17. Intro to Acid-Base Disturbances

Question 1

what is the time course of acid-base compensatory mechanisms

Answer 1

cellular buffering process

resp compensation

renal base excretion

renal acid excretion

(renal takes longer to act than resp)

Question 2

what is the acid-base (davenport) nomogram diagram

& what does it show

Answer 2

the areas of acidosis & alkalosis

2 curves for resp bc kidneys take longer to respond - so graph shows acute and chronic resp changes

Question 3

if metabolic acidosis-

Answer 3

calculate anion gap

Question 4

if metabolic alkalosis -

Answer 4

have to decide if compensation if appropriate or if its a mixed disorder

decide if chloride resistant (urine_Cl>20) or responsive (urine_Cl<10)

Question 5

how do you calculate anion gap

Answer 5

Na - (Cl + HCO3)

= 11-12

high = metabolic acidosis

Question 6

what does it mean if you have a high anion gap

Answer 6

other solutes in plasma (alcohols, lactic acidosis, ketoacidosis)

metabolic acidosis

= GOLDMARK (glycol, oxoproline, L-lactate, D-lactate, methanol, aspirin, renal failure, ketoacidosis)

Question 7

how to calculate Osm gap

Answer 7

Question 8

what does it mean if Osm gap is > 10

Answer 8

other solute in plasma (alcohols, lactic acidosis, ketoacidosis)

Question 9

how to you calculate URINE anion gap

what is the result in metabolic acidosis

Answer 9

Na + K - Cl

= -20 to -50 in metabolic acidosis due to bicarb loss in diarrhea since excretion of unmeasured NH4+ increases

Question 10

what does the Osmolal gap equal if pt presents chronic severe metabolic acidosis or renal tubular acidosis

Answer 10

chronic severe metabolic acidosis - 200-300 (> 0 bc unmeasured osm particles)

renal tubular acidosis - < 75

Question 11

what are causes for acute resp acidosis

Answer 11

“CANS”

CNS depression (opiates)

Airway obstruction

Neuromuscular disorder (myasthenia gravis)

Severe pneumonia, embolism, edema

Question 12

what are reasons for chronic resp acidosis

Answer 12

COPD

anything chronic that leads to imparied ventilation

Question 13

what are symptoms of acute resp acidosis

Answer 13

headache, confusion, anxiety, drowsiness, stupor tremors, convulsions, possible coma

Question 14

what are the symptoms if slow developing respiratory acidosis

Answer 14

memory loss, sleep disturbances, excessive daytime sleepiness, personality changes

-gait probs, tremor, blunted deep tendon reflex, myoclonic jerks, asterixis (flapping wrist) & papilledma

Question 15

How much does [HCO3-] need to compensate for acute & chronic resp acidosis

Answer 15

for every 10 changes in PaCO2

acute - increase 1 mEq/L HCO3-

chronic- increase 3.5 mEq/L HCO3-

Question 16

if compensation of resp acidosis/alkalosis

isnt whats expected –

Answer 16

then you get mixed acid-base disorder

Question 17

what are the causes of resp alkalosis

Answer 17

CHAMPS

CNS disease - hyperventilation

Hypoxia

Anxiety

Mechanical ventilators

Progesterone

Salicylates (aspirin)/Sepsis

Question 18

what are the symptoms of acute & chronic resp alkalosis

Answer 18

acute - light headedness, confusion, peripheral/cicumoral paresthesia, cramps, syncope, tachypnea/hyperpnea - severe = carpopedal spasm bc low Ca

chronic - asymptomatic

Question 19

what is the expectation or HCO3- compensation for resp alkalosis

Answer 19

for every 10 PaCO2 decreased

acute - decrease HCO3 by 2 mEq/L

chronic - decrease HCO3 by 5 mEq/L

Question 20

what are the causes of High Anion Gap Metabolic Acidosis

(HAGMA)

Answer 20

GOLDMARK

Glycols

Oxoproline

Lactate

D-lactate

Methanol

Aspirin

Renal failure

Ketoacidosis

Question 21

what are the causes of Non-Anion Gap Metabolic Acidosis

Answer 21

HARDUPS {* = main causes)

Hyperalimentation

Acetazolamide

Renal tubular acidosis (1, 2, 4) *

Diarrhea *

Ureterosigmoid fistula

Posthypocapnia Pancreatic fistula

Spironolactone

Question 22

what are the symptoms of metabolic acidosis

how is it compensated

Answer 22

mild- asymptomatic

< 7.1 –> nausea, vomitting, malaise

(resp

compensation - long deep breaths at NORMAL rate)

Question 23

how do you calculate expected resp compensation for metabolic acidosis

Answer 23

P_aCO2 = (1.5*HCO3-) + 8 plus/minus 2

or

P_aCO2 =40 - (1.2 * (24-HCO3))

Question 24

what if resp compensation isnt whats expected

Answer 24

= mixed acid-base disorder

Question 25

what are the causes of metabolic alkalosis

Answer 25

CLEVER PD

Contraction

Licorice

Endo (conn, cushing, bartter)

Vomiting

Excess Alkali

Refeeding Alkolosis

Post-hypercapnia

Diuretics

Question 26

what are symptoms of metabolic aklalosis

Answer 26

mild - signs & symp of underlying disorder

severe - hypocalcemia -> HA, lethargy, neuromuscular excitability, sometimes delirium, tetany & seizures

–> lower threshold for angina symptoms, arrhythmias

Question 27

what is chloride-responsive metabolic alkalosis

Answer 27

causes = vomiting, diurtetics, nasogastic suction, diarrhea, cillous adenoma

urine Cl < 10

treat w/ normal saline

Question 28

what is chloride resistant metabolic alkalosis

Answer 28

causes = diuretic use/abuse or distal exchange site stimulation by aldo –> increase H & K excretion & increase Na reabs

urine Cl > 20 mEq/L

Question 29

how to you calculate the expected compensation for metabolic alkalosis

Answer 29

P_aCO2 = 40 + (0.7 * (HCO3 -24)

Question 30

RTA 1 =

Answer 30

impaired H secretion

> 5.5 urine pH

hypercalciuria, sickle cell anemia, kidney transplant

Question 31

RTA 2

Answer 31

impaired HCO3- reabs at PCT

decreased urine pH (fix with alkali therapy)

fancomia, multple myeloma, drugs

Question 32

RTA 4

Answer 32

lack of aldosterone/failure of kidneys to respond

HYPERKALEMIA

low urine pH

NSAIDS, spironolactone, diabetic nephropathy, chronic interstitial nephritis