hypoglycemia)
Lactic acidosis: (liver failure, sepsis, shock)
Drugs and poisons: (salicylate, paraldehyde, Ethanol,
methanol, ethylene glycol)
Inborn errors of metabolism
Step 5
Compare measured and calculated
plasma osmolaity (POSM)


Calculated POSM = 2 Na (mEq/L) + 10
Patient’s calculate POSM = (2 x 140) + 10 = 290
Patient’s measured osmolality = 330
Under normal condition, the estimated serum
osmolality must not exceed the measured osmolality by
more than 10 mosm/kg
Patient has a large osmolal gap of 40 mosm/kg

What is the most likely diagnosis?
Ethanol intoxication


The patient had no oxalate crystals in the
urine as found in the ethylene glycol
intoxication
There was no evidence of optic papillitis on
foundoscopic examination as might be
anticipated in a patient with methanol
intoxication
Case study


A-4 month-old girl was admitted with a 2week history of lethargy and weight loss
despite having solids.
She was born at 38 weeks gestation with a
birth weight 3.2 Kg. There was no neonatal
problems.
Case study (cont’d)

On examination she was aferible, 10%
dehydrated. BP was 78/45 mmHg, height 62
cm (75%), weight 4.1 kg (<5%). There was no
sign of dehydration
Case study (cont’d)

Urine and blood cultures were negative as
was examination of the stools for adeno and
rotaviruses. The hemoglobin was 11.2 g/dl
with normal electrophoresis. Blood pH was
7.55, pCO2 43 mmHg, Na+ 130 mEq/L, CL87 mEq/L, k+ 2.9 mEq/L, HCO3- 35, BUN
22 mg/dL, creatinine 0.8 mg/dL. Urine
electrolyte levels were Na+ 19 mEq/L, K+ 7
mEq/L and Cl- 5 mEq/L.
Quiz



What acid-base is present?
What is the most likely diagnosis?
What investigation would establish the
diagnosis?
Step 1
What is the primary acid-base disorder?


Metabolic alkalosis
Increased plasma pH (7.55)
Increased plasma HCO3 (32 mEq/L)
Step 2
Is the respiratory compensation
adequate?




pCO2 = 0.6 HCO3- or
= 0.6 (35-25) = 6 mEq/L
Expected pCO2 = (40 + 6) or 46 mmHg
Patient’s pCO2 = 43
Patient’s pCO2 < the expected pCO2
Patient has a mixed acidbase disorder


Metabolic alkalosis plus
Respiratory alkalosis
Approach to Metbolic Alkalosis
Urine Cl- < 15 mEq/L
 Persistent vomiting
 CFP
 Use of diuretics
 Decreased effective
arterial blood volume
due to CHF, NS,
cirrhosis
Urine Cl- > 20 mEq/L
 Bartter’s syndrome
 Hyperaldosteronism
 Liddle’s syndrome
 Gittleman’s syndrome
Diagnostic algorithm for metabolic alkalosis
Hypokalemia
Metabolic Alkalosis
Arterial pH>7.45
↑ Plasma HCO3-
Evaluate Respiratory
Compensation
∆ PCO2=0.6 ∆ HCO3-
Measure
Urine Cl- excretion
Check
Blood Pressure
Cl- <15 mEq/L
Normal Blood Pressure
Cl- depletion
Surreptitious vomiting
Post diuretic
CFP
Cl- >15 mEq/L
Measure
PRA, PAC
Normal
Blood Pressure
Bartter and Gitelman
Syndromes
(↑PRA, ↑PAC)
Elevated
Blood Pressure
Primary aldosteronism
(↓PRA, ↑PAC)
Liddle syndrome
Normal
PRA and PAC
Levels
AME (↓PRA, ↓PAC)
Licorice ingestion
RVH
(↑PRA, ↑PAC)
Quiz
What is the most likely
diagnosis?

The finding of hypochloremic metabolic
alkalosis associated with low urine Cl- level
(5 mEq/L) in the absence of vomiting or
diuretic use is most consistent with the
diagnosis of cystic fibrosis
Quiz
How would you treat?


Adminstration of saline with KCl to correct
the ECF volume contraction
Avoid K+ sparing diuretics
What investigation would establish
the diagnosis?

At present, the pilocarpine iontophoresis
sweat test provides the definitive test for
cystic fibrosis
In this child, a sweat testNa+of 99 mEq/L
and sweat Cl- of 139 mEq/L, confirmed the
presence of cystic fibrosis
Any
Questions?
THANKS