Electrolytes and Acid Base with Suneel Udani 4.11.11

Electrolyte and Acid Acid-Base Base 

Board B BBoard dR Review i 

Suneel M Udani MD MPH 

4/11/2011 

/ / 0

Question Question 1 

1 

A 64 64-year year-old old man comes for a routine physical examination. 

During the past year, his urine output has increased and he urinates 

approximately approximately pp y two to three times nightly. g y 

He does not have daytime urinary frequency, urinary hesitancy, or a 

decreased dec eased urinary a y stream. st ea . He also a so has as had ad increased c eased thirst t st and a d 

has been drinking more water than usual. His weight has been 

stable. 

He has bipolar disorder that was treated with lithium for 20 years; 

10 years ago, he was switched to divalproex sodium. His brother 

has sickle cell trait.

Physical Exam 

Afebrile 

BP 148/78 HR 78 RR 18 BMI 20 

The remainder of the physical 

examination is normal. 

On abdominal ultrasound, the right 

kidney is 8.6 cm and the left kidney 

i is 93 9.3 cm. There Th is i no 

hydronephrosis 

Question Question 1 1 (cont) 

(cont) 

146 107 34 

3.6 26 2.1 


(cont) 

Which of of the the following following is the most most likely 

likely 

diagnosis? 

A) Diabetic nephropathy 

B) Lithium-induced nephrotoxicity 

C) Obstructive uropathy 

D) ) Sickle cell nephropathy p p y


(cont) 

Which of the following is the most likely 

diagnosis? 

A) Diabetic nephropathy 

B) Lithium-induced nephrotoxicity 

C) Obstructive uropathy 

D) ) Sickle cell nephropathy p p y

Hypernatremia 

Hypernatremia must always result from a defect in 

sensation of thirst or access to water 

Categorization of hypernatremia depends on 

ADH ADH-renal l response to a state of f hyper- h 

osmolality

Na > 145 mmol/L 

Clinical Approach to 

Urine Osm< 

700 mOsm/L 

Urine Osm> 

700 mOsm/L 

Hypernatremia 

Give 

DDAVP 4 

mcg IV X 1 

Renal loss of H20 inadequate + water 

intake 

Extra-renal H 20 loss, inadequate water 

intake + osmotic diuresis (glucose, 

mannitol) 

Renal 

function 

normal or 

near normal 

Renal 

function 

severely 

abnormal 

b l 

Urine 

osmolality 

unchanged 

Urine osmolality 

corrects to > 1000 

msOsm 

Nephrogenic DI 

Central DI 

Renal Tubular Damage 

(impaired H 20 handling)

Physical Exam 

Afebrile 

BP 148/78 HR 78 RR 18 BMI 20 

The remainder of the physical 


On abdominal ultrasound, the right 

kidney is 8.6 cm and the left kidney 

i is 93 9.3 cm. There Th is i no 

hydronephrosis 


(cont) 

146 107 34 

3.6 26 2.1 


2 

A A32 A32-year A 32 year-old year old man man is brought to to the the emergency 

emergency 

department after becoming disoriented, 

combative combative, and and agitated agitated earlier earlier that that day. day 

H He i is accompanied i d b by a f friend, i d who h states that h 

the patient has a history of alcohol and drug 

abuse, b i including l di i inhalants. 

h l

Physical Exam 

Exam 

Uncooperative and 

slightly g y disoriented. 

Question 2 2 (cont) 

(cont) 

142 109 18 

4.1 23 1.1 


(cont) 


likely 

diagnosis? 

A) Alcoholic ketoacidosis 

B) Diabetic ketoacidosis 

C) Ethylene glycol ingestions 

D) ) Isopropyl p py alcohol ingestion g 

E) Toluene ingestion


(cont) 


likely 

diagnosis? 

A) Alcoholic ketoacidosis 

B) Diabetic ketoacidosis 

C) Ethylene glycol ingestions 

D) ) Isopropyl p py alcohol ingestion g 

E) Toluene ingestion

Alcoholic 

Ketoacidosis 

Diabetic 

Ketoacidosis 

Ethylene Glycol 

ingestion 

Isopropyl p py Alcohol 

ingestion 

Toluene ingestion 


2 

Osmolal Gap Metabolic Acidosis Elevated Anion Gap

Alcoholic 

Ketoacidosis 


2 

Osmolal Gap Metabolic Acidosis Elevated Anion Gap 

Normal 

(must correct for 

ETOH in calculated 

osmoles) 

Diabetic Normal 

Ketoacidosis 


↑↑ 

ingestion g (> 10 mosm/kg) 

Isopropyl Alcohol 

ingestion 

↑↑ 

(> 10 mosm/kg) 

Toluene ingestion Normal

Alcoholic 

Normal 

Ketoacidosis (must correct for 


osmoles) 


Ketoacidosis 


↑↑ 



ingestion 


2 


↑↑ 


Toluene ingestion Normal 

+ 

++ 

++ 

-- 

++

Alcoholic 

Normal 

Ketoacidosis (must correct for 


osmoles) 



2 


+ + 

Ketoacidosis ++ ++ 


↑↑ 



ingestion 

↑↑ 


Toluene ingestion Normal 

++ ++ 

-- -- 

++ --

Question 2

Physical Exam 

Exam 

Uncooperative and 

slightly g y disoriented. 


(cont) 

142 109 18 

4.1 23 1.1 


3 

65 y/o gentleman evaluated for 135 105 22 

3-month history of progressive 

malaise, fatigue, weakness. 

He has 10-year history of 

hypertension. 

Meds 

HCTZ 

Atenolol 

Exam WNL 

3.0 18 1.8 

> 8.5 8 5 < < 340 

340 

7.33/28/102


3 


likely 

diagnosis? 

A. Diabetic nephropathy 

B. Distal (type I) renal tubular acidosis 

C. Hypertensive yp nephrosclerosis 

p 

D. Proximal (type 2) renal tubular acidosis


3 


likely 

diagnosis? 

A. Diabetic nephropathy 

B. Distal (type I) renal tubular acidosis 

C. Hypertensive yp nephrosclerosis 

p 

D. D. Proximal Proximal (type (type 2) 2) renal renal tubular tubular acidosis acidosis

Renal Tubular Tubular Acidosis 

How How does does the the kidney kidney maintain maintain acid acid-base base base balance? 

balance? 

1. R Reclaim l i filtered fil d bicarbonate bi b 

Proximal (type II) RTA 

2. Distal acidification 

Distal (type I) RTA 

Type yp 

IV RTA


Reclamation of Filtered 

HCO - 

3 

Requires luminal luminal carbonic 

carbonic 

anhydrase 

P Proximal i l RTA RTA manifests if 

with other proximal tubule 

wasting 

Hypokalemia 

Hypophosphatemia 

Bicarbonaturia

Distal Acidification 


Alpha Alpha-intercalated intercalated cell 

Acid Aid Acid secretion ti requires i buffering bff i 

Acid excreted as titratable acid 

Acid excreted as Ammonium 

(NH + (NH + 

4 ) 

Type I (traditional “Distal RTA”) 

hypokalemic hypokalemic and severe acidosis 

Type IV IV—”Hyperkalemic ”Hyperkalemic RTA”

Diagnosis of of RTA 

RTA 

Assessment of bicarbonaturia, ,p proximal tubular wasting g 

and/or distal acidification 

Urine pH 

Fractional excretion of Bicarbonate, phosphorus and 

TTKG 

Urinary y Anion Gap p ([Na] ([ ] urine urine urine urine + [K] [ ] urine urine) urine urine) – [Cl] [ ] urine 

In setting of acidosis [Cl] urine > ([Na] urine + [K] urine 

Indirect measurement of urine NH + 

4 

urine)

Clues to to proximal proximal vs vs distal distal RTA 

RTA 

Proximal (type (yp II) ) 

Distal (type (yp I) ) 

Concomitant proximal 

tubular bl d dysfunction f i (i.e. (i 

Fanconi’s syndrome) 

Very high bicarbonate 

requirements 

Urine pH low in steady 

state 

Severe hypokalemia 

Urine pH not maximally 

acidified 

History y of recurrent 

stones, bone disease


3 

65 y/o gentleman evaluated for 135 105 22 

3-month history of progressive 

malaise, fatigue, weakness. 

He has 10-year history of 

hypertension. 

Meds 

HCTZ 

Atenolol 

Exam WNL 

3.0 18 1.8 

> 8.5 8 5 < < 340 

340 

7.33/28/102


4 

A 44 44-year year-old y old man is evaluated in the hospital p because 

of disorientation and hallucinations. 

He was admitted to the hospital 4 days ago for a 

subarachnoid hemorrhage that was repaired with 

surgical clipping clipping. 

His medical medical history is is otherwise otherwise unremarkable; unremarkable; before 

before 

he was admitted to the hospital, he took no 

medications.

Physical Exam 

He is disoriented, confused, 

and hallucinating. 

Temperature p is normal 

Lying BP 140/80 HR 90 RR 

16 

Standing Sta d g BP 120/60 0/60 HR H 110 0 

The remainder of the 

physical examination is 

normal. 

Laboratory values were 

normal on admission 


4 

118 85 

4.1 23 

POsm 248 mosm/kg 

Urine Na 105 K 20 Cl 90 

Ui UrineOsm O 633 mosm/kg /k


4 


likely 

diagnosis? 

A. Adrenal insufficiency 

B. Cerebral Salt Wasting 

C. Hypothyroidism 

yp y 

D. SIADH


4 


likely 

diagnosis? 

A. Adrenal insufficiency 

B. B. Cerebral Cerebral Salt Salt Wasting Wasting 

C. Hypothyroidism 

yp y 

D. SIADH

Na AND H 2O 

deficit 

Hypovolemia 

Total body Na ↓↓ 

Total body H 2O ↓ 

EABV ↓ 

RAAS ↑↑ 

ADH ↑ 

**Urine Na < 20 

meq/L 

Urine Osm > 300 

mOsm/L 

Clinical Approach to 

Hyponatremia 

H2O excess 

ONLY 

**“Look” the same to the body 

“Look” the same to the body 

(urine findings dependent on intact 

(urine findings dependent on intact 

tubular b l function f i and dabsence b of f 

tubular function 

Euvolemia 

and absence of diuretics) 

diuretics) 

Total body Na nl 

Total body H2O ↑↑ 

EABV nl (or ( high) g ) 

RAAS (-) 

ADH ↑ 

Urine Na > 40 

meq/L 


RAAS (-) 

ADH ↓ 

Urine Na < 10 

meq/L 

Urine Osm < 100 

mOsm/L mOsm/L 

Na AND H 2O 

excess 

Hypervolemia 

Total body Na ↑ 

Total body H 2O ↑↑ 

EABV ↓ 

RAAS ↑↑ 

ADH ↑ 

**Urine Na < 20 

meq/L 


mOsm/L

Urine Na 

Urine Osmolality 

Blood Pressure 

Central venous 

pressure p 

CSW vs. SIADH 

SIADH Cerebral Salt Wasting

CSW vs. SIADH 

SIADH Cerebral Salt Wasting 

Urine Na ↑↑ ↑↑ 

Urine Osmolality ↑↑ ↑↑ 

Blood Pressure 


pressure p

CSW vs. SIADH 

SIADH Cerebral Salt Wasting 

Urine Na ↑↑ ↑↑ 

Urine Osmolality ↑↑ ↑↑ 

Blood Pressure Normal 


pressure p 

Ø orthostatic th t ti change h 

Normal High Low 

++ orthostatic change

Physical Exam 

He is disoriented, confused, 

and hallucinating. 

Temperature p is normal 

Lying BP 140/80 HR 90 RR 

16 

Standing Sta d g BP 120/60 0/60 HR H 110 0 

The remainder of the 

physical examination is 

normal. 

Laboratory values were 

normal on admission 


4 

118 85 

4.1 23 


Urine Na 105 K 20 Cl 90 

Ui UrineOsm O 633 mosm/kg /k


5 

A A19 A19-year A 19 year-old year old man man is evaluated in in the the emergency 

emergency 

department for altered mental status. 

He is accompanied by a friend, who states that 

the patient patient was was asymptomatic asymptomatic 12 12 hours hours ago. 

ago. 

Medical history history is is noncontributory, noncontributory and and he he takes 

takes 

no medications. He does not drink alcoholic 

beverages or or use use illicit illicit drugs. 

drugs.

Physical Exam 

Patient is comatose 

Afebrile, BP 90/60 HR 110 

RR 28 

Cardiopulmonary 


Arterial te a oxygen o yge saturation sat at o is s 

96% by pulse oximetry with 

the patient breathing ambient 

air. 

There are no localized 

findings on neurologic 

examination. 


5 

142 108 14 

3.6 14 


UA UA: + k ketones t ( (-- ( --) ) glucose l 

7.42/20/94

Question 5 

5 


likely 

diagnosis? 

A. Alcoholic ketoacidosis 

B. Ethylene glycol intoxication 

C. Methanol intoxication 

D. Salicylate toxicity

Question 5 

5 


likely 

diagnosis? 

A. Alcoholic ketoacidosis 

B. Ethylene glycol intoxication 

C. Methanol intoxication 

D. D. Salicylate Salicylate toxicity toxicity

Approach to the Patient with Acid- 

HCO 3 - < 24 

Metabolic 

Acidosis 

pH < 

735A 7.35Acidemia id i 

Base Disorders 

HCO 3 - > 24 + 

pCO 2 > 45 

Respiratory 

Acidosis 

Estimate pH 

(ABG) 

HCO 3 - > 30 

Metabolic 

Alkalosis 

pH p > 7.45 

Alkalemia 

HCO 3 - < 30 + 

pCO 2 < 35 

Respiratory 

Alkalosis

Assess for for Compensation 

Compensation 

Acute resp p acidosis Acute resp p alkalosis 

The [HCO [HCO3] ] will increase by 1 

mmol/l for every 10 mmHg 

elevation in pCO pCO2 above 40 

mmHg mmHg. 

Expected [HCO [HCO3] ] = 24 + { 

(Actual pCO pCO2 - 40) / 10 } 

Chronic Chronic resp resp acidosis 

acidosis 

The [HCO3] will increase by 4 

mmol/l for every 10 mmHg 

elevation in pCO2 p above 

40mmHg. 

Expected [HCO3] = 24 + 4 { 

(Actual pCO2 - 40) / 10} 

The [HCO3] will decrease by 

2 mmol/l for every 10 mmHg 

decrease in pCO2 below 40 

mmHg mmHg. 

Expected [HCO3] = 24 -2 2 { ( 

40 - Actual pCO2) / 10 } 

Chronic Chronic resp resp alkalosis 

alkalosis 

The [HCO3] will decrease by 

5 mmol/l for every 10 mmHg 

decrease in pCO2 p below 40 

mmHg. 

Expected [HCO3] = 24 -5 5 { ( 

40 - Actual pCO2 ) / 10 } 

(range: +/ +/- +/ 2)

Assess for for Compensation 

Compensation

Physical Exam 

Patient is comatose 

Afebrile, BP 90/60 HR 110 

RR 28 

Cardiopulmonary 


Arterial te a oxygen o yge saturation sat at o is s 

96% by pulse oximetry with 

the patient breathing ambient 

air. 

There are no localized 

findings on neurologic 

examination. 


5 

142 108 14 

3.6 14 


UA UA: + k ketones t ( (-- ( --) ) glucose l 

7.42/20/94


6 

A A22 A22-year A 22 year-old year old old woman woman is is evaluated evaluated at at an an on on-site site medical 

medical 

center after collapsing while running a marathon. 

She is disoriented. During the evaluation, she 

experiences p a g generalized tonic tonic-clonic clonic seizure lasting g 3 

minutes. 

A wristband indicates that she has diabetes mellitus.

Physical Exam 

Exam 

Temp normal 

BP BP 120/60 120/60 HR HR 100 100 RR RR 28 

28 


7 

There is no evidence of hypovolemia or edema. 

Cardiopulmonary examination is normal. 

On neurologic examination, she is confused but has no 

evidence of a focal neurologic g deficit. 

Na 118 118 meq/L meq/L Glucose Glucose 120 120 mg/dl 

mg/dl


7 

Which of of the the following following is the most appropriate 

appropriate 

next step in management? 

A. 3% saline infusion 

B. 50% glucose bolus infusion 

C. IV Furosemide infusion 

D. IV 0.9% saline infusion


7 

Which of of the the following following is the most appropriate 

appropriate 

next step in management? 

A. A. 3% 3% saline saline infusion infusion 

B. 50% glucose bolus infusion 

C. IV Furosemide infusion 

D. IV 0.9% saline infusion

Treatment of hyponatremia: 

Special circumstances 

Acute hyponatremia with neurologic dysfunction 

must be treated emergently 

3% Saline solution 100 ml administered over 15 

minutes (can be repeated up to 3 times) 

Raise [Na] by approx 5 mmol/L 

Slow correction to standard goal


8 

56 56-year year y old man with a history y of alcoholism is found 

lying on the street. 

O On arrival i l at tth the emergency department, d t t he h is i 

confused. 

Physical Exam 

T 36.1 °C C BP 126/80 HR 70 

Funduscopic examination shows no papilledema. 

Cardiac, pulmonary, and abdominal examinations are 

normal normal.

138 98 45 

54 14 28


8 

What is the most most likely likely diagnosis? 

diagnosis? 

A. Al Alcoholic h li k ketoacidosis id i 

B. Diabetic ketoacidosis 

C. Ethylene glycol poisoining 

D D. Lactic acidosis 

acidosis


8 

What is the most most likely likely diagnosis? 

diagnosis? 

A. Al Alcoholic h li k ketoacidosis id i 

B. Diabetic ketoacidosis 

C. Ethylene glycol poisoning 

D D. Lactic acidosis 

acidosis

Question 8

138 98 45 

54 14 28


9 

A A47 A47-year A 47 year-old year old man with a long long-standing long standing history of 

alcoholism is hospitalized for abdominal pain, nausea, 

and vomiting of 7 days’ duration. 

His last drink was 6 days y ago. g 

He has lost approximately pp y 10% of his body y weight g over 

the past 4 months; he states that his weight loss was 

caused by drinking alcohol and not eating.

Physical y Exam 

He appears cachectic. 

T 37.1 BP 100/70 HR 110 rr 

18 BMI 17 

He is not confused or 

tremulous tremulous. 

There is midepigastric 

tenderness without rebound. 

Bowel sounds are present. 

Neurologic examination is 

normal. 


9 

130 90 

3.4 20 

Ca 9.0 mg/dl Phos 3.5 mg/dl 

Amylase 300 IU/L / 

Lipase 150 IU/L 

UA UA—ketones ketones positive


9 

The patient p receives immediate thiamine replacement, p folic acid 

supplementation, and a multivitamin followed by vigorous 

intravenous fluid replacement with 5% dextrose and normal 

saline with aggressive gg potassium p replacement. p 

Morphine is used to control pain. 

Eighteen hours later, the patient’s abdominal pain has improved 

but he becomes restless, agitated, g and extremely weak and is 

barely able to raise his extremities against gravity.


9 

Which is is the the most most likely likely cause cause of of the the patient patient’s s new 

new 

findings? 

A. Hypercalcemia 

B. Hypokalemia 

C. Hyponatremia 

yp 

D. Hypophosphatemia


9 

Which is is the the most most likely likely cause cause of of the the patient patient’s s new 

new 

findings? 

A. Hypercalcemia 

B. Hypokalemia 

C. Hyponatremia 

yp 

D. D. Hypophosphatemia 

Hypophosphatemia

Symptoms of Hypophosphatemia 

Myopathy y p yRhabdomyolysis y y 

Hemolysis 

Respiratory failure 

↓Myocardial performance 

Leukocyte dysfunction 

Neurologic dysfunction

Phos < 2.5 mg/dl 

Approach to the patient with 

Urine Phos < 

100 mg/d or 

FePi < 5% 

Hypophosphatemia PTH 

Urine Phos > 

100 mg/d or 

FePi > 5% 

Recent glucose 

and/or insulin 

administration 

No Recent 

glucose and/or 

insulin 

administration 

Renal Phosphate wasting 

2º to 

Hyperparathyroidism, 

Intracellular 

redistribution 

Hi Highh 

Severe total body 

deficiency 

Hyperparathyroidism 

yp p y 

PTH 

normal Fanconi’s Fanconi s, TIO TIO, XLH XLH, 

ADHR


9 

The patient p receives immediate thiamine replacement, p folic acid 

supplementation, and a multivitamin followed by vigorous 

intravenous fluid replacement with 5% dextrose and normal 

saline with aggressive gg potassium p replacement. p 

Morphine is used to control pain. 

Eighteen hours later, the patient’s abdominal pain has improved 

but he becomes restless, agitated, g and extremely weak and is 

barely able to raise his extremities against gravity.

Question 10 

A 45-year-old y black woman is evaluated for a 2-month history y of 

fatigue, nonproductive cough, decreased appetite, intermittent 

fever, right upper-quadrant abdominal pain, and a 4.5-kg (10.0lb) 

) weight g loss. 

Phys Exam 37.8 °C BP 104/68 mm Hg, HR 100/min RR 16 

BMI 28. 28 There are several erythematous 5- 5 to 10-mm 10 mm 

maculopapular lesions on the forehead. 

Cardiopulmonary examination is normal. Abdominal 

examination reveals hepatomegaly. There is bilateral inguinal 

lymphadenopathy. y p p y 

There is no edema.


10 

Laboratory studies 

Ca 11.2 mg/dl 

Tuberculin skin testing is negative. 

Phos 4.0 mg/dl 

Albumin 4.0 g/dl 

Urine culture is negative. 

Cr. 2.0 mg/dl 

Hgb g 12.2 

Chest radiograph shows bilateral 

hilar lymphadenopathy. 

Renal U/S Right kidney is 13.7 cm 

UA: 1+ prot 20 WBCS/hpf, WBC 

casts 

Urine Prot:Cr 0.914 mg/mg 

Left kidney is 15.4 cm. There is no 

hydronephrosis, and no kidney 

calculi are are seen 

seen

Question 10 


likely 

diagnosis? 

A. Amyloidosis 

B. Sarcoidosis 

C. Sjogren’s j g syndrome y 

D. SLE

Question 10 


likely 

diagnosis? 

A. Amyloidosis 

B. B. Sarcoidosis Sarcoidosis 

C. Sjogren’s j g syndrome y 

D. SLE

Overview of Calcium homeostasis

Calcium > 10.5 

mg/dl g 

Approach to the patient with 

PTH 

appropriately 

suppressed 

PTH Above 

UNL 

Hypercalcemia 

PTHRP elevated 

PTHRP not 

detected 

Primary 

Hyperparathyroidism 

Humoral hypercalcemia 

or malignancy 

1, 25-OH 

vitamin D 

elevated 

1,25-OH 

vitamin D 

normal 

Granulomatous 

disease or 

lymphoma 

Lytic lesions of 

bone, 

immobilization


10 

Laboratory studies 

Ca 11.2 mg/dl 

Tuberculin skin testing is negative. 

Phos 4.0 mg/dl 

Albumin 4.0 g/dl 

Urine culture is negative. 

Cr. 2.0 mg/dl 

Hgb g 12.2 

Chest radiograph shows bilateral 

hilar lymphadenopathy. 

Renal U/S Right kidney is 13.7 cm 

UA: 1+ prot 20 WBCS/hpf, WBC 

casts 

Urine Prot:Cr 0.914 mg/mg 

Left kidney is 15.4 cm. There is no 

hydronephrosis, and no kidney 

calculi are are seen 

seen

Electrolytes and Acid Base with Suneel Udani 4.11.11

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