Acid Base

Normal [H+] level and range in body serum

normal value: 40 nmol/L

Normal pH in body serum

range: 7.35-7.45

normal value: 7.4

Normal pCO2 in body serum

normal value: 40 mmHg

Normal [HCO3-] in body serum

range: 22-26 mEq/L

normal value: 24

normal range for PaCO2

35-45 mmHg

normal range for PaO2

80-100 mmHg

normal range for SaO2%

99%

what is a primary change?

an abnormality in serum [HCO3-] or pCO2/PaCO2 due to a primary issue in body function/metabolism/+ or - in fluids

--> something just aint workin right

what is a secondary change?

COMPENSATION in response to the primary issue

--> buffers, lungs, kidneys all compensate

What are simple Acid-Base disorders?

one primary disorder and one compensation (+/-)

--> pulmonary edema and kidney's compensating

What are Mixed Acid-Base disorders?

simultaneous occurrence of two + primary disorders

Acid-Base disorder assessment table

If a patient has a high pH and high [HCO3-], what would the diagnosis be?

Metabolic Alkalosis

If a patient has low pH and high PaCO2, what is the diagnosis?

respiratory acidosis

Clinical presentation of ACIDosis

Respiratory: hyperventilation (blowing off CO2)

Cardio: bradycardia, hypotension, decreased contraction

Neuro: confusion, coma

Gastro: loss of appetite, nausea, vomiting

**Know this for exam**

Anion Gap

If normal gap is different from normal, this is a clue that somethings going on

--> normal range = 8-12 mmol/L

--> if gap is higher = clue to metabolic acidosis

--> AG = Na+ - (Cl- + HCO3-)****

If the sodium level is 148, chloride level is 110, and HCO3- level is 16, what is the anion gap?

AG = 148 - (110 + 16)

AG = 22

high means metabolic acidosis

Some causes of Metabolic acidosis (Increased Anion Gap)

- Ketoacidosis (most likely)

- overdose

- kidney disease

- lactic acidosis

Some causes of Metabolic acidosis (Normal Anion Gap)

- Lower GI loss (diarrhea, decreased HCO3-)

- Renal losses

- Excessive chloride intake (too much 0.9% NS)

Primary change in RESPIRATORY Acidosis

increased PaCO2 due to impaired ventilation

--> caused by pulmonary issues (COPD), drug-induced

--> buffers and then kidneys compensate respectively

How do you treat respiratory acidosis caused by COPD?

Ventilation or Corticosteroids

--> ALWAYS patient specific!!!

How do you treat respiratory acidosis caused by opioids?

Ventilation and Naloxone

--> ALWAYS patient specific!!!

Describe ACUTE Respiratory Acidosis

- RAPID onset of increased CO2 (hypercapnia)

- decreased pH and elevated CO2

- usually uncompensated/partially compensated

- severe acidemia

Describe CHRONIC Respiratory Acidosis

- GRADUAL onset

- Moderately decreased pH, elevated CO2 and HCO3-

- Renal compensation

Why is the pH only moderately decreased in chronic respiratory acidosis?

due to compensation from the kidneys

Clinical presentation of Alkalosis

Neuro: confusion, coma, dizzy, seize

Muscular: cramps, weakness, tetany (involuntary spasms), and hyperreflexia (strong reflexes)

Cardio: arrhythmias (pH > 7.6)

What is the primary change in Metabolic Alkalosis?

Increased HCO3-

- net loss of H+, gain of bases, loss of chloride rich/bicarb poor fluids (vomiting)

--> buffers and then hypoventilation compensation occurs respectively

What are the two types of metabolic alkalosis?

Chloride responsive: urine [Cl-] < 10 mEq/L

--> responds well to NS IV

Chloride resistant: anything over 10

--> can NOT treat w/ NS IV

What treatments can be used for metabolic alkalosis?

- D/C offending agent

- NaCl IV: vomiting, contraction alkalosis

- Ketoconazole: Cushing's

Causes of chloride-responsive metabolic alkalosis

- vomiting

- contraction alkalosis

- loop/thiazide diuretics

- antacids (PPI's)

- TPN

Causes of chloride-resistant metabolic alkalosis

- cushing's

What is the primary change in Respiratory Alkalosis?

Decreased PaCO2 due to hypERventilation

- caused by both pulmonary and non-pulmonary

- buffers and then kidneys compensate respectively

What are the two treatments for Respiratory Alkalosis caused by asthma?

Bronchodilators and Corticosteroids

What is the treatment for Respiratory Alkalosis caused by high altitude?

Acetazolamide

What is the treatment for Respiratory Alkalosis from a psychogenic origini?

Anxiolytics

--> treating anxiety not the alkalosis

What is the treatment for Respiratory Alkalosis caused by pulmonary edema?

Diuresis

--> treating underlying edema not the alkalosis

what are the pulmonary causes of respiratory alkalosis?

- asthma

- pulmonary edema

- interstitial fibrosis

SOMETHING IS ACTUALLY WRONG W/ THE LUNGS!!!

what are the non-pulmonary causes of respiratory alkalosis?

- pregnancy

- brain lesions

- high altitude

- heart/liver disease

- psychogenic

Acid Base Assessment flow chart

use 7.4 as the normal pH for this chart

If the pH was lower than 7.4 and the PCO2 was high, what would be the diagnosis?

Respiratory Acidosis

If the pH was higher than 7.4 and the HCO3 was high, what would be the diagnosis?

Metabolic Alkalosis