nephrology lecture acid - base balance presented by anas diab md us board certified in nephrology...

Nephrology LectureNephrology Lecture

Acid - Base BalanceAcid - Base BalancePresented byPresented byAnas Diab MDAnas Diab MD

US Board Certified in NephrologyUS Board Certified in NephrologyUniversity of Michigan GraduateUniversity of Michigan Graduate

Acid – Base BalanceAcid – Base Balance

Each day approximately 15,000 mmol of carbon dioxide Each day approximately 15,000 mmol of carbon dioxide form ,from oxidation of carbohydrates, amino acids, and form ,from oxidation of carbohydrates, amino acids, and fatty acids, and this can rapidly excreted by the lung.fatty acids, and this can rapidly excreted by the lung.60-70 meq or approximately 1 meq/kg body weight ,of 60-70 meq or approximately 1 meq/kg body weight ,of fixed nonvolatile acid (mineral acid) mostly sulfuric acid, fixed nonvolatile acid (mineral acid) mostly sulfuric acid, derived from the metabolism of sulfur-containing amino derived from the metabolism of sulfur-containing amino acids), and phosphate.acids), and phosphate.The concentration of free hydrogen ion in body fluid isThe concentration of free hydrogen ion in body fluid is

40 nanoequivalents /L, so adding 60-70 meq of 40 nanoequivalents /L, so adding 60-70 meq of hydrogen ion produced daily would be rapidly fatal, if not hydrogen ion produced daily would be rapidly fatal, if not immediately bufferedimmediately bufferedAcid-base balance is maintained to the normal by renal Acid-base balance is maintained to the normal by renal excretion of acid, through a number of intra and extra excretion of acid, through a number of intra and extra cellular buffers .cellular buffers .

Assessment of Acid – Base Assessment of Acid – Base BalanceBalance

Bicarbonate-carbon dioxide buffer system:Bicarbonate-carbon dioxide buffer system:

Dissolved CO2 +H2O <--> Dissolved CO2 +H2O <-->

H2CO3 <-> HCO3- + H+H2CO3 <-> HCO3- + H+

The Henderson - Hasselbalch equation:The Henderson - Hasselbalch equation:

pH = 6.10 + pH = 6.10 + log ([HCO3-] ÷ [0.03 x PCO2])log ([HCO3-] ÷ [0.03 x PCO2])

Renal excretion of acid Renal excretion of acid

• One third of net acid secretion involves the combination of hydrogen ions with urinary titratable acids, particularly phosphate (HPO4 + H+ —> H2PO4) .

Two third of net acid secretion involves the excretion of excess hydrogen ions as Amonium ions. Electroneutrality is preserved by coupling amonium ions to chloride forming Amonium chloride , and the end result that appropriate titration of renal acidity should result in high levels of urinary chloride.

DEFINITIONSDEFINITIONS

Acidosis — A process that tends to lower the Acidosis — A process that tends to lower the extracellular fluid pH :extracellular fluid pH :

this can be induced by a fall in the extracellular this can be induced by a fall in the extracellular (or plasma ) bicarbonate concentration or by an (or plasma ) bicarbonate concentration or by an elevation in the PCO2.elevation in the PCO2.

Alkalosis — A process that tends to raise the Alkalosis — A process that tends to raise the extracellular fluid pH extracellular fluid pH

this can be induced by an elevation in the this can be induced by an elevation in the extracellular (or plasma ) bicarbonate extracellular (or plasma ) bicarbonate concentration or by a fall in the PCO2.concentration or by a fall in the PCO2.

Type of AcidosisType of Acidosis

Metabolic acidosis — A disorder Metabolic acidosis — A disorder associated with a low pH and low associated with a low pH and low bicarbonate concentration. bicarbonate concentration.

Respiratory acidosis — A disorder Respiratory acidosis — A disorder associated with a low pH and high PCO2.associated with a low pH and high PCO2.

Type of AlkalosisType of Alkalosis

Metabolic alkalosis — A disorder Metabolic alkalosis — A disorder associated with a high pH and high associated with a high pH and high bicarbonate concentration.bicarbonate concentration.

Respiratory alkalosis — A disorder Respiratory alkalosis — A disorder associated with a high pH and low PCO2.associated with a high pH and low PCO2.

Causes of Metabolic AcidosisCauses of Metabolic Acidosis

Overproduction of Endogenous acid Overproduction of Endogenous acid (Diabetic Ketoacidosis)(Diabetic Ketoacidosis)

Loss of Alkali stores (Diarrhea or Renal Loss of Alkali stores (Diarrhea or Renal Tubular Acidosis)Tubular Acidosis)

Failure of Renal Acid Secretion or base Failure of Renal Acid Secretion or base synthesis ( Renal Failure)synthesis ( Renal Failure)

Compensatory responsesCompensatory responses

Each of the simple acid-base disorders is also Each of the simple acid-base disorders is also associated with a compensatory response. associated with a compensatory response. The Henderson-Hasselbalch equation shows The Henderson-Hasselbalch equation shows that the pH is determined by the ratio between that the pH is determined by the ratio between the HCO3 concentration and PCO2, not by the the HCO3 concentration and PCO2, not by the value of either one alone. value of either one alone. The body responds to an acid-base disorder by The body responds to an acid-base disorder by making compensatory respiratory or renal making compensatory respiratory or renal responses in an attempt to normalize the pH. responses in an attempt to normalize the pH. This response is mediated at least in part by This response is mediated at least in part by parallel alterations in regulatory cell (renal parallel alterations in regulatory cell (renal tubular or respiratory center) pH tubular or respiratory center) pH

Compensation in Met. AcidosisCompensation in Met. Acidosis

Ventilation is increased, resulting in a fall in PCO2, which Ventilation is increased, resulting in a fall in PCO2, which tends to raise the pH toward normal. tends to raise the pH toward normal.

Note that protection of the HCO3/PCO2 ratio and Note that protection of the HCO3/PCO2 ratio and therefore the pH requires a compensatory response that therefore the pH requires a compensatory response that varies in the same direction as the primary disorder (low varies in the same direction as the primary disorder (low bicarbonate leads to low PCO2). bicarbonate leads to low PCO2).

The respiratory compensation results in a 1.2 mmHg fall The respiratory compensation results in a 1.2 mmHg fall in the PCO2 for every 1 meq/L reduction in the plasma in the PCO2 for every 1 meq/L reduction in the plasma bicarbonate concentration . This response begins in the bicarbonate concentration . This response begins in the first hour, and is complete by 12 to 24 hours . first hour, and is complete by 12 to 24 hours .

Compensation in Met. AlkalosisCompensation in Met. Alkalosis

The respiratory compensation tends to raise the The respiratory compensation tends to raise the PCO2 by 0.7 mmHg for every 1 meq/L elevation PCO2 by 0.7 mmHg for every 1 meq/L elevation in the plasma bicarbonate concentration in the plasma bicarbonate concentration This response may not be seen in all patients This response may not be seen in all patients because of concurrent problems. because of concurrent problems. For example, diuretics tend to induce metabolic For example, diuretics tend to induce metabolic alkalosis in heart failure or cirrhosis; both of alkalosis in heart failure or cirrhosis; both of these disorders, however, are associated with these disorders, however, are associated with hyperventilation and a low PCO2. Thus, the hyperventilation and a low PCO2. Thus, the expected rise in PCO2 with metabolic alkalosis expected rise in PCO2 with metabolic alkalosis may not be seen due to the underlying may not be seen due to the underlying respiratory alkalosis. respiratory alkalosis.

Compensation in Respiratory Compensation in Respiratory acidosisacidosis

The compensatory response to respiratory acid-base disorders occurs in two The compensatory response to respiratory acid-base disorders occurs in two stages: stages:

1- Cell buffering that acts within minutes to hours 1- Cell buffering that acts within minutes to hours 2- The renal compensation that is not complete for 3 to 5 days. 2- The renal compensation that is not complete for 3 to 5 days. As a result, different responses are seen with acute and chronic disorders. As a result, different responses are seen with acute and chronic disorders.

In acute respiratory acidosis, In acute respiratory acidosis, The [HCOThe [HCO33] will increase by 1 mmol/l ] will increase by 1 mmol/l for every 10 mmHg elevation in pCOfor every 10 mmHg elevation in pCO22 above 40 mmHg. above 40 mmHg.Expected [HCOExpected [HCO33] = 24 + { (Actual pCO] = 24 + { (Actual pCO22 - 40) / 10 } - 40) / 10 }In chronic respiratory acidosis In chronic respiratory acidosis The [HCO3] will increase by 4 mmol/l The [HCO3] will increase by 4 mmol/l for every 10 mmHg elevation in pCO2 above 40mmHg.for every 10 mmHg elevation in pCO2 above 40mmHg.Expected [HCO3] = 24 + 4 { (Actual pCO2 - 40) / 10}Expected [HCO3] = 24 + 4 { (Actual pCO2 - 40) / 10}The renal response is carefully regulated, so that administering extra The renal response is carefully regulated, so that administering extra bicarbonate results in the urinary excretion of the excess alkali without bicarbonate results in the urinary excretion of the excess alkali without elevation in the plasma bicarbonate concentration elevation in the plasma bicarbonate concentration

Compensation in Respiratory Compensation in Respiratory alkalosisalkalosis

In acute respiratory alkalosis, In acute respiratory alkalosis, The [HCO3] will The [HCO3] will decrease by 2 mmol/l for every 10 mmHg decrease by 2 mmol/l for every 10 mmHg decrease in pCO2 below 40 mmHg.decrease in pCO2 below 40 mmHg.

Expected [HCO3] = 24 - 2 { ( 40 - Actual Expected [HCO3] = 24 - 2 { ( 40 - Actual pCO2) / 10 }pCO2) / 10 }

In chronic respiratory alkalosis,In chronic respiratory alkalosis,The [HCO3] will The [HCO3] will decrease by 5 mmol/l for every 10 mmHg decrease by 5 mmol/l for every 10 mmHg decrease in pCO2 below 40 mmHg.decrease in pCO2 below 40 mmHg.

Expected [HCO3] =24 - 5 { ( 40 - Actual Expected [HCO3] =24 - 5 { ( 40 - Actual pCO2) / 10 } ( range: +/- 2)pCO2) / 10 } ( range: +/- 2)Reductions in both bicarbonate reabsorption and in Reductions in both bicarbonate reabsorption and in ammonium excretion contribute to the compensatory ammonium excretion contribute to the compensatory reduction in the plasma bicarbonate concentration reduction in the plasma bicarbonate concentration

MIXED ACID-BASE DISORDERSMIXED ACID-BASE DISORDERS

Some patients have two or more acid-base Some patients have two or more acid-base disorders. disorders.

An understanding of the approach to this An understanding of the approach to this problem requires knowledge of the renal and problem requires knowledge of the renal and respiratory compensations that have been respiratory compensations that have been empirically observed in patients with simple acid-empirically observed in patients with simple acid-base disorders. base disorders.

Values substantially different from those that are Values substantially different from those that are expected indicates the presence of a mixed expected indicates the presence of a mixed disturbance disturbance

How to reach a diagnosis?How to reach a diagnosis?

Evaluation of an acid-base disorder begins with Evaluation of an acid-base disorder begins with measurement of the extra cellular pH measurement of the extra cellular pH Measurement of the plasma bicarbonate Measurement of the plasma bicarbonate concentration, concentration, A low plasma bicarbonate concentration can be A low plasma bicarbonate concentration can be seen as the primary change in metabolic seen as the primary change in metabolic acidosis and as the compensatory response in acidosis and as the compensatory response in respiratory alkalosis. respiratory alkalosis. Once the primary change is determined, the Once the primary change is determined, the degree of compensation should then be degree of compensation should then be assessed. assessed. You can not over- compensate, as a golden rule.You can not over- compensate, as a golden rule.

Establishing a diagnosis requires a Establishing a diagnosis requires a careful history :careful history :

Diarrhea would suggest metabolic acidosisDiarrhea would suggest metabolic acidosis

Vomiting would suggest metabolic Vomiting would suggest metabolic alkalosisalkalosis

History of COPD would suggest History of COPD would suggest respiratory acidosisrespiratory acidosis

History of Psychosis would suggest History of Psychosis would suggest respiratory alkalosis.respiratory alkalosis.

Normal Anion Gap Metabolic Normal Anion Gap Metabolic AcidosisAcidosis

Defined in terms of the serum potassium Defined in terms of the serum potassium concentration:concentration:Hypokalemic : - Diarrhea, Ureteral Hypokalemic : - Diarrhea, Ureteral diversion, Use of Carbonic inhydrase diversion, Use of Carbonic inhydrase inhibitors - Renal Tubular Acidosis: inhibitors - Renal Tubular Acidosis: Type I, or Type IIType I, or Type IIHyperkalemic : Total parenteral nutrition Hyperkalemic : Total parenteral nutrition oral Calcium chloride , obstructive oral Calcium chloride , obstructive uropathy, addison disease , Type IV RTA.uropathy, addison disease , Type IV RTA.

High Anion Gap Metabolic AcidosisHigh Anion Gap Metabolic Acidosis

MUDPILES : Methanol, Uremia, Diabetic MUDPILES : Methanol, Uremia, Diabetic Ketoacidosis, Paraldehyde, Isoniazide, Ketoacidosis, Paraldehyde, Isoniazide, Lactic Acidosis, Ethanol Ethylene glycole, Lactic Acidosis, Ethanol Ethylene glycole, Salicylates.Salicylates.

In chronic renal failure the anion gap is In chronic renal failure the anion gap is less than 25, if more than 25 we should less than 25, if more than 25 we should think about ingestion of poison.think about ingestion of poison.

When to measure The Anion GapWhen to measure The Anion Gap

Anion Gap = NA –(Cloride+Bicarb)Anion Gap = NA –(Cloride+Bicarb)We measure it in each case of metabolic We measure it in each case of metabolic acidosisacidosisNormal anion gap 10-14mEq/LNormal anion gap 10-14mEq/LElevated in cases of overproduction of Elevated in cases of overproduction of endogenously produced organic acids such Keto endogenously produced organic acids such Keto Acidosis or Lactic Acidosis, or the ingestion of Acidosis or Lactic Acidosis, or the ingestion of certain toxins such as Salicylate, Metanol, or certain toxins such as Salicylate, Metanol, or Ethylene Glycol.Ethylene Glycol.In advance renal failure because decreased In advance renal failure because decreased ability of the kidneys to regenerate bicarbonate ability of the kidneys to regenerate bicarbonate through the Amoniagenesis.through the Amoniagenesis.

HintsHints

An elevated Anion Gap always An elevated Anion Gap always strongly suggests a Metabolic strongly suggests a Metabolic Acidosis.Acidosis.

If AG is 20-30 then high chance If AG is 20-30 then high chance (67%) of metabolic acidosis (67%) of metabolic acidosis

If AG is > 30 then a metabolic If AG is > 30 then a metabolic acidosis is definitely present acidosis is definitely present

The delta anion gap / delta bicarbonate in The delta anion gap / delta bicarbonate in metabolic acidosismetabolic acidosis

We use this concept to determine a mix acid base We use this concept to determine a mix acid base disorder.disorder.

The delta /delta ratio in an uncomplicated high AG The delta /delta ratio in an uncomplicated high AG metabolic acidosis should be between 1 and 2.metabolic acidosis should be between 1 and 2.

A lower value (in which the delta AG is less than A lower value (in which the delta AG is less than expected from the delta HCO3) reflects either urinary expected from the delta HCO3) reflects either urinary ketone losses (as in diabetic ketoacidosis)or in CKD. or a ketone losses (as in diabetic ketoacidosis)or in CKD. or a combined high and normal AG acidosis, as might occur if combined high and normal AG acidosis, as might occur if diarrhea were superimposed upon chronic renal failurediarrhea were superimposed upon chronic renal failure

a delta /delta ratio above 2 indicates the plasma HCO3 a delta /delta ratio above 2 indicates the plasma HCO3 is lower than expected from the rise in the AG; this is lower than expected from the rise in the AG; this usually reflects a concurrent metabolic alkalosis, as with usually reflects a concurrent metabolic alkalosis, as with vomiting.vomiting.

If a metabolic acidosis is diagnosed, then the If a metabolic acidosis is diagnosed, then the Delta Ratio should be checkedDelta Ratio should be checked

Delta Ratio Assessment Guidelines in patients with a Delta Ratio Assessment Guidelines in patients with a metabolic acidosismetabolic acidosis : :

< 0.4 - Hyperchloraemic normal anion gap acidosis < 0.4 - Hyperchloraemic normal anion gap acidosis

0.4 to 0.8 - Combined high AG and normal AG acidosis 0.4 to 0.8 - Combined high AG and normal AG acidosis

1 - Common in DKA due to urinary ketone loss 1 - Common in DKA due to urinary ketone loss

1 to 2 - Typical pattern in high anion gap metabolic acidosis 1 to 2 - Typical pattern in high anion gap metabolic acidosis

> 2 Check for either a co-existing Metabolic Alkalosis (which > 2 Check for either a co-existing Metabolic Alkalosis (which would elevate [HCO3]) or a co-existing Chronic Respiratory would elevate [HCO3]) or a co-existing Chronic Respiratory Acidosis (which results in compensatory elevation of [HCO3]) Acidosis (which results in compensatory elevation of [HCO3])

Urinary Anion gapUrinary Anion gap

In metabolic acidosis with a normal serum Anion In metabolic acidosis with a normal serum Anion Gap we have to determine weather the loss in Gap we have to determine weather the loss in Bicarbonate is renal or extra renal from GI loss Bicarbonate is renal or extra renal from GI loss as in Diarrhea.as in Diarrhea.Urinary Anion Gap= Ur Cl- (Ur Na + Ur K)Urinary Anion Gap= Ur Cl- (Ur Na + Ur K)It estimates the Amonium Excretion .It estimates the Amonium Excretion .If it is more negative than -30 it reflect normal If it is more negative than -30 it reflect normal response to severe GI lossresponse to severe GI lossIf it is positive it means impaired urinary If it is positive it means impaired urinary Acidification as in Type I RTAAcidification as in Type I RTA

Osmolal GapOsmolal Gap

Serum Osm= 2X(NA)+ glu/18 +BUN/2.8Serum Osm= 2X(NA)+ glu/18 +BUN/2.8

Osmolal Gap = Measured Osm-Calculated Osmolal Gap = Measured Osm-Calculated Osm.Osm.

An elevated Osmolal gap in the setting of An elevated Osmolal gap in the setting of a metabolic acidosis with elevated Anion a metabolic acidosis with elevated Anion Gap suggests intoxication with a low Gap suggests intoxication with a low molecular-weight substance such as molecular-weight substance such as Methanol or Ethylene glycol.Methanol or Ethylene glycol.

Indication to use bicarbonate Indication to use bicarbonate therapytherapy

Reserved for patient with severe metabolic acidosis pH Reserved for patient with severe metabolic acidosis pH less than 7.15, or serum bicarb less than 12 mEq/L.less than 7.15, or serum bicarb less than 12 mEq/L.Most beneficial in cases of loss of bicarb as in diarrheaMost beneficial in cases of loss of bicarb as in diarrheaNot indicated if in lactic acidosis .Not indicated if in lactic acidosis .Calculated based on the Serum bicarb to be corrected to Calculated based on the Serum bicarb to be corrected to 1515Bicarb needs = body weight X volume of distribution X Bicarb needs = body weight X volume of distribution X ( 15 – the measured bicarb)( 15 – the measured bicarb)50% of the calculated bicarb dose should be 50% of the calculated bicarb dose should be administered bollus, and the rest over 6-12 hours.administered bollus, and the rest over 6-12 hours.

Case study- 1Case study- 1

A patient with diarrhea has an arterial pH of A patient with diarrhea has an arterial pH of 7.23, bicarbonate concentration of 10 meq/L, 7.23, bicarbonate concentration of 10 meq/L, and PCO2 of 23 mmHg and PCO2 of 23 mmHg What is your diagnosis?What is your diagnosis?The low pH indicates acidemia, and the low The low pH indicates acidemia, and the low plasma bicarbonate concentration indicates plasma bicarbonate concentration indicates metabolic acidosis. metabolic acidosis. The plasma bicarbonate concentration is 14 The plasma bicarbonate concentration is 14 meq/L below normal, which should lead to a 17 meq/L below normal, which should lead to a 17 mmHg fall in the PCO2 (14 x 1.2 = 17) from 40 mmHg fall in the PCO2 (14 x 1.2 = 17) from 40 to 23 mmHg. to 23 mmHg.

Case study 1 cont.Case study 1 cont.

This patient has a simple metabolic This patient has a simple metabolic acidosis . acidosis . A PCO2 significantly higher than this level A PCO2 significantly higher than this level would indicate a concurrent respiratory would indicate a concurrent respiratory acidosis. acidosis. If, on the other hand, the PCO2 were If, on the other hand, the PCO2 were lower than 20 mmHg, then a concurrent lower than 20 mmHg, then a concurrent respiratory alkalosis would be present, as respiratory alkalosis would be present, as might be seen with salicylate intoxication. might be seen with salicylate intoxication.

Case study 2Case study 2

D.D is a 56 Y/O smoker 1PP/D for 25 years has D.D is a 56 Y/O smoker 1PP/D for 25 years has the following arterial blood values: pH equals the following arterial blood values: pH equals 7.27; PCO2 equals 70 mmHg; and bicarbonate 7.27; PCO2 equals 70 mmHg; and bicarbonate concentration equals 31 meq/L. concentration equals 31 meq/L. What is your diagnosis?What is your diagnosis?

The low pH and hypercapnia indicate that the The low pH and hypercapnia indicate that the patient has some form of respiratory acidosis. patient has some form of respiratory acidosis.

In view of the 30 mmHg rise in the PCO2, the In view of the 30 mmHg rise in the PCO2, the plasma bicarbonate concentration should be plasma bicarbonate concentration should be elevated by 3 meq/L (to 27 meq/L) in with acute elevated by 3 meq/L (to 27 meq/L) in with acute hypercapnia, and by 11 meq/L (to 35 meq/L) with hypercapnia, and by 11 meq/L (to 35 meq/L) with chronic hypercapnia. chronic hypercapnia.

Case study 2 cont.Case study 2 cont.

The observed value of 31 meq/L is between these expected levels The observed value of 31 meq/L is between these expected levels and could be explained by one of three disorders : and could be explained by one of three disorders :

1-Chronic respiratory acidosis with superimposed metabolic 1-Chronic respiratory acidosis with superimposed metabolic acidosis to lower the plasma bicarbonate concentration, as might acidosis to lower the plasma bicarbonate concentration, as might occur in a patient with chronic obstructive pulmonary disease who occur in a patient with chronic obstructive pulmonary disease who develops diarrhea due to viral gastroenteritis.develops diarrhea due to viral gastroenteritis.

2- Acute respiratory acidosis with superimposed metabolic alkalosis 2- Acute respiratory acidosis with superimposed metabolic alkalosis to elevate the plasma bicarbonate concentration, as might occur in a to elevate the plasma bicarbonate concentration, as might occur in a patient with vomiting due to patient with vomiting due to theophyllinetheophylline toxicity who then develops toxicity who then develops an acute asthmatic attack.an acute asthmatic attack.

Acute, superimposed on mild chronic respiratory acidosis, as can be Acute, superimposed on mild chronic respiratory acidosis, as can be induced by pneumonia in a patient with chronic hypercapnia.induced by pneumonia in a patient with chronic hypercapnia.

Case study 2-cont.Case study 2-cont.

Thus, the correct diagnosis in a primary respiratory acid-Thus, the correct diagnosis in a primary respiratory acid-base disorder can be established only when correlated base disorder can be established only when correlated with the clinical history. with the clinical history. This is true even when the arterial blood values appear This is true even when the arterial blood values appear to represent a simple disorder. If, for example, the to represent a simple disorder. If, for example, the plasma bicarbonate concentration had been 35 meq/L plasma bicarbonate concentration had been 35 meq/L then the results would have been compatible with an then the results would have been compatible with an uncomplicated chronic respiratory acidosis. However, uncomplicated chronic respiratory acidosis. However, similar findings could have been induced by the similar findings could have been induced by the combination of acute hypercapnia and metabolic combination of acute hypercapnia and metabolic alkalosis. The history should allow these possibilities to alkalosis. The history should allow these possibilities to be distinguished.be distinguished.

Case PresentationCase Presentation

A 28 Y/O woman presents for evaluation of malaise fatigue and A 28 Y/O woman presents for evaluation of malaise fatigue and weakness she is always thirsty and her eyes are gritty. The serum weakness she is always thirsty and her eyes are gritty. The serum levels of electrolytes are as follows : Na 135 mEq/l, K 1.2 mEq/l, Cl levels of electrolytes are as follows : Na 135 mEq/l, K 1.2 mEq/l, Cl 118 mEq/L, Bicarb 10 mEq/L, BUN 12 mg/dl, Cr 1.2 mg/dl. ABG’s 118 mEq/L, Bicarb 10 mEq/L, BUN 12 mg/dl, Cr 1.2 mg/dl. ABG’s pH 7.28 PaCo2 25 mm hg. Urinalysis shows pH 6.6, U.Na 35 pH 7.28 PaCo2 25 mm hg. Urinalysis shows pH 6.6, U.Na 35 mEq/l, U.K 20 mEq/L U.Cl 50 mEq/L .mEq/l, U.K 20 mEq/L U.Cl 50 mEq/L .What should be your next recommendation?What should be your next recommendation?

1- Order diuretic screen1- Order diuretic screen 2- Order psychiatric consult2- Order psychiatric consult 3- Order stool electrolytes3- Order stool electrolytes 4- Begin sodium bicarbonate 450 mEq tablets 2 tabs orally X 4/d4- Begin sodium bicarbonate 450 mEq tablets 2 tabs orally X 4/d 5- Initiate potassium repletion, followed by potassium ctrate.5- Initiate potassium repletion, followed by potassium ctrate.

The answer is potassium repletionThe answer is potassium repletion

The patient has Sicca complex and Renal Tubular The patient has Sicca complex and Renal Tubular Acidosis likely due to Sjogren syndromeAcidosis likely due to Sjogren syndromeNormal Anion gap Metabolic acidosisNormal Anion gap Metabolic acidosisUrinary Anion Gap is positiveUrinary Anion Gap is positiveRepletion of potassium is foremost in these situation Repletion of potassium is foremost in these situation because a potential disastrous exacerbation of this because a potential disastrous exacerbation of this patient’s hypokalemia may occur with base patient’s hypokalemia may occur with base supplementation alone.supplementation alone.Diuretic abuse often leads to hypokalemia but not Diuretic abuse often leads to hypokalemia but not metabolic acidosis, except with Acetazolamide.metabolic acidosis, except with Acetazolamide.

Quick CaseQuick Case

select the correct interpretation for the select the correct interpretation for the given arterial blood gas set:given arterial blood gas set:

pH 7.51, pCO2 40, HCO3- 31: pH 7.51, pCO2 40, HCO3- 31:

a. Normal a. Normal

b. Uncompensated metabolic alkalosis b. Uncompensated metabolic alkalosis

c. Partially compensated respiratory c. Partially compensated respiratory acidosis acidosis

d. Uncompensated respiratory alkalosis d. Uncompensated respiratory alkalosis

Quick caseQuick case


a. Uncompensated respiratory a. Uncompensated respiratory alkalosisalkalosisb. Uncompensated metabolic acidosis b. Uncompensated metabolic acidosis c. Partially compensated respiratory c. Partially compensated respiratory acidosisacidosisd. Partially compensated metabolic d. Partially compensated metabolic acidosis acidosis



a. Normal a. Normal

b. Uncompensated metabolic b. Uncompensated metabolic acidosis acidosis

c. Partially compensated c. Partially compensated respiratory acidosis respiratory acidosis

d. Partially compensated metabolic d. Partially compensated metabolic acidosis acidosis



a. Uncompensated metabolic acidosis a. Uncompensated metabolic acidosis

b. Uncompensated respiratory b. Uncompensated respiratory acidosis acidosis





a. Uncompensated metabolic alkalosis a. Uncompensated metabolic alkalosis

b. Uncompensated respiratory b. Uncompensated respiratory alkalosis alkalosis

c. Partially compensated respiratory c. Partially compensated respiratory alkalosis alkalosis

d. Partially compensated metabolic d. Partially compensated metabolic alkalosis alkalosis

Last caseLast case

pH 7.30, pCO2 59. HCO3- 28: pH 7.30, pCO2 59. HCO3- 28:

a. Uncompensated metabolic acidosis a. Uncompensated metabolic acidosis

b. Uncompensated respiratory b. Uncompensated respiratory acidosis acidosis



nephrology lecture acid - base balance presented by anas diab md us board certified in nephrology...

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