Acid-base disorders

What does base excess: 7 mean?

7 too many bases

What does base excess: -4 mean?

need to add 4 bases

Increase in bicarbonate causes…

metabolic alkalosis

Decrease in buffer causes…

metabolic acidosis

Increase in CO2 causes…

Respiratory acidosis

Decrease in CO2 causes…

respiratory alkalosis

T/F: in metabolic disorders pH, HCO3, and pCO2 all move in the same direction

True

T/F: in respiratory disorders pH, HCO3, and pCO2 all move in the same direction

false

What order are the values written

pH/pCO2/O2/HCO3

What is the base value for pH

7.4

What is the base value for pCO2

40

What is the base value for HCO3

24

7.27/34/94/15

metabolic acidosis

7.34/50/92/26

respiratory acidosis

7.45/48/98/32

metabolic alkalosis

7.31/54/100/28

respiratory acidosis

7.57/18/97/16

respiratory alkalosis

What is the upper limit of the anion gap

16

How do you calculate the anion gap

Na - (Cl + HCO)

What does the anion gap mean

• no gap means the metabolic acidosis is caused by chloride

• gap means the metabolic acidosis is caused by ✨something else✨

Most common causes of anion gap metabolic acidosis acronym

MUDPILES

M in mudpiles

Methanol: more common in alcoholic population (drinking non drinkable alc)

manifests as visual disturbances, pancreatitis, CNS tox

U in mudpiles

Uremia: elevated BUN; GFR<50 ml/min; symptoms non specific

D in mudpiles

DKA: relative or absolute insulin deficiency; 3 pieces to diagnose, hyperglycemia (D), ketonuria (K), gap acidosis (A); the triggers of DKA are the 7 eyed monster

also insulin potassium and intubation 🤷‍♀

The seven eyed monster

• initial (new diagnosis)

• infection

• illicit drug use

• insulin (lack of, noncompliance)

• infarction

• incision (surgery)

• infant (pregnancy)

P in mudpiles

Propylene glycol: rare, when using a lot of lorazepam, diazepam, phenytoin, nitroglycerin, esmolol in a hospital setting

I in mudpiles

Isoniazid: inhibits vitamin B6 and GABA, rare, diagnosis by exclusion

Iron:oxidative phosphorylation uncoupler, free radical producer, GI hemorrhage

L in mudpiles

Lactic acidosis: extremely common, anaerobic metabolism of glucose, supply and demand mismatch (workout too hard after just starting)

E in mudpiles

Ethylene Glycol: antifreeze bad when people drink it, causes fluorescent urine

S in mudpiles

Salicylates: aspirin overdose, triggers respiration, hyperthermia, tinnitus, ketogenesis

Non gap metabolic acidosis cause

means theres too much chloride

non gap metabolic acidosis acronym

DURHAM

D in durham

Diarrhea: specifically ACUTE diarrhea; most common cause; lose Na, K, and bicarb but Cl stays behind

U in durham

Ureteral diversion: ureteroenterostomy; rare procedure; ureters are divided into a part of colon after bladder injury causes reabsorption of Cl in exchange for bicarb

R in durham

Renal tubular acidosis: 2nd most common cause; type 1 (distal) = hypokalemia associated with stones; type 2 (proximal) = bicarbonate loss; type 4 = hyperkalemia, associated with hypoaldosteronism

H in Durham

Hyperalimentation: usually from Cl containing solutions and feelings when given too much

A in durham

Acetazolamide: used to control metabolic alkalosis, carbonic anhydrase inhibitor

M in druham

Misc. conditions

Major causes of respiratory acidosis

respiratory depression, COPD

Major symptom of respiratory acidosis

confusion

What is alkalosis often accompanied by

hypokalemia and hypochloremia

What initiates alkalosis

initiated by either bicarbonate going in or hydrogen going out

What initiates a bicarbonate increase

bicarbonate infusion

magnesium citrate, lactate, acetate

What initiates acid loss

• vomiting

• nasogastric suction

• excess mineralocorticoid activity

• diuretic overuse

The initiation (phase 1) of alkalosis is common but usually short lived why?

kidneys are efficient, bicarb-excreting machines

How is alkalosis maintained (phase 2)

the kidneys ability to excrete bicarbonate becomes impaired

What are the two broad categories of metabolic alkalosis

• saline responsive (volume dependent)(dehydrated)

• saline resistant (volume independent) (hypokalemic)

A urine chloride of ______ usually saline responsive

<10 mEq/L

A urine chloride of ______ usually saline resistant

>20 mEq/L

Saline responsive alkalosis is maintained by ECFV depletion and chloride loss such as through…

• vomiting

• NG suction

• posthypercapnea

• diuretics

• chronic diarrhea

Chronic diarrhea causes

Saline responsive alkalosis

Acute diarrhea causes

non gap metabolic acidosis

What is at the root of most cases of saline resistant alkalosis

hypokalemia

How does severe hypokalemia cause alkalosis

• Potassium:intracellular to extracellular

• hydrogen extracellular to intracellular

How does magnesium depletion lead to hypokalemia

magnesium inhibits renal potassium wasting

does mineralocorticoid excess lead to potassium depletion?

yes

Where do mineralocorticoids come from

• adrenal glands and renin-angiotensin system

• licorice

Diseases associated with mineralocorticoid excess

• primary hyperaldosteronism aka cushings

Clinical effects of alkalosis

• decreased contractility

• arrhythmias

• decreased cerebral blood flow

• confusion

• obtundation

• hypoventilation

• poor oxygen unloading

• hypoxia