acid/base physio

The body maintains a tightly controlled blood pH in the normal range of

7.35–7.45.

three main pathophysiologic events that occur when blood pH deviates from the normal range

• proteins get denatured.

• enzymatic reactions get altered.

• cell membrane integrity gets altered.

abnormal pH in patients may present in this way

with mixed metabolic and respiratory disorders (e.g., both metabolic acidosis and respiratory acidosis), which makes treatment difficult and indicates they are typically very sick patients

major organs involved in the regulation of acid-base balance

lungs, kidneys, and bone

respiratory acids eliminated as CO2

volatile body acids

metabolic acids - eliminated by the kidney or metabolized by the liver

nonvolatile body acids

carbonic acid (H2CO3 ), which is formed from the hydration of carbon dioxide is this type of acid

volatile

carbon dioxide is eliminated by

pulmonary ventilation

acids are eliminated by the renal tubules in conjunction with the regulation of the concentration of bicarbonate (HCO3-)

nonvolatile

prime regulators of acid-base balance

lungs and kidneys

these organs regulate HCO3- by either reabsorbing or eliminating it in the urine.

kidneys

elimination occurs when HCO3- combines with phosphate and ammonia in this organ

kidneys

____ eliminate CO_2c formed when HCO₃^- combines with H+ in the serum to form ______, which dissociates into H₂O and CO₂

lungs, H₂CO₃ (carbonic acid)

most important plasma buffer systems

bicarbonate–carbonic acid and hemoglobin

lungs buffer system acts by

decreasing the amount of carbonic acid by exhaling CO2 and leaving water.

this buffer system acts rapidly

lungs

The kidneys buffer system acts by

reabsorbing bicarbonate or regenerating new bicarbonate from CO2 and water.

this buffer system acts slowly

kidneys

high H+ is called

acidemia

low H+ is called

alkalemia

more H+ = increased

acidity, decreased pH 

decreased HCO3- (metabolic) or increased pCO2 (respiratory) is an indicator for this state 

acidemic state

decreased acidity (low H+ and thus, high pH) will cause this process 

alkalosis

increased HCO₃^- (metabolic) or decreased pCO₂ (respirator) is an indicator of this state

alkalemic state

body's attempt to restore the pH by altering the component not primarily affected by the disorder. according to the Henderson-Hasselbach equation, the pCO2 and HCO3- must ultimately move in the same direction (both high or both low) to keep the pH near 7.4

acid-base compensation

in respiratory acidosis, the initial change is an ____ in pCO₂  and the compensatory change is an ____ in HCO₃^-

increase, increase

in respiratory alkalosis, the initial change is an ____ in pCO₂  and the compensatory change is an ____ in HCO₃^-

decrease, decrease

in metabolic acidosis, the initial change is an ____ in HCO₃^-   and the compensatory change is an ____ in pCO₂

decrease, decrease

in metabolic alkalosis, the initial change is an ____ in HCO₃^-   and the compensatory change is an ____ in pCO₂

increase, increase

no attempt made to correct the imbalance.

uncompensated

an attempt is being made, but the pH remains abnormal (outside 7.35–7.45).

partially compensated

the body is correcting the imbalance, and the pH is in the normal range (7.35–7.45), but pCO₂ and HCO_3^- remain abnormal. other ABG values may be abnormal

fully compensated

the ratio of HCO₃- to H₂CO₃

20:1

serum CO2 can be seen in a basic metabolic panel (chem 7) and is primarily representative of _____ as about 95% of the CO2 in the blood is in the form of ____

HCO3^-

HCO3^-

serum CO2 can be seen in this metabolic panel and is primarily representative of HCO3-, as about 95% of the CO2 in the blood is in the form of HCO3-

chem 7

calculated when a patient is in metabolic acidosis to determine its cause.

anion gap

normal anion gap (AG)

12 ± 4 (range 8-16) which represents unmeasured anions like albumin (the most abundant), lactate, phosphate, sulfate, and ketones 

the most abundant unmeasured protein. changes in a patient's_____ level (e.g., hypo____nemia from malnutrition or renal disease) will alter their "normal" AG

albumin

the patient's estimated normal AG can be calculated by multiplying their albumin level by

3

an AG over ___ is more clinically relevant for identifying an AG metabolic acidosis.

20

___ metabolic acidosis is more common than ____ metabolic acidosis

AG, non AG

anion gap formula

AG = Na⁺ - (Cl^- + HCO₃^-)

AG > 12-16 is caused by 

 the gain of an acid that increases unmeasured anions.

Normal AG (non-anion gap) is caused by

the loss of HCO₃^- or H+ retention by the kidneys (often Cl^- increases to compensate)

*Headache

*Lethargy

*Anorexia

*N/V

*Abdominal pain

*Dec ventricular contractility

*Dysrhythmias

*Kussmaul respirations

clinical manifestations of this

AG and non-AG Met Acidosis

kussmaul respirations

AG and non-AG met acidosis

MUD PILES. clinical manifestation for 

anion gap met acid

MUD PILES

*Methanol (antifreeze, solvents, cleaners)

**Uremia

**DKA and other ketoacidosis- ETOH, Starvation

*Propylene glycol (antifreeze, solvent in certain meds, i.e. benzos)

*Isoniazid (INH), Iron toxicity

**Lactic acidosis

*Ethylene glycol (antifreeze, solvents, cleaners)

*Salicylates (ASA)

uremia, DKA and other ketoacidosis, ETOH, starvation, lactic acidosis are more common causes for

anion gap metabolic acid

*Diarrhea

*Renal tubular acidosis

*Carbonic anhydrase inhibitors – Diamox (acetazolamide)

*Addison's Disease – Adrenal insufficiency

clinical manifestations for 

non-anion metabolic acid 

addison's disease (adrenal insufficiency) may be a cause for

non-anion gap metabolic acid

*Slow, shallow respirations

*Weakness

*Muscle cramps

*Hyperreflexia

*Paresthesias

*Numbness

*Dec Ca⁺

metabolic alkalosis clinical mainfestations

calcium binds to anionized albumin from the high pH causing a lot of symptoms in 

metabolic alkalosis 

slow, shallow respirtations are indicative of

metabolic alkalosis

causes: ?__?

*Prolonged vomiting

*Nasogastric (NG) suction

*Over diuresis

*Post-hypercapnia

*Cushing's disease – Increased cortisol production

*Exogenous corticosteroid use

*Hypomag.

*Licorice ingestion

metabolic alkalosis causes

NG suction, cushing’s disease, licorice ingestion

metabolic alkalosis causes

clinical manifestations

*HA

*Restlessness

*Blurred vision

*Apprehension

*Lethargy

*Tremors

*Convulsions

respiratory acidosis 

acute respiratory acidosis common causes

*COPD exacerbation

*Opioid OD (depressed resp center)

*Airway obstruction

chronic respiratory acidosis common causes

*COPD

*Neuromuscular d/o

*Chest wall deformities

clinical manifestations

*Dizziness

*Confusion

*Paresthesias

*Convulsions

*Carpopedal spasm

respiratory alkalosis

respiratory alkalosis (acute) is caused by

*Hyperventilation

*Asthma exacerbation (early)

*Hypoxemia

*Thyrotoxicosis

*Hysteria

chronic respiratory alkalosis is common causes 

pregnancy and mechanical ventilation